Vol. 79 Monday, 

No. 76 April 21, 2014 

Part II 

Department of Defense 

Department of the Army, Corps of Engineers 

33 CFR Part 328 

Environmental Protection Agency 

40 CFR Parts 110, 112, 116, et al. 

Definition of ‘‘Waters of the United States’’ Under the Clean Water Act; 

Proposed Rule 


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22188 Federal Register / Vol. 79, No. 76 / Monday, April 21, 2014 / Proposed Rules 

1 ‘‘Interstate waters’’ in this preamble refers to all 

interstate waters including interstate wetlands. 

DEPARTMENT OF DEFENSE 

Department of the Army, Corps of 

Engineers 

33 CFR Part 328 

ENVIRONMENTAL PROTECTION 

AGENCY 

40 CFR Parts 110, 112, 116, 117, 122, 

230, 232, 300, 302, and 401 

[EPA–HQ–OW- 2011–0880; FRL–9901–47– 

OW] 

RIN 2040–AF30 

Definition of ‘‘Waters of the United 

States’’ Under the Clean Water Act 

AGENCY: U.S. Army Corps of Engineers, 

Department of the Army, Department of 

Defense; and Environmental Protection 

Agency (EPA). 

ACTION: Proposed rule. 

SUMMARY: The Environmental Protection 

Agency (EPA) and the U.S. Army Corps 

of Engineers (Corps) are publishing for 

public comment a proposed rule 

defining the scope of waters protected 

under the Clean Water Act (CWA), in 

light of the U.S. Supreme Court cases in 

U.S. v. Riverside Bayview, Rapanos v. 

United States, and Solid Waste Agency 

of Northern Cook County v. U.S. Army 

Corps of Engineers (SWANCC), and 

Rapanos v. United States (Rapanos). 

This proposal would enhance protection 

for the nation’s public health and 

aquatic resources, and increase CWA 

program predictability and consistency 

by increasing clarity as to the scope of 

‘‘waters of the United States’’ protected 

under the Act. 

DATES: Submit comments on or before 

July 21, 2014. 

ADDRESSES: Submit your comments, 

identified by Docket ID No. EPA–HQ– 

OW–2011–0880 by one of the following 

methods: 

• Federal eRulemaking Portal: http:// 

www.regulations.gov. Follow the 

instructions for submitting comments. 

• Email: ow-docket@epa.gov. Include 

EPA–HQ–OW–2011–0880 in the subject 

line of the message. 

• Mail: Send the original and three 

copies of your comments to: Water 

Docket, Environmental Protection 

Agency, Mail Code 2822T, 1200 

Pennsylvania Avenue NW., Washington, 

DC 20460, Attention: Docket ID No. 

EPA–HQ–OW–2011–0880. 

• Hand Delivery/Courier: Deliver 

your comments to EPA Docket Center, 

EPA West, Room 3334, 1301 

Constitution Avenue NW., Washington, 

DC 20460, Attention Docket ID No. 

EPA–HQ–OW–2011–0880. Such 

deliveries are accepted only during the 

Docket’s normal hours of operation, 

which are 8:30 a.m. to 4:30 p.m., 

Monday through Friday, excluding legal 

holidays. Special arrangements should 

be made for deliveries of boxed 

information. The telephone number for 

the Water Docket is 202–566–2426. 

Instructions: Direct your comments to 

Docket ID No. EPA–HQ–OW–2011– 

0880. EPA’s policy is that all comments 

received will be included in the public 

docket without change and may be 

made available on-line at http://

www.regulations.gov, including any 

personal information provided, unless 

the comment includes information 

claimed to be Confidential Business 

Information (CBI) or other information 

whose disclosure is restricted by statute. 

Do not submit information that you 

consider to be CBI, or otherwise 

protected, through http://

www.regulations.gov or email. The 

http://www.regulations.gov Web site is 

an ‘‘anonymous access’’ system, which 

means EPA will not know your identity 

or contact information unless you 

provide it in the body of your comment. 

If you send an email directly to EPA 

without going through http://

www.regulations.gov, your email 

address will be automatically captured 

and included as part of the comment 

that is placed in the public docket and 

made available on the Internet. If you 

submit an electronic comment, EPA 

recommends that you include your 

name and other contact information in 

the body of your comment and with any 

disk or CD–ROM you submit. If EPA 

cannot read your comment due to 

technical difficulties and cannot contact 

you for clarification, EPA might not be 

able to consider your comment. Avoid 

the use of special characters and any 

form of encryption, and ensure that 

electronic files are free of any defects or 

viruses. For additional information 

about EPA’s public docket, visit the EPA 

Docket Center homepage at http://

www.epa.gov/epahome/dockets.htm. 

Docket: All documents in the docket 

are listed in the http://

www.regulations.gov index. Some 

information, however, is not publicly 

available, e.g., CBI or other information 

whose disclosure is restricted by statute. 

Certain other material, such as 

copyrighted material, is publicly 

available only in hard copy. Publicly 

available docket materials are available 

electronically at http://

www.regulations.gov or in hard copy at 

the Water Docket, EPA Docket Center, 

EPA West, Room 3334, 1301 

Constitution Avenue NW., Washington, 

DC. The Public Reading Room is open 

from 8:30 a.m. to 4:30 p.m., Monday 

through Friday, excluding legal 

holidays. The telephone number for the 

Public Reading Room is 202–566–1744, 

and the telephone number for the Water 

Docket is 202–566–2426. 

FOR FURTHER INFORMATION CONTACT: Ms. 

Donna Downing, Office of Water (4502– 

T), Environmental Protection Agency, 

1200 Pennsylvania Avenue NW., 

Washington, DC 20460; telephone 

number 202–566–2428; email address: 

CWAwaters@epa.gov. Ms. Stacey Jensen, 

Regulatory Community of Practice 

(CECW–CO–R), U.S. Army Corps of 

Engineers, 441 G Street NW., 

Washington, DC 20314; telephone 

number 202–761–5856; email address: 

USACE_CWA_Rule@usace.army.mil. 

SUPPLEMENTARY INFORMATION: The 

SWANCC and Rapanos decisions 

resulted in the agencies evaluating the 

jurisdiction of waters on a case-specific 

basis far more frequently than is best for 

clear and efficient implementation of 

the CWA. This approach results in 

confusion and uncertainty to the 

regulated public and results in 

significant resources being allocated to 

these determinations by Federal and 

State regulators. The agencies are 

proposing this rule to fully carry out 

their responsibilities under the Clean 

Water Act. The agencies are providing 

clarity to regulated entities as to 

whether individual water bodies are 

jurisdictional and discharges are subject 

to permitting, and whether individual 

water bodies are not jurisdictional and 

discharges are not subject to permitting. 

Developing a final rule to provide the 

intended level of certainty and 

predictability, and minimizing the 

number of case-specific determinations, 

will require significant public 

involvement and engagement. Such 

involvement and engagement will allow 

the agencies to make categorical 

determinations of jurisdiction, in a 

manner that is consistent with the 

scientific body of information before the 

agencies—particularly on the category 

of waters known as ‘‘other waters.’’ 

The agencies propose to define 

‘‘waters of the United States’’ in section 

(a) of the proposed rule for all sections 

of the CWA to mean: Traditional 

navigable waters; interstate waters, 

including interstate wetlands; the 

territorial seas; impoundments of 

traditional navigable waters, interstate 

waters, including interstate wetlands, 

the territorial seas, and tributaries, as 

defined, of such waters; tributaries, as 

defined, of traditional navigable waters, 

interstate waters,1 or the territorial seas; 


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2The term ‘‘waters of the United States’’ does not 

include prior converted cropland, which is 

currently defined by the U.S. Department of 

Agriculture (USDA) for purposes of the Agriculture 

Act of 2014 at 7 CFR 122.2. EPA and the Corps use 

the USDA definition of prior converted cropland for 

purposes of determining jurisdiction under the 

CWA. 

and adjacent waters, including adjacent 

wetlands. Waters in these categories 

would be jurisdictional ‘‘waters of the 

United States’’ by rule—no additional 

analysis would be required. The 

agencies emphasize that the categorical 

finding of jurisdiction for tributaries and 

adjacent waters was not based on the 

mere connection of a water body to 

downstream waters, but rather a 

determination that the nexus, alone or 

in combination with similarly situated 

waters in the region, is significant based 

on data, science, the CWA, and caselaw. 

In addition, the agencies propose that 

‘‘other waters’’ (those not fitting in any 

of the above categories) could be 

determined to be ‘‘waters of the United 

States’’ through a case-specific showing 

that, either alone or in combination with 

similarly situated ‘‘other waters’’ in the 

region, they have a ‘‘significant nexus’’ 

to a traditional navigable water, 

interstate water, or the territorial seas. 

The rule would also offer a definition of 

significant nexus and explain how 

similarly situated ‘‘other waters’’ in the 

region should be identified. 

The agencies acknowledge that there 

may be more than one way to determine 

which waters are jurisdictional as 

‘‘other waters.’’ To best meet their goals 

and responsibilities, the agencies 

request comment on alternate 

approaches to determining whether 

‘‘other waters’’ are similarly situated 

and have a ‘‘significant nexus’’ to a 

traditional navigable water, interstate 

water, or the territorial seas. In the 

discussion of ‘‘other waters’’ later in the 

preamble, the agencies seek comment 

on these other approaches and whether 

they could better meet the goals of 

greater predictability and consistency 

through increased clarity, while 

simultaneously fulfilling the agencies’ 

responsibility to the CWA’s objectives 

and policies to protect water quality, 

public health, and the environment. 

Commenters will specifically be asked 

to comment on whether and how these 

alternate approaches may be more 

consistent with the goal of clarity, and 

the CWA, the best available science, and 

the caselaw. 

In particular, the agencies are 

interested in comments, scientific and 

technical data, caselaw, and other 

information that would further clarify 

which ‘‘other waters’’ should be 

considered similarly situated for 

purposes of a case-specific significant 

nexus determination. The agencies seek 

comment on a number of alternative 

approaches. These alternatives include 

potentially determining waters in 

identified ecological regions 

(ecoregions) or hydrologic-landscape 

regions are similarly situated for 

purposes of evaluating a significant 

nexus, as well as the basis for 

determining which ecoregions or 

hydrologic-landscape regions should be 

so identified. The agencies also solicit 

comment on whether the legal, 

technical and scientific record would 

support determining limited specific 

subcategories of waters are similarly 

situated, or as having a significant nexus 

sufficient to establish jurisdiction. 

Just as the agencies are seeking 

comment on a variety of approaches, or 

combination of approaches, as to which 

waters are jurisdictional, the agencies 

also request comment on determining 

which waters should be determined 

non-jurisdictional. The agencies seek 

comment on how inconclusiveness of 

the science relates to the use of casespecific determinations. As the science 

develops, the agencies could determine 

that additional categories of ‘‘other 

waters’’ are similarly situated and have 

a significant nexus and are 

jurisdictional by rule, or that as a class 

they do not have such a significant 

nexus and might not be jurisdictional. 

The agencies pose the questions 

because of the strong intent to provide 

as much certainty to the regulated 

public and the regulators as to which 

waters are and are not subject to CWA 

jurisdiction. These comments on 

alternate approaches will inform the 

agencies in addition to the comments on 

the case-specific determination 

proposed in the rule. 

The agencies’ decision on how best to 

address jurisdiction over ‘‘other waters’’ 

in the final rule will be informed by the 

final version of the EPA’s Office of 

Research and Development synthesis of 

published peer-reviewed scientific 

literature discussing the nature of 

connectivity and effects of streams and 

wetlands on downstream waters (U.S. 

Environmental Protection Agency, 

Connectivity of Streams and Wetlands 

to Downstream Waters: A Review and 

Synthesis of the Scientific Evidence, 

(Washington, DC: U.S. Environmental 

Protection Agency, 2013)) (‘‘Report’’) 

and other available scientific 

information. 

The agencies also propose to exclude 

specified waters from the definition of 

‘‘waters of the United States’’ in section 

(b) of the proposed rule. The agencies 

propose no change to the exclusion for 

waste treatment systems designed 

consistent with the requirements of the 

CWA, no change to the exclusion for 

prior converted cropland,2 and no 

change to the regulatory status of water 

transfers. The agencies propose, for the 

first time, to exclude by regulation 

certain waters and features over which 

the agencies have as a policy matter 

generally not asserted CWA jurisdiction. 

Codifying these longstanding practices 

supports the agencies’ goals of 

providing greater clarity, certainty, and 

predictability for the regulated public 

and the regulators. Waters and features 

that are determined to be excluded 

under section (b) of the proposed rule 

will not be jurisdictional under any of 

the categories in the proposed rule 

under section (a). There is no recapture 

provision for these excluded waters in 

the proposal. 

In light of the Supreme Court 

decisions in SWANCC and Rapanos, the 

scope of regulatory jurisdiction in this 

proposed rule is narrower than that 

under the existing regulations. See 40 

CFR 122.2 (defining ‘‘waters of the 

United States’’). 

The rule does not affect longstanding 

permitting exemptions in the CWA for 

farming, silviculture, ranching and other 

specified activities. Where waters would 

be determined jurisdictional under the 

proposed rule, applicable exemptions in 

the CWA would continue to preclude 

application of CWA permitting 

requirements. 

Finally, the agencies retain the 

existing regulatory definitions for the 

terms ‘‘adjacent’’ and ‘‘wetlands.’’ The 

agencies propose for the first time to 

define the terms ‘‘neighboring,’’ 

‘‘riparian area,’’ ‘‘floodplain,’’ 

‘‘tributary,’’ and ‘‘significant nexus.’’ 

This proposal does not affect 

Congressional policy to preserve the 

primary responsibilities and rights of 

states to prevent, reduce, and eliminate 

pollution, to plan the development and 

use of land and water resources, and to 

consult with the Administrator with 

respect to the exercise of the 

Administrator’s authority under the 

CWA. CWA section 101(b). 

This proposal also does not affect 

Congressional policy not to supersede, 

abrogate or otherwise impair the 

authority of each State to allocate 

quantities of water within its 

jurisdiction and neither does it affect 

the policy of Congress that nothing in 

the CWA shall be construed to 

supersede or abrogate rights to 

quantities of water which have been 

established by any state. CWA section 

101(g). 

This proposal requests public 

comment on issues associated with the 


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22190 Federal Register / Vol. 79, No. 76 / Monday, April 21, 2014 / Proposed Rules 

agencies’ proposed regulatory definition 

of ‘‘waters of the United States.’’ 

Because the agencies do not address the 

exclusions from the definition of 

‘‘waters of the United States’’ for waste 

treatment systems and prior converted 

cropland or the existing definition of 

‘‘wetlands’’ in this proposed rule the 

agencies do not seek comment on these 

existing regulatory provisions. This 

notice also solicits information and data 

from the general public, the scientific 

community, and tribal, state and local 

resource agencies on the aquatic 

resource, implementation, and 

economic implications of a definition of 

‘‘waters of the United States’’ as 

described in the proposal. The goal of 

the agencies is to ensure the regulatory 

definition is consistent with the CWA, 

as interpreted by the Supreme Court, 

and as supported by science, and to 

provide maximum clarity to the public, 

as the agencies work to fulfill the CWA’s 

objectives and policy to protect water 

quality, public health, and the 

environment. 

Table of Contents 

I. General Information 

A. How can I get copies of this document and 

related information? 

B. Under what legal authority is this 

proposed rule issued? 

II. Background 

A. Executive Summary 

B. The Clean Water Act and Regulatory 

Definition of Waters of the United States 

C. Background on Scientific Review and 

Significant Nexus Analysis 

1. Scientific Synthesis 

2. Summary of Significant Nexus 

Conclusions 

III. Proposed Definition of Waters of the 

United States 

A. Summary of Proposed Rule 

B. Traditional Navigable Waters 

C. Interstate Waters 

D. Territorial Seas 

E. Impoundments 

F. Tributaries 

G. Adjacent Waters 

H. Other Waters 

I. Waters That Are Not Waters of the United 

States 

IV. Related Acts of Congress, Executive 

Orders, and Agency Initiatives 

A. Executive Order 12866: Regulatory 

Planning and Review 

B. Paperwork Reduction Act 

C. Regulatory Flexibility Act 

D. Unfunded Mandates Reform Act 

E. Executive Order 13132: Federalism 

F. Executive Order 13175: Consultation and 

Coordination With Indian Tribal 

Governments 

G. Executive Order 13045: Protection of 

Children From Environmental Health 

and Safety Risks 

H. Executive Order 13211: Actions 

Concerning Regulations That 

Significantly Affect Energy Supply, 

Distribution, or Use 

I. National Technology Transfer and 

Advancement Act 

J. Executive Order 12898: Federal Actions To 

Address Environmental Justice in 

Minority Populations and Low-Income 

Populations 

K. Environmental Documentation 

Appendix A. Scientific Evidence 

Appendix B. Legal Analysis 

I. General Information 

A. How can I get copies of this 

document and related information? 

1. Docket. EPA and the Corps of 

Engineers have established an official 

public docket for this action under 

Docket Id. No. EPA–HQ–OW–2011– 

0880. The official public docket consists 

of the document specifically referenced 

in this action, any public comments 

received, and other information related 

to this action. Although a part of the 

official docket, the public docket does 

not include Confidential Business 

Information (CBI) or other information 

whose disclosure is restricted by statute. 

The official public docket is the 

collection of materials that is available 

for public viewing at the OW Docket, 

EPA West, Room 3334, 1301 

Constitution Ave. NW., Washington, DC 

20004. This Docket Facility is open from 

8:30 a.m. to 4:30 p.m., Monday through 

Friday, excluding legal holidays. The 

OW Docket telephone number is 202– 

566–2426. A reasonable fee will be 

charged for copies. 

2. Electronic Access. You may access 

this Federal Register document 

electronically through the EPA Internet 

under the ‘‘Federal Register’’ listings at 

http://www.regulations.gov. An 

electronic version of the public docket 

is available through EPA’s electronic 

public docket and comment system, 

EPA Dockets. You may use EPA Dockets 

at http://www.regulations.gov to view 

public comments, access the index 

listing of the contents of the official 

public docket, and to access those 

documents in the public docket that are 

available electronically. For additional 

information about EPA’s public docket, 

visit the EPA Docket Center homepage 

at http://www.epa.gov/epahome/

dockets.htm. Although not all docket 

materials may be available 

electronically, you may still access any 

of the publicly available docket 

materials through the Docket Facility 

identified earlier. 

B. Under what legal authority is this 

proposed rule issued? 

The authority for this proposed rule is 

the Federal Water Pollution Control Act, 

33 U.S.C. 1251, et seq. 

II. Background 

A. Executive Summary 

The U.S. Environmental Protection 

Agency (EPA) and the U.S. Army Corps 

of Engineers (Corps) publish for public 

comment a proposed rule defining the 

scope of waters protected under the 

Clean Water Act (CWA), in light of the 

U.S. Supreme Court cases in U.S. v. 

Riverside Bayview Homes, Solid Waste 

Agency of Northern Cook County v. U.S. 

Army Corps of Engineers (SWANCC), 

and Rapanos v. United States 

(Rapanos). The purposes of the 

proposed rule are to ensure protection 

of our nation’s aquatic resources and 

make the process of identifying ‘‘waters 

of the United States’’ less complicated 

and more efficient. The rule achieves 

these goals by increasing CWA program 

transparency, predictability, and 

consistency. This rule will result in 

more effective and efficient CWA permit 

evaluations with increased certainty and 

less litigation. This rule provides 

increased clarity regarding the CWA 

regulatory definition of ‘‘waters of the 

United States’’ and associated 

definitions and concepts. 

EPA’s Office of Research and 

Development prepared a draft peerreviewed synthesis of published peerreviewed scientific literature discussing 

the nature of connectivity and effects of 

streams and wetlands on downstream 

waters (U.S. Environmental Protection 

Agency, Connectivity of Streams and 

Wetlands to Downstream Waters: A 

Review and Synthesis of the Scientific 

Evidence, (Washington, DC: U.S. 

Environmental Protection Agency, 

2013)) (‘‘Report’’). The Report is under 

review by EPA’s Science Advisory 

Board, and the rule will not be finalized 

until that review and the final Report 

are complete. This proposal is also 

supported by a body of peer-reviewed 

scientific literature on the connectivity 

of tributaries, wetlands, adjacent open 

waters, and other open waters to 

downstream waters and the important 

effects of these connections on the 

chemical, physical, and biological 

integrity of those downstream waters. 

Appendix A of this preamble 

summarizes currently available 

scientific literature and the Report that 

are part of the administrative record for 

this proposal and explains how this 

scientific information supports the 

proposed rule. Additional data and 

information likely will become available 

during the rulemaking process, 

including that provided during the 

public comment process, and by 

additional research, studies, and 

investigations that take place before the 

rulemaking process is concluded. The 


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3The agencies use the term ‘‘water’’ and ‘‘waters’’ 

in the proposed rule in categorical reference to 

rivers, streams, ditches, wetlands, ponds, lakes, 

playas, and other types of natural or man-made 

aquatic systems. The agencies use the terms 

‘‘waters’’ and ‘‘water bodies’’ interchangeably in 

this preamble. The terms do not refer solely to the 

water contained in these aquatic systems, but to the 

system as a whole including associated chemical, 

physical, and biological features. 

4While section 311 uses the phrase ‘‘navigable 

waters of the United States,’’ EPA has interpreted 

it to have the same breadth as the phrase ‘‘navigable 

waters’’ used elsewhere in section 311, and in other 

sections of the CWA. See United States v. Texas 

Pipe Line Co., 611 F.2d 345, 347 (10th Cir. 1979); 

United States v. Ashland Oil & Transp. Co., 504 

F.2d 1317, 1324–25 (6th Cir. 1974). In 2002, EPA 

revised its regulatory definition of ‘‘waters of the 

United States’’ in 40 CFR part 112 to ensure that 

the actual language of the rule was consistent with 

the regulatory language of other CWA programs. Oil 

Pollution & Response; Non-Transportation-Related 

Onshore & Offshore Facilities, 67 FR 47042, July 17, 

2002. A district court vacated the rule for failure to 

comply with the Administrative Procedure Act, and 

reinstated the prior regulatory language. American 

Petroleum Ins. v. Johnson, 541 F.Supp. 2d 165 (D. 

DC 2008). However, EPA interprets ‘‘navigable 

waters of the United States’’ in CWA section 311(b), 

in the pre-2002 regulations, and in the 2002 rule to 

have the same meaning as ‘‘navigable waters’’ in 

CWA section 502(7). 

5For example, the CWA section 402 (33 U.S.C. 

§ 1342) program regulates discharges of pollutants 

from ‘‘point sources’’ to ‘‘waters of the United 

States,’’ whether these pollutants reach 

jurisdictional waters directly or indirectly. The 

plurality opinion in Rapanos noted that ‘‘there is 

no reason to suppose that our construction today 

significantly affects the enforcement of § 1342. . . . 

The Act does not forbid the ‘addition of any 

pollutant directly to navigable waters from any 

point source,’ but rather the ‘addition of any 

pollutant to navigable waters.’ ’’ 547 U.S. at 743. 

Clean Water Act section 311(b)(1) provides: ‘‘[I]t is 

the policy of the United States that there should be 

no discharges of oil or hazardous substances into 

or upon the navigable waters of the United States 

[or] adjoining shorelines . . . or which may affect 

natural resources belonging to, appertaining to, or 

under the exclusive management authority of the 

United States.’’ (Emphasis added.) ‘‘Discharge’’ is 

broadly defined in CWA section 311(a)(2) to 

include ‘‘any spilling, leaking, pumping, pouring, 

emitting, emptying or dumping,’’ with certain 

enumerated exceptions, and is not limited to point 

source discharges. 

agencies are specifically requesting 

information that would inform the 

decision on how best to address ‘‘other 

waters.’’ At the conclusion of the 

rulemaking process, the agencies will 

review the entirety of the completed 

administrative record and determine at 

that time what, if any, adjustments are 

appropriate for the final rule. 

‘‘Waters of the United States,’’ which 

include wetlands, rivers, streams, lakes, 

ponds and the territorial seas, provide 

many functions and services critical for 

our nation’s economic and 

environmental health.3 In addition to 

providing habitat, rivers, lakes, ponds 

and wetlands cleanse our drinking 

water, ameliorate storm surges, provide 

invaluable storage capacity for some 

flood waters, and enhance our quality of 

life by providing myriad recreational 

opportunities, as well as important 

water supply and power generation 

benefits. A desire to protect these vital 

resources led Congress to pass the CWA 

in 1972 in order to restore and maintain 

the chemical, physical, and biological 

integrity of our nation’s waters while 

recognizing, preserving, and protecting 

the primary responsibilities and rights 

of states to prevent, reduce, and 

eliminate pollution within their borders. 

Decades of experience implementing the 

CWA’s programs and existing science 

provide strong support for the 

regulatory and policy underpinnings of 

the proposed rule. The proposed rule 

was developed with an enhanced 

understanding of the importance of all 

aspects of tributary, wetland, and lake 

and pond systems and the ecological 

functions and services they provide. 

The proposed rule will reduce 

documentation requirements and the 

time currently required for making 

jurisdictional determinations. It will 

provide needed clarity for regulators, 

stakeholders and the regulated public 

for identifying waters as ‘‘waters of the 

United States,’’ and reduce time and 

resource demanding case-specific 

analyses prior to determining 

jurisdiction and any need for permit or 

enforcement actions. 

The modern Clean Water Act was 

established by the Federal Water 

Pollution Control Act Amendments of 

1972, which was substantially amended 

in 1977 and 1987. (The 1972 

amendments were to the Federal Water 

Pollution Control Act originally enacted 

in 1948.) As stated in section 101(a), the 

objective of the CWA is to restore and 

maintain the chemical, physical, and 

biological integrity of the Nation’s 

waters. Prior to the CWA, the Rivers and 

Harbors Appropriations Act of 1899 

protected navigation and protected 

some waters from discharges of 

pollution. 

The 1899 Act continues in force and 

applies primarily to the ‘‘navigable 

waters of the United States.’’ The 1948 

Federal Water Pollution Control Act 

called for programs eliminating or 

reducing the pollution of interstate 

waters and tributaries thereof, and 

improving the sanitary condition of 

surface and underground waters. The 

jurisdictional scope of the CWA is 

‘‘navigable waters,’’ defined in section 

502(7) of the statute as ‘‘waters of the 

United States, including the territorial 

seas.’’ Both the legislative history and 

the caselaw confirm that ‘‘waters of the 

United States’’ in the CWA are not 

limited to the traditional navigable 

waters. It is the CWA definition that is 

the subject of this proposed rule. 

The term ‘‘navigable waters’’ is used 

in a number of provisions of the CWA, 

including the section 402 National 

Pollutant Discharge Elimination System 

(NPDES) permit program, the section 

404 permit program, the section 311 oil 

spill prevention and response program,4

the water quality standards and total 

maximum daily load programs under 

section 303, and the section 401 state 

water quality certification process. 

However, while there is only one CWA 

definition of ‘‘waters of the United 

States,’’ there may be other statutory 

factors that define the reach of a 

particular CWA program or provision.5

The CWA leaves it to EPA and the 

Corps to define the term ‘‘waters of the 

United States.’’ Existing regulations (last 

codified in 1986) define ‘‘waters of the 

United States’’ as traditional navigable 

waters, interstate waters, all other 

waters that could affect interstate or 

foreign commerce, impoundments of 

waters of the United States, tributaries, 

the territorial seas, and adjacent 

wetlands. 33 CFR 328.3; 40 CFR 122.2. 

The U.S. Supreme Court addressed 

the scope of ‘‘waters of the United 

States’’ protected by the CWA in United 

States v. Riverside Bayview Homes, 474 

U.S. 121 (1985), which involved 

wetlands adjacent to a traditional 

navigable water in Michigan. In a 

unanimous opinion, the Court deferred 

to the Corps’ judgment that adjacent 

wetlands are ‘‘inseparably bound up’’ 

with the waters to which they are 

adjacent, and upheld the inclusion of 

adjacent wetlands in the regulatory 

definition of ‘‘waters of the United 

States.’’ The Court observed that the 

broad objective of the CWA to restore 

the integrity of the nation’s waters 

‘‘incorporated a broad, systemic view of 

the goal of maintaining and improving 

water quality. . . . Protection of aquatic 

ecosystems, Congress recognized, 

demanded broad federal authority to 

control pollution, for ‘[w]ater moves in 

hydrologic cycles and it is essential that 

discharge of pollutants be controlled at 

the source.’ In keeping with these views, 

Congress chose to define the waters 

covered by the Act broadly.’’ Id. at 133 

(citing Senate Report 92–414). 

The issue of CWA regulatory 

jurisdiction over ‘‘waters of the United 

States’’ was addressed again by the 

Supreme Court in Solid Waste Agency 

of Northern Cook County v. U.S. Army 

Corps of Engineers, 531 U.S. 159 (2001). 

In SWANCC, the Court (in a 5–4 

opinion) held that the use of ‘‘isolated’’ 

nonnavigable intrastate ponds by 

migratory birds was not by itself a 

sufficient basis for the exercise of 

Federal regulatory authority under the 


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CWA. The Court noted that in the 

Riverside case it had ‘‘found that 

Congress’ concern for the protection of 

water quality and aquatic ecosystems 

indicated its intent to regulate wetlands 

‘inseparably bound up with the 

‘‘waters’’ of the United States’ ’’ and that 

‘‘[i]t was the significant nexus between 

the wetlands and ‘navigable waters’ that 

informed our reading of the CWA’’ in 

that case. Id. at 167. 

Five years after SWANCC, the Court 

again addressed the CWA term ‘‘waters 

of the United States’’ in Rapanos v. 

United States, 547 U.S. 715 (2006). 

Rapanos involved two consolidated 

cases in which the CWA had been 

applied to wetlands adjacent to 

nonnavigable tributaries of traditional 

navigable waters. All Members of the 

Court agreed that the term ‘‘waters of 

the United States’’ encompasses some 

waters that are not navigable in the 

traditional sense. A four-Justice 

plurality in Rapanos interpreted the 

term ‘‘waters of the United States’’ as 

covering ‘‘relatively permanent, 

standing or continuously flowing bodies 

of water. . .’’ id. at 739, that are 

connected to traditional navigable 

waters, id. at 742, as well as wetlands 

with a continuous surface connection to 

such relatively permanent water bodies, 

id. The Rapanos plurality noted that its 

reference to ‘‘relatively permanent’’ 

waters did ‘‘not necessarily exclude 

streams, rivers, or lakes that might dry 

up in extraordinary circumstances, such 

as drought,’’ or ‘‘seasonal rivers, which 

contain continuous flow during some 

months of the year but no flow during 

dry months. . . .’’ Id. at 732 n.5 

(emphasis in original). 

Justice Kennedy’s concurring opinion 

took a different approach than the 

plurality’s. Justice Kennedy concluded 

that the term ‘‘waters of the United 

States’’ encompasses wetlands that 

‘‘possess a ‘significant nexus’ to waters 

that are or were navigable in fact or that 

could reasonably be so made.’’ Id. at 759 

(Kennedy, J., concurring in the 

judgment) (quoting SWANCC, 531 U.S. 

at 167). He stated that wetlands possess 

the requisite significant nexus if the 

wetlands, ‘‘either alone or in 

combination with similarly situated 

[wet]lands in the region, significantly 

affect the chemical, physical, and 

biological integrity of other covered 

waters more readily understood as 

‘navigable.’ ’’ 547 U.S. at 780. Kennedy’s 

opinion notes that such a relationship 

with navigable waters must be more 

than ‘‘speculative or insubstantial.’’ Id. 

Because Justice Kennedy identified 

‘‘significant nexus’’ as the touchstone 

for CWA jurisdiction, the agencies 

determined that it is reasonable and 

appropriate to apply the ‘‘significant 

nexus’’ standard for CWA jurisdiction 

that Justice Kennedy’s opinion applied 

to adjacent wetlands to other categories 

of water bodies as well (such as to 

tributaries of traditional navigable 

waters or interstate waters, and to 

‘‘other waters’’) to determine whether 

they are subject to CWA jurisdiction, 

either by rule or on a case-specific basis. 

The four dissenting Justices in 

Rapanos would have affirmed the court 

of appeals’ application of the pertinent 

regulatory provisions, concluding that 

the term ‘‘waters of the United States’’ 

encompasses, inter alia, all tributaries 

and wetlands that satisfy either the 

plurality’s standard or that of Justice 

Kennedy. Id. at 810 & n.14 (Stevens, J., 

dissenting). Neither the plurality nor the 

Kennedy opinion invalidated any of the 

regulatory provisions defining ‘‘waters 

of the United States.’’ 

The proposed rule would revise the 

existing definition of ‘‘waters of the 

United States’’ consistent with the 

science and the above Supreme Court 

cases. The proposed rule retains much 

of the structure of the agencies’ 

longstanding definition of ‘‘waters of the 

United States,’’ and many of the existing 

provisions of that definition where 

revisions are not required in light of 

Supreme Court decisions or other bases 

for revision. As a result of the Supreme 

Court decisions in SWANCC and 

Rapanos, the scope of regulatory 

jurisdiction of the CWA in this 

proposed rule is narrower than that 

under the existing regulations. 

The most substantial change is the 

proposed deletion of the existing 

regulatory provision that defines 

‘‘waters of the ‘‘United States’’ as all 

other waters such as intrastate lakes, 

rivers, streams (including intermittent 

streams), mudflats, sandflats, wetlands, 

sloughs, prairie potholes, wet meadows, 

playa lakes, or natural ponds, the use, 

degradation or destruction of which 

could affect interstate or foreign 

commerce including any such waters: 

Which are or could be used by interstate 

or foreign travelers for recreational or 

other purposes; from which fish or 

shellfish are or could be taken and sold 

in interstate or foreign commerce; or 

which are used or could be used for 

industrial purposes by industries in 

interstate commerce. 33 CFR 328.3(a)(3); 

40 CFR 122.2. Under the proposed rule, 

these ‘‘other waters’’ (those which do 

not fit within the proposed categories of 

waters jurisdictional by rule) would 

only be jurisdictional upon a casespecific determination that they have a 

significant nexus as defined by the 

proposed rule. Waters in a watershed in 

which there is no connection to a 

traditional navigable water, interstate 

water or the territorial seas would not be 

‘‘waters of the United States.’’ In 

addition, the proposed rule would for 

the first time explicitly exclude some 

features and waters over which the 

agencies have not generally asserted 

jurisdiction and in so doing would 

eliminate the authority of the agencies 

to determine in case specific 

circumstances that some such waters are 

jurisdictional ‘‘waters of the United 

States.’’ 

The agencies propose a rule that is 

clear and understandable and that 

protects the nation’s waters, consistent 

with the law and currently available 

scientific and technical expertise. 

Continuity with the existing regulations, 

where possible, will reduce confusion 

and will reduce transaction costs for the 

regulated community and the agencies. 

To that same end, the agencies also 

propose, where consistent with the law 

and their scientific and technical 

expertise, categories of waters that are 

and are not jurisdictional, as well as 

categories of waters and wetlands that 

require a case-specific significant nexus 

evaluation to determine whether they 

are ‘‘waters of the United States’’ and 

protected by the CWA. Finally, the 

agencies propose definitions for some of 

the terms used in the proposed 

regulation. 

This preamble also presents several 

alternative options for determining the 

jurisdictional status of certain ‘‘other 

waters’’ that would rely less, or not at 

all, on case-specific significant nexus 

evaluations. The agencies may adopt 

one or a combination of these options 

for the final rule, after considering 

public comment and the evolving 

scientific literature on connectivity of 

waters. This preamble also seeks 

comment on a number of other ways 

that the agencies might provide even 

greater clarity, certainty, and 

predictability in determining which 

‘‘other waters’’ are and are not subject 

to CWA jurisdiction. The agencies 

evaluated extensive peer reviewed 

science in making their determination 

in the proposed rule. However, the 

agencies also seek additional 

information that would enhance the 

predictability and accuracy of its 

jurisdictional determinations. The 

agencies request the type of information 

on the evolving scientific literature on 

connectivity of waters that could allow 

the agencies to rely less on case-specific 

significant nexus evaluations. 

Under the proposed first section of 

the regulation, section (a), the agencies 

propose to define the ‘‘waters of the 

United States’’ for all sections 


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(including sections 301, 311, 401, 402, 

404) of the CWA to mean: 

• All waters which are currently 

used, were used in the past, or may be 

susceptible to use in interstate or foreign 

commerce, including all waters which 

are subject to the ebb and flow of the 

tide; 

• All interstate waters, including 

interstate wetlands; 

• The territorial seas; 

• All impoundments of a traditional 

navigable water, interstate water, the 

territorial seas or a tributary; 

• All tributaries of a traditional 

navigable water, interstate water, the 

territorial seas or impoundment; 

• All waters, including wetlands, 

adjacent to a traditional navigable water, 

interstate water, the territorial seas, 

impoundment or tributary; and 

• On a case-specific basis, other 

waters, including wetlands, provided 

that those waters alone, or in 

combination with other similarly 

situated waters, including wetlands, 

located in the same region, have a 

significant nexus to a traditional 

navigable water, interstate water or the 

territorial seas. 

As discussed in further detail below, 

the rule would not change the following 

provisions of the existing rule (although 

some provisions have been 

renumbered): Traditional navigable 

waters; interstate waters; the territorial 

seas; and impoundments of ‘‘waters of 

the United States.’’ In paragraph (a)(5) of 

the proposed rule, the agencies propose 

that all tributaries as defined in the 

proposed rule are ‘‘waters of the United 

States.’’ While tributaries are ‘‘waters of 

the United States’’ under the existing 

regulation, the rule would for the first 

time include a regulatory definition of 

‘‘tributary.’’ 

With this proposed rule, the agencies 

conclude, based on existing science and 

the law, that a significant nexus exists 

between tributaries (as defined in the 

proposed rule) and the traditional 

navigable waters, interstate waters, and 

the territorial seas into which they flow; 

and between adjacent water bodies (as 

defined in the proposed rule) and 

traditional navigable waters, interstate 

waters, and the territorial seas, 

respectively. Consequently, this rule 

establishes as ‘‘waters of the United 

States,’’ all tributaries (as defined in the 

proposal), of the traditional navigable 

waters, interstate waters, and the 

territorial seas, as well as all adjacent 

waters (including wetlands). This will 

eliminate the need to make a casespecific significant nexus determination 

for tributaries or for their adjacent 

waters because it has been determined 

that as a category, these waters have a 

significant nexus and thus are ‘‘waters 

of the United States.’’ 

In paragraph (a)(6) of the proposed 

rule, the rule would clarify that adjacent 

waters, rather than simply adjacent 

wetlands, are ‘‘waters of the United 

States.’’ The rule would further clarify 

the meaning of ‘‘adjacent’’ by defining 

one of its elements, ‘‘neighboring.’’ The 

related terms of ‘‘riparian area’’ and 

‘‘floodplain’’ are also defined in the 

proposed rule. 

The rule states that on a case-specific 

basis ‘‘other waters’’ that have a 

significant nexus to a traditional 

navigable water, interstate water or the 

territorial seas are ‘‘waters of the United 

States.’’ Unlike the categories of waters 

in paragraphs (a)(1) through (6), which 

would be jurisdictional by definition, 

these ‘‘other waters’’ would not be 

‘‘waters of the United States’’ by 

definition; rather, these ‘‘other waters’’ 

would only be jurisdictional provided 

that they have been determined on a 

case-specific basis to have a significant 

nexus to a paragraph (a)(1) through 

(a)(3) water. Therefore, the rule also 

includes a definition of ‘‘significant 

nexus.’’ 

‘‘Significant nexus’’ is not itself a 

scientific term. The relationship that 

waters can have to each other and 

connections downstream that affect the 

chemical, physical, or biological 

integrity of traditional navigable waters, 

interstate waters, or the territorial seas 

is not an all or nothing situation. The 

existence of a connection, a nexus, does 

not by itself establish that it is a 

‘‘significant nexus.’’ There is a gradient 

in the relation of waters to each other, 

and this is documented in the Report. 

The agencies propose a case-specific 

analysis in establishing jurisdiction over 

these ‘‘other waters’’ as consistent with 

the current science, the CWA, and the 

caselaw. A case-specific analysis allows 

for a determination of jurisdiction at the 

point on the gradient in the relationship 

that constitutes a ‘‘significant nexus.’’ In 

the proposed regulation the rule defines 

the following terms: adjacent, 

neighboring, riparian area, floodplain, 

tributary, wetlands, and significant 

nexus. However, the agencies also 

recognize that relying on a case-specific 

analysis provides less certainty to the 

regulated public on the jurisdictional 

status of other waters and is considering 

other approaches, as discussed later in 

this preamble. 

The proposed section (b) excludes 

specified waters and features from the 

definition of ‘‘waters of the United 

States.’’ Waters and features that are 

determined to be excluded under 

section (b) of the proposed rule will not 

be jurisdictional under any of the 

categories in the proposed rule under 

section (a), even if they would otherwise 

satisfy the regulatory definition. Those 

waters and features that would not be 

‘‘waters of the United States’’ are: 

• Waste treatment systems, including 

treatment ponds or lagoons, designed to 

meet the requirements of the Clean 

Water Act. 

• Prior converted cropland. 

Notwithstanding the determination of 

an area’s status as prior converted 

cropland by any other Federal agency, 

for the purposes of the Clean Water Act 

the final authority regarding Clean 

Water Act jurisdiction remains with 

EPA. 

• Ditches that are excavated wholly 

in uplands, drain only uplands, and 

have less than perennial flow. 

• Ditches that do not contribute flow, 

either directly or through another water, 

to a traditional navigable water, 

interstate water, the territorial seas or an 

impoundment of a jurisdictional water. 

• The following features: 

Æ Artificially irrigated areas that 

would revert to upland should 

application of irrigation water to that 

area cease; 

Æ artificial lakes or ponds created by 

excavating and/or diking dry land and 

used exclusively for such purposes as 

stock watering, irrigation, settling 

basins, or rice growing; 

Æ artificial reflecting pools or 

swimming pools created by excavating 

and/or diking dry land; 

Æ small ornamental waters created by 

excavating and/or diking dry land for 

primarily aesthetic reasons; 

Æ water-filled depressions created 

incidental to construction activity; 

Æ groundwater, including 

groundwater drained through 

subsurface drainage systems; and 

Æ gullies and rills and non-wetland 

swales. 

The rule does not affect longstanding 

exemptions in the CWA for farming, 

silviculture, ranching and other 

activities, does not change regulatory 

exclusions for waste treatment systems 

and prior converted cropland, and does 

not change the regulatory status of water 

transfers. Where waters would be 

determined jurisdictional under the 

proposed rule, applicable exemptions of 

the CWA would continue to preclude 

application of CWA permitting 

requirements. For example, if ‘‘other 

waters’’ are aggregated as similarly 

situated in the region and determined to 

be jurisdictional, any exempt activities 

that include a discharge to those waters 

would remain outside the regulatory 

requirements of the CWA. Exempted 

discharges are established under CWA 

sections 402, 502, and 404 and include: 


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Agricultural stormwater discharges; 

return flows from irrigated agriculture; 

normal farming, silvicultural, and 

ranching activities; upland soil and 

water conservation practices; 

construction or maintenance of farm or 

stock ponds or irrigation ditches; 

maintenance of drainage ditches; and 

construction or maintenance of farm, 

forest, and temporary mining roads. 

To provide additional clarity to 

farmers, the agencies are today also 

issuing an interpretive rule clarifying 

the applicability of the permitting 

exemption provided under section 

404(f)(1)(A) of the CWA to discharges of 

dredged or fill material associated with 

certain agricultural conservation 

practices based on the Natural 

Resources Conservation Service 

conservation practice standards and that 

are designed and implemented to 

protect and enhance water quality. This 

interpretive rule was developed in 

coordination with the U.S. Department 

of Agriculture, was signed by EPA and 

the Army, and became effective 

immediately. The agencies recognize, 

however, the value of receiving public 

comment on the interpretive rule and 

are publishing it by separate notice in 

the Federal Register. The public is 

encouraged to provide their comments 

on the interpretive rule to the docket on 

the interpretive rule, Docket Id. No. 

EPA–HQ–OW–2013–0820, and not to 

this docket. The interpretive rule and 

the request for comments can be found 

at http://water.epa.gov/lawsregs/

guidance/wetlands/agriculture.cfm and 

at http://www.regulations.gov via 

Docket Id. No. EPA–HQ–OW–2013– 

0820. 

The proposed rule is expected to 

reduce documentation requirements and 

the time it takes to make approved 

jurisdictional determinations by 

decreasing the number of jurisdictional 

determinations that require case-specific 

significant nexus analysis evaluations. It 

will improve clarity for regulators, 

stakeholders and the regulated public by 

defining certain categories of waters as 

‘‘waters of the United States’’ that 

previously required case-specific 

analyses prior to establishing CWA 

jurisdiction through the approved 

jurisdictional determination procedures. 

A comprehensive review of a growing 

body of scientific literature, as well as 

the agencies’ growing body of scientific 

and technical knowledge and field 

expertise, led the agencies to conclude 

that it is reasonable to establish certain 

categories of waters that are 

jurisdictional by rule as they have a 

significant nexus to an (a)(1) through 

(a)(3) water, specifically tributaries to 

traditional navigable waters, interstate 

waters, or the territorial seas, and their 

adjacent waters and wetlands. Casespecific jurisdictional determinations 

would still be required for the ‘‘other 

waters’’ category in paragraph (a)(7) of 

the proposed rule. Under the alternate 

approaches affecting ‘‘other waters’’ 

described later in the preamble, the 

agencies request comment on the casespecific analysis. 

A review of the scientific literature, 

including the Report of the peerreviewed science, shows that tributaries 

and adjacent waters play an important 

role in maintaining the chemical, 

physical, and biological integrity of 

traditional navigable waters, interstate 

waters, and the territorial seas—and of 

other jurisdictional waters—because of 

their hydrological and ecological 

connections to and interactions with 

those waters. Therefore, it is appropriate 

to protect all tributaries and adjacent 

waters, because the tributaries, adjacent 

waters, and the downstream traditional 

navigable waters, interstate waters, and 

the territorial seas function as an 

integrated system. Water flows through 

tributaries to downstream traditional 

navigable waters, interstate waters, and 

the territorial seas, and that water 

carries pollutants that affect the 

chemical, physical, and biological 

integrity of the (a)(1) through (a)(3) 

waters, including water quality, 

fisheries, recreation, and other 

ecological services. 

In discussing the significant nexus 

standard, Justice Kennedy stated: ‘‘The 

required nexus must be assessed in 

terms of the statute’s goals and 

purposes. Congress enacted the [CWA] 

to ‘restore and maintain the chemical, 

physical, and biological integrity of the 

Nation’s waters. . . .’ ’’ 547 U.S. at 779. 

To protect the integrity of the waters 

subject to the CWA, the significant 

nexus standard must be implemented in 

a manner that restores and maintains 

any of these three attributes of 

traditional navigable waters, interstate 

waters, or the territorial seas. Waters 

adjacent to tributaries also provide 

ecological functions that, in conjunction 

with the functions provided by the 

tributaries they are adjacent to, have a 

significant influence on the chemical, 

physical, and biological integrity of 

downstream traditional navigable 

waters, interstate waters, and the 

territorial seas. 

Examples of the important functions 

provided by adjacent waters are the 

sequestering or transformation of 

pollutants to reduce inputs to tributaries 

and subsequently to downstream (a)(1) 

through (a)(3) waters, water storage, and 

sediment trapping. Thus, in some 

instances, the significance of adjacent 

waters is to prevent or delay a 

hydrological connection with 

downstream waters and store water and/ 

or pollutants. Given the large scale 

systematic interactions that occur, and 

the substantial effects that result, among 

tributaries, adjacent waters, and the 

downstream traditional navigable 

waters, interstate waters, or the 

territorial seas, a significant nexus exists 

that warrants making those categories of 

waters jurisdictional by rule. 

States and tribes play a vital role in 

the implementation and enforcement of 

the CWA. Section 101(b) of the CWA 

states that it is Congressional policy to 

preserve the primary responsibilities 

and rights of states to prevent, reduce, 

and eliminate pollution, to plan the 

development and use of land and water 

resources, and to consult with the 

Administrator with respect to the 

exercise of the Administrator’s authority 

under the CWA. 

Of particular importance, states and 

tribes may be authorized by the EPA to 

administer the permitting programs of 

sections 402 and 404. Forty-six states 

and the Virgin Islands are authorized to 

administer the NPDES program under 

section 402, while two states administer 

the section 404 program. Additional 

CWA programs that utilize the 

definition of ‘‘waters of the United 

States’’ and are of importance to the 

states and tribes include the section 311 

oil spill prevention and response 

program, the water quality standards 

and total maximum daily load programs 

under section 303, and the section 401 

state water quality certification process. 

States and tribes, consistent with the 

CWA, retain full authority to implement 

their own programs to more broadly or 

more fully protect the waters in their 

state. Under section 510 of the Act, 

unless expressly stated in the CWA, 

nothing in the Act precludes or denies 

the right of any state or tribe to establish 

more protective standards or limits than 

the Federal CWA. Many states and 

tribes, for example, protect 

groundwater, and some others protect 

wetlands that are vital to their 

environment and economy but which 

are outside the regulatory jurisdiction of 

the CWA. Nothing in this proposed rule 

would limit or impede any existing or 

future state or tribal efforts to further 

protect their waters. In fact, providing 

greater clarity regarding what waters are 

subject to CWA jurisdiction will reduce 

the need for permitting authorities, 

including the states and tribes that have 

authorized section 402 and 404 CWA 

permitting programs, to make 

jurisdictional determinations on a casespecific basis, leaving them with more 

resources to protect their waters. 


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This proposal also recognizes the 

unique role of states related to water 

quantity and as stated in the CWA. The 

proposal does not affect Congressional 

policy not to supersede, abrogate or 

otherwise impair the authority of each 

state to allocate quantities of water 

within its jurisdiction and neither does 

it affect the policy of Congress that 

nothing in the CWA shall be construed 

to supersede or abrogate rights to 

quantities of water which have been 

established by any state. CWA section 

101(g). 

While a principal goal of this 

rulemaking is to improve clarity for 

determining jurisdiction under the CWA 

in light of the two most recent Supreme 

Court cases with the dual benefits of 

improving certainty and greater 

efficiency for determining whether 

waters are covered, there are other tools 

and approaches underway to increase 

efficiency as well. For example, to 

improve efficiencies, the EPA and the 

Corps are working in partnership with 

states to develop new tools and 

resources that have the potential to 

improve precision of desk based 

jurisdictional determinations at lower 

cost and improved speed than the 

existing primarily field-based 

approaches. In the normal course of 

making jurisdictional determinations, 

information derived from field 

observation is not always required in 

cases where a ‘‘desktop’’ analysis 

furnishes sufficient information to make 

the requisite findings. However, for 

more complex or difficult jurisdictional 

determinations, it may be helpful to 

supplement such information with field 

observation. 

EPA and the Corps are very interested 

in identifying other emerging 

technologies or approaches that would 

save time and money and improve 

efficiency for regulators and the 

regulated community in determining 

which waters are subject to CWA 

jurisdiction. The agencies specifically 

invite comment on this topic. 

The proposed rule will benefit the 

nation by helping to protect the services 

and functions these important water 

bodies provide consistent with the 

overarching objective of the CWA. 

B. The Clean Water Act and Regulatory 

Definition of ‘‘Waters of the United 

States’’ 

The Federal Water Pollution Control 

Act Amendments, now known as the 

Clean Water Act, were enacted in 1972. 

The objective of the CWA is to restore 

and maintain the chemical, physical, 

and biological integrity of the Nation’s 

waters. CWA section 101(a). Its specific 

provisions were designed to improve 

the protection of the nation’s waters 

provided under earlier statutory 

schemes such as certain sections of the 

Rivers and Harbors Appropriations Act 

of 1899 (‘‘RHA’’) (33 U.S.C. 03, 407, 

411) and the Federal Water Pollution 

Control Act of 1948 (62 Stat. 1155) and 

its subsequent amendments through 

1970. The jurisdictional scope of the 

CWA is ‘‘navigable waters,’’ defined in 

the statute as ‘‘waters of the United 

States, including the territorial seas.’’ 

CWA section 502(7). The CWA leaves it 

to the agencies to define the term 

‘‘waters of the United States.’’ Existing 

agency regulations define ‘‘waters of the 

United States’’ as traditional navigable 

waters, interstate waters, all other 

waters that could affect interstate or 

foreign commerce, impoundments of 

waters of the United States, tributaries, 

the territorial seas, and adjacent 

wetlands. 33 CFR 328.3; 40 CFR 

230.3(s). Counterpart and substantively 

similar regulatory definitions appear at 

40 CFR 110.1, 112.2, 116.3, 117.1, 122.2, 

232.2, 300.5, part 300 App. E, 302.3 and 

401.11. 

The current regulatory definition of 

‘‘waters of the United States’’ provides 

two specific exclusions from ‘‘waters of 

the United States.’’ Waste treatment 

systems designed to meet the 

requirements of the CWA and prior 

converted cropland are not ‘‘waters of 

the United States’’ under the agencies’ 

current regulations. Under the 

regulations for prior converted 

cropland, notwithstanding the 

determination of an area’s status as prior 

converted cropland by any other Federal 

agency, for the purposes of the Clean 

Water Act, the final authority regarding 

Clean Water Act jurisdiction remains 

with EPA. 33 CFR 328.3(a)(8). 

C. Background on Scientific Review and 

Significant Nexus Analysis 

1. Scientific Synthesis 

EPA’s Office of Research and 

Development prepared a draft peerreviewed synthesis of published peerreviewed scientific literature discussing 

the nature of connectivity and effects of 

streams and wetlands on downstream 

waters (U.S. Environmental Protection 

Agency, Connectivity of Streams and 

Wetlands to Downstream Waters: A 

Review and Synthesis of the Scientific 

Evidence, (Washington, DC: U.S. 

Environmental Protection Agency, 

2013), (the ‘‘Report’’)). The draft Report 

provides a review and synthesis of the 

scientific information pertaining to 

chemical, physical, and biological 

connections from streams, wetlands, 

and open waters such as oxbow lakes, 

to downstream larger water bodies such 

as rivers, lakes, and estuaries in 

watersheds across the United States and 

the strength of those connections. While 

the scientific literature does not use the 

term ‘‘significant nexus,’’ there is a 

substantial body of scientific literature 

on the chemical, physical, and 

biological connections between 

tributaries and adjacent waters and 

‘‘other waters’’ and the downstream 

larger waters, and on the strength and 

the effect of these connections. 

Connectivity is a foundational 

concept in hydrology and freshwater 

ecology. Connectivity is the degree to 

which components of a system are 

joined, or connected, by various 

transport mechanisms and is 

determined by the characteristics of 

both the physical landscape and the 

biota of the specific system. The 

structure and function of downstream 

waters are highly dependent on the 

constituent materials contributed by and 

transported through waters located 

elsewhere in the watershed. 

Connectivity for purposes of 

interpreting the scope of ‘‘waters of the 

United States’’ under the CWA serves to 

demonstrate the ‘‘nexus’’ between 

upstream water bodies and the 

downstream traditional navigable water, 

interstate water, or the territorial sea. 

Based on the literature, the Office of 

Research and Development was able to 

assess the types of connections between 

the tributaries and adjacent waters and 

the chemical, physical, and biological 

integrity of downstream traditional 

navigable waters, interstate waters, and 

the territorial seas. 

However, as Justice Kennedy found in 

Rapanos, a mere hydrologic connection 

may not suffice in all cases to establish 

CWA jurisdiction and there needs to be 

‘‘some measure of the significance of the 

connection for downstream water 

quality.’’ 547 U.S. at 784–785 (‘‘mere 

hydrologic connection should not 

suffice in all cases; the connection may 

be too insubstantial for the hydrologic 

linkage to establish the required nexus 

with navigable waters as traditionally 

understood’’). The literature does not 

use the term ‘‘significant’’ but does 

provide information on the strength of 

the effects on the chemical, physical, 

and biological functioning of the 

downstream water bodies from the 

connections among tributaries and 

adjacent waters and ‘‘other waters’’ and 

those downstream waters. 

While ‘‘strength’’ of connections to 

and effects on the integrity of 

downstream waters and the 

‘‘significance’’ of the nexus to the 

integrity of downstream waters are 

clearly related inquiries, ‘‘significant’’ is 

not a scientific term but rather a 


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determination of the agencies in light of 

the law and science. The relative 

strength of downstream effects informs 

the agencies’ conclusions about the 

significance of those effects for purposes 

of interpreting the CWA. The data and 

conclusions in the Report concerning 

the strength of the relevant connections 

and effects of certain types of waters on 

downstream waters provide a 

foundation for the agencies’ 

determinations that certain waters have 

effects on the chemical, physical, and 

biological integrity of traditional 

navigable waters, interstate waters, or 

the territorial seas that are ‘‘significant’’ 

and thus constitute a significant nexus. 

As clarified in the proposed definition 

of ‘‘significant nexus’’ and consistent 

with Justice Kennedy’s guidance, for an 

effect to be significant it must be more 

than speculative or insubstantial. 

The Office of Research and 

Development’s review and synthesis of 

more than a thousand publications from 

peer-reviewed scientific literature 

focuses on evidence of those 

connections from various categories of 

waters, evaluated singly or in aggregate, 

which affect downstream waters and the 

strength of that effect. Much of the 

scientific literature relied on does not 

use the terms traditional navigable 

waters, interstate waters, or the 

territorial seas. However, evidence of 

strong chemical, physical, and 

biological connections to larger rivers, 

estuaries and lakes applies to that subset 

of rivers, estuaries and lakes that are 

traditional navigable waters, interstate 

waters, or the territorial seas. The 

objectives of the Report are (1) to 

provide a context for considering the 

evidence of connections between 

downstream waters and their tributary 

waters, and (2) to summarize current 

understanding about these connections, 

the factors that influence them, and the 

mechanisms by which the connections 

affect the function or condition of 

downstream waters. The connections 

and mechanisms discussed in the 

Report include transport of physical 

materials and chemicals such as water, 

wood, sediment, nutrients, pesticides, 

and mercury; functions that adjacent 

waters perform, such as storing and 

cleansing water; movement of organisms 

or their seeds and eggs; and hydrologic 

and biogeochemical interactions 

occurring in and among surface and 

groundwater flows, including hyporheic 

zones and alluvial aquifers. 

The Report concludes that the 

scientific literature clearly demonstrates 

that streams, regardless of their size or 

how frequently they flow, strongly 

influence how downstream waters 

function. Streams supply most of the 

water in rivers, transport sediment and 

organic matter, provide habitat for many 

species, and take up or change nutrients 

that could otherwise impair 

downstream waters. The Report also 

concludes that wetlands and open 

waters in floodplains of streams and 

rivers and in riparian areas (transition 

areas between terrestrial and aquatic 

ecosystems) have a strong influence on 

downstream waters. Such waters act as 

the most effective buffer to protect 

downstream waters from nonpoint 

source pollution (such as nitrogen and 

phosphorus), provide habitat for 

breeding fish and aquatic insects that 

also live in streams, and retain 

floodwaters, sediment, nutrients, and 

contaminants that could otherwise 

negatively impact the condition or 

function of downstream waters. 

Regarding wetlands and open waters 

located outside of floodplains and 

riparian areas, the Report finds that they 

provide many benefits to rivers, lakes, 

and other downstream waters. If the 

wetland or open water has a surface or 

shallow subsurface water connection to 

the river network, it affects the 

condition of downstream waters. Where 

the wetland or open water is not 

connected to the river network through 

surface or shallow subsurface water, the 

type and degree of connectivity varies 

geographically, topographically, and 

ecologically, such that the significance 

of the connection is difficult to 

generalize across the entire group of 

waters. 

Lastly, the Report concludes that to 

understand the health, behavior, and 

sustainability of downstream waters, the 

effects of small water bodies in a 

watershed need to be considered in 

aggregate. The contribution of material 

by, or an important water-retention 

function of, a particular stream, other 

open water, or wetland might be small, 

but the aggregate contribution by an 

entire class of streams, other open 

waters, and wetlands (e.g., all 

ephemeral streams in the river network) 

can be substantial. 

In the proposed rule, the agencies 

interpreted the scope of ‘‘waters of the 

United States’’ in the CWA based on the 

information and conclusions in the 

Report, other relevant scientific 

literature, the agencies’ technical 

expertise, and the objectives and 

requirements of the Clean Water Act. In 

light of this information, the agencies 

made judgments about the nexus 

between the relevant waters and the 

significance of that nexus and 

concluded that tributaries and adjacent 

waters, each as defined by the proposed 

rule, have a significant nexus such that 

they are appropriately jurisdictional by 

rule. 

The Report is currently undergoing 

peer review by EPA’s Scientific 

Advisory Board (SAB) and is available 

at http://yosemite.epa.gov/sab/

sabproduct.nsf/fedrgstr_activites/

Watershed%20Connectivity%20Report?

OpenDocument. A previous version of 

the Report dated October 11, 2011 

underwent an independent peer review 

organized by the Eastern Research 

Group, Inc. (ERG). The purpose of the 

ERG-organized peer review was to 

determine whether the review and 

interpretation of the scientific literature 

was complete and correct, and if the 

conclusions in the Report were 

supported by the evidence. ERG was 

responsible for identifying and selecting 

the expert reviewers, managing the 

review, organizing and facilitating a 

one-day peer review meeting, and 

preparing the peer review summary 

report. ERG provided the reviewers with 

a letter of instruction and the technical 

charge, which asked for their comments 

on the various aspects of the draft 

report. 

ERG convened the one-day meeting 

on January 31, 2012, in Washington, DC. 

The meeting was closed to the public 

and considered an internal EPA 

deliberative process. Observers from 

EPA and the Corps attended to listen to 

the discussions. At the close of the 

meeting, the reviewers developed some 

brief highlights of their discussions, 

which were provided with written postmeeting comments from individual 

reviewers in a report from ERG titled 

‘‘Peer Review Meeting of EPA’s Draft 

Report: Connectivity of Streams and 

Wetlands to Downstream Waters—A 

Review and Synthesis of the Scientific 

Evidence, Post-Meeting Comments,’’ 

dated February 16, 2012. The Office of 

Research and Development revised its 

Report in response to the peer review 

comments and submitted the Report to 

the SAB for peer review and a public 

process. This peer review report is 

available in the docket for the proposed 

rule. 

The agencies have identified key 

aspects of the Report throughout this 

preamble and in Appendix A. The 

Report summarizes and assesses much 

of the currently available scientific 

literature that is part of the 

administrative record for this proposal, 

and informs the agencies during this 

rulemaking. Additional data and 

information will become available 

during the rulemaking process, 

including that provided during the 

public comment process, and by 

additional research, studies, and 

investigations that take place before the 


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rulemaking process is concluded. The 

agencies have relied on the best 

available scientific data and 

information—peer-reviewed literature— 

and would find, to the extent possible, 

additional peer-reviewed literature to be 

the most useful submissions. At the 

conclusion of the rulemaking process, 

the agencies will review the entirety of 

the completed administrative record, 

including the final Report reflecting 

SAB review, and make any adjustments 

to the final rule that are appropriate 

based on this record. As noted below, 

the agencies particularly intend to 

review the rule provisions related to 

‘‘other waters’’ in light of this record, 

and are soliciting comment on several 

alternative approaches to applying the 

science and the law for determining 

whether ‘‘other waters’’ are similarly 

situated and have a ‘‘significant nexus’’ 

to a traditional navigable water, 

interstate water, or the territorial seas. 

2. Summary of Significant Nexus 

Conclusions 

As the agencies developed this 

proposed definition of ‘‘waters of the 

United States,’’ the agencies carefully 

considered available scientific literature 

and propose a rule consistent with their 

conclusions that a particular category of 

waters either alone or in combination 

with similarly situated waters in the 

region, significantly affects the 

chemical, physical, or biological 

integrity of traditional navigable waters, 

interstate waters, or the territorial seas. 

As discussed in this preamble and 

Appendix A, tributaries as proposed to 

be defined perform the requisite 

functions for them to be considered 

‘‘waters of the United States’’ by rule. 

Tributary streams exert a strong 

influence on the character and 

functioning of downstream traditional 

navigable waters, interstate waters, and 

the territorial seas, either individually 

or cumulatively. All tributary streams, 

including perennial, intermittent, and 

ephemeral streams, are physically and 

chemically connected to downstream 

traditional navigable waters, interstate 

waters, and the territorial seas via 

channels and associated alluvial 

deposits where water and other 

materials are concentrated, mixed, 

transformed, and transported. 

Headwater streams (which can be 

ephemeral, intermittent or perennial), in 

particular, supply most of the water to 

downstream traditional navigable 

waters, interstate waters, and the 

territorial seas and are the most 

abundant stream-type in most river 

networks. In addition to water, tributary 

streams supply sediment, wood, organic 

matter, nutrients, chemical 

contaminants, and many of the 

organisms found in downstream 

traditional navigable waters, interstate 

waters, and the territorial seas. 

Tributary streams are biologically 

connected to downstream traditional 

navigable waters, interstate waters, and 

the territorial seas by dispersal and 

migration of aquatic and semi-aquatic 

organisms, including fish, amphibians, 

plants, and invertebrates, that use both 

upstream and downstream habitats 

during one or more stages of their life 

cycles, or provide food resources to 

downstream communities. Chemical, 

physical, and biological connections 

between tributary streams and 

downstream traditional navigable 

waters, interstate waters, and the 

territorial seas interact via processes 

such as nutrient spiraling, in which 

tributary stream communities assimilate 

and chemically transform large 

quantities of nitrogen that would 

otherwise increase nutrient loading 

downstream. 

As discussed in this preamble and 

Appendix A, adjacent waters, as defined 

in this proposal, perform the requisite 

functions for them to be considered 

‘‘waters of the United States’’ by rule. 

Adjacent waters are either directly 

chemically, physically, or biologically 

connected with traditional navigable 

waters, interstate waters, and the 

territorial seas they are adjacent to, or 

they are connected to such waters 

through tributaries. These chemical, 

physical, and biological connections 

affect the integrity of downstream 

traditional navigable waters, interstate 

waters, and the territorial seas through 

the export of channel-forming sediment 

and woody debris, storage of local 

groundwater sources of baseflow for 

downstream waters and their tributaries, 

and transport of organic matter. 

Wetlands and open waters located in 

riparian and floodplain areas remove 

and transform nutrients such as nitrogen 

and phosphorus. They provide nursery 

habitat for fish, and colonization 

opportunities for stream invertebrates. 

Adjacent waters, including those 

located in riparian and floodplain areas, 

serve an important role in the integrity 

of traditional navigable waters, 

interstate waters, and the territorial seas 

because they also act as sinks for water, 

sediment, nutrients, and contaminants 

that could otherwise negatively impact 

traditional navigable waters, interstate 

waters, and the territorial seas. 

Finally, some non-adjacent waters 

may have, in certain circumstances, a 

significant nexus to traditional 

navigable waters, interstate waters, and 

the territorial seas, but at this time the 

agencies are not proposing that a 

category of such ‘‘other waters’’ is 

jurisdictional by rule. These ‘‘other 

waters’’ may provide numerous 

functions of potential benefit to 

traditional navigable waters, interstate 

waters, and the territorial seas, 

including storage of floodwater; 

retention of nutrients, metals, and 

pesticides; and re-charge of groundwater 

sources of river baseflow. The functions 

of these ‘‘other waters’’ may affect 

downstream traditional navigable 

waters, interstate waters, and the 

territorial seas, depending on the 

characteristics of the connection to the 

river network. For ‘‘other waters,’’ 

connectivity varies within a watershed 

and over time, making it difficult to 

generalize about their connections to, or 

isolation from, traditional navigable 

waters, interstate waters, and the 

territorial seas. These ‘‘other waters’’ 

would be evaluated on a case-specific 

basis under the proposed rule. 

Under the existing regulations, ‘‘other 

waters’’ (such as intrastate rivers, lakes 

and wetlands that are not otherwise 

jurisdictional under other sections of 

the rule) could be determined to be 

jurisdictional if the use, degradation or 

destruction of the water could affect 

interstate or foreign commerce. 

Jurisdictional decisions for these waters 

are being made on a case-specific basis. 

As a practical matter in the past, the 

agencies generally relied on the 

presence of migratory birds to indicate 

an effect on interstate commerce. In 

2001, the Supreme Court in SWANCC 

rejected the use of migratory birds as a 

sole basis to establish jurisdiction over 

such ‘‘isolated’’ intrastate nonnavigable 

waters. 

The proposed rule provides that 

‘‘other waters’’ can be jurisdictional 

where there is a case-specific showing 

of a significant nexus to traditional 

navigable waters, interstate waters, or 

the territorial seas. ‘‘Significant nexus’’ 

is not itself a scientific term. The 

science of connections and effects on 

the chemical, physical, or biological 

integrity of traditional navigable waters, 

interstate waters, or the territorial seas 

informs an analysis of the facts and 

circumstances of the waters being 

considered under a ‘‘significant nexus’’ 

analysis. 

Scientific literature establishes that 

‘‘other waters’’ can have a relationship 

to each other and connections 

downstream that affect the chemical, 

physical, or biological integrity of 

traditional navigable waters, interstate 

waters, or the territorial seas. This 

relationship is not an all or nothing 

situation. The existence of a connection, 

a nexus, does not by itself establish that 

it is a ‘‘significant nexus.’’ There is a 


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gradient in the relation of waters to each 

other, and this is documented in the 

Report. The agencies propose a casespecific analysis in establishing 

jurisdiction over these ‘‘other waters’’ as 

consistent with the current science, the 

CWA, and the caselaw. A case-specific 

analysis allows for a determination of 

jurisdiction at the point on the gradient 

in the relationship that constitutes a 

‘‘significant nexus.’’ 

The support for a determination that 

the nexus is significant will be based on 

a record that documents the scientific 

basis for concluding which functions 

are provided by the waters and why 

their effects on a traditional navigable 

water, interstate water, or the territorial 

seas are significant, including that they 

are more than speculative or 

insubstantial. The agencies considered 

multiple options for determining how 

best to balance the science and the 

policy options available to address 

‘‘other waters.’’ Those options ranged 

from establishing jurisdiction over all 

‘‘other waters’’ with a nexus to 

traditionally navigable waters, interstate 

waters, or the territorial seas, with the 

agencies determining categorically the 

nexus to be significant, to declining to 

assert jurisdiction over any ‘‘other 

waters.’’ 

The agencies did not adopt the all in 

or the all out approach to ‘‘other 

waters.’’ Based on the information 

currently available in the scientific 

literature, applicable caselaw, and the 

agencies’ policy judgment about how 

best to provide clarity and certainty to 

the public regarding the jurisdictional 

status of ‘‘other waters’’ the agencies 

today propose the case-specific 

significant nexus analysis presented in 

this rule and explained in the preamble. 

In addition to the proposed ‘‘other 

waters’’ approach in this rule, the 

agencies are requesting comment on a 

range of alternate approaches to inform 

their decision on how best to address 

‘‘other waters.’’ The agencies will 

consider the full administrative record, 

including comments requested and 

received, and the final Report, as 

revised in response to the SAB review, 

when developing the final rule, and may 

adopt one of the alternative approaches 

or combination of approaches and the 

proposal. 

The agencies solicit comment on 

identifying subcategories of ‘‘other 

waters’’ that have a significant nexus to 

traditional navigable waters, interstate 

waters, and the territorial seas and 

could be jurisdictional by rule, and 

subcategories of ‘‘other waters’’ where a 

significant nexus or its absence could 

not be determined as a class and could 

be subject to a case-specific analysis 

under the rule. The Report indicates 

that there is evidence of very strong 

connections in some subcategories that 

are not included as jurisdictional by 

rule. The agencies solicit comment on 

making such subcategories of waters 

with very strong connections 

jurisdictional by rule as well as on 

making subcategories of waters that do 

not have such connections subject to a 

case-specific analysis or categorically 

non-jurisdictional under the rule. Such 

comment should explain with 

supporting documentation why a 

particular subcategory of ‘‘other waters’’ 

might or might not have a significant 

nexus to traditional navigable waters, 

interstate waters, or the territorial seas. 

The agencies do not propose absolute 

standards such as flow rates, surface 

acres, or a minimum number of 

functions for ‘‘other waters’’ to establish 

a significant nexus. A determination of 

the relationship of ‘‘other waters’’ to 

traditional navigable waters, interstate 

waters, and the territorial seas, and 

consequently the significance to these 

waters, requires sufficient flexibility to 

account for the variability of conditions 

across the country and the varied 

functions that different waters provide. 

The case-specific analysis called for in 

the proposed rule recognizes geographic 

and hydrologic variability in 

determining whether an ‘‘other water’’ 

or group of ‘‘other waters’’ possesses a 

‘‘significant nexus’’ with traditional 

navigable waters, interstate waters, or 

the territorial seas. 

III. Proposed Definition of ‘‘Waters of 

the United States’’ 

A. Summary of Proposed Rule 

This proposed rule retains much of 

the structure of the agencies’ 

longstanding definition of ‘‘waters of the 

United States,’’ and many of the existing 

provisions of that definition where 

revisions are not warranted. The 

agencies’ goal is to promulgate a rule 

that is clear and understandable and 

protects the nation’s waters, supported 

by science and consistent with the law. 

Continuity with the existing regulations, 

where possible, will minimize 

confusion and will reduce transaction 

costs for the regulated community and 

the agencies. To that same end, the 

agencies also propose, where supported 

by scientific literature and consistent 

with the law, bright line categories of 

waters that are and are not 

jurisdictional. Waters in the ‘‘other 

waters’’ category are not a per se 

jurisdictional category. While the 

agencies considered multiple options 

for addressing jurisdiction over ‘‘other 

waters,’’ the agencies concluded that 

they could not determine that all ‘‘other 

waters’’ were jurisdictional, or that all 

‘‘other waters’’ were not jurisdictional. 

Therefore, the proposed rule requires a 

case-specific significant nexus 

evaluation to determine if such ‘‘other 

waters’’ are subject to CWA jurisdiction 

and the agencies are requesting 

comment on several alternate 

approaches, including approaches that 

would not include case-specific 

analysis, to inform the final rule. 

Finally, the agencies are for the first 

time proposing definitions for some of 

the terms used in the proposed 

regulation. 

Under section (a) the agencies 

propose to define the ‘‘waters of the 

United States’’ for all sections of the 

CWA to mean: 

• All waters which are currently 

used, were used in the past, or may be 

susceptible to use in interstate or foreign 

commerce, including all waters which 

are subject to the ebb and flow of the 

tide; 

• All interstate waters, including 

interstate wetlands; 

• The territorial seas; 

• All impoundments of a traditional 

navigable water, interstate water, the 

territorial seas or a tributary; 

• All tributaries of a traditional 

navigable water, interstate water, the 

territorial seas or impoundment; 

• All waters, including wetlands, 

adjacent to a traditional navigable water, 

interstate water, the territorial seas, 

impoundment or tributary; and 

• On a case-specific basis, other 

waters, including wetlands, provided 

that those waters alone, or in 

combination with other similarly 

situated waters, including wetlands, 

located in the same region, have a 

significant nexus to a traditional 

navigable water, interstate water or the 

territorial seas. 

As discussed in further detail below, 

the agencies do not propose to change 

the following provisions (although some 

provisions have been renumbered): 

Traditional navigable waters ((a)(1), see 

Section III.B of this preamble); interstate 

waters ((a)(2), see Section III.C of this 

preamble); the territorial seas ((a)(3), see 

Section III.D of this preamble); and 

impoundments of ‘‘waters of the United 

States’’ ((a)(4), see Section III.E of this 

preamble). In paragraph (a)(5), the 

agencies are proposing that tributaries to 

waters identified in paragraphs (a)(1) 

through (a)(4) are ‘‘waters of the United 

States.’’ While tributaries are ‘‘waters of 

the United States’’ under the existing 

regulation, the agencies propose for the 

first time a regulatory definition of 

‘‘tributary’’ and propose that only those 

waters that meet the definition and flow 


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6The terms ‘‘in the region’’ and ‘‘watershed’’ are 

used interchangeably in this document. The 

agencies have interpreted ‘‘in the region’’ to mean 

the watershed that drains to the nearest water 

identified in paragraphs (a)(1) through (a)(3), which 

we refer to as the single point of entry watershed. 

directly or indirectly to an (a)(1) through 

(a)(3) water are ‘‘waters of the United 

States’’ (see Section III.F of this 

preamble). In paragraph (a)(6), the 

agencies propose that adjacent waters, 

rather than simply adjacent wetlands, 

are ‘‘waters of the United States.’’ The 

agencies also propose for the first time 

to define an aspect of adjacency— 

‘‘neighboring’’—and related terms (see 

Section III.G of this preamble). Finally, 

the agencies propose to define ‘‘waters 

of the United States’’ to include on a 

case-specific basis, other waters, 

including wetlands, provided that those 

waters alone, or in combination with 

other similarly situated waters, 

including wetlands, located in the same 

region, have a significant nexus to a 

water identified in paragraphs (a)(1) 

through (3). Unlike the per se 

jurisdictional categories in paragraphs 

(a)(1) through (6) of this section, such 

‘‘other waters’’ are not per se 

jurisdictional under (a)(7); rather, these 

‘‘other waters’’ are only jurisdictional 

provided that they have a significant 

nexus to (a)(1) through (a)(3) waters. 

Therefore, the agencies are providing a 

definition of ‘‘significant nexus’’ (see 

Section III.H of this preamble). 

The second section of the proposed 

regulation, section (b), excludes 

specified waters from the definition of 

‘‘waters of the United States.’’ Those 

waters and features would not be 

‘‘waters of the United States’’ even if 

they would otherwise be included 

within the categories in (a)(1) through 

(a)(7) above. They are: 

• Waste treatment systems, including 

treatment ponds or lagoons, designed to 

meet the requirements of the Clean 

Water Act. 

• Prior converted cropland. 

Notwithstanding the determination of 

an area’s status as prior converted 

cropland by any other Federal agency, 

for the purposes of the Clean Water Act 

the final authority regarding Clean 

Water Act jurisdiction remains with 

EPA. 

• Ditches that are excavated wholly 

in uplands, drain only uplands, and 

have less than perennial flow. 

• Ditches that do not contribute flow, 

either directly or through another water, 

to a traditional navigable water, 

interstate water, the territorial seas or a 

jurisdictional impoundment. 

• The following features: 

Æ artificially irrigated areas that 

would revert to upland should 

application of irrigation water to that 

area cease; 

Æ artificial lakes or ponds created by 

excavating and/or diking dry land and 

used exclusively for such purposes as 

stock watering, irrigation, settling 

basins, or rice growing; 

Æ artificial reflecting pools or 

swimming pools created by excavating 

and/or diking dry land; 

Æ small ornamental waters created by 

excavating and/or diking dry land for 

primarily aesthetic reasons; 

Æ water-filled depressions created 

incidental to construction activity; 

Æ groundwater, including 

groundwater drained through 

subsurface drainage systems; and 

Æ gullies and rills and non-wetland 

swales. 

The agencies do not propose any 

changes to the existing exclusions for 

waste treatment systems designed 

consistent with the requirements of the 

CWA and for prior converted cropland. 

The CWA and current regulations also 

provide a number of exemptions from 

permitting for discharges associated 

with specific activities. The rule does 

not affect any of the exemptions from 

CWA section 404 permitting 

requirements provided by CWA section 

404(f), including those for normal 

farming, silviculture, and ranching 

activities. CWA section 404(f); 40 CFR 

232.3; 33 CFR 323.4. The rule also does 

not affect either the existing statutory 

and regulatory exemptions from NPDES 

permitting requirements, such as for 

agricultural stormwater discharges and 

return flows from irrigated agriculture, 

or the status of water transfers. CWA 

section 402(l)(1); CWA section 402(l)(2); 

CWA section 502(14); 40 CFR 122.3(f); 

40 CFR 122.2. The agencies propose for 

the first time to exclude by rule in 

section (b) certain waters and features 

over which the agencies have as a policy 

matter generally not asserted 

jurisdiction (see Section III.I of this 

preamble). 

Finally, in section (c) of the proposed 

rule the agencies define a number of 

terms, of which ‘‘adjacent’’ and 

‘‘wetlands’’ are unchanged from existing 

definitions The term adjacent means 

bordering, contiguous or neighboring. 

Waters, including wetlands, separated 

from other waters of the United States 

by man-made dikes or barriers, natural 

river berms, beach dunes and the like 

are ‘‘adjacent waters.’’ The term 

neighboring, for purposes of the term 

‘‘adjacent’’ in this section, includes 

waters located within the riparian area 

or floodplain of a water identified in 

paragraphs (a)(1) through (5) of this 

section, or waters with a shallow 

subsurface hydrologic connection or 

confined surface hydrologic connection 

to such a jurisdictional water. The term 

riparian area means an area bordering a 

water where surface or subsurface 

hydrology directly influence the 

ecological processes and plant and 

animal community structure in that 

area. Riparian areas are transitional 

areas between aquatic and terrestrial 

ecosystems that influence the exchange 

of energy and materials between those 

ecosystems. The term floodplain means 

an area bordering inland or coastal 

waters that was formed by sediment 

deposition from such water under 

present climatic conditions and is 

inundated during periods of moderate to 

high water flows. 

The term tributary means a water 

physically characterized by the presence 

of a bed and banks and ordinary high 

water mark, as defined at 33 CFR 

328.3(e), which contributes flow, either 

directly or through another water, to a 

water identified in paragraphs (a)(1) 

through (4). In addition, wetlands, lakes, 

and ponds are tributaries (even if they 

lack a bed and banks or ordinary high 

water mark) if they contribute flow, 

either directly or through another water 

to a water identified in paragraphs (a)(1) 

through (3). A water that otherwise 

qualifies as a tributary under this 

definition does not lose its status as a 

tributary if, for any length, there are one 

or more man-made breaks (such as 

bridges, culverts, pipes, or dams), or one 

or more natural breaks (such as 

wetlands at the head of or along the run 

of a stream, debris piles, boulder fields, 

or a stream that flows underground) so 

long as a bed and banks and an ordinary 

high water mark can be identified 

upstream of the break. A tributary, 

including wetlands, can be a natural, 

man-altered, or man-made water and 

includes waters such as rivers, streams, 

lakes, ponds, impoundments, canals, 

and ditches not excluded in paragraphs 

(b)(3) or (4). 

The term wetlands means those areas 

that are inundated or saturated by 

surface or groundwater at a frequency 

and duration sufficient to support, and 

that under normal circumstances do 

support, a prevalence of vegetation 

typically adapted for life in saturated 

soil conditions. Wetlands generally 

include swamps, marshes, bogs and 

similar areas. 

The term significant nexus means that 

a water, including wetlands, either 

alone or in combination with other 

similarly situated waters in the region 

(i.e., the watershed that drains to the 

nearest water identified in paragraphs 

(a)(1) through (3)),6 significantly affects 


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22200 Federal Register / Vol. 79, No. 76 / Monday, April 21, 2014 / Proposed Rules 

7Link to Michigan’s and New Jersey’s 

Memorandum of Agreement with the Army Corps 

of Engineers identifying which waters of the US 

remain under the Corps’ jurisdiction. http://water.

epa.gov/type/wetlands/initiative_index.cfm. 

the chemical, physical, or biological 

integrity of a water identified in 

paragraphs (a)(1) through (3). For an 

effect to be significant, it must be more 

than speculative or insubstantial. Other 

waters, including wetlands, are 

similarly situated when they perform 

similar functions and are located 

sufficiently close together or sufficiently 

close to a ‘‘water of the United States’’ 

so that they can be evaluated as a single 

landscape unit with regard to their 

effect on the chemical, physical, or 

biological integrity of a water identified 

in paragraphs (a)(1) through (3). 

B. Traditional Navigable Waters 

EPA and the Corps’ existing 

regulations include within the 

definition of ‘‘waters of the United 

States’’ all waters that are currently 

used, or were used in the past, or may 

be susceptible to use in interstate or 

foreign commerce, including all waters 

which are subject to the ebb and flow of 

the tide. See, e.g., 33 CFR 328.3(a)(1); 40 

CFR 230.3(s)(1); 40 CFR 122.2 (‘‘waters 

of the U.S.’’). This section of the 

regulation encompasses those waters 

that are often referred to as ‘‘traditional 

navigable waters.’’ The agencies do not 

propose to make any changes to this 

section of the regulation. See, Appendix 

B, Legal Analysis. 

For purposes of CWA jurisdiction, 

waters will be considered traditional 

navigable waters, and thus (a)(1) waters 

under the proposed rule, if: 

• They are subject to section 9 or 10 

of the Rivers and Harbors 

Appropriations Act of 1899; 

• A Federal court has determined that 

the water body is navigable-in-fact 

under Federal law; 

• They are waters currently being 

used for commercial navigation, 

including commercial waterborne 

recreation (for example, boat rentals, 

guided fishing trips, or water ski 

tournaments); 

• They have historically been used 

for commercial navigation, including 

commercial waterborne recreation; or 

• They are susceptible to being used 

in the future for commercial navigation, 

including commercial waterborne 

recreation. Susceptibility for future use 

may be determined by examining a 

number of factors, including the 

physical characteristics and the capacity 

of the water to be used in commercial 

navigation, including commercial 

recreational navigation (for example, 

size, depth, and flow velocity), and the 

likelihood of future commercial 

navigation, including commercial 

waterborne recreation. While a 

traditional navigable water need not be 

capable of supporting navigation at all 

times, the frequency, volume, and 

duration of flow are relevant 

considerations for determining if a 

water body has the physical 

characteristics suitable for navigation. A 

likelihood of future commercial 

navigation, including commercial 

waterborne recreation, can be 

demonstrated by current boating or 

canoe trips for recreation or other 

purposes. A determination that a water 

is susceptible to future commercial 

navigation, including commercial 

waterborne recreation, must be 

supported by evidence. 

This proposal does not affect the 

scope of waters subject to state 

assumption of the section 404 regulatory 

program under section 404(g) of the 

CWA. See CWA section 404(g). The 

scope of waters that are subject to state 

and tribal permitting is a separate 

inquiry and must be based on the 

statutory language in CWA section 404. 

States administer approved CWA 

section 404 programs for ‘‘waters of the 

United States’’ within the state, except 

those waters remaining under Corps 

jurisdiction pursuant to CWA section 

404(g)(1) as identified in a 

Memorandum of Agreement 7 between 

the state and the Corps. 40 CFR 233.14; 

40 CFR 233.70(c)(2); 40 CFR 

233.71(d)(2). Clarification of waters that 

are subject to assumption by states or 

tribes or retention by the Corps could be 

made through a separate process under 

section 404(g). 

C. Interstate Waters 

The existing EPA and Corps 

regulations define ‘‘waters of the United 

States’’ to include interstate waters, 

including interstate wetlands and the 

agencies’ proposal today does not 

change that provision of the regulations. 

Interstate waters would continue to be 

‘‘waters of the United States’’ even if 

they are not navigable for purposes of 

Federal regulation under (a)(1) and do 

not connect to such waters. Moreover, 

because interstate waters are ‘‘waters of 

the United States’’ under the CWA, the 

agencies are proposing to continue to 

include as jurisdictional tributaries to 

interstate waters, waters adjacent to 

interstate waters, waters adjacent to 

tributaries of interstate waters, and 

‘‘other waters’’ that have a significant 

nexus to interstate waters. 

As discussed in more detail in 

Appendix B to this preamble, the 

language of the CWA indicates that 

Congress intended the term ‘‘navigable 

waters’’ to include interstate waters 

without imposing a requirement that 

they be traditional navigable waters 

themselves or be connected to 

traditional navigable waters. The 

precursor statutes to the CWA always 

subjected interstate waters and their 

tributaries to Federal jurisdiction. The 

text of the CWA, specifically CWA 

section 303 that establishes ongoing 

requirements for interstate waters, in 

conjunction with the definition of 

navigable waters, provides clear 

indication of Congress’ intent to protect 

interstate waters that were previously 

subject to Federal regulation. Other 

provisions of the statute provide 

additional textual evidence of the scope 

of the primary jurisdictional term of the 

CWA. 

While congressional intent is clear, 

the agencies also have a longstanding 

regulatory interpretation that interstate 

waters fall within the scope of CWA 

jurisdiction. The agencies’ 

interpretation was promulgated 

contemporaneously with the passage of 

the CWA and is consistent with the 

statutory and legislative history of the 

CWA. Furthermore, the Supreme Court 

has never addressed the CWA’s 

coverage of interstate waters, and it is 

not reasonable to read its decisions in 

SWANCC and Rapanos to question the 

jurisdictional status of interstate waters 

or to impose additional jurisdictional 

requirements on interstate waters. 

It is reasonable to assert jurisdiction 

over tributaries, adjacent wetlands and 

‘‘other waters’’ that have a significant 

nexus to interstate waters consistent 

with the framework established by 

Justice Kennedy in Rapanos for 

establishing jurisdiction over waters 

with a significant nexus to traditional 

navigable waters. Justice Kennedy’s 

standard seeks to ensure that waters 

Congress intended to subject to Federal 

jurisdiction are indeed protected, both 

by recognizing that waters and wetlands 

with a significant nexus to traditional 

navigable waters and interstate waters 

have important beneficial effects on 

those waters, and by recognizing that 

polluting or destroying waters with a 

significant nexus can harm downstream 

jurisdictional waters. As Congress 

intended to protect interstate waters, the 

agencies propose to also protect 

interstate waters by defining ‘‘waters of 

the United States’’ to include tributaries 

to interstate waters, waters adjacent to 

interstate waters, waters adjacent to 

tributaries of interstate waters, and 

‘‘other waters’’ that have a significant 

nexus to interstate waters. For 

additional discussion of the agencies’ 

interpretation of the CWA with respect 


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to interstate waters, see Appendix B to 

this preamble. 

D. Territorial Seas 

The CWA and its existing regulations 

include ‘‘the territorial seas’’ as a ‘‘water 

of the United States.’’ The agencies 

propose to make no changes to that 

provision of the regulation other than to 

move the provision to earlier in the 

regulation. The CWA defines ‘‘navigable 

waters’’ to include the territorial seas at 

section 502(7). The CWA goes on to 

define the ‘‘territorial seas’’ as ‘‘the belt 

of the seas measured from the line of 

ordinary low water along that portion of 

the coast which is in direct contact with 

the open sea and the line marking the 

seaward limit of inland waters, and 

extending seaward a distance of three 

miles.’’ The territorial seas establish the 

seaward limit of ‘‘waters of the United 

States.’’ As the territorial seas are also 

clearly protected by the CWA (they are 

also traditional navigable waters), it is 

reasonable to use for protecting the 

territorial seas Justice Kennedy’s 

significant nexus framework that 

protects traditional navigable waters. 

The proposed rule reflects that. 

E. Impoundments 

The agencies do not propose to make 

any substantive changes to the existing 

regulatory language with respect to 

impoundments of waters otherwise 

defined as ‘waters of the United States’ 

under this definition. The changes 

proposed are clarifying. 

Impoundments are jurisdictional 

because as a legal matter an 

impoundment of a ‘‘water of the United 

States’’ remains a ‘‘water of the United 

States’’ and because scientific literature 

demonstrates that impoundments 

continue to significantly affect the 

chemical, physical, or biological 

integrity of downstream waters 

traditional navigable waters, interstate 

waters, or the territorial seas. The 

Supreme Court has confirmed that 

damming or impounding a ‘‘water of the 

United States’’ does not make the water 

non-jurisdictional. See S. D. Warren Co. 

v. Maine Bd. of Envtl. Prot., 547 U.S. 

370, 379 n.5 (2006) (‘‘[N]or can we agree 

that one can denationalize national 

waters by exerting private control over 

them.’’). Similarly, when presented with 

a tributary to the Snake River which 

flows only about two months per year 

because of an irrigation diversion 

structure installed upstream, the Ninth 

Circuit has opined ‘‘it is doubtful that a 

mere man-made diversion would have 

turned what was part of the waters of 

the United States into something else 

and, thus, eliminated it from national 

concern.’’ U.S. v. Moses, 496 F.3d 984 

(9th Cir. 2007), cert. denied, 554 U.S. 

918 (2008). As a matter of policy and 

law, impoundments do not de-federalize 

a water, even where there is no longer 

flow below the impoundment. Where 

flow continues below the 

impoundment, it is straightforward to 

analyze the stream network, above and 

below the impoundment, for connection 

to downstream traditional navigable 

waters, interstate waters, or the 

territorial seas. 

The agencies also note that an 

impoundment of a water that is not a 

‘‘water of the United States’’ can become 

jurisdictional if, for example, the 

impounded waters become navigable-infact and covered under paragraph (a)(1) 

of the rule. 

The existing agency regulations 

provide that impoundments of ‘‘waters 

of the United States’’ remain ‘‘waters of 

the United States’’ and the agencies do 

not propose any substantive revisions to 

that component of the regulation. In 

addition, tributaries to an impoundment 

of a ‘‘water of the United States’’ are 

‘‘waters of the United States’’ under this 

proposed rule. As a matter of law and 

science, an impoundment does not cut 

off a connection between upstream 

tributaries and a downstream (a)(1) 

through (a)(3) water, so tributaries above 

the impoundment are still considered 

tributary to a downstream (a)(1) through 

(a)(3) water even where the flow of 

water is impeded due to the 

impoundment. Scientific literature, as 

well as the agencies’ scientific and 

technical expertise, and practical 

knowledge confirm that impoundments 

have chemical, physical, and biological 

effects on downstream waters (see 

Appendix A, Scientific Evidence). 

Appendix A discusses the conclusion 

that it is reasonable to maintain 

jurisdiction over impoundments of 

‘‘waters of the United States’’ not only 

as a legal matter, but because 

impoundments do not sever the effects 

the impounded ‘‘waters of the United 

States’’ have on the chemical, physical, 

or biological integrity of (a)(1) through 

(a)(3) waters. 

F. Tributaries 

Under this proposal, the agencies 

provide a definition of ‘‘tributary’’ 

supported by the scientific literature. 

The agencies also propose that all 

waters that meet the proposed definition 

of tributary are ‘‘waters of the United 

States’’ by rule, unless excluded under 

section (b), because tributaries and the 

ecological functions they provide, alone 

or in combination with other tributaries 

in the watershed, significantly affect the 

chemical, physical, and biological 

integrity of traditional navigable waters, 

interstate waters, and the territorial seas. 

With today’s proposed regulation, the 

agencies confirm that these tributary 

waters have a significant nexus to a 

traditional navigable water, interstate 

water, or territorial sea such that they 

are ‘‘waters of the United States’’ 

without the need for a separate, casespecific significant nexus analysis. In 

practice, under this proposal any water 

that meets the definition of tributary 

(and is not excluded under section (b) 

of the proposed rule) is a ‘‘water of the 

United States,’’ and the agencies would 

only need to determine that a water 

meets the definition of ‘‘tributary.’’ See 

Appendix A, Scientific Evidence (Part I, 

Discussion of Major Conclusions 2.A; 

Part II, i); and Appendix B, Legal 

Analysis. 

Tributaries have a significant impact 

on the chemical, physical, and 

biological integrity of waters into which 

they eventually flow—including 

traditional navigable waters, interstate 

waters, and the territorial seas—and 

they have a significant nexus and thus 

are jurisdictional as a category. The 

great majority of tributaries are 

headwater streams, and whether they 

are perennial, intermittent, or 

ephemeral, they play an important role 

in the transport of water, sediments, 

organic matter, nutrients, and organisms 

to downstream environments. 

Tributaries serve to store water, thereby 

reducing flooding, provide 

biogeochemical functions that help 

maintain water quality, trap and 

transport sediments, transport, store and 

modify pollutants, provide habitat for 

plants and animals, and sustain the 

biological productivity of downstream 

rivers, lakes and estuaries. 

1. What is a ‘‘tributary’’ for purposes of 

the proposed regulation? 

The proposed rule defines ‘‘tributary’’ 

as a water physically characterized by 

the presence of a bed and banks and 

ordinary high water mark, as defined at 

33 CFR 328.3(e), which contributes 

flow, either directly or through another 

water, to a water identified in 

paragraphs (a)(1) through (4). In 

addition, wetlands, lakes, and ponds are 

tributaries (even if they lack a bed and 

banks or ordinary high water mark) if 

they contribute flow, either directly or 

through another water to a water 

identified in paragraphs (a)(1) through 

(3). A water that otherwise qualifies as 

a tributary under this definition does 

not lose its status as a tributary if, for 

any length, there are one or more manmade breaks (such as bridges, culverts, 

pipes, or dams), or one or more natural 

breaks (such as wetlands at the head of 


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or along the run of a stream, debris 

piles, boulder fields, or a stream that 

flows underground) so long as a bed and 

banks and an ordinary high water mark 

can be identified upstream of the break. 

A tributary, including wetlands, can be 

a natural, man-altered, or man-made 

water and includes waters such as 

rivers, streams, lakes, ponds, 

impoundments, canals, and ditches not 

excluded in paragraph (b)(3) or (4). 

While the agencies have not defined 

tributary in any previous regulation, this 

proposed definition is consistent with 

long-standing practice and historical 

implementation of CWA programs. It is 

important to note that today’s proposed 

definition also is based on best available 

science and the intent of the CWA. 

To meet this definition, a water need 

not contribute flow directly to an (a)(1) 

through (a)(4) water. As the definition 

makes clear, the water may contribute 

flow directly or may contribute flow to 

another water or waters which 

eventually flow into an (a)(1) through 

(a)(4) water. Essentially, the water must 

be part of a tributary system that drains 

to an (a)(1) through (a)(4) water. Under 

the proposed definition, to be a 

‘‘tributary,’’ in addition to requiring that 

a water contribute flow to a traditional 

navigable water, interstate water or the 

territorial sea, the water must also have 

a bed and banks and ordinary high 

water mark (except where a wetland is 

a tributary), because these features 

generally are physical indicators of 

flow. The agencies identified these 

tributary characteristics as indicative 

that the water is the type of hydrologic 

feature protected under the CWA 

because, for example, of a tributary’s 

ability to transport pollutants to 

downstream traditional navigable 

waters, interstate waters, and the 

territorial seas, and thereby have a 

significant effect on the chemical, 

physical, or biological integrity of a 

water identified in paragraphs (a)(1) 

through (a)(4). 

The flow in the tributary may be 

ephemeral, intermittent or perennial, 

but the tributary must drain, or be part 

of a network of tributaries that drain, 

into an (a)(1) through (a)(4) water under 

today’s proposed rule. When 

considering whether the tributary being 

evaluated eventually flows to an (a)(1) 

through (a)(4) water, the tributary 

connection may be traced using direct 

observation or U.S. Geological Survey 

maps, aerial photography or other 

reliable remote sensing information, or 

other appropriate information. A bed 

and banks and ordinary high water mark 

(OHWM) generally are physical 

indicators of water flow. These physical 

indicators can be created by ephemeral, 

intermittent, and perennial flows. 

The agencies’ proposed definition of 

‘‘tributary’’ includes waters such as 

rivers, streams, lakes, impoundments, 

wetlands, canals, and ditches not 

excluded in section (b) that, either 

directly or through other tributaries, 

convey water to traditional navigable 

waters, interstate waters, or the 

territorial seas. A tributary is a 

longitudinal surface feature that results 

from directional surface water 

movement and sediment dynamics 

demonstrated by the presence of bed 

and banks, bottom and lateral 

boundaries, or other indicators of 

OHWM. The movement of water 

through a tributary can transport 

pollutants to downstream (a)(1) through 

(a)(4) waters, as either chemicals 

dissolved or suspended in the water 

column or adsorbed to sediment 

particles. 

The existing Corps regulations define 

OHWM as the line on the shore 

established by the fluctuations of water 

and indicated by physical 

characteristics such as a clear, natural 

line impressed on the banks, shelving, 

changes in the character of soil, 

destruction of terrestrial vegetation, the 

presence of litter and debris, or other 

appropriate means that consider the 

characteristics of the surrounding areas. 

33 CFR 328.3(e). That definition is not 

changed by today’s proposed rule. In 

many tributaries, the bed is that part of 

the channel below the OHWM, and the 

banks often extend above the OHWM. 

Indicators of an OHWM may vary from 

region to region across the country. 

Under the proposed definition of 

tributary, the upper limit of a tributary 

is established where the channel begins. 

Note that wetlands can be providing 

flow into a tributary at the upper limit 

of the channel and these would also be 

jurisdictional. The OHWM generally 

defines the lateral limits of a water, and 

its absence generally determines 

whether a tributary’s channel or bed and 

banks has ended such that the upper 

limit of the jurisdictional tributary is 

identified. However, a natural or manmade break in bed and banks or OHWM 

does not constitute the upper limit of a 

tributary where bed and banks or 

OHWM can be found farther upstream, 

as discussed below. 

In many tributaries, there are often 

natural or man-made breaks in the 

presence of a bed and banks or ordinary 

high water mark while hydrologic 

connectivity remains. For example, in 

some regions of the country where there 

is a very low gradient, the banks of a 

tributary may be very low or may even 

disappear at times. Also, in many 

intermittent and ephemeral tributaries, 

including dry-land systems in the arid 

and semi-arid west, OHWM indicators 

can be discontinuous within an 

individual tributary due to the 

variability in hydrologic and climatic 

influences. The agencies proposed 

definition of ‘‘tributary’’ addresses these 

circumstances and states that waters 

that meet the definition of tributary 

remain tributaries even if such breaks 

occur. A water that otherwise qualifies 

as a tributary under the proposed 

definition does not lose its status as a 

tributary if, for any length, there are one 

or more man-made breaks (such as 

bridges, culverts, pipes, or dams), or one 

or more natural breaks (such as debris 

piles, boulder fields, or a stream 

segment that flows underground) so 

long as a bed and banks and an ordinary 

high water mark can be identified 

upstream of the break. The presence of 

a bed and banks and an ordinary high 

water mark upstream of the break 

generally demonstrates that the tributary 

continues upstream of the break. 

Waters that meet the definition of 

tributary under the proposed rule are 

jurisdictional even if there is an 

impoundment at some point along the 

connection from the tributary to the 

(a)(1) through (a)(3) water. 

Longstanding agency practice has 

identified tributaries as including 

‘‘natural, man-altered or manmade’’ 

water bodies. Natural, man-altered, and 

manmade tributaries provide many of 

the same functions, especially as 

conduits for the movement of water and 

pollutants to other tributaries or directly 

to traditional navigable waters, 

interstate waters, or the territorial seas. 

The discharge of a pollutant into a 

tributary generally has the same effect 

downstream whether the tributary 

waterway is natural or manmade (see 

further discussion below and Appendix 

A). Given the extensive human 

modification of watercourses and 

hydrologic systems throughout the 

country, it is often difficult to 

distinguish between natural 

watercourses and watercourses that are 

wholly or partly manmade or manaltered. For example, tributaries that 

have been channelized in concrete or 

otherwise have been human-altered, 

may still meet the definition of 

tributaries under the agencies’ proposed 

regulation so long as they still 

contribute flow to an (a)(1) through 

(a)(4) water. The agencies’ proposed 

definition of tributary provides a nonexclusive list of the types of waters, 

natural, man-altered and man-made, 

that may be tributaries: Wetlands, rivers, 

streams, lakes, ponds, impoundments, 

canals, and ditches not excluded in 


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paragraph (b)(3) or (4) of the proposed 

rule. 

Under the agencies’ proposal, when a 

tributary flows through a wetland into 

another tributary (e.g., a run-of-stream 

wetland), losing its OHWM through the 

wetland, it remains a tributary, and the 

wetland itself is considered a tributary. 

Wetlands may contribute flow to a 

stream or river through channelized 

flow or diffuse flow, and sometimes 

both. Wetlands may also serve as water 

sources at the upper limit of headwater 

streams where the channel begins. In 

light of their potential to be important 

contributors of flow to tributaries to 

traditional navigable waters, interstate 

waters, or the territorial seas, the 

agencies propose a definition of 

tributary which includes such wetlands. 

In other instances, wetlands may serve 

as the connection between a tributary 

and another tributary or even a 

traditional navigable water, interstate 

water, or the territorial seas. For 

wetland tributaries, water may flow 

through braided channels that also 

include wetlands or through a run-ofstream wetland that does not have a bed 

and banks and OHWM. 

It is the agencies’ intent that the 

definitions in this proposed rule 

provide as much clarity and regulatory 

certainty as possible. While it is 

important to include wetlands that 

connect upstream and downstream 

portions of a tributary as jurisdictional 

waters because they have a significant 

nexus to downstream (a)(1) through 

(a)(4) waters, the agencies recognize that 

it may add an element of uncertainty to 

the definition of tributary to include 

features as tributaries which do not have 

a bed and bank and OHWM. An 

alternate approach would be to clarify 

that wetlands that connect tributary 

segments are adjacent wetlands, and as 

such are jurisdictional waters of the 

United States under (a)(6). In this 

approach, a tributary would be defined 

as having a bed and bank and OHWM, 

and the upper limit of the tributary 

would be defined by the point where 

these features cease to be identifiable. 

(Note that natural or manmade breaks 

would still not sever jurisdiction if a 

tributary segment with a bed and bank 

and OHWM could be identified 

upstream of the break.) Wetlands would 

not be considered tributaries, but would 

remain jurisdictional as adjacent waters. 

Wetlands that contribute flow, for 

example at the upper reaches of the 

tributary system, would be considered 

adjacent waters. The agencies request 

comment on this alternate approach, as 

well as any other suggestions 

commenters may have on how to clarify 

the definition of tributaries and provide 

a clear explanation of their lateral and 

upstream extent. 

Tidal ditches subject to the ebb and 

flow of the tide are not evaluated as 

tributaries, but are jurisdictional under 

paragraph (a)(1) of the proposed 

regulation as they are under the current 

regulation. 

The agencies are proposing to clearly 

exclude from the definition of ‘‘waters 

of the United States’’ two types of 

ditches that might otherwise be 

evaluated as tributaries: Ditches that are 

excavated wholly in uplands, drain only 

uplands, and have less than perennial 

flow; and ditches that do not contribute 

flow, either directly or through another 

water, to a water identified in 

paragraphs (a)(1) through (4). The 

proposed rule for the first time excludes 

certain ditches by rule rather than 

simply through preamble and guidance. 

Even before the decisions in SWANCC 

and Rapanos, the agencies excluded 

certain ditches from jurisdiction 

because they either are not part of the 

tributary system or because they are 

excavated wholly in uplands, drain only 

uplands, and are dry for much of the 

year, i.e. upland ditches. The agencies 

are proposing to continue this exclusion 

and, to provide improved consistency 

and clarity, further define flow 

characteristics of upland ditches that are 

and are not jurisdictional. The proposed 

rule would exclude from jurisdiction 

upland ditches with less than perennial 

flow. The scientific concept of perennial 

flow is a widely accepted and well 

understood hydrologic characteristic of 

tributaries. Perennial flow means that 

water is present in a tributary year 

round when rainfall is normal or above 

normal. Identifying upland ditches with 

perennial flow is straightforward and 

will provide for consistent, predictable, 

and technically accurate determinations 

at any time of year. The agencies 

specifically seek comment on the 

appropriate flow regime for a ditch 

excavated wholly in uplands and 

draining only uplands to be included in 

the exclusion of paragraph (b)(3). In 

particular, the agencies seek comment 

on whether the flow regime in such 

ditches should be less than intermittent 

flow or whether the flow regime in such 

ditches should be less than perennial 

flow as proposed. 

Only those ditches not excluded by 

the proposed regulation and that meet 

the proposed definition of tributary are 

‘‘waters of the United States.’’ Ditches 

that are excluded from the definition of 

‘‘waters of the United States’’ under 

(b)(3) and (b)(4) cannot be recaptured 

and considered jurisdictional under any 

of the jurisdictional categories in section 

(a) of the proposed rule, such as a ditch 

that crosses a state line. This is true for 

all other features excluded under 

section (b) as well. Ditches not excluded 

under paragraphs (b)(3) and (4) of the 

proposed regulation meet the definition 

of tributary where they have a bed and 

banks and ordinary high water mark and 

they contribute flow directly or 

indirectly through another water to 

(a)(1) through (a)(4) waters. Such 

jurisdictional ditches may include, but 

are not limited to, the following: 

• Natural streams that have been 

altered (e.g., channelized, straightened 

or relocated); 

• ditches that have been excavated in 

‘‘waters of the United States,’’ including 

jurisdictional wetlands; 

• ditches that have perennial flow; 

and 

• ditches that connect two or more 

‘‘waters of the United States.’’ 

In an effort to distinguish ditches that 

are not ‘‘waters of the United States’’ 

from those that are ‘‘waters of the 

United States,’’ the proposal states that 

ditches with less than perennial flow 

that are excavated in uplands, rather 

than in wetlands or other types of 

waters, for their entire length are not 

tributaries and are not ‘‘waters of the 

United States’’ under the proposed rule. 

Ditches that are perennial generally 

have water present year round when 

rainfall is normal or above normal. 

Under this exclusion, water that only 

stands or pools in a ditch is not 

considered perennial flow and, 

therefore, any such upland ditch would 

not be subject to regulation. In addition, 

ditches that do not contribute flow to 

the tributary system of a traditional 

navigable water, interstate water or the 

territorial seas are not ‘‘waters of the 

United States,’’ even if the ditch has 

perennial flow. 

Historical evidence, such as 

photographs, prior delineations, or 

topographic maps, may be used to 

determine whether a water body was 

excavated wholly in uplands and drains 

only uplands, and has less than 

perennial flow. Site characteristics may 

also be present to inform the 

determination of whether the water 

body is a ditch, such as shape, 

sinuosity, flow indications, etc., as 

ditches are often created in a linear 

fashion with little sinuosity and may 

not connect to another ‘‘water of the 

United States.’’ Ditches created by 

altering natural waters would be 

considered ‘‘waters of the United 

States,’’ so long as they contribute flow 

to another jurisdictional water. Ditches 

may have been created for a number of 

purposes, such as irrigation, water 

management or treatment, and roadside 

drains. In order to be excluded, 


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8A discharge of dredged or fill material into an 

existing tributary which converts a ‘‘water of the 

U.S.’’ into a non-jurisdictional water requires 

authorization under section 404 of the CWA. 

however, the ditch must be excavated 

wholly in uplands, drain only uplands, 

and have less than perennial flow. 

Ditches that do not contribute flow, 

either directly or through another water, 

to a water identified in paragraphs (a)(1) 

through (4) are not ‘‘waters of the 

United States.’’ 

2. What is not a tributary for purposes 

of this proposal? 

Waters that do not contribute flow, 

either directly or through another water, 

to a water identified in paragraphs (a)(1) 

through (4) of the proposed regulation 

are not considered jurisdictional as 

tributaries under the CWA. However, 

even if such waters are not ‘‘tributaries,’’ 

they may be jurisdictional under other 

paragraphs of the proposed rule. Note 

that waters specifically listed under the 

proposed section (b), including ditches 

as defined in paragraphs (b)(3) and 

(b)(4), would not be considered ‘‘waters 

of the United States’’ in any case. In 

addition, ephemeral features located on 

agricultural lands that do not possess a 

bed and bank are not tributaries. The 

defined bed and bank no longer exists 

due to past normal farming practices 

such as plowing or discing (see section 

404(f)(1)(A)),8 and these farming 

practices often pre-date the CWA. Such 

farm field features are not tributaries 

even though they may contribute flow 

during some rain events or snowmelt. 

Section J below discusses in more 

detail the agencies’ proposed rule 

excluding specific waters and features 

from the definition of ‘‘waters of the 

United States.’’ Of importance with 

respect to tributaries is the exclusion of 

gullies, rills, non-wetland swales, and 

certain ditches. These features are not 

considered tributaries under this 

proposed rule, even though rills and 

gullies and non-wetland swales (as 

described in Section J), may contribute 

flow to a tributary in systems with steep 

side slopes. 

Non-jurisdictional geographic features 

(e.g., non-wetland swales, ephemeral 

upland ditches) may still serve as a 

confined surface hydrologic connection 

between an adjacent wetland or water 

and a traditional navigable water, 

interstate water or the territorial sea, 

provided there is an actual exchange of 

water between those waters, and the 

water is not lost to deep groundwater 

through infiltration (i.e., transmission 

losses). In addition, these geographic 

features may function as ‘‘point 

sources,’’ such that discharges of 

pollutants to waters through these 

features could be subject to other CWA 

authorities (e.g., CWA section 402 and 

its implementing regulations). 

The agencies request comment on all 

aspects of the proposed definition of 

tributaries and in particular on whether 

and how this definition can be revised 

to provide increased clarity as to the 

distinction between jurisdictional 

tributaries, as defined, and nonjurisdictional features such as gullies, 

rills and non-wetland swales. The 

agencies seek comments on how to 

provide greater regulatory certainty as to 

which specific aquatic features are 

jurisdictional tributaries, and which are 

not. Commenters should explain how 

any suggestions are consistent with the 

Clean Water Act, applicable caselaw, 

and the scientific literature regarding 

connectivity of aquatic features. 

3. Why do the agencies conclude all 

tributaries are ‘‘waters of the United 

States’’? 

Assertion of jurisdiction over 

tributaries as defined in this proposed 

rule is appropriate under Rapanos both 

as a legal matter and as a scientific 

matter based on available science and 

the agencies’ professional judgment and 

field expertise. The agencies conclude 

based on their scientific and technical 

expertise that tributaries, as defined in 

the proposed rule, in a watershed are 

similarly situated and have a significant 

nexus alone or in combination with 

other tributaries because they 

significantly affect the chemical, 

physical, or biological integrity of 

traditional navigable waters, interstate 

waters, or the territorial seas. 

a. Legal Basis for Defining All 

Tributaries as ‘‘Waters of the United 

States’’ 

In Rapanos, both the plurality 

opinion and Justice Kennedy’s opinion 

discussed the Court’s prior opinion in 

Riverside Bayview to begin their 

analysis of the scope of the CWA. 

Justice Scalia stated, ‘‘In Riverside 

Bayview, we stated that the phrase 

[‘waters of the United States’] in the Act 

referred primarily to ‘rivers, streams, 

and other hydrographic features more 

conventionally identifiable as ‘‘waters’’’ 

than the wetlands adjacent to such 

features. 474 U.S., at 131 (emphasis 

added).’’ Rapanos, 547 U.S. at 734. 

Justice Kennedy began, ‘‘As the 

plurality points out, and as Riverside 

Bayview holds, in enacting the Clean 

Water Act Congress intended to regulate 

at least some waters that are not 

navigable in the traditional sense. Ante 

at 12; Riverside Bayview, 474 U.S. at 

133; see also SWANCC, supra, at 167.’’ 

Id at 780. This conclusion is supported 

by ‘‘the evident breadth of congressional 

concern for protection of water quality 

and aquatic ecosystems.’’ Riverside 

Bayview, supra, at 133; see also 

Milwaukee v. Illinois, 451 U.S. 304, 318 

(1981) (describing the Act as ‘‘an allencompassing program of water 

pollution regulation’’). In Rapanos, 

Justice Kennedy established a standard 

for determining whether wetlands 

should be considered to possess the 

requisite nexus in the context of 

assessing whether wetlands are 

jurisdictional: ‘‘if the wetlands, either 

alone or in combination with similarly 

situated [wet]lands in the region, 

significantly affect the chemical, 

physical, and biological integrity of 

other covered waters more readily 

understood as ‘navigable.’ ’’ 547 U.S. at 

780. While Justice Kennedy focused on 

adjacent wetlands in light of the facts of 

the cases before him, it is reasonable to 

utilize the same standard for tributaries. 

As discussed in this preamble, based on 

a detailed examination of the scientific 

literature, the agencies conclude that 

tributaries as they propose to define 

them perform the requisite functions 

identified by Justice Kennedy for them 

to be considered, as a category, to be 

‘‘waters of the United States.’’ Assertion 

of jurisdiction over tributaries with a 

bed and banks and OHWM is also 

consistent with Rapanos because five 

Justices did not reject the current 

regulations that assert jurisdiction over 

non-navigable tributaries of traditional 

navigable waters and interstate waters. 

The agencies analyzed the Report and 

other scientific literature to determine 

whether tributaries to traditional 

navigable waters, interstate waters, or 

the territorial seas have a significant 

nexus to constitute ‘‘waters of the 

United States’’ under the Act such that 

it is reasonable to assert CWA 

jurisdiction over all such tributaries as 

a category by rule. The agencies’ 

analysis of the available scientific 

literature, including the Report, 

demonstrates through an ecological 

rationale that tributaries draining to a 

traditional navigable water, interstate 

water, or the territorial seas have a 

significant nexus to such waters, 

especially because of their ability to 

transport pollutants to such waters that 

would impair their chemical, physical, 

or biological integrity. 

One of the primary purposes and 

functions of the CWA is to prevent the 

discharge of petroleum wastes and other 

chemical wastes, biological and medical 

wastes, sediments, nutrients and all 

other forms of pollutants into the 

‘‘waters of the United States,’’ because 

such pollutants endanger the nation’s 


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public health, drinking water supplies, 

shellfish, fin fish, recreation areas, etc. 

Because the entire tributary system of 

the traditional navigable, interstate 

waters or the territorial seas is 

interconnected, pollutants that are 

dumped into any part of the tributary 

system eventually are washed 

downstream to traditional navigable 

waters, interstate waters, or the 

territorial seas where those pollutants 

endanger public health and the 

environment. 

The CWA regulates and controls 

pollution at its source, in part because 

most pollutants do not remain at the site 

of the discharge, but instead flow and 

are washed downstream through the 

tributary system to endanger drinking 

water supplies, fisheries, and recreation 

areas. These fundamental facts about the 

movement of pollutants and the 

interconnected nature of the tributary 

system demonstrate why all tributaries 

of traditional navigable waters, 

interstate waters, and the territorial seas, 

alone or in combination with other 

tributaries in a watershed have a 

significant nexus with those 

downstream waters. The significant 

nexus relating to pollution transport (or 

prevention of such transport) from all 

tributaries of traditional navigable 

waters, interstate waters, and the 

territorial seas to their downstream 

waters in and of itself justifies the 

assertion of CWA jurisdiction over all 

tributaries by rule. 

b. The Agencies Conclude That 

Tributaries, as Defined in the Proposed 

Rule, Have a Significant Nexus 

The finding of significant nexus is 

based on the chemical, physical, and 

biological interrelationship between a 

water, the tributary network, and 

traditional navigable waters, interstate 

waters, and the territorial seas. Based on 

their scientific and technical expertise, 

the agencies conclude that tributaries, as 

defined in today’s proposed rule, have 

a significant nexus and are 

appropriately identified as jurisdictional 

by rule. Rapanos, 547 U.S. at 781–82 (J. 

Kennedy). (For more discussion, see 

Appendix A). 

(1) Tributaries Significantly Affect the 

Physical Integrity of (a)(1) Through 

(a)(3) Waters 

Physical connections between 

tributaries and traditional navigable 

waters, interstate waters, and the 

territorial seas result from the 

hydrologic transport of numerous 

materials, including water, sediment 

and organic matter (e.g., leaves, wood) 

from tributaries to downstream waters. 

This transport affects the physical 

characteristics of downstream waters. 

Tributaries, even when seasonally dry, 

are the dominant source of water in 

most rivers, rather than direct 

precipitation or groundwater input to 

main stem river segments. 

One of the primary functions of 

tributaries is transporting sediment to 

downstream waters. Tributaries, 

particularly headwaters, shape and 

maintain river channels by 

accumulating and gradually or 

episodically releasing sediment and 

large woody debris into river channels. 

Sediment transport is also provided by 

ephemeral streams. Effects of the 

releases of sediment and large woody 

debris are especially evident at 

tributary-river confluences, where 

discontinuities in flow regime and 

temperature demonstrate physical 

alteration of river structure and function 

by headwater streams. 

Tributaries have vitally important 

effects on the physical integrity of (a)(1) 

through (a)(3) waters, contributing not 

only the majority of the flow in these 

waters but affecting the structure of the 

waters. These effects occur even when 

the tributaries flow infrequently (such 

as ephemeral tributaries) and even when 

the tributaries are significant distances 

from the (a)(1) through (a)(3) water 

(such as some headwater tributaries). 

Tributaries provide flow to downstream 

rivers necessary to support navigation. 

The agencies conclude that the 

tributaries alone or together with other 

tributaries in a watershed have a 

significant effect on the physical 

integrity of downstream waters. 

(2) Tributaries Significantly Affect the 

Chemical Integrity of (a)(1) Through 

(a)(3) Waters 

Tributaries also influence the 

chemical composition of downstream 

waters, through the transport and 

removal of chemical elements and 

compounds, such as nutrients, ions, 

dissolved and particulate organic 

matter, pollutants, and contaminants. 

Ecosystem processes in tributaries 

transform, remove, and transport these 

substances to downstream waters. In 

turn, these chemical compounds can 

influence water quality, sediment 

deposition, nutrient availability, and 

biotic functions in rivers. Because water 

flow is the primary mechanism by 

which chemical substances are 

transported downstream, chemical 

effects are closely related to 

hydrological connectivity. Longdistance movement of contaminants 

provides another line of evidence for 

chemical connectivity between 

tributaries and traditional navigable 

waters, interstate waters, and the 

territorial seas and significantly affects 

these waters. 

Within tributaries, there are processes 

that occur that transform and export 

nutrients and carbon to downstream 

waters, serving important source 

functions that influence the chemical 

integrity of downstream waters. Organic 

carbon, in both dissolved and 

particulate forms, exported from 

tributaries is consumed by downstream 

organisms. The organic carbon that is 

exported downstream thus supports 

biological activity (including 

metabolism) throughout the river 

network. 

Tributaries have important effects on 

the chemical integrity of (a)(1) through 

(a)(3) waters, acting as both sinks and 

sources of chemical substances. They 

provide sink functions by trapping 

chemicals through absorption to 

sediments in the stream substrate (e.g., 

phosphorous adsorption to clay 

particles). They provide source 

functions by transporting chemicals to 

downstream (a)(1) through (a)(3) waters 

as chemicals dissolved in the waters or 

as chemicals attached to suspended 

sediments. Thus the tributaries of a 

watershed, alone or in combination, 

significantly affect the chemical 

integrity of downstream waters. 

(3) Tributaries Significantly Affect the 

Biological Integrity of (a)(1) Through 

(a)(3) Waters 

Tributaries, including intermittent 

and ephemeral streams, are critical in 

the life cycles of many organisms 

capable of moving throughout river 

networks. In fact, many organisms, such 

as anadromous salmon, have complex 

life cycles which involve migration 

through the river network, from 

headwaters to downstream rivers and 

oceans and back, over the course of their 

lives. Anadromous fish spend the 

majority of their life cycles in saltwater, 

but migrate upstream to inland 

freshwater systems in order to spawn 

and reproduce. More generally, in 

addition to providing critical habitat for 

complex life cycle completion, 

tributaries provide refuge from 

predators and adverse physical 

conditions in rivers, and they are 

reservoirs of genetic- and species-level 

diversity. These connections between 

tributaries and (a)(1) through (a)(3) 

waters significantly influence the 

biologic integrity of these waters. 

Tributaries have important effects on 

the biological integrity of (a)(1) through 

(a)(3) waters, contributing materials to 

downstream food networks and 

supporting populations for aquatic 

species, including economically 

important species such as salmon, etc., 


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and other essential habitat needs for 

species that utilize both tributaries and 

downstream (a)(1) through (a)(3) waters. 

These effects occur even when the 

tributaries flow infrequently (such as 

ephemeral tributaries) and even when 

the tributaries are large distances from 

the (a)(1) through (a)(3) water (such as 

some headwater tributaries). When all 

the tributaries in a watershed are 

considered together, these effects are 

significant. 

(4) Small, Intermittent, and Ephemeral 

Tributaries Significantly Affect the 

Chemical, Physical, and Biological 

Integrity of (a)(1) Through (a)(3) Waters 

As discussed above, the agencies 

conclude that tributaries, including 

headwaters, intermittent, and ephemeral 

streams, and especially when all 

tributaries in a watershed are 

considered in combination, have a 

significant nexus to traditional 

navigable waters, interstate waters, or 

the territorial seas based on their 

contribution to the chemical, physical, 

and biological integrity of (a)(1) through 

(a)(3) waters. Tributaries, including 

headwater streams, within a watershed 

draining to a traditional navigable 

water, interstate water, or the territorial 

seas collectively shape the chemical, 

physical, and biological integrity of 

(a)(1) through (a)(3) waters. 

Tributaries that are small, flow 

infrequently, or are a substantial 

distance from the nearest (a)(1) through 

(a)(3) water (e.g., headwater perennial, 

intermittent, and ephemeral tributaries) 

are essential components of the 

tributary network and have important 

effects on the chemical, physical, and 

biological integrity of (a)(1) through 

(a)(3) waters, contributing many of the 

same functions downstream as larger 

streams. When their functional 

contributions to the chemical, physical, 

and biological conditions of 

downstream waters are considered at a 

watershed scale, the scientific evidence 

supports a legal determination that they 

meet the ‘‘significant nexus’’ standard 

articulated by Justice Kennedy in 

Rapanos. 

(5) Tributary Lakes, Ponds, and 

Wetlands Significantly Affect the 

Chemical, Physical, and Biological 

Integrity of (a)(1) Through (a)(3) Waters 

Although the above discussion refers 

primarily to stream tributaries, lake, 

pond and wetland tributaries also have 

the same or similar connections and 

functions that significantly affect (a)(1) 

through (a)(3) waters. Lakes and ponds 

that contribute surface water to 

downstream (a)(1) through (a)(3) waters 

satisfy the agencies’ definition of 

tributary. They may be at the 

headwaters of the tributary network 

(e.g., a lake with no stream inlets that 

has an outlet to the tributary network) 

or located outside of the headwaters, or 

farther downstream from the headwaters 

(e.g., a lake with both a stream inlet and 

a stream outlet to the tributary network). 

Similarly, wetland tributaries are 

wetlands that are located within the 

stream channel itself or that form the 

start of the stream channel, such as 

channel-origin wetlands that are part of 

the headwaters of the tributary network. 

As noted above, while these wetlands 

may function as part of the ‘‘tributary 

network,’’ the agencies are seeking 

comment on whether it would provide 

greater regulatory clarity to exclude 

such wetlands from the definition of 

‘‘tributary’’ because they generally lack 

a defined bed, bank and OHWM. These 

features are well understood by the 

public and agency field staff and have 

traditionally been the defining 

characteristics of tributaries. Rather, 

wetlands in headwaters or connecting 

tributaries would remain jurisdictional 

as adjacent waters under the definition 

of ‘‘adjacent’’ and its supporting terms 

(e.g., neighboring, floodplain, and 

riparian area) in this proposal. 

Tributary lakes and ponds serve many 

important functions that affect the 

chemical, physical, and biological 

conditions downstream. Lakes can store 

floodwaters, sediment, and nutrients, as 

these materials have the opportunity to 

settle out, at least temporarily, as water 

moves through the lake downstream. 

Lakes, as with other tributaries, can also 

contribute flow, nutrients, sediment, 

and other materials downstream. 

(6) Man-Made or Man-Altered 

Tributaries Significantly Affect the 

Chemical, Physical, and Biological 

Integrity of (a)(1) Through (a)(3) Waters 

This proposal expressly states that a 

tributary, including wetlands, can be a 

natural, man-altered, or man-made 

water body and includes waters such as 

rivers, streams, lakes, impoundments, 

canals, and ditches that meet the 

definition of tributary and are not 

excluded from the definition of ‘‘waters 

of the United States’’ by paragraphs 

(b)(3) and (b)(4) of the proposed rule. 

The agencies’ proposed rule clarifies 

that man-made and man-altered 

tributaries are ‘‘waters of the United 

States’’ because man-made and manaltered tributaries perform many of the 

same functions as natural tributaries, 

especially the conveyance of water that 

carries nutrients, pollutants, and other 

substances to traditional navigable 

waters, interstate waters, or the 

territorial seas. Man-made and manaltered tributaries also provide corridors 

for movement of organisms between 

headwaters and traditional navigable 

waters, interstate waters, or the 

territorial seas. The significant nexus 

between a tributary and a traditional 

navigable water, interstate water, or the 

territorial seas is not broken where the 

tributary flows through a culvert or 

other structure. The scientific literature 

recognizes that features that convey 

water, whether they are natural, manmade, or man-altered, provide the 

connectivity between streams and 

downstream rivers. 

Tributary ditches and other manmade or man-altered waters, if they 

meet the definition of ‘‘tributary,’’ have 

a significant nexus to (a)(1) through 

(a)(3) waters due to their effects on the 

chemical, physical, or biological 

integrity of those downstream waters. 

As described above, tributaries of all 

flow regimes have a significant nexus to 

downstream (a)(1) through (a)(3) waters. 

Due to the often straightened and 

channelized nature of ditches, these 

tributaries quickly move water 

downstream to (a)(1) through (a)(3) 

waters. Ditches and canals, like other 

tributaries, export sediment, nutrients, 

and other materials downstream. Due to 

their often channelized nature, ditches 

are very effective at transporting water 

and these materials, including nitrogen, 

downstream. It is the agencies’ position 

that ditches that meet the definition of 

tributary (which does not include 

ditches excluded under paragraphs 

(b)(3) and (b)(4)) provide the same 

chemical, physical, and biological 

functions as other water bodies defined 

as tributaries under the proposed rule. 

G. Adjacent Waters 

The agencies propose to revise the 

existing jurisdictional category of 

‘‘adjacent wetlands,’’ which currently 

limits consideration to only wetlands, to 

include ‘‘adjacent waters.’’ The 

proposed ‘‘adjacent waters’’ category 

would replace ‘‘adjacent wetlands’’ and 

would include wetlands and other 

waterbodies that meet the proposed 

definition of adjacent, including 

‘‘neighboring.’’ To be jurisdictional, it 

would be necessary to determine that a 

wetland or other waterbody meets the 

definition of ‘‘adjacent’’ water under 

proposed paragraph (a)(6). Adjacent 

waters are integrally linked to the 

chemical, physical, or biological 

functions of the (a)(1) through (a)(5) 

waterbodies to which they are adjacent. 

Waters adjacent to (a)(1) through (a)(3) 

waters have a significant nexus to those 

(a)(1) through (a)(3) waters. Waters 

adjacent to impoundments, (a)(4) and 

tributaries, (a)(5), are integrally linked to 


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the chemical, physical, or biological 

functions of the impoundments or 

tributaries and, through those waters, 

are integrally linked to the chemical, 

physical or biological functions of 

traditional navigable waters, interstate 

waters or the territorial seas. As such, 

where waterbodies are adjacent to (a)(4) 

or (a)(5) waters, they also have a 

significant nexus to (a)(1) through (a)(3) 

waters. See Appendix A, Scientific 

Evidence (Part I, Discussion of Major 

Conclusions 2.B–C; Part II, ii) and 

Appendix B, Legal Analysis. 

The proposed rule proposes to change 

‘‘adjacent wetlands’’ to ‘‘adjacent 

waters’’ so that water bodies such as 

ponds and oxbow lakes, as well as 

wetlands, adjacent to jurisdictional 

waters are ‘‘waters of the United States’’ 

by rule. Second, the proposed rule adds 

a definition of the term ‘‘neighboring,’’ 

a term which appears in the existing 

definition of ‘‘adjacent.’’ The agencies 

propose a definition for ‘‘neighboring’’ 

to identify those adjacent waters that the 

agencies concluded have a significant 

nexus to (a)(1) through (a)(3) waters. To 

bring greater clarity to the meaning of 

‘‘neighboring,’’ the proposed rule adds 

scientifically-based definitions for the 

terms ‘‘riparian area’’ and ‘‘floodplain’’ 

to define the lateral reach of the term 

‘‘neighboring.’’ Under the proposed 

rule, all waters, including wetlands, 

adjacent to a water identified in 

paragraphs (a)(1) through (5); would be 

‘‘waters of the United States.’’ The term 

adjacent means bordering, contiguous or 

neighboring. Waters, including 

wetlands, separated from other waters of 

the United States by man-made dikes or 

barriers, natural river berms, beach 

dunes and the like are ‘‘adjacent 

waters.’’ The term neighboring, for 

purposes of the term ‘‘adjacent,’’ 

includes waters located within the 

riparian area or floodplain of a water 

identified in paragraphs (a)(1) through 

(5), or waters with a shallow subsurface 

hydrologic connection or confined 

surface hydrologic connection to such a 

jurisdictional water. The term riparian 

area means an area bordering a water 

where surface or subsurface hydrology 

directly influence the ecological 

processes and plant and animal 

community structure in that area. 

Riparian areas are transitional areas 

between aquatic and terrestrial 

ecosystems that influence the exchange 

of energy and materials between those 

ecosystems. Finally, the term floodplain 

means an area bordering inland or 

coastal waters that was formed by 

sediment deposition from such water 

under present climatic conditions and is 

inundated during periods of moderate to 

high water flows. 

1. What are ‘‘adjacent waters’’ under the 

proposed rule? 

‘‘Adjacent waters’’ are wetlands, 

ponds, lakes and similar water bodies 

that provide similar functions which 

have a significant nexus to traditional 

navigable waters, interstate waters, and 

the territorial seas. These include waters 

and wetlands that are adjacent to 

traditional navigable waters, interstate 

waters, and the territorial seas as well as 

waters and wetlands adjacent to other 

jurisdictional waters such as tributaries 

and impoundments. The inclusion of 

adjacent waters in this category is 

supported by the Report, the collective 

body of scientific literature, the 

agencies’ growing body of scientific and 

technical knowledge and practical 

expertise addressing the connectivity 

and ecological interactions of these 

waters on (a)(1) through (a)(3) waters, 

and by the determination made in this 

rulemaking that all adjacent waters in a 

watershed have a significant nexus with 

their traditional navigable waters, 

interstate waters or the territorial seas. 

Under the existing rule, only wetlands 

adjacent to ‘‘waters of the United 

States’’ are defined as ‘‘waters of the 

United States.’’ As noted in San 

Francisco Baykeeper v. Cargill Salt, 481 

F.3d 700 (9th Cir. 2007), this provision 

of the agencies’ regulations only defines 

adjacent wetlands, not adjacent ponds, 

as ‘‘waters of the United States.’’ Prior 

to SWANCC, adjacent non-wetland 

waters were often jurisdictional under 

the ‘‘other waters,’’ or ‘‘(a)(3)’’ provision 

of the existing regulations which the 

agencies are proposing to eliminate. 

Waters, including wetlands, that meet 

the proposed definition of adjacency, 

including the new proposed definition 

of neighboring, have a significant nexus 

to (a)(1) through (a)(3) waters, and this 

proposed rule would include all 

adjacent waters, including wetlands, as 

‘‘waters of the United States’’ by rule. 

The existing definition of ‘‘adjacent’’ 

would be generally retained under 

today’s proposal, with a clarification 

with respect to an existing provision 

addressing wetlands adjacent to other 

wetlands. The proposed rule states that 

the term adjacent means bordering, 

contiguous or neighboring. Waters, 

including wetlands, separated from 

other waters of the United States by 

man-made dikes or barriers, natural 

river berms, beach dunes and the like 

are ‘‘adjacent waters.’’ Within the 

definition of ‘‘adjacent,’’ the terms 

bordering and contiguous are well 

understood, and for continuity and 

clarity the agencies would continue to 

interpret and implement those terms 

consistent with existing policy and 

practice. 

The proposed rule also contains for 

the first time a definition of the term 

‘‘neighboring.’’ The term ‘‘neighboring’’ 

has generally been interpreted broadly 

in practice. The agencies provide a 

regulatory definition of ‘‘neighboring’’ 

that captures those waters that in 

practice the agencies have identified as 

having a significant effect on the 

chemical, physical, and biological 

integrity of traditional navigable waters, 

interstate waters, or the territorial seas. 

‘‘Neighboring’’ is defined as including 

waters located within the riparian area 

or floodplain of a water identified in 

paragraphs (a)(1) through (5), or waters 

with a confined surface or shallow 

subsurface hydrologic connection to 

such a jurisdictional water. 

The terms ‘‘riparian area’’ and 

‘‘floodplain’’ are also defined to further 

clarify how the agencies interpret the 

term ‘‘neighboring.’’ Those new terms 

are found at paragraphs (c)(1) through 

(c)(4) of the proposed rule. The agencies 

emphasize that these terms help to 

identify waters, including wetlands, that 

may be ‘‘adjacent’’ and would, therefore, 

be ‘‘waters of the United States’’ under 

this proposed rule. Absolutely no 

uplands located in ‘‘riparian areas’’ and 

‘‘floodplains’’ can ever be ‘‘waters of the 

United States’’ subject to jurisdiction of 

the CWA. 

Most waters, including wetlands, that 

are neighboring to a water body are 

found within its riparian zone or 

floodplain. However, there are some 

neighboring waters that might be 

located outside of the riparian zone or 

floodplain, such as wetlands 

immediately next to a highly incised 

and manipulated stream that no longer 

has a riparian area or a floodplain. 

Waters, including wetlands, determined 

to have a shallow subsurface hydrologic 

connection or confined surface 

hydrologic connection to an (a)(1) 

through (a)(5) water would also be 

‘‘waters of the United States’’ by rule as 

adjacent waters falling within the 

definition of ‘‘neighboring.’’ 

In circumstances where a particular 

water body is outside of the floodplain 

and riparian area of a tributary, but is 

connected by a shallow subsurface 

hydrologic connection or confined 

surface hydrologic connection with 

such tributary, the agencies will also 

assess the distance between the water 

body and tributary in determining 

whether or not the water body is 

adjacent. ‘‘Adjacent’’ as defined in the 

agencies’ regulations has always 

included an element of reasonable 

proximity. See Riverside Bayview, 474 at 


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133–34 (‘‘Following the lead of the 

Environmental Protection Agency, see 

38 FR 10834 (1973), the Corps has 

determined that wetlands adjacent to 

navigable waters do as a general matter 

play a key role in protecting and 

enhancing water quality: . . . ‘For this 

reason, the landward limit of Federal 

jurisdiction under Section 404 must 

include wetlands that are in reasonable 

proximity to other waters of the United 

States, as these wetlands are part of this 

aquatic system.’ ’’ quoting 42 FR 37128, 

July 19, 1977). Therefore, the 

determination of whether a particular 

water meets the definition of 

‘‘neighboring’’ because the water is 

connected by a shallow subsurface or 

confined surface hydrologic connection 

is made in the context of the terms 

‘‘neighboring’’ and ‘‘adjacent’’ as used 

in the regulation. 

The element of reasonable proximity 

is informed by the scientific literature, 

supplemented by agency practice, 

which leads to a recognition of the role 

of hydrologic connections in supporting 

a significant chemical, physical, and 

biological relationship between water 

bodies, but this relationship can be 

reduced as the distance between water 

bodies increases. The agencies recognize 

that in specific circumstances, the 

distance between water bodies may be 

sufficiently far that even the presence of 

a hydrologic connection may not 

support an adjacency determination. 

While the agencies’ best professional 

judgment has always been a factor in 

determining whether a particular 

wetland is ‘‘adjacent’’ under the existing 

definition, the agencies recognize that 

this may result in some uncertainty as 

to whether a particular water connected 

through confined surface or shallow 

subsurface hydrology is an ‘‘adjacent’’ 

water. The agencies therefore request 

comment on whether there are other 

reasonable options for providing clarity 

for jurisdiction over waters with these 

types of connections. 

Options could include asserting 

jurisdiction over all waters connected 

through a shallow subsurface hydrologic 

connection or confined surface 

hydrologic connection regardless of 

distance; asserting jurisdiction over 

adjacent waters only if they are located 

in the floodplain or riparian zone of a 

jurisdictional water; considering only 

confined surface connections but not 

shallow subsurface connections for 

purposes of determining adjacency; or 

establishing specific geographic limits 

for using shallow subsurface or confined 

surface hydrological connections as a 

basis for determining adjacency, 

including, for example, distance 

limitations based on ratios compared to 

the bank-to-bank width of the water to 

which the water is adjacent. The 

agencies note that under the proposed 

rule any waters not fitting within (a)(1) 

through (a)(6) categories would instead 

be treated as ‘‘other waters.’’ 

Both confined surface and shallow 

subsurface connections are forms of 

direct hydrologic connections between 

adjacent waters and (a)(1) through (a)(5) 

waters. For purposes of this rule, 

confined surface connections consist of 

permanent, intermittent or ephemeral 

surface connections through directional 

flowpaths, such as (but not limited to) 

swales, gullies, rills, and ditches. In 

some cases, these connections will be a 

result of ‘‘fill and spill’’ hydrology. A 

directional flowpath is a path where 

water flows repeatedly from the wetland 

or open water to the nearby ‘‘water of 

the United States’’ that at times contains 

water originating in the adjacent 

wetland or open water as opposed to 

just directly from precipitation. 

For the purposes of this rule, ‘‘fill and 

spill’’ describes situations where 

wetlands or open waters fill to capacity 

during intense precipitation events or 

high cumulative precipitation over time 

and then spill to the downstream 

jurisdictional water. Report at 5–62 

(citing T.C. Winter and D.O. Rosenberry, 

‘‘Hydrology of Prairie Pothole Wetlands 

during Drought and Deluge: A 17-year 

Study of the Cottonwood Lake Wetland 

Complex in North Dakota in the 

Perspective of Longer Term Measured 

and Proxy Hydrological Records,’’ 

Climatic Change 40:189–209 (1998); 

S.G. Leibowitz, and K.C. Vining, 

‘‘Temporal connectivity in a prairie 

pothole complex,’’ Wetlands 23:13–25 

(2003)). Water connected through such 

flows originates from the adjacent 

wetland or open water, travels to the 

downstream jurisdictional water, and is 

connected to those downstream waters 

by swales or other directional flowpaths 

on the surface. Surface hydrologic 

connections via physical features or 

discrete features described above allow 

for confined, direct hydrologic flows 

between an adjacent water and the (a)(1) 

through (a)(5) water that it neighbors. 

A shallow subsurface hydrologic 

connection is lateral water flow through 

a shallow subsurface layer, such as can 

be found, for example, in steeply 

sloping forested areas with shallow 

soils, or in soils with a restrictive layer 

that impedes the vertical flow of water, 

or in karst systems, especially karst 

pans. K.J. Devito, et al., ‘‘GroundwaterSurface Water Interactions in Headwater 

Forested Wetlands of the Canadian 

Shield,’’ Journal of Hydrology 181:127– 

47 (1996); M.A. O’Driscoll, and R.R. 

Parizek, ‘‘The Hydrologic Catchment 

Area of a Chain of Karst Wetlands in 

Central Pennsylvania, USA,’’ Wetlands 

23:171–79 (2003); B.J. Cook, and F.R. 

Hauer, ‘‘Effects of Hydrologic 

Connectivity on Water Chemistry, Soils, 

and Vegetation Structure and Function 

in an Intermontane Depressional 

Wetland Landscape,’’ Wetlands 27:719– 

38 (2007). 

A shallow subsurface connection also 

exists, for example, when the adjacent 

water and neighboring (a)(1) through 

(a)(5) water are in contact with the same 

shallow aquifer. Shallow subsurface 

connections may be found both within 

the ordinary root zone and below the 

ordinary root zone (below 12 inches), 

where other wetland delineation factors 

may not be present. A combination of 

physical factors may reflect the presence 

of a shallow subsurface connection, 

including (but not limited to) stream 

hydrograph (for example, when the 

hydrograph indicates an increase in 

flow in an area where no tributaries are 

entering the stream), soil surveys (for 

example, exhibiting indicators of high 

transmissivity over an impermeable 

layer), and information indicating the 

water table in the stream is lower than 

in the shallow subsurface. 

Shallow subsurface connections are 

distinct from deeper groundwater 

connections, which do not satisfy the 

requirement for adjacency, in that the 

former exhibit a direct connection to the 

water found on the surface in wetlands 

and open waters. Water does not have 

to be continuously present in the 

confined surface or shallow subsurface 

hydrologic connection and the flow 

between the adjacent water and the 

jurisdictional water may move in one or 

both directions. While they may provide 

the connection establishing jurisdiction, 

these shallow subsurface flows are not 

‘‘waters of the United States.’’ 

For waters outside of the riparian area 

or floodplain, confined surface 

hydrologic connections (as described 

above) are the only types of surface 

hydrologic connections that satisfy the 

requirements for adjacency. Waters 

outside of the riparian area or floodplain 

that lack a shallow subsurface 

hydrologic connection or a confined 

surface hydrologic connection would be 

analyzed as ‘‘other waters’’ under 

paragraph (a)(7) of the proposed rule. 

Application of the terms ‘‘riparian 

area,’’ ‘‘floodplain,’’ and ‘‘hydrologic 

connection’’ would be based in part on 

best professional judgment and 

experience applied to the definitions 

contained in this rule. The new 

definitions of riparian area and 

floodplain are designed to provide 

greater consistency, clarity, and 

certainty in determining the 


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circumstances under which a particular 

water meets the definition of the term 

adjacent. The addition of these two 

terms to the definition of ‘‘neighboring’’ 

is based on the scientific literature and 

agencies’ knowledge of and expertise on 

river systems, which shows that water 

bodies such as wetlands, ponds, and 

oxbow lakes located within the riparian 

areas and floodplains of (a)(1) through 

(a)(5) waters generally have substantial 

hydrologic and ecologic connections 

with the waters that they neighbor. 

These proposed definitions are 

adapted from scientific definitions using 

the concepts that are most relevant and 

useful in the context of the CWA. Use 

of the floodplain in characterizing the 

term ‘‘neighboring’’ is intended to 

provide greater clarity and predictability 

in the determination of when waters are 

adjacent. The scientific literature clearly 

demonstrates the enhanced hydrologic 

connectivity that is present between a 

tributary and waters within the 

floodplain of that tributary. There is, 

however, variability in the size of the 

floodplain, which is dependent on 

factors such as the flooding frequency 

being considered, size of the tributary, 

and topography. As a general matter, 

large tributaries in low gradient 

topography will generally have large 

floodplains (e.g., the lower Mississippi 

Delta) whereas small headwater streams 

located in steep gradients will have the 

smallest floodplains. It may thus be 

appropriate for the agencies to consider 

a floodplain associated with a lower 

frequency flood when determining 

adjacency for a smaller stream, and to 

consider a floodplain associated with a 

higher frequency flood when 

determining adjacency for a larger 

stream. When determining whether a 

water is located in a floodplain, the 

agencies will use best professional 

judgment to determine which flood 

interval to use (for example, 10 to 20 

year flood interval zone). The agencies 

request comment on whether the rule 

text should provide greater specificity 

with regard to how the agencies will 

determine if a water is located in the 

floodplain of a jurisdictional water. 

As noted above, the agencies retain 

the general existing definition of 

adjacency and have never interpreted 

the term to include wetlands that are a 

great distance from a jurisdictional 

water. The agencies intend to similarly 

interpret the new definition of 

‘‘neighboring.’’ This new definition is 

designed to provide greater clarity by 

identifying specific areas and 

characteristics for jurisdictional 

adjacent waters, but the agencies request 

comment for additional clarification. 

Commenters should support where 

possible from scientific literature any 

suggestions for additional clarification 

of current explicit limits on adjacency, 

such as a specific distance or a specific 

floodplain interval. 

The agencies seek comment on 

specific options for establishing 

additional precision in the definition of 

‘‘neighboring’’ through: explicit 

language in the definition that waters 

connected by shallow subsurface 

hydrologic or confined surface 

hydrologic connections to an (a)(1) 

through (a)(5) water must be 

geographically proximate to the adjacent 

water; circumstances under which 

waters outside the floodplain or riparian 

zone are jurisdictional if they are 

reasonably proximate; support for or 

against placing geographic limits on 

what waters outside the floodplain or 

riparian zone are jurisdictional; 

determining that only waters within the 

floodplain, only waters within the 

riparian area, or only waters within the 

floodplain and riparian area (but not 

waters outside these areas with a 

shallow subsurface or confined surface 

hydrologic connection) are adjacent; 

identification of particular floodplain 

intervals within which waters would be 

considered adjacent; and any other 

scientifically valid criteria, guidelines or 

parameters that would increase clarity 

with respect to neighboring waters. 

Finally, the agencies are also 

proposing to delete the parenthetical 

from the existing ‘‘adjacent wetlands’’ 

regulatory provision The phrase ‘‘other 

than waters that are themselves 

wetlands’’ was intended to preclude 

asserting CWA jurisdiction over 

wetlands that were simply adjacent to 

another wetland (such as an ‘‘isolated’’ 

wetland, as opposed to a wetland 

adjacent to a tributary). However, in 

practice some wetlands that were 

indeed adjacent to a tributary were 

found to not meet the definition of 

‘‘adjacent’’ simply because another 

adjacent wetland was located between 

the adjacent wetland and the tributary. 

With this proposed change, the agencies 

intend to ensure that all waters that 

meet the proposed definition of 

‘‘adjacent’’ are ‘‘waters of the United 

States,’’ regardless of whether or not 

another adjacent water is located 

between those waters and the tributary. 

If, for example, one wetland is in the 

riparian area of a ‘‘tributary’’ as defined 

in today’s proposed rule, and a different 

wetland is in the floodplain of that 

tributary, both wetlands would meet the 

definition of ‘‘adjacent’’ and be ‘‘waters 

of the United States,’’ even if the 

riparian wetland is located between the 

floodplain wetland and the tributary. 

Waters located near an adjacent water 

but which are not themselves 

(independently) adjacent to an (a)(1) 

through (a)(5) water would, under the 

proposed rule, not be regulated under 

(a)(6). However, waters, including 

wetlands, that are adjacent to a wetland 

that meets the definition of a tributary 

would be considered adjacent waters. 

2. Why do the agencies conclude that 

adjacent waters are ‘‘waters of the 

United States?’’ 

a. Legal Basis for Defining All Adjacent 

Waters as ‘‘Waters of the United States’’ 

For those wetlands adjacent to 

traditional navigable waters, Justice 

Kennedy stated in Rapanos that the 

agencies’ existing regulation ‘‘rests upon 

a reasonable inference of ecologic 

interconnection, and the assertion of 

jurisdiction for those wetlands is 

sustainable under the Act by showing 

adjacency alone.’’ 547 U.S. at 780. For 

all other adjacent waters, including 

adjacent wetlands, Justice Kennedy has 

provided a framework for establishing 

categories of waters which are per se 

‘‘waters of the United States.’’ First, he 

provided that wetlands are 

jurisdictional if they ‘‘either alone or in 

combination with similarly situated 

[wet]lands in the region, significantly 

affect the chemical, physical, and 

biological integrity of other covered 

waters more readily understood as 

‘navigable.’ ’’ 547 U.S. at 780. While the 

issue was not before the Supreme Court, 

it is reasonable to also assess whether 

non-wetland waters have a significant 

nexus, as Justice Kennedy’s opinion 

makes clear that a significant nexus is 

the touchstone for CWA jurisdiction. 

Justice Kennedy also stated that the 

agencies could through regulation or 

adjudication identify categories of 

waters that ‘‘are likely, in the majority 

of cases, to perform important functions 

for an aquatic system incorporating 

navigable waters.’’ 547 U.S. at 780–81. 

Adjacent waters as defined in today’s 

proposed rule, alone or in combination 

with other adjacent waters in a 

watershed that drain to a traditional 

navigable water, interstate water or the 

territorial seas, significantly affect the 

chemical, physical, or biological 

integrity of those waters. Waters that are 

adjacent to (a)(1) through (a)(5) waters, 

including wetlands, oxbow lakes and 

adjacent ponds, are integral parts of 

stream networks because of their 

ecological functions and how they 

interact with each other, and with 

downstream traditional navigable 

waters, interstate waters, or the 

territorial seas. In other words, 

tributaries and their adjacent waters, 

and the traditional navigable waters, 


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interstate waters, and territorial seas to 

which those waters flow, are an 

integrated ecological system, and 

discharges of pollutants, including 

discharges of dredged or fill material, 

into these components of that ecological 

system, must be regulated under the 

CWA to restore and maintain the 

chemical, physical, and biological 

integrity of these waters. 

The agencies’ proposed rule is 

consistent with the statute, the Supreme 

Court’s decisions, the best available 

science, and scientific and technical 

expertise. See both Appendices A and 

B. 

b. Adjacent Waters Under This 

Proposed Rule Have a Significant Nexus 

to (a)(1) Through (a)(3) Waters 

The agencies’ proposal to determine 

‘‘adjacent waters’’ to be jurisdictional by 

rule is supported by the substantial 

chemical, physical, and biological 

relationship between adjacent waters, 

alone or in combination with similarly 

situated waters, and (a)(1) through (a)(5) 

waters. Adjacent wetlands and other 

adjacent waters such as ponds and 

oxbow lakes perform important 

functions for the nearby streams and 

lakes, and these functions are significant 

for the chemical, physical, and 

biological integrity of adjacent and 

downstream waters. See Appendix A. 

One reason why the agencies propose 

in this rulemaking that all adjacent 

waters have a significant nexus with 

their traditional navigable waters, 

interstate waters, or the territorial seas 

is closely related to a primary reason 

(explained above) why all tributaries of 

navigable and interstate waters have a 

significant nexus with those waters. 

That is, all adjacent waters should be 

jurisdictional by rule because the 

discharge of many pollutants (such as 

nutrients, petroleum wastes and other 

toxic pollutants) into adjacent waters 

often flow into and thereby pollute the 

traditional navigable waters, interstate 

waters, and the territorial seas. 

Based on science and agency 

expertise, the agencies conclude that 

adjacent waters, as defined in the 

proposed rule, ‘‘are likely, in the 

majority of cases, to perform important 

functions for an aquatic system 

incorporating navigable waters.’’ 

Rapanos, 547 U.S. at 781–82. The 

agencies identified the characteristics of 

adjacent waters that as a class have a 

significant nexus to (a)(1) through (a)(3) 

waters: They are waters that are 

bordering to or are contiguous with 

(a)(1) through (a)(5) waters, including 

wetlands; they are waters that lie within 

the riparian area or floodplain of (a)(1) 

through (a)(5) waters; or they are waters 

that have a shallow subsurface or 

confined surface hydrologic connection 

with (a)(1) through (a)(5) waters. These 

characteristics ensure that the adjacent 

waters are part of ‘‘an aquatic system 

incorporating navigable waters,’’ 547 

U.S. at 781–82; and that they perform 

important functions to maintain the 

chemical, physical, or biological 

integrity of (a)(1) through (a)(3) waters. 

In showing chemical, physical, and 

biological connections between adjacent 

waters and other jurisdictional waters, 

adjacent waters, including wetlands, 

may be separated by land or other 

features not regulated under the CWA, 

but those intervening uplands do not 

eliminate or impede the functional 

interactions between (a)(1) through 

(a)(5) waters and the waters, including 

wetlands, that are adjacent to them. For 

instance, two waters may be separated 

by upland but be connected through 

surface or shallow subsurface 

connections with water and chemicals 

readily exchanging between them. 

Similarly, uplands separating two 

waters may not act as a barrier to 

species that rely on and that regularly 

move between the two waters. 

Therefore, the proposed rule reflects an 

understanding that adjacent waters 

affect the chemical, physical, and 

biological integrity of waters to which 

they are adjacent and to (a)(1) through 

(a)(3) waters even where the two waters 

may be separated by features that are 

not jurisdictional, such as uplands, 

berms, roads, levees, and similar 

features. The presence of these features 

does not extinguish jurisdiction, a 

conclusion contained in the agencies’ 

existing regulation at 33 CFR 328.3(c). 

(1) Riparian and Floodplain Waters 

Significantly Affect the Chemical, 

Physical, and Biological Integrity of 

(a)(1) Through (a)(3) Waters 

Riparian and floodplain waters, 

including wetlands, that are adjacent to 

(a)(1) through (a)(3) waters play an 

integral role in maintaining the 

chemical, physical, and biological 

integrity of those waters. In addition, 

riparian and floodplain waters, 

including wetlands, that are adjacent to 

(a)(4) and (a)(5) waters provide an 

important role in maintaining the 

chemical, physical, and biological 

integrity of traditional navigable waters, 

interstate waters, and the territorial seas. 

Among the ways in which riparian and 

floodplain waters, including wetlands, 

that are adjacent to (a)(4) and (a)(5) 

waters significantly affect the chemical, 

physical, or biological integrity of 

traditional navigable waters, interstate 

waters, and the territorial seas is by 

significantly affecting the chemical, 

physical, and biological integrity of the 

(a)(4) and (a)(5) waters to which they are 

adjacent, and those waters in turn 

significantly affect the chemical, 

physical, or biological integrity of 

traditional navigable waters, interstate 

waters, and the territorial seas. 

(2) Waters, Including Wetlands, 

Determined To Have a Confined Surface 

or a Shallow Subsurface Hydrologic 

Connection Significantly Affect the 

Chemical, Physical, and Biological 

Integrity of (a)(1) Through (a)(3) Waters. 

The proposed rule includes as 

adjacent those waters that are 

‘‘neighboring’’ because they possess a 

shallow subsurface or confined surface 

hydrologic connection to a 

jurisdictional water, and therefore can 

exchange water, along with chemicals 

and organisms within that water, with 

an (a)(1) through (a)(5) water, and 

subsequently have a significant effect, 

particularly in combination with other 

adjacent waters in the watershed, on the 

chemical, physical, or biological 

integrity of a downstream traditional 

navigable water, interstate water, and 

the territorial seas. 

Confined surface connections that 

provide a discrete pathway for water to 

be exchanged between the potentially 

adjacent wetland or water and an (a)(1) 

through (a)(5) water present the clearest 

evidence of a hydrologic connection. 

Shallow subsurface connections are also 

relevant, yet are more difficult to 

identify and document. Evidence shows 

that waters, including wetlands, located 

outside of the riparian area or 

floodplain, but which still have a 

shallow subsurface or confined surface 

hydrologic connection to an (a)(1) 

through (a)(5) water, will have a 

significant nexus to downstream (a)(1) 

through (a)(3) waters. Note that nothing 

under the proposed rule would cause 

the shallow subsurface connections 

themselves to become jurisdictional. 

Examples of confined surface water 

hydrologic connections that 

demonstrate adjacency are swales, 

gullies, and rills. The frequency, 

duration, and volume of flow associated 

with these confined surface connections 

can vary greatly depending largely on 

factors such as precipitation, snowmelt, 

landforms, soil types, and water table 

elevation. It is the presence of this 

hydrologic connection which provides 

the opportunity for neighboring waters 

to influence the chemical, physical, or 

biological integrity of (a)(1) through 

(a)(5) waters. 

In circumstances where a particular 

water is outside of the floodplain and 

riparian area of a jurisdictional water, a 

connection can be established by 

confined surface or shallow subsurface 


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hydrology that makes the water 

neighboring, and thus adjacent. The 

scientific literature recognizes the role 

of hydrologic connections in supporting 

a substantial chemical, physical, or 

biological relationship between water 

bodies, but this relationship can be 

reduced as the distance between water 

bodies increases because of various 

factors, such as soil characteristics, 

geology, climate, precipitation patterns, 

etc. The distance between water bodies 

may be sufficiently great that even the 

presence of an apparent hydrologic 

connection may not support an 

adjacency determination. The greater 

the distance, the less likelihood that 

there is an actual shallow subsurface or 

confined surface hydrologic connection, 

because of the greater potential for the 

water to infiltrate the soil to deeper 

groundwater, or for transmission losses 

in any gully or swale (for example) that 

may appear to be hydrologic 

connections. Within a watershed, 

wetlands and open waters that are 

closer to tributaries will have a higher 

probability of being hydrologically 

connected and of being determined 

adjacent than more distant waters, 

assuming that conditions governing type 

and quantity of flows (e.g., slope, soil, 

and aquifer permeability) are similar. 

Report at 5–2. A determination of 

adjacency based on shallow subsurface 

or confined surface hydrologic 

connection outside the riparian area or 

floodplain requires clear 

documentation. 

H. ‘‘Other Waters’’ 

The ‘‘other waters’’ paragraph of the 

proposed rule is at (a)(7). To be clear, 

these ‘‘other waters’’ are not 

jurisdictional as a single category; 

rather, as the proposed rule language 

states, ‘‘other waters’’ are jurisdictional 

provided that they are found, on a casespecific basis, to have a significant 

nexus to an (a)(1) through (a)(3) water. 

Thus, the introductory phrase ‘‘on a 

case-specific basis’’ is designed to signal 

clearly that this provision of the 

definition of ‘‘waters of the United 

States’’ does not mean ‘‘other waters’’ 

are ‘‘waters of the United States’’ by 

definition in the same way as those 

defined as jurisdictional in proposed 

paragraphs (a)(1) through (a)(6). 

‘‘Other waters’’ will be evaluated 

either individually, or as a group of 

waters where they are determined to be 

similarly situated in the region. Waters 

are similarly situated where they 

perform similar functions and are 

located sufficiently close together or 

when they are sufficiently close to a 

jurisdictional water. How these ‘‘other 

waters’’ are aggregated for a casespecific significant nexus analysis 

depends on the functions they perform 

and their spatial arrangement within the 

‘‘region’’ or watershed. For other waters 

that perform similar functions, their 

landscape position within the 

watershed (i.e., the ‘‘region’’) relative to 

each other or to a jurisdictional water is 

generally the determinative factor for 

aggregating waters in a significant nexus 

analysis, which will focus on the degree 

to which the functions provided by 

those ‘‘other waters’’ affect the 

chemical, physical, or biological 

integrity of (a)(1) through (a)(3) waters 

and whether such effects are significant. 

See Appendix A, Scientific Evidence 

(Part I, Discussion of Major Conclusions 

2.C; Part II, iii) and Appendix B, Legal 

Analysis. 

Significant nexus is proposed to be 

defined to mean that a water, including 

wetlands, either alone or in combination 

with other similarly situated waters in 

the region (i.e., the watershed that 

drains to the nearest water identified in 

paragraphs (a)(1) through (a)(3) of this 

section), significantly affects the 

chemical, physical, or biological 

integrity of a water identified in 

paragraphs (a)(1) through (a)(3) of this 

section. For an effect to be significant, 

it must be more than speculative or 

insubstantial. Other waters, including 

wetlands, are similarly situated when 

they perform similar functions and are 

located sufficiently close together or 

sufficiently close to a ’’water of the 

United States’’ so that they can be 

evaluated as a single landscape unit 

with regard to their effect on the 

chemical, physical, or biological 

integrity of a water identified in 

paragraphs (a)(1) through (a)(3). 

Other waters with a significant nexus 

can be found to be jurisdictional on a 

case-specific basis where these waters 

do not fit within the definition of 

another of the proposed categories of 

‘‘waters of the United States’’ under 

paragraphs (a)(1) through (a)(6) and are 

not excluded from the definition of 

‘‘waters of the United States’’ under 

proposed section (b). 

A significant nexus analysis may be 

based on a particular water alone or 

based on the effect that the water has in 

combination with other similarly 

situated waters in the region. Where 

effects will be analyzed in combination, 

the agencies will aggregate those effects. 

The agencies propose to interpret the 

‘‘region’’ within which similarly 

situated waters would be aggregated as 

the watershed that drains to the nearest 

traditional navigable water, interstate 

water, or the territorial seas. 

For purposes of analyzing whether an 

‘‘other water’’ has a significant nexus, 

the agencies are proposing that ‘‘other 

waters’’ are similarly situated if they 

perform similar functions and they are 

either (1) located sufficiently close 

together so that they can be evaluated as 

a single landscape unit with regard to 

their effect on the chemical, physical, or 

biological integrity of a water identified 

in paragraphs (a)(1) through (a)(3), or (2) 

located sufficiently close to a ‘‘water of 

the United States’’ for such an 

evaluation of their effect. These criteria 

are explained in a subsequent section. 

Consistent with Justice Kennedy’s 

opinion in Rapanos, the agencies 

propose today and are soliciting 

comment on establishing a case-specific 

analysis of whether ‘‘other waters,’’ 

including wetlands, that do not meet the 

criteria for any of the proposed 

jurisdictional categories in (a)(1) 

through (a)(6) and are not proposed to 

be excluded by rule under section (b), 

are susceptible to a case-specific 

analysis of whether they alone, or in 

combination with other similarly 

situated waters, have a significant nexus 

to a traditional navigable water, an 

interstate water, or the territorial seas, 

and therefore are ‘‘waters of the United 

States.’’ 

1. Significant Nexus Analysis for ‘‘Other 

Waters’’ 

a. ‘‘Other Waters’’ 

‘‘Other waters’’ are those waters, 

including wetlands, that are subject to a 

case-specific significant nexus 

determination, and do not meet the 

criteria of any of the categories of waters 

in (a)(1) through (a)(6), and also are not 

one of the waters and features excluded 

from the definition of ‘‘waters of the 

United States’’ in section (b). In the 

existing regulation, there is a nonexclusive list of the types of ‘‘other 

waters’’ which may be found to be 

‘‘waters of the United States.’’ The 

agencies do not propose to repromulgate this list of ‘‘other waters’’ 

because it is unnecessary and has led to 

confusion where it has been incorrectly 

read as an exclusive list. 

Of additional concern was that the 

existing descriptive list of types of 

‘‘other waters’’ includes some waters 

that would be jurisdictional under one 

of the proposed categories of ‘‘waters of 

the United States’’ that would be 

jurisdictional by rule, such as tributary 

streams. The agencies want to avoid 

questions of whether an intermittent 

stream that meets the definition of 

tributary also needs a separate 

significant nexus analysis. Under the 

proposed rule, that tributary stream 

does not require the significant nexus 

analysis. Removing the list of water 


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types does not imply that any of the 

waters listed in the existing regulation 

are never jurisdictional under the 

proposed rule. When one of the waters 

on the current enumerated list does not 

fall under a proposed category for 

jurisdiction (for example, adjacent 

waters under (a)(6) or tributaries under 

(a)(5)), those waters would be 

jurisdictional if found to have a 

significant nexus under proposed 

paragraph (a)(7) on a case-specific 

basis. 

b. Significant Nexus 

The agencies recognize that Supreme 

Court decisions in SWANCC and 

Rapanos placed limits on the scope of 

‘‘other waters’’ that may be determined 

to be jurisdictional. Therefore, the 

agencies’ proposal today provides that 

waters not determined to be 

jurisdictional as a category are 

jurisdictional only if they are 

determined on a case-specific basis to 

have a significant nexus to a traditional 

navigable water, an interstate water, or 

the territorial seas. The agencies also 

request comment and information below 

on how the science could support other 

approaches that could provide greater 

regulatory certainty regarding the 

jurisdictional status of ‘‘other waters’’, 

including expanding the list of waters 

jurisdictional by rule, expanding the list 

of waters not jurisdictional by rule, and 

narrowing the ‘‘other waters’’ subject to 

a case-specific analysis, including 

eliminating the case-specific analysis 

where the science does not support it. 

The agencies will review the 

administrative record, including 

comments received, the scientific 

literature, and the final Report, in 

determining how to address ‘‘other 

waters’’ in the final rule. 

Justice Kennedy explained the 

SWANCC decision in his concurring 

opinion in Rapanos: ‘‘In Solid Waste 

Agency of Northern Cook Cty. v. Army 

Corps of Engineers, 531 U.S. 159 (2001) 

(SWANCC), the Court held, under the 

circumstances presented there, that to 

constitute ‘navigable waters’ under the 

Act, a water or wetland must possess a 

‘significant nexus’ to waters that are or 

were navigable in fact or that could 

reasonably be so made.’’ 547 U.S. at 759. 

The agencies interpret the significant 

nexus standard to apply to the ‘‘other 

waters’’ portion of the existing 

regulation since the Court in SWANCC 

was considering the validity of the 

Corps’ assertion of jurisdiction over 

ponds and mudflats under (a)(3) of the 

Corps’ regulations (33 CFR 328.3). 

To comport with the SWANCC and 

Rapanos decisions, the agencies 

propose to delete the requirement that 

an ‘‘other water’’ be one the use, 

degradation or destruction of which 

could affect interstate or foreign 

commerce and to replace it with the 

requirement that the ‘‘other water’’ meet 

Justice Kennedy’s significant nexus 

standard. The current regulations assert 

jurisdiction more broadly than what is 

proposed today. With this proposed 

regulation, the agencies would limit 

jurisdiction over ‘‘other waters’’ to only 

those that are determined on a casespecific basis to have a significant nexus 

to an (a)(1) through (a)(3) water. 

For purposes of assessing whether a 

particular water is a ‘‘water of the 

United States’’ because it, alone or in 

combination with other similarly 

situated waters, has a significant nexus 

to an (a)(1) through (a)(3) water, the 

agencies are proposing to define 

‘‘significant nexus’’ plus each of the key 

elements used in the definition of 

‘‘significant nexus.’’ 

i. In the Region 

The agencies propose to interpret the 

phrase ‘‘in the region’’ to mean the 

watershed that drains to the nearest 

traditional navigable water, interstate 

water, or the territorial seas through a 

single point of entry. That concept is 

reflected in the definition of ‘‘significant 

nexus’’ at (c)(7). Since Justice Kennedy 

did not define the ‘‘region,’’ the agencies 

determined that because the movement 

of water from watershed drainage basins 

to river networks and lakes shapes the 

development and function of these 

systems in a way that is critical to their 

long term health, the watershed is a 

reasonable and technically appropriate 

extent on which to identify waters that 

together may have an effect on the 

chemical, physical, or biological 

integrity of a particular (a)(1), through 

(a)(3) water. See Appendix A, Scientific 

Evidence (Part I, Background; Part II, 4, 

iii, A). 

The agencies choose to use the single 

point of entry watershed as the 

appropriate scale for the region. A single 

point of entry watershed is the drainage 

basin within whose boundaries all 

precipitation ultimately flows to the 

nearest single traditional navigable 

water, interstate water, or the territorial 

sea. There will likely be other 

traditional navigable waters, interstate 

waters, and ultimately the territorial 

seas further downstream from the 

‘‘nearest’’ such water, and these further 

downstream waters would likely have 

larger watersheds, but the agencies 

determined that a reasonable 

interpretation of ‘‘in the region’’ is the 

watershed that drains to the nearest (i.e. 

first downstream) such water. Any 

nexus between other waters and an 

(a)(1) through (a)(3) water will be 

strongest with this nearest such water, 

and its drainage area is likely to be of 

a size commonly understood as a 

‘‘region.’’ 

The agencies generally use available 

mapping tools that are based on the 

National Hydrography Dataset (NHD) to 

demarcate boundaries of the single 

point of entry watershed. This point of 

entry approach identifies a group of 

waters that flow to a single location and 

represents the scientifically appropriate 

sized area for conducting a significant 

nexus evaluation in most cases. In the 

arid West, the agencies recognize there 

may be situations where the single point 

of entry watershed is very large, and it 

may be resource intensive to demarcate 

watershed boundaries and all relevant 

waters in the watershed. Under those 

circumstances, for practical 

administrative purposes the agencies 

could use the NHD mapping tool to 

demarcate catchments surrounding the 

water to be evaluated that, in 

combination, are roughly the size of the 

typical nearby 10-digit hydrologic unit 

code (HUC–10) watershed. This 

combination of catchments would be 

used for conducting a significant nexus 

evaluation. Such an approach can help 

resolve some practical concerns about 

using available mapping tools on very 

large single point of entry watersheds in 

the arid West. 

The watershed includes all lands, 

streams, wetlands, lakes, and other 

waters within its boundaries. Only 

waters within the watershed that meet 

standards set out in (a)(1) through (a)(7) 

of the proposed rule would be 

considered ‘‘waters of the United 

States.’’ In light of the scientific 

literature, the longstanding approach of 

the agencies to implementation of the 

CWA, and the statutory goals 

underpinning Justice Kennedy’s 

significant nexus framework, the 

watershed draining to the nearest (a)(1) 

through (a)(3) water is the appropriate 

‘‘region’’ for a significant nexus 

analysis. 

ii. Similarly Situated 

Justice Kennedy provided guidance to 

the agencies that establishing a 

significant nexus requires examining 

whether a water ‘‘alone or in 

combination with similarly situated 

[wet]lands in the region, significantly 

affect[s] the chemical, physical, and 

biological integrity of other covered 

waters more readily understood as 

‘navigable.’ ’’ 547 U.S. at 780. The 

proposed rule adopts the concept of the 

‘‘alone or in combination with similarly 

situated waters’’ test. 


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The proposed regulation in the 

definition of ‘‘significant nexus’’ at 

(c)(7) clarifies that other waters, 

including wetlands, are similarly 

situated when they perform similar 

functions and are located sufficiently 

close together or sufficiently close to a 

‘water of the United States’ so that they 

can be evaluated as a single landscape 

unit with regard to their effect on the 

chemical, physical, or biological 

integrity of a water identified in 

paragraphs (a)(1) through (a)(3) This 

combination of functionality and 

proximity to each other or to a ‘‘water 

of the United States’’ meets the standard 

provided by Justice Kennedy. 

Examining both functionality and 

proximity also limits the ‘‘other waters’’ 

that can be aggregated for purposes of 

determining jurisdiction. 

It is appropriate to analyze the 

chemical, physical, or biological effects 

‘‘other waters’’ perform individually or 

together with all similarly situated 

‘‘other waters’’ in the region under 

Justice Kennedy’ s standard. Today, the 

agencies are proposing to identify 

factors to apply in the determination of 

when ‘‘other waters’’ should be 

considered either individually or as a 

single landscape unit for purposes of a 

significant nexus analysis. The agencies 

propose that ‘‘similarly situated’’ 

requires an evaluation of either a single 

water or group of waters (i.e., a single 

landscape unit) in the region that can 

reasonably be expected to function 

together in their effect on the chemical, 

physical, or biological integrity of 

downstream traditional navigable 

waters, interstate waters, or the 

territorial seas. 

In addition, the agencies propose that 

‘‘other waters’’ located close to a 

jurisdictional water are more likely to 

influence such waters and therefore, to 

affect the integrity of downstream (a)(1) 

through (a)(3) waters. These ‘‘other 

waters,’’ which do not meet the 

proposed definition of adjacent waters, 

may be assessed together when 

determining on a case-specific basis 

whether a significant nexus exists, 

because of their similar functions and 

similar location in the landscape. 

Similarly situated waters may be 

identified as sufficiently close together 

for purposes of this paragraph of the 

proposed regulation when they are 

within a contiguous area of land with 

relatively homogeneous soils, vegetation 

and landform (e.g., plain, mountain, 

valley, etc.). As a general matter, it 

would be inappropriate, for example, to 

consider ‘‘other waters’’ as ‘‘similarly 

situated’’ if these ‘‘other waters’’ are 

located in different landforms, have 

different elevation profiles, or have 

different soil and vegetation 

characteristics, unless the ‘‘other 

waters’’ perform similar functions and 

are located sufficiently close to a ‘‘water 

of the United States’’ to allow them to 

consistently and collectively function 

together to affect an (a)(1) through (a)(3) 

water. In determining whether other 

waters are sufficiently close to each 

other or to a water of the United States, 

the agencies would also consider 

hydrologic connectivity to each other or 

a jurisdictional water. 

In determining whether groups of 

other waters perform ‘‘similar 

functions’’ the agencies would also 

consider functions such as habitat, 

water storage, sediment retention, and 

pollution sequestration. These and other 

relevant considerations would be used 

by the agencies to document the 

hydrologic, geomorphic and ecological 

characteristics and circumstances of the 

waters. Examples include: 

documentation of chemical, physical, 

and biological interactions of the 

similarly situated ‘‘other waters;’’ aerial 

photography; topographical or terrain 

maps and information; other available 

geographic information systems (GIS) 

data; National Wetlands Inventory 

Maps; and state and local information. 

The evaluation would use any available 

site information and pertinent field 

observations where available, relevant 

scientific studies or data, or other 

relevant jurisdictional determinations 

that have been completed in the region. 

Under the proposed rule, the agencies 

would assess the combined effects of 

similarly situated ‘‘other waters’’ in the 

region on the chemical, physical, or 

biological integrity of (a)(1) through 

(a)(3) waters in conducting a significant 

nexus analysis. The factors identified 

above would be used by the agencies in 

determining ‘‘other waters’’ in the 

region that are similarly situated and 

should, therefore, be considered 

together in conducting a significant 

nexus analysis. The agencies recognize 

that consideration of these factors will 

often limit aggregation of ‘‘other waters’’ 

for purposes of assessing significant 

nexus or will require that ‘‘other 

waters’’ be considered individually with 

no aggregation. 

iii. Significant Nexus 

The agencies propose to define the 

term ‘‘significant nexus’’ consistent with 

language in SWANCC and Rapanos. The 

proposed definition recognizes that not 

all waters have this requisite connection 

to traditional navigable waters, 

interstate waters, or the territorial seas 

sufficient to be determined 

jurisdictional. Justice Kennedy was 

clear that waters with a significant 

nexus must significantly affect the 

chemical, physical, or biological 

integrity of a downstream navigable 

water and that the requisite nexus must 

be more than ‘‘speculative or 

insubstantial,’’ Rapanos, at 780, and the 

agencies propose to define significant 

nexus in precisely those terms. 

It is important to note that in 

Rapanos, Justice Kennedy did not 

conclude that the wetlands adjacent to 

tributaries in the cases before the Court 

were not ‘‘waters of the United States.’’ 

Rather, Justice Kennedy concluded that 

the proper inquiry to determine their 

jurisdictional status—whether or not the 

wetlands had a ‘‘significant nexus’’— 

had not been made by the Corps or the 

courts below. Justice Kennedy stated 

that in both the consolidated cases 

before the Court the record contained 

the types of evidence relevant to the 

determination of a significant nexus 

according to the principles he 

identified. Justice Kennedy stated 

‘‘[m]uch the same evidence should 

permit the establishment of a significant 

nexus with navigable-in-fact waters, 

particularly if supplemented by further 

evidence about the significance of the 

tributaries to which the wetlands are 

connected.’’ Id. Thus, Justice Kennedy 

concluded that ‘‘the end result in these 

cases and many others to be considered 

by the Corps may be the same as that 

suggested by the dissent, namely, that 

the Corps’ assertion of jurisdiction is 

valid.’’ See Appendix B, Legal Analysis. 

The agencies will determine whether 

the water they are evaluating, in 

combination with other similarly 

situated waters in the region, has a 

significant nexus to the nearest 

traditional navigable water, interstate 

water or the territorial seas. Functions of 

waters that might demonstrate a 

significant nexus include sediment 

trapping, nutrient recycling, pollutant 

trapping and filtering, retention or 

attenuation of flood waters, runoff 

storage, export of organic matter, export 

of food resources, and provision of 

aquatic habitat. A hydrologic 

connection is not necessary to establish 

a significant nexus, because, as Justice 

Kennedy stated, in some cases the lack 

of a hydrologic connection would be a 

sign of the water’s function in 

relationship to the traditional navigable 

water, interstate water or the territorial 

seas. These functional relationships 

include retention of flood waters or 

pollutants that would otherwise flow 

downstream to the traditional navigable 

water, interstate water or the territorial 

seas. See 547 U.S. at 775 (citations 

omitted) (J. Kennedy) (‘‘it may be the 

absence of an interchange of waters 

prior to the dredge and fill activity that 


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22214 Federal Register / Vol. 79, No. 76 / Monday, April 21, 2014 / Proposed Rules 

makes protection of the wetlands 

critical to the statutory scheme’’). For 

example, a report that reviewed the 

results of multiple scientific studies 

concluded that depressional wetlands 

lacking a surface outlet functioned 

together to significantly reduce or 

attenuate flooding. Report at 5–26 

(citing A. Bullock and M. Acreman, 

‘‘The Role of Wetlands in the 

Hydrological Cycle,’’ Hydrology and 

Earth System Sciences 7:358–389 

(2003)). 

When evaluating an ‘‘other water’’ 

individually or cumulatively for the 

presence of a significant nexus to an 

(a)(1) through (a)(3) water, there are a 

variety of factors that can be considered 

that will influence the chemical, 

physical, or biological connections the 

‘‘other water’’ has with the downstream 

(a)(1) through (a)(3) water. The 

likelihood of a significant connection is 

greater with increasing size and 

decreasing distance from the identified 

(a)(1) through (a)(3) water, as well as 

with increased density of the ‘‘other 

waters’’ for ‘‘other waters’’ that can be 

considered in combination with 

similarly situated waters. 

Evidence of chemical connectivity 

and the effect on waters can be found by 

identifying: Whether the properties of 

the water in question are similar or 

dissimilar to an identified (a)(1) through 

(a)(3) water; signs of retention, release, 

or transformation of nutrients or 

pollutants; and the effect of landscape 

position on the strength of the 

connection to the nearest ‘‘water of the 

United States,’’ and through it to an 

(a)(1) through (a)(3) water. In addition, 

relevant factors influencing chemical 

connectivity include hydrologic 

connectivity (see physical factors, 

below), surrounding land use and land 

cover, the landscape setting, and 

deposition of chemical constituents (e.g. 

acidic deposition). 

Evidence of physical connectivity and 

the effect on (a)(1) through (a)(3) waters 

can be found by identifying evidence of 

physical connections, such as flood 

water or sediment retention (flood 

prevention). Presence of indicators of 

hydrologic connections between the 

other water and jurisdictional water are 

also indictors of a physical connection. 

Factors influencing physical 

connectivity include rain intensity, 

duration of rain events or wet season, 

soil permeability, and distance of 

hydrologic connection between the 

‘‘other water’’ and the (a)(1) through 

(a)(3) water, depth from surface to water 

table, and any preferential flowpaths. 

Evidence of biological connectivity 

and the effect on waters can be found by 

identifying: resident aquatic or semiaquatic species present in the ‘‘other 

water’’ and the tributary system (e.g., 

amphibians, aquatic and semi-aquatic 

reptiles, aquatic birds); whether those 

species show life-cycle dependency on 

the identified aquatic resources 

(foraging, feeding, nesting, breeding, 

spawning, use as a nursery area, etc.); 

and whether there is reason to expect 

presence or dispersal around the ‘‘other 

water,’’ and if so whether such dispersal 

extends to the tributary system or 

beyond or from the tributary system to 

the ‘‘other water.’’ Factors influencing 

biological connectivity include species’ 

life history traits, species’ behavioral 

traits, dispersal range, population size, 

timing of dispersal, distance between 

‘‘other water’’ and an (a)(1) through 

(a)(3) water, the presence of habitat 

corridors or barriers, and the number, 

area, and spatial distribution of habitats. 

Non-aquatic species or species such as 

non-resident migratory birds that are not 

demonstrating a life cycle dependency 

on the identified aquatic resources are 

not evidence of biological connectivity 

for purposes of this rule. 

When making a jurisdictional 

determination for an ‘‘other water,’’ the 

administrative record will include 

available information supporting the 

determination. In addition to location 

and other descriptive information 

regarding the water at issue, the record 

will include a clear explanation of the 

rationale for the jurisdictional 

conclusion and a description of the 

information used to determine whether 

the ‘‘other water’’ has a significant 

nexus. Information relevant to a finding 

that an ‘‘other water’’ alone or in 

combination with similarly situated 

‘‘other waters’’ in the region can come 

from many sources. Such information 

need not always be specific to the water 

whose jurisdictional status is being 

evaluated. Regional and national studies 

of the same type of water or similarly 

situated waters can help to inform a 

significant nexus analysis as long as 

they are applicable to the water being 

evaluated. Information derived from 

field observation is not required in cases 

where a ‘‘desktop’’ analysis can provide 

sufficient information to make the 

requisite findings. However, for more 

complex or difficult jurisdictional 

determinations, it may be helpful to 

supplement such information with field 

observation. 

The agencies solicit comment 

regarding this approach to ‘‘other 

waters,’’ recognizing that a case-specific 

analysis of significant nexus is resourceintensive for the regulating agencies and 

the regulated community alike. In 

addition, the agencies solicit comment 

on additional scientific research and 

data that might further inform decisions 

about ‘‘other waters.’’ In particular the 

agencies solicit information about 

whether current scientific research and 

data regarding particular types of waters 

are sufficient to support the inclusion of 

subcategories of types of ‘‘other waters,’’ 

either alone or in combination with 

similarly situated waters, that can 

appropriately be identified as always 

lacking or always having a significant 

nexus. 

iv. Additional Request for Public 

Comment on ‘‘Other Waters’’ 

As stated above, significant goals of 

the agencies in developing this 

proposed rule are to provide greater 

clarity, certainty, and predictability to 

the public as to what waters are and are 

not subject to the jurisdiction of the 

CWA. The agencies will achieve these 

goals consistent with the CWA, as 

interpreted by the Supreme Court, and 

as supported by the best available 

science. The agencies also will fulfill 

their responsibility to the CWA’s 

objectives and policies to protect water 

quality, public health, and the 

environment. 

The agencies acknowledge that there 

may be more than one way to determine 

which waters are jurisdictional as 

‘‘other waters.’’ This proposal is for a 

case-specific analysis of whether ‘‘other 

waters,’’ including wetlands, alone, or 

in combination with other similarly 

situated waters located in the same 

region, have a significant nexus to a 

traditional navigable water, interstate 

water, or the territorial seas. The 

agencies make this proposal based on an 

analysis of the current state of the 

science available to them. In this 

proposal, the agencies continue to 

solicit additional science (peer-reviewed 

whenever possible) that could lead to 

greater clarity, certainty, and 

predictability of which waters are and 

are not within the jurisdiction of the 

CWA. 

To best meet their goals and 

responsibilities, the agencies solicit 

comment and information on the state 

of the science, and its relation to the 

CWA and the caselaw, to determine if 

there are opportunities to provide 

greater clarity, certainty, and 

predictability for establishing 

jurisdiction over ‘‘other waters.’’ This 

includes the possibility of determining 

that additional waters should be 

jurisdictional by rule such as in 

paragraphs (a)(1) through (a)(6), and the 

possibility that additional waters should 

be excluded from jurisdiction by rule 

such as in section (b). The agencies’ 

decision on how best to address 

jurisdiction over ‘‘other waters’’ in the 


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final rule will be informed by the final 

version of the Report and other available 

scientific information. 

The agencies request public comment 

on whether these alternative approaches 

present options for determining the 

jurisdictional status of ‘‘other waters’’ 

that could rely less, or not at all, on 

case-specific analysis of whether waters 

are similarly situated for conducting a 

significant nexus analysis. Possible 

alternative options to the case-specific 

determination in the ‘‘other waters’’ 

proposal are described below. The 

agencies might adopt any combination 

of today’s ‘‘other waters’’ proposal and 

the alternative options for the final rule, 

after considering public comment and 

the evolving scientific literature on 

connectivity of waters. 

The agencies solicit comment on how 

the agencies propose to find ‘‘other 

waters’’ to be similarly situated in this 

proposed rule, whether other methods 

of identifying similarly situated ‘‘other 

waters’’ would be reasonable, and 

whether no ‘‘other waters’’ should be 

determined to be similarly situated. In 

each instance, the comments should 

address how the actions of the agencies 

would be consistent with the science, 

including any science not currently 

before the agencies, the CWA, and the 

caselaw. 

The agencies considered multiple 

approaches and options for how best to 

address whether ‘‘other waters’’ were 

jurisdictional under the CWA. In 

addition to the case-specific analysis in 

the proposal, the agencies seek 

comment on the following alternatives: 

1. Determine by rule that ‘‘other 

waters’’ are similarly situated in certain 

areas of the country. 

The case-specific analysis in the 

proposed rule approaches the question 

of what ‘‘other waters’’ are similarly 

situated for purposes of aggregation in 

the same manner throughout the U.S. 

The agencies could determine by rule 

that ‘‘other waters’’ are similarly 

situated in only certain areas of the 

country, and not in other areas. Under 

this option, the agencies would identify 

ecological regions (ecoregions) which 

contain ‘‘other waters’’ that are 

‘‘similarly situated’’ as provided in the 

proposed rule. Where waters are 

determined to be similarly situated, 

those waters are aggregated for 

evaluation of whether they have a 

significant nexus to a traditional 

navigable water, interstate water, or the 

territorial seas. The agencies expect that 

determining all ‘‘other waters’’ within 

an ecoregion to be similarly situated 

would result in these ‘‘other waters’’ 

being determined to have a significant 

nexus and being found jurisdictional. 

Waters not located in these identified 

ecoregions or other specified areas 

would be determined to not be similarly 

situated and their effects would not be 

aggregated for purposes of a significant 

nexus determination. The result of not 

finding waters to be similarly situated 

would most likely be a finding of no 

significant nexus and no jurisdiction. 

The agencies particularly seek comment 

on whether the science supports 

differing approaches with respect to 

which ‘‘other waters’’ are similarly 

situated in certain areas of the U.S based 

on distinguishing factors in those areas. 

The agencies also request comment on 

factors that could lead ‘‘other waters’’ to 

be aggregated in some areas but 

analyzed individually in other areas for 

purposes of informing a case-specific 

significant nexus analysis. The agencies 

request comment on whether some 

resource types are more or less likely to 

be similarly situated than others, and if 

there are ways to identify regions within 

which aggregation of ‘‘other waters’’ 

would be routinely applied rather than 

a case-specific determination. The 

agencies also request comment about 

whether ‘‘other waters’’ that are not 

found in identifiable mapped regions 

should be analyzed individually on a 

case-specific basis for a significant 

nexus, aggregated in some other way for 

a significant nexus analysis, or 

categorically excluded from jurisdiction. 

An ecoregion is an area within the 

United States that includes generally 

similar ecosystems and that has similar 

types, qualities, and quantities of 

environmental resources. (J.M. Omernik, 

‘‘Perspectives on the Nature and 

Definition of Ecological Regions,’’ 

Environmental Management 

34(Supplement 1):S27–S38 (2004)). 

Ecoregions cover relatively large areas of 

land or water, and contain 

characteristic, geographically distinct 

assemblages of natural communities and 

species. The biodiversity of flora, fauna 

and ecosystems that characterize an 

ecoregion tends to be distinct from that 

of other ecoregions. (Id.) 

Level III ecoregions are the second 

most detailed level of ecoregions 

nationally, with 105 Level III ecoregions 

in the conterminous United States, and 

have been refined over the years in 

several state-level projects conducted in 

collaboration with the EPA and other 

Federal and State agencies. U.S. 

Environmental Protection Agency, 

‘‘Level III Ecoregions of the Continental 

United States,’’ map scale 1:7,500,000 

(Corvallis, OR: U.S. EPA—National 

Health and Environmental Effects 

Research Laboratory, 2013), available at 

http://www.epa.gov/wed/pages/

ecoregions/level_iii_iv.htm. For this 

reason, the agencies consider Level III 

ecoregions to be the most appropriate 

level for analysis. The ‘‘other waters’’ in 

these ecoregions are within a contiguous 

area of land with relatively 

homogeneous soils, vegetation and 

landform (e.g., plain, mountain, valley, 

etc.), and generally provide similar 

functions to the downstream traditional 

navigable waters, interstate waters, or 

the territorial seas. A possible list of 

Level III ecoregions where waters are 

similarly situated and aggregation could 

be used include: 

1. Coast Range 

4. Cascades 

6. Central California Foothills and 

Coastal Mountains 

7. Central California Valley 

8. Southern California Mountains 

9. Eastern Cascades Slopes and Foothills 

10. Columbia Plateau 

27. Central Great Plains 

34. Western Gulf Coastal Plain 

42. Northwestern Glaciated Plains 

44. Nebraska Sand Hills 

46. Northern Glaciated Plains 

47. Western Corn Belt Plains 

48. Lake Agassiz Plain 

50. Northern Lakes and Forests 

51. North Central Hardwood Forests 

59. Northeastern Coastal Zone 

63. Middle Atlantic Coastal Plain 

65. Southeastern Plains 

75. Southern Coastal Plain 

78. Klamath Mountains/California High 

North Coast Range 

81. Sonoran Basin and Range 

83. Eastern Great Lakes Lowlands 

84. Atlantic Coastal Pine Barrens 

85. Southern California/Northern Baja 

Coast 

See Map A in docket. 

The agencies would consider the 

‘‘other waters’’ in a single point of entry 

watershed in these identified ecoregions 

as similarly situated for purposes of 

aggregation for a significant nexus 

analysis. The agencies expect that this 

approach would lead to all similarly 

situated other waters within single point 

of entry watersheds within an ecoregion 

being found jurisdictional through casespecific analysis of significant nexus. 

Alternately, the agencies could 

determine that the similarly situated 

waters within each ecoregion have a 

significant nexus and are jurisdictional 

by rule and therefore do not require a 

case-specific significant nexus analysis. 

The agencies request comment on the 

list of ecoregions above and whether 

this list is appropriate, and whether 

there are other ecoregions or distinct 

areas that should be included or 

excluded from this list. This list does 

not include regions in Alaska or Hawaii 

and the agencies request comment on 


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appropriate regions to use to analyze 

‘‘other waters’’ in those states. The 

agencies also request comment on 

whether using Level III ecoregions is 

appropriate or whether a finer gradation 

of ecoregions would be more 

appropriate. 

The factors the agencies used in 

developing the list above are: 

a. Density of ‘‘other waters’’ such that 

there can be periodic surface hydrologic 

connections among the waters, for 

example in West Coast vernal pools. 

b. Soil permeability and surface or 

shallow subsurface flow such that the 

‘‘other waters’’ can be considered 

hydrologically connected, such as many 

Texas coastal prairie wetlands. 

c. Water chemistry which indicates 

that the ‘‘other waters’’ are part of the 

same system and influenced by the 

same processes. 

d. Physical capacity of ‘‘other waters’’ 

to provide flood and sediment retention; 

this is a case where several small 

wetlands together may have a different 

effect than a single large wetland 

providing the same function, for 

example prairie potholes in the 

Missouri Coteau. 

e. Co-location of waters to each other 

or similarly to the tributary system such 

that their cumulative and additive 

effects on pollutant removal through 

parallel, serial, or sequential processing 

are apparent, such as the role of 

pocosins in maintaining water quality in 

estuaries. 

f. ‘‘Other waters’’ that are sufficiently 

near each other or the tributary system 

and thus function as an integrated 

habitat that can support the life cycle of 

a species or more broadly provide 

habitat to a large number of a single 

species. 

The agencies request comment on the 

factors above and whether this list of 

factors is appropriate, and whether there 

are other factors that should be included 

or excluded from this list. Comments 

should address the science that supports 

each comment. 

In addition to ecoregions, another 

method of mapping boundaries where 

waters could be considered to be 

similarly situated for a significant nexus 

analysis would be to rely on hydrologiclandscape regions. Hydrologiclandscape regions are groups of 

watersheds that are clustered together 

on the basis of similarities in landsurface form, geologic texture, and 

climate characteristics. (D.M. Wolock, et 

al. ‘‘Delineation and Evaluation of 

Hydrologic-Landscape Regions in the 

United States Using Geographic 

Information System Tools and 

Multivariate Statistical Analyses,’’ 

Environmental Management 

34(Supplement 1):S71–S88 (2004)). 

Hydrologic-landscape regions are based 

on a concept that reflects fundamental 

hydrologic processes that are expected 

to affect water quality and other 

environmental characteristics. 

The agencies seek comment on the 

technical bases for using ecoregions and 

hydrologic-landscape regions under this 

option. Commenters may also address 

whether some other method or 

combination of methods (certain 

ecoregions and hydrologic-landscape 

regions, for example) of mapping 

geographic boundaries is better 

supported by the science. Comments 

should also address whether and how 

this option is consistent with the 

science and the caselaw. 

If the agencies choose to determine by 

rule that ‘‘other waters’’ in certain 

ecoregions or other geographic 

boundaries are similarly situated, the 

agencies could also determine that 

waters not located in identified 

ecoregions or otherwise specifically 

identified areas are not similarly 

situated for purposes of establishing a 

significant nexus and jurisdiction. The 

agencies also request comment on 

whether ‘‘other waters’’ that are not 

found in identifiable mapped ecoregions 

or other areas should be analyzed 

individually on a case-specific basis for 

determining a significant nexus, and on 

whether or not case-specific analysis of 

whether there are similarly situated 

‘‘other waters’’ in the area is advisable. 

2. Determine by rule that certain 

additional subcategories of waters 

would be jurisdictional rather than 

addressed with a case-specific analysis, 

and that other subcategories of waters 

would be non-jurisdictional. 

The agencies could choose to 

determine that there is science available 

to determine by rule that certain 

additional subcategories of ‘‘other 

waters’’ are similarly situated and have 

a significant nexus and are 

jurisdictional by rule rather than 

addressed with a case-specific 

significant nexus analysis under 

paragraph (a)(7). Such an approach 

would lead to certain subcategories of 

‘‘other waters’’ being determined 

jurisdictional in the same way that 

waters under paragraphs (a)(1) through 

(a)(6) are jurisdictional without a casespecific significant nexus analysis. 

Under this option the agencies could 

determine that waters such as prairie 

potholes, Carolina and Delmarva bays, 

pocosins, Texas coastal prairie 

wetlands, western vernal pools, and 

perhaps other categories of waters, 

either alone or in combination with 

other waters of the same type in a single 

point of entry watershed, have a 

significant nexus and are jurisdictional 

by rule. See Appendix A, Part II, iii.C(1). 

These waters would not require a casespecific significant nexus analysis to 

determine jurisdiction. 

In addition, the agencies could 

determine that other subcategories of 

waters are not jurisdictional and lack a 

significant nexus to an (a)(1) through 

(a)(3) water. Under this option the 

agencies could conclude that ‘‘other 

waters’’ such as playa lakes in the Great 

Plains, even in combination with other 

playa lakes in a single point of entry 

watershed, lack a significant nexus and 

therefore are not jurisdictional. See 

Appendix A, Part II, iii.C(1). 

Under this approach, where a playa 

lake, or other excluded category of 

water, would be within a category 

established by paragraphs (a)(1) through 

(a)(6) of the proposed rule (e.g., the 

playa is an interstate water or the playa 

is adjacent to an (a)(1) through (a)(5) 

water), the playas would be 

jurisdictional. (See R.W. Tiner, 

‘‘Geographically Isolated Wetlands of 

the United States,’’ Wetlands 23(3):494– 

516 (2003); M.G. Forbes, et al., 

‘‘Nutrient Transformation and Retention 

by Coastal Prairie Wetlands, Upper Gulf 

Coast, Texas,’’ Wetlands 32(4): 705–715 

(2012)). 

The agencies seek comment on how 

they should categorize the remaining 

‘‘other waters.’’ The agencies seek 

comment on whether these remaining 

‘‘other waters’’ should be nonjurisdictional because they would lack a 

significant nexus to a traditional 

navigable water, interstate water, or the 

territorial seas. 

There is substantial value to the 

regulated public and all other 

stakeholders in providing increased 

certainty regarding which ‘‘other 

waters’’ are jurisdictional and which are 

not. By expanding the categories of 

waters determined jurisdictional and 

expanding the categories of waters not 

categorized as jurisdictional, the 

agencies can better address the clarity, 

certainty, and predictability goals of this 

rule. However, the agencies 

acknowledge that the science may not 

be sufficient today to conclusively 

determine whether all categories of 

other waters significantly affect the 

chemical, physical and biological 

integrity of (a)(1) through (a)(3) waters. 

The agencies seek comment on the 

science used in support of the proposed 

rule, plus any additional science they 

should consider when determining 

jurisdiction. The agencies also seek 

comment on how inconclusiveness of 

the science relates to the use of casespecific determinations. As the science 

develops, the agencies could determine 


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that additional categories of ‘‘other 

waters’’ are similarly situated and have 

a significant nexus and are 

jurisdictional by rule, or that as a class 

they do not have such a significant 

nexus and might not be jurisdictional. 

If waters are categorized as nonjurisdictional because of a lack of 

science available today, the agencies 

request comment on how to best 

accommodate evolving science in the 

future that could indicate a significant 

nexus for these ‘‘other waters.’’ 

Specifically, the agencies request 

comment as to whether this should be 

done through subsequent rulemaking, or 

through some other approach, such as 

through a process established in this 

rulemaking. 

The agencies also seek comment on 

how the science supports retaining the 

case-specific determination for the 

remaining ‘‘other waters’’ that are 

neither specifically included nor 

excluded from jurisdiction. Retaining 

the case-specific analysis for these other 

waters would not enhance clarity of 

jurisdiction for these other waters, but it 

would retain the ability for a 

jurisdictional determination consistent 

with the objective of the CWA to restore 

and maintain the chemical, physical, 

and biological integrity of the nation’s 

waters. In the alternative, the agencies 

seek comment on whether it would be 

appropriate to categorize remaining 

‘‘other waters’’ as not jurisdictional. The 

agencies specifically seek comment on 

how these ‘‘other waters’’ should be 

considered. 

3. Additional ‘‘other waters’’ 

approaches. 

The agencies request comment on 

additional ‘‘other waters’’ approaches 

considered, but not proposed by the 

agencies. 

The agencies could determine that no 

‘‘other waters’’ are similarly situated, 

and all significant nexus analyses would 

be made on a case-specific basis for each 

individual ‘‘other water.’’ The agencies 

expect that this likely would result in 

few if any other waters being found 

jurisdictional. The agencies recognize 

that if they determine there are no 

similarly situated ‘‘other waters,’’ there 

are issues about consistency with 

existing scientific information and 

studies regarding the functional 

relationship of ‘‘other waters’’ of the 

same type, and their contribution to the 

chemical, physical, or biological 

integrity of streams, rivers, lakes, and 

similar waters. There are also questions 

of how finding no ‘‘other waters’’ to be 

similarly situated reconciles with the 

portion of Justice Kennedy’s opinion 

discussing ‘‘similarly situated’’ waters 

in the region that ‘‘significantly affect’’ 

the chemical, physical, or biological 

integrity of waters more traditionally 

understood as navigable. While the 

agencies do not propose to determine 

that no ‘‘other waters’’ are similarly 

situated and aggregated, the agencies 

specifically seek comment on whether 

and how choosing to find no ‘‘other 

waters’’ similarly situated would be 

consistent with the science, the CWA, 

and the caselaw. 

The agencies also considered and seek 

comment on all ‘‘other waters’’ in a 

single point of entry watershed being 

evaluated as a single landscape unit 

with regard to their effect on traditional 

navigable waters, interstate waters, and 

the territorial seas. 

The agencies seek comment that 

would inform a decision that these 

‘‘other waters’’ in a single point of entry 

watershed perform similar functions 

and are located sufficiently close 

together or to a paragraph (a)(1) through 

(a)(5) water so that they can be 

aggregated and evaluated as a single 

landscape unit with regard to their 

effects on the nearest (a)(1) through 

(a)(3) water. Generally, the agencies 

anticipate that if the other waters in a 

single point of entry watershed are 

aggregated as a single unit, these waters 

would be determined to have a 

significant nexus and be jurisdictional. 

The agencies recognize that if they 

choose to aggregate all other waters in 

a single point of entry watershed, there 

likely is insufficient existing scientific 

information to support the 

determination that all ‘‘other waters’’ in 

watersheds across the nation are 

similarly situated as provided in this 

rule and described in the caselaw. There 

are also questions of how determining 

‘‘other waters’’ in a single point of entry 

watershed to be similarly situated 

reconciles with the portion of Justice 

Kennedy’s opinion discussing 

‘‘similarly situated’’ waters in the region 

that ‘‘significantly affect’’ the chemical, 

physical, or biological integrity of 

waters more traditionally understood as 

navigable. While the agencies do not 

propose to determine that ‘‘other 

waters’’ in a single point of entry 

watershed are similarly situated and 

aggregated, the agencies seek comment 

on whether and how choosing to find 

such ‘‘other waters’’ similarly situated 

would be consistent with the science, 

the CWA, and the caselaw. 

The agencies’ determination will be 

informed by the final version of the 

Report and other available scientific 

information. 

I. Waters That Are Not ‘‘Waters of the 

United States’’ 

The agencies’ longstanding 

regulations exclude waste treatment 

systems designed to meet the 

requirements of the CWA and prior 

converted cropland from the definition 

of ‘‘waters of the United States.’’ The 

agencies propose no changes to these 

exclusions and therefore they would 

continue as a part of this rulemaking. 

The agencies also propose to codify for 

the first time longstanding practices that 

have generally considered certain 

features and types of waters not to be 

‘‘waters of the United States.’’ Codifying 

these longstanding practices supports 

the agencies’ goals of providing greater 

clarity, certainty, and predictability for 

the regulated public and the regulators. 

Under today’s proposal, the waters 

identified in section (b) as excluded 

would not be ‘‘waters of the United 

States,’’, even if they would otherwise 

fall within one of the categories in (a)(1) 

through (a)(7). 

The agencies propose ministerial 

actions with respect to the placement of 

the two existing exemptions for waste 

treatment systems and prior converted 

cropland. They will be in proposed new 

section (b). For the waste treatment 

systems exclusion, the agencies propose 

to delete a cross-reference in the current 

language to an EPA regulation that is no 

longer in the Code of Federal 

Regulations. The parenthetical to be 

deleted states: ‘‘(other than cooling 

ponds as defined in 40 CFR 423.11(m) 

which also meet the criteria of this 

definition).’’ The agencies do not 

consider this deletion to be a 

substantive change to the waste 

treatment systems exclusion or how it is 

applied. In fact, the agencies do not 

propose to make conforming changes to 

ensure that each of the existing 

definitions of the ‘‘waters of the United 

States’’ for the various CWA programs 

have the exact same language with 

respect to the waste treatment system 

exclusion. The regulations 

implementing the various CWA 

programs were promulgated and 

amended at different times and 

therefore there are some differences in 

language. For example, compare EPA’s 

regulations for the section 402 program, 

40 CFR 122.2 with the Corps’ 

regulations for the 404 program, 33 CFR 

328.3. The agencies do not propose to 

address the substance of the waste 

treatment system exclusion and thus 

will leave each regulation as is with the 

exception of deleting the crossreference. 

In addition, this regulation does not 

address or change in any way the many 


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statutory exemptions from CWA 

permitting requirements. The proposed 

rule does not affect any of the 

exemptions provided by CWA section 

404(f), including those for normal 

farming, silviculture, and ranching 

activities. CWA section 404(f); 40 CFR 

232.3; 33 CFR 323.4. The proposed rule 

also does not address or change the 

statutory and regulatory exemptions 

from NPDES permitting requirements 

such as those for agricultural 

stormwater discharges, return flows 

from irrigated agriculture, or the status 

of water transfers. CWA section 402(l)(1) 

(exempting discharges composed 

entirely of return flows from irrigated 

agriculture from section 402 permit 

requirements); CWA section 

502(14)(excluding agricultural 

stormwater discharges and return flows 

from irrigated agriculture from the term 

point source.); 40 CFR 122.3(f) 

(excluding return flows from irrigated 

agriculture from the NPDES program); 

40 CFR 122.2 (excluding return flows 

from irrigated agriculture or agricultural 

storm water runoff from the term point 

source.). 

Finally, in new paragraphs (b)(3) 

through (5), the agencies propose, for 

the first time by rule, to exclude some 

waters and features that the agencies 

have by longstanding practice generally 

considered not to be ‘‘waters of the 

United States.’’ Specifically, the 

agencies propose that the following are 

not ‘‘waters of the United States’’ 

notwithstanding whether they would 

otherwise be jurisdictional under 

section (a): 

• Ditches that are excavated wholly 

in uplands, drain only uplands, and 

have less than perennial flow. 

• Ditches that do not contribute flow, 

either directly or through another water, 

to a traditional navigable water, 

interstate water, the territorial seas or 

impoundment. 

• The following features: 

Æ Artificially irrigated areas that 

would revert to upland should 

application of irrigation water to that 

area cease; 

Æ Artificial lakes or ponds created by 

excavating and/or diking dry land and 

used exclusively for such purposes as 

stock watering, irrigation, settling 

basins, or rice growing; 

Æ Artificial reflecting pools or 

swimming pools created by excavating 

and/or diking dry land; 

Æ Small ornamental waters created by 

excavating and/or diking dry land for 

primarily aesthetic reasons; 

Æ Water-filled depressions created 

incidental to construction activity; 

Æ Groundwater, including 

groundwater drained through 

subsurface drainage systems; and 

Æ Gullies and rills and non-wetland 

swales. 

Most of these features and waters 

have been identified by the agencies as 

generally not ‘‘waters of the United 

States’’ in previous preambles or 

guidance documents. The agencies’ 

have always preserved the authority to 

determine in a particular case that any 

of these waters are a ‘‘water of the 

United States.’’ One of the agencies’ 

goals in this proposed rule is to increase 

clarity and certainty about the scope of 

‘‘waters of the United States.’’ To that 

end, the agencies propose not simply 

that these features and waters are 

‘‘generally’’ not ‘‘waters of the United 

States,’’ but that they are expressly not 

‘‘waters of the United States’’ by rule. 

The agencies would not retain the 

authority to determine that any of these 

waters was a ‘‘water of the United 

States’’ because it would otherwise be 

jurisdictional under section (a). For 

example, the agencies could not find 

that a water had a significant nexus and 

was an ‘‘other waters’’ under paragraph 

(a)(7), or that it was an interstate water 

under paragraph (a)(2). These waters 

would not be jurisdictional by rule. 

In determining that these features and 

waters are not ‘‘waters of the United 

States,’’ the agencies are by the 

decisions of the Supreme Court. In 

Riverside Bayview, the Supreme Court 

deferred to the agencies’ regulations and 

noted the difficulty of drawing lines 

identifying where waters end. The 

plurality opinion in Rapanos also noted 

that there were certain features that 

were not primarily the focus of the 

CWA. See 547 U.S. at 734. In this 

section of the proposed rule, the 

agencies are drawing lines and 

concluding that certain waters and 

features are not subject to the 

jurisdiction of the Clean Water Act. 

A similar list of waters and features 

not generally ‘‘waters of the United 

States’’ was provided by the Corps in a 

1986 preamble to the existing rule 

defining ‘‘waters of the United States’’ 

(51 FR 41206, 41217, November 13, 

1986) and by the EPA in a 1988 

preamble (53 FR 20764, June 6, 1988). 

In today’s proposed rule, the agencies 

have clarified and added to the list in 

order to provide a full description of the 

waters that will not be ‘‘waters of the 

United States’’ by rule. The agencies 

have never interpreted ‘‘waters of the 

United States’’ to include groundwater 

and the proposed rule explicitly 

excludes groundwater, including 

groundwater drained through 

subsurface drainage systems. 

In clarifying the list of waters not 

subject to CWA jurisdiction, the 

agencies did not include ‘‘puddles’’ 

from the lists of waters generally not 

considered jurisdictional in previous 

preambles or guidance documents. This 

is not because puddles are considered 

jurisdictional, it is because ‘‘puddles’’ is 

not a sufficiently precise hydrologic 

term or a hydrologic feature capable of 

being easily understood. Because of the 

lack of common understanding and 

precision inherent in the term 

‘‘puddles,’’ the agencies determined that 

adding puddles would be contrary to 

the agencies’ stated goals of increased 

clarity, predictability, and certainty. In 

addition, one commonly understood 

meaning for the term ‘‘puddle’’ is a 

relatively small, temporary pool of 

water that forms on pavement or 

uplands immediately after a rainstorm, 

snow melt, or similar event. Such a 

puddle cannot reasonably be considered 

a water body or aquatic feature at all, 

because usually it exists for only a brief 

period of time before the water in the 

puddle evaporates or sinks into the 

ground. Puddles of this sort obviously 

are not, and have never been thought to 

be, waters of the United States subject 

to CWA jurisdiction. Listing puddles 

also could have created the 

misapprehension that anything larger 

than a puddle was jurisdictional. That is 

not the agencies’ intent. 

Gullies are relatively deep channels 

that are ordinarily formed on valley 

sides and floors where no channel 

previously existed. They are commonly 

found in areas with low-density 

vegetative cover or with soils that are 

highly erodible. See, e.g., N.C. Brady 

and R.R. Weil, The Nature and 

Properties of Soils, 13th Edition (Upper 

Saddle River, NJ: Prentice Hall, 2002). 

Rills are formed by overland water flows 

eroding the soil surface during rain 

storms. See, e.g., L.B. Leopold, A View 

of the River (Cambridge: Harvard 

University Press, 1994). Rills are less 

permanent on the landscape than 

streams and typically lack an OHWM, 

whereas gullies are younger than 

streams in geologic age and also 

typically lack an OHWM; time has 

shaped streams into geographic features 

distinct from gullies and rills. See, e.g., 

American Society of Civil Engineers, 

Task Committee on Hydrology 

Handbook, Hydrology Handbook (ASCE 

Publications, 1996). 

The two main processes that result in 

the formation of gullies are downcutting 

and headcutting, which are forms of 

longitudinal (incising) erosion. These 

actions ordinarily result in erosional 

cuts that are often deeper than they are 

wide, with very steep banks, often small 


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beds, and typically only carry water 

during precipitation events. The 

principal erosional processes that 

modify streams are also downcutting 

and headcutting. In streams, however, 

lateral erosion is also very important. 

The result is that streams, except on 

steep slopes or where soils are highly 

erodible, are characterized by the 

presence of bed and banks and an 

OHWM as compared to typical erosional 

features that are more deeply incised. It 

should be noted that some ephemeral 

streams are called ‘‘gullies’’ or the like 

when they are not ‘‘gullies’’ in the 

technical sense; such streams where 

they are tributaries under the proposed 

definition would be considered ‘‘waters 

of the United States,’’ regardless of the 

name they are given locally. The 

agencies request comment on how they 

could provide greater clarity on how to 

distinguish between erosional features 

such as gullies, which are excluded 

from jurisdiction, and ephemeral 

tributaries, which are categorically 

jurisdictional. 

Non-wetland natural and man-made 

swales would not be ‘‘waters of the 

United States’’ under this proposal. In 

certain circumstances, however, swales 

include areas that meet the regulatory 

definition of ‘‘wetlands.’’ Swales 

generally are considered wetlands when 

they meet the applicable criteria in the 

Corps of Engineers Wetland Delineation 

Manual and the appropriate regional 

supplement to that Wetland Delineation 

Manual. Wetland swales would be 

evaluated as adjacent waters under 

proposed (a)(6) or as ‘‘other waters’’ 

under proposed (a)(7) depending upon 

whether they meet the proposed 

definition of adjacent. Swales are 

distinct from streams in that they are 

non-channelized, shallow trough-like 

depressions that carry water mainly 

during rainstorms or snowmelt. Report 

at A–19. Swales typically lack the 

OHWM that is characteristic of 

jurisdictional streams. The agencies 

request comment on how they could 

provide greater clarity on how to 

distinguish swales, which are excluded 

from jurisdiction, and ephemeral 

tributaries, which are categorically 

jurisdictional. 

Finally, under paragraphs (b)(3) and 

(b)(4), the agencies propose to clearly 

exempt from the definition of ‘‘waters of 

the United States’’ two types of ditches: 

(1) Ditches that are excavated wholly in 

uplands, drain only uplands, and have 

less than perennial flow, and (2) ditches 

that do not contribute flow, either 

directly or through another water, to a 

water identified in paragraphs (a)(1) 

through (4). 

The agencies have long distinguished 

between ditches that are ‘‘waters of the 

United States’’ and ditches that are not 

‘‘waters of the United States.’’ In a 1986 

Corps preamble and a 1988 EPA 

preamble, the agencies each stated that 

they generally do not consider non-tidal 

drainage and irrigation ditches 

excavated on dry land to be ‘‘waters of 

the United States.’’ 51 FR 41217, 

November 13, 1986, 53 FR 20764, June 

6, 1988. More recently, the agencies 

have stated that they generally would 

not assert jurisdiction over ‘‘Ditches 

(including roadside ditches) excavated 

wholly in and draining only uplands 

and that do not carry a relatively 

permanent flow of water.’’ ‘‘Clean Water 

Act Jurisdiction Following the Supreme 

Court’s Decision in Rapanos v. United 

States and Carabell v. United States’’ 

(Dec. 2, 2008) at 1, 12 (2008 Rapanos 

guidance). 

The agencies recognize that there 

have been inconsistencies in practice 

implementing agency policy with 

respect to ditches and this proposed 

rule is designed to improve clarity, 

predictability, and consistency. With 

this proposal, the agencies would no 

longer rely on ‘‘generally not’’ 

jurisdictional but would clearly 

establish that specific types of ditches 

are not ‘‘waters of the United States’’ by 

rule. Other ditches not excluded under 

paragraphs (b)(3) or (b)(4), if they meet 

the new proposed definition of 

‘‘tributary’’ would continue to be 

‘‘waters of the United States,’’ as they 

have been under the longstanding 

implementation of the statute and 

regulations by the agencies. 

The first type of ditch that is excluded 

needs to meet all three criteria: (1) It is 

excavated wholly in uplands; (2) it 

drains only uplands, and (3) it has less 

than perennial flow. Ditches that are 

excavated wholly in uplands means 

ditches that at no point along their 

length are excavated in a jurisdictional 

wetland (or other water). Members of 

the public should consider whether a 

wetland is jurisdictional before 

constructing a ditch that would drain 

the wetland and connect either directly 

or through other waters to an (a)(1) 

through (a)(3) water. The ditch must 

also contain less than perennial flow to 

be excluded under this proposed 

provision. Perennial flow means that the 

flow in the ditch occurs year-round 

under normal circumstances; therefore, 

excluded ditches must be dug only in 

uplands, drain only uplands, and have 

ephemeral or intermittent flow. As 

noted above, the 2008 Rapanos 

guidance stated that the agencies 

generally would not assert jurisdiction 

over ‘‘ditches (including roadside 

ditches) excavated wholly in and 

draining only uplands and that do not 

carry a relatively permanent flow of 

water.’’ The agencies recognize that the 

term ‘‘relatively permanent’’ does not 

align with more commonly understood 

technical descriptions of flow regime. 

The agencies therefore believe it is 

appropriate to clarify the extent of this 

exclusion using the flow regime terms 

that are familiar to the public and 

agency field personnel. The agencies 

request comment on this formulation of 

the ditch exclusion. The agencies 

specifically seek comment on the 

appropriate flow regime for a ditch 

excavated wholly in uplands and 

draining only uplands to be covered by 

the exclusion in paragraph (b)(3). In 

particular, the agencies seek comment 

on whether the flow regime in such 

ditches should be less than intermittent 

flow or whether the flow regime in such 

ditches should be less than perennial 

flow as proposed. 

The other type of ditch that would not 

be a ‘‘water of the United States’’ is a 

ditch that does not contribute flow, 

either directly or through another water, 

to a water identified in paragraphs (a)(1) 

through (4). Essentially, ditches that do 

not contribute flow to the tributary 

system of a traditional navigable water, 

interstate water or territorial sea would 

not be ‘‘waters of the United States.’’ 

It is important to note, however, that 

even when not jurisdictional waters, 

these non-wetland swales, gullies, rills 

and specific types of ditches may still be 

a surface hydrologic connection for 

purposes of the proposed definition of 

adjacent under paragraph (a)(6) or for 

purposes of a significant nexus analysis 

under paragraph (a)(7). For example, a 

wetland may be a ‘‘water of the United 

States,’’ meeting the proposed definition 

of ‘‘neighboring’’ because it is connected 

to such a tributary by a nonjurisdictional ditch that does not meet 

the definition of a ‘‘tributary.’’ In 

addition, these geographic features may 

function as ‘‘point sources’’ under CWA 

section 502(14)), such that discharges of 

pollutants to waters through these 

features would be subject to other CWA 

regulations (e.g., CWA section 402). 

IV. Related Acts of Congress, Executive 

Orders, and Agency Initiatives 

A. Executive Order 12866: Regulatory 

Planning and Review and Executive 

Order 13563: Improving Regulation and 

Regulatory Review 

Under Executive Order 12866 (58 FR 

51735, October 4, 1993), this action is a 

‘‘significant regulatory action.’’ 

Accordingly, the EPA and the Corps 

submitted this action to the Office of 


emcdonald on DSK67QTVN1PROD with PROPOSALS2
22220 Federal Register / Vol. 79, No. 76 / Monday, April 21, 2014 / Proposed Rules 

Management and Budget (OMB) for 

review under Executive Orders 12866 

and 13563 (76 FR 3821, January 21, 

2011) and any changes made in 

response to OMB recommendations 

have been documented in the docket for 

this action. 

In addition, the EPA and the Corps of 

Engineers prepared an analysis of the 

potential costs and benefits associated 

with this action. This analysis is 

contained in ‘‘Economic Analysis of 

Proposed Revised Definition of Waters 

of the United States.’’ A copy of the 

analysis is available in the docket for 

this action. 

B. Paperwork Reduction Act 

This action does not impose any 

information collection burden under the 

provisions of the Paperwork Reduction 

Act, 44 U.S.C. 3501 et seq. Burden is 

defined at 5 CFR 1320.3(b). An Agency 

may not conduct or sponsor, and a 

person is not required to respond to, a 

collection of information unless it 

displays a currently valid OMB control 

number. The OMB control numbers for 

EPA’s CWA section 402 program may be 

found at 40 CFR 9.1. (OMB Control No. 

2040–0004, EPA ICR No. 0229.19). For 

the CWA section 404 regulatory 

program, the current OMB approval 

number for information requirements is 

maintained by the Corps of Engineers 

(OMB approval number 0710–0003). 

However, there are no new approval or 

application processes required as a 

result of this rulemaking that necessitate 

a new Information Collection Request 

(ICR). 

C. Regulatory Flexibility Act 

The Regulatory Flexibility Act (RFA) 

generally requires an agency to prepare 

a regulatory flexibility analysis of any 

rule subject to notice-and-comment 

rulemaking requirements under the 

Administrative Procedure Act or any 

other statute unless the agency certifies 

that the rule will not have a significant 

economic impact on a substantial 

number of small entities. Small entities 

include small businesses, small 

organizations, and small governmental 

jurisdictions. 

For purposes of assessing the impacts 

of this final action on small entities, 

‘‘small entity’’ is defined as: (1) A small 

business that is a small industrial entity 

as defined in the U.S. Small Business 

Administration’s size standards (see 13 

CFR 121.201); (2) a small governmental 

jurisdiction that is a government of a 

city, county, town, school district, or 

special district with a population of less 

than 50,000; or (3) a small organization 

that is any not-for-profit enterprise that 

is independently owned and operated 

and is not dominant in its field. 

After considering the economic 

impacts of this proposed rule on small 

entities, I certify that this proposed rule 

will not have a significant economic 

impact on a substantial number of small 

entities. See, e.g., Cement Kiln Recycling 

Coalition v. EPA, 255 F.3d 855 (D.C. Cir. 

2001); Michigan v. EPA, 213 F.3d 663 

(D.C. Cir. 2000); Am. Trucking Ass’n v. 

EPA, 175 F.3d 1027 (D.C. Cir. 1999); 

Mid-Tex Elec. Co-op, Inc. v. FERC, 773 

F.2d 327 (D.C. Cir. 1985). 

Under the RFA, the impact of concern 

is any significant adverse economic 

impact on small entities, because the 

primary purpose of the initial regulatory 

flexibility analysis is to identify and 

address regulatory alternatives ‘‘which 

minimize any significant economic 

impact of the rule on small entities.’’ 5 

U.S.C. 603. The scope of regulatory 

jurisdiction in this proposed rule is 

narrower than that under the existing 

regulations. See 40 CFR 122.2 (defining 

‘‘waters of the United States’’). Because 

fewer waters will be subject to the CWA 

under the proposed rule than are subject 

to regulation under the existing 

regulations, this action will not affect 

small entities to a greater degree than 

the existing regulations. As a 

consequence, this action if promulgated 

will not have a significant adverse 

economic impact on a substantial 

number of small entities, and therefore 

no regulatory flexibility analysis is 

required. 

The proposed rule contemplated here 

is not designed to ‘‘subject’’ any entities 

of any size to any specific regulatory 

burden. Rather, it is designed to clarify 

the statutory scope of ‘‘the waters of the 

United States, including the territorial 

seas’’ (33 U.S.C. 1362(7)), consistent 

with Supreme Court precedent. This 

question of CWA jurisdiction will be 

informed by the tools of statutory 

construction and the geographical and 

hydrological factors identified in 

Rapanos v. United States, 547 U.S. 715 

(2006), which are not factors readily 

informed by the RFA. 

Nevertheless, the scope of the term 

‘‘waters of the United States’’ is a 

question that has continued to generate 

substantial interest, particularly within 

the small business community, because 

permits must be obtained for many 

discharges of pollutants into those 

waters. In light of this interest, the EPA 

and the Corps determined to seek early 

and wide input from representatives of 

small entities while formulating a 

proposed definition of this term that 

reflects the intent of Congress consistent 

with the mandate of the Supreme 

Court’s decisions. Such outreach, 

although voluntary, is also consistent 

with the President’s January 18, 2011 

Memorandum on Regulatory Flexibility, 

Small Business, and Job Creation, which 

emphasizes the important role small 

businesses play in the American 

economy. This process has enabled the 

agencies to hear directly from these 

representatives, at a very preliminary 

stage, about how they should approach 

this complex question of statutory 

interpretation, together with related 

issues that such representatives of small 

entities may identify for possible 

consideration in separate proceedings. 

The agencies have also prepared a 

report summarizing their small entity 

outreach to date, the results of this 

outreach, and how these results have 

informed the development of this 

proposed rule. This report is available 

in the docket for this proposed rule 

(cite). 

D. Unfunded Mandates Reform Act 

This proposed rule contains no 

Federal mandates (under the regulatory 

provisions of Title II of the Unfunded 

Mandates Reform Act of 1995 (UMRA), 

2 U.S.C. 1531–1538 for state, local, or 

tribal governments or the private sector. 

This proposed rule does not directly 

regulate or affect any entity and, 

therefore, is not subject to the 

requirements of sections 202 and 205 of 

UMRA. 

The agencies determined that this 

proposed rule contains no regulatory 

requirements that might significantly or 

uniquely affect small governments. 

Moreover, the proposed definition of 

‘‘waters of the United States’’ applies 

broadly to CWA programs and the 

subsequently affected entities, which 

are not uniquely applicable to small 

governments. Thus, this proposed rule 

is not subject to the requirements of 

section 203 of UMRA. 

E. Executive Order 13132: Federalism 

This proposed rule seeks to clarify the 

definition of the extent of CWA 

jurisdiction established by statute. State 

and local governments have welldefined and long-standing relationships 

in implementing affected CWA 

programs and these relationships will 

not be altered. Forty-six states and the 

Virgin Islands have been authorized to 

administer the NPDES program under 

section 402, while two states administer 

the section 404 program. This action 

will not have substantial direct effects 

on the states, on the relationship 

between the national government and 

the states, or on the distribution of 

power and responsibilities among the 

various levels of government. Thus, 

Executive Order 13132 (64 FR 43255, 


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August 10, 1999) does not apply to this 

action. Consistent with EPA and Corps 

policy to promote communications 

between the agencies and state and local 

governments, and in recognition of the 

vital role states play in implementation 

of the CWA, EPA voluntarily undertook 

federalism consultation for this effort 

and met the terms of E.O. 13132 and 

EPA guidance for implementing the 

Order. EPA held a series of meetings 

and outreach calls with state and local 

governments and their representatives 

soliciting input on a potential rule to 

define ‘‘waters of the United States.’’ 

As part of this consultation, early in 

the rulemaking process, EPA held three 

in-person meetings and two phone calls 

in the fall and winter of 2011. 

Organizations involved include the 

National Governors Association, the 

National Conference of State 

Legislatures, the Council of State 

Governments, the National Association 

of Counties, the National League of 

Cities, the U.S. Conference of Mayors, 

the County Executives of America, the 

National Associations of Towns and 

Townships, the International City/ 

County Management Association, and 

the Environmental Council of States. In 

addition, the National Association of 

Clean Water Agencies (NACWA) and 

the Association of Clean Water 

Administrators (ACWA) were invited to 

participate. As part of the consultation 

12 counties, 8 associations and various 

state agencies and offices from five 

states (Alaska, Wyoming, Kansas, 

Tennessee, and Texas) submitted 

written comments. In addition, EPA 

held numerous outreach calls with state 

and local government agencies seeking 

their technical input. More than 400 

people from a variety of state and local 

agencies and associations, including the 

Western Governors’ Association, the 

Western States Water Council and the 

Association of State Wetland Managers 

participated in various calls and 

meetings. 

The agencies engaged in voluntary 

federalism consultation on this rule and 

we will continue to work closely with 

the states with respect to development 

of a final rule. Additionally, EPA and 

the Corps are specifically soliciting 

comments on this proposed action from 

state and local officials. The agencies 

will include a detailed narrative of 

intergovernmental concerns raised 

during the course of the rule’s 

development and a description of the 

agencies’ efforts to address them with 

the final rule. 

F. Executive Order 13175: Consultation 

and Coordination With Indian Tribal 

Governments 

Subject to the Executive Order (E.O.) 

13175 (65 FR 67249, November 9, 2000) 

Agencies may not issue a regulation that 

has tribal implications, that imposes 

substantial direct compliance costs, and 

that is not required by statute, unless 

the Federal government provides the 

funds necessary to pay the direct 

compliance costs incurred by tribal 

governments, or the Agencies consult 

with tribal officials early in the process 

of developing the proposed regulation 

and develops a tribal summary impact 

statement. This action does not have 

tribal implications as specified in E.O. 

13175. 

In compliance with the EPA Policy on 

Consultation and Coordination with 

Indian Tribes (May 4, 2011), EPA 

consulted with tribal officials to gain an 

understanding of and, where 

appropriate, to address the tribal 

implications of the proposed rule. In the 

course of this consultation EPA 

coordinated with the Corps, and the 

Corps jointly participated in aspects of 

the consultation process. In the fall of 

2011 EPA sent a Tribal Consultation 

Notification letter to all federallyrecognized tribal leaders, via mail and 

email, inviting tribal officials to 

participate in outreach and consultation 

events and provide comments to EPA in 

coordination with the Corps. Close to 

200 tribal representatives and more than 

40 tribes participated in the 

consultation process, which included 

multiple webinars and national 

teleconferences and face-to-face 

meetings. In addition, EPA received 

written comments from 3 tribes during 

the consultation period. In the spirit of 

E.O. 13175, and consistent with EPA 

and Corps policy to promote 

communications between the agencies 

and tribal governments, the agencies 

specifically solicit additional comment 

on this proposed action from tribal 

officials. 

G. Executive Order 13045: Protection of 

Children From Environmental Health 

and Safety Risks 

This action is not subject to E.O. 

13045 because the environmental health 

or safety risks addressed by this action 

do not present a disproportionate risk to 

children. 

H. Executive Order 13211: Actions 

Concerning Regulations That 

Significantly Affect Energy Supply, 

Distribution, or Use 

This action is not a ‘‘significant 

energy action’’ as defined in Executive 

Order 13211 (66 FR 28355, May 22, 

2001), because it is not likely to have a 

significant adverse effect on the supply, 

distribution, or use of energy. 

I. National Technology Transfer and 

Advancement Act 

Section 12(d) of the National 

Technology Transfer and Advancement 

Act of 1995 (‘‘NTTAA’’), Public Law 

104–113, 12(d) (15 U.S.C. 272 note) 

directs Federal agencies to use 

voluntary consensus standards in its 

regulatory activities unless to do so 

would be inconsistent with applicable 

law or otherwise impractical. Voluntary 

consensus standards are technical 

standards (e.g., materials specifications, 

test methods, sampling procedures, and 

business practices) that are developed or 

adopted by voluntary consensus 

standards bodies. NTTAA directs 

Federal agencies to provide Congress, 

through OMB, explanations when the 

Agency decides not to use available and 

applicable voluntary consensus 

standards. 

This proposed rulemaking does not 

involve technical standards. Therefore, 

the agencies are not considering the use 

of any voluntary consensus standards. 

J. Executive Order 12898: Federal 

Actions To Address Environmental 

Justice in Minority Populations and 

Low-Income Populations 

Executive Order (E.O.) 12898 (59 FR 

7629, Feb. 16, 1994) establishes Federal 

executive policy on environmental 

justice. Its main provision directs 

Federal agencies, to the greatest extent 

practicable and permitted by law, to 

make environmental justice part of their 

mission by identifying and addressing, 

as appropriate, disproportionately high 

and adverse human health or 

environmental effects of their programs, 

policies, and activities on minority 

populations and low-income 

populations in the United States. 

The agencies have determined that 

this proposed rule will not have 

disproportionately high and adverse 

human health or environmental effects 

on minority or low-income populations. 

The proposed rule defines the scope of 

waters protected under the CWA. The 

increased clarity regarding the 

definition of ‘‘waters of the United 

States’’ will be of benefit to all 

regulators, stakeholders, and interested 

parties. However, in the spirit of 

Executive Order 12898, we specifically 

request comment regarding potential 

environmental justice issues raised by 

the proposed rule, and will fully 

consider those comments when 

preparing the final rule. 


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K. Environmental Documentation 

The U.S. Army Corps of Engineers has 

prepared a draft environmental 

assessment in accordance with the 

National Environmental Policy Act 

(NEPA). The Corps has made a 

preliminary determination that the 

section 404 aspects of today’s proposed 

rule do not constitute a major Federal 

action significantly affecting the quality 

of the human environment, and thus 

preparation of an Environmental Impact 

Statement (EIS) will not be required. 

The proposed rule will increase and 

make more efficient the protection of 

the aquatic environment. Additionally, 

the Corps complies with NEPA 

programmatically for general permits, 

and specifically for each and every 

standard individual permit application 

before making final permit decisions. 

The implementation of the procedures 

prescribed in this proposed regulation 

would not authorize anyone (e.g., any 

landowner or permit applicant) to 

perform any work involving regulated 

activities in ‘‘waters of the United 

States’’ without first seeking and 

obtaining an appropriate CWA 

authorization, which concurrently 

documents compliance with all 

applicable environmental laws. 

Appendix A 

Scientific Evidence 

Overview of Scientific Literature on Aquatic 

Resource Connectivity and Downstream 

Effects 

In preparation for this proposal, more than 

a thousand peer-reviewed scientific papers 

and other data that address connectivity of 

aquatic resources and effects on downstream 

waters were reviewed and considered. EPA’s 

Office of Research and Development (ORD) 

has prepared a draft peer-reviewed synthesis 

of published peer-reviewed scientific 

literature discussing the nature of 

connectivity and effects of tributaries and 

wetlands on downstream waters (U.S. 

Environmental Protection Agency, 

Connectivity of Streams and Wetlands to 

Downstream Waters: A Review and Synthesis 

of the Scientific Evidence, (Washington, DC: 

U.S. Environmental Protection Agency, 

2013), hereinafter, ‘‘Report’’). This draft 

Report similarly has been considered in the 

development of this proposal. The Report is 

currently undergoing peer review led by 

EPA’s Scientific Advisory Board (SAB) and is 

available at http://yosemite.epa.gov/sab/

sabproduct.nsf/fedrgstr_activites/Watershed

%20Connectivity%20Report?

OpenDocument. The Report also underwent 

an earlier peer review, and the results of this 

peer review are available in the docket for 

this proposed rule. The Report summarizes 

and assesses much of the currently available 

scientific literature that is part of the 

administrative record for this proposal. The 

agencies anticipate that additional data and 

information will become available during the 

rulemaking process, including that provided 

during the public comment process, and by 

additional research, studies, and 

investigations that take place before the 

rulemaking process is concluded. At the 

conclusion of the rulemaking process, the 

agencies will review the entirety of the 

completed administrative record, including 

the final Report reflecting SAB review, and 

will make any adjustments to the final rule 

deemed to be appropriate at that time. The 

Report is under review by the Science 

Advisory Board, and the rule will not be 

finalized until that review and the final 

report are complete. Part I of this Appendix 

provides the conclusions of the review and 

synthesis. Part II provides additional detail of 

the scientific literature and the agencies’ 

reasoning in support of this proposal. 

Part I: Synthesis of Peer-Reviewed Scientific 

Literature 

Background 

The draft Report prepared by ORD reviews 

and synthesizes the peer-reviewed scientific 

literature on the connectivity or isolation of 

streams and wetlands relative to large water 

bodies such as rivers, lakes, estuaries, and 

oceans. The purpose of the review and 

synthesis is to summarize current 

understanding about these connections, the 

factors that influence them, and the 

mechanisms by which connected waters, 

singly or in aggregate, affect the function or 

condition of downstream waters. The focus 

of the Report is on surface and shallow 

subsurface connections from small or 

temporary streams, non-tidal wetlands, and 

certain open waters. Specific types of 

connections considered in the Report include 

transport of physical materials and chemicals 

such as water, wood, and sediment, 

nutrients, pesticides, and mercury; 

movement of organisms or their seeds or 

eggs; and hydrologic and biogeochemical 

interactions occurring in surface and 

groundwater flows, including hyporheic 

zones and alluvial aquifers. 

The draft Report prepared by ORD consists 

of six chapters. Following an executive 

summary and an introduction to the Report, 

chapter 3 presents a conceptual framework 

describing the hydrologic elements of a 

watershed, the types of chemical, physical, 

and biological connections that link them, 

and watershed and climatic factors that 

influence connectivity at various temporal 

and spatial scales. It also provides 

background on the structure and function of 

streams and wetlands viewed from an 

integrated watershed perspective. In a 

discussion of connectivity, the watershed 

scale is the appropriate context for 

interpreting technical evidence about 

individual watershed components, reviewed 

in subsequent chapters. Chapter 4 surveys 

the literature on stream networks (lotic 

systems) in terms of chemical, physical, and 

biological connections between upstream and 

downstream habitats. Two case studies from 

the literature examine in greater detail 

longitudinal connectivity and downstream 

effects in prairie streams and arid streams of 

the Southwest. Chapter 5 reviews the 

literature on connectivity and effects of nontidal wetlands and certain open waters 

(lentic systems) on downstream waters. This 

chapter is further subdivided into two broad 

categories of landscape settings based on 

directionality of hydrologic flows: 

Bidirectional settings, in which wetlands and 

open waters can have two-way hydrologic 

exchanges with other water bodies (e.g., 

riparian and floodplain wetlands and open 

waters), and unidirectional settings, in which 

water flows only from the wetland or open 

water towards the downstream water (e.g., 

most wetlands and open waters outside of 

riparian areas and floodplains). Directionality 

of hydrologic flow was selected as an 

organizational principle for this section 

because it has a dominant role in 

determining the types of connectivity and 

downstream effects (if any) of wetlands. 

However, the use of these landscape settings 

for hydrologic directionality should not be 

construed as suggesting directionality of 

geochemical or biological flows. Also, the 

terms ‘‘unidirectional’’ and ‘‘bidirectional’’ 

describe the landscape setting in which 

wetlands and open waters occur, and do not 

refer to wetland type or class. Four case 

studies from the literature examine evidence 

pertaining to connectivity and downstream 

effects of oxbow lakes, Carolina and 

Delmarva bays, prairie potholes, and vernal 

pools in greater detail. 

Chapter 6 presents and discusses key 

findings and major conclusions of the review, 

which also are included at the end of each 

review section and in this executive 

summary. 

Summary of Major Conclusions 

Based on the review and synthesis of more 

than a thousand publications from the peerreviewed scientific literature, the available 

evidence supports three major conclusions: 

1. The scientific literature demonstrates 

that streams, individually and cumulatively, 

exert a strong influence on the character and 

functioning of downstream waters. All 

tributary streams, including perennial, 

intermittent, and ephemeral streams, are 

chemically, physically, and biologically 

connected to downstream rivers via channels 

and associated alluvial deposits where water 

and other materials are concentrated, mixed, 

transformed, and transported. Headwater 

streams (headwaters) are the most abundant 

stream-type in most river networks, and 

supply most of the water in rivers. In 

addition to water, streams supply sediment, 

wood, organic matter, nutrients, chemical 

contaminants, and many of the organisms 

found in rivers. Streams are biologically 

connected to downstream waters by the 

dispersal and migration of aquatic and semiaquatic organisms, including fish, 

amphibians, plants, microorganisms, and 

invertebrates, that use both up- and 

downstream habitats during one or more 

stages of their life cycles, or provide food 

resources to downstream communities. 

Chemical, physical, and biological 

connections between streams and 

downstream waters interact via processes 

such as nutrient spiraling, in which stream 

communities assimilate and chemically 

transform large quantities of nitrogen and 

other nutrients that would otherwise increase 

nutrient loading downstream. 


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2. Wetlands and open waters in landscape 

settings that have bidirectional hydrologic 

exchanges with streams or rivers (e.g., 

wetlands and open waters in riparian areas 

and floodplains) are chemically, physically, 

and biologically connected with rivers via 

the export of channel-forming sediment and 

woody debris, temporary storage of local 

groundwater that supports baseflow in rivers, 

and transport of stored organic matter. They 

remove and transform excess nutrients such 

as nitrogen and phosphorus. They provide 

nursery habitat for breeding fish, 

colonization opportunities for stream 

invertebrates, and maturation habitat for 

stream insects. Moreover, wetlands in this 

landscape setting serve an important role in 

the integrity of downstream waters because 

they also act as sinks by retaining 

floodwaters, sediment, nutrients, and 

contaminants that could otherwise negatively 

impact the condition or function of 

downstream waters. 

3. Wetlands and open waters in landscape 

settings that lack bidirectional hydrologic 

exchanges with downstream waters (e.g., 

many prairie potholes, vernal pools, and 

playa lakes) provide numerous functions that 

can benefit downstream water quality and 

integrity. These functions include storage of 

floodwater; retention and transformation of 

nutrients, metals, and pesticides; and recharge of groundwater sources of river 

baseflow. The functions and effects of this 

diverse group of wetlands, which the Report 

refers to as ‘‘unidirectional wetlands,’’ affect 

the condition of downstream waters if there 

is a surface or shallow subsurface water 

connection to the river network. In 

unidirectional wetlands that are not 

connected to the river network through 

surface or shallow subsurface water, the type 

and degree of connectivity varies 

geographically within a watershed and over 

time. Because such wetlands occur on a 

gradient of connectivity, it is difficult to 

generalize about their effects on downstream 

waters. Generalization for this class is further 

complicated because, for certain functions 

(e.g., sediment removal and water storage), 

downstream effects are due to wetland 

isolation, rather than connectivity. The 

literature reviewed does not provide 

sufficient information to evaluate or 

generalize about the degree of connectivity 

(absolute or relative) or the downstream 

effects of wetlands in unidirectional 

landscape settings. However, evaluations of 

individual geographically isolated wetlands 

or groups of geographically isolated wetlands 

could be possible through case-by-case 

analysis. Further, while the review did not 

specifically address other unidirectional 

water bodies, the conclusions apply to these 

water bodies (e.g., ponds and lakes that lack 

surface water inlets) as well, since the same 

principles govern hydrologic connectivity 

between these water bodies and downstream 

waters. 

Section 3 below provides an overview of 

the conceptual framework, with further 

discussion of the key findings for streams, 

riparian and floodplain areas, and 

unidirectional wetlands. 

1. Conceptual Framework Overview 

Connectivity is a foundational concept in 

hydrology and freshwater ecology. The 

structure and function of downstream waters 

are highly dependent on the constituent 

materials contributed by and transported 

through water bodies located elsewhere in 

the watershed. Most of the materials in a 

river, including water, sediment, wood, 

organic matter, nutrients, chemical 

contaminants, and certain organisms, 

originate outside of the river, from upstream 

tributaries, wetlands, or other components of 

the river system, and are transported to the 

river by water movement, wind, or other 

means. Therefore, streams and wetlands 

fundamentally affect river structure and 

function by altering transport of various 

types of materials to the river. This alteration 

of material transport depends on two key 

factors: (1) Connectivity (or isolation) 

between streams, wetlands and rivers that 

enables (or prevents) the movement of 

materials between the system components; 

and (2) functions within streams and 

wetlands that supply, remove, transform, 

provide refuge for, or delay transport of 

materials. 

The ORD Report defines connectivity as 

the degree to which components of a system 

are joined, or connected, by various transport 

mechanisms. Connectivity is determined by 

the characteristics of both the physical 

landscape and the biota of the specific 

system. Isolation is the opposite of 

connectivity; or the degree to which system 

components are not joined. Both connectivity 

and isolation have important effects on 

downstream waters. For example, stream 

channels convey water and channel-forming 

sediment to rivers, whereas wetlands that 

lack output channels can reduce flooding and 

store excess sediment. Materials transport 

connects different ecosystem types, at 

multiple spatial and temporal scales. For 

example, streams flowing into and out of 

wetlands or between lakes form continuous 

or seasonal connections across ecosystem 

boundaries. Similarly, aquatic food webs 

connect terrestrial ecosystems, streams, 

wetlands, and downstream waters. 

Water movement through the river system 

is the primary, but certainly not the only, 

mechanism providing physical connectivity 

within river networks. It provides a 

‘‘hydraulic highway’’ that transports 

chemical, physical, and biological materials 

associated with the water (e.g., sediment, 

woody debris, contaminants, and organisms). 

Because the movement of water is 

fundamental to understanding watershed 

connectivity, Chapter 3 begins with a review 

and an explanation of the hydrologic 

foundation of river systems, and terms and 

concepts used throughout the Report are 

defined. 

Numerous factors influence watershed 

connectivity. Climate, watershed topography, 

soil and aquifer permeability, the number 

and types of contributing waters, their spatial 

distribution in the watershed, interactions 

among aquatic organisms, and human 

alteration of watershed features, among other 

things, can act individually or in concert to 

influence stream and wetland connectivity 

to, and effects on, downstream waters. For 

example, all else being equal, materials 

traveling shorter distances could enter the 

river with less transformation or dilution, 

thus increasing a beneficial or harmful effect. 

In other cases, sequential transformations 

such as nutrient spiraling (defined and 

discussed below) connect distant water 

bodies and produce beneficial effects on 

downstream waters. Infrequent events that 

temporarily connect nearby or distant 

streams or wetlands to rivers also can have 

large, long-lasting effects. Most of the major 

changes in sediment load and river channel 

structure that are critical to maintaining river 

health—including meanders of rivers in 

floodplains and creation of oxbow lakes—are 

a result of large floods that provide 

infrequent, intense connections with more 

distant streams and riparian or floodplain 

waters. 

Based on a review of the peer-reviewed 

scientific literature, the Report identifies five 

functions by which streams, wetlands, and 

open waters influence material transport into 

downstream waters: 

• Source: The net export of materials, such 

as water and food resources 

• Sink: The net removal or storage of 

materials, such as sediment and 

contaminants 

• Refuge: The protection of materials, 

especially organisms 

• Transformation: The transformation of 

materials, especially nutrients and 

chemical contaminants, into different 

physical or chemical forms 

• Lags: The delayed or regulated release of 

materials, such as storm water 

These functions are not static or mutually 

exclusive (e.g., a wetland can be both a 

source of organic matter and a sink for 

nitrogen) and can change over time (e.g., one 

wetland can be a water sink when 

evapotranspiration is high and a water source 

when evapotranspiration is low). Further, 

some functions work in conjunction with 

others. For example, a lag function can 

include transformation of materials prior to 

their delayed release. In a particular stream, 

wetland, or open water, the presence or 

absence of these functions depends upon the 

biota, hydrology, and environmental 

conditions in the watershed. 

When considering effects on downstream 

waters, it is helpful to distinguish between 

actual function and potential function of a 

stream, wetland, or open water. For example, 

a wetland with appropriate conditions for 

denitrification is a potential sink for nitrogen, 

a nutrient that can be a contaminant when 

present in high concentrations. This function 

is conditional; if nitrogen were to enter a 

wetland (from agricultural runoff, for 

example), the wetland has the capacity to 

remove this nitrogen from the water. The 

wetland will not serve this function, 

however, if no nitrogen enters the wetland. 

Even if a stream or wetland is not currently 

serving an actual function, it has the 

potential to provide that function when a 

new material enters it, or when 

environmental conditions change. Thus, 

potential functions play a critical role in 

protecting those waters from future impacts. 


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2. Discussion of Major Conclusions 

A. Streams 

The scientific literature demonstrates that 

streams, individually or cumulatively, exert 

a strong influence on the character and 

functioning of downstream waters. All 

tributary streams, including perennial, 

intermittent, and ephemeral streams, are 

chemically, physically, or biologically 

connected to downstream rivers via channels 

and associated alluvial deposits where water 

and other materials are concentrated, mixed, 

transformed, and transported. Headwater 

streams (headwaters) are the most abundant 

stream type in most river networks, and 

supply most of the water in rivers. In 

addition to water, streams supply sediment, 

wood, organic matter, nutrients, chemical 

contaminants, and many of the organisms 

found in rivers. Streams are biologically 

connected to downstream waters by dispersal 

and migration of aquatic and semi-aquatic 

organisms, including fish, amphibians, 

plants, microorganisms, and invertebrates, 

that use both up- and downstream habitats 

during one or more stages of their life cycles, 

or provide food resources to downstream 

communities. Chemical, physical, and 

biological connections between streams and 

downstream waters interact via processes 

such as nutrient spiraling, in which stream 

communities assimilate and chemically 

transform large quantities of nitrogen and 

other nutrients that would otherwise increase 

nutrient loading downstream. 

Key findings: 

a. Streams are hydrologically connected to 

downstream waters via channels that convey 

surface and subsurface water year-round 

(perennial flow), weekly to seasonally 

(intermittent flow), or only in direct response 

to precipitation (ephemeral flow). Streams 

are the dominant source of water in most 

rivers, and the great majority of tributaries 

are perennial, intermittent, and ephemeral 

headwater streams. For example, headwater 

streams, which are the smallest channels 

where stream flows begin, are the source of 

approximately 60% of the total mean annual 

flow to all northeastern U.S. streams and 

rivers. 

b. Headwaters convey water into local 

storage compartments such as ponds, shallow 

aquifers, or river banks and into regional and 

alluvial aquifers. These local storage 

compartments are important sources of water 

for baseflow in rivers. The ability of streams 

to keep flowing even during dry periods 

typically depends on the delayed (lagged) 

release of local groundwater, also referred to 

as shallow groundwater, originating from 

these water sources, especially in areas with 

shallow groundwater tables and pervious 

subsurfaces. For example, in the 

southwestern United States, short-term 

shallow groundwater storage in alluvial 

floodplain aquifers, with gradual release into 

stream channels by intermittent and 

ephemeral streams, is a major source of 

annual flow in rivers. 

c. Even infrequent flows through 

ephemeral or intermittent channels influence 

fundamental biogeochemical processes by 

connecting the channel and shallow 

groundwater with other landscape elements. 

Infrequent, high-magnitude events are 

especially important for transmitting 

materials from headwater streams in most 

river networks. For example, headwater 

streams, including ephemeral and 

intermittent streams, shape river channels by 

accumulating and gradually or episodically 

releasing stored materials such as sediment 

and large woody debris. These materials 

provide substrate, habitat for aquatic 

organisms, and slow the flow of water 

through channels. 

d. Connectivity between streams and rivers 

provides opportunities for materials, 

including nutrients and chemical 

contaminants, to be sequentially altered as 

they are transported downstream. Although 

highly efficient at transport of water and 

other physical materials, streams are not 

pipes. They are dynamic ecosystems with 

permeable beds and banks that interact with 

terrestrial and aquatic ecosystems above and 

below the surface. The connections formed 

by surface and subsurface streamflows act as 

a series of complex chemical, physical, and 

biological alterations that occur as materials 

move through different parts of the river 

system. The amount and quality of such 

materials that eventually reach a river are 

determined by the aggregate effect of these 

sequential alterations that begin at the source 

waters, which can be at some distance from 

the river. The greater the distance a material 

travels between a particular stream reach and 

the river, the greater the opportunity for that 

material to be altered in intervening stream 

reaches, which can allow for uptake, 

assimilation, or beneficial transformation. 

One example of sequential alteration with 

significant beneficial effects on downstream 

waters is the process of nutrient spiraling, in 

which nutrients entering headwater streams 

are transformed by various aquatic organisms 

and chemical reactions as they are 

transported downstream by streamflow. 

Nutrients which enter the headwater stream 

(e.g., via overland flow) are first removed 

from the water column by streambed algal 

and microbial populations. Fish or insects 

feeding on algae and microbes take up some 

of those nutrients, which are subsequently 

released back to the stream via excretion and 

decomposition, and the cycle is repeated. In 

each phase of the cycling process—from 

dissolved inorganic nutrients in the water 

column, through microbial uptake, 

subsequent transformations through the food 

web, and back to dissolved nutrients in the 

water column—nutrients are subject to 

downstream transport. Stream and wetland 

capacities for nutrient cycling have important 

implications for the form and concentration 

of nutrients exported to downstream waters. 

e. The literature review found strong 

evidence that headwater streams function as 

nitrogen sources (export) and sinks (uptake 

and transformation) for river networks. One 

study estimated that rapid nutrient cycling in 

small streams that were free from agricultural 

or urban impacts removed 20–40% of the 

nitrogen that otherwise would be delivered to 

downstream waters. Nutrients are necessary 

to support aquatic life, but excess nutrients 

create conditions leading to eutrophication 

and hypoxia, in which oxygen concentrations 

fall below the level necessary to sustain most 

within and near-bed animal life. Thus, the 

role of streams in influencing nutrient loads 

can have significant repercussions for 

hypoxic areas in downstream waters. 

f. Headwaters provide critical habitat 

during one or more life cycle stages of many 

organisms capable of moving throughout 

river networks. This review found strong 

evidence that headwaters provide habitat for 

complex life-cycle completion, refuge from 

predators or adverse physical conditions in 

rivers, and reservoirs of genetic- and specieslevel diversity. Use of headwater streams as 

habitat is especially obvious for the many 

species that migrate between small streams 

and marine environments during their life 

cycles (e.g., Pacific and Atlantic salmon, 

American eels, certain lamprey species), and 

the presence of these species within river 

networks provides robust evidence of 

biological connections between headwaters 

and larger rivers. In prairie streams, many 

fishes swim upstream into tributaries to 

release eggs, which develop as they are 

transported downstream. Small streams also 

provide refuge habitat for riverine organisms 

seeking protection from temperature 

extremes, flow extremes, low dissolved 

oxygen, high sediment levels, or the presence 

of predators, parasites, and competitors. 

B. Riparian/Floodplain Waters 

Wetlands and open waters in landscape 

settings that have bidirectional hydrologic 

exchanges with streams or rivers (e.g., 

wetlands and open waters in riparian areas 

and floodplains) are chemically, physically, 

or biologically connected with rivers via the 

export of channel-forming sediment and 

woody debris, temporary storage of local 

groundwater that supports baseflow in rivers, 

and transport of stored organic matter. They 

remove and transform excess nutrients such 

as nitrogen and phosphorus. They provide 

nursery habitat for breeding fish, 

colonization opportunities for stream 

invertebrates, and maturation habitat for 

stream insects. Moreover, wetlands in this 

landscape setting serve an important role in 

the integrity of downstream waters because 

they also act as sinks by retaining 

floodwaters, sediment, nutrients, and 

contaminants that could otherwise negatively 

impact the condition or function of 

downstream waters. 

Key Findings: 

a. Riparian areas act as buffers that are 

among the most effective tools for mitigating 

nonpoint source pollution. The wetland 

literature shows that collectively, riparian 

wetlands improve water quality through 

assimilation, transformation, or sequestration 

of nutrients, sediment and other pollutants— 

such as pesticides and metals—that can affect 

downstream water quality. These pollutants 

enter wetlands via various pathways that 

include various sources such as dry and wet 

atmospheric deposition, some runoff from 

upland agricultural and urban areas, spray 

drift, and subsurface water flows, as well as 

point sources such as outfalls, pipes, and 

ditches. 

b. Riparian and floodplain areas connect 

upland and aquatic environments through 

both surface and subsurface hydrologic flow 

paths. These areas are therefore uniquely 

situated in watersheds to receive and process 


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waters that pass over densely vegetated areas 

and through subsurface zones before reaching 

streams and rivers. When contaminants reach 

a riparian or floodplain area, such materials 

can be sequestered in sediments, assimilated 

into the wetland plants and animals, 

transformed into less harmful forms or 

compounds, or lost to the atmosphere. 

Wetland potential for biogeochemical 

transformations (e.g., denitrification) that can 

improve the quality of water entering streams 

and rivers is influenced by factors present in 

riparian areas and floodplains, including 

anoxic conditions, shallow water tables, slow 

organic matter decomposition, wetland plant 

communities, permeable soils, and complex 

topography. 

c. Riparian and floodplain areas can reduce 

flood peaks by storing and desynchronizing 

floodwaters. They also can contribute to 

maintenance of flow by recharging alluvial 

aquifers. Many studies have documented the 

ability of riparian and floodplain areas to 

reduce flood pulses by storing excess water 

from streams and rivers. One review of 

wetland studies reported that riparian 

wetlands reduced or delayed floods in 23 of 

28 studies. For example, peak discharges 

between upstream and downstream gauging 

stations on the Cache River in Arkansas were 

reduced 10–20% primarily due to floodplain 

water storage. 

d. Riparian and floodplain areas store large 

amounts of sediment and organic matter from 

upland areas before those sediments enter the 

stream. For example, riparian areas have 

been shown to filter 80–90% of sediments 

leaving agricultural fields in North Carolina. 

(A. Cooper, et al., ‘‘Riparian Areas as Filters 

for Agricultural Sediment,’’ Soil Science 

Society of America Proceedings 51:416–420 

(1987); R.B. Daniels, and J.G. Gilliam, 

‘‘Sediment and Chemical Load Reduction by 

Grass and Riparian Filters,’’ Soil Science 

Society of America Journal 60:246–251 

(1996); R.J. Naiman, and H. Decamps, ‘‘The 

Ecology of Interfaces: Riparian Zones,’’ 

Annual Review of Ecology and Systematics 

28:621–658 (1997)). 

e. Ecosystem function within a river 

system is driven by interactions between the 

physical environment and the diverse 

biological communities living within the 

river system. Movements of organisms 

connect aquatic habitats and populations in 

different locations through several processes 

important for the survival of individuals, 

populations, and species, and for the 

functioning of the river ecosystem. For 

example, lateral expansion and contraction of 

the river in its floodplain results in an 

exchange of matter and organisms, including 

fish populations that are adapted to use 

floodplain habitat for feeding and spawning 

during high water. Refuge populations of 

aquatic plants in floodplains can become 

important seed sources for the river network, 

especially if catastrophic flooding scours 

vegetation and seed banks in other parts of 

the channel. Many invertebrates exploit 

temporary hydrologic connections between 

rivers and floodplain wetland habitats, 

moving into these wetlands to feed, 

reproduce, or avoid harsh environmental 

conditions and then returning to the river 

network. Amphibians and aquatic reptiles in 

many parts of the country commonly use 

both streams and wetlands, including 

wetlands in riparian and floodplain areas, to 

hunt, forage, overwinter, rest, or hide from 

predators. 

C. Unidirectional Wetlands 

Wetlands and open waters in landscape 

settings that lack bidirectional hydrologic 

exchanges with downstream waters (e.g., 

many prairie potholes, vernal pools, and 

playa lakes) provide numerous functions that 

can benefit downstream water quality and 

integrity. These functions include storage of 

floodwater; retention and transformation of 

nutrients, metals, and pesticides; and recharge of groundwater sources of river 

baseflow. The functions and effects of this 

diverse group of wetlands, hereafter referred 

to as ‘‘unidirectional wetlands,’’ clearly affect 

the condition of downstream waters if there 

is a surface or shallow subsurface water 

connection to the river network. In 

unidirectional wetlands that are not 

connected to the river network through 

surface or shallow subsurface water, the type 

and degree of connectivity varies 

geographically within a watershed and over 

time. Because such wetlands occur on a 

gradient of connectivity, it is difficult to 

generalize about their effects on downstream 

waters. This evaluation is further 

complicated because, for certain functions 

(e.g., sediment removal and water storage), 

downstream effects arise from wetland 

isolation, rather than connectivity. The 

literature reviewed does not provide 

sufficient information to evaluate or 

generalize about the degree of connectivity 

(absolute or relative) or the downstream 

effects of wetlands in unidirectional 

landscape settings. However, evaluations of 

connectivity of individual wetlands or 

groups of wetlands could be possible through 

case-by-case analysis. Further, while the 

review did not specifically address other 

unidirectional water bodies, the conclusions 

apply to these water bodies (e.g., ponds and 

lakes that lack surface water inlets) as well, 

since the same principals govern hydrologic 

connectivity between these water bodies and 

downstream waters. 

Key Findings: 

a. Water storage by wetlands well outside 

of riparian or floodplain areas can affect 

streamflow. Hydrologic models of prairie 

potholes in the Starkweather Coulee subbasin 

(North Dakota) that drain to Devils Lake 

indicate that increasing the volume of 

pothole storage across the sub-basin by 

approximately 60% caused simulated total 

annual streamflow to decrease 50% during a 

series of dry years and 20% during wet years. 

Similar simulation studies of watersheds that 

feed the Red River of the North in North 

Dakota and Minnesota demonstrated 

qualitatively comparable results, suggesting 

that the ability of potholes to modulate 

streamflow may be widespread across 

portions of the prairie pothole region. This 

work also indicates that reducing wetland 

water storage capacity by connecting 

formerly isolated potholes through ditching 

or drainage to the Devils Lake and Red River 

basins could increase stormflow and 

contribute to downstream flooding. In many 

agricultural areas already crisscrossed by 

extensive drainage systems, total streamflow 

and baseflow are enhanced by directly 

connecting potholes to stream networks. The 

impacts of changing streamflow are 

numerous, including altered flow regime, 

stream geomorphology, habitat, and ecology. 

The presence or absence of an effect of 

prairie pothole water storage on streamflow 

depends on many factors, including patterns 

of precipitation, topography and degree of 

human alteration. For example, in parts of 

the prairie pothole region with low 

precipitation, low stream density, and little 

human alteration, hydrologic connectivity 

between prairie potholes and streams or 

rivers is likely to be low. 

b. Unidirectional wetlands act as sinks and 

transformers for various pollutants, 

especially nutrients, which pose a serious 

pollution problem in the United States. In 

one study, sewage wastewaters were applied 

to forested unidirectional wetlands in Florida 

for a period of 4.5 years. More than 95% of 

the phosphorus, nitrate, ammonium, and 

total nitrogen were removed by the wetland 

during the study period, and 66–86% of the 

nitrate removed was attributed to the process 

of denitrification. In another study, sizeable 

phosphorus retention occurred in 

unidirectional marshes that comprised only 

7% of the lower Lake Okeechobee basin area 

in Florida. A unidirectional bog in 

Massachusetts was reported to sequester 

nearly 80% of nitrogen inputs from various 

sources, including atmospheric deposition, 

and prairie pothole wetlands in the upper 

Midwest were found to remove >80% of the 

nitrate load via denitrification. A large 

unidirectional prairie marsh was found to 

remove 86% of nitrate, 78% of ammonium, 

and 20% of phosphate through assimilation 

and sedimentation, sorption, and other 

mechanisms. Together, these and other 

studies indicate that on-site removal of 

nutrients by unidirectional wetlands is 

significant and geographically widespread. 

The effects of this removal on rivers are 

generally not reported in the literature. 

c. Biological connectivity can occur 

between unidirectional wetlands and 

downstream waters through movement of 

amphibians, aquatic seeds, 

macroinvertebrates, reptiles, and mammals. 

Many species in those groups that use both 

stream and wetland habitats are capable of 

dispersal distances equal to or greater than 

distances between many unidirectional 

wetlands and river networks. Unidirectional 

wetlands can be hydrologically connected 

directly to river networks through channels, 

non-channelized surface flow, or subsurface 

flows. A wetland surrounded by uplands is 

defined as ‘‘geographically isolated.’’ Our 

review found that in some cases, wetland 

types such as vernal pools and coastal 

depressional wetlands are collectively, and 

incorrectly, referred to as geographically 

isolated. Technically, the term 

‘‘geographically isolated’’ should be applied 

only to the particular wetlands within a type 

or class that are completely surrounded by 

uplands. Furthermore, ‘‘geographic isolation’’ 

should not be confused with functional 

isolation, because geographically isolated 

wetlands can still have hydrological and 

biological connections to downstream waters. 


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d. Unidirectional wetlands occur along a 

gradient of hydrologic connectivity-isolation 

with respect to river networks, lakes, or 

marine/estuarine water bodies. This gradient 

includes, for example, wetlands that serve as 

origins for stream channels that have 

permanent surface water connections to the 

river network; wetlands with outlets to 

stream channels that discharge to deep 

groundwater aquifers; geographically isolated 

wetlands that have local groundwater or 

occasional surface water connections to 

downstream waters; and geographically 

isolated wetlands that have minimal 

hydrologic connection to other water bodies 

(but which could include surface and 

subsurface connections to other wetlands). 

The existence of this gradient among 

wetlands of the same type or in the same 

geographic region can make it difficult to 

determine or generalize, from the literature 

alone, the degree to which particular 

wetlands (individually or as classes), 

including geographically isolated wetlands, 

are hydrologically connected. 

e. A related issue is that spatial scale must 

be considered when determining geographic 

isolation. Individual wetlands that are 

geographically isolated could be connected to 

downstream waters when considered as a 

complex (a group of interacting wetlands). 

This principle was demonstrated in a recent 

study that examined a depressional wetland 

complex on the Texas coastal plain. These 

wetlands have been considered as a type of 

geographically isolated wetlands. 

Collectively, however, they are 

geographically and hydrologically connected 

to downstream waters in the area. During an 

almost 4-year study period, nearly 20% of the 

precipitation that fell on the wetland 

complex flowed as surface runoff through an 

intermittent stream to a nearby waterway, the 

Armand Bayou. Thus, wetland complexes 

could have connections to downstream 

waters through stream channels even when 

the individual wetland components are 

geographically isolated. 

3. Closing Comments 

The strong hydrologic connectivity of river 

networks is apparent in the existence of 

stream channels that form the physical 

structure of the network itself. Given the 

discussion above, it is clear that streams and 

rivers are much more than a system of 

physical channels for conveying water and 

other materials downstream, but the presence 

of physical channels is one strong line of 

evidence for surface water connections from 

tributaries, or water bodies of other types, to 

downstream waters. Physical channels are 

defined by continuous bed and bank 

structures, which may include apparent 

disruptions (such as by bedrock outcrops, 

braided channels, flow-through wetlands) 

associated with changes in the material and 

gradient over and through which water flows. 

The continuation of bed and banks down 

gradient from such disruptions is evidence of 

the surface connection with the channel that 

is up gradient of the perceived disruption. 

The structure and function of rivers are 

highly dependent on the constituent 

materials that are stored in and transported 

through them. Most of these materials, 

broadly defined here as any chemical, 

physical, or biological entity, including, but 

not limited to, water, heat energy, sediment, 

wood, organic matter, nutrients, chemical 

contaminants, and organisms, originate 

outside of the river: They originate from 

either the upstream river network or other 

components of the river system, and then are 

transported to the river by water movement 

or other mechanisms. Thus, the fundamental 

way in which streams and wetlands affect 

river structure and function is by altering 

fluxes of materials to the river. The control 

of material fluxes depends on two key 

factors: (1) Functions within streams and 

wetlands that affect material fluxes, and (2) 

connectivity (or isolation) between streams 

and wetlands and rivers that allows (or 

prevents) transport of materials between the 

systems. 

Absence of channels does not, however, 

mean that a wetland or open water is isolated 

or only infrequently connected to 

downstream waters. Areas that are 

infrequently flooded by surface water can be 

connected more regularly through shallow 

groundwater or through dispersal among 

biological populations and communities. 

Such wetlands and open waters also can 

reduce flood peaks by storing flood waters, 

filter large amounts of sediment and 

nutrients from upland areas, influence stream 

geomorphology by providing woody debris 

and sediment, and regulate stream 

temperature. They also serve as sources of 

food for river biota and sources of genetic 

diversity for populations of stream 

invertebrates. 

Unidirectional wetlands can reduce and 

attenuate floods through water storage, and 

can recharge groundwater, thereby 

contributing to stream and river baseflow. 

These wetlands also affect nutrient delivery 

and improve water quality by functioning as 

sources of food and as sinks for metals, 

pesticides, excess nutrients. Biological 

connectivity can also occur between 

unidirectional wetlands and downstream 

waters, through movement of amphibians, 

aquatic insects, aquatic reptiles, migratory 

birds, and riverine mammals that require or 

opportunistically use both river and wetland 

or open water habitats. However, given a 

geographically isolated wetland for which a 

surface water connection cannot be observed, 

it is difficult to assess its degree of 

connectivity with the river network without 

site-specific data. 

Additionally, caution should be used in 

interpreting connectivity for wetlands based 

on their being designated as ‘‘geographically 

isolated’’ since (a) the term can be mistakenly 

applied to a heterogeneous group of wetlands 

that can include wetlands that are not 

geographically isolated, (b) wetlands with 

permanent channels could be miscategorized 

as geographically isolated if the designation 

is based on maps or imagery with inadequate 

spatial resolution, obscured views, etc., and 

(c) wetland complexes could have 

connections to downstream waters through 

stream channels even if individual wetlands 

within the complex are geographically 

isolated. Thus, the term ‘‘geographically 

isolated’’ should only be applied to groups of 

wetlands if they fit the technical definition 

(i.e., they are surrounded by uplands). 

Further, even geographically isolated 

wetlands can be connected to other wetlands 

and downstream waters through groundwater 

connections, occasional spillage, or 

biological connections. Thus, the term 

‘‘geographically isolated’’ should not be used 

to infer lack of hydrologic, chemical, or 

biological connectivity. 

Lastly, to understand the health, behavior, 

and sustainability of downstream waters, 

effects of small water bodies in a watershed 

need to be considered in aggregate. The 

contribution of material by a particular 

stream and wetland might be small, but the 

aggregate contribution by an entire class of 

streams and wetlands (e.g., all ephemeral 

streams in the river network) might be 

substantial. For example, western vernal 

pools typically occur within ‘‘vernal pool 

landscapes’’ or complexes of pools in which 

swales connect pools to each other and to 

seasonal streams, and in which the hydrology 

and ecology are tightly coupled with the 

local and regional geological processes that 

formed them. The vernal pool basins, swales, 

and seasonal streams are part of a single 

surface water and shallow groundwater 

system connected to the river network when 

seasonal precipitation exceeds storage 

capacity of the wetlands. Since rivers 

develop and respond over time and are 

functions of the whole watershed, 

understanding the integration of 

contributions and effects over time is also 

necessary to have an accurate understanding 

of the system, taking into account the 

duration and frequency of material export 

and delivery to downstream waters. In 

addition, when considering the effect of an 

individual stream or wetland, it is important 

to include the cumulative effect of all 

materials that originate from it, rather than 

each material individually, to understand 

that water body’s influence on downstream 

waters. 

Part II: Additional Scientific Support 

i. Tributaries 

The agencies propose that all waters that 

meet the proposed definition of tributary are 

‘‘waters of the United States’’ because they 

meet Justice Kennedy’s test for jurisdiction 

under Rapanos. In other words, the agencies 

are asserting that all tributaries have a 

significant nexus with traditional navigable 

waters, interstate waters, and/or the 

territorial seas. EPA and the Corps’ 

longstanding definition of ‘‘waters of the 

United States’’ has included tributaries. That 

regulation was based on the agencies’ historic 

view of the scope of the CWA and the general 

scientific understanding about the ecological 

and hydrological relationship between 

waters. 

Tributaries have a substantial impact on 

the chemical, physical, or biological integrity 

of waters into which they eventually flow— 

including traditional navigable waters, 

interstate waters, and the territorial seas. The 

great majority of tributaries are headwater 

streams, and whether they are perennial, 

intermittent, or ephemeral, they play an 

important role in the transport of water, 

sediments, organic matter, pollutants, 

nutrients, and organisms to downstream 

environments. Tributaries serve to store 


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water (thereby reducing flooding), provide 

biogeochemical functions that help maintain 

water quality, trap and transport sediments, 

transport, store and modify pollutants, 

provide habitat for plants and animals, and 

sustain the biological productivity of 

downstream rivers, lakes and estuaries. 

These conclusions are strongly supported in 

the scientific literature, as discussed below. 

Headwater streams are the smallest 

channels where stream flows begin, and often 

occur at the outer rims of a watershed. 

Typically these are first-order streams (i.e., 

they do not have any other streams flowing 

into them). However, headwater streams can 

include streams with multiple tributaries 

flowing into them and can be perennial, 

intermittent or ephemeral, but are still 

located near the channel origins of the 

tributary system in a watershed. 

Protection of tributaries under the CWA is 

critically important because they serve many 

important functions which directly influence 

the integrity of downstream waters. It is 

necessary to regulate the entire tributary 

system to fulfill the objective of the CWA, 

because discharges of pollutants into the 

tributary system adversely affect the 

chemical, physical, or biological integrity of 

these waters. For example, destruction or 

modification of headwater streams has been 

shown to affect the integrity of downstream 

waters, in part through changes in hydrology, 

chemistry and stream biota. M.C. Freeman, et 

al., ‘‘Hydrologic Connectivity and the 

Contribution of Stream Headwaters to 

Ecological Integrity at Regional Scales,’’ 

Journal of the American Water Resources 

Association 43:5–14. (2007); M.S. Wipfli., et 

al., ‘‘Ecological Linkages between 

Headwaters and Downstream Ecosystems: 

Transport of Organic Matter, Invertebrates, 

and Wood Down Headwater Channels,’’ 

Journal of the American Water Resources 

Association 43:72–85 (2007). Additionally, 

activities such as discharging a pollutant into 

one part of the tributary system are welldocumented to affect, at times, other parts of 

the system, even when the point of discharge 

is far upstream from the navigable water that 

experiences the effect of the discharge. In 

order to protect traditional navigable waters, 

interstate waters, and the territorial seas it is 

also critically important to protect tributaries 

as defined in today’s proposal that are 

upstream from those waters. 

A. The Agencies Have Concluded That 

Tributaries, as Defined in the Proposed Rule, 

Have a Significant Nexus 

The scientific literature documents that 

tributary streams, including perennial, 

intermittent, and ephemeral streams, and 

certain categories of ditches are integral parts 

of river networks because they are directly 

connected to rivers via permanent surface 

features (channels and associated alluvial 

deposits) that concentrate, mix, transform, 

and transport water and other materials, 

including food resources, downstream. 

Tributaries transport, and often transform, 

chemical elements and compounds, such as 

nutrients, ions, dissolved and particulate 

organic matter and contaminants, influencing 

water quality, sediment deposition, nutrient 

availability, and biotic functions in rivers. 

Streams also are biologically connected to 

downstream waters by dispersal and 

migration, processes which have critical 

implications for aquatic populations of 

organisms that use both headwater and river 

or open water habitats to complete their life 

cycles or maintain viable populations. The 

scientific literature clearly demonstrates that 

cumulatively, streams exert strong influence 

on the character and functioning of rivers. In 

light of these well documented connections 

and functions, the agencies concluded that 

tributaries, as defined, alone or in 

combination with other tributaries in a 

watershed, significantly affect the chemical, 

physical, or biological integrity of a 

traditional navigable water, interstate water, 

or the territorial seas. The scientific literature 

supports this conclusion for ephemeral 

tributaries, as well as for intermittent and 

perennial tributaries; for tributaries both near 

to and far from the downstream traditional 

navigable water, interstate water, or the 

territorial seas; and for natural tributaries or 

man-altered tributaries, which may include 

certain ditches and canals. 

The discussion below summarizes the key 

points in the literature regarding the 

chemical, physical, and biological 

connections and functions of tributaries that 

significantly affect downstream waters. In 

addition, the evidence regarding headwater 

streams and non-perennial streams, types of 

tributaries whose important functional 

relationships to downstream traditional 

navigable waters and interstate waters might 

not be obvious, is summarized. The scientific 

literature does not use legal terms like 

‘‘traditional navigable water,’’ ‘‘interstate 

water,’’ or ‘‘the territorial seas.’’ Rather, the 

literature assesses tributaries in terms of their 

connections to and effects on downstream 

waters in a watershed. While the agencies 

define as ‘‘waters of the United States’’ 

tributaries only in watersheds which drain to 

a traditional navigable water, interstate 

water, or the territorial seas, that distinction 

does not affect the conclusions of the 

scientific literature with respect to the effects 

of tributaries on downstream waters. 

B. Tributaries Significantly Affect the 

Physical Integrity of (a)(1) Through (a)(3) 

Waters 

Tributaries, even when seasonally dry, are 

the dominant source of water in most rivers, 

rather than direct precipitation or 

groundwater input to main stem river 

segments. See, e.g., Report at 4–3 (citing T.C. 

Winter, 2007, ‘‘The role of groundwater in 

generating streamflow in headwater areas 

and in maintaining base flow,’’ Journal of the 

American Water Resources Association 

43:15–25; P.A. Bukaveckas, ‘‘Rivers,’’ in G.E. 

Likens, ed., Encyclopedia of Inland Waters, 

Vol. 1 (Elsevier: Oxford, 2009)). Distant 

headwaters with stronger connections to 

groundwater or consistently higher 

precipitation levels than downstream reaches 

contribute more water to downstream rivers. 

In the northeastern United States headwater 

streams contribute greater than 60% of the 

water volume in larger tributaries, including 

navigable rivers. See, e.g., id. (citing R.B. 

Alexander, et. al., ‘‘The role of headwater 

streams in downstream water quality,’’ 

Journal of the American Water Resources 

Association 43:41–59 (2007)). The 

contributions of tributaries to river flows are 

often readily measured or observed, 

especially immediately below confluences, 

where tributary flows increase the flow 

volume and alter physical conditions, such 

as water temperature, in the main stream. 

The physical effects of tributaries are 

particularly clear after intense rainfall occurs 

over only the upper tributary reaches of a 

river network. For example, a study of 

ephemeral tributaries to the Rio Grande in 

New Mexico found that after a storm event 

contributions of the stormflow from 

ephemeral tributaries accounted for 76% of 

the flow of the Rio Grande. See, e.g., id. at 

4–5 (citing E.R. Vivoni, et. al., ‘‘Analysis of 

a Monsoon Flood Event in an Ephemeral 

Tributary and Its Downstream Hydrologic 

Effects,’’ Water Resources Research 

42:W03404 (2006)). A key effect of tributaries 

on the hydrologic response of river networks 

to storm events is dispersion, or the 

spreading of water output from a drainage 

basin over time. Hydrologic dispersion of 

connected tributaries influence the timing 

and volume of water reaching a river network 

outlet. See, e.g., id. at 4–5 to 4–6 (citing P. 

M. Saco and P. Kumar, ‘‘Kinematic 

dispersion in stream networks coupling 

hydraulics and network geometry,’’ Water 

Resources Research 38:1244 (2002)). 

Tributaries also can reduce the amount of 

water that reaches downstream rivers and 

minimize downstream flooding, often 

through infiltration or seepage through 

channel beds and banks or through 

evapotranspiration. See, e.g., id. at 4–8 (citing 

S.K. Hamilton, et al., ‘‘Persistence of Aquatic 

Refugia between Flow Pulses in a Dryland 

River System (Cooper Creek, Australia),’’ 

Limnology and Oceanography 50:743–754 

(2005); J.F. Costelloe, et.al., ‘‘Determining 

Loss Characteristics of Arid Zone River 

Waterbodies,’’ River Research and 

Applications 23:715–731 (2007)). 

One of the primary functions of tributaries 

is transporting sediment to downstream 

waters. Tributaries, particularly headwaters, 

shape and maintain river channels by 

accumulating and gradually or episodically 

releasing sediment and large woody debris 

into river channels. Sediment transport is 

also clearly provided by ephemeral streams. 

Effects of the releases of sediment and large 

woody debris are especially evident at 

tributary-river confluences, where 

discontinuities in flow regime and 

temperature clearly demonstrate physical 

alteration of river structure and function by 

headwater streams. Report at 4–10, 4–14. 

Sediment movement is critical for 

maintaining the river network, including 

rivers that are considered to be traditional 

navigable waters, as fluvial (produced by the 

action of a river or stream) sediments are 

eroded from some channel segments, and 

deposited in others downstream to form 

channel features, stream and riparian habitat 

which supports the biological communities 

resident downstream, and influence the river 

hydrodynamics. See, e.g., J.L. Florsheim, et 

al., ‘‘Bank Erosion as a Desirable Attribute of 

Rivers,’’ Bioscience 58:519–29 (2008); Report 

at 4–9 (citing M. Church, ‘‘Bed material 

transport and the morphology of alluvial 

river channels,’’ Annual Review of Earth and 


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Planetary Sciences: 325–354 (2006)). While 

essential to river systems, too much sediment 

can impair ecological integrity by filling 

interstitial spaces, blocking sunlight 

transmission through the water column, and 

increasing contaminant and nutrient 

concentrations. Report at 4–9 (citing P.J. 

Wood and P.D. Armitage, ‘‘Biological Effects 

of Fine Sediment in the Lotic Environment,’’ 

Environmental Management 21:203–217 

(1997)). Over sedimentation thus can reduce 

photosynthesis and primary productivity 

within the stream network and otherwise 

have harmful effects on downstream biota, 

including on the health and abundance of 

fish, aquatic macrophytes (plants), and 

aquatic macroinvertebrates that inhabit 

downstream waters. See, e.g., Wood and 

Armitage 1997. Headwater streams tend to 

trap and store sediments behind large 

structures, such as boulders and trees, that 

are transported downstream only during 

infrequent large storm events. See Report at 

4–10, 4–12 (citing L.E. Benda, and T.W. 

Cundy, ‘‘Predicting deposition of debris 

flows in mountain channels,’’ Canadian 

Geotechnical Journal 27:409–417 (1990); T. 

Gomi and R.C. Sidle, ‘‘Bed load transport in 

managed steep-gradient headwater streams of 

southeastern Alaska,’’ Water Resources 

Research 39:1336 (2003); L.E. Benda, et al., 

‘‘Geomorphology of steepland headwaters: 

The transition from hillslopes to channels,’’ 

Journal of the American Water Resources 

Association 41:835–851 (2005); P.E. Bigelow, 

et al., ‘‘On Debris Flows, River networks, and 

the Spatial Structure of Channel 

Morphology,’’ Forest Science 53:220–238 

(2007); J.P.R. Gooderham, et al., ‘‘Upstream 

Heterogeneous Zones: Small Stream Systems 

Structured by a Lack of Competence?’’ 

Journal of the North American Benthological 

Society 26:365–374 (2007)). 

Tributaries can greatly influence water 

temperatures in tributary networks. This is 

important because water temperature is a 

critical factor governing the distribution and 

growth of aquatic life, both directly (through 

its effects on organisms) and indirectly 

(through its effects on other physiochemical 

properties, such as dissolved oxygen and 

suspended solids). Id. at 4–13 (citing J.D. 

Allan, Stream Ecology—Structure and 

Function of Running Waters (New York, NY: 

Chapman & Hall, 1995)). For instance, water 

temperature controls metabolism and level of 

activity in cold-blooded species like fish, 

amphibians, and aquatic invertebrates. See, 

e.g., G.G. Ice, ‘‘Chapter 3: Stream 

Temperature and Dissolved Oxygen,’’ in J.D. 

Stednick, ed., Hydrologic and Biological 

Responses to Forest Practices (Springer, 

2008). Temperature can also control the 

amount of dissolved oxygen in streams, as 

colder water holds more dissolved oxygen, 

which fish and other fauna need to breathe. 

Connections between tributaries and 

downstream rivers can affect water 

temperature in river networks. See, e.g., 

Report at 4–13 (citing S. Knispel, and E. 

Castella, ‘‘Disruption of a Longitudinal 

Pattern in Environmental Factors and 

Benthic Fauna by a Glacial Tributary,’’ 

Freshwater Biology 48:604–618 (2003); S.P. 

Rice, et al., ‘‘The Ecological Importance of 

Tributaries and Confluences,’’ in S.P. Rice, et 

al., ed., River Confluences, Tributaries and 

the Fluvial Network, (Chichester, UK: John 

Wiley & Sons, 2008), pp. 209–242)). In 

particular, tributaries provide both cold and 

warm water refuge habitats that are critical 

for protecting aquatic life. Id. at 4–32. 

Because headwater tributaries often depend 

on groundwater inputs, temperatures in these 

systems tend to be warmer in the winter 

(when groundwater is warmer than ambient 

temperatures) and colder in the summer 

(when groundwater is colder than ambient 

temperatures) relative to downstream waters. 

Id. (citing G. Power, et al., ‘‘Groundwater and 

Fish: Insights from Northern North America,’’ 

Hydrological Processes 13:401–422 (1999)). 

Thus tributaries provide organisms with both 

warm water and coldwater refuges at 

different times of the year. Id. (citing R.A. 

Curry, et al., ‘‘Use of Small Streams by Young 

Brook Trout Spawned in a Lake,’’ 

Transactions of the American Fisheries 

Society 126:77–83 (1997); C.V. Baxter, and 

F.R. Hauer, ‘‘Geomorphology, Hyporheic 

Exchange and Selection of Spawning Habitat 

by Bull Trout (Salvelinus confluentus),’’ 

Canadian Journal of Fisheries and Aquatic 

Sciences 57: 1470–1481 (2000); T.R. Labbe, 

and K.D. Fausch, ‘‘Dynamics of Intermittent 

Stream Habitat Regulate Persistence of a 

Threatened Fish at Multiple Scales,’’ 

Ecological Applications 10:1774–1791 

(2000); M.J. Bradford, et al., ‘‘Ecology of 

Juvenile Chinook Salmon in a Small Nonnatal Stream of the Yukon River Drainage 

and the Role of Ice Conditions on Their 

Distribution and Survival,’’ Canadian Journal 

of Zoology-Revue Canadienne De Zoologie 

79:2043–2054 (2001)). For example, when 

temperature conditions in downstream 

waters are adverse, fish can travel upstream 

and use tributaries as refuge habitat. Id. 

(citing Curry et al. 1997; M.A. Cairns, et al., 

‘‘Influence of Summer Stream Temperatures 

on Black Spot Infestation of Juvenile Coho 

Salmon in the Oregon Coast Range,’’ 

Transactions of the American Fisheries 

Society 134:1471–1479 (2005)). Tributaries 

also help buffer temperatures in downstream 

waters. Id. at 4–13 to 4–14 (citing D. Caissie, 

‘‘The thermal regime of rivers: A review,’’ 

Freshwater Biology 51:1389–1406 (2006). 

Temperatures in tributaries affect 

downstream water temperature many 

kilometers away. Id. at 4–14 (citing B. 

Gardner, and P.J. Sullivan, ‘‘Spatial and 

Temporal Stream Temperature Prediction: 

Modeling Nonstationary Temporal 

Covariance Structures,’’ Water Resources 

Research 40:W01102 doi (2004); B.R. 

Johnson, et al., ‘‘Use of Spatially Explicit 

Physicochemical Data to Measure 

Downstream Impacts of Headwater Stream 

Disturbance,’’ Water Resources Research 

46:W09526 (2010)). 

C. Tributaries Significantly Affect the 

Chemical Integrity of (a)(1) Through (a)(3) 

Waters 

Tributaries transform and export 

significant amounts of nutrients and carbon 

to downstream waters, serving important 

source functions that greatly influence the 

chemical integrity of downstream waters. 

Organic carbon, in both dissolved and 

particulate forms, exported from tributaries is 

consumed by downstream organisms. The 

organic carbon that is exported downstream 

thus supports biological activity (including 

metabolism) throughout the river network. 

See, e.g., Report at 4–22 (citing S.G. Fisher 

and G.E. Likens, ‘‘Energy Flow in Bear Brook, 

New Hampshire: An Integrative Approach to 

Stream Ecosystem Metabolism,’’ Ecological 

Monographs 43: 421–439 (1973); J.L. Meyer, 

‘‘The Microbial Loop in Flowing Waters,’’ 

Microbial Ecology 28:195–199 (1994); J.B. 

Wallace, et al. ‘‘Multiple Trophic Levels of a 

Forest Stream Linked to Terrestrial Litter 

Inputs,’’ Science 277:102–104 (1997); R.O. 

Hall and J.L. Meyer, ‘‘The Trophic 

Significance of Bacteria in a Detritus-Based 

Stream Food Web,’’ Ecology 79:1995–2012 

(1998); R.O. Hall, et al., ‘‘Organic Matter 

Flow in Stream Food Webs with Reduced 

Detrital Resource Base,’’ Ecology 81:3445– 

3463 (2000); C. Augspurger, et al., ‘‘Tracking 

Carbon Flow in a 2-Week-Old and 6-WeekOld Stream Biofilm Food Web,’’ Limnology 

and Oceanography 53:642–650 (2008)). 

Much or most of the organic carbon that is 

exported from tributaries has been altered 

either physically or chemically by ecosystem 

processes within the tributary streams, 

particularly by headwater streams. 

Nutrient export from tributaries has a large 

effect on downstream water quality, as excess 

nutrients from surface runoff from lawns and 

agricultural fields can cause algal blooms that 

reduce dissolved oxygen levels and increase 

turbidity in rivers, lakes, estuaries, and 

territorial seas. Water low in dissolved 

oxygen cannot support aquatic life; it is 

widely-recognized that this phenomenon has 

resulted in the devastation of commercial 

and recreational fisheries in the northern 

Gulf of Mexico. Committee on Environment 

and Natural Resources, Integrated 

Assessment of Hypoxia in the Northern Gulf 

of Mexico (Washington, DC: National Science 

and Technology Council, 2000). The amount 

of nitrogen that is exported downstream 

varies depending on stream size, and how 

much nitrogen is present in the system. 

Nitrogen loss is greater in smaller, shallow 

streams, most likely because denitrification 

and settling of nitrogen particles occur at 

slower rates in deeper channels. Report at 4– 

16 (citing R.G. Alexander, et al., ‘‘Effect of 

Stream Channel Size on the Delivery of 

Nitrogen to the Gulf of Mexico,’’ Nature 

403:758–761 (2000)). At low loading rates, 

the biotic removal of dissolved nitrogen from 

water is high and occurs primarily in small 

tributaries, reducing the loading to larger 

tributaries and rivers downstream. At high 

nitrogen loading rates, tributaries become 

nitrogen saturated and are not effectively able 

to remove nitrogen, resulting in high nitrogen 

export to rivers. Id. at 4–18 (citing P.J. 

Mulholland, et al., ‘‘Stream Denitrification 

across Biomes and Its Response to 

Anthropogenic Nitrate Loading,’’ Nature 

452:202–205 (2008)). The transport of 

nitrogen and phosphorus downstream has 

also been well-documented, particularly in 

the cases of the Gulf of Mexico and the 

Chesapeake Bay. Tributary streams in the 

uppermost portions of the Gulf and Bay 

watersheds transport the majority of 

nutrients to the downstream waters; an 

estimated 85% of nitrogen arriving at the 

hypoxic zone in the Gulf originates in the 


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upper Mississippi (north of Cairo, Illinois) 

and the Ohio River Basins. D. Goolsby, et al., 

Topic Report 3, Flux and Sources of 

Nutrients in the Mississippi-Atchafalaya 

River Basin (Washington, DC: National 

Science and Technology Council Committee 

on Environment and Natural Resources, 

1999). The export of nutrients from streams 

in the Mississippi River Basin has an effect 

on anoxia, or low oxygen levels, in the Gulf. 

Report at 4–17 (citing N.N. Rabalais, et al., 

‘‘Gulf of Mexico Hypoxia, a.k.a. ‘the Dead 

Zone,’ ’’ Annual Review of Ecology and 

Systematics 33:235–263 (2002)). Similarly, 

nutrient loads from virtually the entire 

64,000 square mile watershed affect water 

quality in the Chesapeake Bay. Simulation 

tools have been used to determine the 

nutrient and sediment load reductions that 

must be made at many different points 

throughout the entire watershed in order to 

achieve acceptable water quality in the 

mainstem of the Bay. These reductions 

included specific annual nitrogen caps on the 

upper reaches of the Susquehanna River in 

New York State, more than 400 miles from 

the mouth of the Chesapeake Bay. See e.g., 

U.S. Environmental Protection Agency (EPA), 

Region III, Chesapeake Bay Program Office, 

Setting and Allocating the Chesapeake Bay 

Basin Nutrient and Sediment Loads: The 

Collaborative Process, Technical Tools and 

Innovative Approaches, EPA 903–R–03–007 

(Washington, DC: EPA, 2003); Rabalais et al. 

2002. 

Although tributaries export nutrients, 

carbon, and contaminants downstream, they 

also transform these substances. Phosphorous 

and nitrogen arrive at downstream waters 

having already been cycled, or taken up and 

transformed by living organisms, many times 

in headwater and smaller tributaries. Report 

at 4–19 to 4–20, 6–3 to 6–4 (citing J.R. 

Webster, and B.C. Patten, ‘‘Effects of 

watershed perturbation on stream potassium 

and calcium dynamics,’’ Ecological 

Monographs 49:51–72 (1979); J.D. Newbold, 

et al., ‘‘Measuring nutrient spiraling in 

streams,’’ Canadian Journal of Fisheries and 

Aquatic Sciences 38:860–863 (1981); J. 

Elwood, et al., ‘‘Resource spiraling: An 

operational paradigm for analyzing lotic 

ecosystems,’’ in T.D. Fontaine and S.M. 

Bartell, ed., Dynamics of Lotic Ecosystems 

(Ann Arbor, MI: Ann Arbor Science, 1983), 

pp. 3–23; S.H. Ensign, and M.W. Doyle, 

‘‘Nutrient Spiraling in Streams and River 

Networks,’’ Journal of Geophysical ResearchBiogeosciences 111:G04009 (2006)). In 

addition, some of the nutrient that is taken 

up as readily available inorganic forms is 

released back to the water as organic forms 

that are less available for biotic uptake. Id. at 

4–20 (citing P.J. Mulholland, et al., 

‘‘Production of Soluble, High Molecular 

Weight Phosphorus and Its Subsequent 

Uptake by Stream Detritus,’’ Verhandlungen 

des Internationalen Verein Limnologie 

23:1190–1197 (1988); S.P. Seitzinger, et al., 

‘‘Bioavailability of DON from Natural and 

Anthropogenic Sources to Estuarine 

Plankton,’’ Limnology and Oceanography 

47:353–366 (2002)). Similarly, nutrient 

incorporated into particulates is not entirely 

regenerated, but accumulates in 

longitudinally increasing particulate loads 

(i.e. increases moving downstream). Id. at 4– 

20 (citing J.L Merriam, et al., ‘‘Characterizing 

Nitrogen Dynamics, Retention and Transport 

in a Tropical Rainforest Stream Using an in 

situ N–15 Addition,’’ Freshwater Biology 

47:143–160 (2002); M.R. Whiles, and W.K. 

Dodds, ‘‘Relationships between Stream Size, 

Suspended Particles, and Filter-Feeding 

Macroinvertebrates in a Great Plains Drainage 

Network,’’ Journal of Environmental Quality 

31:1589–1600 (2002); R.O. Hall, et al., 

‘‘Hydrologic Control of Nitrogen Removal, 

Storage, and Export in a Mountain Stream,’’ 

Limnology and Oceanography 54:2128–2142 

(2009)). Headwater streams have seasonal 

cycles in the concentrations of phosphorous 

and nitrogen that are delivered downstream 

by accumulating nutrient derived from 

temporarily growing streambed biomass. Id. 

(citing P.J. Mulholland, and W.R. Hill, 

‘‘Seasonal Patterns in Streamwater Nutrient 

and Dissolved Organic Carbon 

Concentrations: Separating Catchment Flow 

Path and In-Stream Effects,’’ Water Resources 

Research 33:1297–1306 (1997); P.J. 

Mulholland, ‘‘The Importance of In-stream 

Uptake for Regulating Stream Concentrations 

and Outputs of N and P from a Forested 

Watershed: Evidence from Long-Term 

Chemistry Records for Walker Branch 

Watershed,’’ Biogeochemistry 70:403–426 

(2004)). Such variations have been 

demonstrated to affect downstream 

productivity. Id. (citing P.J. Mulholland, et 

al., ‘‘Longitudinal Patterns of Nutrient 

Cycling and Periphyton Characteristics in 

Streams: a Test of Upstream-Downstream 

Linkage,’’ Journal of the North American 

Benthological Society 14:357–370 (1995)). 

Nitrification, the microbial transformation of 

ammonium to nitrate, affects the form of 

downstream nutrient delivery. Nitrification 

occurs naturally in undisturbed headwater 

streams, but increases sharply in response to 

ammonium inputs, thereby reducing 

potential ammonium toxicity from pollutant 

inputs. Id. (citing Newbold, et al., 

‘‘Phosphorus Dynamics in a Woodland 

Stream Ecosystem: a Study of Nutrient 

Spiraling,’’ Ecology 64:1249–1265 (1983); 

S.C. Chapra, Surface Water Quality Modeling 

(McGraw-Hill, 1996); E.S. Bernhardt, et al., 

‘‘Whole-system Estimates of Nitrification and 

Nitrate Uptake in Streams of the Hubbard 

Brook Experimental Forest,’’ Ecosystems 

5:419–430 (2002)). Denitrification, the 

removal of nitrate from streamwater through 

transformation to atmospheric nitrogen, is 

widespread among headwater streams; 

research indicates that small, unimpacted 

tributaries can reduce up to 40% of 

downstream nitrogen delivery through 

denitrification. Id. at 4–20 to 4–21 (citing P.J. 

Mulholland, et al., ‘‘Stream Denitrification 

across Biomes and Its Response to 

Anthropogenic Nitrate Loading,’’ Nature 

452:202–205 (2008)). Small tributaries also 

affect the downstream delivery of nutrients 

through abiotic processes. Streams can 

reduce phosphorus concentrations through 

sorption (i.e., ‘‘sticking’’) to stream 

sediments. Id. at 4–21 (citing J.L. Meyer, 

‘‘The Role of Sediments and Bryophytes in 

Phosphorus Dynamics in a Headwater Stream 

Ecosystem,’’ Limnology and Oceanography 

24:365–375 (1979)). This is particularly 

beneficial to downstream chemical integrity 

where phosphorus sorbs to contaminants 

such as metal hydroxide precipitates. Id. 

(citing J.A. Simmons, ‘‘Phosphorus Removal 

by Sediment in Streams Contaminated with 

Acid Mine Drainage,’’ Water Air and Soil 

Pollution 209:123–132 (2010)). 

Tributaries also store significant amounts 

of nutrients and carbon, functioning as 

important sinks (lags) for river networks so 

that they do not reach downstream 

traditional navigable waters, interstate 

waters, or the territorial seas. Small tributary 

streams in particular often have the greatest 

effect on downstream water quality, in terms 

of storage and reducing inputs to 

downstream waters. For instance, uptake and 

transformation of inorganic nitrogen often 

occurs most rapidly in the smallest 

tributaries. See, e.g., id. at 4–18 (citing B.J. 

Peterson, et al., ‘‘Control of Nitrogen Export 

from Watersheds by Headwater Streams,’’ 

Science 292:86–90 (2001)). Small tributaries 

affect the downstream delivery of nutrients 

such as phosphorus through abiotic 

processes; such streams can reduce 

phosphorus concentrations by sorption to 

stream sediments. 

Tributaries can also serve as a temporary 

or permanent source or sink for 

contaminants, for instance substances like 

metals, sodium, and even dead fish carcasses 

that adversely affect organisms when 

occurring at excessive or elevated 

concentrations to reduce the amounts that 

reach downstream traditional navigable 

waters, interstate waters, or the territorial 

seas. The transport of contaminants to 

downstream waters can impact water quality 

downstream, if they are not stored in 

tributaries. See, e.g., id. at 4–26 (citing X. 

Wang, et al., ‘‘Water Quality Changes as a 

Result of Coalbed Methane Development in 

a Rocky Mountain Watershed,’’ Journal of the 

American Water Resources Association 

43:1383–1399 (2007)). Tributaries can also 

serve as at least a temporary sink for 

contaminants that would otherwise impair 

downstream water quality. See, e.g., id. at 

133–134 (citing W.L. Graf, Plutonium and the 

Rio Grande: Environmental Change and 

Contamination in the Nuclear Age (New 

York: Oxford University Press, 1994)). 

The distances and extent of metal 

contaminant transport was shown in separate 

studies in the upper Arkansas River in 

Colorado, and Clark Fork River in Montana, 

where past mining activities impacted the 

headwater tributaries. River bed sediments 

showed that metals originating from the 

mining and smelting areas in the headwaters 

were reaching water bodies up to 550 km 

downstream. Id. at 4–26 to 4–27 (citing E.V. 

Axtmann, and S.N. Luoma, ‘‘Large-scale 

Distribution of Metal Contamination in the 

Fine-grained Sediments of the Clark Fork 

River, Montana, USA,’’ Applied 

Geochemistry 6:75–88 (1991); B.A. Kimball, 

et al., ‘‘Effects of Colloids on Metal Transport 

in a River Receiving Acid Mine Drainage, 

Upper Arkansas River, Colorado, USA,’’ 

Applied Geochemistry 10:285–306 (1995)). 

Military studies of the distribution, 

transport, and storage of radionuclides (e.g., 

plutonium, thorium, uranium) have provided 

convincing evidence for distant chemical 


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connectivity in river networks because the 

natural occurrence of radionuclides is 

extremely rare. From 1942 to 1952, prior to 

the full understanding of the risks of 

radionuclides to human health and the 

environment, plutonium dissolved in acid 

was discharged untreated into several 

intermittent headwater streams that flow into 

the Rio Grande at the Los Alamos National 

Laboratory, New Mexico. Id. at 4–28 (citing 

W.L. Graf, Plutonium and the Rio Grande: 

Environmental Change and Contamination in 

the Nuclear Age (New York: Oxford 

University Press, 1994); S.L. Reneau, et al., 

‘‘Geomorphic Controls on Contaminant 

Distribution along an Ephemeral Stream,’’ 

Earth Surface Processes and Landforms 

29:1209–1223 (2004)). Also during this time, 

nuclear weapons testing occurred west of the 

upper Rio Grande near Socorro, New Mexico 

(Trinity blast site) and in Nevada, where 

fallout occurred on mountainous areas with 

thin soils that are readily transported to 

headwater streams in the upper Rio Grande 

basin. The distribution of plutonium within 

the Rio Grande illustrates how headwater 

streams transport and store contaminated 

sediment that has entered the basin through 

fallout and from direct discharge. Los Alamos 

Canyon, while only representing 0.4% of the 

drainage area at its confluence with the Rio 

Grande, had a mean annual bedload 

contribution of plutonium almost seven 

times that of the mainstem. Id. (citing Graf 

1994). Much of the bedload contribution 

occurred sporadically during intense storms 

that were out of phase with flooding on the 

upper Rio Grande. Total estimated 

contributions of plutonium between the two 

sources to the Rio Grande were 

approximately 90% from fallout to the 

landscape and 10% from direct effluent 

discharge at Los Alamos National Laboratory. 

Id. (citing Graf 1994). 

C. Tributaries Significantly Affect the 

Biological Integrity of (a)(1) Through (a)(3) 

Waters 

Tributaries are biologically linked to 

downstream waters through the movement of 

living organisms or their reproductive 

propagules, such as eggs or seeds. For 

organisms that drift with water flow, 

biological connections depend on 

hydrological connections. However, many 

aquatic organisms are capable of active 

movement with or against water flow, and 

others disperse actively or passively over 

land by walking, flying, drifting, or 

‘‘hitchhiking.’’ All of these different types of 

movement form the basis of biological 

connectivity between headwater tributaries 

and downstream waters. 

Headwater tributaries increase the amount 

and quality of habitat available to aquatic 

organisms. Under adverse conditions, small 

tributaries provide safe refuge, allowing 

organisms to persist and recolonize 

downstream areas once adverse conditions 

have abated. See, e.g., Report at 4–29 (citing 

J.L. Meyer and J.B. Wallace, ‘‘Lost Linkages 

and Lotic Ecology: Rediscovering Small 

Streams,’’ Pages 295–317 in M.C. Press, N. J. 

Huntly, and S. Levin, editors. Ecology: 

Achievement and Challenge (Oxford, UK: 

Blackwell Science, 2001); A. Meyer et al., 

‘‘The Effect of Low Flow and Stream Drying 

on the Distribution and Relative Abundance 

of the Alien Amphipod, Echinogammarus 

berilloni (Catta, 1878) in a Karstic Stream 

System (Westphalia, Germany),’’ Crustaceana 

77:909–922 (2004); A.D. Huryn et al., 

‘‘Landscape Heterogeneity and the 

Biodiversity of Arctic Stream Communities: 

A Habitat Template Analysis,’’ Canadian 

Journal of Fisheries and Aquatic Sciences 

62:1905–1919 (2005)). Use of tributaries by 

salmon and other anadromous fish for 

spawning is well-documented, but even nonmigratory species can travel great distances 

within the river and tributary networks. See, 

e.g., id. at 4–31 (citing O.T. Gorman, 

‘‘Assemblage Organization of Stream Fishes: 

The Effects of Rivers on Adventitious 

Streams,’’ American Naturalist 128(4): 611– 

616 (1986); A. L. Sheldon, ‘‘Conservation of 

Stream Fishes: Patterns of Diversity, Rarity, 

and Risk,’’ Conservation Biology 2:149–156 

(1988); N.P. Hitt and P.L. Angermeier, 

‘‘Evidence for Fish Dispersal from Spatial 

Analysis of Stream Network Topology,’’ 

Journal of the North American Benthological 

Society 27:304–320 (2008)). Tributaries also 

serve as an important source of food for biota 

in downstream rivers. Tributaries export 

plankton, vegetation, fish eggs, insects, 

invertebrates like worms or crayfish, smaller 

fish that originate in upstream tributaries and 

other food sources that drift downstream to 

be consumed by other animals. See, e.g., id. 

at 4–29 (citing D.J. Progar and A.R. Modenke, 

‘‘Insect Production from Temporary and 

Perennially Flowing Headwater Streams in 

Western Oregon,’’ Journal of Freshwater 

Ecology 17:391–407 (2002)). For example, 

many fish feed on drifting insects, and 

numerous studies document the downstream 

drift of stream invertebrates that then are 

eaten by fish in larger rivers. See, e.g., id. at 

4–29 to 4–30 (citing S. Nakano and M. 

Murakami, ‘‘Reciprocal Subsidies: Dynamic 

Interdependence between Terrestrial and 

Aquatic Food Webs,’’ Proceedings of the 

National Academy of Sciences USA 98:166– 

170 (2001); M.S. Wipfli and D.P. Gregovich, 

‘‘Export of Invertebrates and Detritus from 

Fishless Headwater Streams in Southeastern 

Alaska: Implications for Downstream 

Salmonid Production,’’ Freshwater Biology 

47:957–969 (2002)). 

Biological connectivity also allows gene 

flow, or genetic connectivity, among tributary 

and river populations. Gene flow is needed 

to maintain genetic diversity in a species, a 

basic requirement for that species to be able 

to adapt to environmental change. 

Populations connected by gene flow have a 

larger breeding population size, making them 

less prone to the deleterious effects of 

inbreeding and local extinction. Id. at 4–33 

(citing R. Lande and S. Shannon, ‘‘The role 

of genetic variation in adaptation and 

population persistence in a changing 

environment,’’ Evolution 50:434–437 (1996)). 

Genetic connectivity exists at multiple scales 

and can extend beyond one a single river 

catchment, and for species capable of long 

distance movement (such as salmon), reveals 

complex interactions among spatially distant 

populations of aquatic organisms Id. (citing 

J.M. Hughes, et al., ‘‘Genes in Streams: Using 

DNA to Understand the Movement of 

Freshwater Fauna and Their Riverine 

Habitat,’’ Bioscience 59:573–583 (2009); C.D. 

Anderson, ‘‘Considering spatial and temporal 

scale in landscape-genetic studies of gene 

flow,’’ Molecular Ecology 19:3565–3575 

(2010)). 

D. Headwater Tributaries Significantly Affect 

the Chemical, Physical, or Biological 

Integrity of (a)(1) Through (a)(3) Waters 

As discussed above, the scientific literature 

supports the conclusion that tributaries, 

including headwater streams, have a 

significant nexus to downstream waters 

based on their contribution to the chemical, 

physical, or biological integrity of (a)(1) 

through (a)(3) waters. Headwater tributaries, 

the small streams at the uppermost reaches 

of the tributary network, are the most 

abundant streams in the United States. See, 

e.g., id. at 4–2 (citing T.L. Nadeau and M.C. 

Rains, ‘‘Hydrological connectivity between 

headwater streams and downstream waters: 

How science can inform policy,’’ Journal of 

the American Water Resources Association 

43:118–133 (2007)). Collectively, they help 

shape the chemical, physical, and biological 

integrity of downstream waters, and provide 

many of the same functions as nonheadwater streams. See, e.g., id. at 1–7 to 1– 

8, 4–1. For example, headwater streams 

reduce the amount of sediment delivered to 

downstream waters by trapping sediment 

from water and runoff. See, e.g., M. Dieterich 

and N.H. Anderson, ‘‘Dynamics of Abiotic 

Parameters, Solute Removal and Sediment 

Retention in Summer-Dry Headwater Stream 

of Western Oregon,’’ Hydrobiologia 379: 1–15 

(1998). Headwater streams shape river 

channels by accumulating and gradually or 

episodically releasing sediment and large 

woody debris into river channels. They are 

also responsible for most nutrient cycling 

and removal, and thus transforming and 

changing the amount of nutrients delivered 

to downstream waters. See, e.g., Report at 4– 

18 (citing B.J. Peterson, et al., ‘‘Control of 

Nitrogen Export from Watersheds by 

Headwater Streams,’’ Science 292: 86–90 

(2001)). A close connection exists between 

the water quality of these streams and the 

water quality of traditional navigable waters, 

interstate waters, and the territorial seas. See, 

e.g., State of Ohio Environmental Protection 

Agency, Nonpoint Source Impacts on 

Primary Headwater Streams (Columbus, OH: 

Ohio Environmental Protection Agency, 

2003). Activities such as discharging a 

pollutant into one part of the tributary system 

are well-documented to affect other parts of 

the system, even when the point of discharge 

is far upstream from the navigable water that 

experiences the effect of the discharge. See, 

e.g., F.M. Dunnivant and E. Anders, A Basic 

Introduction To Pollutant Fate and 

Transport: An Integrated Approach With 

Chemistry, Modeling, Risk Assessment, and 

Environmental Legislation (Hoboken, NJ: 

John Wiley & Sons, Inc., 2006). 

Headwater streams provide unique habitat 

and protection for amphibians, fish, and 

other aquatic or semi-aquatic species living 

in and near the stream that may use the 

downstream waters for other portions of their 

life stages. See, e.g., Report at 1–8; J.L. Meyer, 

et al., ‘‘The Contribution of Headwater 

Streams to Biodiversity in River Networks,’’ 

Journal of the American Water Resources 


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Association 43(1): 86–103 (2007). They also 

serve as migratory corridors for fish. 

Tributaries can improve or maintain 

biological integrity and can control water 

temperatures in the downstream waters. See, 

e.g., Report at 4–14 (citing J.L. Ebersole, et. 

al., ‘‘Cold water patches in warm streams: 

Physicochemical characteristics and the 

influence of shading,’’ Journal of the 

American Water Resources Association 

39:355–368 (2003); B. Gardner, and P.J. 

Sullivan, ‘‘Spatial and temporal stream 

temperature prediction: Modeling 

nonstationary temporal covariance 

structures,’’ Water Resources Research 40:1– 

9 (2004); B.R. Johnson, et al., ‘‘Use of 

spatially explicit physicochemical data to 

measure downstream impacts of headwater 

stream disturbance,’’ Water Resources 

Research 46:W09526 (2010)). Headwater 

streams also provide refuge habitat for 

riverine organisms seeking protection from 

temperature extremes, flow extremes, low 

dissolved oxygen, high sediment levels, or 

the presence of predators, parasites, and 

competitors. See, e.g., id. at 4–32 (citing J.C. 

Scrivener, et al., ‘‘Juvenile Chinook salmon 

(Oncorhynchus tshawytscha) utilization of 

Hawks Creek, a small and nonnatal tributary 

of the Upper Fraser River,’’ Canadian Journal 

of Fisheries and Aquatic Sciences 51:1139– 

1146 (1994); R.A. Curry, et al., ‘‘Use of small 

streams by young brook trout spawned in a 

lake,’’ Transactions of the American 

Fisheries Society 126:77–83 (1997); A.M. 

Pires, et al., ‘‘Seasonal changes in fish 

community structure of intermittent streams 

in the middle reaches of the Guadiana basin, 

Portugal,’’ Journal of Fish Biology 54:235–249 

(1999); M.J Bradford, et al., ‘‘Ecology of 

juvenile Chinook salmon in a small nonnatal 

stream of the Yukon River drainage and the 

role of ice conditions on their distribution 

and survival,’’ Canadian Journal of ZoologyRevue Canadienne De Zoologie 79:2043– 

2054 (2001); M.A. Cairns, et al., ‘‘Influence 

of summer stream temperatures on black spot 

infestation of juvenile coho salmon in the 

Oregon Coast Range,’’ Transactions of the 

American Fisheries Society 134:1471–1479 

(2005); Wigington, P. J., et al., ‘‘Coho salmon 

dependence on intermittent streams,’’ 

Frontiers in Ecology and the Environment 

4:513–518 (2006)). Headwater streams serve 

as a source of food materials such as insects, 

larvae, and organic matter to nourish the fish, 

mammals, amphibians, and other organisms 

in downstream streams, rivers, and lakes. 

See, e.g., id. at 4–22, 4–24 (citing S.G., Fisher, 

and G.E. Likens, ‘‘Energy flow in Bear Brook, 

New Hampshire: An integrative approach to 

stream ecosystem metabolism,’’ Ecological 

Monographs 43:421–439 (1973); J.L. Meyer, 

‘‘The microbial loop in flowing waters,’’ 

Microbial Ecology 28:195–199 (1994); J.B. 

Wallace, et al., ‘‘Multiple trophic levels of a 

forest stream linked to terrestrial litter 

inputs,’’ Science 277:102–104 (1997); R.O. 

Hall, and J.L. Meyer, ‘‘The trophic 

significance of bacteria in a detritus-based 

stream food web,’’ Ecology 79:1995–2012 

(1998); R.O. Hall, et al., ‘‘Organic matter flow 

in stream food webs with reduced detrital 

resource base,’’ Ecology 81:3445–3463 (2000); 

T. Gomi, et al., ‘‘Understanding processes 

and downstream linkages of headwater 

systems,’’ Bioscience 52:905–916 (2002); C. 

Augspurger, et al., ‘‘Tracking carbon flow in 

a 2-week-old and 6-week-old stream biofilm 

food web,’’ Limnology and Oceanography 

53:642–650 (2008)). Disruptions in these 

biological processes affect the ecological 

functions of the entire downstream system. 

See, e.g., L.A. Kaplan, et al., ‘‘Patterns of 

Dissolved Organic Carbon in Transport,’’ 

Limnology and Oceanography 25: 1034–1043 

(1980); R.L. Vannote, et. al., ‘‘The River 

Continuum Concept,’’ Canadian Journal of 

Fisheries and Aquatic Sciences 37: 130–37 

(1980). Headwater streams can help to 

maintain base flow in the larger rivers 

downstream, which is particularly important 

in times of drought. See, e.g., Report at 4–4, 

4–66 (citing P.D. Brooks, and M.M. Lemon, 

‘‘Spatial variability in dissolved organic 

matter and inorganic nitrogen concentrations 

in a semiarid stream, San Pedro River, 

Arizona,’’ Journal of Geophysical ResearchBiogeosciences 112:G03S05.D (2007); 

Tetzlaff, and C. Soulsby, ‘‘Sources of 

baseflow in larger catchments—using tracers 

to develop a holistic understanding of runoff 

generation,’’ Journal of Hydrology 359:287– 

302 (2008)). At the same time, the network 

of headwater streams can regulate the flow of 

water into downstream waters, mitigating 

low flow and high flow extremes, reducing 

local and downstream flooding, and 

preventing excess erosion caused by 

flooding. See, e.g., United States, U.S. EPA 

and USDA/ARS Southwest Watershed 

Research Center, EPA/600/R–08/134, ARS/

2330462008: The Ecological and 

Hydrological Significance of Ephemeral and 

Intermittent Streams in the Arid and Semiarid American Southwest (Washington, DC: 

U.S. EPA and USDA/ARS Southwest 

Watershed Research Center, Levick et al., 

2008) (Levick et al. 2008). 

F. Ephemeral and Intermittent Tributaries 

Significantly Affect the Chemical, Physical, 

or Biological Integrity of (a)(1) Through (a)(3) 

Waters 

Tributaries do not need to flow perennially 

to have a significant nexus to downstream 

waters. Approximately 59% of streams across 

the United States (excluding Alaska) flow 

intermittently or ephemerally; ephemeral and 

intermittent streams are particularly 

prevalent in the arid and semi-arid 

Southwest, where they account for over 81% 

of streams. Levick et al. 2008. Despite their 

intermittent or ephemeral flow, these streams 

nonetheless perform the same important 

ecological and hydrological functions 

documented in the scientific literature as 

perennial streams, through their movement 

of water, nutrients, and sediment to 

downstream waters. Id. The importance of 

intermittent and ephemeral streams is 

documented in a 2008 peer-reviewed report 

by EPA’s Office of Research and 

Development and the U.S. Department of 

Agriculture’s Agricultural Research Service, 

which addresses the hydrological and 

ecological significance of ephemeral and 

intermittent streams in the arid and semi-arid 

Southwestern United States and their 

connections to downstream waters; the report 

is a state-of-the-art synthesis of current 

knowledge of the ecology and hydrology in 

these systems. Id. 

Intermittent and ephemeral streams are 

chemically, physically, and biologically 

connected to downstream waters, and these 

connections have effects downstream. See, 

e.g., id. In some areas, stormflows channeled 

into alluvial floodplain aquifers by 

intermittent and ephemeral streams are the 

major source of annual streamflow in rivers. 

Perennial flows are not necessary for 

chemical connections. Periodic flows in 

ephemeral or intermittent tributaries can 

have a strong influence on biogeochemistry 

by connecting the channel and other 

landscape elements. See, e.g., Report at 4–16 

(citing H.M. Valett, et. al., ‘‘Biogeochemical 

and Metabolic Responses to the Flood Pulse 

in a Semiarid Floodplain,’’ Ecology 86(1): 

220–234 (2005)). This episodic connection 

can be very important for transmitting a 

substantial amount of material into 

downstream rivers. See, e.g., id. (citing 

Nadeau and Rains (2007)). Ephemeral desert 

streams have been shown to export 

particularly high sediment loadings. See, e.g., 

id. at 4–10 (citing M.A. Hassan, 

‘‘Observations of Desert Food Bores,’’ Earth 

Surface Processes and Landforms 15:481–485 

(1990)). Ephemeral streams can also 

temporarily and effectively store large 

amounts of sediment that would otherwise 

wash downstream, contributing to the 

maintenance of downstream water quality 

and productive fish habitat. See, e.g., S.H. 

Duncan, et al., ‘‘Transport of Road-Surface 

Sediment through Ephemeral Stream 

Channels,’’ Water Resources Bulletin 23(1): 

113–119 (1987). This temporary storage of 

sediment thus helps maintain the chemical 

and biologic integrity of downstream waters. 

The Report provides case studies of prairie 

streams and Southwest intermittent and 

ephemeral streams, two stream types whose 

jurisdictional status has been called into 

question in the past. These case studies 

highlight the importance of these streams to 

downstream waters, despite their small size 

and ephemeral or intermittent flow regime. 

Prairie streams are frequently subjected to the 

extremes of drying and flooding, and 

intermittent or flashy hydrology is prevalent 

in river networks throughout most of the 

Great Plains. Report at 4–40 (citing W.J. 

Matthews, ‘‘North American Prairie Streams 

as Systems for Ecological Study,’’ Journal of 

the North American Benthological Society 

7:387–409 (1988); A.V. Zale et al., ‘‘The 

Physicochemistry, Flora, and Fauna of 

Intermittent Prairie Streams: A Review of the 

Literature,’’ United States Fish and Wildlife 

Service Biological Report 89:1–44 (1989); 

N.L. Poff, ‘‘A Hydrogeography of Unregulated 

Streams in the United States and an 

Examination of Scale Dependence in Some 

Hydrological Descriptors,’’ Freshwater 

Biology 36:71–91 (1996); W.K. Dodds, et al., 

‘‘Life on the Edge: The Ecology of Great 

Plains Prairie Streams,’’ Bioscience 54:205– 

216 (2004)). Prairie streams typically 

represent a collection of spring-fed, perennial 

pools and reaches, embedded within larger, 

intermittently flowing segments. Id. at 4–55 

(citing T.R. Labbe, and K.D. Fausch, 

‘‘Dynamics of Intermittent Stream Habitat 

Regulate Persistence of a Threatened Fish at 

Multiple Scales,’’ Ecological Applications 

10:1774–1791 (2000)). These streams have 


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significant chemical, physical, and biological 

connections to downstream waters, despite 

extensive alteration of historical prairie 

regions by agriculture, water impoundment, 

water withdrawals, and other human 

activities, and the challenges these 

alterations create for assessing connectivity. 

Id. (citing W.J. Matthews, and H.W. 

Robinson, ‘‘Influence of Drainage 

Connectivity, Drainage Area and Regional 

Species Richness on Fishes of the Interior 

Highlands in Arkansas,’’ American Midland 

Naturalist 139:1–19 (1998); W.K. Dodds, et 

al., ‘‘Life on the Edge: The Ecology of Great 

Plains Prairie Streams,’’ Bioscience 54:205– 

216 (2004)). The most notable connections 

are via flood propagation, contaminated 

sediment transport, nutrient retention, and 

the extensive transport and movement of fish 

species (including eggs and larvae) 

throughout these networks. Id. at 4–55 (citing 

H.F. Matthai, Floods of June 1965 in South 

Platte River Basin, Colorado, Water Supply 

Paper 1850–B (Washington, DC: U.S. 

Geological Survey, 1969); A.J. Horowitz, et 

al., ‘‘The Effect of Mining on the Sedimenttrace Element Geochemistry of Cores from 

the Cheyenne River Arm of Lake Oahe, South 

Dakota, USA,’’ Chemical Geology 67:17–33 

(1988); DC Marron, ‘‘The Transport of Mine 

Tailings as Suspended Sediment in the Belle 

Fourche River, West-central South Dakota, 

USA,’’ International Association of 

Hydrologic Sciences 184:19–26 (1989); W.K. 

Dodds, et al., ‘‘Nitrogen Transport from 

Tallgrass Prairie Watersheds,’’ Journal of 

Environmental Quality 25:973–981 (1996); 

K.D. Fausch, and K.R. Bestgen, ‘‘Ecology of 

Fishes Indigenous to the Central and 

Southwestern Great Plains,’’ in F.L. Knopf 

and F.B. Samson, ed., Ecology and 

Conservation of Great Plains Vertebrates, 

(New York, NY: Springer-Verlag, 1997), pp. 

131–166; S.P. Platania, and C.S. Altenbach, 

‘‘Reproductive Strategies and Egg Types of 

Seven Rio Grande Basin Cyprinids,’’ Copeia 

1998:559–569 (1998); K.M. Fritz, and W.K. 

Dodds, ‘‘Resistance and Resilience of 

Macroinvertebrate Assemblages to Drying 

and Flood in a Tallgrass Prairie Stream 

System,’’ Hydrobiologia 527:99–112 (2004); 

K.M. Fritz, and W.K. Dodds, ‘‘Harshness: 

Characterization of Intermittent Stream 

Habitat over Space and Time,’’ Marine and 

Freshwater Research 56:13–23 (2005); N.R. 

Franssen, et al., ‘‘Effects of Floods on Fish 

Assemblages in an Intermittent Prairie 

Stream,’’ Freshwater Biology 51:2072–2086 

(2006); R.B. Alexander, et al., ‘‘Differences in 

Phosphorus and Nitrogen Delivery to the 

Gulf of Mexico from the Mississippi River 

Basin,’’ Environmental Science & Technology 

42:822–830 (2008); J.S. Perkins, and K.B. 

Gido, ‘‘Stream Fragmentation Thresholds for 

a Reproductive Guild of Great Plains Fishes,’’ 

Fisheries 36:371–383 (2011)). 

Southwestern intermittent and ephemeral 

streams exert strong influences on the 

structure and function of downstream waters, 

and the case study (included in the Report) 

echoes many of the findings of the functions 

of intermittent and ephemeral tributaries 

generally, which are described above. The 

case study focuses on the heavily studied San 

Pedro River, located in southeast Arizona, in 

particular, as a representative example of the 

hydrological behavior and the connectivity of 

rivers in the Southwest, but also examines 

evidence relevant to other Southwestern 

streams. The chemical, physical, and 

biological connections of Southwestern 

intermittent and ephemeral streams 

highlighted in the case study are summarized 

below. Flows from ephemeral streams are 

one of the major drivers of the dynamic 

hydrology of Southwest rivers (particularly of 

floods during monsoon seasons. Id. at 4–60, 

4–67 (citing DC Goodrich, et al., ‘‘Linearity 

of Basin Response as a Function of Scale in 

a Semiarid Watershed,’’ Water Resources 

Research 33:2951–2965 (1997); F. Yuan, and 

S. Miyamoto, ‘‘Characteristics of Oxygen-18 

and Deuterium Composition in Waters from 

the Pecos River in American Southwest,’’ 

Chemical Geology 255:220–230 (2008)). 

Downstream river fishes and invertebrates 

are adapted to the variable flow regimes that 

are influenced strongly by ephemeral 

tributary systems, which provide isolated 

pools as refuges for fish during dry periods. 

Id. at 4–68 to 4–69 (citing K.R. John, 

‘‘Survival of Fish in Intermittent Streams of 

the Chirichua Mountains, Arizona’’ Ecology 

45:112–119 (1964); T.R. Labbe, and K.D. 

Fausch, ‘‘Dynamics of Intermittent Stream 

Habitat Regulate Persistence of a Threatened 

Fish at Multiple Scales,’’ Ecological 

Applications 10:1774–1791 (2000); J.N. 

Rinne, and D. Miller, ‘‘Hydrology, 

Geomorphology and Management: 

Implications for Sustainability of Native 

Southwestern Fishes,’’ Reviews in Fisheries 

Science 14:91–110 (2006); D.A. Lytle, et al., 

‘‘Evolution of Aquatic Insect Behaviors 

across a Gradient of Disturbance 

Predictability,’’ Proceedings of the Royal 

Society—Series B 275:453–462 (2008)). 

Ephemeral tributaries in the Southwest also 

supply water to mainstem river alluvial 

aquifers, which aids in the sustaining river 

baseflows downstream. Id. at 4–64 (citing DC 

Goodrich, et al., ‘‘Linearity of Basin Response 

as a Function of Scale in a Semiarid 

Watershed,’’ Water Resources Research 

33:2951–2965 (1997); J.B. Callegary, et al., 

‘‘Rapid Estimation of Recharge Potential in 

Ephemeral-Stream Channels using 

Electromagnetic Methods, and Measurements 

of Channel and Vegetation Characteristics,’’ 

Journal of Hydrology 344:17–31 (2007)). 

Ephemeral tributaries export sediment 

downstream during major hydrologic events; 

the sediment, in turn, contributes to 

materials that comprise alluvial aquifers and 

shape the fluvial geomorphology (the science 

of how rivers and streams form given the 

landscape setting) of downstream waters. Id. 

at 4–65 (citing G.C. Nanson, and J.C. Croke, 

‘‘A Genetic Classification of Floodplains,’’ 

Geomorphology 4:459–486 (1992)). The 

nutrient and biogeochemical integrity of 

downstream Southwestern rivers, such as the 

San Pedro River, is heavily influenced by 

nutrient export from ephemeral tributaries 

after storm flow events. Id. at 4–18, 4–66 

(citing P.D. Brooks, and M.M. Lemon, 

‘‘Spatial Variability in Dissolved Organic 

Matter and Inorganic Nitrogen 

Concentrations in a Semiarid Stream, San 

Pedro River, Arizona,’’ Journal of 

Geophysical Research-Biogeosciences 

112:G03S05 (2007)). Extensive downstream 

river riparian communities are supported by 

water, sediment and nutrients exported to the 

river from ephemeral tributaries; these 

riparian communities have a profound 

influence on the river attributes through 

shading, allochthonous (originating from 

outside of the channel) inputs of organic 

matter, detritus, wood, and invertebrates to 

the river. Id. at 4–65 to 4–66 (citing S.V. 

Gregory, et al., ‘‘An Ecosystem Perspective of 

Riparian Zones: Focus on Links between 

Land and Water,’’ Bioscience 41:540–551 

(1991); R.J. Naiman, et al., Riparia: Ecology, 

Conservation, and Management of 

Streamside Communities (Burlington, MA: 

Elsevier, Inc., 2005); J.C. Stromberg, et al., 

‘‘Effects of Stream Flow Intermittency on 

Riparian Vegetation of a Semiarid Region 

River (San Pedro River, Arizona),’’ River 

Research and Applications 21:925–938 

(2005), M. Baillie, et al., ‘‘Quantifying Water 

Sources to a Semiarid Riparian Ecosystem, 

San Pedro River, Arizona,’’ Journal of 

Geophysical Research 112:G03S02 (2007); 

National Research Council, Riparian Areas: 

Functions and Strategies for Management 

(Washington, DC: National Academy Press, 

2002)). 

E. Tributary Lakes, Ponds, and Wetlands 

Significantly Affect the Chemical, Physical, 

or Biological Integrity of (a)(1) Through (a)(3) 

Waters 

As discussed elsewhere in this preamble, 

riparian and floodplain wetlands have a 

significant nexus to downstream waters, and 

wetlands that are tributaries are a subset of 

such wetlands. The fact that a wetland 

tributary is in-stream often enhances its 

ability to filter pollutants and contaminants 

that would otherwise make it downstream; 

in-stream wetlands also attenuate 

floodwaters. Lakes and ponds serve many 

important functions that affect the chemical, 

physical, and biological conditions 

downstream. Lake tributaries can act as 

sinks, storing floodwaters, sediment, and 

nutrients, as these materials have the 

opportunity to settle out, at least temporarily, 

as water moves through the lake to 

downstream waters. See, e.g., R.W. Phillips, 

et al., ‘‘Connectivity and Runoff Dynamics in 

Heterogeneous Basins,’’ Hydrological 

Processes 25(19): 3061–3075 (2011). The 

attenuation of floodwaters can also maintain 

stream flows downstream. Id. Lakes, as with 

other tributaries, can also act as sources, 

contributing flow, nutrient, sediment, and 

other materials downstream. Total Maximum 

Daily Loads (TMDLs) for nutrients have been 

established for many in-stream lakes across 

the country in recognition of the ability of 

lakes to transport nutrients downstream, 

contributing to downstream impairments. 

See, e.g. Maine Department of Environmental 

Protection, Phosphorus Control Action Plan 

and Total Maximum Daily (Annual 

Phosphorous) Load Report, Daigle Pond, New 

Canada, Aroostook County, Maine, Daigle 

Pond PCAP—TMDL Report, Maine DEPLW— 

0789 (Maine DEP, 2006); U.S. Environmental 

Protection Agency, ‘‘Section 6 Echo Park 

Lake TMDLs,’’ Los Angeles Area Lakes 

TMDLs, January 2011 Revised Draft (2011). 

Lakes can also serve as habitat for species 

that then move downstream. For instance, 

brook trout that are stocked in headwater 


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lakes in Idaho and Montana are capable of 

invading most downstream habitat, including 

through very steep channel slopes and 

waterfalls. S.B. Adams, et al., ‘‘Geography of 

Invasion in Mountain Streams: Consequences 

of Headwater Lake Fish Introductions,’’ 

Ecosystems 4(4): 296–307. These non-native 

species can then affect the biological integrity 

of downstream waters by impacting 

populations of native fish species, such as 

cutthroat trout, downstream. See, e.g., J.B. 

Dunham, et al., ‘‘Alien Invasions in Aquatic 

Ecosystems: Toward an Understanding of 

Brook Trout Invasions and Potential Impacts 

on Inland Cutthroat Trout in Western North 

America,’’ Reviews in Fish Biology and 

Fisheries 12(4): 373–391 (2002). For example, 

non-native trout were introduced in 

headwater tributary lakes to the Little Kern 

River in the southern Sierra Nevada and 

dispersed downstream, causing the nearextinction of the native Little Kern golden 

trout. R.A. Knapp, and K.R. Matthews, 

‘‘Effects on Nonnative Fishes on Wilderness 

Lake Ecosystems in the Sierra Nevada and 

Recommendations for Reducing Impacts,’’ in 

D. N. Cole, et al., ed., Wilderness Science in 

a Time of Change Conference, Volume 5: 

Wilderness Ecosystems, Threats, and 

Management, Missoula, Montana, May 23– 

27, 1999, Proceedings RMRS–P–15–VOL–5 

(Ogden, UT: U.S. Department of Agriculture, 

Forest Service, Rocky Mountain Research 

Station, 2000), 312–317. These studies 

demonstrate the ability of organisms to travel 

from tributary lakes to downstream waters, 

which is not limited to just non-native 

species; many other species can also move 

downstream and back again. 

One type of wetlands located in-stream are 

unidirectional wetlands that are connected to 

the river network through a channel (e.g., 

wetlands that serve as stream origins; a 

definition of ‘‘unidirectional wetlands’’ can 

be found in part I section 4.B above). These 

tributary wetlands are generally exemplary of 

tributary wetlands as a whole, and because 

the Report focuses in part on these wetlands, 

they are discussed here in further detail. 

These are wetlands from which a stream 

channel originates. Report at 5–1 to 5–2. 

They are part of the stream network itself, 

and along with first- and second-order 

streams, form the headwaters of the river 

network. Such wetlands have a direct 

hydrologic connection to the tributary 

network via unidirectional flow from 

wetland to the headwater stream. Channel 

origin wetlands generally have important 

chemical, physical, and biological effects on 

(a)(1) through (a)(3) waters, including 

hydrologic, water quality, and habitat 

functions, regardless if the outflow from the 

wetland to the stream is perennial, 

intermittent, or ephemeral. Id. Like other 

wetlands, wetlands that serve as stream 

origins can transport channel-forming 

sediment and woody debris, transport stored 

organic matter, remove and transform 

pollutants and excess nutrients such as 

nitrogen and phosphorus, attenuate and store 

floodwaters, contribute to stream baseflow 

through groundwater recharge, and provide 

habitat for breeding fish, amphibians, 

reptiles, birds, and other aquatic and semiaquatic species that move from the wetlands 

to the river network. Id. at 5–41. 

Wetlands that serve as stream origins 

connect via perennial, intermittent, or 

ephemeral drainages to river networks. Id. at 

5–22 to 5–23 (citing M.C. Rains, et al., ‘‘The 

Role of Perched Aquifers in Hydrological 

Connectivity and Biogeochemical Processes 

in Vernal Pool Landscapes, Central Valley, 

California,’’ Hydrological Processes 20:1157– 

1175 (2006); M.C. Rains, et al., ‘‘Geological 

Control of Physical and Chemical Hydrology 

in California Vernal Pools,’’ Wetlands 

28:347–362 (2008); T.R. Morley, et al., ‘‘The 

Role of Headwater Wetlands in Altering 

Streamflow and Chemistry in a Maine, USA 

Catchment,’’ Journal of the American Water 

Resources Association 47:337–349 (2011)). 

Regardless of the permanence of flow, such 

wetlands have an impact on downstream 

water. Id. at 5–1 to 5–2. Wetland seeps, for 

example, can form where groundwater 

discharges from breaks in slope. Id. at 5–21 

(citing B.R. Hall, et al., ‘‘Environmental 

Influences on Plant Species Composition in 

Ground-water Seeps in the Catskill 

Mountains of New York,’’ Wetlands 21:125– 

134 (2001); M.A. O’Driscoll, and D.R. 

DeWalle, ‘‘Seeps Regulate Stream Nitrate 

Concentration in a Forested Appalachian 

Catchment,’’ Journal of Environmental 

Quality 39:420–431 (2010)). They often have 

perennial connections to the stream, 

providing important sources of water 

downstream, particularly during summer 

baseflow. Id. at 5–22 (citing T.R. Morley, et 

al., ‘‘The Role of Headwater Wetlands in 

Altering Streamflow and Chemistry in a 

Maine, USA Catchment,’’ Journal of the 

American Water Resources Association 

47:337–349 (2011)). In Maine, for example, 

seeps were found to provide 40 to 80% of 

stream water during baseflow periods. Id. In 

other cases, surface connections between 

channel origin wetlands and streams are 

intermittent or ephemeral. For example, 

California vernal pools spill water a great 

number of days during the years via 

channels, providing water downstream. Id. 

(citing M.C. Rains, et al., ‘‘The Role of 

Perched Aquifers in Hydrological 

Connectivity and Biogeochemical Processes 

in Vernal Pool Landscapes, Central Valley, 

California,’’ Hydrological Processes 20:1157– 

1175 (2006); M.C. Rains, et al., ‘‘Geological 

Control of Physical and Chemical Hydrology 

in California Vernal Pools,’’ Wetlands 

28:347–362 (2008)). In addition to surface 

water connections, groundwater flow can 

hydrologically connect wetlands that serve as 

stream origins with the stream network. Id. 

at 5–23. 

The hydrologic connection of the wetland 

to the stream can affect streamflow by 

altering baseflow or storm flow through 

several mechanisms, including surface 

storage and groundwater recharge. Id. at 5– 

25. Studies at the larger scale have shown 

that wetlands, by storing water, reduce peak 

streamflows and, thus, downstream flooding. 

Id. (citing J. Jacques, and D. L. Lorenz, 

Techniques for Estimating the Magnitude 

and Frequency of Floods of Ungauged 

Streams in Minnesota, Report 87–4170 

(Washington, DC: U.S. Geological Survey, 

1988); Vining, K.C., Simulation of 

Streamflow and Wetland Storage, 

Starkweather Coulee Subbasin, North 

Dakota, Water Years 1981–98, WaterResources Investigations Report 02–4113 

(Bismarck, ND: U.S. Geological Survey, 

2002), 33 p.; P. McEachern, et al., 

‘‘Landscape Control of Water Chemistry in 

Northern Boreal Streams of Alberta,’’ Journal 

of Hydrology 323:303–324 (2006); R.A. 

Gleason, et al. Estimating Water Storage 

Capacity of Existing and Potentially 

Restorable Wetland Depressions in a 

Subbasin of the Red River of the North, U.S. 

Geological Survey Open-File Report 2007– 

1159 (Reston, VA: U.S. Geological Survey, 

2007), 36 p.). In some cases, however, where 

wetlands that serve as stream origins are 

already saturated prior to rainfall, they can 

convey stormwater quickly downstream and 

thus actually increase flood peaks. Id. at 227 

(citing Bay, R., ‘‘Runoff from Small Peatland 

Watersheds,’’ Journal of Hydrology 9:90–102 

(1969); A. Bullock, and M. Acreman, ‘‘The 

Role of Wetlands in the Hydrological Cycle,’’ 

Hydrology and Earth System Sciences 7:358– 

389 (2003)). This is because the wetland soil, 

if completely saturated, cannot store any 

additional water, making the wetland enable 

to store floodwater. 

Wetlands that serve as stream origins have 

important chemical connections to 

downstream waters that affect the integrity of 

those waters. These wetlands contain diverse 

microbial populations that perform various 

chemical transformations, acting as source of 

compounds and influencing the water quality 

downstream. Id. at 5–28 (citing K.R. Reddy, 

and R.D. DeLaune, Biogeochemistry of 

Wetlands: Science and Applications, 774 p. 

(2008)). Sulfate-reducing bacteria found in 

some headwater wetlands produce 

methylated mercury, which is then 

transported downstream by surface flows. Id. 

(citing O.K. Linqvist, et al., ‘‘Mercury in the 

Swedish Environment—Recent Research on 

Causes, Consequences, and Remedial 

Measures,’’ Water Air and Soil Pollution 

55:xi-xiii (1991); G. Mierle, and R. Ingram, 

‘‘The Role of Humic Substances in the 

Mobilization of Mercury from Watersheds,’’ 

Water Air and Soil Pollution 56:349–357 

(1991); C.T. Driscoll, et al., ‘‘The Role of 

Dissolved Organic Carbon in the Chemistry 

and Bioavailability of Mercury in Remote 

Adirondack Lakes,’’ Water Air and Soil 

Pollution 80:499–508 (1995); B.A. Branfireun, 

et al., ‘‘In situ Sulphate Stimulation of 

Mercury Methylation in a Boreal Peatland: 

Toward a Link Between Acid Rain and 

Methylmercury Contamination in Remote 

Environments,’’ Global Biogeochemical 

Cycles 13:743–750 (1999)). Wetlands, 

including those that serve as stream origins, 

are the principle sources of dissolved organic 

carbon (DOC) in forests to downstream 

waters. Id. (citing P.J. Mulholland, and E.J. 

Kuenzler, ‘‘Organic Carbon Export from 

Upland and Forested Wetland Watersheds,’’ 

Limnology and Oceanography 24:960–966 

(1979); N.R. Urban, et al., ‘‘Export of 

Dissolved Organic Carbon and Acidity from 

Peatlands,’’ Water Resources Research 

25:1619–1628 (1989); B.W. Eckhardt and T.R. 

Moore, ‘‘Controls on Dissolved Organic 

Carbon Concentrations in Streams of 

Southern Quebec,’’ Canadian Journal of 

Fisheries and Aquatic Sciences 47:1537–1544 

(1990); J.-F. Koprivnjak and T.R. Moore, 


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22234 Federal Register / Vol. 79, No. 76 / Monday, April 21, 2014 / Proposed Rules 

‘‘Sources, Sinks, and Fluxes of Dissolved 

Organic Carbon in Subarctic Fen 

Catchments,’’ Arctic and Alpine Research 

24:204–210 (1992); P. Kortelainen, ‘‘Content 

of Total Organic Carbon in Finnish Lakes and 

Its Relationship to Catchment 

Characteristics,’’ Canadian Journal of 

Fisheries and Aquatic Sciences 50:1477–1483 

(1993); T.A. Clair, et al., ‘‘Exports of Carbon 

and Nitrogen from River Basins in Canada’s 

Atlantic Provinces,’’ Global Biogeochemical 

Cycles 8:441–450 (1994); D. Hope, et al., ‘‘A 

Review of the Export of Carbon in River 

Water: Fluxes and Processes,’’ Environmental 

Pollution 84:301–324 (1994); P.J. Dillon and 

L.A. Molot, ‘‘Effects of Landscape Form on 

Export of Dissolved Organic Carbon, Iron, 

and Phosphorus from Forested Stream 

Catchments,’’ Water Resources Research 

33:2591–2600 (1997); S.E. Gergel, et al., 

‘‘Dissolved Organic Carbon as an Indicator of 

the Scale of Watershed Influence on Lakes 

and Rivers,’’ Ecological Applications 9:1377– 

1390 (1999)). Export of DOC to downstream 

waters supports primary productivity, effects 

pH and buffering capacity, and regulates 

exposure to UV–B radiation. Id. at 5–29 

(citing K.N. Eshelman and H.F. Hemond, 

‘‘The Role of Organic Acids in the Acid-base 

Status of Surface Waters at Bickford 

Watershed, Massachusetts,’’ Water Resources 

Research 21:1503–1510 (1985); L.O. Hedin, et 

al., ‘‘Patterns of Nutrient Loss from 

Unpolluted Old-growth Temperate Forests: 

Evaluation of Biogeochemical Theory,’’ 

Ecology 76:493–509 (1995); D.W. Schindler 

and P.J. Curtis, ‘‘The Role of DOC in 

Protecting Freshwaters Subjected to Climate 

Warming and Acidification from UV 

Exposure,’’ Biogeochemistry 36:1–8 (1997); 

J.C. Nuff and G.P. Asner, ‘‘Dissolved Organic 

Carbon in Terrestrial Ecosystems: Synthesis 

and a Model,’’ Ecosystems 4:29–48 (2001)). 

Wetlands also act as sinks and transformers 

for pollutants, including excess nutrients, 

through such processes as denitrification, 

ammonia volatilization, microbial and plant 

biomass assimilation, sedimentation, 

sorption and precipitation, biological uptake, 

and long-term storage of plant detritus. Id. 

(citing K.C. Ewel and H.T. Odum, Cypress 

Swamps (Gainesville, FL: University Presses 

of Florida, 1984); S.J. Nixon and V.J. Lee, 

Wetlands and Water Quality: A Regional 

Review of Recent Research in the United 

States on the Role of Freshwater and 

Saltwater Wetlands as Sources, Sinks, and 

Transformers of Nitrogen, Phosphorus, and 

Various Heavy Metals, Technical Report Y– 

86–2 (Vicksburg, MS: U.S. Army Corps of 

Engineers, Waterways Experiment Station, 

1986); C. Johnston, ‘‘Sediment and Nutrient 

Retention by Freshwater Wetlands: Effects on 

Surface Water Quality,’’ Critical Reviews in 

Environmental Control 21:491–565 (1991); 

K.R. Reddy, et al., ‘‘Phosphorus Retention in 

Streams and Wetlands: A Review,’’ Critical 

Reviews in Environmental Science and 

Technology 29:83–146 (1999); W.J. Mitsch 

and J.G. Gosselink, Wetlands, 4th edition 

(Hoboken, NJ: John Wiley & Sons Inc., 2007); 

K.R. Reddy, and R.D. DeLaune, 

Biogeochemistry of Wetlands: Science and 

Applications (Boca Raton, FL: CRC Press, 

2008); R.H. Kadlec and S.D. Wallace, 

Treatment Wetlands, 2nd edition (Boca 

Raton, FL: CRC Press, 2009)). Specifically, 

wetlands reduce phosphorus, nitrate, and 

ammonium by large percentages. Id. at 5–30 

(citing F.E. Dierberg and P.L. Brezonik, 

‘‘Nitrogen and Phosphorus Mass Balances in 

a Cypress Dome Receiving Wastewater,’’ in 

K.C. Ewel and H.T. Odum, ed., Cypress 

Swamps (Gainesville, FL: University Presses 

of Florida, 1984), pp. 112–118; E.J. Dunne, et 

al., ‘‘Phosphorus Release and Retention by 

Soils of Natural Isolated Wetlands,’’ 

International Journal of Environment and 

Pollution 28:496–516 (2006); T.E. Jordan, et 

al., ‘‘Comparing Functional Assessments of 

Wetlands to Measurements of Soil 

Characteristics and Nitrogen Processing,’’ 

Wetlands 27:479–497 (2007)). These 

processes are important for protecting 

downstream waters from pollutants from 

agricultural runoff. Wetland microbial 

processes reduce other pollutants, such as 

pesticides, hydrocarbons, heavy metals, and 

chlorinated solvents. Id. (citing R.R. Brooks, 

et al., ‘‘Cobalt and Nickel Uptake by the 

Nyssaceae,’’ Taxon 26:197–201 (1977); C.M. 

Kao, et al., ‘‘Non-point Source Pesticide 

Removal by a Mountainous Wetland,’’ Water 

Science and Technology 46:199–206 (2002); 

P.I. Boon, ‘‘Biogeochemistry and Bacterial 

Ecology of Hydrologically Dynamic 

Wetlands,’’ in D. P. Batzer and R. R. Sharitz, 

ed., Ecology of Freshwater and Estuarine 

Wetlands (Berkeley, CA: University of 

California Press, 2006), pp. 115–176). 

Tributary wetlands have important 

biological connections downstream that 

impact the integrity of (a)(1) through (a)(3) 

waters. Emergent and aquatic vegetation 

found in wetlands disperse by water, wind, 

and hitchhiking on migratory animals from 

tributary wetlands downstream. Id. at 5–31 

(citing M.B. Soons and G.W. Heil, ‘‘Reduced 

Colonization Capacity in Fragmented 

Populations of Wind-Dispersed Grassland 

Forbs,’’ Journal of Ecology 90:1033–1043 

(2002); M.B. Soons, ‘‘Wind Dispersal in 

Freshwater Wetlands: Knowledge for 

Conservation and Restoration,’’ Applied 

Vegetation Science 9:271–278 (2006); C. 

Nilsson, et al., ‘‘The Role of Hydrochory in 

Structuring Riparian and Wetland 

Vegetation,’’ Biological Reviews 85:837–858 

(2010)). Similarly, fish move between the 

river network and wetlands during times of 

surface water connections, and tributary 

wetlands by definition are connected on the 

surface to downstream waters. Id. at 5–32 

(citing J.W. Snodgrass, et al., ‘‘Factors 

affecting the occurrence and structure of fish 

assemblages in isolated wetlands of the 

upper coastal plain, USA,’’ Canadian Journal 

of Fisheries and Aquatic Sciences 53:443– 

454 (1996); K.D. Zimmer, et al., ‘‘Effects of 

fathead minnow colonization and removal on 

a prairie wetland ecosystem,’’ Ecosystems 

4:346–357 (2001); M.J. Baber, et al., ‘‘Controls 

on fish distribution and abundance in 

temporary wetlands,’’ Canadian Journal of 

Fisheries and Aquatic Sciences 59:1441–1450 

(2002); M.A. Hanson, et al., ‘‘Biotic 

interactions as determinants of ecosystem 

structure in prairie wetlands: An example 

using fish,’’ Wetlands 25:764–775 (2005); 

B.R. Herwig, et al., ‘‘Factors influencing fish 

distributions in shallow lakes in prairie and 

prairie-parkland regions of Minnesota, USA,’’ 

Wetlands 30:609–619 (2010)). Mammals that 

can disperse overland can also contribute to 

connectivity. Id. (citing C.E. Shanks, and G.C. 

Arthur, ‘‘Muskrat movements and population 

dynamics in Missouri farm ponds and 

streams,’’ Journal of Wildlife Management 

16:138–148 (1952); W.R. Clark, ‘‘Ecology of 

muskrats in prairie wetlands,’’ in H.R. 

Murkin, et al., ed., Prairie Wetland Ecology: 

The Contribution of the Marsh Ecology 

Research Program, (Ames, IA: Iowa State 

University Press, 2000), pp. 287–313). Insects 

also hitchhike on birds and mammals from 

tributary wetlands to the stream network, 

which can then serve as a food source for 

downstream waters. Id. (citing J. Figuerola, 

and A.J. Green, ‘‘Dispersal of Aquatic 

Organisms by Waterbirds: A Review of Past 

Research and Priorities for Future Studies,’’ 

Freshwater Biology 47:483–494 (2002); J. 

Figuerola, et al., ‘‘Invertebrate Eggs Can Fly: 

Evidence of Waterfowl-Mediated Gene Flow 

in Aquatic Invertebrates,’’ American 

Naturalist 165:274–280 (2005)). Insects that 

are flight-capable also use both stream and 

tributary wetlands, moving from the stream 

to the wetland to find suitable habitat for 

overwintering, refuge from adverse 

conditions, hunting, foraging, or breeding. Id. 

at 5–33 (citing D.D. Williams, 

‘‘Environmental Constraints in Temporary 

Fresh Waters and Their Consequences for the 

Insect Fauna,’’ Journal of the North American 

Benthological Society 15:634–650 (1996); A.J. 

Bohonak and D.G. Jenkins, ‘‘Ecological and 

Evolutionary Significance of Dispersal by 

Freshwater Invertebrates,’’ Ecology Letters 

6:783–796 (2003)). Amphibians and reptiles, 

including frogs, toads, and newts, also move 

between streams or rivers and tributary 

wetlands to satisfy part of their life history 

requirements, feed on aquatic insects, and 

avoid predators. Id. (citing V.S. Lamoureux 

and D.M. Madison, ‘‘Overwintering Habitats 

of Radio-Implanted Green Frogs, Rana 

clamitans,’’ Journal of Herpetology 33:430– 

435 (1999); K.J. Babbitt, et al., ‘‘Patterns of 

Larval Amphibian Distribution Along a 

Wetland Hydroperiod Gradient,’’ Canadian 

Journal of Zoology-Revue Canadienne De 

Zoologie 81:1539–1552 (2003); S.B. Adams, 

et al., ‘‘Instream Movements by Boreal Toads 

(Bufo boreas boreas),’’ Herpetological Review 

36:27–33 (2005); D.M. Green, ‘‘Bufo 

americanus, American Toad,’’ in M. Lannoo, 

ed., Amphibian Declines: The Conservation 

Status of United States Species (Berkeley, 

CA: University of California Press, 2005), pp. 

692–704; T.W. Hunsinger and M.J. Lannoo, 

‘‘Notophthalmus viridescens, Eastern Newt,’’ 

in M. Lannoo, ed., Amphibian Declines: The 

Conservation Status of United States Species 

(Berkeley, CA: University of California Press, 

2005), pp. 912–914; J.W. Petranka, and C.T. 

Holbrook, ‘‘Wetland Restoration for 

Amphibians: Should Local Sites Be Designed 

to Support Metapopulations or Patchy 

Populations?,’’ Restoration Ecology 14:404– 

411 (2006); A.L. Subalusky, et al., 

‘‘Ontogenetic Niche Shifts in the American 

Alligator Establish Functional Connectivity 

between Aquatic Systems,’’ Biological 

Conservation 142:1507–1514 (2009)). 

Lake, pond, and wetland tributaries, 

including wetlands that serve as stream 

origins, have important chemical, physical, 


emcdonald on DSK67QTVN1PROD with PROPOSALS2
Federal Register / Vol. 79, No. 76 / Monday, April 21, 2014 / Proposed Rules 22235 

and biological connections downstream that 

affect (a)(1) through (a)(3) waters. Their direct 

hydrologic connection to the stream network 

facilitates the significant impact they have 

downstream. This impact on downstream 

waters occurs regardless of whether their 

flow is perennial, intermittent, or ephemeral. 

Thus, lake, pond, and wetland tributaries 

serve the same important functions as stream 

tributaries, which in turn greatly impact 

downstream (a)(1) through (a)(3) waters, 

particularly when their functional 

contributions to the chemical, physical, and 

biological conditions of downstream waters 

are combined at a watershed scale. 

F. Man-Made or Man-Altered Tributaries 

Significantly Affect the Physical, Chemical 

and Biological Integrity of (a)(1) Through 

(a)(3) Waters 

The agencies’ proposed rule clarifies that 

man-made and man-altered tributaries as 

defined in the proposed rule are ‘‘waters of 

the United States’’ because the significant 

nexus between a tributary and a traditional 

navigable water or interstate water is not 

broken where the tributary flows through a 

culvert or other structure. Note that the 

proposal excludes certain ditches from CWA 

jurisdiction by rule in paragraphs (b)(3) and 

(b)(4). The scientific literature indicates that 

structures that convey water do not affect the 

connectivity between streams and 

downstream rivers. Indeed, because such 

structures can reduce water losses from 

evapotranspiration and seepage, such 

structures likely enhance the extent of 

connectivity by more completely conveying 

the water downstream. 

Man-made and man-altered tributaries 

include impoundments, ditches, canals, 

channelized streams, piped, and the like. 

Ditches and canals are wide-spread across 

the United States. Ditches may have been 

streams that were channelized. They are 

purposely constructed to allow the 

hydrologic flow of the tributary to continue 

downstream. Man-made and man-altered 

tributaries, despite human manipulation, 

usually continue to have chemical, physical, 

or biological connections downstream and to 

serve important functions downstream. 

Because these tributaries are hydrologically 

connected to downstream waters, the 

chemical and some biological connections to 

downstream waters that are supported by this 

hydrologic connection are still intact. Oftentimes man-made tributaries create 

connections where they did not previously 

exist, such as canals that connect two rivers 

in different watersheds. 

Tributary ditches and other man-made or 

man-altered waters that meet the definition 

of ‘‘tributary’’ have a significant nexus to 

(a)(1) through (a)(3) waters due to their 

impact, either individually or with other 

tributaries, on the chemical, physical, or 

biological integrity of those downstream 

waters. Tributary ditches and the like, as 

with other tributaries, have chemical, 

physical, and biological connections with 

downstream waters that substantially impact 

those waters. Tributary ditches and canals 

can have perennial, intermittent, or 

ephemeral flow. As described above, 

tributaries of all flow regimes have a 

significant nexus to downstream (a)(1) 

through (a)(3) waters. Due to the often 

straightened and channelized nature of 

ditches, these tributaries quickly move water 

downstream to (a)(1) through (a)(3) waters. 

Ditches and canals, like other tributaries, 

export sediment, nutrients, and other 

materials downstream. Due to their often 

channelized nature, ditches are very effective 

at transporting water and these materials, 

including nitrogen, downstream. See, e.g., 

J.P. Schmidt, et al., ‘‘Nitrogen Export from 

Coastal Plain Field Ditches,’’ Journal of Soil 

and Water Conservation 62(4):235–243; J.S. 

Strock, et al., ‘‘Managing Natural Processes in 

Drainage Ditches for Nonpoint Source 

Nitrogen Control.’’ Journal of Soil and Water 

Conservation 62(4): 188–196 (2007). Ditches 

provide habitat for fish and other aquatic 

organisms. See, e.g., P.C. Smiley, Jr., et al., 

‘‘Contribution of Habitat and Water Quality 

to the Integrity of Fish Communities in 

Agricultural Drainage Ditches,’’ Journal of 

Soil and Water Conservation 63(6):218A– 

219A (2008). Fish and other aquatic 

organisms utilize canals and ditches to move 

to different habitats, sometimes over long 

distances. F.J. Rahel, ‘‘Biogeographic 

Barriers, Connectivity and Homogenization 

of Freshwater Faunas: It’s a Small World after 

All,’’ Freshwater Biology 52(4): 696–710 

(2007). 

These significant connections and 

functions continue even where the tributary 

has a natural or man-made break in its 

channel, bed and banks, or OHWM. The 

presence of a channel, bed and banks, and 

OHWM upstream or downstream of the break 

is an indication that connections still exist. 

The significant nexus between a tributary 

and a downstream water is not broken where 

the tributary flows underground for a portion 

of its length, such as in karst topography. The 

hydrologic connection still exists, meaning 

that the chemical and biological connections 

that are mediated by the hydrologic 

connection also still exist. Similarly, flow 

through boulder fields does not sever the 

hydrologic connection. When a tributary 

flows through a wetland enroute to another 

or the same tributary, the significant nexus 

still exists even though the bed and banks or 

ordinary high watermark is broken for the 

length of the wetland. As discussed in Part 

II, section 1.G. of this appendix, in-stream 

wetlands provide numerous benefits 

downstream, and the presence of the wetland 

in stream can provide additional water 

quality benefits to the receiving waters. Flow 

in flat areas with very low gradients may 

temporarily break the tributary’s bed and 

banks or OHWM, but these systems continue 

to have a significant nexus downstream. 

These are just illustrative examples of break 

in ordinary high watermark; there are several 

other types, all of which do not break the 

significant nexus between a tributary and the 

downstream (a)(1) through (a)(3) water. 

There are more than 80,000 dams in the 

United States, with over 6,000 exceeding 15 

meters in height. Report at 3–48 (citing U.S. 

Army Corps of Engineers, National Inventory 

of Dams (2009)). The purpose of a dam is to 

impound (store) water for any of several 

reasons (e.g. flood control, human water 

supply, irrigation, livestock water supply, 

energy generation, containment of mine 

tailings, recreation or pollution control). See 

http://www.damsafety.org/layout/

subsection.aspx?groupid=14&contentid=47. 

Many dams fulfill a combination of the above 

functions. Because the purpose of a dam is 

to retain water effectively and safely, the 

water retention ability of a dam is of prime 

importance. Water may pass from the 

reservoir to the downstream side of a dam by: 

passing through the main spillway or outlet 

works; passing over an auxiliary spillway; 

overtopping the dam; seepage through the 

abutments; and seepage under the dam. Id. 

All water retention structures are subject to 

seepage through their foundations and 

abutments. Department of the Army, U.S. 

Army Corps of Engineers, Engineering and 

Design—Design, Construction and 

Maintenance of Relief Wells, EM 1110–2– 

1914 (Washington, DC: Department of the 

Army, 1992), p. 1–1. Thus waters behind a 

dam still maintain a hydrologic connection to 

downstream waters. 

Numerous studies have shown that dams 

impede biotic movements, reducing 

biological connectivity between upstream 

and downstream locations. Report at 3–48 

(citing E.A. Greathouse, et al., ‘‘Indirect 

Upstream Effects Of Dams: Consequences Of 

Migratory Consumer Extirpation In Puerto 

Rico,’’ Ecological Applications 16: 339–352 

(2006); C.J. Hall, et al., ‘‘The Historic 

Influence of Dams on Diadromous Fish 

Habitat with a Focus on River Herring and 

Hydrologic Longitudinal Connectivity,’’ 

Landscape Ecology 26: 95–107(2011)). Dams 

alter but typically do not sever the hydrologic 

connection between upstream and 

downstream waters. (See Part II, section 2.C. 

of this appendix). Upstream of large dams 

riparian areas are permanently inundated, 

increasing hydrological connectivity. 

Downstream, peak flows and the potential for 

overbank lateral flow are reduced; however, 

dams may also reduce flow variability 

downstream, resulting in higher minimum 

flows and reduced flow intermittency and 

thereby increasing hydrological (and 

potentially biological) connectivity. Id. 

(citing N.L. Poff, et al., ‘‘Homogenization of 

Regional River Dynamics by Dams and 

Global Biodiversity Implications,’’ 

Proceedings of the National Academy of 

Sciences of the United States of America 104: 

5732–5737 (2007)). Where an impoundment 

does stop flow, it also has significant effects 

on downstream waters. For example, the 

downstream segments have a reduced 

quantity of waters, less sediment, and 

reduced species biological connectivity with 

upstream refugia. 

Because dams reduce the amount of 

sediment delivered downstream, the 

reservoirs behind dams are actually very 

effective at retaining sediment, which can 

have significant effects in downstream 

waters. For instance, the Mississippi River’s 

natural sediment load has been reduced by 

an estimated 50% through dam construction 

in the Mississippi Basin. M.D. Blum, and H. 

H. Roberts, ‘‘Drowning of the Mississippi 

Delta Due to Insufficient Sediment Supply 

and Global Sea-Level Rise,’’ Nature 

Geoscience 2(7): 488–491 (2009). 

Man-made or man-altered tributaries 

continue to have chemical, physical, and 


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biological connections that significantly 

affect the integrity of (a)(1) through (a)(3) 

waters. Though the man-made or man-altered 

nature of such tributaries can change the 

nature of the connections, it does not 

eliminate them. Thus, man-made and manaltered tributaries continue to serve the same 

important functions as ‘‘natural’’ tributaries, 

which in turn greatly impact downstream 

(a)(1) through (a)(3) waters, particularly when 

their functional contributions to the 

chemical, physical, and biological conditions 

of downstream waters are combined at a 

watershed scale. 

ii. Adjacent Waters 

Adjacent waters, including adjacent 

wetlands, alone or in combination with other 

adjacent waters in the watershed, have a 

substantial impact on the chemical, physical, 

or biological integrity of traditional navigable 

waters, interstate waters, and the territorial 

seas. In addition, waters adjacent to 

tributaries serve many important functions 

that directly influence the integrity of 

downstream waters including traditional 

navigable waters, interstate waters, and the 

territorial seas. Adjacent waters store water, 

which can reduce flooding of downstream 

waters, and the loss of adjacent waters has 

been shown, in some circumstances, to 

increase downstream flooding. Adjacent 

waters maintain water quality and quantity, 

trap sediments, store and modify potential 

pollutants, and provide habitat for plants and 

animals, thereby sustaining the biological 

productivity of downstream rivers, lakes and 

estuaries, which may be traditional navigable 

waters, interstate waters, or the territorial 

seas. The scientific literature and Report 

supports these conclusions, as discussed in 

greater detail below. 

1. Adjacent Waters Under This Proposed 

Rule Have a Significant Nexus to (a)(1) 

Through (a)(3) Waters 

The discussion below summarizes the key 

points made in the Report and explains the 

technical basis for supporting a conclusion 

that adjacent waters, as defined in this 

proposed rule, have a significant nexus to 

waters identified in paragraphs (a)(1) through 

(a)(3) of the proposed rule. The geographic 

position of an ‘‘adjacent’’ water relative to the 

stream is indicative of the relationship they 

share, with many of its defining 

characteristics resulting from the movement 

of materials and energy between the two. A 

review and analysis of the scientific literature 

supports the conclusion that individually or 

in combination with similarly situated waters 

in a watershed, adjacent waters have a 

significant effect on the chemical, physical, 

and biological integrity of downstream 

traditionally navigable waters, interstate 

waters, and the territorial seas. 

a. Riparian and Floodplain Waters 

Significantly Affect the Chemical, Physical, 

or Biological Integrity of (a)(1) Through (a)(3) 

Waters 

Waters, including wetlands, often lie 

within landscape settings that have 

bidirectional hydrological exchange with 

(a)(1) through (a)(5) waters (e.g., wetlands 

and open waters in riparian areas and flood 

plains). Such waters play an integral role in 

the chemical, physical, and biological 

integrity of the waters to which they are 

adjacent. Riparian areas and floodplains 

often describe the same geographic region. 

Report at 3–4. Therefore, the discussion of 

the functions of waters, including wetlands, 

in riparian areas will typically apply to 

floodplains unless otherwise noted. Where 

connections arise specifically from the act of 

inundation of adjacent land during times of 

higher-than-normal water, the term 

‘‘floodplain’’ is solely used to describe the 

area. 

Riparian areas are transition zones between 

terrestrial and aquatic ecosystems that are 

distinguished by gradients in biophysical 

conditions, ecological processes, and biota. 

Id., Report at 31. Waters including wetlands 

in riparian areas significantly influence 

exchanges of energy and matter with aquatic 

ecosystems. See, e.g., id. (citing National 

Research Council, Riparian Areas: Functions 

and Strategies for Management (Washington, 

DC: The National Academies Press, 2002). 

Floodplains are low gradient areas 

bordering stream or river channels, lakes, and 

impoundments that were formed by sediment 

deposition from those waters under present 

climatic conditions. These natural 

geomorphic features are inundated during 

moderate to high water events. Id. (citing L.B. 

Leopold, A View of the River (Cambridge, 

MA: Harvard University Press, 1994); W.R. 

Osterkamp, Annotated Definitions of 

Selected Geomorphic Terms and Related 

Terms of Hydrology, Sedimentology, Soil 

Science and Ecology, USGS Open File Report 

2008–1217 (Reston, VA: U.S. Department of 

the Interior, U.S. Geological Survey, 2008)). 

By ‘‘present climactic conditions,’’ the 

agencies mean that currently or recently 

active floodplains will be used to help 

determine whether wetlands or waters are 

adjacent to ‘‘waters of the United States.’’ 

The proposed definition is limited to the 

present climactic conditions in order to best 

represent the floodplain that has an active 

and significant relationship with the stream 

or river channel. Historic floodplains that 

played a role in the river or lake dynamics 

in the past only will not be used to determine 

whether a water is adjacent. Floodplains 

formed under different climactic conditions 

that no longer connect to the stream channel 

that formed them are terraces. Id. It should 

be noted that ‘‘floodplain’’ as defined in 

today’s proposed rule does not necessarily 

equate to the 100-year floodplain as defined 

by the Federal Emergency Management 

Agency (FEMA). However, the FEMA defined 

floodplain may often coincide with the 

current definition proposed in this rule. 

Flood insurance rate maps are based on the 

probability of a flood event occurring (e.g., 

100-year floods have a 1% probability of 

occurring in a given year or 500 year-floods 

have a 0.2% probability of occurring in a 

particular year). Flood insurance rate maps 

are not based on an ecological definition of 

the term ‘‘floodplain,’’ and therefore may not 

be appropriate for identifying adjacent 

wetlands and waters for the purposes of 

CWA jurisdiction. Flood insurance rate maps 

are developed by applying models and other 

information to identify areas that would be 

inundated by a flood event of a particular 

probability of recurring. 

Riparian waters take many different forms. 

Some may be wetlands, which are defined in 

paragraph (c)(6) of the proposed rule. Others 

may be ponds, oxbow lakes, or other types 

of open waters. Oxbow lakes, commonly 

found in floodplains, are formed when river 

meanders are cutoff from the rest of the river. 

Id. at 5–42. 

b. Riparian and Floodplain Waters 

Significantly Affect the Physical Integrity of 

(a)(1) Through (a)(3) Waters 

Scientific research shows waters and 

wetlands in riparian areas and floodplains to 

be important in protecting the physical 

integrity of aquatic resources. Because 

riparian and floodplain waters exhibit 

bidirectional exchange of water with the 

waters to which they are adjacent, they play 

an important role in determining the volume 

and duration of stream flow. Riparian and 

floodplain waters also have an essential role 

in regulating and stabilizing sediment 

transport to downstream waters. These 

characteristics are fundamental to the 

physical integrity of streams as well as 

downstream traditional navigable waters, 

interstate waters, and the territorial seas. 

Riparian and floodplain wetlands are 

important for the reduction or delay of 

floods. Id.at 3–22 (citing A. Bullock and M. 

Acreman, ‘‘The Role of Wetlands in the 

Hydrological Cycle,’’ Hydrology and Earth 

System Sciences 7:358–389 (2003)). Waters in 

riparian areas control flooding during times 

of high precipitation or snowmelt by 

capturing water from overbank flow and 

storing excess stream water. Id. at 5–6. One 

study found that peak flows in the Cache 

River in Arkansas decreased by 10–20% 

mainly because of floodplain water storage. 

Id. (citing R. Walton, et al., ‘‘Hydrology of the 

Black Swamp Wetlands on the Cache River, 

Arkansas,’’ Wetlands 16:279–287 (1996). 

Research has shown that floodplain wetlands 

in Ohio store about 40% of the flow of small 

streams. Id. at 5–6 to 5–7 (citing D.E. Gamble, 

et al., An Ecological and Functional 

Assessment of Urban Wetlands in Central 

Ohio. Columbus, Ohio, EPA Technical Report 

WET/2007–3B, (Columbus, OH: Ohio 

Environmental Protection Agency, Wetland 

Ecology Group, Division of Surface Water, 

2007)). These and similar findings point to 

the close hydrological influence that waters 

in riparian and floodplain areas have on 

streams. 

Some adjacent waters are bordering or 

contiguous with (a)(1) through (a)(5) waters. 

Because of their close physical proximity to 

nearby water bodies, they readily exchange 

their waters through the saturated soils 

surrounding the stream or through surface 

exchange. This commingling of waters allows 

bordering or contiguous waters to both 

provide chemically transformed waters to 

streams and to absorb excess stream flow. 

Flow between neighboring waters and 

streams is more longitudinal (downslope) at 

headwaters and more lateral further 

downstream. Id. at 5–38, Table 5–3. These 

connections in part determine stream flow 

volume and duration. Waters, including 

wetlands, in riparian areas connect to 

neighboring water bodies through various 

surface and subsurface connections. See, e.g., 

id. at 3–4 (citing National Research Council, 


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Riparian Areas: Functions and Strategies for 

Management (Washington, DC: National 

Academy Press, 2002)). Floodplains, 

similarly, are closely associated with the 

groundwater found beneath and beside river 

channels (which are considered shallow 

aquifers) and waters in floodplains readily 

exchange water with such aquifers. Id. at 3– 

14 (citing J.A. Stanford and J. V. Ward, ‘‘An 

Ecosystem Perspective of Alluvial Rivers: 

Connectivity and the Hyporheic Corridor,’’ 

Journal of the North American Benthological 

Society 12:48–60 (1993); C. Amoros and G. 

Bornette, ‘‘Connectivity and Biocompexity in 

Waterbodies of Riverine Floodplains,’’ 

Freshwater Biology 47:761–776 (2002); G.C. 

Poole, et al., ‘‘Multiscale Geomorphic Drivers 

of Groundwater Flow Paths: Subsurface 

Hydrologic Dynamics and Hyporheic 

Diversity,’’ Journal of the North American 

Benthological Society 25:288–303 (2006)). 

Riparian and floodplain wetlands are 

frequently contiguous with streams and other 

water bodies and significantly influence the 

hydrology of such water bodies. Id. at 5–6 

(citing R.J. Naiman, et al., Riparia: Ecology, 

Conservation, and Management of 

Streamside Communities (Burlington, MA: 

Elsevier Academic Press, 2005); P. Vidon, et 

al., ‘‘Hot Spots and Hot Moments in Riparian 

Zones: Potential for Improved Water Quality 

Management,’’ Journal of the American 

Water Resources Association 46:278–298 

(2010)). Floodplain wetlands are important 

for the reduction or delay of floods. Id. (citing 

A. Bullock and M. Acreman, ‘‘The Role of 

Wetlands in the Hydrological Cycle,’’ 

Hydrology and Earth System Sciences 7:358– 

389 (2003)). Oxbow lakes also retain flood 

waters. Id. at 5–44. Adjacent ponds generally 

function similarly to oxbow lakes. 

Waters in riparian areas filter sediment 

washed down from uplands and collect 

sediment from overbank flow as the river or 

stream floods. Id. at 5–7. For example, 

riparian areas were observed to collect 80– 

90% of the sediment from farmlands in a 

study in North Carolina. Id. (citing A. 

Cooper, et al., ‘‘Riparian Areas as Filters for 

Agricultural Sediment,’’ Soil Science Society 

of America Proceedings 51:416–420 (1987); 

R.B. Daniels and J.G. Gilliam, ‘‘Sediment and 

Chemical Load Reduction by Grass and 

Riparian Filters,’’ Soil Science Society of 

America Journal 60:246–251 (1996); R.J. 

Naiman and H. Decamps, ‘‘The Ecology of 

Interfaces: Riparian Zones,’’ Annual Review 

of Ecology and Systematics 28:621–658 

(1997)). Maintaining the equilibrium between 

sediment deposition and sediment transport 

is important to maintain the physical shape 

and structure of stream channels. Significant 

changes to upstream channels can affect the 

chemical, physical, and biological condition 

of downstream (a)(1) through (a)(3) waters. 

The physical effects of excess sediment can 

impair chemical and ecological integrity in a 

variety of ways. Id. at 5–9 (citing P.J. Wood 

and P.D. Armitage, ‘‘Biological Effects of Fine 

Sediment in the Lotic Environment,’’ 

Environmental Management 21:203–217 

(1997)). Excess sediment is linked to 

increasing contaminant and nutrient 

concentrations, all of which tributaries can 

transmit downstream, affecting water quality. 

Excess sediment may block and absorb 

sunlight transmission through the water 

column, inhibiting plant photosynthesis and 

warming the water in the stream. Sediment 

may fill the interstitial spaces between rocks 

in a streambed, which many fish and aquatic 

species use for mating, reproduction, and 

shelter from predators. This kind of physical 

degradation of tributary streambeds results in 

less suitable habitat available for animals and 

fish that move between upstream and 

downstream waters. Riparian waters that 

retain sediments thus protect downstream 

waters from the effects of excess sediment. 

Oxbow lakes play similar roles in the 

floodplain as they are an integral part of 

alluvial floodplains of meandering rivers. Id. 

at 5–42 (citing K.O. Winemiller, et al., ‘‘Fish 

Assemblage Structure in Relation to 

Environmental Variation among Brazos River 

Oxbow Lakes,’’ Transactions of the American 

Fisheries Society 129:451–468 (2000), K. 

Glinska-Lewczuk, ‘‘Water Quality Dynamics 

of Oxbow Lakes in Young Glacial Landscape 

of NE Poland in Relation to Their 

Hydrological Connectivity,’’ Ecological 

Engineering 35:25–37 (2009)). They connect 

to rivers by periodic overland flow, typically 

from the river during flooding events, and 

bidirectional shallow subsurface flow 

through fine river soils (bidirectional means 

flow from river to lake and lake to river). Id. 

at 5–43 to 5–44. Oxbow lakes generally have 

an important influence on the condition and 

function of rivers. Id. at 5–48 to 5–49. That 

influence can vary with the distance from the 

river and the age of the oxbow, reflecting the 

frequency and nature of the exchange of 

materials that takes place between the two 

water bodies. 

Because adjacent waters support riparian 

vegetation, they affect the capacity of riparian 

vegetation to influence stream flow, 

morphology, and habitat provided in the 

nearby water body. Vegetation in riparian 

waters influences the amount of water in the 

stream by capturing and transpiring stream 

flow and intercepting groundwater and 

overland flow. Id. at 3–22, 5–7 (citing P. 

Meyboom, ‘‘Three Observations on 

Streamflow Depletion by Phreatophytes,’’ 

Journal of Hydrology 2:248–261 (1964)). 

Riparian vegetation in adjacent waters also 

reduces stream bank erosion, serving to 

maintain the physical integrity of the 

channel. See, e.g., id. at 5–8 (citing C.E. 

Beeson and P. F. Doyle, ‘‘Comparison of Bank 

Erosion at Vegetated and Non-Vegetated 

Channel Bends,’’ Journal of the American 

Water Resources Association 31:983–990 

(1995)). In addition, inputs of woody debris 

from aquatic vegetation into waters make 

important contributions to the channel’s 

geomorphology and the stream’s aquatic 

habitat value. Id. (citing N.H. Anderson and 

J. R. Sedell, ‘‘Detritus Processing by 

Macroinvertebrates in Stream Ecosystems,’’ 

Annual Review of Entomology 24:351–377 

(1979); M.E. Harmon, et al., ‘‘Ecology of 

Coarse Woody Debris in Temperature 

Ecosystems,’’ Advances in Ecological 

Research 15:133–302 (1986); F. Nakamura 

and F. J. Swanson, ‘‘Effects of Coarse Woody 

Debris on Morphology and Sediment Storage 

of a Mountain Stream System in Western 

Oregon,’’ Earth Surface Processes and 

Landforms 18:43–61 (1993); T.E. Abbe and D. 

R. Montgomery, ‘‘Large Woody Debris Jams, 

Channel Hydraulics and Habitat Formation 

in Large Rivers,’’ Regulated Rivers: Research 

& Management 12:201–221 (1996); R.J. 

Naiman and H. Decamps, ‘‘The Ecology of 

Interfaces: Riparian Zones,’’ Annual Review 

of Ecology and Systematics 28:621–658 

91997); A.M. Gurnell, et al., ‘‘Large Wood 

and Fluvial Processes,’’ Freshwater Biology 

47:601–619 (2002)). Also, the riparian 

vegetation that overhangs streams provides 

shade, providing a critically important 

function of reducing fluctuations in water 

temperature helping to reduce excessive algal 

production and to maintain life-supporting 

oxygen levels in streams and other waters. Id. 

at 5–9 (citing S.V. Gregory, et al., ‘‘An 

Ecosystem Perspective of Riparian Zones: 

Focus on Links between Land and Water,’’ 

Bioscience 41:540–551 (1991); E.C. Volkmar 

and R.A. Dahlgren, ‘‘Biological Oxygen 

Demand Dynamics in the Lower San Joaquin 

River, California,’’ Environmental Science & 

Technology 40:5653–5660 (2006)). Even 

small changes in water temperature can have 

significant impacts on the type and number 

of species present in waters, with higher 

temperatures generally associated with 

degraded habitat which supports only those 

species that can tolerate higher temperatures 

and reduced levels of dissolved oxygen. 

Higher water temperatures are associated 

with streams and rivers with less valuable 

recreational and commercial fisheries. As 

discussed below, these physical 

characteristics of headwater streams 

influence what types of organisms live in the 

region. 

Headwaters and nearby wetlands supply 

downstream waters with dissolved organic 

carbon as a result of decomposition processes 

from dead organic matter such as plants. The 

biological consequences of this dissolved 

organic carbon are discussed in more detail 

below. The presence of dissolved organic 

carbon can affect how light penetrates the 

water, an important factor in the growth of 

plants, algae, and other primary producers, 

and can protect aquatic organisms from the 

harmful effects of UV–B radiation. Id. at 5– 

28 to 5–29 (citing K.N. Eshelman and H.F. 

Hemond, ‘‘The role of organic acids in the 

acid-base status of surface waters at Bickford 

Watershed, Massachusetts,’’ Water Resources 

Research 21:1503–1510 (1985); J.E. Hobbie 

and R.G. Wetzel, ‘‘Microbial control of 

dissolved organic carbon in lakes: Research 

for the future,’’ Hydrobiologia 229:169–180 

(1992); D.W. Schindler and P.J. Curtis, ‘‘The 

role of DOC in protecting freshwaters 

subjected to climate warming and 

acidification from UV exposure,’’ 

Biogeochemistry 36:1–8 (1997); K.R. Reddy 

and R.D. DeLaune, Biogeochemistry of 

Wetlands: Science and Applications, (Boca 

Raton, FL: CRC Press, 2008)). 

c. Riparian and Floodplain Waters 

Significantly Affect the Chemical Integrity of 

(a)(1) Through (a)(3) Waters 

As stated above in the section on 

tributaries, pollutants such as petroleum 

waste products and other harmful pollutants 

dumped into any part of the tributary system 

are likely to flow downstream, or to be 

washed downstream, and thereby pollute 

traditional navigable waters, interstate 


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waters, and the territorial seas from which 

American citizens take their drinking water, 

shellfish, fin fish, water-based recreation, and 

many other uses. Some wetlands perform the 

valuable function of trapping or filtering out 

some pollutants (such as fertilizers, silt, and 

some pesticides), thereby reducing the 

likelihood that those pollutants will reach 

and pollute the tributaries of the downstream 

navigable or interstate waters (and eventually 

pollute those downstream waters 

themselves). However, many other pollutants 

(such as petroleum wastes and toxic 

chemical wastes), if dumped into wetlands or 

other waters that are adjacent to tributary 

streams, may reach those tributaries 

themselves, and thereafter flow downstream 

to pollute the nation’s drinking water supply, 

fisheries, and recreation areas. 

Riparian and floodplain waters play a 

critical role in controlling the chemicals that 

enter streams and other ‘‘waters of the United 

States’’ and as a result are vital in protecting 

the chemical, physical, and biological 

integrity of downstream (a)(1) through (a)(3) 

waters. Runoff (the water that has not 

evaporated or infiltrated into the 

groundwater) from uplands is a large source 

of pollution, but research has shown that 

wetlands and other riparian waters trap and 

chemically transform a substantial amount of 

the nutrients, pesticides, and other pollutants 

before they enter streams, river, lakes and 

other waters. 

Chemicals and other pollutants enter 

waters from point sources, non-point sources, 

atmospheric deposition, upstream reaches, 

and through the hyporheic zone, a region 

beneath and alongside a stream bed where 

surface water and shallow groundwater mix. 

Id. at 5–10 (citing SW. Nixon and V.J. Lee, 

Wetlands and Water Quality: A Regional 

Review of Recent Research in the United 

States on the Role of Freshwater and 

Saltwater Wetlands as Sources, Sinks, and 

Transformers of Nitrogen, Phosphorus, and 

Various Heavy Metals, Technical Report Y– 

86–2, (Vicksburg, MS: U.S. Army Corp of 

Engineers, Waterways Experiment Station, 

1986); D.F. Whigham and T.E. Jordan, 

‘‘Isolated Wetlands and Water Quality,’’ 

Wetlands 23:541–549 (2003); S.L.Whitmire 

and S.K. Hamilton, ‘‘Rates of Anaerobic 

Microbial Metabolism in Wetlands of 

Divergent Hydrology on a Glacial 

Landscape,’’ Wetlands 28:703–714 (2008)). 

Throughout the stream network, but 

especially in headwater streams and their 

adjacent wetlands, chemicals are 

sequestered, assimilated, transformed, or lost 

to the atmosphere by microbes, fungi, algae, 

and macrophytes present in riparian waters 

and soils. Id. (citing SW. Nixon and V.J. Lee, 

Wetlands and Water Quality: A Regional 

Review of Recent Research in the United 

States on the Role of Freshwater and 

Saltwater Wetlands as Sources, Sinks, and 

Transformers of Nitrogen, Phosphorus, and 

Various Heavy Metals, Technical Report Y– 

86–2, (Vicksburg, MS: U.S. Army Corp of 

Engineers, Waterways Experiment Station, 

1986); C. Johnston, ‘‘Sediment and Nutrient 

Retention by Freshwater Wetlands: Effects on 

Surface Water Quality,’’ Critical Reviews in 

Environmental Control 21:491–565 (1991); 

P.I. Boon, ‘‘Biogeochemistry and Bacterial 

Ecology of Hydrologically Dynamic 

Wetlands,’’ in D.P. Batzer and R.R. Sharitz, 

ed., Ecology of Freshwater and Estuarine 

Wetlands (Berkeley, CA: University of 

California Press, 2006), pp. 115–176; W.J. 

Mitsch and J.G. Gosselink, Wetlands, 4th 

edition, (Hoboken, NJ: John Wiley & Sons 

Inc., 2007); K.R., Reddy and R.D. DeLaune, 

Biogeochemistry of Wetlands: Science and 

Applications (Boca Raton, FL: CRC Press, 

2008). These chemical processes reduce or 

eliminate pollution that would otherwise 

enter streams, rivers, lakes and other waters 

and subsequently downstream traditional 

navigable waters, interstate waters, or the 

territorial seas. The removal of the nutrients 

nitrogen and phosphorus is a particularly 

important role for riparian waters. Nutrients 

are necessary to support aquatic life, but the 

presence of excess nutrients can lead to 

eutrophication and the depletion of oxygen 

nearby waters and in waters far downstream. 

See, e.g., id. at 1–8. Eutrophication is a large 

problem in waters across the United States 

including such significant ecosystems as the 

Chesapeake Bay and Lake Spokane in 

Washington. W.M. Kemp, et al., 

‘‘Eutrophication of Chesapeake Bay: 

Historical Trends and Ecological 

Interactions,’’ Marine Ecology Progress Series 

303(21):1–29 (2005); D.J. Moore and J. Ross, 

Spokane River and Lake Spokane Dissolved 

Oxygen Total Maximum Daily Load: Water 

Quality Improvement Report, Publication No. 

07–10–073 (Spokane, WA: Washington State 

Department of Ecology, 2010); R.R. Murphy, 

et al., ‘‘Long-Term Trends in Chesapeake Bay 

Seasonal Hypoxia, Stratification, and 

Nutrient Loading,’’ Estuaries and Coasts 

34(6):1293–1309 (2011). Eutrophication is the 

process by which plants and algae grow in 

waters to such an extent that the abundance 

of vegetation monopolizes the available 

oxygen, detrimentally affecting other aquatic 

organisms. Id. Oxbow lakes also have high 

mineralization rates, suggesting that similar 

to adjacent wetlands they process and trap 

nutrients from runoff. Report at 5–45 to 5– 

46 (citing K.O. Winemiller, et al., ‘‘Fish 

Assemblage Structure in Relation to 

Environmental Variation among Brazos River 

Oxbow Lakes,’’ Transactions of the American 

Fisheries Society 129:451–468 (2000)). 

Protection of these waters therefore helps 

maintain the chemical integrity of the 

nation’s waters. 

The removal of nitrogen is an important 

function of all waters, including wetlands, in 

the riparian areas. Riparian areas regularly 

remove more than half of dissolved nitrogen 

found in surface and subsurface water by 

plant uptake and microbial transformation. 

Id. at 5–11 (citing P. Vidon, et al., ‘‘Hot Spots 

and Hot Moments in Riparian Zones: 

Potential for Improved Water Quality 

Management,’’ Journal of the American 

Water Resources Association 46:278–298 

(2010)). Denitrification in surface and 

subsurface flows is highest where there is 

high organic matter and/or anoxic 

conditions. Id. Denitrification occurs in 

wetland soils where there is high organic 

matter, low oxygen, denitrifying microbes, 

and saturated soil conditions, and rates 

increase with proximity to streams. Id. (citing 

S.V. Gregory, et al., ‘‘An Ecosystem 

Perspective of Riparian Zones: Focus on 

Links between Land and Water,’’ Bioscience 

41:540–551 (1991); P. Vidon, et al., ‘‘Hot 

Spots and Hot Moments in Riparian Zones: 

Potential for Improved Water Quality 

Management,’’ Journal of the American 

Water Resources Association 46:278–298 

(2010)). Riparian waters are therefore 

important in maintaining the conditions 

important for denitrification, which in turn 

protects streams, rivers, lakes and other 

waters from nitrogen pollution. 

Plant uptake of dissolved nitrogen in 

subsurface flows also accounts for large 

quantities of nitrogen removal. Riparian 

forests have been found to remove 75% of 

dissolved nitrate transported from 

agricultural fields in Maryland. Id. (citing P. 

Vidon, et al., ‘‘Hot Spots and Hot Moments 

in Riparian Zones: Potential for Improved 

Water Quality Management,’’ Journal of the 

American Water Resources Association 

46:278–298 (2010)). Likewise, riparian forests 

in Georgia remove 65% of nitrogen and 30% 

of phosphorus from agricultural sources. Id. 

at 5–11 to 5–12 (citing Vidon, et al. 2010). A 

Pennsylvania forest removed 26% of the 

nitrate from the subsurface. Id. at 5–12 (citing 

J.D. Newbold, et al., ‘‘Water Quality 

Functions of a 15-Year-Old Riparian Forest 

Buffer System,’’ Journal of the American 

Water Resources Association 46:299–310 

(2010)). The vegetation associated with 

riparian waters also removes nitrogen from 

subsurface flows. Therefore, the conservation 

of riparian waters helps protect downstream 

waters from influxes of dissolved nitrogen. 

Phosphorus is another potentially harmful 

nutrient that is captured and processed in 

riparian waters. Id. (citing T.A. Dillaha and 

S.P. Inamdar, ‘‘Buffer Zones as Sediment 

Traps or Sources,’’ in N.E. Haycock, T.P. 

Burt, K.W.T. Goulding, and G. Pinay, ed., 

Buffer Zones: Their Processess and Potential 

in Water Protection, Proceedings of the 

International Conference on Buffer Zones, 

September 1996 (Hertfordshire, UK: Quest 

Environmental, 1997), pp. 33–42; A.N. 

Sharpley and S. Rekolainen, ‘‘Phosphorus in 

Agriculture and Its Environmental 

Implications,’’ in H. Tunney, et al., ed., 

Phosphorus Losses from Soil to Water 

(Cambridge, UK: CAB International, 1997), 

pp. 1–54; G.C. Carlyle and A.R. Hill, 

‘‘Groundwater Phosphate Dynamics in a 

River Riparian Zone: Effects of Hydrologic 

Flowpaths, Lithology, and Redox 

Chemistry,’’ Journal of Hydrology 247:151– 

168 (2001)). Biogeochemical processes, 

sedimentation, and plant uptake account for 

high rates of removal of particulate 

phosphorus in riparian areas. Id. (citing C.C. 

Hoffmann, et al., ‘‘Phosphorus Retention in 

Riparian Buffers: Review of Their 

Efficiency,’’ Journal of Environmental 

Quality 38:1942–1955 (2009)). The amount of 

contact the water has with nearby soils 

determines the ability of the riparian area to 

remove phosphorus. Id. This function of 

upstream riparian waters is crucial for 

maintaining the chemical and biological 

integrity of the waters to which they are 

adjacent, and for preventing eutrophication 

in downstream traditional navigable waters, 

interstate waters, and the territorial seas. 


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Federal Register / Vol. 79, No. 76 / Monday, April 21, 2014 / Proposed Rules 22239 

d. Riparian and Floodplain Waters 

Significantly Affect the Biological Integrity of 

(a)(1) Through (a)(3) Waters 

Waters and wetlands located in both 

riparian areas and floodplains support the 

biological integrity of downstream (a)(1) 

through (a)(3) waters in a variety of ways. 

They provide habitat for aquatic and watertolerant plants, invertebrates, and vertebrates, 

and provide feeding, refuge, and breeding 

areas for invertebrates and fish. Seeds, plants, 

and animals move between waters in the 

riparian zone and floodplains and the 

adjacent streams, and from there colonize or 

utilize downstream waters, including 

traditional navigable waters. 

Organic matter from adjacent wetlands is 

critical to aquatic food webs, particularly in 

headwaters, where it is the primary source of 

energy flow due to low light conditions that 

inhibit photosynthesis. Id. at 5–13 (citing J.L. 

Tank, et al., ‘‘A Review of Allochthonous 

Organic Matter Dynamics and Metabolism in 

Streams,’’ Journal of the North American 

Benthological Society 29:118–146 (2010)). 

Headwater streams tend to be located in 

heavily vegetated areas compared to larger 

waters, so they are more likely to contain leaf 

litter, dead and decaying plants, and other 

organic matter that forms the basis of 

headwater food webs. The organic matter is 

processed by microbes and insects that make 

the energy available to higher levels of stream 

life such as amphibians and fish. Studies 

have shown that macroinvertebrates rely on 

leaf inputs in headwater streams and that 

excluding organic litter from a stream 

resulted in significant changes to the food 

web at multiple levels. Id. (citing G.W. 

Minshall, ‘‘Role of Allochthonous Detritus in 

the Tropic Structure of a Woodland 

Springbrook Community,’’ Ecology 48:139– 

149 (1967); J.B. Wallace, et al., ‘‘Multiple 

Trophic Levels of a Forest Stream Linked to 

Terrestrial Litter Inputs,’’ Science 277:102– 

104 (1997); J.L. Meyer, et al., ‘‘Leaf Litter as 

a Source of Dissolved Organic Carbon in 

Streams,’’ Ecosystems 1:240–249 (1998)). 

Fish and amphibian species found in 

headwaters travel downstream and in turn 

become part of the food web for larger 

aquatic organisms in rivers and other waters. 

Organic material provided by riparian waters 

to small, headwater streams is therefore 

important not only to the small streams that 

directly utilize this source of energy to 

support their biological populations but also 

to the overall biological integrity of 

downstream waters that also benefit from the 

movement of fish and other species that 

contribute to the food web of larger streams 

and rivers. 

Floodplain water bodies, including oxbow 

lakes, accumulate organic carbon, an 

important function influenced by the size 

and frequency of floods from adjacent rivers. 

See, e.g., id. at 5–45 (citing A. Cabezas, et al., 

‘‘Changing Patterns of Organic Carbon and 

Nitrogen Accretion on the Middle Ebro 

Floodplain (NE Spain),’’ Ecological 

Engineering 35:1547–1558 (2009)). These 

stored chemicals are available for exchange 

with river water when hydrological 

connections form. Organic materials are the 

basis for the food web in stream reaches 

where photosynthetic production of energy is 

absent or limited, particularly in headwater 

systems where vegetative litter alone makes 

up the base of the aquatic food web. The 

maintenance of floodplain waters is therefore 

an important component of protecting the 

biological integrity of downstream waters 

into which the headwaters flow. 

The waters, including wetlands, in the 

riparian area play an important role in the 

removal of pesticides. Id. at 5–14 (citing P. 

Vidon, et al., ‘‘Hot Spots and Hot Moments 

in Riparian Zones: Potential for Improved 

Water Quality Management,’’ Journal of the 

American Water Resources Association 

46:278–298 (2010). Microbes near plant roots 

break down these pesticides. See, e.g., id. 

(citing G. Voos, and P.M. Groffman, 

‘‘Relationships between microbial biomass 

and dissipation of 2,4–D and dicamba in 

soil,’’ Biology and Fertility of Soils 24:106– 

110 (1996)). Uptake by aquatic plants has 

also been shown to be an important 

mechanism of removal of the pesticides 

alachlor and atrazine. Id. (citing K.G. 

Paterson and J.L. Schnoor, ‘‘Fate of Alachlor 

and Atrazine in a Riparian Zone Field Site,’’ 

Water Environment Research 64:274–283 

(1992)). Riparian waters also trap and hold 

pesticide contaminated runoff preventing it 

from harming neighboring waters. 

Riparian areas are dynamic places that 

support a diversity of aquatic, amphibious, 

and terrestrial species adapted to the unique 

habitat created by periodic flooding events. 

Id. at 5–15 (citing W.J. Junk, et al., ‘‘The flood 

pulse concept in river-floodplain systems,’’ 

in D.P. Dodge, ed., Proceedings of the 

International Large River Symposium Ottawa 

(Ottawa, Canada: Canadian Special 

Publication of Fisheries and Aquatic 

Sciences 106, 1989), pp. 110–127; K. 

Tockner, et al., ‘‘An Extension of the Flood 

Pulse Concept,’’ Hydrological Processes 

14:2861–2883 (2000); C.T. Robinson, et al., 

‘‘The Fauna of Dynamic Riverine 

Landscapes,’’ Freshwater Biology 47:661–677 

(2002)). Plants, invertebrates, and vertebrates 

use waters, including wetlands, in the 

riparian areas for habitat, nutrients, and 

breeding. As a result, the waters, including 

wetlands, in the riparian areas act as sources 

of organisms, particularly during inundation 

events, replenishing neighboring waters with 

organisms, seeds, and organic matter. 

Inundation and hydrological connectivity of 

riparian areas greatly increase the area of 

aquatic habitats and species diversity. Id. at 

5–15 to 5–16 (citing W.J. Junk et al. 1989; R. 

Jansson, et al., ‘‘Hydrochory Increases 

Riparian Plant Species Richness: A 

Comparison between a Free-Flowing and a 

Regulated River,’’ Journal of Ecology 

93:1094–1103 (2005)). Aquatic animals, 

including amphibians and fish, take 

advantage of the waters present in riparian 

areas, either inhabiting them or moving 

between the riparian water and neighboring 

waters. Id. at 5–15, 5–17, 5–19 (citing G.H. 

Copp, ‘‘The habitat diversity and fish 

reproductive function of floodplain 

ecosystems,’’ Environmental Biology of 

Fishes 26:1–27 (1989); L.A. Smock, et al., 

‘‘Lotic macroinvertebrate production in three 

dimensions: Channel surface, hyporheic, and 

floodplain environments,’’ Ecology 73:876– 

886 (1992); L.A. Smock, ‘‘Movements of 

invertebrates between stream channels and 

forested floodplains,’’ Journal of the North 

American Benthological Society 13:524–531 

(1994); C. T. Robinson, et al., ‘‘The fauna of 

dynamic riverine landscapes,’’ Freshwater 

Biology 47:661–677 (2002); J.S. Richardson, 

et al., ‘‘Riparian communities associated with 

Pacific Northwest headwater streams: 

Assemblages, processes, and uniqueness,’’ 

Journal of the American Water Resources 

Association 41:935–947 (2005); C. Ilg, et al., 

‘‘Long-term reactions of plants and 

macroinvertebrates to extreme floods in 

floodplain grasslands,’’ Ecology 89:2392– 

2398 (2008); D.E. Shoup, and D. H. Wahl, 

‘‘Fish diversity and abundance in relation to 

interannual and lakespecific variation in 

abiotic characteristics of floodplain lakes of 

the lower Kaskaskia River, Illinois,’’ 

Transactions of the American Fisheries 

Society 138:1076–1092 (2009)). Likewise, 

seeds, plant fragments, and whole plants 

move between riparian and floodplain waters 

and the river network. Id. at 5–15 (citing R.L. 

Schneider, and R.R. Sharitz, ‘‘Hydrochory 

and regeneration in a bald cypress water 

tupelo swamp forest,’’ Ecology 69:1055–1063 

(1988); B. Middleton, ‘‘Hydrochory, seed 

banks, and regeneration dynamics along the 

landscape boundaries of a forested wetland,’’ 

Plant Ecology 146:169–184 (2000); C. 

Nilsson, et al., ‘‘The role of hydrochory in 

structuring riparian and wetland vegetation,’’ 

Biological Reviews 85:837–858 (2010)). 

Hydrological connections are often drivers 

of biological connections, and flooding 

events enhance the existing connections 

between floodplain waters and the river 

network. As a result, waters within 

floodplains have important functions for 

aquatic health. Many species have cycles 

timed to flooding events, particularly in 

circumstances where flooding is associated 

with annual spring snowmelt or high 

precipitation. Id. at 5–15 to 5–17, 5–20 (citing 

J.R. Thomas, et al., ‘‘A landscape perspective 

of the stream corridor invasion and habitat 

characteristics of an exotic (Dioscorea 

oppositifolia) in a pristine watershed in 

Illinois,’’ Biological Invasions 8:1103–1113 

(2006); L.M. Tronstad, et al., ‘‘Aerial 

colonization and growth: Rapid invertebrate 

responses to temporary aquatic habitats in a 

river floodplain,’’ Journal of the North 

American Benthological Society 26:460–471 

(2007); A. Gurnell, et al., ‘‘Propagule 

deposition along river margins: Linking 

hydrology and ecology,’’ Journal of Ecology 

96:553–565 (2008)). Waters within 

floodplains act as sinks of seeds, plant 

fragments, and invertebrate eggs, allowing for 

cross-breeding and resulting gene flow across 

time. Id. at 5–19 to 5–21 (citing K.M. Jenkins, 

and A.J. Boulton, ‘‘Connectivity in a dryland 

river: Short-term aquatic microinvertebrate 

recruitment following floodplain 

inundation,’’ Ecology 84:2708–2723 (2003); 

D. Frisch, and S.T. Threlkeld, ‘‘Floodmediated dispersal versus hatching: Early 

recolonisation strategies of copepods in 

floodplain ponds,’’ Freshwater Biology 

50:323–330 (2005); B. Vanschoenwinkel, et 

al., ‘‘Wind mediated dispersal of freshwater 

invertebrates in a rock pool metacommunity: 

Differences in dispersal capacities and 

modes,’’ Hydrobiologia 635:363–372 (2009)). 


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Micro- and macroinvertebrates colonize 

nutrient rich waters within floodplains 

during periods of inundation, facilitating an 

increase in population and sustaining them 

though times of limited resources and 

population decline. Id. at 5–19 (citing W.J. 

Junk, et al., ‘‘The flood pulse concept in 

river-floodplain systems,’’ in D.P. Dodge, ed., 

Proceedings of the International Large River 

Symposium Ottawa (Ottawa, Canada: 

Canadian Special Publication of Fisheries 

and Aquatic Sciences 106, 1989), pp. 110– 

127; B. Malmqvist, ‘‘Aquatic invertebrates in 

riverine landscapes,’’ Freshwater Biology 

47:679–694 (2002); C. Ilg, et al., ‘‘Long-term 

reactions of plants and macroinvertebrates to 

extreme floods in floodplain grasslands,’’ 

Ecology 89:2392–2398 (2008)). Such animals 

are adapted to high floods, desiccation 

(drying out), or other stresses that come with 

these regular, systemic fluctuations. Id. at 5– 

20 (citing Jenkins and Boulton 2003). 

Floodplain waters therefore maintain various 

biological populations, which periodically 

replenish adjacent jurisdictional waters, 

serving to maintain their biological integrity. 

Plants and animals use waters, including 

wetlands, in the riparian areas and 

floodplains for habitat, food, and breeding. 

Oxbow lakes in the floodplain provide 

critical fish habitat needed for feeding and 

rearing, leading researchers to conclude that 

the entire floodplain should be considered a 

single functional unit, essential to the river’s 

biological integrity. Id. at 5–17 (citing D.E. 

Shoup and D.H. Wahl, ‘‘Fish Diversity and 

Abundance in Relation to Interannual and 

Lake-Specific Variation in Abiotic 

Characteristics of Floodplain Lakes of the 

Lower Kaskaskia River, Illinois,’’ 

Transactions of the American Fisheries 

Society 138:1076–1092 (2009)). Since 

adjacent ponds are structurally and 

biologically similar to oxbow lakes they serve 

similar functions relative to the nearby river 

or stream. Waters, including wetlands, in the 

riparian areas also provide food sources for 

stream invertebrates, which colonize during 

inundation events. Id. at 5–19 (citing W.J. 

Junk, et al., ‘‘The Flood Pulse Concept in 

River-Floodplain Systems,’’ in D.P. Dodge, 

ed., Proceedings of the International Large 

River Symposium Ottawa (Ottawa, Canada: 

Canadian Special Publication of Fisheries 

and Aquatic Sciences 106, 1989), pp. 110– 

127; C. Ilg, et al., ‘‘Long-term Reactions of 

Plants and Macroinvertebrates to Extreme 

Floods in Floodplain Grasslands,’’ Ecology 

89:2392–2398 (2008)). Riparian waters also 

form an integral part of the food web, linking 

primary producers and plants to higher 

animals. Id. (citing B. Malmqvist, ‘‘Aquatic 

Invertebrates in Riverine Landscapes,’’ 

Freshwater Biology 47:679–694 (2002); 

G.U.Y. Woodward and A.G. Hildrew, ‘‘Food 

Web Structure in Riverine Landscapes,’’ 

Freshwater Biology 47:777–798 (2002), T.K. 

Stead, et al., ‘‘Secondary Production of a 

Stream Metazoan Community: Does the 

Meiofauna Make a Difference?,’’ Limnology 

and Oceanography 50:398–403 (2005), D.J. 

Woodford and A.R. McIntosh, ‘‘Evidence of 

Source-Sink Metapopulations in a Vulnerable 

Native Galaxiid Fish Driven by Introduced 

Trout,’’ Ecological Applications 20:967–977 

(2010)). Likewise, floodplains are important 

foraging, hunting, and breeding sites for fish 

and amphibians. Id. at 5–15 (citing G.H. 

Copp, ‘‘The Habitat Diversity and Fish 

Reproductive Function of Floodplain 

Ecosystems,’’ Environmental Biology of 

Fishes 26:1–27 (1989); J.S. Richardson, et al., 

‘‘Riparian Communities Associated with 

Pacific Northwest Headwater Streams: 

Assemblages, Processes, and Uniqueness,’’ 

Journal of the American Water Resources 

Association 41:935–947 (2005)). 

Plants and animals move back and forth 

between riparian or floodplain waters and 

the river network. This movement is assisted 

in some cases when flooding events create 

hydrological connections. For instance, these 

floodplain and riparian wetlands provide 

refuge, feeding, and rearing habitat for many 

fish species. Id. at 5–17 (citing C.H. Wharton, 

et al., The Ecology of Bottomland Hardwood 

Swamps of the Southeast: A Community 

Profile, FWS/OBS–81/37 (Washington, DC: 

U.S. Department of the Interior, Fish and 

Wildlife Service, Biological Services 

Program, 1982); M.P. Matheney and C.F. 

Rabeni, ‘‘Patterns of Movement and Habitat 

Use by Northern Hogsuckers in an Ozark 

Stream,’’ Transactions of the American 

Fisheries Society 124:886–897 (1995); A.A. 

Pease, et al., ‘‘Habitat and Resource Use by 

Larval and Juvenile Fishes in an Arid-Land 

River (Rio Grande, New Mexico),’’ 

Freshwater Biology 51:475–486 (2006); J.A. 

Henning, et al., ‘‘Use of Seasonal Freshwater 

Wetlands by Fishes in a Temperate River 

Floodplain,’’ Journal of Fish Biology 71:476– 

492 (2007); C.A. Jeffres, et al., ‘‘Ephemeral 

Floodplain Habitats Provide Best Growth 

Conditions for Juvenile Chinook Salmon in a 

California River,’’ Environmental Biology of 

Fishes 83:449–458 (2008)). Seeds ingested by 

animals such as carp are dispersed in stream 

channels and associated waters. See, e.g., id. 

at 5–16 (citing B.J.A. Pollux, et al., 

‘‘Consequences of Intraspecific Seed-Size 

Variation in Sparganium emersum for 

Dispersal by Fish,’’ Functional Ecology 

21:1084–1091 (2007)). Also, phytoplankton 

move between floodplain wetlands and the 

river network. Id. at 5–17 (citing D.G. 

Angeler, et al., ‘‘Phytoplankton community 

similarity in a semiarid floodplain under 

contrasting hydrological connectivity 

regimes,’’ Ecological Research 25:513–520 

(2010)). In turn, the primary productivity 

conditions in the floodplain results in large 

populations of phytoplankton that enrich 

river networks when hydrological 

connections form. Id. (citing P.W. Lehman, et 

al., ‘‘The Influence of Floodplain Habitat on 

the Quantity and Quality of Riverine 

Phytoplankton Carbon Produced During the 

Flood Season in San Francisco Estuary,’’ 

Aquatic Ecology 42:363–378 (2008)). This 

influx of carbon into the river system 

nourishes the downstream waters, for 

example, supporting fisheries. 

However, even when hydrological 

connections are absent, some organisms can 

move between riparian waters and their 

neighboring tributaries by overland 

movement in order to complete their life 

cycle. River-dwelling mammals, such as river 

otters, move from the river to riparian 

wetlands. Id. at 5–18 (citing D.G. Newman 

and C.R. Griffin, ‘‘Wetland Use by River 

Otters in Massachusetts,’’ Journal of Wildlife 

Management 58:18–23 (1994)). Several 

species of amphibians and reptiles including 

frogs, snakes and turtles use both streams and 

neighboring waters. Id. at 1–10, 5–4 to 5–5 

(Table 5–1), 5–15 (citing J.S. Richardson, et 

al., ‘‘Riparian Communities Associated with 

Pacific Northwest Headwater Streams: 

Assemblages, Processes, and Uniqueness,’’ 

Journal of the American Water Resources 

Association 41:935–947 (2005)). Movement 

between wetlands and the river network also 

occurs by the dispersal of seed and plant 

fragments and the wind dispersal of 

invertebrates. Id. at 5–15, 5–20 (citing R.L. 

Schneider and R.R. Sharitz, ‘‘Hydrochory and 

Regeneration in a Bald Cypress Water Tupelo 

Swamp Forest,’’ Ecology 69:1055–1063 

(1988); B. Middleton, ‘‘Hydrochory, Seed 

Banks, and Regeneration Dynamics Along the 

Landscape Boundaries of a Forested 

Wetland,’’ Plant Ecology 146:169–184 (2000); 

A.M. Gurnell, ‘‘Analogies Between Mineral 

Sediment and Vegetative Particle Dynamics 

in Fluvial Systems,’’ Geomorphology 89:9–22 

(2007); A. Gurnell, et al., ‘‘Propagule 

Deposition Along River Margins: Linking 

Hydrology and Ecology,’’ Journal of Ecology 

96:553–565 (2008); C. Nilsson, et al., ‘‘The 

Role of Hydrochory in Structuring Riparian 

and Wetland Vegetation,’’ Biological Reviews 

85:837–858 (2010); L.M. Tronstad, et al., 

‘‘Aerial Colonization and Growth: Rapid 

Invertebrate Responses to Temporary Aquatic 

Habitats in a River Floodplain,’’ Journal of 

the North American Benthological Society 

26:460–471 (2007)). Animals, particularly 

migratory fish, may thus move between 

adjacent waters and (a)(1) through (a)(3) 

waters. And even when some species do not 

traverse the entire distance from adjacent 

waters to downstream waters, the 

downstream waters still benefit from the 

ecological integrity that persists because of 

the close relationship that adjacent waters 

have with nearby waters. This is because the 

chemical and biological properties that arise 

from interactions between adjacent waters 

and tributaries move downstream and 

support the integrity of (a)(1) through (a)(3) 

waters. 

Biological connections between adjacent 

waters and river systems do not always 

increase with hydrologic connections. In 

some cases, the lack of connection improves 

the biological contribution provided by 

riparian waters towards neighboring streams, 

rivers, and lakes. For instance, the periodic 

hydrologic disconnectedness of oxbow lakes 

is necessary for the accumulation of 

plankton, an important source of carbon 

more easily assimilated by the aquatic food 

chain than terrestrial forms of carbon. Id. at 

5–46 (citing C. Baranyi, et al., ‘‘Zooplankton 

Biomass and Community Structure in a 

Danube River Floodplain System: Effects of 

Hydrology,’’ Freshwater Biology 47:473–482 

(2002); S. Keckeis, et al., ‘‘The Significance 

of Zooplankton Grazing in a Floodplain 

System of the River Danube,’’ Journal of 

Plankton Research 25:243–253 (2003)). 

Similarly, some degree of hydrological 

disconnectedness is important in increasing 

the number of mollusk species and 

macroinvertebrate diversity in oxbow lakes, 

which in turn support the diversity of 


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Federal Register / Vol. 79, No. 76 / Monday, April 21, 2014 / Proposed Rules 22241 

mollusks throughout the aquatic system. Id. 

at 5–46 to 5–47 (citing W. Reckendorfer, et 

al., ‘‘Floodplain Restoration by Reinforcing 

Hydrological Connectivity: Expected Effects 

on Aquatic Mollusc Communities,’’ Journal 

of Applied Ecology 43:474–484 (2006); K. 

Obolewski, et al., ‘‘Effect of Hydrological 

Connectivity on the Molluscan Community 

Structure in Oxbow Lakes of the Lyna River,’’ 

Oceanological and Hydrobiological Studies 

38:75–88 (2009). 

2. Confined Surface and Shallow Subsurface 

Hydrologic Connections Significantly Affect 

the Chemical, Physical, or Biological 

Integrity of (a)(1) Through (a)(3) Waters 

Wetlands and open waters, including those 

outside the riparian zone and floodplain, can 

be connected downstream through 

unidirectional flow from the wetland or open 

water to a nearby tributary. Such connections 

can occur through a confined surface or a 

shallow subsurface hydrologic connection. 

Report at 3–7, 5–23. Outside of the riparian 

zone and floodplain, surface hydrologic 

connections between adjacent waters and 

jurisdictional waters can occur via confined 

flows (e.g. a swale, gully, ditch, or other 

discrete feature). For purposes of this rule, 

confined surface connections are defined as 

permanent, intermittent or ephemeral surface 

connections through directional flowpaths, 

such as (but not limited to) swales, gullies, 

rills, and ditches. In some cases, these 

connections will be a result of ‘‘fill and spill’’ 

hydrology. A directional flowpath is a path 

where water flows repeatedly from the 

wetland or open water to the nearby 

jurisdictional water that at times contains 

water originating in the wetland or open 

water as opposed to just directly from 

precipitation. For the purposes of this rule, 

‘‘fill and spill’’ describes situations where 

wetlands or open waters fill to capacity 

during intense precipitation events or high 

cumulative precipitation over time and then 

spill to the downstream jurisdictional water. 

Id. at 5–62 (citing T.C. Winter and D.O. 

Rosenberry, ‘‘Hydrology of Prairie Pothole 

Wetlands during Drought and Deluge: A 17- 

year Study of the Cottonwood Lake Wetland 

Complex in North Dakota in the Perspective 

of Longer Term Measured and Proxy 

Hydrological Records,’’ Climatic Change 

40:189–209 (1998); S.G. Leibowitz, and K.C. 

Vining, ‘‘Temporal connectivity in a prairie 

pothole complex,’’ Wetlands 23:13–25 

(2003)). Water connected through such flows 

originate from the adjacent wetland or open 

water, travel to the downstream jurisdictional 

water, and are connected to those 

downstream waters by swales or other 

directional flowpaths on the surface. 

A confined surface hydrologic connection, 

which may be perennial, intermittent or 

ephemeral, supports periodic flows between 

the adjacent water and the jurisdictional 

water. For example, wetland seeps are likely 

to have perennial connections to streams that 

provide important sources of baseflow, 

particularly during summer. Id. at 5–22 

(citing T.R. Morley, et al., ‘‘The Role of 

Headwater Wetlands in Altering Streamflow 

and Chemistry in a Maine, USA catchment,’’ 

Journal of the American Water Resources 

Association 47:337–349 (2011)). Other 

wetlands are connected to streams via 

intermittent or ephemeral conveyances and 

can contribute flow to downstream waters via 

their surface hydrologic connection. Id. at 5– 

22 (citing M.C. Rains, et al., ‘‘The Role of 

Perched Aquifers in Hydrological 

Connectivity and Biogeochemical Processes 

in Vernal Pool Landscapes, Central Valley, 

California,’’ Hydrological Processes 20:1157– 

1175 (2006); M.C. Rains, et al., ‘‘Geological 

Control of Physical and Chemical Hydrology 

in California Vernal Pools,’’ Wetlands 

28:347–362 (2008); B.P. Wilcox, et al., 

‘‘Evidence of Surface Connectivity for Texas 

Gulf Coast Depressional Wetlands,’’ 

Wetlands 31:451–458 (2011)).The surface 

hydrologic connection of the neighboring 

water to the jurisdictional water and the 

close proximity of the waters enhance the 

neighboring waters substantial effects the 

waters have on downstream (a)(1) through 

(a)(3) waters. Wetlands and open waters that 

are connected to (a)(1) through (a)(5) waters 

through a confined surface hydrologic 

connection will have an impact on 

downstream (a)(1) through (a)(3) waters, 

regardless of whether the outflow is 

permanent, intermittent, or ephemeral. See, 

e.g., id. at 5–1 to 5–2. 

Wetlands and open waters with confined 

surface connections can affect the physical 

integrity of waters to which they connect. 

Such waters can provide an important source 

of baseflow to the streams to which they are 

adjacent, helping to sustain the water levels 

in the nearby streams. Id. at 5–22 (citing T.R. 

Morley, et al., ‘‘The Role of Headwater 

Wetlands in Altering Streamflow and 

Chemistry in a Maine, USA catchment,’’ 

Journal of the American Water Resources 

Association 47:337–349 (2011); M.C. Rains, 

et al., ‘‘The Role of Perched Aquifers in 

Hydrological Connectivity and 

Biogeochemical Processes in Vernal Pool 

Landscapes, Central Valley, California,’’ 

Hydrological Processes 20:1157–1175 (2006); 

M.C. Rains, et al., ‘‘Geological Control of 

Physical and Chemical Hydrology in 

California Vernal Pools,’’ Wetlands 28:347– 

362 (2008); B.P. Wilcox, et al., ‘‘Evidence of 

Surface Connectivity for Texas Gulf Coast 

Depressional Wetlands,’’ Wetlands 31:451– 

458 (2011)) and T.M. Lee, et al., Effect of 

Groundwater Levels and Headwater 

Wetlands on Streamflow in the Charlie Creek 

Basin, Peace River Watershed, West-Central 

Florida, U.S. Geological Survey Scientific 

Investigations Report 2010–5189 (Reston, 

Virginia: U.S. Department of the Interior, U.S. 

Geological Survey, 2010). Waters with a 

confined surface connection to downstream 

jurisdictional waters can affect streamflow by 

altering baseflow or stormflow through 

several mechanisms, including surface 

storage and groundwater recharge. Report at 

5–25. Wetlands effectively store water 

because the entire aboveground portion of 

the wetland basin is available for water 

storage, in contrast to upland areas where 

soil particles or rock reduce water storage 

volume for a given volume of that soil or rock 

(i.e., the specific yield). Id. at 5–25 (citing 

A.I. Johnson, Specific Yield—Compilation of 

Specific Yields for Various Materials, USGS 

Water Supply Paper 1662–D (Washington, 

DC: U.S. Department of the Interior, U.S. 

Geological Survey, 1967)). By storing water, 

these waters can reduce peak streamflow, 

and thus, downstream flooding. Id. at 5–25 

(citing A. Bullock, and M. Acreman, ‘‘The 

Role of Wetlands in the Hydrological Cycle,’’ 

Hydrology and Earth System Sciences 7:358– 

389 (2003); P. McEachern, et al., ‘‘Landscape 

Control of Water Chemistry in Northern 

Boreal Streams of Alberta,’’ Journal of 

Hydrology 323:303–324 (2006)). Antecedent 

moisture conditions, available wetland 

storage, and evaporation rates could impact 

water storage, as some waters connected to 

jurisdictional waters via discrete features 

may actually reduce flows in the streams 

they neighbor during dry periods. Id. at 5– 

26 (citing A. Bullock, and M. Acreman, ‘‘The 

Role of Wetlands in the Hydrological Cycle,’’ 

Hydrology and Earth System Sciences 7:358– 

389 (2003)). Thus, wetlands and open waters 

with a confined hydrologic connection to 

jurisdictional waters may function as a sink 

in dry periods if storage capacity is not 

exceeded and evaporation rates surpass 

groundwater recharge. Id. at 5–26 to 5–27. 

Wetlands and open waters with confined 

surface connections can affect the chemical 

integrity of waters to which they connect. 

Such waters can affect water quality of 

jurisdictional waters through source and sink 

functions, often mediated by transformation 

of chemical constituents. The surface 

hydrologic connections to nearby 

jurisdictional waters provide pathways for 

materials transformed in the wetlands and 

open waters (such as methylmercury or 

degraded organic matter) to reach and affect 

the nearby waters and the downstream (a)(1) 

through (a)(3). Id. at 5–27. Functions that 

occur in the wetlands and open waters can 

affect downstream (a)(1) through (a)(3) waters 

when compounds that are transformed in 

wetland environments move to downstream 

waters via the surface hydrologic connection. 

Id. at 5–28 (citing T.C. Winter and J.W. 

LaBaugh, ‘‘Hydrologic Considerations in 

Defining Isolated Wetlands,’’ Wetlands 

23:532–540 (2003)). For example, 

methylmercury (which can form in 

peatlands) can be transported through 

entrainment with organic matter exports, and 

can move through surface flows from 

peatlands with confined surface connections 

to downstream waters. Id. at 5–28 (citing O. 

Linqvist, et al., ‘‘Mercury in the Swedish 

Environment—Recent Research on Causes, 

Consequences, and Remedial Measures,’’ 

Water Air and Soil Pollution 55:xi–xiii 

(1991); G. Mierle, and R. Ingram, ‘‘The Role 

of Humic Substances in the Mobilization of 

Mercury from Watersheds,’’ Water Air and 

Soil Pollution 56:349–357 (1991); V.L. St. 

Louis, et al., ‘‘Importance of Wetlands as 

Sources of Methyl mercury to Boreal Forest 

Ecosystems,’’ Canadian Journal of Fisheries 

and Aquatic Sciences 51:1065–1076 (1994); 

C.T. Driscoll, et al., ‘‘The Role of Dissolved 

Organic Carbon in the Chemistry and 

Bioavailability of Mercury in Remote 

Adirondack Lakes,’’ Water Air and Soil 

Pollution 80:499–508 (1995); P. Porvari, and 

M. Verta, ‘‘Total and Methyl mercury 

Concentrations and Fluxes from Small Boreal 

Forest Catchments in Finland,’’ 

Environmental Pollution 123:181–191 

(2003)). The mercury that is transported 

downstream can enter the food chains of the 


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(a)(1) through (a)(3) waters and negatively 

impact wildlife inhibiting those downstream 

waters. Id. at 5–28. Export of dissolved 

organic matter from neighboring waters 

connected via a confined surface connection 

can have potentially negative effects on 

downstream waters because contaminants, 

such as MeHg and other trace metals, can be 

adsorbed to the organic matter. Id. at 5–28 

(citing E.M. Thurman, Organic Geochemistry 

of Natural Waters (Boston, MA: Martinus 

Nijhoff/Dr. W. Junk Publishers, 1985); C.T. 

Driscoll, et al., ‘‘The Role of Dissolved 

Organic Carbon in the Chemistry and 

Bioavailability of Mercury in Remote 

Adirondack Lakes,’’ Water Air and Soil 

Pollution 80:499–508 (1995)). Dissolved 

organic matter, however, is also an important 

source of energy for downstream aquatic 

communities. Id. at 5–28 (citing J.E. Hobbie 

and R.G. Wetzel, ‘‘Microbial control of 

dissolved organic carbon in lakes: Research 

for the future,’’ Hydrobiologia 229:169–180 

(1992); K.R. Reddy and R.D. DeLaune, 

Biogeochemistry of Wetlands: Science and 

Applications, 774 p. (2008)). Wetlands with 

confined surface hydrologic connections to 

the stream are connected to jurisdictional 

tributary system and therefore can efficiently 

transport dissolved organic carbon and other 

dissolved organic matter to the nearby 

jurisdictional water and downstream (a)(1) 

through (a)(3) waters. See, e.g., I.F. Creed, et 

al., ‘‘Cryptic Wetlands: Integrating Hidden 

Wetlands in Regression Models of the Export 

of Dissolved Organic Carbon from Forested 

Landscapes,’’ Hydrological Processes 

17:3629–3648 (2003). Adjacent waters with a 

surface hydrologic connection to 

jurisdictional waters can also improve water 

quality through assimilation, transformation, 

or sequestration of nutrients and other 

pollutants. Report at 5–29 (citing, e.g., K.R. 

Reddy, and R.D. DeLaune, Biogeochemistry 

of Wetlands: Science and Applications, 774 

p. (2008)). These processes can occur during 

times of lower hydroperiods when water is 

not present in the surface hydrologic 

connection between the adjacent water and 

the jurisdictional water. Pollutants can be 

attenuated or retained in such adjacent 

waters through processes including 

denitrification, ammonia volatilization, 

microbial and plant biomass assimilation, 

sedimentation, sorption and precipitation 

reactions, biological uptake, and long-term 

storage in plant detritus. Id. at 5–29 (citing 

K.R. Reddy, et al., ‘‘Phosphorus Retention in 

Streams and Wetlands: A Review,’’ Critical 

Reviews in Environmental Science and 

Technology 29:83–146 (1999); K.R. Reddy 

and R.D. DeLaune, Biogeochemistry of 

Wetlands: Science and Applications, 774 p. 

(2008)). Through retention and mitigation of 

pollutants and other chemical compounds, 

adjacent waters with a surface hydrologic 

connection to jurisdictional waters can 

substantially improve water quality 

downstream. 

Wetlands and open waters with confined 

surface connections can affect the biological 

integrity of waters to which they connect. 

Movement of organisms between these 

adjacent waters and the nearby jurisdictional 

water is governed by many of the same 

factors that affect movement of organisms 

between riparian/floodplain waters and the 

river network. Id. at 5–31. Because such 

waters are at least periodically hydrologically 

connected to the nearby jurisdictional 

tributary network on the surface, dispersal of 

organisms can occur actively through the 

surface connection or via wind dispersal, 

hitchhiking, walking, crawling, or flying. See, 

e.g., id. at 5–31. For example, waterborne 

dispersal of aquatic and emergent plants can 

occur between the jurisdictional water and 

the neighboring water due to the periodic 

hydrologic connection to the tributary 

system. Id. at 5–31 (citing C. Nilsson, et al., 

‘‘The Role of Hydrochory in Structuring 

Riparian and Wetland Vegetation,’’ Biological 

Reviews 85:837–858 (2010)). Fish can also 

move between the jurisdictional water and 

the neighboring water to which it is 

connected via a surface hydrologic 

connection during periodic surficial 

hydrologic connections. Id. at 5–32 (citing 

J.W. Snodgrass, et al., ‘‘Factors affecting the 

occurrence and structure of fish assemblages 

in isolated wetlands of the upper coastal 

plain, USA,’’ Canadian Journal of Fisheries 

and Aquatic Sciences 53:443–454 (1996); 

K.D. Zimmer, et al., ‘‘Effects of fathead 

minnow colonization and removal on a 

prairie wetland ecosystem,’’ Ecosystems 

4:346–357 (2001); M.J. Baber, et al., ‘‘Controls 

on fish distribution and abundance in 

temporary wetlands,’’ Canadian Journal of 

Fisheries and Aquatic Sciences 59:1441–1450 

(2002); M.A. Hanson, et al., ‘‘Biotic 

interactions as determinants of ecosystem 

structure in prairie wetlands: An example 

using fish,’’ Wetlands 25:764–775 (2005);, 

B.R. Herwig, et al., ‘‘Factors influencing fish 

distributions in shallow lakes in prairie and 

prairie-parkland regions of Minnesota, USA,’’ 

Wetlands 30:609–619 (2010)). Mammals and 

aquatic and semi-aquatic amphibians and 

reptiles that can disperse overland can also 

contribute to connectivity, as can aquatic 

birds, particularly given the close proximity 

of the neighboring water to the jurisdictional 

water. Mammals and birds can act as 

transport vectors for hitchhikers like algae or 

aquatic insects. Id. at 5–32 (citing J.P. 

Roscher, ‘‘Alga Dispersal by Muskrat 

Intestinal Contents,’’ Transactions of the 

American Microscopical Society 86:497–498 

(1967)); J. Figuerola and A.J. Green, 

‘‘Dispersal of Aquatic Organisms by 

Waterbirds: a Review of Past Research and 

Priorities for Future Studies,’’ Freshwater 

Biology 47:483–494 (2002); J. Figuerola, et al., 

‘‘Invertebrate Eggs Can Fly: Evidence of 

Waterfowl-Mediated Gene Flow in Aquatic 

Invertebrates,’’ American Naturalist 165:274– 

280 (2005)). Amphibians and reptiles move 

between streams and their adjacent waters to 

satisfy part of their life-history requirements. 

Id.at 5–33, Table 5–2. The hydrologic 

connection between neighboring waters with 

a surface connection to the jurisdictional 

water allows for that movement to occur 

either in the water or over land. Aquatic 

insects that use both streams and their 

adjacent waters can move outside of the 

stream network to the nearby wetland or 

open water to seek suitable habitat for 

overwintering, refuge from adverse 

conditions, hunting, foraging or breeding, 

and then return to the stream for other lifehistory requirements. Id. at 5–33 (citing D.D. 

Williams, ‘‘Environmental Constraints in 

Temporary Fresh Waters and Their 

Consequences for the Insect Fauna,’’ Journal 

of the North American Benthological Society 

15:634–650 (1996); A.J. Bohonak and D.G. 

Jenkins, ‘‘Ecological and Evolutionary 

Significance of Dispersal by Freshwater 

Invertebrates,’’ Ecology Letters 6:783–796 

(2003)). Neighboring waters with a confined 

surface hydrologic connection to 

jurisdictional waters help to maintain various 

biological populations, which periodically 

replenish adjacent jurisdictional waters, 

serving to maintain the biological integrity of 

(a)(1) through (a)(3) waters. 

A shallow subsurface hydrologic 

connection is lateral water flow through a 

shallow subsurface layer, such as can be 

found in steeply sloping areas with shallow 

soils and soils with a restrictive horizon that 

prevents vertical water flow, or in karst 

systems. K.J. Devito, et al., ‘‘GroundwaterSurface Water Interactions in Headwater 

Forested Wetlands of the Canadian Shield,’’ 

Journal of Hydrology 181:127–47 (1996); 

M.A. O’Driscoll and R.R. Parizek, ‘‘The 

Hydrologic Catchment Area of a Chain of 

Karst Wetlands in Central Pennsylvania, 

USA,’’ Wetlands 23:171–79 (2003); B.J. Cook 

and F.R. Hauer, ‘‘Effects of Hydrologic 

Connectivity on Water Chemistry, Soils, and 

Vegetation Structure and Function in an 

Intermontane Depressional Wetland 

Landscape,’’ Wetlands 27:719–38 (2007). 

Shallow subsurface connections may be 

found below the ordinary root zone (below 

12 inches), where other wetland delineation 

factors may not be present. The presence of 

an aquiclude (impervious layer) near the 

surface leads to shallow subsurface flows 

through the soil, which favors local 

groundwater flowpaths that connect to 

nearby wetlands or streams. Report at 3–38. 

Wetlands with shallow subsurface 

connections can affect the physical integrity 

of waters to which they connect. In general, 

the volume and sustainability of streamflow 

within river networks depends on 

contributions from groundwater, especially 

in areas with shallow groundwater tables and 

pervious (meaning water can easily pass 

through) subsurfaces. Id. at 3–12 (citing J.J. 

de Vries, ‘‘Seasonal Expansion and 

Contraction of Stream Networks in Shallow 

Groundwater Systems,’’ Journal of Hydrology 

170:15–26 (1995); T.C. Winter, ‘‘The Role of 

Groundwater in Generating Streamflow in 

Headwater Areas and in Maintaining Base 

Flow,’’ Journal of the American Water 

Resources Association 43:15–25 (2007); G.R. 

Kish, et al., ‘‘A Geochemical Mass-Balance 

Method for Base-Flow Separation, Upper 

Hillsborough River Watershed, West-Central 

Florida, 2003–2005 and 2009,’’ USGS 

Scientific Investigations Report 2010–5092 

(Washington, DC: U.S. Department of the 

Interior, U.S. Geological Survey, 2010). 

Because wetlands with shallow subsurface 

connections to streams and rivers provide 

some of these groundwater contributions, 

they influence the flow regime. Wetlands 

connected via shallow subsurface 

connections also can act as water sinks when 

evapotranspiration is high, but as water 

sources when evapotranspiration is low. Id. 


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at 3–25. As a result, these adjacent waters 

moderate peak flows, reduce downstream 

flooding, and provide runoff to help maintain 

baseflow for streams during times of low 

flows. 

Wetlands and other waters with shallow 

subsurface connections affect the chemical 

and biological integrity of downstream 

waters in ways similar to wetlands with 

surface connections. The distance between 

these wetlands and jurisdictional waters may 

influence the connectivity since wetlands 

with shorter distances to the stream network 

will have higher hydrological and biological 

connectivity than wetlands located further 

from the same network. Id. at 3–43. The 

distance between the wetland and water may 

also influence whether waters are connected 

via surface or shallow subsurface hydrologic 

connections, as wetlands and open waters 

that are closer to rivers and streams will have 

a higher probability of being connected than 

more distant waters, assuming that 

conditions governing type and quantity of 

flows (e.g. slope, soil and aquifer 

permeability) are similar. Id at 5–2. For 

wetlands connected to tributaries through 

groundwater flows, less distant wetlands/ 

waters are generally connected through 

shallower flowpaths, assuming similar soil 

and geologic properties. Id. at 3–11 (Figure 

3–5), 3–42. These shallower subsurface flows 

have the greatest interchange with surface 

waters and travel between points in the 

shortest amount of time. Id. at 3–42. 

3. Adjacent Waters, Including Wetlands, 

Separated From Other ‘‘Waters of the United 

States’’ by Man-Made Dikes or Barriers, 

Natural River Berms, Beach Dunes and the 

Like Significantly Affect the Chemical, 

Physical, or Biological Integrity of (a)(1) 

Through (a)(3) Waters 

The terms earthen dam, dike, berm, and 

levee are used to describe similar structures 

whose primary purpose is to help control 

flood waters. Such structures vary in scale 

and size. A levee is an embankment whose 

primary purpose is to furnish flood 

protection from seasonal high water and 

which is therefore subject to water loading 

for periods of only a few days or weeks a 

year. Earthen embankments that are subject 

to water loading for prolonged periods 

(longer than normal flood protection 

requirements) are called earth dams. There 

are a wide variety of types of structures and 

an even wider set of construction methods. 

These range from a poorly constructed, low 

earthen berm pushed up by a backhoe to a 

well-constructed, impervious core, riprap 

lined levee that protects houses and 

cropland. Generally, levees are built to 

detach the floodplain from the channel, 

decreasing overbank flood events. S.B. 

Franklin, et al., ‘‘Complex Effects of 

Channelization and Levee Construction on 

Western Tennessee Floodplain Forest 

Function,’’ Wetlands 29(2): 451–464 (2009). 

The investigation methods to determine the 

presence or absence of the hydrologic 

connection depend on the type of structure, 

the underlying soils, the presence of 

groundwater, and the depth of the water 

table. Department of the Army, U.S. Army 

Corps of Engineers, Engineering and 

Design—Design and Construction of Levees, 

EM 1110–2–1913 (Washington, DC, 

Department of the Army, 2000), p. 1–1. 

Man-made berms and the like are fairly 

common along streams and rivers across the 

United States and often accompany stream 

channelization. S.B. Franklin, et al., 

‘‘Complex Effects of Channelization and 

Levee Construction on Western Tennessee 

Floodplain Forest Function,’’ Wetlands 29(2): 

451–464 (2009). One study conducted in 

Portland, Oregon found that 42% of surveyed 

wetlands had dams, dikes, or berms. M. 

Kentula, et al., ‘‘Tracking Changes in 

Wetlands with Urbanization: Sixteen Years of 

Experience in Portland, Oregon, USA,’’ 

Wetlands 24(4):734–743 (2004). Likewise, 

over 90% of the tidal freshwater wetlands of 

the Sacramento-San Joaquin Delta have been 

diked or leveed. C. Simenstad, et al., 

‘‘Preliminary Results from the SacramentoSan Joaquin Delta Breached Levee Wetland 

Study,’’ Interagency Ecological Program for 

the Sacramento-San Joaquin Estuary 

Newsletter 12(4):15–21 (1999). At least 

40,000 kilometers of levees, floodwalls, 

embankments, and dikes are estimated across 

the United States, with approximately 17,000 

kilometers of levees in the Upper Mississippi 

Valley alone. SE. Gergel, et al., 

‘‘Consequences of Human-altered Floods: 

Levees, Floods, and Floodplain Forests along 

the Wisconsin River,’’ Ecological 

Applications 12(6): 1755–1770 (2002). 

Adjacent waters separated from the 

tributary network by dikes, levees, berms and 

the like continue to have a hydrologic 

connection to downstream waters. This is 

because berms and similar features typically 

do not block all water flow. Indeed, even 

dams, which are specifically designed and 

constructed to impound large amounts of 

water effectively and safely, do not prevent 

all water flow, but rather allow seepage 

under the foundation of the dam and through 

the dam itself. See, e.g., International Atomic 

Energy Agency, Factsheet on Investigating 

Leaks through Dams and Reservoirs, http://

www.tc.iaea.org/tcweb/publications/

factsheets/sheet20dr.pdf; U.S. Bureau of 

Reclamation, Provo Office, Safety of Dams, 

http://www.usbr.gov/uc/provo/progact/

damsafety.html; Federal Energy Regulatory 

Commission (FERC), ‘‘Chapter 14: Dam 

Safety Performance Monitoring Program,’’ 

Engineering Guidelines for the Evaluation of 

Hydropower Projects (FERC, 2005), pp. 14– 

36 to 14–39. 

Seepage is the flow of a fluid through the 

soil pores. Seepage through a dam, through 

the embankments, foundations or abutments, 

or through a berm is a normal condition. D.A. 

Kovacic, et al., ‘‘Effectiveness of Constructed 

Wetlands in Reducing Nitrogen and 

Phosphorus Export from Agricultural Tile 

Drainage,’’ Journal of Environmental Quality 

29(4): 1262–1274 (2000); Federal Energy 

Regulatory Commission (FERC), ‘‘Chapter 14: 

Dam Safety Performance Monitoring 

Program,’’ Engineering Guidelines for the 

Evaluation of Hydropower Projects (FERC, 

2005), pp. 14–36 to 14–39. This is because 

water seeks paths of least resistance through 

the berm or dam and its foundation. 

Michigan Department of Environmental 

Quality, Seepage Through Earth Dams (2002), 

http://www.michigan.gov/deq/0,1607,7-135- 

3313_3684_3723-9515-,00.html. All earth and 

rock-fill dams are subject to seepage through 

the embankment, foundation, and abutments. 

Department of the Army, U.S. Army Corps of 

Engineers, Seepage Analysis and Control for 

Dams, EM 1110–2–1901, (Washington, DC: 

Department of the Army, Original 1986— 

Revised 1993), Page 1–1; Department of the 

Army, U.S. Army Corps of Engineers, 

Engineering and Design: General Design and 

Construction Considerations for Earth and 

Rock-filled Dams, EM 1110–2–2300 

(Washington, DC: Department of the Army, 

2004), pp. 6–1 to 6–7. Concrete gravity and 

arch dams similarly are subject to seepage 

through the foundation and abutments. 

Department of the Army, U.S. Army Corps of 

Engineers, Seepage Analysis and Control for 

Dams, EM 1110–2–1901 (Washington, DC: 

Department of the Army, Original 1986— 

Revised 1993), Page 1–1. Levees and the like 

are subject to breaches and breaks during 

times of floods. C. Nilsson, et al., 

‘‘Fragmentation and Flow Regulation of the 

World’s Large River Systems,’’ Science 

308(5720):405–408 (2005). Levees are 

similarly subject to failure in the case of 

extreme events, such as the extensive levee 

failures caused by Hurricanes Katrina and 

Rita. J.W. Day, et al., ‘‘Restoration of the 

Mississippi Delta: Lessons from Hurricanes 

Katrina and Rita,’’ Science 315(5819): 1679– 

1684 (2007). In designing levees and similar 

structures, seepage control is necessary to 

prevent possible failure caused by excessive 

uplift pressures, instability of the 

downstream slope, piping through the 

embankment and/or foundation, and erosion 

of material by migration into open joints in 

the foundation and abutments. Id.; D.A. 

Kovacic, et al., ‘‘Effectiveness of Constructed 

Wetlands in Reducing Nitrogen and 

Phosphorus Export from Agricultural Tile 

Drainage,’’ Journal of Environmental Quality 

29(4): 1262–1274 (2000); U.S. Department of 

the Interior, Bureau of Reclamation, Upper 

Colorado Region, see http://www.usbr.gov/

uc/provo/progact/damsafety.html; 

International Atomic Energy Agency, 

Investigating Leaks through Dams and 

Reservoirs, see http://www-tc.iaea.org/

tcweb/publications/factsheets/sheet20dr.pdf; 

California Division of Safety of Dams, 

Embankment Design, see http://

damsafety.water.ca.gov/guidelines/

embankment.htm. 

The rate at which water moves through the 

embankment depends on the type of soil in 

the embankment, how well it is compacted, 

the foundation and abutment preparation, 

and the number and size of cracks and voids 

within the embankment. All but the smallest 

earthen dams are commonly built with 

internal subsurface drains to intercept water 

seeping from the reservoir (i.e., upstream 

side) to the downstream side. Department of 

the Army, U.S. Army Corps of Engineers, 

Construction Control for Earth and Rockfilled Dams, EM 1110–2–1911, September 30, 

1995, Washington, DC 20314–1000, Page 1– 

1. Where it is not intercepted by a subsurface 

drain, the seepage will emerge downstream 

from or at the toe of the embankment. 

Michigan Department of Environmental 

Quality, Seepage Through Earth Dams (2002), 

http://www.michigan.gov/deq/0,1607,7-135- 


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22244 Federal Register / Vol. 79, No. 76 / Monday, April 21, 2014 / Proposed Rules 

3313_3684_3723-9515-,00.html. Seepage may 

vary in appearance from a ‘‘soft,’’ wet area to 

a flowing ‘‘spring.’’ It may show up first as 

an area where the vegetation is lush and 

darker green. Cattails, reeds, mosses, and 

other marsh vegetation may grow in a 

seepage area. Michigan Department of 

Environmental Quality, Seepage Through 

Earth Dams (2002), http://www.michigan.

gov/deq/0,1607,7-135-3313_3684_3723-9515- 

,00.html. 

Engineered berms are typically designed to 

interfere with the seasonal pattern of water 

level (hydroperiod) of the area behind the 

berm, reducing the frequency and severity of 

inundation. Berms are not designed to 

eliminate all hydrologic connection between 

the channel on one side and the area behind 

the berm on the other. It is almost always 

impracticable to build a berm that will not 

be overtopped by a flood of maximum 

severity, and most berms are not designed to 

withstand severe floods. See, e.g., 

Department of the Army, U.S. Army Corps of 

Engineers, Seepage Analysis and Control for 

Dams, EM 1110–2–1901, (Washington, DC: 

Department of the Army, Original 1986— 

Revised 1993), Page 1–1. Levees are designed 

to allow seepage and are frequently situated 

on foundations having natural covers of 

relatively fine-grain impervious to 

semipervious soils overlying pervious sands 

and gravels. Department of the Army, U.S. 

Army Corps of Engineers, Engineering and 

Design: Design Guidance for Levee 

Underseepage, ELT 1110–2–569, 

Washington, DC: Department of the Army, 

2005), pp. 1–9. These surface strata constitute 

impervious or semipervious blankets when 

considered in connection with seepage. 

Principal seepage control measures for 

foundation underseepage are (a) cutoff 

trenches, (b) riverside impervious blankets, 

(c) landslide berms, (d) pervious toe trenches, 

and (e) pressure relief wells. Department of 

the Army, U.S. Army Corps of Engineers, 

Engineering and Design—Design and 

Construction of Levees, EM 1110–2–1913 

(Washington, DC, Department of the Army, 

2000), p. 1–1. Overtopping of an 

embankment dam is very undesirable 

because the embankment materials may be 

eroded away. Additionally, only a small 

number of concrete dams have been designed 

to be overtopped. Water normally passes 

through the main spillway or outlet works; it 

should pass over an auxiliary spillway only 

during periods of high reservoir levels and 

high water inflow. All embankment and most 

concrete dams have some seepage. See, e.g., 

http://www.damsafety.org/layout/

subsection.aspx?groupid=14&contentid=47. 

However, it is important to control the 

seepage to prevent internal erosion and 

instability. Proper dam construction, and 

maintenance and monitoring of seepage 

provide control. 

Berm-like landforms known as natural 

levees occur naturally and do not isolate 

adjacent wetlands from the streams that form 

them. Natural levees and the wetlands and 

waters behind them are part of the 

floodplain, including along some small 

streams and streams in the Arid West. C.A. 

Johnston, et al., ‘‘Nutrient Dynamics in 

Relation to Geomorphology of Riverine 

Wetlands,’’ Soil Science Society of America 

Journal 65(2):557–577 (2001). Every flowing 

watercourse transports not only water, but 

sediment—eroding and rebuilding its banks 

and floodplains continually. Federal 

Interagency Stream Restoration Working 

Group, Stream Corridor Restoration: 

Principles, Processes and Practices, USDA 

National Engineering Handbook Part 653 

(1999). Different deposition patterns occur 

under varying levels of streamflow, with 

higher flows having the most influence on 

the resulting shape of streambanks and 

floodplains. Id. In relatively flat landscapes 

drained by low-gradient streams, this natural 

process deposits the most sediment on the 

bank immediately next to the stream channel 

while floodplains farther from the channel 

are usually lower-lying wetlands 

(‘‘backswamps’’ or ‘‘backwater wetlands’’) 

that receive less sediment. See, e.g., C.A. 

Johnston, et al., ‘‘The Potential Role of 

Riverine Wetlands as Buffer Zones,’’ in N.E. 

Haycock, et al., ed., Buffer Zones Their 

Processes and Potential in Water Protection 

(Quest International, 1997), pp. 155–170. The 

somewhat elevated land thus built up at 

streamside is called a natural levee, and this 

entirely natural landform is physically and 

hydrologically similar to narrow, man-made 

berms. See, e.g., L.B. Leopold, et al., Fluvial 

Processes in Geomorphology (Toronto: 

General Publishing Co. Ltd., 1964). Natural 

levees are discontinuous, which allows for a 

hydrologic connection to the stream or river 

via openings in the levees and thus the 

periodic mixing of river water and backwater. 

C.A. Johnston, et al., ‘‘Nutrient Dynamics in 

Relation to Geomorphology of Riverine 

Wetlands,’’ Soil Science Society of America 

Journal 65(2): 557–577 (2001). In addition, 

streams with natural levees, in settings with 

no human interference whatsoever, retain 

hydrologic connection with their wetlands 

behind the levees by periodic flooding during 

high water and via seepage through and 

under the levee. Similarly, man-made berms 

are typically periodically overtopped with 

water from the near-by stream, and as 

previously mentioned, are connected via 

seepage. 

Waters, including wetlands, separated from 

a stream by a natural or man-made berm 

serve many of the same functions as those 

discussed above on other adjacent waters. 

Furthermore, even in cases where a 

hydrologic connection may not exist, there 

are other important considerations, such as 

chemical and biological factors, that result in 

a significant nexus between the adjacent 

wetlands or waters and the nearby ‘‘waters of 

the United States,’’ and (a)(1) through (a)(3) 

waters. 

The movement of surface and subsurface 

both over berms and through soils and berms 

adjacent to rivers and streams is a hydrologic 

connection between wetlands and flowing 

watercourses. The intermittent connection of 

surface waters over top of, or around, natural 

and manmade berms further strengthens the 

evidence of hydrologic connection between 

wetlands and flowing watercourses. Both 

natural and man-made barriers can be topped 

by occasional floods or storm events. See, 

e.g., R.E. Turner, et al., ‘‘Wetland 

Sedimentation from Hurricanes Katrina and 

Rita,’’ Science 314(5798): 449–452 (2006); 

P.A. Keddy, et al., ‘‘The Wetlands of Lakes 

Pontchartrain and Maurepas: Past, Present 

and Future,’’ Environmental Reviews 15: 43– 

77 (2007). When berms are periodically 

overtopped by water, wetlands and waters 

behind the barriers are directly connected to 

and interacting with the nearby stream and 

its downstream waters. In addition, surface 

waters move to and from adjacent soils 

(including adjacent wetland soils) 

continually. Along their entire length, 

streams alternate between effluent (watergaining) and influent (water-losing) zones as 

the direction of water exchange with the 

streambed and banks varies. Federal 

Interagency Stream Restoration Working 

Group, Stream Corridor Restoration: 

Principles, Processes and Practices, USDA 

National Engineering Handbook Part 653 

(1999). The adjacent areas involved in this 

surface water exchange with a stream or river 

are known as the hyporheic zone. Hyporheic 

zone waters are part of total surface waters 

temporarily moving through soil or sediment. 

Like within-channel waters, these waters are 

oxygenated and support living communities 

of organisms in the hyporheic zone. 

Because a hydrologic connection between 

adjacent wetlands and waters and 

downstream waters still exists despite the 

presence of a berm or the like, the chemical 

and biological connections that rely on a 

hydrologic connection also exist. For 

instance, adjacent waters behind berms can 

still serve important water quality functions, 

serving to filter pollutants and sediment 

before they reach downstream waters. 

Wetlands behind berms can function to filter 

pollutants before they enter the nearby 

tributary, with the water slowly released to 

the stream through seepage or other 

hydrological connections. See, e.g., L.L. 

Osborne and D.A. Kovacic, ‘‘Riparian 

Vegetated Buffer Strips in Water-Quality 

Restoration and Stream Management,’’ 

Freshwater Biology 29(2): 243–258 (1993); 

D.A. Kovacic, et al., ‘‘Effectiveness of 

Constructed Wetlands in Reducing Nitrogen 

and Phosphorus Export from Agricultural 

Tile Drainage,’’ Journal of Environmental 

Quality 29(4): 1262–1274 (2000). Their 

ability to retain sediment and floodwaters 

may be enhanced by the presence of the 

berm. For instance, some backwater wetlands 

in floodplain/riparian areas exhibit higher 

sedimentation rates than streamside 

locations. E.J. Kuenzler, et al., ‘‘Distributions 

and Budgets of Carbon, Phosphorus, Iron and 

Manganese in a Floodplain Swamp 

Ecosystem,’’ Water Resources Research 

Institute Report 157 (Chapel Hill, NC: 

University of North Carolina, 1980); C.A. 

Johnston, et al., ‘‘Nutrient Dynamics in 

Relation to Geomorphology of Riverine 

Wetlands,’’ Soil Science Society of America 

Journal 65(2): 557–577 (2001). The presence 

of manmade levees can actually increase 

denitrification rates, meaning that the 

adjacent waters can more quickly transform 

nitrogen. SE. Gergel, et al., ‘‘Do Dams and 

Levees Impact Nitrogen Cycling? Simulating 

the Effects of Flood Alterations on 

Floodplain Denitrification,’’ Global Change 

Biology 11(8): 1352–1367 (2005). However, 

the presence of manmade berms does limit 


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the ability of the river to connect with its 

adjacent wetlands through overbank flooding 

and thus limits sediment, water and nutrients 

transported from the river to the adjacent 

waters. Id.; J.L. Florsheim and J.F. Mount, 

‘‘Changes in Lowland Floodplain 

Sedimentation Processes: Pre-disturbance to 

Post-rehabilitation, Cosumnes River, CA,’’ 

Geomorphology 56(3–4):305–323 (2003). 

However, the presence of a berm does not 

completely eliminate the transport of 

sediments and water from the river to the 

nearby adjacent wetland, as suspended 

sediments and water can overflow both 

natural and man-made levees, though the 

transport is usually more pronounced in 

settings with natural levees. See, e.g., R.E. 

Turner, et al., ‘‘Wetland Sedimentation from 

Hurricanes Katrina and Rita,’’ Science 

314(5798):449–452 (2006); P.A. Keddy, et al., 

‘‘The Wetlands of Lakes Pontchartrain and 

Maurepas: Past, Present and Future,’’ 

Environmental Reviews 15:43–77 (2007). 

Sediment deposition over levees is 

particularly enhanced by extreme events like 

hurricanes. Id.; D.J. Reed, et al., ‘‘Reducing 

the Effects of Dredged Material Levees on 

Coastal Marsh Function: Sediment 

Deposition and Nekton Utilization,’’ 

Environmental Management 37(5):671–685 

(2006). Wetlands behind berms, where the 

system is extensive, can help reduce the 

impacts of storm surges caused by 

hurricanes. J.W. Day, et al., ‘‘Restoration of 

the Mississippi Delta: Lessons from 

Hurricanes Katrina and Rita,’’ Science 

315(5819):1679–1684 (2007). 

Adjacent waters, including wetlands, 

separated from water bodies by berms and 

the like maintain ecological connection with 

those water bodies. Though a berm may 

reduce habitat functional value and may 

prevent some species from moving back and 

forth from the wetland to the river, many 

major species that prefer habitats at the 

interface of wetland and stream ecosystems 

remain able to utilize both habitats despite 

the presence of such a berm. Additional 

species that are physically isolated in either 

stream or wetlands habitat still interact 

ecologically with species from the other 

component. Thus, adjacent wetlands with or 

without small berms can retain numerous 

similarities in ecological function. For 

example: Wetland bird species such as 

wading birds are able to utilize both wetland 

and adjacent stream/ditch habitats; wetland 

amphibians would be able to bypass the berm 

in their adult stage; aquatic invertebrates and 

fish would still interact with terrestrial/

wetland predators and prey in common food 

web relationships despite the presence of a 

berm. See, e.g., G.S. Butcher, and B. Zimpel, 

‘‘Habitat Value of Isolated Waters to 

Migratory Birds,’’ Prepared by Cornell 

Laboratory of Ornithology and The Cadmus 

Group, Inc. for U.S. Environmental 

Protection Agency Office of Wetlands 

Protection, (Washington, DC: Cornell and 

Cadmus, 1991); M.F. Willson and K.C. 

Halupka, ‘‘Anadromous Fish as Keystone 

Species in Vertebrate Communities,’’ 

Conservation Biology 9(3):489–497 (1995); 

C.J. Cederholm, et al., ‘‘Pacific Salmon 

Carcasses: Essential Contributions of 

Nutrients and Energy for Aquatic and 

Terrestrial Ecosystems,’’ Fisheries 24(10):6– 

15 (1999); S.S. Schwartz and D.G. Jenkins, 

‘‘Temporary Aquatic Habitats: Constraints 

and Opportunities,’’ Aquatic Ecology 34:3–8 

(2000); D.T. Bilton, et al., ‘‘Dispersal in 

Freshwater Invertebrates,’’ Annual Review of 

Ecology and Systematics 32:159–81 (2001). 

One example of adjacent waters behind 

berms and the like are interdunal wetlands 

located in coastal areas, including some areas 

of the Great Lakes and along barrier islands. 

Interdunal wetlands form in swales or 

depressions within open dunes or between 

beach ridges along the coast and experience 

a fluctuating water table seasonally and 

yearly in synchrony with sea or lake level 

changes. W.E. Odum, ‘‘Non-Tidal Freshwater 

Wetlands in Virginia,’’ Virginia Journal of 

Natural Resources Law 7: 421–434 (1988); 

D.A. Albert, Borne of the Wind: An 

Introduction to the Ecology of Michigan Sand 

Dunes (Lansing, MI: Michigan Natural 

Features Inventory, 2000), 63 pp.; D.A. 

Albert, Between Land and Lake: Michigan’s 

Great Lakes Coastal Wetlands, Bulletin E– 

2902 (East Lansing, MI: Michigan Natural 

Features Inventory, Michigan State 

University Extension, 2003), 96 pp; D.A. 

Albert, Natural Community Abstract for 

Interdunal Wetland (Lansing, MI: Michigan 

Natural Features Inventory, 2007), 6 pp. For 

those along the ocean coast, they are 

typically formed as a result of oceanic 

processes where the wetlands establish 

behind relict dune ridges (dunes that were 

formed along a previously existing coast 

line). Wetlands in the interdunal system are 

in close proximity to each other and to the 

surrounding (a)(1) through (a)(3) waters. 

Their proximity to one another and to the 

(a)(1) through (a)(3) waters indicates a close 

physical relationship between interdunal 

wetland systems and the traditional 

navigable waters, interstate waters, or the 

territorial seas. Despite the presence of the 

beach dunes, interdunal wetlands have 

chemical, physical, or biological connections 

that greatly influence the integrity of the 

nearby (a)(1) through (a)(3) waters. The 

wetlands are hydrologically connected to 

these (a)(1) through (a)(3) waters through 

unconfined, directional flow and shallow 

subsurface flow during normal precipitation 

events and extreme events. As previously 

noted, they are linked to the rise and fall of 

the surrounding tides—the water-level 

fluctuations of the nearby (a)(1) through (a)(3) 

waters are important for the dynamics of the 

wetlands. D.A. Albert, Between Land and 

Lake: Michigan’s Great Lakes Coastal 

Wetlands, Bulletin E–2902 (East Lansing, MI: 

Michigan Natural Features Inventory, 

Michigan State University Extension, 2003), 

96 pp. The wetlands provide floodwater 

storage and attenuation, retaining and slowly 

releasing floodwaters before they reach the 

nearby (a)(1) through (a)(3) waters. Like other 

adjacent wetlands, interdunal wetlands also 

have important chemical connections to the 

nearby (a)(1) through (a)(3) waters, as they 

serve important water quality benefits. The 

wetlands store sediment and pollutants that 

would otherwise reach the surrounding (a)(1) 

through (a)(3) waters. The wetlands are 

biologically connected to the surrounding 

(a)(1) through (a)(3) waters. For instance, they 

provide critical habitats for species that 

utilize both the wetlands and the nearby 

(a)(1) through (a)(3) waters, supporting high 

diversity and structure. Habitat uses include 

basic food, shelter, and reproductive 

requirements. Aquatic insects, amphibians, 

and resident and migratory birds all use 

interdunal wetlands as critical habitat, and 

the wetlands provide better shelter than the 

nearby exposed beach. D.A. Albert, Borne of 

the Wind: An Introduction to the Ecology of 

Michigan Sand Dunes (Lansing, MI: 

Michigan Natural Features Inventory, 2000), 

63 pp.; S.M. Smith, et al., ‘‘Development of 

Vegetation in Dune Slack Wetlands of Cape 

Cod National Seashore (Massachusetts, 

USA),’’ Plant Ecology 194(2): 243–256 (2008). 

In marine coastal areas, the wetlands are 

often the only freshwater system in the 

immediate landscape, thus providing critical 

drinking water for the species that utilize 

both the wetlands and the nearby (a)(1) 

through (a)(3) waters, although some 

interdunal wetlands are brackish in nature. 

See, e.g., C.M. Heckscher and C.R. Bartlett, 

‘‘Rediscovery and Habitat Associations of 

Photuris Bethaniensis McDermott 

(Coleoptera: Lampyridae),’’ The Coleopterists 

Bulletin 58(3): 349–353 (2004). 

Wetlands behind the extensive levee 

system in the Yazoo Basin are an example of 

adjacent waters behind man-made barriers. A 

regional hydrogeomorphic approach 

guidebook for the Yazoo Basin of the Lower 

Mississippi River Alluvial Valley assesses the 

functions of these wetlands. R.D. Smith and 

C.V. Klimas, A Regional Guidebook for 

Applying the Hydrogeomorphic Approach to 

Assessing Wetland Functions of Selected 

Regional Wetland Subclasses, Yazoo Basin, 

Lower Mississippi River Alluvial Valle, 

Prepared for the U.S. Army Corps of 

Engineers, ERDC/EL TR–02–4 (2002). An 

extensive levee system was built along the 

river system to prevent flooding of the 

Mississippi River, resulting in drastic effects 

to the hydrology of the basin. Id. at 47. 

Despite the alteration of hydrology in the 

basin, extensive wetlands systems still exist 

behind the man-made and natural levees and 

maintain a hydrologic connection to the river 

system. These wetlands detain floodwater, 

detain precipitation, cycle nutrients, export 

organic carbon, remove elements and 

compounds, maintain plant communities, 

and provide fish and wildlife habitat. Id. The 

functions in turn provide numerous and 

substantial benefits to the nearby river. 

4. Conclusions Regarding Adjacent Waters 

The scientific literature documents that 

waters which are adjacent to (a)(1) through 

(a)(5) waters, including wetlands, oxbow 

lakes and adjacent ponds, are integral parts 

of tributary networks to (a)(1) through (a)(3) 

waters because they are directly connected to 

streams via permanent surface features that 

concentrate, mix, transform, and transport 

water and other materials, including food 

resources, downstream to larger rivers. 

Adjacent wetlands and other adjacent waters 

filter pollutants before they enter the 

tributary system, they attenuate flow during 

flood events, they regulate flow rate and 

timing, they trap sediment, and they input 

organic material into rivers and streams, 

providing the basic building blocks for their 


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healthy functioning. These waters also are 

biologically connected to downstream waters 

by providing habitat and refuge to many 

species, and storing and releasing food 

sources. The scientific literature 

demonstrates that adjacent waters in a 

watershed together exert a strong influence 

on the character and functioning of rivers, 

streams and lakes. 

Adjacent waters, as defined, alone or in 

combination with other adjacent waters in a 

watershed, significantly affect the chemical, 

physical, or biological integrity of traditional 

navigable waters, interstate waters, and the 

territorial seas. Based on studies of waters in 

riparian areas, flood plains, and their 

hydrologic connections through the tributary 

system there is sufficient scientific evidence 

regarding the important functions of these 

adjacent wetlands to demonstrate that, alone 

or in combination with similarly situated 

waters in the region, wetlands and open 

waters adjacent to any tributary have a 

significant effect on the chemical, physical, 

or biological integrity of traditional navigable 

waters, interstate waters, or the territorial 

seas. The reviewed scientific literature 

supports the conclusion that adjacent waters 

generally play a larger role in the ecological 

condition of smaller tributary systems, 

which, in turn, determines the effects on the 

chemical, physical, and biological health of 

larger downstream waters. 

iii. ‘‘Other Waters’’ 

The Report includes a focused evaluation 

of the connections and effects to downstream 

waters for several regional types of streams 

and wetlands: Prairie streams, southwest 

intermittent and ephemeral streams, oxbow 

lakes, Carolina and Delmarva bays, prairie 

potholes, and vernal pools. These regional 

types were chosen for evaluation because 

they represent a broad geographic area as 

well as a diversity of water types based on 

their origin, landscape setting, hydrology, 

and other factors. Most prairie streams and 

southwest intermittent and ephemeral 

streams are likely to be considered tributaries 

to (a)(1) through (a)(3) waters (with the 

exception of streams, for example, located in 

closed basins, which lack an (a)(1) through 

(a)(3) water or a connection thereto); 

similarly, most oxbow lakes are likely to be 

considered adjacent to (a)(1) through (a)(5) 

waters. Carolina and Delmarva bays, prairie 

potholes, and vernal pools may or may not 

be considered adjacent to (a)(1) through (a)(5) 

waters. Where waters are not considered 

tributaries (e.g. waters in a solely intrastate 

closed basin that does not contain a 

traditional navigable water, interstate water, 

or a territorial sea, or a connection thereto) 

or where waters, including wetlands, do not 

meet the proposed regulatory definition of 

adjacent, they should be evaluated to 

determine whether they are (a)(7) waters. The 

agencies seek comment on establishing such 

categories, as well as on other options for 

addressing ‘‘other waters.’’ 

The term ‘‘other waters’’ refers to waters 

that cannot be considered ‘‘adjacent’’ to 

downstream jurisdictional waters and that 

are not tributaries of such waters. ‘‘Other 

waters’’ are found outside the riparian zone 

and the floodplain, as waters within these 

areas are considered to be ‘‘adjacent.’’ As 

such, wetlands that are ‘‘other waters’’ 

typically will have unidirectional flow. As 

mentioned in Part II, section 2.B. above, 

many unidirectional wetlands are considered 

adjacent and interact with downstream 

jurisdictional waters through channels, 

shallow subsurface flow, or by providing 

additional functions such as storage and 

mitigating peak flows. Unidirectional 

wetlands that lack a confined surface 

connection or a shallow subsurface 

connection to downstream waters and are 

surrounded by uplands will typically fall 

under the definition of ‘‘other waters,’’ and 

are often referred to in scientific literature 

and policy as ‘‘geographically isolated 

waters.’’ The term ‘‘geographically isolated’’ 

should not be used to implicate the lack of 

connectivity to downstream waters, as these 

wetlands are often connected to downstream 

waters through deeper groundwater 

connections, biological connections, or 

spillage. The degree of connectivity of such 

wetlands will vary depending on landscape 

features such as distance from downstream 

waters and proximity to other wetlands of 

similar nature that as a group connect to 

jurisdictional downstream waters. Report at 

3–43, 5–2. 

For purposes of assessing whether a 

particular water is a ‘‘water of the United 

States’’ because it, alone or in combination 

with other similarly situated waters, has a 

significant nexus to an (a)(1) through (a)(3) 

water, the agencies are proposing to define 

each of the elements of Justice Kennedy’s 

significant nexus standard in the definition 

of ‘‘significant nexus.’’ 

A. In the Region 

The agencies have determined that because 

the movement of water from watershed 

drainage basins to river networks and lakes 

shapes the development and function of 

these systems in a way that is critical to their 

long term health, the watershed is a 

reasonable and technically appropriate 

interpretation of Justice Kennedy’s standard. 

See, e.g., D.R. Montgomery, ‘‘Process 

Domains and the River Continuum,’’ Journal 

of the American Water Resources Association 

35:397–410 (1999). 

Using a watershed as the framework for 

conducting significant nexus evaluations is 

scientifically supportable. Watersheds are 

generally regarded as the most appropriate 

spatial unit for water resource management. 

See, e.g., J.M. Omernik and R.G. Bailey, 

‘‘Distinguishing Between Watersheds and 

Ecoregions,’’ Journal of the American Water 

Resources Association 33.5: 939–40 (1997); 

D.R. Montgomery, ‘‘Process Domains and the 

River Continuum,’’ Journal of the American 

Water Resources Association 35: 397–410 

(1999); T.C. Winter ‘‘The Concept of 

Hydrologic Landscapes,’’ Journal of the 

American Water Resources Association 37: 

335–49 (2001); J.S. Baron, et al., ‘‘Meeting 

Ecological and Societal Needs for 

Freshwater,’’ Ecological Applications 12: 

1247–60 (2002); J.D. Allan, ‘‘Landscapes and 

Riverscapes: The Influence of Land Use on 

Stream Ecosystems,’’ Annual Review of 

Ecology Evolution and Systematics 35: 257– 

84 (2004); United States, EPA 841–B–08–002: 

U.S. Environmental Protection Agency, 

Handbook for Developing Watershed Plans to 

Restore and Protect Our Waters: Planning & 

Implementation Steps (Washington D.C.: U.S. 

EPA, March 2008); P.J. Wigington, et al., 

‘‘Oregon Hydrologic Landscapes: A 

Classification Framework,’’ Journal of the 

American Water Resources Association 

49.1:163–82 (2013). Anthropogenic actions 

and natural events can have widespread 

effects within the watershed that collectively 

impact the quality of the relevant traditional 

navigable water, interstate water or territorial 

sea. United States, U.S. EPA and USDA/ARS 

Southwest Watershed Research Center, EPA/ 

600/R–08/134, ARS/2330462008: The 

Ecological and Hydrological Significance of 

Ephemeral and Intermittent Streams in the 

Arid and Semi-arid American Southwest 

(Washington, D.C.: U.S. EPA and USDA/ARS 

Southwest Watershed Research Center, 

Levick et al., 2008) (Levick, et. al.). For these 

reasons, it is more appropriate to conduct a 

significant nexus determination at the 

watershed scale than to focus on a specific 

site, such as an individual stream segment. 

The watershed size reflects the specific water 

management objective, and is scaled up or 

down as is appropriate to meet that objective. 

If the objective is to manage the water quality 

in a particular receiving water body (the 

‘‘target’’ water body), the watershed should 

include all those waters that are contributing 

to that target water since they will primarily 

determine the quality of the receiving water. 

The watershed that drains to the single 

point of entry to a traditional navigable 

water, interstate water or territorial sea is a 

logical spatial framework for the evaluation 

of the nexus. This is because, from a water 

quality management perspective, the (a)(1), 

(a)(2) or (a)(3) water is the downstream 

affected water whose quality is dependent on 

the condition of the contributing upstream 

waters, including streams, lakes, and 

wetlands. To restore or maintain the health 

of the downstream affected water, it is 

standard practice to evaluate the condition of 

the waters that are in the contributing 

watersheds and to develop a plan to address 

the issues of concern. The functions of the 

contributing waters are inextricably linked 

and have a cumulative effect on the integrity 

of the downstream traditional navigable 

water, interstate water or territorial sea. The 

size of that watershed can be determined by 

identifying the geographic area that drains to 

the nearest traditional navigable water, 

interstate water or the territorial seas, and 

then using that point of entry watershed to 

conduct a significant nexus evaluation. P.E. 

Black, ‘‘Watershed Functions,’’ Journal of the 

American Water Resources Association 

33.1:1–11 (1997). 

The Corps is organized based on 

watersheds and has used watershed 

framework approaches for water sources, 

navigation approaches for over 100 years, 

and in the regulatory program since its 

inception. Also, using a watershed 

framework is consistent with over two 

decades of practice by EPA and many other 

governmental, academic, and other entities 

which recognize that a watershed approach 

is the most effective framework to address 

water resource challenges. U.S. 

Environmental Protection Agency, The 


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Watershed Protection Approach Framework 

(Oct. 1991). The agencies both recognize the 

importance of the watershed approach by 

investing in opportunities to advance 

watershed protection and in developing 

useful watershed tools and services. For 

example, EPA is allowing states that are 

reorganizing programs to function on a 

watershed basis to have short-term backlogs 

on CWA section 402 National Pollution 

Discharge Elimination System (NPDES) 

permit review—without penalty. This 

flexibility gives states time to synchronize 

the reissuance of major and minor permits 

within a watershed. By managing NPDES 

permits on a watershed basis, all the permits 

for discharges to the water body can be 

coordinated and the most efficient and 

equitable allocation of pollution control 

responsibility can be made. U.S. 

Environmental Protection Agency, Why 

Watersheds?, EPA 800–F–96–001 (February 

1996). Applying a watershed approach 

continues to be a priority of EPA, and is one 

of the three key strategies the agency is using 

to drive progress toward the Agency’s health 

and environmental goals over the next five 

years. U.S Environmental Protection Agency, 

FY 2011–2015 Strategic Plan: Achieving Our 

Vision, 2010. 

B. Similarly Situated 

Scientists routinely aggregate the effects of 

groups of waters, multiplying the known 

effect of one water by the number of similar 

waters in a specific geographic area, or to a 

certain scale. This kind of functional 

aggregation of non-adjacent (and other types 

of waters) is well-supported in the scientific 

literature. See, e.g., R.J. Stevenson and F.R. 

Hauer, ‘‘Integrating Hydrogeomorphic and 

Index of Biotic Integrity Approaches for 

Environmental Assessment of Wetlands,’’ 

Journal of the North American Benthological 

Society 21(3): 502–513 (2002); S.G. 

Leibowitz, ‘‘Isolated Wetlands and Their 

Functions: An Ecological Perspective,’’ 

Wetlands 23:517–531 (2003); D. Gamble, et 

al., An Ecological and Functional 

Assessment of Urban Wetlands in Central 

Ohio, Ohio EPA Technical Report WET/ 

2007–3B (Columbus, OH: Ohio 

Environmental Protection Agency, 2007); 

C.R. Lane and E. D’Amico, ‘‘Calculating the 

Ecosystem Service of Water Storage in 

Isolated Wetlands using LiDAR in North 

Central Florida, USA,’’ Wetlands 30:967–977 

(2010); B.P. Wilcox, et al., ‘‘Evidence of 

Surface Connectivity for Texas Gulf Coast 

Depressional Wetlands,’’ Wetlands 

31(3):451–8 (2011). Similarly, streams and 

rivers are routinely aggregated by scientists to 

estimate their combined effect on 

downstream waters in the same watershed. 

This is because chemical, physical, or 

biological integrity of downstream waters is 

directly related to the aggregate contribution 

of upstream waters that flow into them, 

including any tributaries and connected 

wetlands. As a result, the scientific literature 

and the Report consistently documents that 

the health of larger downstream waters is 

directly related to the aggregate health of 

waters located upstream, including waters 

such as wetlands that may not be 

hydrologically connected but function 

together to prevent floodwaters and 

contaminants from reaching downstream 

waters. 

In the aggregate, similarly situated 

wetlands may have significant effects on the 

quality of water many miles away, 

particularly in circumstances where 

numerous similarly situated waters are 

located in the region and are performing like 

functions that combine to influence 

downstream waters. See, e.g., A. Jansson et 

al., ‘‘Quantifying the Nitrogen Retention 

Capacity of Natural Wetlands in the LargeScale Drainage Basin of the Baltic Sea,’’ 

Landscape Ecology 13:249–262 (1998); W.J. 

Mitsch et al., ‘‘Reducing Nitrogen Loading to 

the Gulf of Mexico from the Mississippi River 

Basin: Strategies to Counter a Persistent 

Ecological Problem,’’ BioScience 51(5): 373– 

388 (2001); M.G. Forbes, et al., ‘‘Nutrient 

Transformation and Retention by Coastal 

Prairie Wetlands, Upper Gulf Coast, Texas,’’ 

Wetlands 32(4):705–15 (2012). Cumulatively, 

many small wetlands can hold a large 

amount of snowmelt and precipitation, 

reducing the likelihood of flooding 

downstream. Report at 5–25 (citing D.E. 

Hubbard and R.L. Linder, ‘‘Spring Runoff 

Retention in Prairie Pothole Wetlands,’’ 

Journal of Soil and Water Conservation 

41(2):122–125 (1986)). 

Scientists can and do routinely classify 

similar waters and wetlands into groups for 

a number of different reasons; because of 

their inherent physical characteristics, 

because they provide similar functions, 

because they were formed by similar 

geomorphic processes, and by their level of 

biological diversity, for example. Classifying 

wetlands based on their functions is also the 

basis for the U.S. Army Corps of Engineers 

hydrogeomorphic (HGM) classification of 

wetlands. M.M. Brinson, A Hydrogeomorphic 

Classification for Wetlands (Washington, 

D.C.: U.S. Army Corps of Engineers, 1993). 

The HGM method is a wetlands assessment 

approach pioneered by the Corps in the 

1990s, and extensively applied via regional 

handbooks since then. The Corps HGM 

method uses a conceptual framework for 

identifying broad wetland classes based on 

common structural and functional features, 

which includes a method for using local 

attributes to further subdivide the broad 

classes into regional subclasses. Assessment 

methods like the HGM provide a basis for 

determining if waters provide similar 

functions based on their structural attributes 

and indicator species. Scientists also directly 

measure attributes and processes taking place 

in particular types of waters during in-depth 

field studies that provide reference 

information that informs the understanding 

of the functions performed by many types of 

aquatic systems nationwide. 

These waters, primarily depressional 

wetlands, small open waters and peatlands, 

are known to have important hydrologic, 

water quality, and habitat functions which 

vary as a result of the diverse settings in 

which they exist across the country. For 

example, a report that reviewed the results of 

multiple scientific studies concluded that 

depressional wetlands lacking a surface 

outlet functioned together to significantly 

reduce or attenuate flooding. Report at 5–26 

(citing A. Bullock and M. Acreman, ‘‘The 

Role of Wetlands in the Hydrological Cycle,’’ 

Hydrology and Earth System Sciences 7:358– 

389 (2003)). Some of the important factors 

which influence the variability of their 

functions and connectivity include the 

topography, geology, soil features, antecedent 

moisture conditions, and seasonal position of 

the water table relative to the wetland. Report 

at 5–25. 

When proposing that ‘‘other waters’’ are 

sufficiently close and should be considered 

similarly situated, it is recognized that they 

are more likely to have similar influence with 

regard to their effect on the chemical, 

physical, or biological integrity of a 

downstream water identified in paragraphs 

(a)(1) through (a)(3). If a water is a great 

distance from a group of similar ‘‘other 

waters,’’ it may be performing some of the 

same functions as those in the group, but 

their distance from each other or from 

downstream (a)(1) through (a)(3) waters will 

decrease the probability that it has some kind 

of chemical, physical, or biological 

connectivity to the downstream water, 

assuming that conditions governing the type 

and quantity of flows (e.g. slope, soil, and 

aquifer permeability, etc.) are similar. Id. at 

5–2, 5–41. 

Consideration of the aggregate effects of 

wetlands and other waters often gives the 

most complete information about how such 

waters influence the chemical, physical, or 

biological integrity of downstream waters. In 

many watersheds, wetlands have a 

disproportionate effect on water quality 

relative to their surface area because wetland 

plants slow down water flow, allowing 

suspended sediments, nutrients, and 

pollutants to settle out. They filter these 

materials out of the water received from large 

areas, absorbing or processing them, and then 

releasing higher quality water. National 

Research Council, Wetlands: Characteristics 

and Boundaries (Washington, D.C.: National 

Academy Press, 1995), p. 38. For an 

individual wetland, this is most pronounced 

where it lies immediately upstream of a 

drinking water intake, for example. See, e.g., 

C.A. Johnston, et al., ‘‘The Cumulative Effect 

of Wetlands on Stream Water Quality and 

Quantity,’’ Biogeochemistry 10:105–141 

(1990). 

The structure and function of a river are 

highly dependent on the constituent 

materials that are stored in, or transported 

through the river. Most of the materials found 

in rivers originate outside of them. Thus, the 

fundamental way that ‘‘other waters’’ are able 

to affect river structure and function is by 

providing or altering the materials delivered 

to the river. Report at 1–13. Since the 

alteration of material fluxes depends on the 

functions within these waters and the degree 

of connectivity, it is appropriate to consider 

both these factors for purposes of significant 

nexus under this provision. 

Numerous factors affect chemical, 

physical, and biological connectivity, 

operating at multiple spatial and temporal 

scales, and interacting with each other in 

complex ways, to determine where 

components of aquatic systems fall on the 

connectivity-isolation gradient at a given 

time. Some of these factors include climate, 

watershed characteristics, spatial distribution 


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patterns, biota, and human activities and 

alterations. Id. at 3–33. Recognizing the 

limits on the ability to observe or document 

all of these interacting factors, it is reasonable 

to look for visible patterns in the landscape 

and waters that are often indicative of the 

connectivity factors, in determining what 

waters to aggregate. Due to relative similarity 

of soils, topography, or groundwater 

connections, for example, there may be a 

group of wetlands scattered throughout a 

watershed, at similar distances from the 

tributaries in the watershed and performing 

similar functions. It is appropriate to assess 

the significance of the nexus of those waters 

in the aggregate, consistent with Justice 

Kennedy’s standard. 

C. Significant Nexus 

The scientific literature regarding ‘‘other 

waters’’ documents their functions, including 

the chemical, physical, and biological impact 

they can have downstream. Available 

literature indicates that ‘‘other waters’’ have 

important hydrologic, water quality, and 

habitat functions that have the ability to 

affect downstream waters if and when a 

connection exists between the ‘‘other water’’ 

and downstream waters. Report at 6–1. 

‘‘Other waters’’ generally fit into the category 

of unidirectional waters as described in the 

Report. However, there are some 

unidirectional waters that are in fact adjacent 

under (a)(6) to (a)(1) through (a)(5) waters 

(e.g., neighboring waters that are outside of 

the riparian area and/or floodplain but that 

have a surface or shallow subsurface 

hydrologic connection to (a)(1) through (a)(5) 

waters). Connectivity of ‘‘other waters’’ to 

downstream waters that do not meet the 

definition of adjacent will vary within a 

watershed and over time, which is why a 

case-specific significant nexus determination 

for ‘‘other waters’’ is necessary under (a)(7). 

See, e.g., id. at 6–2. The types of chemical, 

physical, and biological connections between 

‘‘other waters’’ and downstream waters are 

described below for illustrative purposes. As 

described in the preamble above, when the 

agencies are conducting a case-specific 

determination for significant nexus under 

(a)(7), they examine the connections between 

the water (including any similarly situated 

waters in the region) and downstream waters 

and determine if those connections 

significantly affect the chemical, physical, or 

biological integrity of the downstream water, 

using any available site-information and field 

observations where available, relevant 

scientific studies or data, or other relevant 

jurisdictional determinations that have been 

made on similar resources in the region. 

The hydrologic connectivity of ‘‘other 

waters’’ to downstream waters occurs on a 

gradient and can include waters that have 

groundwater or occasional surface water 

connections (through overland flow) to the 

tributary network and waters that have no 

hydrologic connection to the tributary 

network. Id. at 5–1. The connectivity of 

‘‘other waters’’ to downstream waters will 

vary within a watershed as a function of local 

factors (e.g. position, topography, and soil 

characteristics). Id. at 3–41 to 3–43. 

Connectivity also varies over time, as the 

tributary network and water table expand 

and contract in response to local climate. Id. 

at 3–31 to 3–33. Lack of connection does not 

necessarily translate to lack of impact; even 

when lacking connectivity, waters can still 

impact chemical, physical, and biological 

conditions downstream. Id. at 3–29, 3–31. 

The physical effect that ‘‘other waters’’ 

have downstream is less obvious than the 

physical connections of waters that are 

adjacent or waters that are tributary, due to 

the physical distance of ‘‘other waters’’ from 

the stream network. Despite this physical 

distance, they are frequently connected in 

some degree through either surface water or 

groundwater systems; over time, impacts in 

one part of the hydrologic system will be felt 

in other parts. T.C. Winter and J.W. LaBaugh, 

‘‘Hydrologic Considerations in Defining 

Isolated Wetlands,’’ Wetlands 23:532–540 

(2003) at 538. For example, ‘‘other waters’’ 

that overspill into downstream water bodies 

during times of abundant precipitation are 

connected over the long term. Id. at 539. 

Wetlands that lack surface connectivity in a 

particular season or year can, nonetheless, be 

highly connected in wetter seasons or years. 

Report at 5–22 to 5–25. Many ‘‘other waters’’ 

interact with groundwater, either by 

receiving groundwater discharge (flow of 

groundwater to the ‘‘other water’’), 

contributing to groundwater recharge (flow of 

water from the ‘‘other water’’ to the 

groundwater), or both. Id. at 5–23 (citing R.F. 

Lide, et al., ‘‘Hydrology of a Carolina Bay 

Located on the Upper Coastal Plain of 

Western South Carolina,’’ Wetlands 15:47–57 

(1995); K.J. Devito, et al., ‘‘Groundwater 

Surface-Water Interactions in Headwater 

Forested Wetlands of the Canadian Shield,’’ 

Journal of Hydrology 181:127–47 (1996); R.K. 

Matheney and P.J. Gerla, ‘‘Environmental 

Isotopic Evidence for the Origins of Ground 

and Surface Water in a Prairie Discharge 

Wetland,’’ Wetlands 16:109–120 (1996); D.O. 

Rosenberry and T.C. Winter, ‘‘Dynamics of 

Water-Table Fluctuations in an Upland 

between Two Prairie-Pothole Wetlands in 

North Dakota,’’ Journal of Hydrology 

191:266–289 (1997); J.E. Pyzoha, et al., ‘‘A 

Conceptual Hydrologic Model for a Forested 

Carolina Bay Depressional Wetland on the 

Coastal Plain of South Carolina, USA,’’ 

Hydrological Processes 22:2689–2698 

(2008)). Factors that determine whether a 

water recharges groundwater or is a site of 

groundwater discharge include topography, 

geology, soil features, and seasonal position 

of the water table relative to the water. Id. at 

5–24 (citing P.J. Phillips and R.J. Shedlock, 

‘‘Hydrology and Chemistry of Groundwater 

and Seasonal Ponds in the Atlantic CoastalPlain in Delaware, USA,’’ Journal of 

Hydrology 141:157–78 (1993); R.J. Shedlock, 

et al., ‘‘Interactions between Ground-Water 

and Wetlands, Southern Shore of LakeMichigan, USA,’’ Journal of Hydrology 

141:127–55 (1993); D.O. Rosenberry and T.C. 

Winter, ‘‘Dynamics of Water-Table 

Fluctuations in an Upland Between two 

Prairie-Pothole Wetlands in North Dakota,’’ 

Journal of Hydrology 191:266–89 (1997); J.E. 

Pyzoha, et al., ‘‘A Conceptual Hydrologic 

Model for a Forested Carolina Bay 

Depressional Wetland on the Coastal Plain of 

South Carolina, USA,’’ Hydrological 

Processes 22: 2689–98 (2008)). Similarly, the 

magnitude and transit time of groundwater 

flow from an ‘‘other water’’ to downstream 

waters depend on several factors, including 

the intervening distance and the properties of 

the rock or unconsolidated sediments 

between the water bodies (i.e., the hydraulic 

conductivity of the material). Id. at 5–24. 

Surface and groundwater hydrological 

connections are those generating the capacity 

for ‘‘other waters’’ to affect downstream 

waters, as water from the ‘‘other water’’ may 

contribute to baseflow or stormflow through 

groundwater recharge. Id. at 5–25. 

Contributions to baseflow are important for 

maintaining conditions that support aquatic 

life in downstream waters. As discussed 

further below, even in cases where waters 

lack a connection to downstream waters, they 

can influence downstream water through 

water storage and mitigation of peak flows. 

Id. at 5–36. 

The chemical effects that ‘‘other waters’’ 

have on downstream waters are linked to 

their hydrologic connection downstream, 

though a surface connection is not needed for 

a water to influence the chemical integrity of 

the downstream water. Because the majority 

of ‘‘other waters’’ are hydrologically 

connected to downstream waters via surface 

or groundwater connections, most ‘‘other 

waters’’ can affect water quality downstream 

(although these connections do not meet the 

definition of adjacency). D.F. Whigham and 

T. E. Jordan, ‘‘Isolated Wetlands and Water 

Quality,’’ Wetlands 23:541–549 (2003) at 542. 

‘‘Other waters’’ can act as sinks and 

transformers for nitrogen and phosphorus, 

metals, pesticides, and other contaminants 

that could otherwise negatively impact 

downstream waters. Report at 5–30 (citing 

R.R. Brooks, et al., ‘‘Cobalt and Nickel 

Uptake by the Nyssaceae,’’ Taxon 26:197–201 

(1977); H.F. Hemond, ‘‘Biogeochemistry of 

Thoreau’s Bog, Concord, Massachusetts,’’ 

Ecological Monographs 50:507–526 (1980); 

C.B. Davis, et al., ‘‘Prairie Pothole Marshes as 

Traps for Nitrogen and Phosphorus in 

Agricultural Runoff,’’ in B. Richardson, ed., 

Selected Proceedings of the Midwest 

Conference on Wetland Values and 

Management, June 17–19, 1981, St. Paul, MN, 

(St. Paul, MN: The Freshwater Society, 1981), 

pp. 153–163; H.F. Hemond, ‘‘The Nitrogen 

Budget of Thoreau’s Bog,’’ Ecology 64:99–109 

(1983); K.C. Ewel and H.T. Odum, ed., 

Cypress Swamps, (Gainesville, Florida: 

University of Florida Press, 1984); J.T. 

Moraghan, ‘‘Loss and Assimilation of 15Nnitrate Added to a North Dakota Cattail 

Marsh,’’ Aquatic Botany 46:225–234 (1993); 

C.M. Kao, et al., ‘‘Non-point Source Pesticide 

Removal by a Mountainous Wetland,’’ Water 

Science and Technology 46:199–206 (2002); 

P.I. Boon, ‘‘Biogeochemistry and Bacterial 

Ecology of Hydrologically Dynamic 

Wetlands,’’ in D.P. Batzer and R.R. Sharitz, 

ed., Ecology of Freshwater and Estuarine 

Wetlands (Berkeley, CA: University of 

California Press, 2006), pp. 115–176; E.J. 

Dunne, et al., ‘‘Phosphorus Release and 

Retention by Soils of Natural Isolated 

Wetlands,’’ International Journal of 

Environment and Pollution 28:496–516 

(2006); T.E. Jordan, et al., ‘‘Comparing 

Functional Assessments of Wetlands to 

Measurements of Soil Characteristics and 

Nitrogen Processing,’’ Wetlands 27:479–497 


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(2007); S.L. Whitmire and S.K. Hamilton, 

‘‘Rates of Anaerobic Microbial Metabolism in 

Wetlands of Divergent Hydrology on a 

Glacial Landscape,’’ Wetlands 28:703–714 

(2008)). Also see, e.g., T.M. Isenhart, 

Transformation and Fate of Nitrate in 

Northern Prairie Wetlands, Ph.D. Dissertation 

(Ames, Iowa: Iowa State University, 1992). 

The body of published scientific literature 

and the Report indicate that sink removal of 

nutrients and other pollutants by ‘‘other 

waters’’ is significant and geographically 

widespread. Report at 5–30. Water quality 

characteristics of ‘‘other waters’’ are highly 

variable, depending primarily on the sources 

of water, characteristics of the substrate, and 

land uses within the watershed. D.F. 

Whigham and T.E. Jordan, ‘‘Isolated 

Wetlands and Water Quality,’’ Wetlands 

23:541–549 (2003) at 541. These variables 

inform whether an ‘‘other water’’ has a 

significant nexus to an (a)(1) through (a)(3) 

water. For instance, some prairie potholes 

may improve water quality and may 

efficiently retain nutrients that might 

otherwise cause water quality problems 

downstream; in such systems it may be their 

lack of a direct hydrologic connection that 

enables the prairie potholes to more 

effectively retain nutrients. Id. at 543. 

‘‘Other waters’’ can be biologically 

connected to each other and to downstream 

waters through the movement of seeds, 

macroinvertebrates, amphibians, reptiles, 

birds, and mammals. Report at 5–31 to 5–33; 

S.G. Leibowitz, ‘‘Isolated Wetlands and Their 

Functions: An Ecological Perspective,’’ 

Wetlands 23:517–531 (2003) at 519. The 

movement of organisms between ‘‘other 

waters’’ and downstream waters is governed 

by many of the same factors that affect 

movement of organisms between adjacent 

wetlands and downstream waters (See Part II 

Section 2.A.d.). Report at 5–31. Generally, 

‘‘other waters’’ are further away from stream 

channels than adjacent waters, making 

hydrologic connectivity less frequent, and 

increasing the number and variety of 

landscape barriers over which organisms 

must disperse. Id. Plants, though non-mobile, 

have evolved many adaptations to achieve 

dispersal over a variety of distances, 

including water-borne dispersal during 

periodic hydrologic connections, 

‘‘hitchhiking’’ on or inside highly mobile 

animals, and more typically via wind 

dispersal of seeds and/or pollen. Id. at 5–31 

(citing S.M. Galatowitsch and A.G. van der 

Valk, ‘‘The Vegetation of Restored and 

Natural Prairie Wetlands,’’Ecological 

Applications 6:102–112 (1996); H.R. Murkin 

and P.J. Caldwell, ‘‘Avian Use of Prairie 

Wetlands,’’ in H.R. Murkin, et al., ed., Prairie 

Wetland Ecology: The Contribution of the 

Marsh Ecology Research Program, (Ames, IA: 

Iowa State University Press, 2000), pp. 249– 

286; J.M. Amezaga, et al., ‘‘Biotic Wetland 

Connectivity—Supporting a New Approach 

for Wetland Policy,’’ Acta OecologicaInternational Journal of Ecology 23:213–222 

(2002); J. Figuerola and A.J. Green, ‘‘Dispersal 

of Aquatic Organisms by Waterbirds: a 

Review of Past Research and Priorities for 

Future Studies,’’ Freshwater Biology 47:483– 

494 (2002); M.B. Soons and G.W. Heil, 

‘‘Reduced Colonization Capacity in 

Fragmented Populations of Wind-Dispersed 

Grassland Forbs,’’ Journal of Ecology 

90:1033–1043 (2002); M.B. Soons, ‘‘Wind 

Dispersal in Freshwater Wetlands: 

Knowledge for Conservation and 

Restoration,’’ Applied Vegetation Science 

9:271–278 (2006); C. Nilsson, et al., ‘‘The 

Role of Hydrochory in Structuring Riparian 

and Wetland Vegetation,’’ Biological Reviews 

85:837–858 (2010)). Mammals that disperse 

overland can also contribute to connectivity 

and can act as transport vectors for 

hitchhikers such as algae. Id. at 5–32 (citing 

C.E. Shanks and G.C. Arthur, ‘‘Muskrat 

Movements and Population Dynamics in 

Missouri Farm Ponds and Streams,’’ Journal 

of Wildlife Management 16:138–148 (1952); 

J.P. Roscher, ‘‘Alga Dispersal by Muskrat 

Intestinal Contents,’’ Transactions of the 

American Microscopical Society 86:497–498 

(1967); W.R. Clark, ‘‘Ecology of Muskrats in 

Prairie Wetlands,’’ in H. R. Murkin, et al., ed., 

2000, pp. 287–313)). Invertebrates also utilize 

birds and mamals to hitchhike, and these 

hitchhikers can be an important factor 

structuring invertebrate metapopulations in 

‘‘other waters’’ and in aquatic habitats 

separated by hundreds of kilometers. Id. 

(citing J. Figuerola and A.J. Green, ‘‘Dispersal 

of Aquatic Organisms by Waterbirds: A 

Review of Past Research and Priorities for 

Future Studies,’’ Freshwater Biology 47:483– 

494 (2002); J. Figuerola, et al., ‘‘Invertebrate 

Eggs Can Fly: Evidence of WaterfowlMediated Gene Flow in Aquatic 

Invertebrates,’’ American Naturalist 165:274– 

280 (2005); M.R. Allen, ‘‘Measuring and 

Modeling Dispersal of Adult Zooplankton,’’ 

Oecologia 153:135–143 (2007); D. Frisch, et 

al., ‘‘High Dispersal Capacity of a Broad 

Spectrum of Aquatic Invertebrates Via 

Waterbirds,’’ Aquatic Sciences 69:568–574 

(2007)). Numerous flight-capable insects use 

both ‘‘other waters’’ and downstream waters; 

these insects move outside the tributary 

network to find suitable habitat for 

overwintering, refuge from adverse 

conditions, hunting, foraging, or breeding, 

and then can return back to the tributary 

network for other lifecycle needs. Id. at 5–33 

(citing D.D. Williams, ‘‘Environmental 

Constraints in Temporary Fresh Waters and 

Their Consequences for the Insect Fauna,’’ 

Journal of the North American Benthological 

Society 15:634–650 (1996); A.J. Bohonak and 

D.G. Jenkins, ‘‘Ecological and Evolutionary 

Significance of Dispersal by Freshwater 

Invertebrates,’’ Ecology Letters 6:783–796 

(2003)). Amphibians and reptiles also move 

between ‘‘other waters’’ and downstream 

waters to satisfy part of their life history 

requirements. Id. at 5–33. Alligators in the 

Southeast, for instance, can move from 

tributaries to shallow, seasonal limesink 

wetlands for nesting, and also use these 

wetlands as nurseries for juveniles; subadults then shift back to the tributary 

network through overland movements. Id. 

(citing A.L. Subalusky, et al., ‘‘Ontogenetic 

Niche Shifts in the American Alligator 

Establish Functional Connectivity between 

Aquatic Systems,’’ Biological Conservation 

142:1507–1514 (2009); A.L. Subalusky, et al., 

‘‘Detection of American Alligators in 

Isolated, Seasonal Wetlands,’’ Applied 

Herpetology 6:199–210 (2009)). Similarly, 

amphibians and small reptile species, such as 

frogs, toads, and newts, commonly use both 

tributaries and ‘‘other waters,’’ during one or 

more stages of their life cycle, and can at 

times disperse over long distances. Id. (citing 

V.S. Lamoureux and D.M. Madison, 

‘‘Overwintering Habitats of Radio-Implanted 

Green Frogs, Rana clamitans,’’ Journal of 

Herpetology 33:430–435 (1999); K.J. Babbitt, 

et al., ‘‘Patterns of Larval Amphibian 

Distribution along a Wetland Hydroperiod 

Gradient,’’ Canadian Journal of ZoologyRevue Canadienne De Zoologie 81:1539– 

1552 (2003); S.B. Adams, et al., ‘‘Instream 

Movements by Boreal Toads (Bufo boreas 

boreas),’’ Herpetological Review 36:27–33 

(2005); D.M. Green, ‘‘Bufo americanus, 

American Toad,’’ in M. Lannoo, ed., 

Amphibian Declines: The Conservation 

Status of the United States Species (Berkeley, 

CA: University of California Press, 2005), pp. 

692–704; T.W. Hunsinger and M. J. Lannoo, 

‘‘Notophthalmus viridescens, Eastern Newt,’’ 

in M. Lannoo, ed., 2005, pp. 912–914; J.W. 

Petranka and C.T. Holbrook, ‘‘Wetland 

Restoration for Amphibians: Should Local 

Sites Be Designed to Support 

Metapopulations or Patchy Populations?,’’ 

Restoration Ecology 14:404–411 (2006)). 

Even when a surface or groundwater 

hydrologic connection between a water and 

a downstream water is visibly absent, many 

waters still have the ability to substantially 

influence the integrity of downstream waters. 

However, such circumstances would be 

uncommon. Id. at 5–22 to 5–25. Aquatic 

systems that may seem disconnected 

hydrologically are often connected but at 

irregular timeframes or through subsurface 

flow, and perform important functions that 

can be vital to the chemical, physical, or 

biological integrity of downstream waters. 

Some wetlands that are not adjacent may be 

hydrologically disconnected most of the time 

but connected to the stream network during 

rare high-flow events. The lack of a 

hydrologic connection also allows for water 

storage in ‘‘other waters,’’ attenuating peak 

streamflows, and, thus, downstream flooding, 

and also reducing nutrient and soil pollution 

in downstream waters. Report at 5–25 to 5– 

26, 5–36. Prairie potholes a great distance 

from any tributary, for example, are thought 

to store significant amounts of runoff. Id. at 

5–36 (citing R.P. Novitzki, ‘‘Hydrologic 

Characteristics of Wisconsin’s Wetlands and 

Their Influence on Floods,’’ in P. Greeson, et 

al., ed., Wetland Functions and Values: The 

Status of Our Understanding, Proceedings of 

the National Symposium on Wetlands 

(Minneapolis, MN: American Water 

Resources Association, 1979), pp. 377–388; 

D.E. Hubbard and R.L. Linder, ‘‘Spring 

Runoff Retention in Prairie Pothole 

Wetlands,’’ Journal of Soil and Water 

Conservation 41:122–125 (1986); J. Jacques 

and D.L. Lorenz, ‘‘Techniques for Estimating 

the Magnitude and Frequency of Floods in 

Minnesota,’’ Water Resources Investigations 

Report 87–4170, (St. Paul, MN: U.S. 

Geological Survey, 1988); K.C. Vining, 

‘‘Simulation of Streamflow and Wetland 

Storage, Starkweather Coulee Subbasin, 

North Dakota, Water Years 1981–98,’’ WaterResources Investigations Report 02–4113 

(Bismarck, North Dakota: U.S. Geological 


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Survey, 2002); R.A. Gleason, et al., 

Estimating Water Storage Capacity of 

Existing and Potentially Restorable Wetland 

Depressions in a Subbasin of the Red River 

of the North, U.S. Geological Survey OpenFile Report 2007–1159 (Reston, VA: U.S. 

Geological Survey, 2007); D.L. Lorenz, et al., 

‘‘Techniques for Estimating the Magnitude 

and Frequency of Peak Flows on Small 

Streams in Minnesota Based on Through 

Water Year 2005,’’ USGS Scientific 

Investigations Report 2009–5250, (Reston, 

VA: U.S. Geological Survey, 2010)). Filling 

wetlands reduces water storage capacity in 

the landscape and causes runoff from 

rainstorms to overwhelm the remaining 

available water conveyance system. See, e.g., 

C.A. Johnston, et al., ‘‘The Cumulative Effect 

of Wetlands on Stream Water Quality and 

Quantity,’’ Biogeochemistry 10:105–141 

(1990); A.L. Moscrip and D.R. Montgomery, 

‘‘Urbanization, Flood Frequency, and Salmon 

Abundance in Puget Lowland Streams,’’ 

Journal of the American Water Resources 

Association 33:1289–1297 (1997); N.E. 

Detenbeck, et al., ‘‘Evaluating Perturbations 

and Developing Restoration Strategies for 

Inland Wetlands in the Great Lakes Basin,’’ 

Wetlands 19(4): 789–820 (1999); N.E. Beck, et 

al., ‘‘Relationship of Stream Flow Regime in 

the Western Lake Superior Basin to 

Watershed Type Characteristics,’’ Journal of 

Hydrology 309(1–4): 258–276 (2005). 

Wetlands, even when lacking a hydrologic 

connection downstream, improve 

downstream water quality by accumulating 

nutrients, trapping sediments, and 

transforming a variety of substances. See, 

e.g., National Research Council, Wetlands: 

Characteristics and Boundaries (Washington, 

DC: National Academy Press, 1995), p. 38. 

Under today’s proposal, on a case-specific 

basis, ‘‘other waters’’ that have a significant 

nexus to an (a)(1) through (a)(3) water are 

‘‘waters of the United States’’ under (a)(7). 

The scientific literature and data in the 

Report and elsewhere support that some 

‘‘other waters’’ (including some of those in 

the case studies), along with other similarly 

situated waters in the region, do greatly affect 

the chemical, physical, or biological integrity 

of (a)(1) through (a)(3) waters, and thus 

would be jurisdictional under (a)(7). 

Though much of the literature cited in the 

Report relates to ‘‘other waters’’ that are 

wetlands, the Report indicates that nonwetland waters that are not (a)(1) through 

(a)(6) waters also can have chemical, 

physical, or biological connections that 

significantly impact downstream waters. For 

instance, non-adjacent ponds or lakes that are 

not part of the tributary network can still be 

connected to downstream waters through 

chemical, physical, and biological 

connections. Lake storage has been found to 

attenuate peak streamflows in Minnesota. Id. 

at 5–25 (citing J. Jacques and D.L. Lorenz, 

Techniques for Estimating the Magnitude 

and Frequency of Floods of Ungauged 

Streams in Minnesota, USGS WaterResources Investigations Report 84–4170 

(Washington, DC: U.S. Geological Survey, 

1988); D.L. Lorenz, et al., Techniques for 

Estimating the Magnitude and Frequency of 

Peak Flows on Small Streams in Minnesota 

Based on Data through Water Year 2005, U.S. 

Geological Survey Scientific Investigations 

Report 2009–5250 (Reston, VA: U.S. 

Geological Survey, 2010)). Similar to 

wetlands, ponds are often used by 

invertebrate, reptile, and amphibian species 

that also utilized downstream waters for 

various life history requirements, particularly 

because many ponds, particularly temporary 

ponds, are free of predators, such as fish, that 

prey on larvae. The American toad and 

Eastern newt are widespread habitat 

generalists that can move among streams, 

wetlands, and ponds to take advantage of 

each aquatic habitat, feeding on aquatic 

invertebrate prey, and avoiding predators. 

See, e.g., Id. at 5–33 (citing K.J. Babbitt et al., 

‘‘Patterns of Larval Amphibian Distribution 

along a Wetland Hydroperiod Gradient,’’ 

Canadian Journal of Zoology-Revue 

Canadienne De Zoologie 81:1539–1552 

(2003); D.M. Green, ‘‘Bufo americanus, 

American Toad,’’ in M. Lannoo, ed., 

Amphibian Declines: The Conservation 

Status of United States Species, (Berkeley, 

CA: University of California Press, 2005), pp. 

692–704; T.W. Hunsinger and M.J. Lannoo, 

‘‘Notophthalmus viridescens, Eastern Newt,’’ 

in M. Lannoo, ed., Amphibian Declines: The 

Conservation Status of United States Species, 

(Berkeley, CA: University of California Press, 

2005), pp. 912–914; J.W. Petranka and C.T. 

Holbrook, ‘‘Wetland Restoration for 

Amphibians: Should Local Sites Be Designed 

to Support Metapopulations or Patchy 

Populations?,’’ Restoration Ecology 14:404– 

411 (2006)). Additionally, stream networks 

that are not part of the tributary system (e.g., 

streams in closed basins without an (a)(1) 

through (a)(3) water or losing streams and 

other streams that cease to flow before 

reaching downstream (a)(1) through (a)(3) 

waters) may likewise have a significant 

impact on the chemical, physical, or 

biological integrity of downstream waters. 

Non-tributary streams may be connected via 

groundwater to downstream waters. Such 

streams may also provide habitat to insect, 

amphibian, and reptile species that also use 

the tributary network. 

i. Additional Request for Public Comment on 

‘‘Other Waters’’ 

The agencies are considering whether to 

determine by rule that prairie potholes, 

Carolina and Delmarva bays, pocosins, Texas 

coastal prairie wetlands, western vernal 

pools, and perhaps other categories of waters, 

either alone or in combination with ‘‘other 

waters’’ of the same type in a single point of 

entry watershed have a significant nexus and 

are jurisdictional. R.W. Tiner, 

‘‘Geographically Isolated Wetlands of the 

United States,’’ Wetlands 23(3):494–516 

(2003); M.G. Forbes, et al., ‘‘Nutrient 

Transformation and Retention by Coastal 

Prairie Wetlands, Upper Gulf Coast, Texas,’’ 

Wetlands 32(4): 705–715 (2012). These 

waters would not require a case-by-case 

analysis. At the same time, the agencies 

could determine by rule that playa lakes, and 

perhaps other categories of waters, do not 

have a significant nexus and are not 

jurisdictional. These waters would not be 

subject to a case-by-case analysis of 

significant nexus. As the science develops, 

the agencies may determine that additional 

categories of ‘‘other waters’’ have a 

significant nexus and are thus categorically 

jurisdictional. The specific categories of 

‘‘other waters’’ for which there is currently 

evidence of a significant nexus are discussed 

below: 

a. Prairie potholes are a complex of 

glacially formed wetlands, usually occurring 

in depressions that lack permanent natural 

outlets, that are found in the central United 

States and Canada. Report at 5–57. The vast 

area they occupy is variable in many aspects, 

including climatically, topographically, 

geologically, and in terms of land use and 

alteration, which imparts variation on the 

potholes themselves. Prairie potholes 

demonstrate a wide range of hydrologic 

permanence, from holding permanent 

standing water to wetting only in years with 

high precipitation, which in turn influences 

the diversity and structure of their biological 

communities. Owing in large part to their 

spatial and temporal variability, individual 

prairie potholes span the entire continuum of 

connectivity to and isolation from the river 

network and other bodies of water. Potholes 

generally accumulate and retain water 

effectively due to the low permeability of 

their underlying soil, which can modulate 

flow characteristics of nearby streams and 

rivers. Potholes also can accumulate 

chemicals in overland flow, thereby reducing 

chemical loading to other bodies of water. 

When potholes are artificially connected to 

streams and lakes through drainage, isolation 

is eliminated and they become sources of 

water and chemicals. Potholes also support a 

community of highly mobile organisms, from 

plants to invertebrates that move among 

potholes and that can biologically connect 

the entire complex to the river network. 

Based on these connections and the strength 

of their effects, individually or in 

combination with other prairie potholes in 

the watershed, on the chemical, physical, or 

biological integrity of an (a)(1) through (a)(3) 

water, the agencies could conclude by rule 

that prairie potholes have a significant nexus 

and are jurisdictional. The agencies’ 

determination will be informed by the final 

version of the Report and other available 

scientific information. 

b. Carolina and Delmarva bays are ponded 

depressional wetlands that occur along the 

Atlantic coastal plain from northern Florida 

to New Jersey. Id. at 5–49. Most bays receive 

water through precipitation, lose water 

through evapotranspiration, and lack natural 

surface outlets. Both mineral-based and peatbased bays have shown connections to 

shallow groundwater. Bays typically are in 

proximity to each other or to open waters, 

providing the potential for surface water 

connections in large rain events via overland 

flow. Fish are reported in bays that are 

known to dry out, indirectly demonstrating 

surficial connections. Amphibians and 

reptiles use bays extensively for breeding and 

for rearing young. These animals can 

disperse many meters on the landscape and 

can colonize, or serve as a food source to, 

downstream waters. Similarly, bays foster 

abundant insects that have the potential to 

become part of the downstream food chain. 

Humans have ditched and channelized a 

high percentage of bays, creating new surface 

connections to ‘‘other waters’’ and allowing 


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transfer of nutrients, sediment, and other 

pollutants such as methylmercury. Based on 

these connections and the strength of their 

effects, individually or in combination with 

other Carolina or Delmarva bays in the 

watershed, on the chemical, physical, or 

biological integrity of an (a)(1) through (a)(3) 

water, the agencies could conclude by rule 

that Carolina and Delmarva bays have a 

significant nexus and are jurisdictional. The 

agencies’ determination will be informed by 

the final version of the Report and other 

available scientific information. 

c. Vernal pools are shallow, seasonal 

wetlands that accumulate water during 

colder, wetter months and gradually dry up 

during warmer, drier months. Id. at 5–66. 

Western vernal pools are seasonal wetlands 

associated with topographic depressions, 

soils with poor drainage, mild, wet winters 

and hot, dry summers in western North 

America from southeastern Oregon to 

northern Baja California, Mexico (Id. at 5–67, 

citing E.T. Bauder and S. McMillan, ‘‘Current 

Distribution and Historical Extent of Vernal 

Pools in Southern California and Northern 

Baja California, Mexico,’’ pp. 56–70 in C.W. 

Witham, et al., editors, Ecology, 

Conservation, and Management, 1998). 

Because their hydrology and ecology are so 

tightly coupled with the local and regional 

geological processes that formed them, 

western vernal pools typically occur within 

‘‘vernal pool landscapes,’’ or complexes of 

pools in which swales connect pools to each 

other and to seasonal streams (Id. at 5–67 to 

5–68, citing W.A. Weitkamp, et al., 

‘‘Pedogenesis of a Vernal Pool EntisolAlfisol-Vertisol Catena in Southern 

California,’’ Soil Science Society of America 

Journal 60:316323 (1996); D.W. Smith and 

W.L. Verrill, ‘‘Vernal Pool-Soil-Landform 

Relationships in the Central Valley, 

California,’’ pp. 15–23 in C.W. Witham, et al., 

editors, Ecology, Conservation, and 

Management of Vernal Pool Ecosystems— 

Proceedings from a 1996 Conference 

(California Native Plant Society, Sacramento, 

CA,1998); M.C. Rains, et al., ‘‘The Role of 

Perched Aquifers in Hydrological 

Connectivity and Biogeochemical Processes 

in Vernal Pool Landscapes, Central Valley, 

California,’’ Hydrological Processes 20:1157– 

1175 (2008)). Despite differences in geology, 

climate, and biological communities, some 

common findings about the hydrologic 

connectivity of vernal pools in different 

regions, including Western vernal pools, 

include evidence for temporary or permanent 

outlets, frequent filling and spilling of higher 

pools into lower elevation swales and stream 

channels, and conditions supporting 

subsurface flows through pools without 

perched aquifers to nearby streams. Nonglaciated vernal pools in western states are 

reservoirs of biodiversity and can be 

connected genetically to other locations and 

aquatic habitats through wind- and animalmediated dispersal. Based on these 

connections and the strength of their effects, 

individually or in combination with other 

western vernal pools in the watershed, on the 

chemical, physical, or biological integrity of 

an (a)(1) through (a)(3) water, the agencies 

could conclude by rule that western vernal 

pools have a significant nexus and are 

jurisdictional. The agencies’ determination 

will be informed by the final version of the 

Report and other available scientific 

information. The jurisdictional status of 

vernal pools located in other areas will be 

determined on a case-by-case significant 

nexus analysis with any similar situated 

waters in the single point of entry watershed. 

For example, insects and amphibians that 

can live in streams or permanent pools 

opportunistically use glaciated vernal pools 

in the Northeast and Midwest as alternative 

breeding habitat, refuge from predators or 

environmental stressors, hunting or foraging 

habitat, or stepping-stone corridors for 

dispersal and migration. 

d. The word pocosin comes from the 

Algonquin Native American word for 

‘‘swamp on a hill,’’ and these evergreen 

shrub and tree dominated landscapes are 

found from Virginia to northern Florida, but 

mainly in North Carolina. (C.J. Richardson, 

‘‘Pocosins: Hydrologically Isolated or 

Integrated Wetlands on the Landscape?,’’ 

Wetlands 23(3):563–576 (2003)). Usually, 

there is no standing water present in these 

peat-accumulating wetlands, but a shallow 

water table leaves the soil saturated for much 

of the year. They range in size from less than 

an acre to several thousand acres. The slow 

movement of water through the dense 

organic matter in pocosins removes excess 

nutrients deposited by rainwater. The same 

organic matter also acidifies the water. This 

pure water is slowly released to downstream 

waters and estuaries, where it helps to 

maintain the proper salinity, nutrients, and 

acidity. (Id.) Because pocosins are the 

topographic high areas on the regional 

landscape, they serve as the source of water 

for downstream areas. Pocosins often have 

seasonal connections to drainageways 

leading to estuaries or are contiguous with 

other wetlands draining into perennial 

streams or estuaries. (R.W. Tiner, 

‘‘Geographically Isolated Wetlands of the 

United States,’’ Wetlands 23(3):494–516 

(2003)). Other pocosins have been ditched 

and are directly connected to streams. (Id.) 

The draining of pocosins and decreased 

salinity in estuaries may be having a negative 

effect on brown shrimp in North Carolina. 

(Id.) Based on these connections and the 

strength of their effects, individually or in 

combination with other pocosins in the 

watershed, on the chemical, physical, or 

biological integrity of an (a)(1) through (a)(3) 

water, the agencies could conclude by rule 

pocosins have a significant nexus and are 

jurisdictional. The agencies’ determination 

will be informed by the final version of the 

Report and other available scientific 

information. 

e. Along the Gulf of Mexico from western 

Louisiana to south Texas, freshwater 

wetlands occur as a mosaic of depressions, 

ridges, intermound flats, and mima mounds. 

(M.G. Forbes, et al., ‘‘Nutrient 

Transformation and Retention by Coastal 

Prairie Wetlands, Upper Gulf Coast, Texas,’’ 

Wetlands 32(4): 705–715 (2012)). These 

coastal prairie wetlands were formed 

thousands of years ago by ancient rivers and 

bayous and once occupied almost a third of 

the landscape around Galveston Bay, Texas. 

Texas coastal prairie wetlands are locally 

abundant and in close proximity to other 

coastal prairie wetlands and function 

together cumulatively. (N. Enwright, et al., 

‘‘Using Geographic Information Systems 

(GIS) to Inventory Coastal Prairie Wetlands 

Along the Upper Gulf Coast, Texas,’’ 

Wetlands 31:687–697 (2011)). Collectively as 

a complex, Texas coastal prairie wetlands 

may be geographically and hydrologically 

connected to each other via swales and 

connected to downstream waters, 

contributing flow to those downstream 

waters. (B.P. Wilcox, et al., ‘‘Evidence of 

Surface Connectivity for Texas Gulf Coast 

Depressional Wetlands,’’ Wetlands 

31(3):451–458 (2011)). Cumulatively, these 

wetlands can control nutrient release levels 

and rates to downstream waters, as they 

capture, store, transform and pulse releases 

of nutrients to those waters. (M.G. Forbes, et 

al., ‘‘Nutrient Transformation and Retention 

by Coastal Prairie Wetlands, Upper Gulf 

Coast, Texas,’’ Wetlands 32(4): 705–715 

(2012)). Based on these connections and the 

strength of their effects, individually or in 

combination with other coastal prairie 

wetlands in the watershed, on the chemical, 

physical, or biological integrity of an (a)(1) 

through (a)(3) water, the agencies could 

conclude by rule Texas coastal prairie 

wetlands have a significant nexus and are 

jurisdictional. The agencies’ determination 

will be informed by the final version of the 

Report and other available scientific 

information. 

The agencies could also conclude that 

playa lakes in the Great Plains even in 

combination with other playa lakes in a 

single point of entry watershed always lack 

a significant nexus and therefore are not 

jurisdictional. Playa lakes are round, shallow 

wetlands found primarily in the High Plains, 

a subregion of the Great Plains in the western 

and Midwestern United States. (D.A. Haukos, 

and L.M. Smith, ‘‘Past and Future Impacts of 

Wetland Regulations on Playas,’’ Wetlands 

23(3):577–589 (2003); R.W. Tiner, 

‘‘Geographically Isolated Wetlands of the 

United States,’’ Wetlands 23(3):494–516 

(2003)). Each playa typically occurs within a 

closed or terminal watershed, where all water 

in the watershed drains to the playa. (D.A. 

Haukos, and L.M. Smith, ‘‘Past and Future 

Impacts of Wetland Regulations on Playas,’’ 

Wetlands 23(3):577–589 (2003)). As such, 

playas typically do not drain to an (a)(1) 

through (a)(3) water. Most playas are fed by 

precipitation and associated runoff, though a 

few are fed by groundwater. (R.W. Tiner, 

‘‘Geographically Isolated Wetlands of the 

United States,’’ Wetlands 23(3):494–516 

(2003)). Most playas fill with water only after 

spring rainstorms when freshwater collects in 

the round depressions of the otherwise flat 

landscape of west Texas, Oklahoma, New 

Mexico, Colorado, and Kansas. Although 

playas play a role in groundwater recharge of 

the Ogallala Aquifer, in local floodwater 

storage, and in provision of wildlife habitat, 

available scientific literature indicates that 

their chemical, physical, or biological 

connections to and effects on (a)(1) through 

(a)(3) waters are of a limited and tenuous 

nature. 

The agencies seek comment, data, and 

information on whether there are 


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9The 1972 legislation extensively amended the 

Federal Water Pollution Control Act (FWPCA), 

which was originally enacted in 1948. Further 

amendments to the FWPCA enacted in 1977 

acknowledged the popular name of the statute as 

the Clean Water Act. See Public Law 95–217, 91 

Stat. 1566; 33 U.S.C. 1251 note. 

subcategories of ‘‘other waters’’ or specific 

combinations of characteristics that are 

‘‘likely, in the majority of cases, to perform 

important functions for an aquatic ecosystem 

incorporating navigable waters,’’ and, thus, 

should be per se jurisdictional. For example, 

if there are additional studies addressing the 

connectivity of prairie potholes in the Red 

River Valley, including the factors 

influencing that connectivity and how it is 

important to particular downstream waters, 

that would be relevant information. 

Appendix B 

Legal Analysis 

Background 

Congress enacted the Federal Water 

Pollution Control Act Amendments of 1972, 

Public Law 92–500, 86 Stat. 816, as amended, 

(33 U.S.C. 1251 et seq.) (Clean Water Act or 

CWA) ‘‘to restore and maintain the chemical, 

physical, and biological integrity of the 

Nation’s waters.’’ 33 U.S.C. 1251(a).9 The 

U.S. Supreme Court first addressed the scope 

of ‘‘waters of the United States’’ protected by 

the CWA in United States v. Riverside 

Bayview Homes, 474 U.S. 121 (1985), which 

involved wetlands adjacent to a traditional 

navigable water in Michigan. In a unanimous 

opinion, the Court deferred to the Corps’ 

ecological judgment that adjacent wetlands 

are ‘‘inseparably bound up’’ with the waters 

to which they are adjacent, and upheld the 

inclusion of adjacent wetlands in the 

regulatory definition of ‘‘waters of the United 

States.’’ Id. at 134. The Court observed that 

the broad objective of the CWA to restore and 

maintain the integrity of the Nation’s waters 

‘‘incorporated a broad, systemic view of the 

goal of maintaining and improving water 

quality. . . . Protection of aquatic 

ecosystems, Congress recognized, demanded 

broad federal authority to control pollution, 

for ‘[w]ater moves in hydrologic cycles and 

it is essential that discharge of pollutants be 

controlled at the source.’ In keeping with 

these views, Congress chose to define the 

waters covered by the Act broadly.’’ Id. at 

132–33 (citing Senate Report 92–414). 

The issue of CWA jurisdiction over ‘‘waters 

of the United States’’ was addressed again by 

the Supreme Court in Solid Waste Agency of 

Northern Cook County v. U.S. Army Corps of 

Engineers, 531 U.S. 159 (2001) (SWANCC). In 

SWANCC, the Court (in a 5–4 opinion) held 

that the use of ‘‘isolated’’ nonnavigable 

intrastate ponds by migratory birds was not 

by itself a sufficient basis for the exercise of 

Federal regulatory authority under the CWA. 

The SWANCC Court noted that in Riverside 

it had ‘‘found that Congress’ concern for the 

protection of water quality and aquatic 

ecosystems indicated its intent to regulate 

wetlands ‘inseparably bound up’ with the 

‘waters of the United States’ ’’ and that ‘‘it 

was the significant nexus between the 

wetlands and ‘navigable waters’ that 

informed our reading of the CWA’’ in that 

case. Id. at 167. SWANCC did not invalidate 

(a)(3) or other parts of the regulatory 

definition of ‘‘waters of the United States.’’ 

Five years after SWANCC, the Court again 

addressed the CWA term ‘‘waters of the 

United States’’ in Rapanos v. United States, 

547 U.S. 715 (2006). Rapanos involved two 

consolidated cases in which the CWA had 

been applied to wetlands adjacent to 

nonnavigable tributaries of traditional 

navigable waters. All Members of the Court 

agreed that the term ‘‘waters of the United 

States’’ encompasses some waters that are not 

navigable in the traditional sense. A fourJustice plurality in Rapanos interpreted the 

term ‘‘waters of the United States’’ as 

covering ‘‘relatively permanent, standing or 

continuously flowing bodies of water . . . ,’’ 

id. at 739, that are connected to traditional 

navigable waters, id. at 742, as well as 

wetlands with a ‘‘continuous surface 

connection . . .’’ to such water bodies, id. 

(Scalia, J., plurality opinion). The Rapanos 

plurality noted that its reference to 

‘‘relatively permanent’’ waters did ‘‘not 

necessarily exclude streams, rivers, or lakes 

that might dry up in extraordinary 

circumstances, such as drought,’’ or 

‘‘seasonal rivers, which contain continuous 

flow during some months of the year but no 

flow during dry months . . . .’’ Id. at 732 n.5 

(emphasis in original). Justice Kennedy’s 

concurring opinion took a different approach. 

Justice Kennedy concluded that ‘‘to 

constitute ‘navigable waters’ under the Act, 

a water or wetland must possess a ‘significant 

nexus’ to waters that are or were navigable 

in fact or that could reasonably be so made.’’ 

Id. at 759 (citing SWANCC, 531 U.S. at 167, 

172). He concluded that wetlands possess the 

requisite significant nexus if the wetlands 

‘‘either alone or in combination with 

similarly situated [wet]lands in the region, 

significantly affect the chemical, physical, 

and biological integrity of other covered 

waters more readily understood as 

‘navigable.’ ’’ 547 U.S. at 780. Justice 

Kennedy’s opinion notes that such a 

relationship with navigable waters must be 

more than ‘‘speculative or insubstantial.’’ Id. 

at 780. In Rapanos, the four dissenting 

Justices, who would have affirmed the court 

of appeals’ application of the pertinent 

regulatory provisions, concluded that the 

term ‘‘waters of the United States’’ 

encompasses, inter alia, all tributaries and 

wetlands that satisfy either the plurality’s 

standard or that of Justice Kennedy. Id. at 810 

& n.14 (Stevens, J., dissenting). Neither the 

plurality nor the Kennedy opinions 

invalidated any of the regulatory provisions 

defining ‘‘waters of the United States.’’ 

The Circuit Courts of Appeals are not 

uniform as to the controlling standard for 

‘‘waters of the United States’’ under Rapanos. 

The First, Third and Eighth Circuits have 

concluded that CWA jurisdiction exists if 

either Justice Kennedy’s standard or the 

plurality’s standard is met. United States v. 

Johnson, 467 F.3d 56, 66 (1st Cir. 2006), cert. 

denied, 552 U.S. 948 (2007); U.S. v. Donovan, 

661 F.3d. 174, 176 (3rd Cir. 2011), cert. 

denied, 132 S.Ct. 2409 (2012); U.S. v. Bailey, 

571 F.3d 791, 798–99 (8th Cir. 2009). The 

Seventh and Ninth Circuits limited their 

holdings that the Kennedy standard applied 

to the facts of the cases before them, and did 

not foreclose the possibility that in some 

cases the plurality’s standard might apply. N. 

Cal. River Watch v. City of Healdsburg, 496 

F.3d 993, 999–1000 (9th Cir. 2007), cert. 

denied, 552 U.S. 1180 (2008); United States 

v. Gerke Excavating, Inc., 464 F.3d 723, 725 

(7th Cir. 2006), cert. denied, 552 U.S. 810 

(2007). The Fifth and Sixth Circuits did not 

choose a controlling standard because the 

waters at issue satisfied both standards. 

United States v. Lucas, 516 F.3d 316, 326– 

27 (5th Cir. 2008), cert. denied, 555 U.S. 822 

(2008); United States v. Cundiff, 555 F.3d 

200, 210–13 (6th Cir. 2009), cert. denied, 558 

U.S. 818 (2009). The Eleventh Circuit has 

held that only the Kennedy standard 

determines jurisdiction. United States v. 

Robison, 505 F.3d 1208 (11th Cir. 2007), cert. 

denied sub nom United States v. McWane 

and McWane v. United States, 555 U.S. 1045 

(2008). No Circuit Court has held that only 

the plurality standard applies. 

Traditional Navigable Waters 

EPA and the Corps are proposing no 

changes to the existing regulation related to 

traditional navigable waters and at paragraph 

(a)(1) will continue to assert jurisdiction over 

all waters which are currently used, or were 

used in the past, or may be susceptible to use 

in interstate or foreign commerce, including 

all waters which are subject to the ebb and 

flow of the tide. See e.g., 33 CFR 328.3(a)(1); 

40 CFR 230.3(s)(1); 40 CFR 122.2 (‘‘waters of 

the U.S.’’)). These ‘‘(a)(1) waters’’ are the 

‘‘traditional navigable waters.’’ These (a)(1) 

waters include all of the waters defined in 33 

CFR part 329, which implements sections 9 

and 10 of the Rivers and Harbors Act, and by 

numerous decisions of the Federal courts, 

plus all other waters that are navigable-infact (e.g., the Great Salt Lake, UT and Lake 

Minnetonka, MN). 

To determine whether a water body 

constitutes an (a)(1) water under the 

regulations, relevant considerations include 

Corps regulations, prior determinations by 

the Corps and by the Federal courts, and case 

law. Corps districts and EPA regions would 

determine whether a particular water body is 

a traditional navigable water based on 

application of those considerations to the 

specific facts in each case. 

As noted above, the (a)(1) waters include, 

but are not limited to, waters that meet any 

of the tests set forth in 33 CFR part 329 (e.g., 

the water body is (a) subject to the ebb and 

flow of the tide, and/or (b) the water body is 

presently used, or has been used in the past, 

or may be susceptible for use (with or 

without reasonable improvements) to 

transport interstate or foreign commerce). 

The Corps districts have made 

determinations in the past under these 

regulations for purposes of asserting 

jurisdiction under sections 9 and 10 of the 

Rivers and Harbors Act of 1899 (33 U.S.C. 

401 and 403). Pursuant to 33 CFR 329.16, the 

Corps maintains lists of final determinations 

of navigability for purposes of Corps 

jurisdiction under the Rivers and Harbors Act 

of 1899. While absence from the list should 

not be taken as an indication that the water 

is not navigable (§ 329.16(b)), Corps districts 

and EPA Regions rely on any final Corps 


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determination that a water body meets any of 

the tests set forth in part 329. 

If the Federal courts have determined that 

a water body is navigable-in-fact under 

Federal law for any purpose, that water body 

qualifies as a ‘‘traditional navigable water’’ 

subject to CWA jurisdiction under 33 CFR 

328.3(a)(1) and 40 CFR 230.3(s)(1). Corps 

districts and EPA regions are guided by the 

relevant opinions of the Federal courts in 

determining whether such water bodies are 

‘‘currently used, or were used in the past, or 

may be susceptible to use in interstate or 

foreign commerce’’ (33 CFR 328.3(a)(1); 40 

CFR 230.3(s)(1)) or ‘‘navigable-in-fact.’’ 

The definition of ‘‘navigable-in-fact’’ 

derives from a long line of cases originating 

with The Daniel Ball, 77 U.S. 557 (1870). The 

Supreme Court stated: 

Those rivers must be regarded as public 

navigable rivers in law which are navigable 

in fact. And they are navigable in fact when 

they are used, or are susceptible of being 

used, in their ordinary condition, as 

highways for commerce, over which trade 

and travel are or may be conducted in the 

customary modes of trade and travel on 

water. 

The Daniel Ball, 77 U.S. at 563. 

In The Montello, the Supreme Court 

clarified that ‘‘customary modes of trade and 

travel on water’’ encompasses more than just 

navigation by larger vessels: 

The capability of use by the public for 

purposes of transportation and commerce 

affords the true criterion of the navigability 

of a river, rather than the extent and manner 

of that use. If it be capable in its natural state 

of being used for purposes of commerce, no 

matter in what mode the commerce may be 

conducted, it is navigable in fact, and 

becomes in law a public river or highway. 

The Montello, 87 U.S. 430, 441–42 (1874). In 

that case, the Court held that early fur trading 

using canoes sufficiently showed that the Fox 

River was a navigable water of the United 

States. The Court was careful to note that the 

bare fact of a water’s capacity for navigation 

alone is not sufficient; that capacity must be 

indicative of the water’s being ‘‘generally and 

commonly useful to some purpose of trade or 

agriculture.’’ Id. at 442. 

In Economy Light & Power, the Supreme 

Court held that a waterway need not be 

continuously navigable; it is navigable even 

if it has ‘‘occasional natural obstructions or 

portages’’ and even if it is not navigable ‘‘at 

all seasons . . . or at all stages of the water.’’ 

Economy Light & Power Co. v. U.S., 256 U.S. 

113, 122 (1921). 

In United States v. Holt State Bank, 270 

U.S. 49 (1926), the Supreme Court 

summarized the law on navigability as of 

1926 as follows: 

The rule long since approved by this court 

in applying the Constitution and laws of the 

United States is that streams or lakes which 

are navigable in fact must be regarded as 

navigable in law; that they are navigable in 

fact when they are used, or are susceptible 

of being used, in their natural and ordinary 

condition, as highways for commerce, over 

which trade and travel are or may be 

conducted in the customary modes of trade 

and travel on water; and further that 

navigability does not depend on the 

particular mode in which such use is or may 

be had—whether by steamboats, sailing 

vessels or flatboats—nor on an absence of 

occasional difficulties in navigation, but on 

the fact, if it be a fact, that the stream in its 

natural and ordinary condition affords a 

channel for useful commerce. 

Holt State Bank, 270 U.S. at 56. 

In U.S. v. Utah, 283 U.S. 64 (1931) and 

U.S. v. Appalachian Elec. Power Co, 311 U.S. 

377 (1940), the Supreme Court held that so 

long as a water is susceptible to use as a 

highway of commerce, it is navigable-in-fact, 

even if the water has never been used for any 

commercial purpose. U.S. v. Utah, at 81–83 

(‘‘The question of that susceptibility in the 

ordinary condition of the rivers, rather than 

of the mere manner or extent of actual use, 

is the crucial question.’’); U.S. v. 

Appalachian Elec. Power Co., 311 U.S. at 416 

(‘‘Nor is lack of commercial traffic a bar to 

a conclusion of navigability where personal 

or private use by boats demonstrates the 

availability of the stream for the simpler 

types of commercial navigation.’’) 

Appalachian Power further held that a water 

is navigable-in-fact even if it is not navigable 

and never has been but may become so by 

reasonable improvements. 311 U.S. at 407– 

08. 

In 1971, in Utah v. United States, 403 U.S. 

9 (1971), the Supreme Court held that the 

Great Salt Lake, an intrastate water body, was 

navigable under Federal law even though it 

‘‘is not part of a navigable interstate or 

international commercial highway.’’ Id. at 10. 

In doing so, the Supreme Court stated that 

the fact that the Lake was used for hauling 

of animals by ranchers rather than for the 

transportation of ‘‘water-borne freight’’ was 

an ‘‘irrelevant detail.’’ Id. at 11. ‘‘The lake 

was used as a highway and that is the gist 

of the federal test.’’ Id. 

Most recently, the Supreme Court 

explained: 

The Daniel Ball formulation has been 

invoked in considering the navigability of 

waters for purposes of assessing federal 

regulatory authority under the Constitution, 

and the application of specific federal 

statutes, as to the waters and their beds. See, 

e.g., ibid.; The Montello, 20 Wall. 430, 439, 

22 L.Ed. 391 (1874); United States v. 

Appalachian Elec. Power Co., 311 U.S. 377, 

406, and n. 21, 61 S.Ct. 291, 85 L.Ed. 243 

(1940) (Federal Power Act); Rapanos v. 

United States, 547 U.S. 715, 730–731, 126 

S.Ct. 2208, 165 L.Ed.2d 159 (2006) (plurality 

opinion) (Clean Water Act); id., at 761, 126 

S.Ct. 2208 (KENNEDY, J., concurring in 

judgment) (same). It has been used as well to 

determine questions of title to water beds 

under the equal-footing doctrine. See Utah, 

supra, at 76, 51 S.Ct. 438; Oklahoma v. 

Texas, 258 U.S. 574, 586, 42 S.Ct. 406, 66 

L.Ed. 771 (1922); Holt State Bank, supra, at 

56, 46 S.Ct. 197. It should be noted, however, 

that the test for navigability is not applied in 

the same way in these distinct types of cases. 

Among the differences in application are the 

following. For state title under the equalfooting doctrine, navigability is determined 

at the time of statehood, see Utah, supra, at 

75, 51 S.Ct. 438, and based on the ‘‘natural 

and ordinary condition’’ of the water, see 

Oklahoma, supra, at 591, 42 S.Ct. 406. In 

contrast, admiralty jurisdiction extends to 

water routes made navigable even if not 

formerly so, see, e.g., Ex parte Boyer, 109 

U.S. 629, 631–632, 3 S.Ct. 434, 27 L.Ed. 1056 

(1884) (artificial canal); and federal 

regulatory authority encompasses waters that 

only recently have become navigable, see, 

e.g., Philadelphia Co. v. Stimson, 223 U.S. 

605, 634–635, 32 S.Ct. 340, 56 L.Ed. 570 

(1912), were once navigable but are no 

longer, see Economy Light & Power Co. v. 

United States, 256 U.S. 113, 123–124, 41 

S.Ct. 409, 65 L.Ed. 847 (1921), or are not 

navigable and never have been but may 

become so by reasonable improvements, see 

Appalachian Elec. Power Co., supra, at 407– 

408, 61 S.Ct. 291. With respect to the federal 

commerce power, the inquiry regarding 

navigation historically focused on interstate 

commerce. See The Daniel Ball, 1229*1229 

supra, at 564. And, of course, the commerce 

power extends beyond navigation. See Kaiser 

Aetna v. United States, 444 U.S. 164, 173– 

174, 100 S.Ct. 383, 62 L.Ed.2d 332 (1979). In 

contrast, for title purposes, the inquiry 

depends only on navigation and not on 

interstate travel. See Utah, supra, at 76, 51 

S.Ct. 438. This list of differences is not 

exhaustive. Indeed, ‘‘[e]ach application of 

[the Daniel Ball] test . . . is apt to uncover 

variations and refinements which require 

further elaboration.’’ Appalachian Elec. 

Power Co., supra, at 406, 61 S.Ct. 291. 

PPL Montana v. Montana, 565 U.S. 

___(2012). 

Also of note are two decisions from the 

courts of appeals. In FPL Energy Marine 

Hydro, a case involving the Federal Power 

Act, the D.C. Circuit reiterated the fact that 

‘‘actual use is not necessary for a navigability 

determination’’ and repeated earlier Supreme 

Court holdings that navigability and capacity 

of a water to carry commerce could be shown 

through ‘‘physical characteristics and 

experimentation.’’ FPL Energy Marine Hydro 

LLC v. FERC, 287 F.3d 1151, 1157 (D.C. Cir. 

2002). In that case, the D.C. Circuit upheld 

a FERC navigability determination that was 

based upon three experimental canoe trips 

taken specifically to demonstrate the river’s 

navigability. Id. at 1158–59. 

The 9th Circuit has also implemented the 

Supreme Court’s holding that a water need 

only be susceptible to being used for 

waterborne commerce to be navigable-in-fact. 

Alaska v. Ahtna, Inc., 891 F.2d 1404 (9th Cir. 

1989). In Ahtna, the 9th Circuit held that 

current use of an Alaskan river for 

commercial recreational boating was 

sufficient evidence of the water’s capacity to 

carry waterborne commerce at the time that 

Alaska became a state. Id. at 1405. It was 

found to be irrelevant whether or not the 

river was actually being navigated or being 

used for commerce at the time, because 

current navigation showed that the river 

always had the capacity to support such 

navigation. Id. at 1404. 

In summary, when determining whether a 

water body qualifies as a ‘‘traditional 

navigable water’’ (i.e., an (a)(1) water), 

relevant considerations include whether the 

water body meets any of the tests set forth 

in Part 329, or a Federal court has 

determined that the water body is 


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10For purposes of the CWA, EPA and the Corps 

have interpreted the term ‘‘traditional navigable 

waters’’ to include all of the ‘‘navigable waters of 

the United States,’’ defined in 33 CFR part 329 and 

by numerous decisions of the Federal courts, plus 

all other waters that are navigable-in-fact (e.g., the 

Great Salt Lake, UT and Lake Minnetonka, MN). 

This section explains why EPA and the Corps do 

not interpret the CWA or the Supreme Court’s 

decisions in Solid Waste Agency of Northern Cook 

County (SWANCC) v. U.S. Army Corps of Engineers, 

531 U.S. 159 (2001) and Rapanos v. United States, 

547 U.S. 715 (2006), to restrict CWA jurisdiction 

over interstate waters to only those interstate waters 

that are traditional navigable waters or that connect 

to traditional navigable waters. 

11The Supreme Court has found that the term 

‘‘waters of the United States’’ is ambiguous in some 

respects. Rapanos, 547 U.S. at 752 (plurality 

opinion), 804 (dissent). 

12Section 303 of the Act requires the states to 

submit revised and new water quality standards to 

the Administrator for review. CWA section 

303(c)(2)(A). Such revised or new water quality 

standards ‘‘shall consist of the designated uses of 

the navigable waters involved and the water quality 

criteria for such waters.’’ Id. If the Administrator 

determines that a revised or new standard is not 

consistent with the Act’s requirements, or 

determines that a revised or new standard is 

necessary to meet the Act’s requirements, and the 

state does not make required changes, ‘‘[t]he 

Administrator shall promptly prepare and publish 

proposed regulations setting forth a revised or new 

water quality standard for the navigable waters 

involved.’’ CWA section 303(c)(4). 

‘‘navigable-in-fact’’ under Federal law for any 

purpose, or the water body is ‘‘navigable-infact’’ under the standards that have been 

used by the Federal courts. 

Interstate Waters 

1. Interstate Waters 

The agencies’ proposal today makes no 

change to the interstate waters section of the 

existing regulations and the agencies would 

continue to assert jurisdiction over interstate 

waters, including interstate wetlands. The 

language of the CWA is clear that Congress 

intended the term ‘‘navigable waters’’ to 

include interstate waters, and the agencies’ 

interpretation, promulgated 

contemporaneously with the passage of the 

CWA, is consistent with the statute and 

legislative history. The Supreme Court’s 

decisions in SWANCC and Rapanos did not 

address the interstate waters provision of the 

existing regulation. 

A. The Language of the Clean Water Act, the 

Statute as a Whole, and the Statutory History 

Demonstrate Congress’ Clear Intent To 

Include Interstate Waters as ‘‘Navigable 

Waters’’ Subject to the Clean Water Act 

While as a general matter, the scope of the 

terms ‘‘navigable waters’’ and ‘‘waters of the 

United States’’ is ambiguous, the language of 

the CWA, particularly when read as a whole, 

demonstrates that Congress clearly intended 

to continue to subject interstate waters to 

Federal regulation. The statutory history of 

Federal water pollution control places the 

terms of the CWA in context and provides 

further evidence of Congressional intent to 

include interstate waters within the scope of 

the ‘‘navigable waters’’ protected by the Act. 

Congress clearly intended to subject 

interstate waters to CWA jurisdiction without 

imposing a requirement that they be water 

that is navigable for purposes of Federal 

regulation under the Commerce Clause 

themselves or be connected to water that is 

navigable for purposes of Federal regulation 

under the Commerce Clause.10 The CWA 

itself is clear that interstate waters that were 

previously subject to Federal regulation 

remain subject to Federal regulation. The text 

of the CWA, specifically the CWA’s provision 

with respect to interstate waters and their 

water quality standards, in conjunction with 

the definition of navigable waters, provides 

clear indication of Congress’ intent. Thus, 

interstate waters are ‘‘navigable waters’’ 

protected by the CWA. 

(1) The Plain Language of the Clean Water 

Act and the Statute as a Whole Clearly 

Indicate Congress’ Intent to Include Interstate 

Waters Within the Scope of ‘‘Navigable 

Waters’’ for Purposes of the Clean Water Act 

Under well settled principles, the phrase 

‘‘navigable waters’’ should not be read in 

isolation from the remainder of the statute. 

As the Supreme Court has explained: 

The definition of words in isolation, 

however, is not necessarily controlling in 

statutory construction. A word in a statute 

may or may not extend to the outer limits of 

its definitional possibilities. Interpretation of 

a word or phrase depends upon reading the 

whole statutory text, considering the purpose 

and context of the statute, and consulting any 

precedents or authorities that inform the 

analysis. 

Dolan v. U.S. Postal Service, 546 U.S. 481, 

486 (2006); see also United States Nat’l. Bank 

of Oregon v. Indep. Ins. Agents of Am., Inc., 

508 U.S. 439, 455 (1993). 

While the term ‘‘navigable waters’’ is, in 

general, ambiguous, interstate waters are 

waters that are clearly covered by the plain 

language of the definition of ‘‘navigable 

waters.’’ 11 Congress defined ‘‘navigable 

waters’’ to mean ‘‘the waters of the United 

States, including the territorial seas.’’ 

Interstate waters are waters of the several 

States and, thus, the United States. While the 

1972 Act was clearly not limited to interstate 

waters, it was clearly intended to include 

interstate waters. 

Furthermore, the CWA does not simply 

define ‘‘navigable waters.’’ Other provisions 

of the statute provide additional textual 

evidence of the scope of this term of the Act. 

Most importantly, there is a specific 

provision in the 1972 CWA establishing 

requirements for those interstate waters 

which were subject to the prior Water 

Pollution Control Acts. 

The CWA requires states to establish water 

quality standards for navigable waters and 

submit them to the Administrator for 

review.12 Under section 303(a) of the Act, in 

order to carry out the purpose of this Act, any 

water quality standard applicable to 

interstate waters which was adopted by any 

State and submitted to, and approved by, or 

is awaiting approval by, the Administrator 

pursuant to this Act as in effect immediately 

prior to the date of enactment of the Federal 

Water Pollution Control Act Amendments of 

1972, shall remain in effect unless the 

Administrator determined that such standard 

is not consistent with the applicable 

requirements of the Act as in effect 

immediately prior to the date of enactment of 

the Federal Water Pollution Control Act 

Amendments of 1972. If the Administrator 

makes such a determination he shall, within 

three months after the date of enactment of 

the Federal Water Pollution Control Act 

Amendments of 1972, notify the State and 

specify the changes needed to meet such 

requirements. If such changes are not 

adopted by the State within ninety days after 

the date of such notification, the 

Administrator shall promulgate such changes 

in accordance with subsection (b). CWA 

section 303(a)(1) (emphasis added). 

Under the 1965 Act, as discussed in more 

detail below, states were directed to develop 

water quality standards establishing water 

quality goals for interstate waters. By the 

early 1970s, all the states had adopted such 

water quality standards. Advanced Notice of 

Proposed Rulemaking, Water Quality 

Standards Regulation, 63 FR 36742, 36745, 

July 7, 1998. In section 303(a), Congress 

clearly intended for existing Federal 

regulation of interstate waters to continue 

under the amended CWA. Water quality 

standards for interstate waters were not 

merely to remain in effect, but EPA was 

required to actively assess those water 

quality standards and even promulgate 

revised standards for interstate waters if 

states did not make necessary changes. By 

the plain language of the statute, these water 

quality standards for interstate waters were to 

remain in effect ‘‘in order to carry out the 

purpose of this Act.’’ The objective of the Act 

is ‘‘to restore and maintain the chemical, 

physical, and biological integrity of the 

Nation’s waters.’’ CWA section 101(a). It 

would contravene Congress’ clearly stated 

intent for a court to impose an additional 

jurisdictional requirement on all rivers, lakes, 

and other waters that flow across, or form a 

part of, state boundaries (‘‘interstate waters’’ 

as defined by the 1948 Act, § 10, 62 Stat. 

1161), such that interstate waters that were 

previously protected were no longer 

protected because they lacked a connection 

to a water that is navigable for purposes of 

Federal regulation under the Commerce 

Clause. Nor would all the existing water 

quality standards be ‘‘carry[ing] out the 

purpose of this Act,’’ if the only water quality 

standards that could be implemented through 

the Act (through, for example, National 

Pollutant Discharge Elimination System 

permits under section 402) were those water 

quality standards established for interstate 

waters that are also waters that are navigable 

for purposes of Federal regulation under the 

Commerce Clause or that connect to waters 

that are navigable for purposes of Federal 

regulation under the Commerce Clause. 

Nowhere in section 303(a) does Congress 

make such a distinction. 

(2) The Federal Water Pollution Control 

Statute That Became the Clean Water Act 

Covered Interstate Waters 

In 1972, when Congress rewrote the law 

governing water pollution, two Federal 

statutes addressed discharges of pollutants 

into interstate waters and water that is 


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13Congress did not define the term ‘‘navigable 

waters’’ in the 1961 Amendments, or in subsequent 

FWPCA Amendments, until 1972. 

14 In 1967, the state of Arizona created the Water 

Quality Control Council (Council) to implement the 

requirements of the 1965 FWPCA. The Council 

adopted water quality standards for those waters 

that were considered ‘‘interstate waters’’ pursuant 

to the existing Federal law. The Council identified 

the Santa Cruz River as an interstate water and 

promulgated water quality standards for the river in 

accordance with Federal law. 

15The 1966 Amendments authorized civil fines 

for failing to provide information about an alleged 

discharge causing or contributing to water 

pollution. Public Law 89–753, 80 Stat. 1250 (1966); 

see also S. Rep. No. 414, 92d Congress, 1st Sess. 10 

(1972) (describing the history of the FWPCA). 

16 In December 1970, administration of the 

Federal Water Pollution Control Administration 

was transferred from the Secretary of the Interior to 

EPA. S. Rep. No. 414, 92d Congress, 1st Sess. 

(1972). 

navigable for purposes of Federal regulation 

under the Commerce Clause, and tributaries 

of each: The Water Pollution Control Act of 

1948, as amended, and section 13 of the 

Rivers and Harbors Act of 1899 (known as 

the ‘‘Refuse Act’’). Of the two, the Water 

Pollution Control Act extended Federal 

authority over interstate waters and their 

tributaries. In contrast, the Refuse Act 

extended Federal jurisdiction over the 

‘‘navigable waters of the United States’’ and 

their tributaries. These two separate statutes 

demonstrate that Congress recognized that 

interstate waters and ‘‘navigable waters of the 

United States’’ were independent lawful 

bases of Federal jurisdiction. 

a. The Federal Water Pollution Control Act 

Prior to 1972 

From the outset, and through all the 

amendments pre-dating the 1972 

Amendments, the Federal authority to abate 

water pollution under the Water Pollution 

Control Act, and the Federal Water Pollution 

Control Act (FWPCA) as it was renamed in 

1956, extended to interstate waters. In 

addition, since first enacted in 1948, and 

throughout all the amendments, the goals of 

the Act have been, inter alia, to protect 

public water supplies, propagation of fish 

and aquatic life, recreation, agricultural, 

industrial, and other legitimate uses. See 62 

Stat. 1155 and 33 U.S.C. 466 (1952), 33 

U.S.C. 466 (1958), 33 U.S.C. 466 (1964), 33 

U.S.C. 1151 (1970). 

In 1948, Congress enacted the Water 

Pollution Control Act in connection with the 

exercise of jurisdiction over the waterways of 

the Nation and in the consequence of the 

benefits to public health and welfare by the 

abatement of stream pollution. See Pub. L. 

No. 80–845, 62 Stat. 1155 (June 30, 1948). 

The Act authorized technical assistance and 

financial aid to states for stream pollution 

abatement programs, and made discharges of 

pollutants into interstate waters and their 

tributaries a nuisance, subject to abatement 

and prosecution by the United States. See 

section 2(d)(1),(4), 62 Stat. at 1156–1157 

(section 2(d)(1) of the Water Pollution 

Control Act of 1948, 62 Stat. at 1156, stated 

that the ‘‘pollution of interstate waters’’ in or 

adjacent to any State or States (whether the 

matter causing or contributing to such 

pollution is discharged directly into such 

waters or reaches such waters after discharge 

into a tributary of such waters), which 

endangers the health or welfare of persons in 

a State other than that in which the discharge 

originates, is declared to be a public nuisance 

and subject to abatement as provided by the 

Act. (emphasis added)); § 2(a), 62 Stat. 1155 

(requiring comprehensive programs for 

‘‘interstate waters and tributaries thereof’’); 

§ 5, 62 Stat. 1158 (authorizing loans for 

sewage treatment to abate discharges into 

‘‘interstate waters or into a tributary of such 

waters’’). Under the statute, ‘‘interstate 

waters’’ were defined as all rivers, lakes, and 

other waters that flow across, or form a part 

of, state boundaries. Section 10, 62 Stat. 

1161. 

In 1956, Congress strengthened measures 

for controlling pollution of interstate waters 

and their tributaries. Public Law 84–660, 70 

Stat. 498 (1956) (directing further 

cooperation between the Federal and State 

Governments in development of 

comprehensive programs for eliminating or 

reducing ‘‘the pollution of interstate waters 

and tributaries’’ and improving the sanitary 

condition of surface and underground waters, 

and authorizing the Surgeon General to make 

joint investigations with States into the 

conditions of and discharges into ‘‘any 

waters of any State or States.’’). 

In 1961, Congress amended the FWPCA to 

substitute the term ‘‘interstate or navigable 

waters’’ for ‘‘interstate waters.’’ See Public 

Law 87–88, 75 Stat. 208 (1961). Accordingly, 

beginning in 1961, the provisions of the 

FWPCA applied to all interstate waters and 

navigable waters and the tributaries of each, 

see 33 U.S.C. 466a, 466g(a) (1964).13

In 1965, Congress approved a second set of 

major legislative changes, requiring each 

state to develop water quality standards for 

interstate waters within its boundaries by 

1967. Public Law 89–234, 79 Stat. 908 

(1965).14 Failing establishment of adequate 

standards by the state, the Act authorized 

establishment of water quality standards by 

Federal regulation. Id. at 908. The 1965 

Amendments provided that the discharge of 

matter ‘‘into such interstate waters or 

portions thereof,’’ which reduces the quality 

of such waters below the water quality 

standards established under this subsection 

(whether the matter causing or contributing 

to such reduction is discharged directly into 

such waters or reaches such waters after 

discharge into tributaries of such waters), is 

subject to abatement through procedures 

specified in the Act, including (after 

conferences and negotiations and 

consideration by a Hearing Board) legal 

action in the courts. Id. at 909.15

b. The Refuse Act 

Since its original enactment in 1899, the 

Refuse Act has prohibited the discharge of 

refuse matter ‘‘into any navigable water of the 

United States, or into any tributary of any 

navigable water.’’ Ch. 425, 30 Stat. 1152 

(1899). It also has prohibited the discharge of 

such material on the bank of any tributary 

where it is liable to be washed into a 

navigable water. Id. Violators are subject to 

fines and imprisonment. Id. at 1153 (codified 

at 33 U.S.C. 412). In 1966, the Supreme Court 

upheld the Corps’ interpretation of the 

Refuse Act as prohibiting discharges that 

pollute the navigable waters, and not just 

those discharges that obstruct navigation. 

United States v. Standard Oil Co., 384 U.S. 

224, 230 (1966). In 1970, President Nixon 

signed an Executive Order directing the 

Corps (in consultation with the Federal 

Water Pollution Control Administration 16) to 

implement a permit program under section 

13 of the RHA ‘‘to regulate the discharge of 

pollutants and other refuse matter into the 

navigable waters of the United States or their 

tributaries and the placing of such matter 

upon their banks.’’ E.O. 11574, 35 FR 19627, 

Dec. 25, 1970. In 1971, the Corps 

promulgated regulations establishing the 

Refuse Act Permit Program. 36 FR 6564, 

6565, April 7, 1971. The regulations made it 

unlawful to discharge any pollutant (except 

those flowing from streets and sewers in a 

liquid state) into a navigable waterway or 

tributary, except pursuant to a permit. Under 

the permit program, EPA advised the Corps 

regarding the consistency of a proposed 

discharge with water quality standards and 

considerations, and the Corps evaluated a 

permit application for impacts on anchorage, 

navigation, and fish and wildlife resources. 

Id. at 6566. 

c. The Federal Water Pollution Control Act 

Amendments of 1972 

When Congress passed the Federal Water 

Pollution Control Act Amendments of 1972 

(referred to hereinafter as the CWA or CWA), 

it was not acting on a blank slate. It was 

amending existing law that provided for a 

Federal/State program to address water 

pollution. The Supreme Court has recognized 

that Congress, in enacting the CWA in 1972, 

‘‘intended to repudiate limits that had been 

placed on federal regulation by earlier water 

pollution control statutes and to exercise its 

powers under the Commerce Clause to 

regulate at least some waters that would not 

be deemed ‘navigable’ under the classical 

understanding of that term.’’ Riverside 

Bayview Homes, 474 U.S. at 133; see also 

International Paper Co. v. Ouellette, 479 U.S. 

481, 486, n.6 (1987). 

The amendments of 1972 defined the term 

‘‘navigable waters’’ to mean ‘‘the waters of 

the United States, including the territorial 

seas.’’ 33 U.S.C. 1362(7). While earlier 

versions of the 1972 legislation defined the 

term to mean ‘‘the navigable waters of the 

United States,’’ the Conference Committee 

deleted the word ‘‘navigable’’ and expressed 

the intent to reject prior geographic limits on 

the scope of Federal water-protection 

measures. Compare S. Conf. Rep. No. 1236, 

92d Cong., 2d Sess. 144 (1972), with H.R. 

Rep. No. 911, 92 Cong., 2d Sess. 356 (1972) 

(bill reported by the House Committee 

provided that ‘‘[t]he term ‘navigable waters’ 

means the navigable waters of the United 

States, including the territorial seas’’); see 

also S. Rep. No. 414, 92d Cong., 1st Sess. 77 

(‘‘Through a narrow interpretation of the 

definition of interstate waters the 

implementation of the 1965 Act was severely 

limited. . . . Therefore, reference to the 

control requirements must be made to the 

navigable waters, portions thereof, and their 

tributaries.’’). Thus, Congress intended the 

scope of the 1972 Act to include, at a 


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minimum, the waters already subject to 

Federal water pollution control law—both 

interstate waters and waters that are 

navigable for purposes of Federal regulation 

under the Commerce Clause. Those statutes 

covered interstate waters, defined interstate 

waters without requiring that they be a 

traditional navigable water or be connected 

to water that is a traditional navigable water, 

and demonstrated that Congress knew that 

there are interstate waters that are not 

navigable for purposes of Federal regulation 

under the Commerce Clause. 

In fact, Congress amended the Federal 

Water Pollution Control Act in 1961 to 

substitute the term ‘‘interstate or navigable 

waters’’ for ‘‘interstate waters,’’ 

demonstrating that Congress wanted to be 

very clear that it was asserting jurisdiction 

over both types of waters: interstate waters 

even if they were not navigable for purposes 

of Federal regulation under the Commerce 

Clause, and traditional navigable waters even 

if they were not interstate waters. At no point 

were the interstate waters already subject to 

Federal water pollution control authority 

required to be navigable or to connect to a 

traditional navigable water. Further, as 

discussed above, the legislative history 

clearly demonstrates that Congress was 

expanding jurisdiction—not narrowing it— 

with the 1972 amendments. Thus, it is 

reasonable to conclude that by defining 

‘‘navigable waters’’ as ‘‘the waters of the 

United States’’ in the 1972 amendments, 

Congress included not just traditionally 

navigable waters, but all waters previously 

regulated under the Federal Water Pollution 

Control Act, including non-navigable 

interstate waters. 

Based on the statutory definition of 

navigable waters, the requirement of section 

303(a) for water quality standards for 

interstate waters to remain in effect, the 

purposes of the Act, and the more than three 

decades of Federal water pollution control 

regulation that provides a context for reading 

those provisions of the statute, the intent of 

Congress is clear that the term ‘‘navigable 

waters’’ includes ‘‘interstate waters’’ as an 

independent basis for CWA jurisdiction, 

whether or not they themselves are 

traditional navigable waters or are connected 

to a traditional navigable water. 

B. Supreme Court Precedent Supports CWA 

Jurisdiction Over Interstate Waters Without 

Respect to Navigability 

In two seminal decisions, the Supreme 

Court established that resolving interstate 

water pollution issues was a matter of 

Federal law and that the CWA was the 

comprehensive regulatory scheme for 

addressing interstate water pollution. Illinois 

v. Milwaukee, 406 U.S. 91 (1972); City of 

Milwaukee v. Illinois, 451 U.S. 304 (1981). In 

both of these decisions, the Court held that 

Federal law applied to interstate waters. 

Moreover, these cases analyzed the 

applicable Federal statutory schemes and 

determined that the provisions of the Federal 

Water Pollution Control Act and the CWA 

regulating water pollution applied generally 

to interstate waters. The holdings of these 

cases recognized the Federal interest in 

interstate water quality pollution; and City of 

Milwaukee recognized that CWA jurisdiction 

extends to interstate waters without regard to 

navigability. 

In Illinois v. Milwaukee, the Court 

considered a public nuisance claim brought 

by the State of Illinois against the city of 

Milwaukee to address the adverse effects of 

Milwaukee’s discharges of poorly treated 

sewage into Lake Michigan, ‘‘a body of 

interstate water.’’ 406 U.S. at 93. In relevant 

part, the Court held that the Federal common 

law of nuisance was an appropriate 

mechanism to resolve disputes involving 

interstate water pollution. 406 U.S. at 107 

(‘‘federal courts will be empowered to 

appraise the equities of suits alleging creation 

of a public nuisance by water pollution’’). 

The Court further noted that in such actions 

the Court could consider a state’s interest in 

protecting its high water quality standards 

from ‘‘the more degrading standards of a 

neighbor.’’ Id. 

In reaching this conclusion, the Court 

examined in detail the scope of the Federal 

regulatory scheme as it existed prior to the 

October, 1972 FWPCA amendments. In its 

April, 1972 decision, the Court concluded 

that the Federal Water Pollution Control Act 

‘‘makes clear that it is federal, not state, law 

that in the end controls the pollution of 

interstate or navigable waters.’’ 406 U.S. at 

102 (emphasis added). The Court, in this 

case, concluded that the regulatory 

provisions of the Federal Water Pollution 

Control Act did not address the right of a 

state to file suit to protect water quality. 

However, this was not because this statute 

did not reach interstate waters. The Court 

specifically noted that section 10(a) of the 

Federal Water Pollution Control Act ‘‘makes 

pollution of interstate or navigable waters 

subject ‘to abatement’ ’’ 406 U.S. at 102 

(emphasis added). Rather, the Court noted 

that the plaintiff in this action was seeking 

relief outside the scope of the Federal Water 

Pollution Control Act and that statute 

explicitly provided that independent ‘‘state 

and interstate action to abate pollution of 

interstate or navigable waters shall be 

encouraged and shall not . . . be displaced 

by Federal enforcement action.’’ 406 U.S. at 

104 (citing section 10(b) of the Federal Water 

Pollution Control Act). 

In addition, in Illinois v. Milwaukee, the 

Court acknowledged that it was essential for 

Federal law to resolve interstate water 

pollution disputes, citing with approval the 

following discussion from Texas v. Pankey: 

Federal common law and not the varying 

common law of the individual states is, we 

think, entitled and necessary to be 

recognized as a basis for dealing in uniform 

standard with the environmental rights of a 

State against improper impairment by 

sources outside its domain. . . . Until the 

field has been made the subject of 

comprehensive legislation or authorized 

administrative standards, only a federal 

common law basis can provide an adequate 

means for dealing with such claims as 

alleged federal rights. 

406 U.S. at 107 n. 9, citing Texas v. Pankey, 

441 F.2d 236, 241–242. 

In City of Milwaukee, the Court revisited 

this dispute and addressed the expanded 

statutory provisions of the CWA regulating 

water pollution. The scope of the CWA 

amendments led the Court to reverse its 

decision in Illinois v. Milwaukee. In reaching 

this result, the Court concluded that Congress 

had elected to exercise its authority under 

Federal law to occupy the field of water 

pollution regulation. As a result, the Court 

concluded that there was no basis for 

maintaining a Federal common law of 

nuisance. 

Congress has not left the formulation of 

appropriate federal standards to the courts 

through application of often vague and 

indeterminate nuisance concepts and 

maxims of equity jurisprudence, but rather 

has occupied the field through the 

establishment of a comprehensive regulatory 

program supervised by an expert 

administrative agency. The 1972 

Amendments to the Federal Water Pollution 

Control Act were not merely another law 

‘‘touching interstate waters’’. . . Rather, the 

Amendments were viewed by Congress as a 

‘‘total restructuring’’ and ‘‘complete 

rewriting’’ of the existing water pollution 

legislation considered in that case. 

451 U.S. at 317. 

The Court’s analysis in Illinois v. 

Milwaukee made clear that Federal common 

law was necessary to protect ‘‘the 

environmental rights of States against 

improper impairment by sources outside its 

domain.’’ 406 U.S. at 107, n. 9. In the context 

of interstate water pollution, nothing in the 

Court’s language or logic limits the reach of 

this conclusion to only navigable interstate 

waters. In City of Milwaukee, the Court found 

that the CWA was the ‘‘comprehensive 

regulatory program’’ that ‘‘occupied the 

field’’ (451 U.S. 317) with regard to interstate 

water pollution, eliminating the basis for an 

independent common law of nuisance to 

address interstate water pollution. Since the 

Federal common law of nuisance (as well as 

the statutory provisions regulating water 

pollution in the Federal Water Pollution 

Control Act) applied to interstate waters 

whether navigable or not, the CWA could 

only occupy the field of interstate water 

pollution if it too extended to non-navigable 

as well as navigable interstate waters. 

With regard to the specifics of interstate 

water pollution, the City of Milwaukee Court 

noted that, in Illinois v. Milwaukee, it had 

been concerned that Illinois did not have a 

forum in which it could protect its interests 

in abating water pollution from out of state, 

absent the recognition of Federal common 

law remedies. 451 U.S. at 325. The Court 

then went on to analyze in detail the specific 

procedures created by the CWA ‘‘for a State 

affected by decisions of a neighboring State’s 

permit-granting agency to seek redress.’’ 451 

U.S. at 326. The Court noted that ‘‘any State 

whose waters may be affected by the issuance 

of a permit’’ is to receive notice and the 

opportunity to comment on the permit. Id. 

(citing to CWA section 402(b)(3)(5). In 

addition the Court noted provisions giving 

EPA the authority to veto and issue its own 

permits ‘‘if a stalemate between an issuing 

and objecting state develops.’’ Id. (citing to 

CWA sections 402(d)(2)(A),(4)). In light of 

these protections for states affected by 

interstate water pollution, the court 

concluded that 


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17Nothing in subsequent Supreme Court case law 

regarding interstate waters in any way conflicts 

with the agencies’ interpretation. See International 

Paper v. Ouellette, 479 U.S. 481 (1987); Arkansas 

v. Oklahoma, 503 U.S. 91 (1992). In both of these 

cases, the Court detailed how the CWA had 

supplanted the Federal common law of nuisance to 

establish the controlling statutory scheme for 

addressing interstate water pollution disputes. 

Nothing in either decision limits the applicability 

of the CWA to interstate water pollution disputes 

involving navigable interstate waters or interstate 

waters connected to navigable waters. 

18 It is worth noting the Justice Rehnquist was 

also the author of City of Milwaukee. 

[t]he statutory scheme established by 

Congress provides a forum for the pursuit of 

such claims before expert agencies by means 

of the permit-granting process. It would be 

quite inconsistent with this scheme if federal 

courts were in effect to ‘‘write their own 

ticket’’ under the guise of federal common 

law after permits have already been issued 

and permittees have been planning and 

operating in reliance on them. 

451 U.S. at 326. 

Nothing in the language or the reasoning of 

this discussion limits the applicability of 

these protections of interstate waters to 

navigable interstate waters or interstate 

waters connected to navigable waters. If these 

protections only applied to navigable 

interstate waters, a downstream state would 

be unable to protect many of its waters from 

out of state water pollution. This would 

hardly constitute a comprehensive regulatory 

scheme that occupied the field of interstate 

water pollution. 

For these reasons, the holdings and the 

reasoning of these decisions establish that the 

regulatory reach of the CWA extends to all 

interstate waters without regard to 

navigability.17

C. The Supreme Court’s Decisions in 

SWANCC and Rapanos Do Not Limit or 

Constrain Clean Water Act Jurisdiction Over 

Non-Navigable Interstate Waters 

As noted above, the Supreme Court 

recognized that Congress, in enacting the 

CWA, ‘‘intended to repudiate limits that had 

been placed on federal regulation by earlier 

water pollution control statutes and to 

exercise its powers under the Commerce 

Clause to regulate at least some waters that 

would not be deemed ‘navigable’ under the 

classical understanding of that term.’’ 

Riverside Bayview, 474 U.S. at 133; see also 

International Paper Co. v. Ouellette, 479 U.S. 

481, 486 n.6, (1987). In Riverside Bayview, 

and subsequently in SWANCC and Rapanos, 

the Court addressed the construction of the 

CWA terms ‘‘navigable waters’’ and ‘‘the 

waters of the United States.’’ In none of these 

cases did the Supreme Court address 

interstate waters, nor did it overrule prior 

Supreme Court precedent which addressed 

the interaction between the CWA and Federal 

common law to address pollution of 

interstate waters. Therefore, the statute, even 

in light of SWANCC and Rapanos, does not 

impose an additional requirement that 

interstate waters must be water that is 

navigable for purposes of Federal regulation 

under the Commerce Clause or connected to 

water that is navigable for purposes of 

Federal regulation under the Commerce 

Clause to be jurisdictional waters for 

purposes of the CWA. 

At the outset, it is worth noting that neither 

SWANCC nor Rapanos dealt with the 

jurisdictional status of interstate waters. 

Repeatedly in the SWANCC decision the 

Court emphasized that the question 

presented concerned the jurisdiction status of 

nonnavigable intrastate waters located in two 

Illinois counties. SWANCC 531 U.S. at 165– 

166, 171 (‘‘we thus decline to . . . hold that 

isolated ponds, some only seasonal, wholly 

located within two Illinois counties fall under 

§ 404(a) definition of navigable waters . . .’’) 

(emphasis added). Nowhere in Justice 

Rehnquist’s majority opinion in SWANCC 

does the Court discuss the Court’s interstate 

water case law.18 The Court does not even 

discuss the fact that CWA jurisdictional 

regulations identify interstate waters as 

regulated ‘‘waters of the United States.’’ In 

fact, the repeated emphasis on the intrastate 

nature of the waters at issue can be read as 

an attempt to distinguish SWANCC from the 

Court’s interstate water jurisprudence. 

In Rapanos, the properties at issue were 

located entirely within the State of Michigan. 

547 U.S. 715, 762–764. Thus, the Court had 

no occasion to address the text of the CWA 

with respect to interstate waters or the 

agencies’ regulatory provisions concerning 

interstate waters. In addition, neither Justice 

Kennedy nor the plurality discusses the 

impact of their opinions on the Court’s 

interstate waters jurisprudence. The plurality 

decision acknowledges that CWA 

jurisdictional regulations include interstate 

waters. 547 U.S. 715, 724. However, the 

plurality did not discuss in any detail its 

views as to the continued vitality of 

regulations concerning such waters. 

Moreover, one of the analytical 

underpinnings of the SWANCC and Rapanos 

decisions is irrelevant to analysis of 

regulations asserting jurisdiction over 

interstate waters. In SWANCC, the Court 

declined to defer to agency regulations 

asserting jurisdiction over isolated waters 

because 

[w]here an administrative interpretation of a 

statute invokes the outer limits of Congress’ 

power, we expect a clear indication that 

Congress intended that result. . . .This 

requirement stems from our prudential desire 

not to needlessly reach constitutional issues 

and our assumption that Congress does not 

casually authorize administrative agencies to 

interpret a statute to push the limit of 

Congressional authority. . . . This concern is 

heightened where the administrative 

interpretation alerts the federal-state 

framework by permitting federal 

encroachment upon a traditional state power. 

531 U.S. at 172–173 (citations omitted). 

However, the Court’s analysis in Illinois v. 

Milwaukee and City of Milwaukee makes 

clear that Congress has broad authority to 

create Federal law to resolve interstate water 

pollution disputes. As discussed above, the 

Court in Illinois v. Milwaukee, invited further 

Federal legislation to address interstate water 

pollution, and in so doing concluded that 

State law was not an appropriate basis for 

addressing interstate water pollution issues. 

406 U.S. at 107 n. 9 (citing Texas v. Pankey, 

441 F.2d 236, 241–242). In City of 

Milwaukee, the Court indicated that central 

to its holding in Illinois v. Milwaukee was its 

concern ‘‘that Illinois did not have any forum 

to protect its interests [in the matters 

involving interstate water pollution].’’ 451 

U.S. 325. As discussed above, the Court cited 

with approval the statutory provisions of the 

CWA regulating water pollution as an 

appropriate means to address that concern. 

The City of Milwaukee and Illinois v. 

Milwaukee decisions make clear that 

assertion of Federal authority to resolve 

disputes involving interstate waters does not 

alter ‘‘the Federal-State framework by 

permitting Federal encroachment on a 

traditional State power.’’ 531 U.S. at 173. 

‘‘Our decisions concerning interstate waters 

contain the same theme. Rights in interstate 

streams, like questions of boundaries, have 

been recognized as presenting Federal 

questions.’’ Illinois v. Milwaukee, 406 U.S. at 

105 (internal quotations and citations 

omitted). 

The Supreme Court’s analysis in SWANCC 

and Rapanos materially altered the criteria 

for analyzing CWA jurisdictional issues for 

wholly intrastate waters. However, these 

decisions by their terms did not affect the 

body of case law developed to address 

interstate waters. The holdings in the 

Supreme Court’s interstate waters 

jurisprudence, in particular City of 

Milwaukee, apply CWA jurisdiction to 

interstate waters without regard to, or 

discussion of, navigability. In City of 

Milwaukee, the Court held that the CWA 

provided a comprehensive statutory scheme 

for addressing the consequences of interstate 

water pollution. Based on this analysis, the 

Court expressly overruled its holding in 

Illinois v. Milwaukee that the Federal 

common law of nuisance would apply to 

resolving interstate water pollution disputes. 

Instead, the Court held that such disputes 

would now be resolved through application 

of the statutory provisions of the CWA 

regulating water pollution. 

It would be unreasonable to interpret 

SWANCC or Rapanos as overruling City of 

Milwaukee with respect to CWA jurisdiction 

over non-navigable interstate waters. Such an 

interpretation would result in no law to 

apply to water pollution disputes with regard 

to such waters, unless one were to assume 

that the Court intended (without discussion 

or analysis) to restore the Federal common 

law of nuisance as the law to apply in such 

matters. Moreover, SWANCC and Rapanos 

acknowledge that CWA regulatory 

jurisdiction extends to at least some nonnavigable waters. See, e.g., 547 U.S. at 779 

(Kennedy, J.). Neither the SWANCC Court 

nor the plurality or Kennedy opinions in 

Rapanos purports to set out the complete 

boundaries of CWA jurisdiction. See, e.g., 

547 U.S. at 731 (‘‘[w]e need not decide the 

precise extent to which the qualifiers 

‘navigable’ and ‘of the United States’ restrict 

the coverage of the Act.’’) (plurality opinion). 

In addition, as the Supreme Court has 

repeatedly admonished, if a Supreme Court 

precedent has direct application in a case yet 

appears to rest on a rationale rejected in some 

other line of decisions, lower courts should 

follow the case which directly controls, 


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19See id. at 9 (‘‘The scope of the 1899 Refuse Act 

is broadened; the administrative capability is 

strengthened.’’); id. at 43 (‘‘Much of the 

Committee’s time devoted to this Act centered on 

an effort to resolve the existing water quality 

program and the separate pollution program 

developing under the 1899 Refuse Act.’’). Congress 

made an effort ‘‘to weave’’ the Refuse Act permit 

program into the 1972 Amendments, id. at 71, as 

the statutory text shows. See 33 U.S.C. 1342(a) 

(providing that each application for a permit under 

33 U.S.C. 407, pending on October 18, 1972, shall 

be deemed an application for a permit under 33 

U.S.C. 1342(a)). 

20City of Milwaukee v. Illinois, 451 U.S. at 317; 

see also id. at 318 (holding that the CWA precluded 

Federal common-law claims because ‘‘Congress’ 

intent in enacting the [CWA] was clearly to 

establish an all-encompassing program of water 

pollution regulation’’); Middlesex County Sewerage 

Auth. v. National Sea Clammers Ass’n, 453 U.S. 1, 

22 (1981) (existing statutory scheme ‘‘was 

completely revised’’ by enactment of the CWA). 

21 40 FR 31320, 31324 (July 25, 1975). 

22Section 404 of the Federal Water Pollution 

Control Act Amendments of 1972: Hearings Before 

the Senate Comm. on Public Works, 94th Cong., 2d 

Sess. (1976); Development of New Regulations by 

the Corps of Engineers, Implementing Section 404 

of the Federal Water Pollution Control Act 

Concerning Permits for Disposal of Dredge or Fill 

Material: Hearings Before the Subcomm. on Water 

Resources of the House Comm. on Public Works 

and Transportation, 94th Cong., 1st Sess. (1975). 

leaving to the Supreme Court the prerogative 

of overruling its precedents. Agostino v. 

Felton, 521 U.S. 203, 237 (1997); United 

States v. Hatter, 532 U.S. 557, 566–567 

(1981). Moreover, when the Supreme Court 

overturns established precedent, it is explicit. 

See, Lawrence v. Texas, 539 U.S. 558, 578 

(‘‘Bowers was not correct when it was 

decided, and it is not correct today. It ought 

not to remain binding precedent. Bowers v. 

Hardwick should be and now is overruled.’’). 

D. The Agencies’ Longstanding Interpretation 

of the Term ‘‘Navigable Waters’’ To Include 

‘‘Interstate Waters’’ 

EPA, the agency charged with 

implementing the CWA, has always 

interpreted the 1972 Act to cover interstate 

waters. Final Rules, 38 FR 13528, May 22, 

1973 (the term ‘‘waters of the United States’’ 

includes ‘‘interstate waters and their 

tributaries, including adjacent wetlands’’). 

While the Corps of Engineers initially limited 

the scope of coverage for purposes of section 

404 of the CWA to those waters that were 

subject to the Rivers and Harbors Act of 1899, 

after a lawsuit, the Corps amended its 

regulations to provide for the same definition 

of ‘‘waters of the United States’’ that EPA’s 

regulations had always established. In 1975, 

the Corps’ revised regulations defined 

‘‘navigable waters’’ to include ‘‘[i]nterstate 

waters landward to their ordinary high water 

mark and up to their headwaters.’’ In their 

final rules promulgated in 1977, the Corps 

adopted EPA’s definition and included 

within the definition of ‘‘waters of the United 

States’’ ‘‘interstate waters and their 

tributaries, including adjacent wetlands.’’ 

The preamble provided an explanation for 

the inclusion of interstate waters: 

The affects [sic] of water pollution in one 

state can adversely affect the quality of the 

waters in another, particularly if the waters 

involved are interstate. Prior to the FWPCA 

amendments of 1972, most federal statutes 

pertaining to water quality were limited to 

interstate waters. We have, therefore, 

included this third category consistent with 

the Federal government’s traditional role to 

protect these waters from the standpoint of 

water quality and the obvious effects on 

interstate commerce that will occur through 

pollution of interstate waters and their 

tributaries. 

Final Rules, 42 FR 37122, July 19, 1977. 

The legislative history similarly provides 

support for the agencies’ interpretation. 

Congress in 1972 concluded that the 

mechanism for controlling discharges and, 

thereby abating pollution, under the FWPCA 

and Refuse Act ‘‘has been inadequate in 

every vital aspect.’’ S. Rep. No. 414, 92d 

Cong., 1st Sess. 7 (1972). The Senate 

Committee on Public Works reported that 

development of water quality standards, 

assigned to the states under the 1965 FWPCA 

Amendments, ‘‘is lagging’’ and the ‘‘1948 

abatement procedures, and the almost total 

lack of enforcement,’’ prompted the search 

for ‘‘more direct avenues of action against 

water polluters and water pollution.’’ Id. at 

5. The Committee further concluded that 

although the Refuse Act permit program 

created in 1970 ‘‘seeks to establish this direct 

approach,’’ it was too weak because it 

applied only to industrial polluters and too 

unwieldy because the authority over each 

permit application was divided between two 

Federal agencies. See id. at 5; see also id. at 

70–72 (discussing inadequacies of Refuse Act 

program). 

In light of the poor success of those 

programs, the Committee recommended a 

more direct and comprehensive approach 

which, after amendment in conference, was 

adopted in the 1972 Act. The text, legislative 

history and purpose of the 1972 

Amendments all show an intent—through 

the revisions—to broaden, improve and 

strengthen, not to curtail, the Federal water 

pollution control program that had existed 

under the Refuse Act and FWPCA.19 The 

1972 FWPCA Amendments were ‘‘not merely 

another law ‘touching interstate waters’ ’’ but 

were ‘‘viewed by Congress as a ‘total 

restructuring’ and ‘complete rewriting’ of the 

existing water pollution legislation.’’ 20

As the legislative history of the 1972 Act 

confirms, Congress’ use of the term ‘‘waters 

of the United States’’ was intended to 

repudiate earlier limits on the reach of 

Federal water pollution efforts: ‘‘The 

conferees fully intend that the term 

‘navigable waters’ be given the broadest 

possible constitutional interpretation 

unencumbered by agency determinations 

which have been made or may be made for 

administrative purposes.’’ See S. Conf. Rep. 

No. 1236, 92d Cong., 2d Sess. 144 (1972). The 

House and Senate Committee Reports further 

elucidate the Conference Committee’s 

rationale for removing the word ‘‘navigable’’ 

from the definition of ‘‘navigable waters,’’ in 

33 U.S.C. 1362(7). The Senate report stated: 

The control strategy of the Act extends to 

navigable waters. The definition of this term 

means the navigable waters of the United 

States, portions thereof, tributaries thereof, 

and includes the territorial seas and the Great 

Lakes. Through a narrow interpretation of the 

definition of interstate waters the 

implementation of the 1965 Act was severely 

limited. Water moves in hydrologic cycles 

and it is essential that discharge of pollutants 

be controlled at the source. Therefore, 

reference to the control requirements must be 

made the navigable waters, portions thereof, 

and their tributaries. 

See S. Rep. 414, 92d Cong., 1st Sess. 77 

(1971); see also H.R. Rep. No. 911, 92d Cong., 

2d Sess. 131 (1972) (‘‘The Committee fully 

intends that the term ‘‘navigable waters’’ be 

given the broadest possible constitutional 

interpretation unencumbered by agency 

determinations which have been made or 

may be made for administrative purposes.’’). 

These passages strongly suggest that Congress 

intended to expand Federal protection of 

waters. There is no evidence that Congress 

intended to exclude interstate waters which 

were protected under Federal law if they 

were not water that is navigable for purposes 

of Federal regulation under the Commerce 

Clause or connected to water that is 

navigable for purposes of Federal regulation 

under the Commerce Clause. Such an 

exclusion would be contrary to all the stated 

goals of Congress in enacting the sweeping 

amendments which became the CWA. 

The CWA was enacted in 1972. EPA’s 

contemporaneous regulatory definition of 

‘‘waters of the United States,’’ promulgated 

in 1973, included interstate waters. The 

definition has been EPA’s interpretation of 

the geographic jurisdictional scope of the 

CWA for approximately 40 years. Congress 

has also been aware of and has supported the 

Agency’s longstanding interpretation of the 

CWA. ‘‘Where ‘an agency’s statutory 

construction has been fully brought to the 

attention of the public and the Congress, and 

the latter has not sought to alter that 

interpretation although it has amended the 

statute in other respects, then presumably the 

legislative intent has been correctly 

discerned.’ ’’ North Haven Board of 

Education v. Bell, 102 456 U.S. 512, 535 

(1982) (quoting United States v. Rutherford, 

442 U.S. 544 n. 10 (1979) (internal quotes 

omitted)). 

The 1977 amendments to the CWA were 

the result of Congress’ thorough analysis of 

the scope of CWA jurisdiction in light of EPA 

and Corps regulations. The 1975 interim final 

regulations promulgated by the Corps in 

response to NRDC v. Callaway,21 aroused 

considerable congressional interest. Hearings 

on the subject of section 404 jurisdiction 

were held in both the House and the 

Senate.22 An amendment to limit the 

geographic reach of section 404 to waters that 

are navigable for purposes of Federal 

regulation under the Commerce Clauses and 

their adjacent wetlands was passed by the 

House, 123 Cong. Rec. 10434 (1977), defeated 

on the floor of the Senate, 123 Cong. Rec. 

26728 (1977), and eliminated by the 

Conference Committee, H.R. Conf. Rep. 95– 

830, 95th Cong., 1st Sess. 97–105 (1977). 

Congress rejected the proposal to limit the 

geographic reach of section 404 because it 

wanted a permit system with ‘‘no gaps’’ in its 

protective sweep. 123 Cong. Rec. 26707 

(1977) (remarks of Sen. Randolph). Rather 

than alter the geographic reach of section 


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23 In Illinois v. Milwaukee, the Supreme Court 

noted that ‘‘Congress has enacted numerous laws 

touching interstate waters.’’ 406 U.S. at 101. 

404, Congress amended the statute by 

exempting certain activities—most notably 

certain agricultural and silvicultural 

activities—from the permit requirements of 

section 404. See 33 U.S.C. 1344(f). 

Other evidence abounds to support the 

conclusion that when Congress rejected the 

attempt to limit the geographic reach of 

section 404, it was well aware of the 

jurisdictional scope of EPA and the Corps’ 

definition of ‘‘waters of the United States.’’ 

For example, Senator Baker stated (123 Cong. 

Rec. 26718 (1977)): 

Interim final regulations were promulgated 

by the [C]orps [on] July 25, 1975.* * * 

Together the regulations and [EPA] 

guidelines established a management 

program that focused the decisionmaking 

process on significant threats to aquatic areas 

while avoiding unnecessary regulation of 

minor activities. On July 19, 1977, the 

[C]orps revised its regulations to further 

streamline the program and correct several 

misunderstandings. * * * 

Continuation of the comprehensive coverage 

of this program is essential for the protection 

of the aquatic environment. The once 

seemingly separable types of aquatic systems 

are, we now know, interrelated and 

interdependent. We cannot expect to 

preserve the remaining qualities of our water 

resources without providing appropriate 

protection for the entire resource. 

Earlier jurisdictional approaches under the 

[Rivers and Harbors Act] established artificial 

and often arbitrary boundaries. . . . 

This legislative history leaves no room for 

doubt that Congress was aware of the 

agencies’ definition of navigable waters. 

While there was controversy over the 

assertion of jurisdiction over all adjacent 

wetlands and some non-adjacent wetlands, 

the agencies’ assertion of CWA jurisdiction 

over interstate waters was uncontroversial. 

Finally, the constitutional concerns which 

led the Supreme Court to decline to defer to 

agency regulations in SWANCC and Rapanos 

are not present here where the agency is 

asserting jurisdiction over interstate waters. 

In SWANCC, the Court declined to defer to 

agency regulations asserting jurisdiction over 

non-adjacent, non-navigable, intrastate 

waters because the Court felt such an 

interpretation of the statute invoked the outer 

limits of Congress’ power. The Court’s 

concern ‘‘is heightened where the 

administrative interpretation alters the 

federal-state framework by permitting federal 

encroachment upon a traditional state 

power.’’ 531 U.S. at 172–173 (citations 

omitted). Authority over interstate waters is 

squarely within the bounds of Congress’ 

Commerce Clause powers.23 Further, the 

Federal Government is in the best position to 

address issues which may arise when waters 

cross state boundaries, so this interpretation 

does not disrupt the Federal-State framework 

in the manner the Supreme Court feared that 

the assertion of jurisdiction over a nonadjacent, non-navigable, intrastate body of 

water based on the presence of migratory 

birds did. The Supreme Court’s analysis in 

Illinois v. Milwaukee and City of Milwaukee 

makes clear that Congress has broad 

authority to create Federal law to resolve 

interstate water pollution disputes. 

Therefore, as discussed in Section II.B above, 

it is appropriate for the agencies to adopt an 

interpretation of the extent of CWA 

jurisdiction over interstate waters that gives 

full effect to City of Milwaukee unless and 

until the Supreme Court elects to revisit its 

holding in that case. 

Thus, based on the language of the statute, 

the statutory history, the legislative history, 

and the caselaw, the agencies’ continue their 

longstanding interpretation of ‘‘navigable 

waters’’ to include interstate waters. 

Tributaries 

In Rapanos, Justice Kennedy reasoned that 

Riverside Bayview and SWANCC ‘‘establish 

the framework for’’ determining whether an 

assertion of regulatory jurisdiction 

constitutes a reasonable interpretation of 

‘‘navigable waters’’—‘‘the connection 

between a non-navigable water or wetland 

and a navigable water may be so close, or 

potentially so close, that the Corps may deem 

the water or wetland a ‘navigable water’ 

under the Act;’’ and ‘‘[a]bsent a significant 

nexus, jurisdiction under the Act is lacking.’’ 

547 U.S. at 767. ‘‘The required nexus must 

be assessed in terms of the statute’s goals and 

purposes. Congress enacted the law to 

‘restore and maintain the chemical, physical, 

and biological integrity of the Nation’s 

waters,’ 33 U.S.C. 1251(a), and it pursued 

that objective by restricting dumping and 

filling in ‘navigable waters,’ sections 1311(a), 

1362(12).’’ Id. at 779. ‘‘Justice Kennedy 

concluded that the term ‘‘waters of the 

United States’’ encompasses wetlands and 

other waters that ‘‘possess a ‘significant 

nexus’ to waters that are or were navigable 

in fact or that could reasonably be so made.’’ 

Id. at 759. He further concluded that 

wetlands possess the requisite significant 

nexus: ‘‘if the wetlands, either alone or in 

combination with similarly situated 

[wetlands] in the region, significantly affect 

the chemical, physical, and biological 

integrity of other covered waters more readily 

understood as ‘navigable.’ ’’ Id. at 780. 

While Justice Kennedy’s opinion focused 

on adjacent wetlands in light of the facts of 

the cases before him, the agencies 

determined it was reasonable and 

appropriate to undertake a detailed 

examination of the scientific literature to 

determine whether tributaries, as a category 

and as the agencies propose to define them, 

significantly affect the chemical, physical, or 

biological integrity of downstream navigable 

waters, interstate waters, or territorial seas 

into which they flow. Based on this extensive 

analysis, the agencies concluded that 

tributaries with bed and banks, and ordinary 

high water marks, alone or in combination 

with other tributaries, as defined by the 

proposed regulation, in the watershed 

perform these functions and should be 

considered, as a category, to be ‘‘waters of the 

United States.’’ 

The assertion of jurisdiction over this 

category of waters is fully consistent with 

Justice Kennedy’s opinion in Rapanos. 

‘‘Justice Kennedy concluded that the term 

‘‘waters of the United States’’ encompasses 

wetlands and other waters that ‘‘possess a 

‘significant nexus’ to waters that are or were 

navigable in fact or that could reasonably be 

so made.’’ Id. at 759. With respect to 

tributaries, Justice Kennedy rejected the 

plurality’s approach that only ‘‘relatively 

permanent’’ tributaries are within the scope 

of CWA jurisdiction. He stated that the 

plurality’s requirement of ‘‘permanent 

standing water or continuous flow, at least 

for a period of ‘some months’ . . . makes 

little practical sense in a statute concerned 

with downstream water quality.’’ Id. at 769. 

Instead, Justice Kennedy concluded that 

‘‘Congress could draw a line to exclude 

irregular waterways, but nothing in the 

statute suggests it has done so;’’ in fact, he 

stated that Congress has done ‘‘[q]uite the 

opposite . . ..’’ Id. at 769. Further, Justice 

Kennedy concluded, based on ‘‘a full reading 

of the dictionary definition’’ of ‘‘waters,’’ that 

‘‘the Corps can reasonably interpret the Act 

to cover the paths of such impermanent 

streams.’’ Id. at 770 (emphasis added). 

Moreover, Justice Kennedy’s opinion did 

not reject the agencies’ existing regulations 

governing tributaries. The consolidated cases 

in Rapanos involved discharges into 

wetlands adjacent to nonnavigable tributaries 

and, therefore, Justice Kennedy’s analysis 

focused on the requisite showing for 

wetlands. Justice Kennedy described the 

Corps’ standard for asserting jurisdiction over 

tributaries: ‘‘the Corps deems a water a 

tributary if it feeds into a traditional 

navigable water (or a tributary thereof) and 

possesses an ordinary high water mark . . ..’’ 

Id. at 781, see also id at 761. He 

acknowledged that this requirement of a 

perceptible ordinary high water mark for 

ephemeral streams, 65 FR 12828, March 9, 

2000, ‘‘[a]ssuming it is subject to reasonably 

consistent application, . . . may well provide 

a reasonable measure of whether specific 

minor tributaries bear a sufficient nexus with 

other regulated waters to constitute navigable 

waters under the Act.’’ 547 U.S. at 781, see 

also id. at 761. With respect to wetlands, 

Justice Kennedy concluded that the breadth 

of this standard for tributaries precluded use 

of adjacency to such tributaries as the 

determinative measure of whether wetlands 

adjacent to such tributaries ‘‘are likely to play 

an important role in the integrity of an 

aquatic system comprising navigable waters 

as traditionally understood.’’ Id. at 781. He 

did not, however, reject the Corps’ use of 

‘‘ordinary high water mark’’ to assert 

regulatory jurisdiction over tributaries 

themselves. Id. 

In the foregoing passage regarding the 

existing regulatory standard for ephemeral 

streams, Justice Kennedy also provided a 

‘‘but see’’ citation to a 2004 U.S. General 

Accounting Office (now the U.S. Government 

Accountability Office) (GAO) report ‘‘noting 

variation in results among Corps district 

offices.’’ Id. In 2005, the Corps issued a 

regulatory guidance letter (RGL 05–05) to 

Corps districts on OHWM identification that 

was designed to ensure more consistent 

practice. The Corps has also issued 

documents to provide additional technical 

assistance for problematic OHWM 

delineations. See, e.g., R.W. Lichvar and S.M. 


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McColley, U.S. Army Corps of Engineers, A 

Field Guide to the Identification of the 

Ordinary High Water Mark (OHWM) in the 

Arid West Region of the Western United 

States: A Delineation Manual, ERDC/CRREL 

TR–08–12 (2008). Moreover, the agencies 

propose today for the first time a regulatory 

definition of ‘‘tributary.’’ The definition 

expressly addresses some of the issues with 

respect to identification of an OHWM that 

caused many of the inconsistencies reported 

by the GAO. For example, this proposed 

regulation clearly provides that a water that 

otherwise meets the proposed definition of 

tributary remains a jurisdictional tributary 

even if there are natural or man-made breaks 

in the OHWM. The proposed definition also 

provides a non-exclusive list of examples of 

breaks in the OHWM to assist in clearly and 

consistently determining what meets the 

definition of tributary. 

Most fundamentally, the agencies believe 

that the scientific literature demonstrates that 

tributaries, as a category and as the agencies 

propose to define them, play a critical role 

in the integrity of aquatic systems comprising 

traditional navigable waters and interstate 

waters, and therefore are ‘‘waters of the 

United States’’ within the meaning of the 

Clean Water Act. 

Adjacent Waters 

The CWA explicitly establishes authority 

over adjacent wetlands. Under section 404(g), 

states are authorized to assume responsibility 

for administration of the section 404 

permitting program with respect to 

‘‘navigable waters (other than those waters 

which are presently used, or are susceptible 

to use in their natural condition or by 

reasonable improvement as a means to 

transport interstate or foreign commerce 

shoreward to their ordinary high water mark, 

including all waters which are subject to the 

ebb and flow of the tide shoreward to their 

mean high water mark, or mean higher high 

water mark on the west coast, including 

wetlands adjacent thereto).’’ 33 U.S.C. 

1344(g)(1) (emphasis added). While this 

provision mainly serves as a limitation on the 

scope of waters for which states may be 

authorized to issue permits, it also shows 

that Congress was concerned with the 

protection of adjacent wetlands and 

recognized their important role in protecting 

downstream traditional navigable waters. 

Indeed, the existing definition of adjacency 

was developed in recognition of the integral 

role wetlands play in broader aquatic 

ecosystems: 

The regulation of activities that cause water 

pollution cannot rely on . . . artificial lines 

. . . but must focus on all waters that 

together form the entire aquatic system. 

Water moves in hydrologic cycles, and the 

pollution of this part of the aquatic system, 

regardless of whether it is above or below an 

ordinary high water mark, or mean high tide 

line, will affect the water quality of the other 

waters within that aquatic system. For this 

reason, the landward limit of Federal 

jurisdiction under Section 404 must include 

any adjacent wetlands that form the border 

of or are in reasonable proximity to other 

waters of the United States, as these wetlands 

are part of this aquatic system. 

42 FR 37128, July 19, 1977. 

As the Supreme Court found in United 

States v. Riverside Bayview Homes, Inc., ‘‘the 

evident breadth of congressional concern for 

protection of water quality and aquatic 

ecosystems suggests that it is reasonable for 

the Corps to interpret the term ‘waters’ to 

encompass wetlands adjacent to waters as 

more conventionally defined.’’ 474 U.S. at 

133. 

In upholding the Corps’ judgment about 

the relationship between waters and their 

adjacent wetlands, the Supreme Court in 

Riverside Bayview acknowledged that the 

agencies’ regulations take into account 

functions provided by wetlands in support of 

this relationship. ‘‘[A]djacent wetlands may 

‘serve significant natural biological functions, 

including food chain production, general 

habitat, and nesting, spawning, rearing and 

resting sites for aquatic . . . species.’ ’’ Id. at 

133 (citing § 320.4(b)(2)(i)). The Court further 

stated that the Corps had reasonably 

concluded that ‘‘wetlands adjacent to lakes, 

rivers, streams, and other bodies of water 

may function as integral parts of the aquatic 

environment even when the moisture 

creating the wetlands does not find its source 

in the adjacent bodies of water.’’ 474 U.S. at 

135. 

Two decades later, a majority of justices in 

Rapanos concluded that the agencies’ 

regulatory definition of adjacent wetlands 

reasonable. Justice Kennedy stated: 

As the Court noted in Riverside Bayview, ‘the 

Corps has concluded that wetlands may serve 

to filter and purify water draining into 

adjacent bodies of water, 33 CFR 

320.4(b)(2)(vii)(1985), and to slow the flow of 

surface runoff into lakes, rivers, and streams 

and thus prevent flooding and erosion, see 

§ 320.4(b)(2)(iv) and (v).’ Where wetlands 

perform these filtering and runoff-control 

functions, filling them may increase 

downstream pollution, much as a discharge 

of toxic pollutants would.. . . In many cases, 

moreover, filling in wetlands separated from 

another water by a berm can mean that flood 

water, impurities, or runoff that would have 

been stored or contained in the wetlands will 

instead flow out to major waterways. With 

these concerns in mind, the Corps’ definition 

of adjacency is a reasonable one, for it may 

be the absence of an interchange of waters 

prior to the dredge and fill activity that 

makes protection of the wetlands critical to 

the statutory scheme. 

547 U.S. at 775 (citations omitted). 

The four dissenting justices similarly 

concluded: 

The Army Corps has determined that 

wetlands adjacent to tributaries of 

traditionally navigable waters preserve the 

quality of our Nation’s waters by, among 

other things, providing habitat for aquatic 

animals, keeping excessive sediment and 

toxic pollutants out of adjacent waters, and 

reducing downstream flooding by absorbing 

water at times of high flow. The Corps’ 

resulting decision to treat these wetlands as 

encompassed within the term ‘waters of the 

United States’ is a quintessential example of 

the Executive’s reasonable interpretation of a 

statutory provision. 

Id. at 778 (citing Chevron U.S.A. Inc. v. 

Natural Resources Defense Council, Inc., 467 

U.S. 837, 842–845 (1984)). 

For those wetlands adjacent to traditional 

navigable waters, Justice Kennedy concluded 

in Rapanos that the agencies’ existing 

regulation ‘‘rests upon a reasonable inference 

of ecologic interconnection, and the assertion 

of jurisdiction for those wetlands is 

sustainable under the Act by showing 

adjacency alone.’’ 547 U.S. at 780. For other 

adjacent waters, including adjacent wetlands, 

Justice Kennedy’s significant nexus standard 

provides a framework for establishing 

categories of waters which are per se ‘‘waters 

of the United States.’’ First, he provided that 

wetlands are jurisdictional if they ‘‘either 

alone or in combination with similarly 

situated lands in the region, significantly 

affect the chemical, physical, and biological 

integrity of other covered waters more readily 

understood as ‘navigable.’ ’’ Id. at 780. Next, 

Justice Kennedy stated that ‘‘[t]hrough 

regulation or adjudication, the Corps may 

choose to identify categories of tributaries 

that, due to their volume of flow (either 

annually or on average), their proximity to 

navigable waters, or other relevant 

considerations, are significant enough that 

wetlands adjacent to them are likely, in the 

majority of cases, to perform important 

functions for an aquatic system incorporating 

navigable waters.’’ Id. at 780–81. 

While the issue was not before the 

Supreme Court, it is reasonable to also assess 

whether non-wetland waters have a 

significant nexus, as Justice Kennedy’s 

opinion makes clear that a significant nexus 

is a touchstone for CWA jurisdiction. The 

agencies have determined that adjacent 

waters as defined in today’s proposed rule, 

alone or in combination with other adjacent 

waters in the region that drains to a 

traditional navigable water, interstate water 

or the territorial seas, significantly affect the 

chemical, physical, and biological integrity of 

those waters. As explained in more detail in 

Section H, below, the proposed rule 

interprets the phrase ‘‘in the region’’ to mean 

the watershed that drains to the nearest 

traditional navigable water or interstate water 

through a single point of entry. The agencies 

have determined that because the movement 

of water from watershed drainage basins to 

river networks and lakes shapes the 

development and function of these systems 

in a way that is critical to their long term 

health, the watershed is a reasonable and 

technically appropriate reflection of 

Congressional intent. 

The agencies have concluded that all 

waters that meet the proposed definition of 

‘‘adjacent’’ are similarly situated for purposes 

of analyzing whether they, in the majority of 

cases, have a significant nexus to an (a)(1) 

through (a)(3) water. Based on the agencies’ 

review of the scientific literature, we have 

concluded that these waters, when bordering, 

contiguous or located in the floodplain or 

riparian area, or when otherwise meeting the 

definition of ‘‘adjacent,’’ provide many 

similar functions that significantly affect the 

chemical, physical, or biological integrity of 

traditional navigable waters, interstate 

waters, or the territorial seas. Further, 

because the proposed definition generally 


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focuses on the location of the waters (i.e., 

those that are located near (a)(1) through 

(a)(5) waters), interpreting the term 

‘‘similarly situated’’ to include all adjacent 

waters, as defined in the proposed rule, is 

reasonable and consistent with the science. 

The geographic position of an ‘‘adjacent’’ 

water relative to the tributary is indicative of 

the relationship to it, with many of its 

defining characteristics resulting from the 

movement of materials and energy between 

the categories of waters. The scientific 

literature documents that waters that are 

adjacent to (a)(1) through (a)(5) waters, 

including wetlands, oxbow lakes and 

adjacent ponds, are integral parts of stream 

networks because of their ecological 

functions and how they interact with each 

other, and with downstream traditional 

navigable waters, interstate waters, or the 

territorial seas. In other words, tributaries 

and their adjacent waters, and the 

downstream traditional navigable waters, 

interstate waters, and territorial seas into 

which those waters flow, are an integrated 

ecological system, and discharges of 

pollutants, including discharges of dredged 

or fill material, into any component of that 

ecological system, must be regulated under 

the CWA to restore and maintain the 

chemical, physical, or biological integrity of 

these waters. 

Based on the science, as summarized 

below, the agencies have concluded that 

wetlands and waters adjacent to all 

tributaries that meet the proposed definition 

of ‘‘tributary’’ provide vital functions for 

downstream traditional navigable waters, 

interstate waters, or the territorial seas. In 

particular, the scientific literature supports 

the conclusion that waters adjacent to all 

tributaries as defined in section (a)(5) have a 

significant nexus to waters described in 

paragraphs (a)(1) through (a)(3). Because 

smaller streams, whether perennial, 

intermittent, or ephemeral, are much more 

common than larger streams, the volume of 

a stream’s flow is not the best measure of its 

contribution to the chemical, physical, or 

biological integrity of downstream waters. 

Report at 4–2, 4–3. As discussed in more 

detail in Appendix A, small streams 

cumulatively exert a strong influence on 

downstream waters, partly by collectively 

providing a substantial amount of the river’s 

water, id. at 4–3, 4–4 to 4–5, but also by 

playing unique roles that large streams 

typically do not, including providing habitat 

for aquatic macroinvertebrates which help 

maintain the health of the downstream water. 

Waters adjacent to those small tributary 

streams, therefore, also significantly affect 

(a)(1) through (a)(3) waters through the 

movement of energy and materials between 

adjacent waters and those tributaries, 

resulting ultimately in significant 

downstream effects on the chemical, 

physical, and biological integrity of the (a)(1) 

through (a)(3) waters. 

‘‘Other Waters’’ 

In Rapanos, Justice Kennedy provides an 

approach for determining what constitutes a 

‘‘significant nexus’’ that can serve as a basis 

for defining ‘‘waters of the United States’’ 

through regulation. Justice Kennedy 

concluded that ‘‘to constitute ‘navigable 

waters’ under the Act, a water or wetland 

must possess a ‘significant nexus’ to waters 

that are or were navigable in fact or that 

could reasonably be so made.’’ Id. at 759 

(citing SWANCC, 531 U.S. at 167, 172). 

Again, the four justices who signed on to 

Justice Stevens’ opinion would have upheld 

jurisdiction under the agencies’ existing 

regulations and stated that they would 

uphold jurisdiction under either the plurality 

or Justice Kennedy’s opinion. Justice 

Kennedy stated that wetlands should be 

considered to possess the requisite nexus in 

the context of assessing whether wetlands are 

jurisdictional: ‘‘if the wetlands, either alone 

or in combination with similarly situated 

[wetlands] in the region, significantly affect 

the chemical, physical, and biological 

integrity of other covered waters more readily 

understood as ‘navigable.’ ’’ Id. at 780. In 

light of Rapanos and SWANCC, the 

‘‘significant nexus’’ standard for CWA 

jurisdiction that Justice Kennedy’s opinion 

applied to adjacent wetlands also can 

reasonably be applied to other waters such as 

ponds, lakes, and non-adjacent wetlands that 

may have a significant nexus to a traditional 

navigable water, an interstate water, or the 

territorial seas. 

The proposed rule includes a definition of 

significant nexus that is consistent with 

Justice Kennedy’s significant nexus standard. 

In characterizing the significant nexus 

standard, Justice Kennedy stated: ‘‘The 

required nexus must be assessed in terms of 

the statute’s goals and purposes. Congress 

enacted the [CWA] to ‘restore and maintain 

the chemical, physical, and biological 

integrity of the Nation’s waters’ . . ..’’ 547 

U.S. at 779. It clear that Congress intended 

the CWA to ‘‘restore and maintain’’ all three 

forms of ‘‘integrity,’’ 33 U.S.C. 1251(a), so if 

any one form is compromised then that is 

contrary to the statute’s stated objective. It 

would subvert the intent if the CWA only 

protected waters upon a showing that they 

had effects on every attribute of a traditional 

navigable water, interstate water, or 

territorial sea. Therefore, a showing of a 

significant chemical, physical, or biological 

affect should satisfy the significant nexus 

standard. 

Justice Kennedy’s opinion provides 

guidance pointing to many functions of 

waters that might demonstrate a significant 

nexus, such as sediment trapping, nutrient 

recycling, pollutant trapping and filtering, 

retention or attenuation of flood waters, and 

runoff storage. See 547 U.S. at 775, 779–80. 

Furthermore, Justice Kennedy recognized 

that a hydrologic connection is not necessary 

to establish a significant nexus, because in 

some cases the absence of a hydrologic 

connection would show the significance of a 

water to the aquatic system, such as retention 

of flood waters or pollutants that would 

otherwise flow downstream to the traditional 

navigable water or interstate water. Id. at 775. 

Finally, Justice Kennedy was clear that the 

requisite nexus must be more than 

‘‘speculative or insubstantial’’ in order to be 

significant. Id. at 780. Justice Kennedy’s 

standard is consistent with basic scientific 

principles about how to restore and maintain 

the integrity of aquatic ecosystems. 

Similarly Situated 

For purposes of analyzing the significant 

nexus of tributaries and adjacent waters, 

tributaries that meet the proposed definition 

of ‘‘tributary’’ in a watershed draining to an 

(a)(1) through (a)(3) water are similarly 

situated, and adjacent waters that meet the 

proposed definition of ‘‘adjacent’’ in a 

watershed draining to an (a)(1) through (a)(3) 

water are similarly situated. That is 

reasonable because the agencies are 

identifying characteristics of these waters 

through the regulation and documenting the 

science that demonstrates that these defined 

tributaries and defined adjacent waters 

provide similar functions in the watershed. 

As stated above, the functions of the 

tributaries are inextricably linked and have a 

cumulative effect on the integrity of the 

downstream traditional navigable water or 

interstate water. There is also an obvious 

locational relationship between the (a)(1), 

(a)(2) or (a)(3) water and the streams, lakes, 

and wetlands that meet the definition of 

tributaries and the definition of adjacent 

waters; these waters have a clear linear 

relationship resulting from the simple 

existence of the channel itself and the 

direction of flow. See Appendix A, Scientific 

Evidence. 

‘‘Other waters,’’ on the other hand, 

constitute a broad range of different types of 

waters performing different functions. In 

light of the range and degree of functions 

performed by waters that are neither 

tributaries nor adjacent waters under today’s 

proposed rule, the agencies propose a 

definition of similarly situated which takes 

into account similarity of functions provided 

and situation in the landscape. Since the 

focus of the significant nexus standard is on 

protecting the chemical, physical, and 

biological integrity of the nation’s waters, the 

agencies propose to interpret the phrase 

‘‘similarly situated’’ in terms of whether the 

functions provided by the particular ‘‘other 

waters’’ are similar and, therefore, whether 

such ‘‘other waters’’ are collectively 

influencing the chemical, physical, or 

biological integrity of downstream waters. 

There are many functions of waters that 

might demonstrate a significant nexus, such 

as sediment trapping, nutrient recycling, 

pollutant trapping and filtering, retention or 

attenuation of flood waters, runoff storage, 

and provision of habitat. See 547 U.S. at 775, 

779–80. This approach is consistent not only 

with the significant nexus standard, but with 

the science of aquatic systems. 

The absence of a hydrologic connection 

between ‘‘other waters’’ and traditional 

navigable waters, interstate waters, or the 

territorial seas may demonstrate the presence 

of a significant nexus between such waters, 

as Justice Kennedy recognized in his opinion. 

‘‘Other waters’’ frequently function alone or 

cumulatively with similarly situated ‘‘other 

waters’’ in the region to capture runoff, rain 

water, or snowmelt and thereby protect the 

integrity of downstream waters by reducing 

potential flooding or trapping pollutants that 

would otherwise reach a traditional 

navigable water or interstate water. See id. at 

775. Such waters can be crucial in 

controlling flooding as well as in maintaining 

water quality by trapping or transforming 


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pollutants such as excess nutrients or 

sediment, for example, or retaining 

precipitation or snow melt, thereby reducing 

contamination or flooding of traditional 

navigable waters, interstate waters, or the 

territorial seas. 

Significant Nexus 

The agencies propose to define the term 

‘‘significant nexus’’ consistent with language 

in SWANCC and Rapanos. The proposed 

definition of ‘‘significant nexus’’ at (c)(7) 

relies most significantly on Justice Kennedy’s 

Rapanos opinion which recognizes that not 

all waters have this requisite connection to 

waters covered by paragraphs (a)(1) through 

(a)(3) of the proposed regulations. Justice 

Kennedy was clear that the requisite nexus 

must be more than ‘‘speculative or 

insubstantial. . ., ’’ Rapanos, 547 U.S. at 

780, in order to be significant and the 

proposed rule defines significant nexus in 

precisely those terms. In Rapanos, Justice 

Kennedy stated that in both the consolidated 

cases before the Court the record contained 

evidence suggesting the possible existence of 

a significant nexus according to the 

principles he identified. See id. at 783. 

Justice Kennedy concluded that ‘‘the end 

result in these cases and many others to be 

considered by the Corps may be the same as 

that suggested by the dissent, namely, that 

the Corps’ assertion of jurisdiction is valid.’’ 

Id. Justice Kennedy remanded the cases 

because neither the agency nor the reviewing 

courts properly applied the controlling legal 

standard—whether the wetlands at issue had 

a significant nexus. See id. Justice Kennedy 

was clear however, that ‘‘[m]uch the same 

evidence should permit the establishment of 

a significant nexus with navigable-in-fact 

waters, particularly if supplemented by 

further evidence about the significance of the 

tributaries to which the wetlands are 

connected.’’ Id. at 784. 

With respect to one of the wetlands at issue 

in the consolidated Rapanos cases, Justice 

Kennedy stated: 

In Carabell, No. 04–1384, the record also 

contains evidence bearing on the 

jurisdictional inquiry. The Corps noted in 

deciding the administrative appeal that 

‘‘[b]esides the effects on wildlife habitat and 

water quality, the [district office] also noted 

that the project would have a major, longterm detrimental effect on wetlands, flood 

retention, recreation and conservation and 

overall ecology. . . . The Corps’ evaluation 

further noted that by ‘eliminat[ing] the 

potential ability of the wetland to act as a 

sediment catch basin,’’ the proposed project 

‘‘would contribute to increased runoff and 

. . . accretion along the drain and further 

downstream in Auvase Creek.’ . . . And it 

observed that increased runoff from the site 

would likely cause downstream areas to ‘‘see 

an increase in possible flooding magnitude 

and frequency.’’ 

Id. at 785–86. Justice Kennedy also expressed 

concern that ‘‘[t]he conditional language in 

these assessments—‘potential ability,’ 

‘possible flooding’—could suggest an undue 

degree of speculation.’’ Id.at 786. 

Justice Kennedy’s observations regarding 

the above case provide guidance as to what 

it means for a nexus to be more than merely 

speculative or insubstantial and inform the 

proposed definition of ‘‘significant nexus.’’ It 

is important to note, however, that where 

Justice Kennedy viewed the language ‘‘more 

than speculative or insubstantial’’ to suggest 

an undue degree of speculation, scientists do 

not equate certain conditional language (such 

as ‘‘may’’ or ‘‘could’’) with speculation, but 

rather with the rigorous and precise language 

of science necessary when applying specific 

findings in another individual situation or 

more broadly across a variety of situations. 

Certain terms used in a scientific context do 

not have the same implications that they 

have in a legal or policy context. Scientists 

use cautionary language, such as ‘‘may’’ or 

‘‘could,’’ when applying specific findings on 

a broader scale to avoid the appearance of 

overstating their research results and to avoid 

inserting bias into their findings (such that 

the reader may think the results of one study 

are applicable in all related studies). Words 

like ‘‘potential’’ are commonly used in the 

biological sciences, but when viewed under 

a legal and policy veil, may seem to mean the 

same as ‘‘speculative’’ or ‘‘insubstantial.’’ 

Instead, potential in scientific terms means 

ability or capability. For example, when the 

term ‘‘potential’’ is used to describe how a 

wetland has the potential to act as a sink for 

floodwater and pollutants, scientists mean 

that wetlands in general do indeed perform 

those functions, but whether a particular 

wetland performs that function is dependent 

upon the circumstances that would create 

conditions for floodwater or pollutants in the 

watershed to reach that particular wetland to 

retain and transform. That does not mean, 

however, that this nexus to downstream 

waters is ‘‘speculative;’’ indeed the wetland 

would be expected to provide these functions 

under the proper circumstances. 

Definition of ‘‘Waters of the United 

States’’ Under the Clean Water Act. 

List of Subjects 

33 CFR Part 328 

Environmental protection, 

Administrative practice and procedure, 

Intergovernmental relations, Navigation, 

Water pollution control, Waterways. 

40 CFR Part 110 

Environmental protection, Water 

pollution control. 

40 CFR Part 112 

Environmental protection, Water 

pollution control. 

40 CFR Part 116 

Environmental protection, Water 

pollution control. 

40 CFR Part 117 

Environmental protection, Water 

pollution control. 

40 CFR Part 122 

Environmental protection, Water 

pollution control. 

40 CFR Part 230 

Environmental protection, Water 

pollution control. 

40 CFR Part 232 

Environmental protection, Water 

pollution control. 

40 CFR Part 300 

Environmental protection, Water 

pollution control. 

40 CFR Part 302 

Environmental protection, Water 

pollution control. 

40 CFR Part 401 

Environmental protection, Water 

pollution control. 

Dated: March 25, 2014. 

Gina McCarthy, 

Administrator, Environmental Protection 

Agency. 

Dated: March 24, 2014. 

Jo Ellen Darcy, 

Assistant Secretary of the Army (Civil Works), 

Department of the Army. 

Title 33—Navigation and Navigable 

Waters 

For the reasons set out in the 

preamble, title 33, chapter I of the Code 

of Federal Regulations is proposed to be 

amended as follows: 

PART 328—DEFINITION OF WATERS 

OF THE UNITED STATES 

■ 1. The authority citation for part 328 

continues to read as follows: 

Authority: The Clean Water Act, 33 U.S.C. 

1251 et seq. 

■ 2. Section 328.3 is amended by 

removing the introductory text and 

revising paragraphs (a), (b), and (c) to 

read as follows: 

§ 328.3 Definitions. 

(a) For purposes of all sections of the 

Clean Water Act, 33 U.S.C. 1251 et. seq. 

and its implementing regulations, 

subject to the exclusions in paragraph 

(b) of this section, the term ‘‘waters of 

the United States’’ means: 

(1) All waters which are currently 

used, were used in the past, or may be 

susceptible to use in interstate or foreign 

commerce, including all waters which 

are subject to the ebb and flow of the 

tide; 

(2) All interstate waters, including 

interstate wetlands; 

(3) The territorial seas; 

(4) All impoundments of waters 

identified in paragraphs (a)(1) through 

(3) and (5) of this section; 

(5) All tributaries of waters identified 

in paragraphs (a)(1) through (4) of this 

section; 


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(6) All waters, including wetlands, 

adjacent to a water identified in 

paragraphs (a)(1) through (5) of this 

section; and 

(7) On a case-specific basis, other 

waters, including wetlands, provided 

that those waters alone, or in 

combination with other similarly 

situated waters, including wetlands, 

located in the same region, have a 

significant nexus to a water identified in 

paragraphs (a)(1) through (3) of this 

section. 

(b) The following are not ‘‘waters of 

the United States’’ notwithstanding 

whether they meet the terms of 

paragraphs (a)(1) through (7) of this 

section— 

(1) Waste treatment systems, 

including treatment ponds or lagoons, 

designed to meet the requirements of 

the Clean Water Act. 

(2) Prior converted cropland. 

Notwithstanding the determination of 

an area’s status as prior converted 

cropland by any other Federal agency, 

for the purposes of the Clean Water Act 

the final authority regarding Clean 

Water Act jurisdiction remains with 

EPA. 

(3) Ditches that are excavated wholly 

in uplands, drain only uplands, and 

have less than perennial flow. 

(4) Ditches that do not contribute 

flow, either directly or through another 

water, to a water identified in 

paragraphs (a)(1) through (4) of this 

section. 

(5) The following features: 

(i) Artificially irrigated areas that 

would revert to upland should 

application of irrigation water to that 

area cease; 

(ii) Artificial lakes or ponds created 

by excavating and/or diking dry land 

and used exclusively for such purposes 

as stock watering, irrigation, settling 

basins, or rice growing; 

(iii) Artificial reflecting pools or 

swimming pools created by excavating 

and/or diking dry land; 

(iv) Small ornamental waters created 

by excavating and/or diking dry land for 

primarily aesthetic reasons; 

(v) Water-filled depressions created 

incidental to construction activity; 

(vi) Groundwater, including 

groundwater drained through 

subsurface drainage systems; and 

(vii) Gullies and rills and non-wetland 

swales. 

(c) Definitions— 

(1) Adjacent. The term adjacent 

means bordering, contiguous or 

neighboring. Waters, including 

wetlands, separated from other waters of 

the United States by man-made dikes or 

barriers, natural river berms, beach 

dunes and the like are ‘‘adjacent 

waters.’’ 

(2) Neighboring. The term 

neighboring, for purposes of the term 

‘‘adjacent’’ in this section, includes 

waters located within the riparian area 

or floodplain of a water identified in 

paragraphs (a)(1) through (5) of this 

section, or waters with a shallow 

subsurface hydrologic connection or 

confined surface hydrologic connection 

to such a jurisdictional water. 

(3) Riparian area. The term riparian 

area means an area bordering a water 

where surface or subsurface hydrology 

directly influence the ecological 

processes and plant and animal 

community structure in that area. 

Riparian areas are transitional areas 

between aquatic and terrestrial 

ecosystems that influence the exchange 

of energy and materials between those 

ecosystems. 

(4) Floodplain. The term floodplain 

means an area bordering inland or 

coastal waters that was formed by 

sediment deposition from such water 

under present climatic conditions and is 

inundated during periods of moderate to 

high water flows. 

(5) Tributary. The term tributary 

means a water physically characterized 

by the presence of a bed and banks and 

ordinary high water mark, as defined at 

33 CFR 328.3(e), which contributes 

flow, either directly or through another 

water, to a water identified in 

paragraphs (a)(1) through (4) of this 

section. In addition, wetlands, lakes, 

and ponds are tributaries (even if they 

lack a bed and banks or ordinary high 

water mark) if they contribute flow, 

either directly or through another water 

to a water identified in paragraphs (a)(1) 

through (3) of this section. A water that 

otherwise qualifies as a tributary under 

this definition does not lose its status as 

a tributary if, for any length, there are 

one or more man-made breaks (such as 

bridges, culverts, pipes, or dams), or one 

or more natural breaks (such as 

wetlands at the head of or along the run 

of a stream, debris piles, boulder fields, 

or a stream that flows underground) so 

long as a bed and banks and an ordinary 

high water mark can be identified 

upstream of the break. A tributary, 

including wetlands, can be a natural, 

man-altered, or man-made water and 

includes waters such as rivers, streams, 

lakes, ponds, impoundments, canals, 

and ditches not excluded in paragraph 

(b)(3) or (4) of this section. 

(6) Wetlands. The term wetlands 

means those areas that are inundated or 

saturated by surface or groundwater at 

a frequency and duration sufficient to 

support, and that under normal 

circumstances do support, a prevalence 

of vegetation typically adapted for life 

in saturated soil conditions. Wetlands 

generally include swamps, marshes, 

bogs and similar areas. 

(7) Significant nexus. The term 

significant nexus means that a water, 

including wetlands, either alone or in 

combination with other similarly 

situated waters in the region (i.e., the 

watershed that drains to the nearest 

water identified in paragraphs (a)(1) 

through (3) of this section), significantly 

affects the chemical, physical, or 

biological integrity of a water identified 

in paragraphs (a)(1) through (3) of this 

section. For an effect to be significant, 

it must be more than speculative or 

insubstantial. Other waters, including 

wetlands, are similarly situated when 

they perform similar functions and are 

located sufficiently close together or 

sufficiently close to a ‘‘water of the 

United States’’ so that they can be 

evaluated as a single landscape unit 

with regard to their effect on the 

chemical, physical, or biological 

integrity of a water identified in 

paragraphs (a)(1) through (3) of this 

section. 

* * * * * 

Title 40—Protection of Environment 

For the reasons set out in the 

preamble, title 40, chapter I of the Code 

of Federal Regulations is proposed to be 

amended as follows: 

PART 110—DISCHARGE OF OIL 

■ 3. The authority citation for part 110 

continues to read as follows: 

Authority: The Clean Water Act, 33 U.S.C. 

1321 et seq. 

■ 4. Section 110.1 is amended by 

revising the definition of ‘‘navigable 

waters’’ to read as follows: 

§ 110.1 Definitions. 

* * * * * 

Navigable waters means the waters of 

the United States, including the 

territorial seas. 

(1) For purposes of all sections of the 

Clean Water Act, 33 U.S.C. 1251 et. seq. 

and its implementing regulations, 

subject to the exclusions in paragraph 

(2) of this definition, the term ‘‘waters 

of the United States’’ means: 

(i) All waters which are currently 

used, were used in the past, or may be 

susceptible to use in interstate or foreign 

commerce, including all waters which 

are subject to the ebb and flow of the 

tide; 

(ii) All interstate waters, including 

interstate wetlands; 

(iii) The territorial seas; 

(iv) All impoundments of waters 

identified in paragraphs (1)(i) through 

(iii) and (v) of this definition; 


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(v) All tributaries of waters identified 

in paragraphs (1)(i) through (iv) of this 

definition; 

(vi) All waters, including wetlands, 

adjacent to a water identified in 

paragraphs (1)(i) through (v) of this 

definition; and 

(vii) On a case-specific basis, other 

waters, including wetlands, provided 

that those waters alone, or in 

combination with other similarly 

situated waters, including wetlands, 

located in the same region, have a 

significant nexus to a water identified in 

paragraphs (1)(i) through (iii) of this 

definition. 

(2) The following are not ‘‘waters of 

the United States’’ notwithstanding 

whether they meet the terms of 

paragraphs (1)(i) through (vii) of this 

definition— 

(i) Waste treatment systems, including 

treatment ponds or lagoons, designed to 

meet the requirements of the Clean 

Water Act. 

(ii) Prior converted cropland. 

Notwithstanding the determination of 

an area’s status as prior converted 

cropland by any other Federal agency, 

for the purposes of the Clean Water Act 

the final authority regarding Clean 

Water Act jurisdiction remains with 

EPA. 

(iii) Ditches that are excavated wholly 

in uplands, drain only uplands, and 

have less than perennial flow. 

(iv) Ditches that do not contribute 

flow, either directly or through another 

water, to a water identified in 

paragraphs (1)(i) through (iv) of this 

definition. 

(v) The following features: 

(A) Artificially irrigated areas that 

would revert to upland should 

application of irrigation water to that 

area cease; 

(B) Artificial lakes or ponds created 

by excavating and/or diking dry land 

and used exclusively for such purposes 

as stock watering, irrigation, settling 

basins, or rice growing; 

(C) Artificial reflecting pools or 

swimming pools created by excavating 

and/or diking dry land; 

(D) Small ornamental waters created 

by excavating and/or diking dry land for 

primarily aesthetic reasons; 

(E) Water-filled depressions created 

incidental to construction activity; 

(F) Groundwater, including 

groundwater drained through 

subsurface drainage systems; and 

(G) Gullies and rills and non-wetland 

swales. 

(3) Definitions— 

(i) Adjacent. The term adjacent means 

bordering, contiguous or neighboring. 

Waters, including wetlands, separated 

from other waters of the United States 

by man-made dikes or barriers, natural 

river berms, beach dunes and the like 

are ‘‘adjacent waters.’’ 

(ii) Neighboring. The term 

neighboring, for purposes of the term 

‘‘adjacent’’ in this section, includes 

waters located within the riparian area 

or floodplain of a water identified in 

paragraphs (1)(i) through (v) of this 

definition, or waters with a shallow 

subsurface hydrologic connection or 

confined surface hydrologic connection 

to such a jurisdictional water. 

(iii) Riparian area. The term riparian 

area means an area bordering a water 

where surface or subsurface hydrology 

directly influence the ecological 

processes and plant and animal 

community structure in that area. 

Riparian areas are transitional areas 

between aquatic and terrestrial 

ecosystems that influence the exchange 

of energy and materials between those 

ecosystems. 

(iv) Floodplain. The term floodplain 

means an area bordering inland or 

coastal waters that was formed by 

sediment deposition from such water 

under present climatic conditions and is 

inundated during periods of moderate to 

high water flows. 

(v) Tributary. The term tributary 

means a water physically characterized 

by the presence of a bed and banks and 

ordinary high water mark, as defined at 

33 CFR 328.3(e), which contributes 

flow, either directly or through another 

water, to a water identified in 

paragraphs (1)(i) through (iv) of this 

definition. In addition, wetlands, lakes, 

and ponds are tributaries (even if they 

lack a bed and banks or ordinary high 

water mark) if they contribute flow, 

either directly or through another water 

to a water identified in paragraphs (1)(i) 

through (iii) of this definition. A water 

that otherwise qualifies as a tributary 

under this definition does not lose its 

status as a tributary if, for any length, 

there are one or more man-made breaks 

(such as bridges, culverts, pipes, or 

dams), or one or more natural breaks 

(such as wetlands at the head of or along 

the run of a stream, debris piles, boulder 

fields, or a stream that flows 

underground) so long as a bed and 

banks and an ordinary high water mark 

can be identified upstream of the break. 

A tributary, including wetlands, can be 

a natural, man-altered, or man-made 

water and includes waters such as 

rivers, streams, lakes, ponds, 

impoundments, canals, and ditches not 

excluded in paragraph (2)(iii) or (iv) of 

this definition. 

(vi) Wetlands. The term wetlands 

means those areas that are inundated or 

saturated by surface or groundwater at 

a frequency and duration sufficient to 

support, and that under normal 

circumstances do support, a prevalence 

of vegetation typically adapted for life 

in saturated soil conditions. Wetlands 

generally include swamps, marshes, 

bogs and similar areas. 

(vii) Significant nexus. The term 

significant nexus means that a water, 

including wetlands, either alone or in 

combination with other similarly 

situated waters in the region (i.e., the 

watershed that drains to the nearest 

water identified in paragraphs (1)(i) 

through (iii) of this definition), 

significantly affects the chemical, 

physical, or biological integrity of a 

water identified in paragraphs (1)(i) 

through (iii) of this definition. For an 

effect to be significant, it must be more 

than speculative or insubstantial. Other 

waters, including wetlands, are 

similarly situated when they perform 

similar functions and are located 

sufficiently close together or sufficiently 

close to a ‘‘water of the United States’’ 

so that they can be evaluated as a single 

landscape unit with regard to their 

effect on the chemical, physical, or 

biological integrity of a water identified 

in paragraphs (1)(i) through (iii) of this 

definition. 

* * * * * 

PART 112—OIL POLLUTION 

PREVENTION 

■ 5. The authority citation for part 112 

continues to read as follows: 

Authority: The Clean Water Act, 33 U.S.C. 

1321 et seq. 

■ 6. Section 112.2 is amended by 

revising the definition of ‘‘navigable 

waters’’ to read as follows: 

§ 112.2 Definitions. 

* * * * * 

Navigable waters means the waters of 

the United States, including the 

territorial seas. 

(1) For purposes of all sections of the 

Clean Water Act, 33 U.S.C. 1251 et. seq. 

and its implementing regulations, 

subject to the exclusions in paragraph 

(b) of this section, the term ‘‘waters of 

the United States’’ means: 

(i) All waters which are currently 

used, were used in the past, or may be 

susceptible to use in interstate or foreign 

commerce, including all waters which 

are subject to the ebb and flow of the 

tide; 

(ii) All interstate waters, including 

interstate wetlands; 

(iii) The territorial seas; 

(iv) All impoundments of waters 

identified in paragraphs (1)(i) through 

(iii) and (v) of this definition; 


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(v) All tributaries of waters identified 

in paragraphs (1)(i) through (iv) of this 

definition; 

(vi) All waters, including wetlands, 

adjacent to a water identified in 

paragraphs (1)(i) through (v) of this 

definition; and 

(vii) On a case-specific basis, other 

waters, including wetlands, provided 

that those waters alone, or in 

combination with other similarly 

situated waters, including wetlands, 

located in the same region, have a 

significant nexus to a water identified in 

paragraphs (1)(i) through (iii) of this 

definition. 

(2) The following are not ‘‘waters of 

the United States’’ notwithstanding 

whether they meet the terms of 

paragraphs (1)(i) through (vii) of this 

definition —— 

(i) Waste treatment systems, including 

treatment ponds or lagoons, designed to 

meet the requirements of the Clean 

Water Act. 

(ii) Prior converted cropland. 

Notwithstanding the determination of 

an area’s status as prior converted 

cropland by any other Federal agency, 

for the purposes of the Clean Water Act 

the final authority regarding Clean 

Water Act jurisdiction remains with 

EPA. 

(iii) Ditches that are excavated wholly 

in uplands, drain only uplands, and 

have less than perennial flow. 

(iv) Ditches that do not contribute 

flow, either directly or through another 

water, to a water identified in 

paragraphs (1)(i) through (iv) of this 

definition. 

(v) The following features: 

(A) Artificially irrigated areas that 

would revert to upland should 

application of irrigation water to that 

area cease; 

(B) Artificial lakes or ponds created 

by excavating and/or diking dry land 

and used exclusively for such purposes 

as stock watering, irrigation, settling 

basins, or rice growing; 

(C) Artificial reflecting pools or 

swimming pools created by excavating 

and/or diking dry land; 

(D) Small ornamental waters created 

by excavating and/or diking dry land for 

primarily aesthetic reasons; 

(E) Water-filled depressions created 

incidental to construction activity; 

(F) Groundwater, including 

groundwater drained through 

subsurface drainage systems; and 

(G) Gullies and rills and non-wetland 

swales. 

(3) Definitions— 

(i) Adjacent. The term adjacent means 

bordering, contiguous or neighboring. 

Waters, including wetlands, separated 

from other waters of the United States 

by man-made dikes or barriers, natural 

river berms, beach dunes and the like 

are ‘‘adjacent waters.’’ 

(ii) Neighboring. The term 

neighboring, for purposes of the term 

‘‘adjacent’’ in this section, includes 

waters located within the riparian area 

or floodplain of a water identified in 

paragraphs (1)(i) through (v) of this 

definition, or waters with a shallow 

subsurface hydrologic connection or 

confined surface hydrologic connection 

to such a jurisdictional water. 

(iii) Riparian area. The term riparian 

area means an area bordering a water 

where surface or subsurface hydrology 

directly influence the ecological 

processes and plant and animal 

community structure in that area. 

Riparian areas are transitional areas 

between aquatic and terrestrial 

ecosystems that influence the exchange 

of energy and materials between those 

ecosystems. 

(iv) Floodplain. The term floodplain 

means an area bordering inland or 

coastal waters that was formed by 

sediment deposition from such water 

under present climatic conditions and is 

inundated during periods of moderate to 

high water flows. 

(v) Tributary. The term tributary 

means a water physically characterized 

by the presence of a bed and banks and 

ordinary high water mark, as defined at 

33 CFR 328.3(e), which contributes 

flow, either directly or through another 

water, to a water identified in 

paragraphs (1)(i) through (iv) of this 

definition. In addition, wetlands, lakes, 

and ponds are tributaries (even if they 

lack a bed and banks or ordinary high 

water mark) if they contribute flow, 

either directly or through another water 

to a water identified in paragraphs (1)(i) 

through (iii) of this definition. A water 

that otherwise qualifies as a tributary 

under this definition does not lose its 

status as a tributary if, for any length, 

there are one or more man-made breaks 

(such as bridges, culverts, pipes, or 

dams), or one or more natural breaks 

(such as wetlands at the head of or along 

the run of a stream, debris piles, boulder 

fields, or a stream that flows 

underground) so long as a bed and 

banks and an ordinary high water mark 

can be identified upstream of the break. 

A tributary, including wetlands, can be 

a natural, man-altered, or man-made 

water and includes waters such as 

rivers, streams, lakes, ponds, 

impoundments, canals, and ditches not 

excluded in paragraph (2)(iii) or (iv) of 

this definition. 

(6) Wetlands. The term wetlands 

means those areas that are inundated or 

saturated by surface or groundwater at 

a frequency and duration sufficient to 

support, and that under normal 

circumstances do support, a prevalence 

of vegetation typically adapted for life 

in saturated soil conditions. Wetlands 

generally include swamps, marshes, 

bogs and similar areas. 

(7) Significant nexus. The term 

significant nexus means that a water, 

including wetlands, either alone or in 

combination with other similarly 

situated waters in the region (i.e., the 

watershed that drains to the nearest 

water identified in paragraphs (1)(i) 

through (iii) of this definition), 

significantly affects the chemical, 

physical, or biological integrity of a 

water identified in paragraphs (1)(i) 

through (iii) of this definition. For an 

effect to be significant, it must be more 

than speculative or insubstantial. Other 

waters, including wetlands, are 

similarly situated when they perform 

similar functions and are located 

sufficiently close together or sufficiently 

close to a ‘‘water of the United States’’ 

so that they can be evaluated as a single 

landscape unit with regard to their 

effect on the chemical, physical, or 

biological integrity of a water identified 

in paragraphs (1)(i) through (iii) of this 

definition. 

* * * * * 

PART 116—DESIGNATION OF 

HAZARDOUS SUBSTANCE 

■ 7. The authority citation for part 116 

continues to read as follows: 

Authority: The Clean Water Act, 33 U.S.C. 

1251 et seq. 

■ 8. Section 116.3 is amended by 

revising the definition of ‘‘navigable 

waters’’ to read as follows: 

§ 116.3 Definitions. 

* * * * * 

Navigable waters is defined in section 

502(7) of the Act to mean ‘‘waters of the 

United States, including the territorial 

seas.’’ 

(1) For purposes of all sections of the 

Clean Water Act, 33 U.S.C. 1251 et seq. 

and its implementing regulations, 

subject to the exclusions in paragraph 

(2) of this definition, the term ‘‘waters 

of the United States’’ means: 

(i) All waters which are currently 

used, were used in the past, or may be 

susceptible to use in interstate or foreign 

commerce, including all waters which 

are subject to the ebb and flow of the 

tide; 

(ii) All interstate waters, including 

interstate wetlands; 

(iii) The territorial seas; 

(iv) All impoundments of waters 

identified in paragraphs (1)(i) through 

(iii) and (v) of this definition;. 


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(v) All tributaries of waters identified 

in paragraphs (1)(i) through (iv) of this 

definition; 

(vi) All waters, including wetlands, 

adjacent to a water identified in 

paragraphs (1)(i) through (v) of this 

definition; and 

(vii) On a case-specific basis, other 

waters, including wetlands, provided 

that those waters alone, or in 

combination with other similarly 

situated waters, including wetlands, 

located in the same region, have a 

significant nexus to a water identified in 

paragraphs (1)(i) through (iii) of this 

definition. 

(2) The following are not ‘‘waters of 

the United States’’ notwithstanding 

whether they meet the terms of 

paragraphs (1)(i) through (viii) of this 

definition— 

(i) Waste treatment systems, including 

treatment ponds or lagoons, designed to 

meet the requirements of the Clean 

Water Act. 

(ii) Prior converted cropland. 

Notwithstanding the determination of 

an area’s status as prior converted 

cropland by any other Federal agency, 

for the purposes of the Clean Water Act 

the final authority regarding Clean 

Water Act jurisdiction remains with 

EPA. 

(iii) Ditches that are excavated wholly 

in uplands, drain only uplands, and 

have less than perennial flow. 

(iv) Ditches that do not contribute 

flow, either directly or through another 

water, to a water identified in 

paragraphs (1)(i) through (iv) of this 

section. 

(v) The following features: 

(A) Artificially irrigated areas that 

would revert to upland should 

application of irrigation water to that 

area cease; 

(B) Artificial lakes or ponds created 

by excavating and/or diking dry land 

and used exclusively for such purposes 

as stock watering, irrigation, settling 

basins, or rice growing; 

(C) Artificial reflecting pools or 

swimming pools created by excavating 

and/or diking dry land; 

(D) Small ornamental waters created 

by excavating and/or diking dry land for 

primarily aesthetic reasons; 

(E) Water-filled depressions created 

incidental to construction activity; 

(F) Groundwater, including 

groundwater drained through 

subsurface drainage systems; and 

(G) Gullies and rills and non-wetland 

swales. 

(3) Definitions— 

(i) Adjacent. The term adjacent means 

bordering, contiguous or neighboring. 

Waters, including wetlands, separated 

from other waters of the United States 

by man-made dikes or barriers, natural 

river berms, beach dunes and the like 

are ‘‘adjacent waters.’’ 

(ii) Neighboring. The term 

neighboring, for purposes of the term 

‘‘adjacent’’ in this section, includes 

waters located within the riparian area 

or floodplain of a water identified in 

paragraphs (1)(i) through (v) of this 

definition, or waters with a shallow 

subsurface hydrologic connection or 

confined surface hydrologic connection 

to such a jurisdictional water. 

(iii) Riparian area. The term riparian 

area means an area bordering a water 

where surface or subsurface hydrology 

directly influence the ecological 

processes and plant and animal 

community structure in that area. 

Riparian areas are transitional areas 

between aquatic and terrestrial 

ecosystems that influence the exchange 

of energy and materials between those 

ecosystems. 

(4) Floodplain. The term floodplain 

means an area bordering inland or 

coastal waters that was formed by 

sediment deposition from such water 

under present climatic conditions and is 

inundated during periods of moderate to 

high water flows. 

(5) Tributary. The term tributary 

means a water physically characterized 

by the presence of a bed and banks and 

ordinary high water mark, as defined at 

33 CFR 328.3(e), which contributes 

flow, either directly or through another 

water, to a water identified in 

paragraphs (1)(i) through (iv) of this 

definition. In addition, wetlands, lakes, 

and ponds are tributaries (even if they 

lack a bed and banks or ordinary high 

water mark) if they contribute flow, 

either directly or through another water 

to a water identified in paragraphs (1)(i) 

through (iii) of this definition. A water 

that otherwise qualifies as a tributary 

under this definition does not lose its 

status as a tributary if, for any length, 

there are one or more man-made breaks 

(such as bridges, culverts, pipes, or 

dams), or one or more natural breaks 

(such as wetlands at the head of or along 

the run of a stream, debris piles, boulder 

fields, or a stream that flows 

underground) so long as a bed and 

banks and an ordinary high water mark 

can be identified upstream of the break. 

A tributary, including wetlands, can be 

a natural, man-altered, or man-made 

water and includes waters such as 

rivers, streams, lakes, ponds, 

impoundments, canals, and ditches not 

excluded in paragraph (2)(iii) or (iv) of 

this definition. 

(vi) Wetlands. The term wetlands 

means those areas that are inundated or 

saturated by surface or groundwater at 

a frequency and duration sufficient to 

support, and that under normal 

circumstances do support, a prevalence 

of vegetation typically adapted for life 

in saturated soil conditions. Wetlands 

generally include swamps, marshes, 

bogs and similar areas. 

(vii) Significant nexus. The term 

significant nexus means that a water, 

including wetlands, either alone or in 

combination with other similarly 

situated waters in the region (i.e., the 

watershed that drains to the nearest 

water identified in paragraphs (1)(i) 

through (iii) of this definition), 

significantly affects the chemical, 

physical, or biological integrity of a 

water identified in paragraphs (1)(i) 

through (iii) of this definition. For an 

effect to be significant, it must be more 

than speculative or insubstantial. Other 

waters, including wetlands, are 

similarly situated when they perform 

similar functions and are located 

sufficiently close together or sufficiently 

close to a ‘‘water of the United States’’ 

so that they can be evaluated as a single 

landscape unit with regard to their 

effect on the chemical, physical, or 

biological integrity of a water identified 

in paragraphs (1)(i) through (iii) of this 

definition. 

* * * * * 

PART 117—DETERMINATION OF 

REPORTABLE QUANTITIES FOR 

HAZARDOUS SUBSTANCES 

■ 9. The authority citation for part 117 

continues to read as follows: 

Authority: The Clean Water Act, 33 U.S.C. 

1251 et seq. 

■ 10. Section 117.1 is amended by 

revising the definition of ‘‘navigable 

waters’’ to read as follows: 

§ 117.1 Definitions. 

* * * * * 

(i) Navigable waters means ‘‘waters of 

the United States, including the 

territorial seas.’’ 

(1) For purposes of all sections of the 

Clean Water Act, 33 U.S.C. 1251 et. seq. 

and its implementing regulations, 

subject to the exclusions in paragraph 

(i)(2) of this section, the term ‘‘waters of 

the United States’’ means: 

(i) All waters which are currently 

used, were used in the past, or may be 

susceptible to use in interstate or foreign 

commerce, including all waters which 

are subject to the ebb and flow of the 

tide; 

(ii) All interstate waters, including 

interstate wetlands; 

(iii) The territorial seas; 

(iv) All impoundments of waters 

identified in paragraphs (i)(1)(i) through 

(iii) and (v) of this section; 


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(v) All tributaries of waters identified 

in paragraphs (i)(1)(i) through (iv) of this 

section; 

(vi) All waters, including wetlands, 

adjacent to a water identified in 

paragraphs (i)(1)(i) through (v) of this 

section; and 

(vii) On a case-specific basis, other 

waters, including wetlands, provided 

that those waters alone, or in 

combination with other similarly 

situated waters, including wetlands, 

located in the same region, have a 

significant nexus to a water identified in 

paragraphs (i)(1)(i) through (iii) of this 

section. 

(2) The following are not ‘‘waters of 

the United States’’ notwithstanding 

whether they meet the terms of 

paragraphs (i)(1)(i) through (vii) of this 

section— 

(i) Waste treatment systems, including 

treatment ponds or lagoons, designed to 

meet the requirements of the Clean 

Water Act. 

(ii) Prior converted cropland. 

Notwithstanding the determination of 

an area’s status as prior converted 

cropland by any other Federal agency, 

for the purposes of the Clean Water Act 

the final authority regarding Clean 

Water Act jurisdiction remains with 

EPA. 

(iii) Ditches that are excavated wholly 

in uplands, drain only uplands, and 

have less than perennial flow. 

(iv) Ditches that do not contribute 

flow, either directly or through another 

water, to a water identified in 

paragraphs (i)(1)(i) through (iv) of this 

section. 

(v) The following features: 

(A) Artificially irrigated areas that 

would revert to upland should 

application of irrigation water to that 

area cease; 

(B) Artificial lakes or ponds created 

by excavating and/or diking dry land 

and used exclusively for such purposes 

as stock watering, irrigation, settling 

basins, or rice growing; 

(C) Artificial reflecting pools or 

swimming pools created by excavating 

and/or diking dry land; 

(D) Small ornamental waters created 

by excavating and/or diking dry land for 

primarily aesthetic reasons; 

(E) Water-filled depressions created 

incidental to construction activity; 

(F) Groundwater, including 

groundwater drained through 

subsurface drainage systems; and 

(G) Gullies and rills and non-wetland 

swales. 

(3) Definitions— 

(i) Adjacent. The term adjacent means 

bordering, contiguous or neighboring. 

Waters, including wetlands, separated 

from other waters of the United States 

by man-made dikes or barriers, natural 

river berms, beach dunes and the like 

are ‘‘adjacent waters.’’ 

(ii) Neighboring. The term 

neighboring, for purposes of the term 

‘‘adjacent’’ in this section, includes 

waters located within the riparian area 

or floodplain of a water identified in 

paragraphs (i)(1)(i) through (v) of this 

section, or waters with a shallow 

subsurface hydrologic connection or 

confined surface hydrologic connection 

to such a jurisdictional water. 

(iii) Riparian area. The term riparian 

area means an area bordering a water 

where surface or subsurface hydrology 

directly influence the ecological 

processes and plant and animal 

community structure in that area. 

Riparian areas are transitional areas 

between aquatic and terrestrial 

ecosystems that influence the exchange 

of energy and materials between those 

ecosystems. 

(iv) Floodplain. The term floodplain 

means an area bordering inland or 

coastal waters that was formed by 

sediment deposition from such water 

under present climatic conditions and is 

inundated during periods of moderate to 

high water flows. 

(v) Tributary. The term tributary 

means a water physically characterized 

by the presence of a bed and banks and 

ordinary high water mark, as defined at 

33 CFR 328.3(e), which contributes 

flow, either directly or through another 

water, to a water identified in 

paragraphs (i)(1)(i) through (iv) of this 

section. In addition, wetlands, lakes, 

and ponds are tributaries (even if they 

lack a bed and banks or ordinary high 

water mark) if they contribute flow, 

either directly or through another water 

to a water identified in paragraphs 

(i)(1)(i) through (iii) of this section. A 

water that otherwise qualifies as a 

tributary under this definition does not 

lose its status as a tributary if, for any 

length, there are one or more man-made 

breaks (such as bridges, culverts, pipes, 

or dams), or one or more natural breaks 

(such as wetlands at the head of or along 

the run of a stream, debris piles, boulder 

fields, or a stream that flows 

underground) so long as a bed and 

banks and an ordinary high water mark 

can be identified upstream of the break. 

A tributary, including wetlands, can be 

a natural, man-altered, or man-made 

water and includes waters such as 

rivers, streams, lakes, ponds, 

impoundments, canals, and ditches not 

excluded in paragraph (i)(2)(iii) or (iv) 

of this section. 

(vi) Wetlands. The term wetlands 

means those areas that are inundated or 

saturated by surface or groundwater at 

a frequency and duration sufficient to 

support, and that under normal 

circumstances do support, a prevalence 

of vegetation typically adapted for life 

in saturated soil conditions. Wetlands 

generally include swamps, marshes, 

bogs and similar areas. 

(vii) Significant nexus. The term 

significant nexus means that a water, 

including wetlands, either alone or in 

combination with other similarly 

situated waters in the region (i.e., the 

watershed that drains to the nearest 

water identified in paragraphs (i)(1)(i) 

through (iii) of this section), 

significantly affects the chemical, 

physical, or biological integrity of a 

water identified in paragraphs (i)(1)(i) 

through (iii) of this section. For an effect 

to be significant, it must be more than 

speculative or insubstantial. Other 

waters, including wetlands, are 

similarly situated when they perform 

similar functions and are located 

sufficiently close together or sufficiently 

close to a ‘‘water of the United States’’ 

so that they can be evaluated as a single 

landscape unit with regard to their 

effect on the chemical, physical, or 

biological integrity of a water identified 

in paragraphs (i)(1)(i) through (iii) of 

this section. 

* * * * * 

PART 122—EPA ADMINISTERED 

PERMIT PROGRAMS: THE NATIONAL 

POLLUTANT DISCHARGE 

ELIMINATION SYSTEM 

■ 11. The authority citation for part 122 

continues to read as follows: 

Authority: The Clean Water Act, 33 U.S.C. 

1251 et seq. 

■ 12. Section 122.2 is amended by 

revising the definition of ‘‘Waters of the 

United States’’ and removing the note 

and editorial note at the end of the 

section. 

The revision reads as follows: 

§ 122.2 Definitions. 

* * * * * 

Waters of the United States or waters 

of the U.S. means: 

(a) For purposes of all sections of the 

Clean Water Act, 33 U.S.C. 1251 et seq. 

and its implementing regulations, 

subject to the exclusions in paragraph 

(b) of this definition, the term ‘‘waters 

of the United States’’ means: 

(1) All waters which are currently 

used, were used in the past, or may be 

susceptible to use in interstate or foreign 

commerce, including all waters which 

are subject to the ebb and flow of the 

tide; 

(2) All interstate waters, including 

interstate wetlands; 

(3) The territorial seas; 


emcdonald on DSK67QTVN1PROD with PROPOSALS2
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(4) All impoundments of waters 

identified in paragraphs (a)(1) through 

(3) and (5) of this definition; 

(5) All tributaries of waters identified 

in paragraphs (a)(1) through (4) of this 

definition; 

(6) All waters, including wetlands, 

adjacent to a water identified in 

paragraphs (a)(1) through (5) of this 

definition; and 

(7) On a case-specific basis, other 

waters, including wetlands, provided 

that those waters alone, or in 

combination with other similarly 

situated waters, including wetlands, 

located in the same region, have a 

significant nexus to a water identified in 

paragraphs (a)(1) through (3) of this 

definition. 

(b) The following are not ‘‘waters of 

the United States’’ notwithstanding 

whether they meet the terms of 

paragraphs (a)(1) through (7) of this 

definition— 

(1) Waste treatment systems, 

including treatment ponds or lagoons, 

designed to meet the requirements of 

the Clean Water Act. This exclusion 

applies only to manmade bodies of 

water which neither were originally 

created in waters of the United States 

(such as disposal area in wetlands) nor 

resulted from the impoundment of 

waters of the United States.1

(2) Prior converted cropland. 

Notwithstanding the determination of 

an area’s status as prior converted 

cropland by any other Federal agency, 

for the purposes of the Clean Water Act 

the final authority regarding Clean 

Water Act jurisdiction remains with 

EPA. 

(3) Ditches that are excavated wholly 

in uplands, drain only uplands, and 

have less than perennial flow. 

(4) Ditches that do not contribute 

flow, either directly or through another 

water, to a water identified in 

paragraphs (a)(1) through (4) of this 

definition. 

(5) The following features: 

(i) Artificially irrigated areas that 

would revert to upland should 

application of irrigation water to that 

area cease; 

(ii) Artificial lakes or ponds created 

by excavating and/or diking dry land 

and used exclusively for such purposes 

as stock watering, irrigation, settling 

basins, or rice growing; 

(iii) Artificial reflecting pools or 

swimming pools created by excavating 

and/or diking dry land; 

(iv) Small ornamental waters created 

by excavating and/or diking dry land for 

primarily aesthetic reasons; 

(v) Water-filled depressions created 

incidental to construction activity; 

(vi) Groundwater, including 

groundwater drained through 

subsurface drainage systems; and 

(vii) Gullies and rills and non-wetland 

swales. 

(c) Definitions— 

(1) Adjacent. The term adjacent 

means bordering, contiguous or 

neighboring. Waters, including 

wetlands, separated from other waters of 

the United States by man-made dikes or 

barriers, natural river berms, beach 

dunes and the like are ‘‘adjacent 

waters.’’ 

(2) Neighboring. The term 

neighboring, for purposes of the term 

‘‘adjacent’’ in this section, includes 

waters located within the riparian area 

or floodplain of a water identified in 

paragraphs (a)(1) through (5) of this 

section, or waters with a shallow 

subsurface hydrologic connection or 

confined surface hydrologic connection 

to such a jurisdictional water. 

(3) Riparian area. The term riparian 

area means an area bordering a water 

where surface or subsurface hydrology 

directly influence the ecological 

processes and plant and animal 

community structure in that area. 

Riparian areas are transitional areas 

between aquatic and terrestrial 

ecosystems that influence the exchange 

of energy and materials between those 

ecosystems. 

(4) Floodplain. The term floodplain 

means an area bordering inland or 

coastal waters that was formed by 

sediment deposition from such water 

under present climatic conditions and is 

inundated during periods of moderate to 

high water flows. 

(5) Tributary. The term tributary 

means a water physically characterized 

by the presence of a bed and banks and 

ordinary high water mark, as defined at 

33 CFR 328.3(e), which contributes 

flow, either directly or through another 

water, to a water identified in 

paragraphs (a)(1) through (4) of this 

definition. In addition, wetlands, lakes, 

and ponds are tributaries (even if they 

lack a bed and banks or ordinary high 

water mark) if they contribute flow, 

either directly or through another water 

to a water identified in paragraphs (a)(1) 

through (3) of this definition. A water 

that otherwise qualifies as a tributary 

under this definition does not lose its 

status as a tributary if, for any length, 

there are one or more man-made breaks 

(such as bridges, culverts, pipes, or 

dams), or one or more natural breaks 

(such as wetlands at the head of or along 

the run of a stream, debris piles, boulder 

fields, or a stream that flows 

underground) so long as a bed and 

banks and an ordinary high water mark 

can be identified upstream of the break. 

A tributary, including wetlands, can be 

a natural, man-altered, or man-made 

water and includes waters such as 

rivers, streams, lakes, ponds, 

impoundments, canals, and ditches not 

excluded in paragraphs (b)(3) or (4) of 

this definition. 

(6) Wetlands. The term wetlands 

means those areas that are inundated or 

saturated by surface or groundwater at 

a frequency and duration sufficient to 

support, and that under normal 

circumstances do support, a prevalence 

of vegetation typically adapted for life 

in saturated soil conditions. Wetlands 

generally include swamps, marshes, 

bogs and similar areas. 

(7) Significant nexus. The term 

significant nexus means that a water, 

including wetlands, either alone or in 

combination with other similarly 

situated waters in the region (i.e., the 

watershed that drains to the nearest 

water identified in paragraphs (a)(1) 

through (3) of this definition), 

significantly affects the chemical, 

physical, or biological integrity of a 

water identified in paragraphs (a)(1) 

through (3) of this definition. For an 

effect to be significant, it must be more 

than speculative or insubstantial. Other 

waters, including wetlands, are 

similarly situated when they perform 

similar functions and are located 

sufficiently close together or sufficiently 

close to a ‘‘water of the United States’’ 

so that they can be evaluated as a single 

landscape unit with regard to their 

effect on the chemical, physical, or 

biological integrity of a water identified 

in paragraphs (a)(1) through (3) of this 

definition. 

* * * * * 1At 45 FR 48620, July 21, 1980, the 

Environmental Protection Agency 

suspended until further notice in 

§ 122.2, the last sentence, beginning 

‘‘This exclusion applies . . .’’ in the 

definition of ‘‘Waters of the United 

States.’’ This revision (48 FR 14153, 

Apr. 1, 1983) continues that suspension. 

PART 230—SECTION 404(b)(1) 

GUIDELINES FOR SPECIFICATION OF 

DISPOSAL SITES FOR DREDGED OR 

FILL MATERIAL 

■ 13. The authority citation for part 230 

continues to read as follows: 

Authority: The Clean Water Act, 33 U.S.C. 

1251 et seq. 

■ 14. Section 230.3 is amended by 

revising paragraphs (s) and (t) and 

adding paragraph (u) to read as follows: 

§ 230.3 Definitions. 

* * * * * 

(s) For purposes of all sections of the 

Clean Water Act, 33 U.S.C. 1251 et seq. 


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and its implementing regulations, 

subject to the exclusions in paragraph (t) 

of this section, the term ‘‘waters of the 

United States’’ means: 

(1) All waters which are currently 

used, were used in the past, or may be 

susceptible to use in interstate or foreign 

commerce, including all waters which 

are subject to the ebb and flow of the 

tide; 

(2) All interstate waters, including 

interstate wetlands; 

(3) The territorial seas; 

(4) All impoundments of waters 

identified in paragraphs (s)(1) through 

(3) and (5) of this section; 

(5) All tributaries of waters identified 

in paragraphs (s)(1) through (4) of this 

section; 

(6) All waters, including wetlands, 

adjacent to a water identified in 

paragraphs (s)(1) through (5) of this 

section; and 

(7) On a case-specific basis, other 

waters, including wetlands, provided 

that those waters alone, or in 

combination with other similarly 

situated waters, including wetlands, 

located in the same region, have a 

significant nexus to a water identified in 

paragraphs (s)(1) through (3) of this 

section. 

(t) The following are not ‘‘waters of 

the United States’’ notwithstanding 

whether they meet the terms of 

paragraphs (s)(1) through (7) of this 

section— 

(1) Waste treatment systems, 

including treatment ponds or lagoons, 

designed to meet the requirements of 

the Clean Water Act. 

(2) Prior converted cropland. 

Notwithstanding the determination of 

an area’s status as prior converted 

cropland by any other Federal agency, 

for the purposes of the Clean Water Act 

the final authority regarding Clean 

Water Act jurisdiction remains with 

EPA. 

(3) Ditches that are excavated wholly 

in uplands, drain only uplands, and 

have less than perennial flow. 

(4) Ditches that do not contribute 

flow, either directly or through another 

water, to a water identified in 

paragraphs (s)(1) through (4) of this 

section. 

(5) The following features: 

(i) Artificially irrigated areas that 

would revert to upland should 

application of irrigation water to that 

area cease; 

(ii) Artificial lakes or ponds created 

by excavating and/or diking dry land 

and used exclusively for such purposes 

as stock watering, irrigation, settling 

basins, or rice growing; 

(iii) Artificial reflecting pools or 

swimming pools created by excavating 

and/or diking dry land; 

(iv) Small ornamental waters created 

by excavating and/or diking dry land for 

primarily aesthetic reasons; 

(v) Water-filled depressions created 

incidental to construction activity; 

(vi) Groundwater, including 

groundwater drained through 

subsurface drainage systems; and 

(vii) Gullies and rills and non-wetland 

swales. 

(u) Definitions— 

(1) Adjacent. The term adjacent 

means bordering, contiguous or 

neighboring. Waters, including 

wetlands, separated from other waters of 

the United States by man-made dikes or 

barriers, natural river berms, beach 

dunes and the like are ‘‘adjacent 

waters.’’ 

(2) Neighboring. The term 

neighboring, for purposes of the term 

‘‘adjacent’’ in this section, includes 

waters located within the riparian area 

or floodplain of a water identified in 

paragraphs (s)(1) through (5) of this 

section, or waters with a shallow 

subsurface hydrologic connection or 

confined surface hydrologic connection 

to such a jurisdictional water. 

(3) Riparian area. The term riparian 

area means an area bordering a water 

where surface or subsurface hydrology 

directly influence the ecological 

processes and plant and animal 

community structure in that area. 

Riparian areas are transitional areas 

between aquatic and terrestrial 

ecosystems that influence the exchange 

of energy and materials between those 

ecosystems. 

(4) Floodplain. The term floodplain 

means an area bordering inland or 

coastal waters that was formed by 

sediment deposition from such water 

under present climatic conditions and is 

inundated during periods of moderate to 

high water flows. 

(5) Tributary. The term tributary 

means a water physically characterized 

by the presence of a bed and banks and 

ordinary high water mark, as defined at 

33 CFR 328.3(e), which contributes 

flow, either directly or through another 

water, to a water identified in 

paragraphs (s)(1) through (4) of this 

section. In addition, wetlands, lakes, 

and ponds are tributaries (even if they 

lack a bed and banks or ordinary high 

water mark) if they contribute flow, 

either directly or through another water 

to a water identified in paragraphs (s)(1) 

through (3) of this section. A water that 

otherwise qualifies as a tributary under 

this definition does not lose its status as 

a tributary if, for any length, there are 

one or more man-made breaks (such as 

bridges, culverts, pipes, or dams), or one 

or more natural breaks (such as 

wetlands at the head of or along the run 

of a stream, debris piles, boulder fields, 

or a stream that flows underground) so 

long as a bed and banks and an ordinary 

high water mark can be identified 

upstream of the break. A tributary, 

including wetlands, can be a natural, 

man-altered, or man-made water and 

includes waters such as rivers, streams, 

lakes, ponds, impoundments, canals, 

and ditches not excluded in paragraph 

(t)(3) or (4) of this section. 

(6) Wetlands. The term wetlands 

means those areas that are inundated or 

saturated by surface or groundwater at 

a frequency and duration sufficient to 

support, and that under normal 

circumstances do support, a prevalence 

of vegetation typically adapted for life 

in saturated soil conditions. Wetlands 

generally include swamps, marshes, 

bogs and similar areas. 

(7) Significant nexus. The term 

significant nexus means that a water, 

including wetlands, either alone or in 

combination with other similarly 

situated waters in the region (i.e., the 

watershed that drains to the nearest 

water identified in paragraphs (s)(1) 

through (3) of this section), significantly 

affects the chemical, physical, or 

biological integrity of a water identified 

in paragraphs (s)(1) through (3) of this 

section. For an effect to be significant, 

it must be more than speculative or 

insubstantial. Other waters, including 

wetlands, are similarly situated when 

they perform similar functions and are 

located sufficiently close together or 

sufficiently close to a ‘‘water of the 

United States’’ so that they can be 

evaluated as a single landscape unit 

with regard to their effect on the 

chemical, physical, or biological 

integrity of a water identified in 

paragraphs (s)(1) through (3) of this 

section. 

PART 232—404 PROGRAMS 

DEFINITIONS; EXEMPT ACTIVITIES 

NOT REQUIRING 404 PERMITS 

■ 15. The authority citation for part 232 

continues to read as follows: 

Authority: The Clean Water Act, 33 U.S.C. 

1251 et seq. 

■ 16. Section 232.2 is amended by 

revising the definition of ‘‘Waters of the 

United States’’ to read as follows: 

§ 232.2 Definitions, 

* * * * * 

Waters of the United States or waters 

means: 

(1) For purposes of all sections of the 

Clean Water Act, 33 U.S.C. 1251 et. seq. 

and its implementing regulations, 

subject to the exclusions in paragraph 

(2) of this definition, the term ‘‘waters 

of the United States’’ means: 


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(i) All waters which are currently 

used, were used in the past, or may be 

susceptible to use in interstate or foreign 

commerce, including all waters which 

are subject to the ebb and flow of the 

tide; 

(ii) All interstate waters, including 

interstate wetlands; 

(iii) The territorial seas; 

(iv) All impoundments of waters 

identified in paragraphs (1)(i) through 

(iii) and (v) of this definition; 

(v) All tributaries of waters identified 

in paragraphs (1)(i) through (iv) of this 

section; 

(vi) All waters, including wetlands, 

adjacent to a water identified in 

paragraphs (1)(i) through (v) of this 

definition; and 

(vii) On a case-specific basis, other 

waters, including wetlands, provided 

that those waters alone, or in 

combination with other similarly 

situated waters, including wetlands, 

located in the same region, have a 

significant nexus to a water identified in 

paragraphs (1)(i) through (iii) of this 

definition. 

(2) The following are not ‘‘waters of 

the United States’’ notwithstanding 

whether they meet the terms of 

paragraphs (1)(i) through (vii) of this 

definition— 

(i) Waste treatment systems, including 

treatment ponds or lagoons, designed to 

meet the requirements of the Clean 

Water Act. 

(ii) Prior converted cropland. 

Notwithstanding the determination of 

an area’s status as prior converted 

cropland by any other Federal agency, 

for the purposes of the Clean Water Act 

the final authority regarding Clean 

Water Act jurisdiction remains with 

EPA. 

(iii) Ditches that are excavated wholly 

in uplands, drain only uplands, and 

have less than perennial flow. 

(iv) Ditches that do not contribute 

flow, either directly or through another 

water, to a water identified in 

paragraphs (1)(i) through (iv) of this 

section. 

(v) The following features: 

(A) Artificially irrigated areas that 

would revert to upland should 

application of irrigation water to that 

area cease; 

(B) Artificial lakes or ponds created 

by excavating and/or diking dry land 

and used exclusively for such purposes 

as stock watering, irrigation, settling 

basins, or rice growing; 

(C) Artificial reflecting pools or 

swimming pools created by excavating 

and/or diking dry land; 

(D) Small ornamental waters created 

by excavating and/or diking dry land for 

primarily aesthetic reasons; 

(E) Water-filled depressions created 

incidental to construction activity; 

(F) Groundwater, including 

groundwater drained through 

subsurface drainage systems; and 

(G) Gullies and rills and non-wetland 

swales. 

(3) Definitions— 

(i) Adjacent. The term adjacent means 

bordering, contiguous or neighboring. 

Waters, including wetlands, separated 

from other waters of the United States 

by man-made dikes or barriers, natural 

river berms, beach dunes and the like 

are ‘‘adjacent waters.’’ 

(ii) Neighboring. The term 

neighboring, for purposes of the term 

‘‘adjacent’’ in this section, includes 

waters located within the riparian area 

or floodplain of a water identified in 

paragraphs (1)(i) through (v) of this 

definition, or waters with a shallow 

subsurface hydrologic connection or 

confined surface hydrologic connection 

to such a jurisdictional water. 

(iii) Riparian area. The term riparian 

area means an area bordering a water 

where surface or subsurface hydrology 

directly influence the ecological 

processes and plant and animal 

community structure in that area. 

Riparian areas are transitional areas 

between aquatic and terrestrial 

ecosystems that influence the exchange 

of energy and materials between those 

ecosystems. 

(iv) Floodplain. The term floodplain 

means an area bordering inland or 

coastal waters that was formed by 

sediment deposition from such water 

under present climatic conditions and is 

inundated during periods of moderate to 

high water flows. 

(v) Tributary. The term tributary 

means a water physically characterized 

by the presence of a bed and banks and 

ordinary high water mark, as defined at 

33 CFR 328.3(e), which contributes 

flow, either directly or through another 

water, to a water identified in 

paragraphs (1)(i) through (iv) of this 

definition. In addition, wetlands, lakes, 

and ponds are tributaries (even if they 

lack a bed and banks or ordinary high 

water mark) if they contribute flow, 

either directly or through another water 

to a water identified in paragraphs (1)(i) 

through (iii) of this definition. A water 

that otherwise qualifies as a tributary 

under this definition does not lose its 

status as a tributary if, for any length, 

there are one or more man-made breaks 

(such as bridges, culverts, pipes, or 

dams), or one or more natural breaks 

(such as wetlands at the head of or along 

the run of a stream, debris piles, boulder 

fields, or a stream that flows 

underground) so long as a bed and 

banks and an ordinary high water mark 

can be identified upstream of the break. 

A tributary, including wetlands, can be 

a natural, man-altered, or man-made 

water and includes waters such as 

rivers, streams, lakes, ponds, 

impoundments, canals, and ditches not 

excluded in paragraph (2)(iii) or (iv) of 

this definition. 

(vi) Wetlands. The term wetlands 

means those areas that are inundated or 

saturated by surface or groundwater at 

a frequency and duration sufficient to 

support, and that under normal 

circumstances do support, a prevalence 

of vegetation typically adapted for life 

in saturated soil conditions. Wetlands 

generally include swamps, marshes, 

bogs and similar areas. 

(vii) Significant nexus. The term 

significant nexus means that a water, 

including wetlands, either alone or in 

combination with other similarly 

situated waters in the region (i.e., the 

watershed that drains to the nearest 

water identified in paragraphs (1)(i) 

through (iii) of this definition), 

significantly affects the chemical, 

physical, or biological integrity of a 

water identified in paragraphs (1)(i) 

through (iii) of this definition. For an 

effect to be significant, it must be more 

than speculative or insubstantial. Other 

waters, including wetlands, are 

similarly situated when they perform 

similar functions and are located 

sufficiently close together or sufficiently 

close to a ‘‘water of the United States’’ 

so that they can be evaluated as a single 

landscape unit with regard to their 

effect on the chemical, physical, or 

biological integrity of a water identified 

in paragraphs (1)(i) through (iii) of this 

definition. 

PART 300—NATIONAL OIL AND 

HAZARDOUS SUBSTANCES 

POLLUTION CONTINGENCY PLAN 

■ 17. The authority citation for part 300 

continues to read as follows: 

Authority: The Clean Water Act, 33 U.S.C. 

1251 et seq. 

■ 18. Section 300.5 is amended by 

revising the definition of ‘‘navigable 

waters’’ to read as follows: 

§ 300.5 Definitions. 

* * * * * 

Navigable waters as defined by 40 

CFR 110.1, means the waters of the 

United States, including the territorial 

seas. 

(1) For purposes of all sections of the 

Clean Water Act, 33 U.S.C. 1251 et seq. 

and its implementing regulations, 

subject to the exclusions in paragraph 

(2) of this definition, the term ‘‘waters 

of the United States’’ means: 


emcdonald on DSK67QTVN1PROD with PROPOSALS2
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(i) All waters which are currently 

used, were used in the past, or may be 

susceptible to use in interstate or foreign 

commerce, including all waters which 

are subject to the ebb and flow of the 

tide; 

(ii) All interstate waters, including 

interstate wetlands; 

(iii) The territorial seas; 

(iv) All impoundments of waters 

identified in paragraphs (1)(i) through 

(iii) and (v) of this definition; 

(v) All tributaries of waters identified 

in paragraphs (1)(i) through (iv) of this 

definition; 

(vi) All waters, including wetlands, 

adjacent to a water identified in 

paragraphs (1)(i) through (v) of this 

definition; and 

(vii) On a case-specific basis, other 

waters, including wetlands, provided 

that those waters alone, or in 

combination with other similarly 

situated waters, including wetlands, 

located in the same region, have a 

significant nexus to a water identified in 

paragraphs (1)(i) through (iii) of this 

definition. 

(2) The following are not ‘‘waters of 

the United States’’ notwithstanding 

whether they meet the terms of 

paragraphs (1)(i) through (vii) of this 

definition— 

(i) Waste treatment systems, including 

treatment ponds or lagoons, designed to 

meet the requirements of the Clean 

Water Act. 

(ii) Prior converted cropland. 

Notwithstanding the determination of 

an area’s status as prior converted 

cropland by any other Federal agency, 

for the purposes of the Clean Water Act 

the final authority regarding Clean 

Water Act jurisdiction remains with 

EPA. 

(iii) Ditches that are excavated wholly 

in uplands, drain only uplands, and 

have less than perennial flow. 

(iv) Ditches that do not contribute 

flow, either directly or through another 

water, to a water identified in 

paragraphs (1)(i) through (iv) of this 

definition. 

(v) The following features: 

(A) Artificially irrigated areas that 

would revert to upland should 

application of irrigation water to that 

area cease; 

(B) Artificial lakes or ponds created 

by excavating and/or diking dry land 

and used exclusively for such purposes 

as stock watering, irrigation, settling 

basins, or rice growing; 

(C) Artificial reflecting pools or 

swimming pools created by excavating 

and/or diking dry land; 

(D) Small ornamental waters created 

by excavating and/or diking dry land for 

primarily aesthetic reasons; 

(E) Water-filled depressions created 

incidental to construction activity; 

(F) Groundwater, including 

groundwater drained through 

subsurface drainage systems; and 

(G) Gullies and rills and non-wetland 

swales. 

(3) Definitions— 

(i) Adjacent. The term adjacent means 

bordering, contiguous or neighboring. 

Waters, including wetlands, separated 

from other waters of the United States 

by man-made dikes or barriers, natural 

river berms, beach dunes and the like 

are ‘‘adjacent waters.’’ 

(ii) Neighboring. The term 

neighboring, for purposes of the term 

‘‘adjacent’’ in this section, includes 

waters located within the riparian area 

or floodplain of a water identified in 

paragraphs (1)(i) through (v) of this 

definition, or waters with a shallow 

subsurface hydrologic connection or 

confined surface hydrologic connection 

to such a jurisdictional water. 

(iii) Riparian area. The term riparian 

area means an area bordering a water 

where surface or subsurface hydrology 

directly influence the ecological 

processes and plant and animal 

community structure in that area. 

Riparian areas are transitional areas 

between aquatic and terrestrial 

ecosystems that influence the exchange 

of energy and materials between those 

ecosystems. 

(iv) Floodplain. The term floodplain 

means an area bordering inland or 

coastal waters that was formed by 

sediment deposition from such water 

under present climatic conditions and is 

inundated during periods of moderate to 

high water flows. 

(v) Tributary. The term tributary 

means a water physically characterized 

by the presence of a bed and banks and 

ordinary high water mark, as defined at 

33 CFR 328.3(e), which contributes 

flow, either directly or through another 

water, to a water identified in 

paragraphs (1)(i) through (iv) of this 

definition. In addition, wetlands, lakes, 

and ponds are tributaries (even if they 

lack a bed and banks or ordinary high 

water mark) if they contribute flow, 

either directly or through another water 

to a water identified in paragraphs (1)(i) 

through (iii) of this definition. A water 

that otherwise qualifies as a tributary 

under this definition does not lose its 

status as a tributary if, for any length, 

there are one or more man-made breaks 

(such as bridges, culverts, pipes, or 

dams), or one or more natural breaks 

(such as wetlands at the head of or along 

the run of a stream, debris piles, boulder 

fields, or a stream that flows 

underground) so long as a bed and 

banks and an ordinary high water mark 

can be identified upstream of the break. 

A tributary, including wetlands, can be 

a natural, man-altered, or man-made 

water and includes waters such as 

rivers, streams, lakes, ponds, 

impoundments, canals, and ditches not 

excluded in paragraph (2)(iii) or (iv) of 

this definition. 

(vi) Wetlands. The term wetlands 

means those areas that are inundated or 

saturated by surface or groundwater at 

a frequency and duration sufficient to 

support, and that under normal 

circumstances do support, a prevalence 

of vegetation typically adapted for life 

in saturated soil conditions. Wetlands 

generally include swamps, marshes, 

bogs and similar areas. 

(vii) Significant nexus. The term 

significant nexus means that a water, 

including wetlands, either alone or in 

combination with other similarly 

situated waters in the region (i.e., the 

watershed that drains to the nearest 

water identified in paragraphs (1)(i) 

through (iii) of this definition), 

significantly affects the chemical, 

physical, or biological integrity of a 

water identified in paragraphs (1)(i) 

through (iii) of this definition. For an 

effect to be significant, it must be more 

than speculative or insubstantial. Other 

waters, including wetlands, are 

similarly situated when they perform 

similar functions and are located 

sufficiently close together or sufficiently 

close to a ‘‘water of the United States’’ 

so that they can be evaluated as a single 

landscape unit with regard to their 

effect on the chemical, physical, or 

biological integrity of a water identified 

in paragraphs (1)(i) through (iii) of this 

definition. 

* * * * * 

■ 19. In appendix E to part 300, section 

1.5 Definitions is amended by revising 

the definition of ‘‘navigable waters’’ to 

read as follows: 

Appendix E to Part 300—Oil Spill 

Response. 

1.5 Definitions. * * * 

Navigable waters as defined by 40 CFR 

110.1, means the waters of the United States, 

including the territorial seas. 

(1) For purposes of all sections of the Clean 

Water Act, 33 U.S.C. 1251 et seq. and its 

implementing regulations, subject to the 

exclusions in paragraph (2) of this definition, 

the term ‘‘waters of the United States’’ 

means: 

(i) All waters which are currently used, 

were used in the past, or may be susceptible 

to use in interstate or foreign commerce, 

including all waters which are subject to the 

ebb and flow of the tide; 

(ii) All interstate waters, including 

interstate wetlands; 

(iii) The territorial seas; 


emcdonald on DSK67QTVN1PROD with PROPOSALS2
22272 Federal Register / Vol. 79, No. 76 / Monday, April 21, 2014 / Proposed Rules 

(iv) All impoundments of waters identified 

in paragraphs (1)(i) through (iii) and (v) of 

this definition; 

(v) All tributaries of waters identified in 

paragraphs (1)(i) through (iv) of this 

definition; 

(vi) All waters, including wetlands, 

adjacent to a water identified in paragraphs 

(1)(i) through (v) of this definition; and 

(vii) On a case-specific basis, other waters, 

including wetlands, provided that those 

waters alone, or in combination with other 

similarly situated waters, including 

wetlands, located in the same region, have a 

significant nexus to a water identified in 

paragraphs (1)(i) through (iii) of this 

definition. 

(2) The following are not ‘‘waters of the 

United States’’ notwithstanding whether they 

meet the terms of paragraphs (1)(i) through 

(vii) of this definition— 

(i) Waste treatment systems, including 

treatment ponds or lagoons, designed to meet 

the requirements of the Clean Water Act. 

(ii) Prior converted cropland. 

Notwithstanding the determination of an 

area’s status as prior converted cropland by 

any other Federal agency, for the purposes of 

the Clean Water Act the final authority 

regarding Clean Water Act jurisdiction 

remains with EPA. 

(iii) Ditches that are excavated wholly in 

uplands, drain only uplands, and have less 

than perennial flow. 

(iv) Ditches that do not contribute flow, 

either directly or through another water, to a 

water identified in paragraphs (1)(i) through 

(iv) of this definition. 

(v) The following features: 

(A) Artificially irrigated areas that would 

revert to upland should application of 

irrigation water to that area cease; 

(B) Artificial lakes or ponds created by 

excavating and/or diking dry land and used 

exclusively for such purposes as stock 

watering, irrigation, settling basins, or rice 

growing; 

(C) Artificial reflecting pools or swimming 

pools created by excavating and/or diking 

dry land; 

(D) Small ornamental waters created by 

excavating and/or diking dry land for 

primarily aesthetic reasons; 

(E) Water-filled depressions created 

incidental to construction activity; 

(F) Groundwater, including groundwater 

drained through subsurface drainage systems; 

and 

(G) Gullies and rills and non-wetland 

swales. 

(3) Definitions— 

(i) Adjacent. The term adjacent means 

bordering, contiguous or neighboring. 

Waters, including wetlands, separated from 

other waters of the United States by manmade dikes or barriers, natural river berms, 

beach dunes and the like are ‘‘adjacent 

waters.’’ 

(ii) Neighboring. The term neighboring, for 

purposes of the term ‘‘adjacent’’ in this 

section, includes waters located within the 

riparian area or floodplain of a water 

identified in paragraphs (1)(i) through (v) of 

this definition, or waters with a shallow 

subsurface hydrologic connection or 

confined surface hydrologic connection to 

such a jurisdictional water. 

(iii) Riparian area. The term riparian area 

means an area bordering a water where 

surface or subsurface hydrology directly 

influence the ecological processes and plant 

and animal community structure in that area. 

Riparian areas are transitional areas between 

aquatic and terrestrial ecosystems that 

influence the exchange of energy and 

materials between those ecosystems. 

(iv) Floodplain. The term floodplain means 

an area bordering inland or coastal waters 

that was formed by sediment deposition from 

such water under present climatic conditions 

and is inundated during periods of moderate 

to high water flows. 

(v) Tributary. The term tributary means a 

water physically characterized by the 

presence of a bed and banks and ordinary 

high water mark, as defined at 33 CFR 

328.3(e), which contributes flow, either 

directly or through another water, to a water 

identified in paragraphs (1)(i) through (iv) of 

this definition. In addition, wetlands, lakes, 

and ponds are tributaries (even if they lack 

a bed and banks or ordinary high water mark) 

if they contribute flow, either directly or 

through another water to a water identified 

in paragraphs (1)(i) through (iii) of this 

definition. A water that otherwise qualifies as 

a tributary under this definition does not lose 

its status as a tributary if, for any length, 

there are one or more man-made breaks (such 

as bridges, culverts, pipes, or dams), or one 

or more natural breaks (such as wetlands at 

the head of or along the run of a stream, 

debris piles, boulder fields, or a stream that 

flows underground) so long as a bed and 

banks and an ordinary high water mark can 

be identified upstream of the break. A 

tributary, including wetlands, can be a 

natural, man-altered, or man-made water and 

includes waters such as rivers, streams, lakes, 

ponds, impoundments, canals, and ditches 

not excluded in paragraph (2)(iii) or (iv) of 

this definition. 

(vi) Wetlands. The term wetlands means 

those areas that are inundated or saturated by 

surface or groundwater at a frequency and 

duration sufficient to support, and that under 

normal circumstances do support, a 

prevalence of vegetation typically adapted for 

life in saturated soil conditions. Wetlands 

generally include swamps, marshes, bogs and 

similar areas. 

(vii) Significant nexus. The term significant 

nexus means that a water, including 

wetlands, either alone or in combination 

with other similarly situated waters in the 

region (i.e., the watershed that drains to the 

nearest water identified in paragraphs (1)(i) 

through (iii) of this definition), significantly 

affects the chemical, physical, or biological 

integrity of a water identified in paragraphs 

(1)(i) through (iii) of this definition. For an 

effect to be significant, it must be more than 

speculative or insubstantial. Other waters, 

including wetlands, are similarly situated 

when they perform similar functions and are 

located sufficiently close together or 

sufficiently close to a ‘‘water of the United 

States’’ so that they can be evaluated as a 

single landscape unit with regard to their 

effect on the chemical, physical, or biological 

integrity of a water identified in paragraphs 

(1)(i) through (iii) of this definition. 

* * * * * 

PART 302—DESIGNATION, 

REPORTABLE QUANTITIES, AND 

NOTIFICATION 

■ 20. The authority citation for part 302 

continues to read as follows: 

Authority: The Clean Water Act, 33 U.S.C. 

1251 et seq. 

■ 21. Section 302.3 is amended by 

revising the definition of ‘‘navigable 

waters’’ to read as follows: 

§ 302.3 Definitions. 

* * * * * 

Navigable waters means the waters of 

the United States, including the 

territorial seas. 

(1) For purposes of all sections of the 

Clean Water Act, 33 U.S.C. 1251 et. seq. 

and its implementing regulations, 

subject to the exclusions in paragraph 

(2) of this definition, the term ‘‘waters 

of the United States’’ means: 

(i) All waters which are currently 

used, were used in the past, or may be 

susceptible to use in interstate or foreign 

commerce, including all waters which 

are subject to the ebb and flow of the 

tide; 

(ii) All interstate waters, including 

interstate wetlands; 

(iii) The territorial seas; 

(iv) All impoundments of waters 

identified in paragraphs (1)(i) through 

(iii) and (v) of this definition; 

(v) All tributaries of waters identified 

in paragraphs (1)(i) through (iv) of this 

definition; 

(vi) All waters, including wetlands, 

adjacent to a water identified in 

paragraphs (1)(i) through (v) of this 

definition; and 

(vii) On a case-specific basis, other 

waters, including wetlands, provided 

that those waters alone, or in 

combination with other similarly 

situated waters, including wetlands, 

located in the same region, have a 

significant nexus to a water identified in 

paragraphs (1)(i) through (iii) of this 

definition. 

(2) The following are not ‘‘waters of 

the United States’’ notwithstanding 

whether they meet the terms of 

paragraphs (1)(i) through (vii) of this 

definition— 

(i) Waste treatment systems, including 

treatment ponds or lagoons, designed to 

meet the requirements of the Clean 

Water Act. 

(ii) Prior converted cropland. 

Notwithstanding the determination of 

an area’s status as prior converted 

cropland by any other Federal agency, 

for the purposes of the Clean Water Act 

the final authority regarding Clean 

Water Act jurisdiction remains with 

EPA. 


emcdonald on DSK67QTVN1PROD with PROPOSALS2
Federal Register / Vol. 79, No. 76 / Monday, April 21, 2014 / Proposed Rules 22273 

(iii) Ditches that are excavated wholly 

in uplands, drain only uplands, and 

have less than perennial flow. 

(iv) Ditches that do not contribute 

flow, either directly or through another 

water, to a water identified in 

paragraphs (1)(i) through (iv) of this 

definition. 

(v) The following features: 

(A) Artificially irrigated areas that 

would revert to upland should 

application of irrigation water to that 

area cease; 

(B) Artificial lakes or ponds created 

by excavating and/or diking dry land 

and used exclusively for such purposes 

as stock watering, irrigation, settling 

basins, or rice growing; 

(C) Artificial reflecting pools or 

swimming pools created by excavating 

and/or diking dry land; 

(D) Small ornamental waters created 

by excavating and/or diking dry land for 

primarily aesthetic reasons; 

(E) Water-filled depressions created 

incidental to construction activity; 

(F) Groundwater, including 

groundwater drained through 

subsurface drainage systems; and 

(G) Gullies and rills and non-wetland 

swales. 

(3) Definitions— 

(i) Adjacent. The term adjacent means 

bordering, contiguous or neighboring. 

Waters, including wetlands, separated 

from other waters of the United States 

by man-made dikes or barriers, natural 

river berms, beach dunes and the like 

are ‘‘adjacent waters.’’ 

(ii) Neighboring. The term 

neighboring, for purposes of the term 

‘‘adjacent’’ in this section, includes 

waters located within the riparian area 

or floodplain of a water identified in 

paragraphs (1)(i) through (v) of this 

definition, or waters with a shallow 

subsurface hydrologic connection or 

confined surface hydrologic connection 

to such a jurisdictional water. 

(iii) Riparian area. The term riparian 

area means an area bordering a water 

where surface or subsurface hydrology 

directly influence the ecological 

processes and plant and animal 

community structure in that area. 

Riparian areas are transitional areas 

between aquatic and terrestrial 

ecosystems that influence the exchange 

of energy and materials between those 

ecosystems. 

(iv) Floodplain. The term floodplain 

means an area bordering inland or 

coastal waters that was formed by 

sediment deposition from such water 

under present climatic conditions and is 

inundated during periods of moderate to 

high water flows. 

(v) Tributary. The term tributary 

means a water physically characterized 

by the presence of a bed and banks and 

ordinary high water mark, as defined at 

33 CFR 328.3(e), which contributes 

flow, either directly or through another 

water, to a water identified in 

paragraphs (1)(i) through (iv) of this 

definition. In addition, wetlands, lakes, 

and ponds are tributaries (even if they 

lack a bed and banks or ordinary high 

water mark) if they contribute flow, 

either directly or through another water 

to a water identified in paragraphs (1)(i) 

through (iii) of this definition. A water 

that otherwise qualifies as a tributary 

under this definition does not lose its 

status as a tributary if, for any length, 

there are one or more man-made breaks 

(such as bridges, culverts, pipes, or 

dams), or one or more natural breaks 

(such as wetlands at the head of or along 

the run of a stream, debris piles, boulder 

fields, or a stream that flows 

underground) so long as a bed and 

banks and an ordinary high water mark 

can be identified upstream of the break. 

A tributary, including wetlands, can be 

a natural, man-altered, or man-made 

water and includes waters such as 

rivers, streams, lakes, ponds, 

impoundments, canals, and ditches not 

excluded in paragraph (2)(iii) or (iv) of 

this definition. 

(vi) Wetlands. The term wetlands 

means those areas that are inundated or 

saturated by surface or groundwater at 

a frequency and duration sufficient to 

support, and that under normal 

circumstances do support, a prevalence 

of vegetation typically adapted for life 

in saturated soil conditions. Wetlands 

generally include swamps, marshes, 

bogs and similar areas. 

(vii) Significant nexus. The term 

significant nexus means that a water, 

including wetlands, either alone or in 

combination with other similarly 

situated waters in the region (i.e., the 

watershed that drains to the nearest 

water identified in paragraphs (1)(i) 

through (iii) of this definition), 

significantly affects the chemical, 

physical, or biological integrity of a 

water identified in paragraphs (1)(i) 

through (iii) of this definition. For an 

effect to be significant, it must be more 

than speculative or insubstantial. Other 

waters, including wetlands, are 

similarly situated when they perform 

similar functions and are located 

sufficiently close together or sufficiently 

close to a ‘‘water of the United States’’ 

so that they can be evaluated as a single 

landscape unit with regard to their 

effect on the chemical, physical, or 

biological integrity of a water identified 

in paragraphs (1)(i) through (iii) of this 

definition. 

* * * * * 

PART 401—GENERAL PROVISIONS 

■ 22. The authority citation for part 401 

continues to read as follows: 

Authority: The Clean Water Act, 33 U.S.C. 

1251 et seq. 

■ 23. Section 401.11 is amended by 

revising paragraph (l) to read as follows: 

§ 401.11 General definitions. 

* * * * * 

(l) The term navigable waters means 

the waters of the United States, 

including the territorial seas. 

(1) For purposes of all sections of the 

Clean Water Act, 33 U.S.C. 1251 et. seq. 

and its implementing regulations, 

subject to the exclusions in paragraph 

(l)(2) of this section, the term ‘‘waters of 

the United States’’ means: 

(i) All waters which are currently 

used, were used in the past, or may be 

susceptible to use in interstate or foreign 

commerce, including all waters which 

are subject to the ebb and flow of the 

tide; 

(ii) All interstate waters, including 

interstate wetlands; 

(iii) The territorial seas; 

(iv) All impoundments of waters 

identified in paragraphs (l)(1)(i) through 

(iii) and (v) of this section; 

(v) All tributaries of waters identified 

in paragraphs (l)(1)(i) through (iv) of this 

section; 

(vi) All waters, including wetlands, 

adjacent to a water identified in 

paragraphs (l)(1)(i) through (v) of this 

section; and 

(vii) On a case-specific basis, other 

waters, including wetlands, provided 

that those waters alone, or in 

combination with other similarly 

situated waters, including wetlands, 

located in the same region, have a 

significant nexus to a water identified in 

paragraphs (l)(1)(i) through (iii) of this 

section. 

(2) The following are not ‘‘waters of 

the United States’’ notwithstanding 

whether they meet the terms of 

paragraphs (l)(1)(i) through (vii) of this 

section— 

(i) Waste treatment systems, including 

treatment ponds or lagoons, designed to 

meet the requirements of the Clean 

Water Act. 

(ii) Prior converted cropland. 

Notwithstanding the determination of 

an area’s status as prior converted 

cropland by any other Federal agency, 

for the purposes of the Clean Water Act 

the final authority regarding Clean 

Water Act jurisdiction remains with 

EPA. 

(iii) Ditches that are excavated wholly 

in uplands, drain only uplands, and 

have less than perennial flow. 

(iv) Ditches that do not contribute 

flow, either directly or through another 


emcdonald on DSK67QTVN1PROD with PROPOSALS2
22274 Federal Register / Vol. 79, No. 76 / Monday, April 21, 2014 / Proposed Rules 

water, to a water identified in 

paragraphs (l)(1)(i) through (iv) of this 

section. 

(v) The following features: 

(A) Artificially irrigated areas that 

would revert to upland should 

application of irrigation water to that 

area cease; 

(B) Artificial lakes or ponds created 

by excavating and/or diking dry land 

and used exclusively for such purposes 

as stock watering, irrigation, settling 

basins, or rice growing; 

(C) Artificial reflecting pools or 

swimming pools created by excavating 

and/or diking dry land; 

(D) Small ornamental waters created 

by excavating and/or diking dry land for 

primarily aesthetic reasons; 

(E) Water-filled depressions created 

incidental to construction activity; 

(F) Groundwater, including 

groundwater drained through 

subsurface drainage systems; and 

(G) Gullies and rills and non-wetland 

swales. 

(3) Definitions— 

(i) Adjacent. The term adjacent means 

bordering, contiguous or neighboring. 

Waters, including wetlands, separated 

from other waters of the United States 

by man-made dikes or barriers, natural 

river berms, beach dunes and the like 

are ‘‘adjacent waters.’’ 

(ii) Neighboring. The term 

neighboring, for purposes of the term 

‘‘adjacent’’ in this section, includes 

waters located within the riparian area 

or floodplain of a water identified in 

paragraphs (l)(1)(i) through (v) of this 

section, or waters with a shallow 

subsurface hydrologic connection or 

confined surface hydrologic connection 

to such a jurisdictional water. 

(iii) Riparian area. The term riparian 

area means an area bordering a water 

where surface or subsurface hydrology 

directly influence the ecological 

processes and plant and animal 

community structure in that area. 

Riparian areas are transitional areas 

between aquatic and terrestrial 

ecosystems that influence the exchange 

of energy and materials between those 

ecosystems. 

(iv) Floodplain. The term floodplain 

means an area bordering inland or 

coastal waters that was formed by 

sediment deposition from such water 

under present climatic conditions and is 

inundated during periods of moderate to 

high water flows. 

(v) Tributary. The term tributary 

means a water physically characterized 

by the presence of a bed and banks and 

ordinary high water mark, as defined at 

33 CFR 328.3(e), which contributes 

flow, either directly or through another 

water, to a water identified in 

paragraphs (l)(1)(i) through (iv) of this 

section. In addition, wetlands, lakes, 

and ponds are tributaries (even if they 

lack a bed and banks or ordinary high 

water mark) if they contribute flow, 

either directly or through another water 

to a water identified in paragraphs 

(l)(1)(i) through (iii) of this section. A 

water that otherwise qualifies as a 

tributary under this definition does not 

lose its status as a tributary if, for any 

length, there are one or more man-made 

breaks (such as bridges, culverts, pipes, 

or dams), or one or more natural breaks 

(such as wetlands at the head of or along 

the run of a stream, debris piles, boulder 

fields, or a stream that flows 

underground) so long as a bed and 

banks and an ordinary high water mark 

can be identified upstream of the break. 

A tributary, including wetlands, can be 

a natural, man-altered, or man-made 

water and includes waters such as 

rivers, streams, lakes, ponds, 

impoundments, canals, and ditches not 

excluded in paragraph (l)(2)(iii) or (iv) 

of this section. 

(vi) Wetlands. The term wetlands 

means those areas that are inundated or 

saturated by surface or groundwater at 

a frequency and duration sufficient to 

support, and that under normal 

circumstances do support, a prevalence 

of vegetation typically adapted for life 

in saturated soil conditions. Wetlands 

generally include swamps, marshes, 

bogs and similar areas. 

(vii) Significant nexus. The term 

significant nexus means that a water, 

including wetlands, either alone or in 

combination with other similarly 

situated waters in the region (i.e., the 

watershed that drains to the nearest 

water identified in paragraphs (l)(1)(i) 

through (iii) of this section), 

significantly affects the chemical, 

physical, or biological integrity of a 

water identified in paragraphs (l)(1)(i) 

through (iii) of this section. For an effect 

to be significant, it must be more than 

speculative or insubstantial. Other 

waters, including wetlands, are 

similarly situated when they perform 

similar functions and are located 

sufficiently close together or sufficiently 

close to a ‘‘water of the United States’’ 

so that they can be evaluated as a single 

landscape unit with regard to their 

effect on the chemical, physical, or 

biological integrity of a water identified 

in paragraphs (l)(1)(i) through (iii) of 

this section. 

* * * * * 

[FR Doc. 2014–07142 Filed 4–18–14; 8:45 am] 

BILLING CODE 6560–50–P 


emcdonald on DSK67QTVN1PROD with PROPOSALS2