Draft Guidance on Identifying Waters Protected by the Clean Water Act 

This draft guidance clarifies how the Environmental Protection Agency (EPA)*i and the 

U.S. Army Corps of Engineers (the Corps)ii will identify waters protected by the Federal Water 

Pollution Control Act Amendments of 19721

 (Clean Water Act or CWA or Act) and implement 

the Supreme Court’s decisions concerning the extent of waters covered by the Act (Solid Waste 

Agency of Northern Cook County v. U.S. Army Corps of Engineers (SWANCC)2

 and Rapanos v. 

United States (Rapanos)3). This document clarifies how the EPA and the Corps understand 

existing requirements of the CWA and the agencies' implementing regulations in light of 

SWANCC and Rapanos and provides guidance to agency field staff in making determinations 

about whether waters are protected by the CWA. 

This draft guidance document is intended to describe for agency field staff the agencies’ 

current understandings; it is not a rule, and hence it is not binding and lacks the force of law. 

Once finalized, this guidance will supersede existing guidance to field staff issued in 2003 and 

2008 on the scope of “waters of the United States” (also “waters of the U.S.”) subject to CWA 

programs.

iii Although guidance does not have the force of law, it is frequently used by Federal 

agencies to explain and clarify their understandings of existing requirements. In this case, the 

agencies believe that field staff across the country will benefit from new guidance that is 

informed by lessons learned since 2008 and that reflects the agencies’ understandings with 

respect to CWA jurisdiction, consistent with Supreme Court decisions and existing agency 

regulations. Each jurisdictional determination, however, will be made on a case-by-case basis 

considering the facts and circumstances of the case and consistent with applicable statutes, 

regulations, and case law. 

After receiving and taking account of public comments on this document, EPA and the 

Corps expect to finalize it and to undertake rulemaking consistent with the Administrative 

Procedure Act. This process is expected to start with a proposed rule, to clarify further via 

regulation the extent of Clean Water Act jurisdiction, consistent with the Court's decisions. EPA 

and the Corps decided to begin this process with draft, nonbinding guidance in order to clarify 

their existing understandings while also considering and receiving the benefit of public 

comments. 

Congress enacted the Clean Water Act “to restore and maintain the chemical, physical, 

and biological integrity of the Nation’s waters,” and this guidance will help the agencies 

implement specific provisions of the Act to achieve this objective.4

 The CWA has a number of 

programs designed to protect and restore the Nation's waters. Together, these programs provide 

effective protection from pollution for waterbodies across the country, including waters that 

* To increase clarity of this document, endnotes that primarily provide citations will be indicated with Arabic 

numerals, and footnotes that provide additional substantive information will be indicated with Roman numerals. 

i

 EPA Regions will use this guidance to oversee and implement programs under the Clean Water Act, including 

those under sections 303, 311, 401, 402 and 404, 33 U.S.C. §§ 1313, 1321, 1341, 1342 and 1344. (See endnote 1 

for an explanation of the relevant history of the Clean Water Act.)

ii Corps Districts will utilize this guidance to implement Clean Water Act section 404, 33 U.S.C. § 1344. 

iii Specifically, this memorandum supersedes the “Joint Memorandum” providing clarifying guidance on SWANCC,
 

dated January 15, 2003 (68 Fed. Reg. 1991, 1995), and “Clean Water Act Jurisdiction Following the U.S. Supreme 

Court’s Decision in Rapanos v. United States & Carabell v. United States,” dated December 2, 2008. 
supply drinking water, filter pollutants, provide water for irrigation, and support hunting and 

fishing, outdoor recreation, and tourism. 

The Clean Water Act, however, applies only to waters that are “waters of the United 

States.” This draft guidance clarifies how EPA and the Corps will identify waters to be protected 

under the Act consistent with the statute, regulations, Supreme Court caselaw, relevant science 

related to aquatic ecosystems, and the agencies' field experience. As noted above, this guidance, 

once finalized, will supersede previously issued guidance on the scope of “waters of the United 

States” (also “waters of the U.S.”) subject to CWA programs. However, it is not the agencies’ 

intention that previously issued jurisdictional determinations be re-opened as a result of this 

guidance. 

The U.S. Supreme Court has addressed the scope of waters of the United States protected 

by the CWA in three cases. In United States v. Riverside Bayview Homes, Inc. (474 U.S. 121 

(1985)), the Supreme Court held that wetlands adjacent to a traditional navigable water were 

properly considered to be “waters of the United States.” In SWANCC, the Court addressed the 

question of CWA jurisdiction over isolated, non-navigable, intrastate ponds, and concluded that 

CWA jurisdiction could not be based solely on the presence of migratory birds. In Rapanos, the 

Court addressed CWA protections for wetlands adjacent to non-navigable tributaries, and issued 

five opinions with no single opinion commanding a majority of the Court. The plurality opinion, 

authored by Justice Scalia, stated that “waters of the United States” extended beyond traditional 

navigable waters to include “relatively permanent, standing or flowing bodies of water.” Id. at 

739. The plurality went on to clarify that relatively permanent waters ”do not necessarily 

exclude” streams, rivers, or lakes that might dry up in extraordinary circumstances, such as 

drought, and seasonal rivers, which contain continuous flow during some months of the year but 

no flow during dry months. The plurality opinion also asserted that only wetlands with a 

“continuous surface connection” to other jurisdictional waters are considered “adjacent” and 

protected by the CWA. Id. at 742. 

Justice Kennedy’s concurring opinion took a different approach from Justice Scalia’s. 

Justice Kennedy concluded that “waters of the United States” included wetlands that had a 

significant nexus to traditional navigable waters, “if the wetlands, 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). 

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 (id. at 810). 

The agencies continue to believe, as expressed in previous guidance, that it is most 

consistent with the Rapanos decision to assert jurisdiction over waters that satisfy either the 

plurality or the Justice Kennedy standard, since a majority of justices would support jurisdiction 

under either standard. However, after careful review of these opinions, the agencies concluded 

that previous guidance did not make full use of the authority provided by the CWA to include 

waters within the scope of the Act, as interpreted by the Court. This draft guidance provides a 

more complete discussion of the agencies’ interpretation, including of how waters with a 

"significant nexus" to traditional navigable waters or interstate waters are protected by the CWA. 

2
 
 

In addition, this guidance explains the legal basis for coverage of waters by the CWA in cases 

that were not addressed by the previous guidance (for example, interstate waters). 

The agencies expect, based on relevant science and recent field experience, that under the 

understandings stated in this draft guidance, the extent of waters over which the agencies assert 

jurisdiction under the CWA will increase compared to the extent of waters over which 

jurisdiction has been asserted under existing guidance, though certainly not to the full extent that 

it was typically asserted prior to the Supreme Court decisions in SWANCC and Rapanos. 

However, each jurisdictional determination will be made on a case-by-case basis considering the 

facts and circumstances of the case and consistent with applicable statutes, regulations, and case 

law. 

The agencies understand that decisions concerning whether or not a waterbody is subject 

to the CWA have consequences for State, tribal, and local governments and for private parties. 

Consistent with Executive Order 13563, and in particular its emphasis on predictability and 

certainty, key goals of this draft guidance are to increase clarity and to reduce costs and delays in 

obtaining CWA permits by reducing the complexity of Corps of Engineers and EPA decisions 

concerning waters protected by the CWA, thus improving the predictability of the process of 

identifying waters protected by the Act, and increasing consistency of decisions across the 

country. 

There is only one CWA definition of “waters of the United States.” Thus, this draft 

guidance, like the earlier guidance it replaces, necessarily will apply to decisions concerning 

whether a waterbody is subject to any of the programs authorized under the CWA. Although 

SWANCC and Rapanos specifically involved section 404 of the CWA and discharges of dredged 

or fill material, the term “waters of the United States” must be interpreted consistently for all 

CWA provisions that use the term. These provisions include the section 402 National Pollutant 

Discharge Elimination System (NPDES) permit program, the section 311 oil spill program,5

 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.6 

This draft guidance does not address the regulatory exclusions from coverage under the 

CWA for waste treatment systems and prior converted croplands, or practices for identifying 

waste treatment systems or prior converted croplands.7 It does not affect any of the exemptions 

from CWA section 404 permitting requirements provided by CWA section 404(f), including 

those for normal agriculture, forestry and ranching practices.8 This guidance also does not 

address the statutory and regulatory exemptions from NPDES permitting requirements for 

agricultural stormwater discharges and return flows from irrigated agriculture.9 

The CWA provisions and supporting regulations described in this document contain 

legally binding requirements. The agencies emphasize that this guidance does not substitute for 

those provisions or regulations and is not itself a regulation. It does not impose legally binding 

requirements on EPA, the Corps, or the regulated community, and may not apply to a particular 

situation depending on the circumstances. Any decisions regarding a particular water will be 

3
 
 

based on the applicable statutes, regulations, and case law. Therefore, interested persons are free 

to raise questions regarding particular situations, and EPA and/or the Corps will consider 

whether or not the recommendations or interpretations of this guidance are appropriate in that 

situation based on the statutes, regulations, and case law. The use of language such as 

"recommend," "may," "should" and "can" is intended to describe agency policies and 

recommendations, while the use of mandatory terminology such as "must" and "required" is 

intended to describe the agencies’ interpretations of controlling requirements under the terms of 

the CWA, its implementing regulations, and relevant case law. 

This draft guidance is divided into eight sections: 

•	 The first two sections address the fundamental classes of waters subject to Clean Water 

Act jurisdiction: traditional navigable waters (Section 1) and interstate waters (Section 

2). 

•	 The next section provides general guidance relating to the “significant nexus” standard 

described by Justice Kennedy in the Rapanos decision (Section 3). 

•	 The next three sections provide guidance on determining whether various types of waters 

are subject to CWA jurisdiction, including: 

o	 Tributaries (Section 4); 

o	 Adjacent wetlands (Section 5); and 

o	 Other waters (Section 6). 

•	 The next section provides examples of waters that are generally not waters of the United 

States under the CWA (Section 7). 

•	 The final section provides guidance on the documentation necessary to support decisions 

concerning whether waters are protected by the CWA (Section 8). 

Additional scientific and legal information concerning these topics is provided in an 

appendix at the end of this document. 

4
 
 

 

 

Summary of Key Points 

Based on the agencies’ interpretation of the statute, implementing regulations and relevant 

caselaw, the following waters are protected by the Clean Water Act: 

•	 Traditional navigable waters; 

•	 Interstate waters; 

•	 Wetlands adjacent to either traditional navigable waters or interstate waters; 

•	 Non-navigable tributaries to traditional navigable waters that are relatively permanent, 

meaning they contain water at least seasonally; and 

•	 Wetlands that directly abut relatively permanent waters. 

In addition, the following waters are protected by the Clean Water Act if a fact-specific analysis 

determines they have a “significant nexus” to a traditional navigable water or interstate water: 

•	 Tributaries to traditional navigable waters or interstate waters; 

•	 Wetlands adjacent to jurisdictional tributaries to traditional navigable waters or 

interstate waters; and 

•	 Waters that fall under the “other waters” category of the regulations. The guidance 

divides these waters into two categories, those that are physically proximate to other 

jurisdictional waters and those that are not, and discusses how each category should be 

evaluated. 

The following aquatic areas are generally not protected by the Clean Water Act: 

•	 Wet areas that are not tributaries or open waters and do not meet the agencies’ 

regulatory definition of “wetlands”;
 

•	 Waters excluded from coverage under the CWA by existing regulations; 

•	 Waters that lack a “significant nexus” where one is required for a water to be protected 

by the CWA; 

•	 Artificially irrigated areas that would revert to upland should irrigation cease; 

•	 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; 

•	 Artificial reflecting pools or swimming pools created by excavating and/or diking dry 

land; 

•	 Small ornamental waters created by excavating and/or diking dry land for primarily 

aesthetic reasons; 

•	 Water-filled depressions created incidental to construction activity; 

•	 Groundwater drained through subsurface drainage systems and 

•	 Erosional features (gullies and rills), and swales and ditches that are not tributaries or 

wetlands. 

5
 
Section 1: Traditional Navigable Waters 

EPA and the Corps will continue to assert CWA jurisdiction over “[a]ll 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.”10 These 

waters are referred to in this guidance as “traditional navigable waters.” The traditional 

navigable waters include all of the “navigable waters of the United States,” as defined in 33 

C.F.R. part 329 and by numerous decisions of the federal courts, plus all other waters that are 

navigable-in-fact (for example, the Great Salt Lake, Utah, and Lake Minnetonka, Minnesota). 

Thus, the traditional navigable waters include, but are not limited to, the “navigable waters of the 

United States” within the meaning of section 10 of the Rivers and Harbors Act of 1899 (also 

known as “Section 10 waters”).11 

For purposes of CWA jurisdiction and this guidance, waters will be considered traditional 

navigable waters if: 

•	 They are subject to section 9 or 10 of the Rivers and Harbors Act; or 

•	 A federal court has determined that the water body is navigable-in-fact under federal law; 

or 

•	 They are waters currently being used for commercial navigation, including commercial 

waterborne recreation (for example, boat rentals, guided fishing trips, or water ski 

tournaments); or 

•	 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 capacity of the 

water to be used in commercial navigation, including commercial recreational navigation 

(for example, size, depth, and flow velocityiv), and the likelihood of future commercial 

navigation, including commercial waterborne recreation. 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, should be supported by evidence. v 

 

 

iv 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 waterbody has the physical
 

characteristics suitable for navigation.
 v

 A trip taken solely for the purpose of demonstrating a waterbody can be navigated would be sufficient. See, e.g., 

FPL Energy Marine Hydro L.L.C. v. FERC, 287 F.3d 1151, 1157 (D.C. Cir. 2002). 

6
 
 

 

 

Section 2: Interstate Waters 

EPA and the Corps will assert jurisdiction over all interstate waters, consistent with the 

agencies’ current regulations defining “waters of the United States” to include “interstate waters 

including interstate wetlands.”12 Interstate waters, defined by the federal water pollution control 

statutes prior to the CWA as “all rivers, lakes, and other waters that flow across, or form a part 

of, State boundaries,” remain jurisdictional waters under the CWA, even if such waters are not 

traditional navigable waters as described in Section 1 above.13 For purposes of this guidance, 

lakes, ponds, and similar lentic (or still) water features crossing state boundaries are 

jurisdictional as interstate waters in their entirety. For streams and rivers, including 

impoundments, field staff should determine the upstream and downstream extent of the stream 

or river crossing a state boundary that should be considered the “interstate water.” One method 

of determining the extent of a riverine “interstate water” is the use of stream order. Thus, for 

rivers and streams the “interstate water” would extend upstream and downstream of such 

boundary for the entire length that the water is of the same stream order.14 

The agencies will analyze tributaries to interstate waters15 consistent with the treatment of 

tributaries to traditional navigable waters under Justice Kennedy's standard discussed in Section 

4 below. Similarly, the agencies will analyze wetlands adjacent to interstate waters (except 

wetlands that are adjacent to interstate wetlands)16 consistent with the treatment of adjacent 

wetlands under Justice Kennedy's standard discussed in Section 5 below. Finally, EPA and the 

Corps will analyze other waters relative to an interstate water consistent with Section 6 below. 

Section 3: Significant Nexus Analysis 

The agencies will assert jurisdiction over waters with a significant nexus to traditional 

navigable waters or interstate waters in accordance with SWANCC and Rapanos. Justice 

Kennedy stated: 

“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.”17 

Waters have the requisite significant nexus if they, either alone or in combination with 

similarly situated waters in the region, significantly affect the chemical, physical, or biological 

integrity of traditional navigable waters or interstate waters.vi There is one significant nexus 

standard for waters of the United States, and this section provides general guidance for 

determining the presence or absence of a significant nexus. Sections 4, 5 and 6 provide more 

vi 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. Consistent with Justice Kennedy’s 

instruction, EPA and the Corps will apply the significant nexus standard in a manner that restores and maintains any 

of these three attributes of traditional navigable waters and interstate waters. 

7
 
specific guidance to field staff for applying the significant nexus standard when determining 

jurisdiction over: 

•	 tributaries, 

• adjacent wetlands, and 

• other waters. 

To evaluate the presence or absence of a significant nexus, the agencies intend to, as a 

general matter, consider: 

(1) Waters to be “similarly situated” with waters of the same resource type, specifically 

(a) tributaries; (b) adjacent wetlands; or (c) other waters that are in close physical 

proximity to traditional navigable waters, interstate waters, or their jurisdictional 

tributaries (“proximate other waters”);vii 

(2) Waters to be “in the region” if they fall within the same watershed. For the purposes 

of this analysis, the watershed is defined by the area draining into the traditional 

navigable water or interstate water; and 

(3) Waters to have a significant nexus if they alone or in combination with other similarly 

situated waters in the same watershed have an effect on the chemical, physical, or 

biological integrity of traditional navigable waters or interstate waters that is more 

than “speculative or insubstantial.” 

Therefore, field staff should first determine whether the water to be evaluated is a 

tributary, adjacent wetland, or proximate other water under the regulations - waters in the same 

category should be considered the similarly situated waters. 

Next, field staff should determine the watershed, as defined by the area18 draining into the 

nearest traditional navigable water or interstate water, and should identify the “similarly 

situated” waters in that watershed. The logical and scientifically valid "region" for determining 

whether similarly situated waters have a significant nexus is the watershed that drains to the 

nearest traditional navigable water or interstate water through a single point of entry. There may 

be circumstances in which field staff, for efficiency purposes, elect to begin the case-by-case 

significant nexus analysis utilizing a smaller watershed (for example, in some circumstances, the 

Hydrologic Unit Code (HUC)-10 "watershed" as identified by the U.S. Geological Survey and 

the Natural Resources Conservation Service, which are typically between 40,000-250,000 acres 

in size).19 Field staff should not, however, utilize an area larger than the watershed that drains to 

the nearest traditional navigable water or interstate water through a single point of entry. When a 

smaller watershed provides sufficient science-based justification to establish jurisdiction, field 

staff need not unnecessarily expend administrative time and resources analyzing the entire single 

point of entry watershed. However, field staff should not use a watershed smaller than the single 

point of entry watershed as the basis for a finding of no jurisdiction. 

 

vii For other waters that are not in close physical proximity to traditional navigable waters, interstate waters, or their 

jurisdictional tributaries, the agencies will apply the significant nexus standard to each of these waters individually, 

except in cases where there is a compelling scientific basis for treating a group of such waters as similarly situated 

waters in the same region (see Section 6). 

8
 
Finally, field staff should determine whether the water they are evaluating, in 

combination with other similarly situated waters in the watershed, has a significant nexus to the 

nearest traditional navigable water or interstate water. 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, and provision of aquatic 

habitat. A hydrologic connection is not necessary to establish a significant nexus, because 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 or interstate water, such as retention of flood 

waters or pollutants that would otherwise flow downstream to the traditional navigable water or 

interstate water. 

Within a single point of entry watershed, over a period of time there will probably be 

multiple jurisdictional determinations. While field staff will have to make case-specific 

determinations, they may use information used in previous determinations, and the agencies 

would generally expect that if a significant nexus has been established for one water in the 

watershed, then other similarly situated waters in the watershed would also be found to have a 

significant nexus, because under Justice Kennedy’s test, similarly situated waters in the region 

should be evaluated together. However, the documentation for each case should be complete 

enough to support the specific jurisdictional determination without cross-references to other files, 

including an explanation of which waters were considered together as similarly situated and in 

the same region. 

Among the most important tasks for field staff is demonstrating that a significant nexus 

exists between the “similarly situated” waters that are the subject of a case-specific jurisdictional 

determination and the relevant traditional navigable water or interstate water. Justice Kennedy 

provides guidance about the nature of the nexus when he concludes that waters are not 

jurisdictional when their effects on the physical, chemical, or biological integrity of downstream 

traditional navigable waters are speculative or insubstantial. In the context used by Justice 

Kennedy, a “significant nexus” includes having a predictable or observable chemical, physical, 

or biological functional relationship between the similarly situated waters and the traditional 

navigable water or interstate water. EPA and the Corps should further demonstrate that the 

similarly situated waters significantly affect the traditional navigable water or interstate water. 

Thus, field staff should look for indicators of hydrology, effects on water quality, and 

physical, chemical, and biological (including ecological) connections or functions when 

assessing whether a water, alone or in combination with similarly situated waters, has a more 

than speculative or insubstantial effect on the chemical, physical, or biological integrity of 

downstream traditional navigable waters or interstate waters. Examples of ways in which 

hydrology can significantly affect downstream waters include, but are not limited to, transport of 

water and materials and compounds carried by the water (e.g., suspended materials, dissolved 

compounds), water retention, as a medium for the movement of aquatic organisms such as fish 

and invertebrates, and water discharge (e.g., release of retained water to other waters). Effects 

on the chemical integrity of downstream waters may include the extent to which the waters have 

the capacity to carry pollutants (for example, petroleum wastes, toxic wastes, and sediment) or 

flood waters downstream to traditional navigable waters or interstate waters; the extent to which 

9
 
the waters reduce the amount of pollutants or flood waters that would otherwise enter traditional 

navigable waters or interstate waters; and the extent to which the waters perform physical 

functions related to the maintenance of downstream water quality such as sediment trapping. 

 Biological functions performed by the waters that may affect downstream traditional navigable 

waters or interstate waters include the capacity to transfer nutrients and organic carbon to 

downstream food webs (for example, macroinvertebrates present in headwater streams convert 

carbon in leaf litter, making it available to species downstream), and the maintenance of habitat 

that provides spawning areas for species in downstream waters. 

Analysis of the above indicators, whether documented for an individual water or based on 

scientific literature describing functions applicable to the waters in question, along with an 

analysis of how the described functions affect a traditional navigable water or interstate water 

will allow field staff to evaluate whether the water alone or in combination with similarly 

situated waters in the watershed is likely to have a more than speculative or insubstantial effect 

on the chemical, physical, or biological integrity of a traditional navigable water or interstate 

water. It is not appropriate to determine significant nexus based solely on any specific threshold 

of distance (for example, between a tributary and the traditional navigable water). Watershed 

ecosystems, and their interrelationships, are constructed of component parts that have relevance 

when considered collectively. Failure to protect the components can undermine the ecosystem in 

its entirety. Therefore, the agencies have an obligation to evaluate waters in terms of how they 

interrelate and function as ecosystems rather than as individual units, especially in the context of 

complex ecosystems where their integrity may be compromised by environmental harms that 

individually may not be measurably large but collectively are significant. 

It is important to clarify that agency field staff, in conducting a significant nexus analysis, 

are not required to identify or evaluate every similarly situated water located within a particular 

watershed being assessed. Staff should evaluate as many waters of the same type as is necessary 

to support and document the presence or absence of a significant nexus for that type of water 

(e.g., adjacent wetland, tributary or proximate other water). Staff should be confident that their 

significant nexus determination based on evaluation of a representative subset of adjacent 

wetlands, tributaries, or proximate other waters in a particular watershed would be fully 

consistent with a determination based on an evaluation of all waters of the same type in the 

watershed. Field staff should look at the best available information to identify the similarly 

situated waters in the point of entry watershed and their effects on downstream traditional 

navigable waters or interstate waters. In many circumstances, a reliable affirmative jurisdictional 

determination may be based on consideration of a subset of similarly situated waters, since 

including additional waters in the analysis would only establish a more significant nexus to the 

traditional navigable water or interstate water. In general, field staff are not expected to develop 

new information on similarly situated waters (e.g., the identification or delineation of as yet 

unmapped wetlands or tributaries). In many cases, scientifically credible (e.g., peer reviewed) 

literature on the functions and effects of similarly situated waters generally will be sufficient, 

along with site-specific information for the water for which a determination is being conducted, 

to support a significant nexus jurisdictional determination. This information should be 

incorporated into a site-specific explanation of how the waterbody and similarly situated waters 

in the region significantly affect the physical, chemical, or biological integrity of a traditional 

navigable or interstate water. 

10
 
 

Section 4: Tributaries 

EPA and the Corps will assert jurisdiction over tributaries under either the plurality 

standard or the Kennedy standard, as described below. 

For purposes of this guidance, a water may be a tributary if it contributes flow to a 

traditional navigable water or interstate water, either directly or indirectly by means of other 

tributaries. A tributary can be a natural, man-altered, or man-made water body. Examples 

include rivers and streams, as well as lakes and certain wetlands that are part of the tributary 

system and flow directly or indirectly into traditional navigable waters or interstate waters. A 

tributary is physically characterized by the presence of a channel with defined bed and bank. The 

bed of a stream is the bottom of the channel. The lateral constraints (channel margins) are the 

stream banks. Channels are formed, maintained, and altered by the water and sediment they 

carry, and the forms they take can vary greatly. 

A means of identifying the lateral limits of a tributary, including where there are no 

contiguous wetlands, is the existence of an ordinary high water mark (OHWM). Corps 

regulations define OHWM as “that line on the shore established by the fluctuations of water and 

indicated by physical characteristics such as a clear, natural line impressed on the bank, 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.”20 

In many tributaries, the bed is that part of the channel below the OWHM, and the banks often 

extend above the OHWM. Channel characteristics depend on variables such as hydrology, 

lithology, climate, physiography, and gradient,21 among others. A tributary continues as far as a 

channel (i.e., bed and bank) is present. A natural or manmade break (e.g., rock outcrop, 

underground flow, dam, weir, diversion, or similar break) in the presence of a bed and bank or 

ordinary high water mark does not establish the upstream limit of a tributary in cases where a 

bed and bank and an ordinary high water mark can be identified upstream and downstream of the 

break. Tributaries that have been channelized by being lined with concrete are still considered 

tributaries for the purposes of this guidance. 

Certain types of erosional features, such as gullies and rills, are not tributaries for 

purposes of this guidance. Gullies22 are relatively deep channels that are ordinarily formed on 

valley sides and floors where no well-defined channel previously existed. They are commonly 

found in areas with low-density vegetative cover or with soils that are highly erodible. Rills23 

are formed by overland water flows eroding the soil surface during rain storms. Erosional 

features that are not tributaries for the purposes of this guidance can also be found in 

environments where compacted soil and sparse vegetation have increased overland flow 

significantly. The two main processes that result in the formation of gullies and similar erosional 

features 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 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 more defined 

11
 
bed and banks as compared to typical erosional features that are more deeply incised. Field staff 

should consider these factors as they distinguish streams and other tributaries that may be subject 

to Clean Water Act jurisdiction from other types of erosional features. 

Non-tidal ditches (including roadside and agricultural ditches) are also not tributaries except 

where they have a bed, bank, and ordinary high water mark; connect directly or indirectly to a 

traditional navigable or interstate water; and have one of the following five characteristics: 

•	 natural streams that have been altered (e.g., channelized, straightened or relocated); 

•	 ditches that have been excavated in waters of the U.S., including wetlands; 

•	 ditches that have relatively permanent flowing or standing water; 

•	 ditches that connect two or more jurisdictional waters of the U.S.; or 

•	 ditches that drain natural water bodies (including wetlands) into the tributary system of a 

traditional navigable or interstate water. 

If a ditch is considered a tributary, it will be evaluated in the same manner as other 

tributaries (i.e., plurality standard or Kennedy standard, as appropriate). Note that tidal ditches 

are by definition waters of the U.S. 

Natural and man-made swales are also not tributaries for purposes of this guidance. In 

certain circumstances, however, ditches or swales include areas that meet the regulatory 

definition of “wetlands.” Wetland ditches and swales will be evaluated as wetlands under the 

plurality or Kennedy standard, not as tributaries (unless the ditch itself is considered a tributary 

for one of the reasons stated above). Ditches and swales are considered wetlands when they 

meet the applicable criteria in the Corps of Engineers Wetland Delineation Manual or the 

appropriate regional supplement to that Wetland Delineation Manual. 

Even when not jurisdictional waters, these geographic features (e.g., swales, ditches) may 

still contribute to a surface hydrologic connection between an adjacent wetland and a traditional 

navigable water or interstate water. In addition, these geographic features may function as “point 

sources” (i.e., "discernible, confined and discrete conveyance[s]" under CWA section 502(14)), 

such that discharges of pollutants to waters through these features could be subject to other CWA 

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

Tributaries Covered under the Rapanos Plurality Standard 

EPA and the Corps will assert jurisdiction over “relatively permanent, standing or 

continuously flowing bodies of water” connected to traditional navigable waters.viii Under the 

plurality standard, relatively permanent waters are jurisdictional without making a significant 

nexus finding. 

 

viii 547 U.S. at 739. The agencies will not assert jurisdiction over such waters under the plurality standard within the 

Eleventh Circuit, i.e., waters in the states of Florida, Georgia and Alabama. See United States v. Robison, 505 F.3d 

1208 (11th Cir.); reh’g en banc denied, 521 F.3d 1319 (11th Cir. 2007), cert. denied, 129 S. Ct. 627, 630 (2008). 

Instead the agencies will use the Kennedy standard only. 

12
 
Under the plurality standard, a non-navigable tributary is jurisdictional when it satisfies 

the following characteristics: 

(1)	 The tributary is connected, directly or indirectly through other tributaries, to a 

downstream traditional navigable water, and 

(2)	 Flow in the tributary, except for drought years, is at least seasonal. 

A central issue to the plurality standard is what constitutes “seasonal flow.” In this 

context, a water is “seasonal” when it has predictable flow during wet seasons in most years. 

The time period constituting “seasonal” will vary across the country. Rather than having 

distinct, rigid boundaries, stream reaches classified as perennial, intermittent, and ephemeral may 

more accurately be described as dynamic zones within stream networks. The length or extent of 

these zones may be highly variable and is dictated by multiple factors such as annual 

precipitation, evapotranspiration, and land- and water-use practices.24 Thus, determination of 

whether a water meets the plurality standard for relatively permanent should involve 

determination of the length and timing of seasonal flows in the ecoregion in question. 

Tributaries that are not relatively permanent will be evaluated under the Kennedy 

standard. 

Tributaries Covered under the Rapanos Kennedy Standard 

EPA and Corps regulations define “waters of the United States” to include tributaries to 

traditional navigable waters and to interstate waters.25 Consistent with the agencies’ 

interpretation of the CWA, these regulations and the relevant case law, EPA and the Corps 

expect to assert jurisdiction over all tributaries to traditional navigable waters or interstate 

waters, provided that the tributary, alone or in combination with other similarly situated 

tributaries in the watershed, significantly affects the chemical, physical, or biological integrity of 

traditional navigable waters or interstate waters. 

 

Thus, a tributary is jurisdictional where: 

(1)	 It is a tributary as defined for purposes of this guidance to a traditional navigable 

water or an interstate water; and 

(2)	 The tributary, alone or in combination with other tributaries in the watershed, has 

a significant nexus with the traditional navigable water or interstate water. 

When performing a significant nexus analysis for a tributary, the first step is to determine 

whether that tributary has a bed and bank and an ordinary high water mark. If the tributary 

possesses those characteristics, the next step is to determine whether the tributary drains, or is 

part of a network of tributaries that drain, into a downstream traditional navigable water or 

interstate water. If it can be demonstrated that the tributary has a bed and bank, and an OHWM, 

and is part of a tributary system to a traditional navigable water or an interstate water, and, 

therefore, can transport pollutants, flood waters or other materials to a traditional navigable water 

or interstate water, then the agencies would generally expect that the tributary, along with the 

13
 
other tributaries in the watershed (the "similarly situated" waters), can be demonstrated to have a 

significant nexus with the downstream traditional navigable water or interstate water. This 

expectation is based on the significant harm that pollutants can have on the physical, chemical, 

or biological integrity of the downstream traditional navigable water or interstate water.26 The 

presence of a bed and bank and an OHWM are physical indicators of flow and it is likely that 

flows through all of the tributaries collectively in a watershed with the above characteristics are 

sufficient to transport pollutants, or other materials downstream to the traditional navigable water 

or interstate water in amounts that would significantly affect its chemical, physical or biological 

integrity. 

When considering whether the tributary being evaluated eventually flows to an interstate 

water or traditional navigable water, field staff should trace the tributary connection using 

resources such as direct observation or U.S. Geological Survey maps, aerial photography or other 

reliable remote sensing information, soil survey data or other appropriate information. 

Although the agencies generally expect that tributaries will be found to have a significant 

nexus with downstream traditional navigable waters or interstate waters, as explained above, it is 

still important that field staff document such a significant nexus through a site-specific analysis 

for tributaries that are not relatively permanent. Field staff should document, using available or 

readily obtainable information wherever possible, the flow characteristics and functions of the 

tributary or tributaries, and their hydrologic relationship to the nearest downstream traditional 

navigable water or interstate water. Hydrologic information may include volume, duration, and 

frequency of flow (if such information is readily available, e.g., through publicly available 

reports or on-line resources), as well as physical indicators of flow. Field staff may document 

the flow characteristics of tributaries by using physical indicators of flow, observations of flow 

considered in the context of local precipitation patterns and recent precipitation events, field 

reports, local expert statements, and other sources of information. Ordinary high water mark 

determinations are made by examining recent physical evidence of flow.27 It is not necessary to 

document actual flow data via stream gages.28 Field staff should also document other functions 

provided by the tributary, and describe how those functions may significantly affect the physical, 

chemical, or biological integrity of downstream traditional navigable waters or interstate waters. 

Flow characteristics and functions of the tributary or tributaries and their hydrologic 

relationship to the nearest downstream traditional navigable water or interstate water may 

include topographic maps, gage data, historic records of water flow, statistical data, personal 

observations/records, and other relevant information. Consideration may also be given to 

relevant contextual factors that directly influence the hydrology of tributaries, including the size 

of the watershed, average annual rainfall, and average annual winter snow pack. The significant 

nexus evaluation should also discuss the potential for the tributaries to transport pollutants to a 

traditional navigable water or interstate water. Direct observation of the tributary is not 

necessary if other available documentation is sufficient to establish the significant nexus. 

Examples of other functions provided by tributaries that may significantly affect the 

physical, chemical, or biological integrity of downstream traditional navigable waters or 

interstate waters include: distributing sediment29 to maintain stream and riparian habitat; nutrient 

cycling and removal; providing habitat for amphibians, fish, and other aquatic or semi-aquatic 

14
 
species living in and near the stream that may use the downstream waters for other portions of 

their life stages (e.g., spawning areas for recreationally or commercially important species); 

improving or maintaining biological integrity in downstream waters; and transferring nutrients 

and organic carbon vital to support downstream food webs (e.g., macroinvertebrates present in 

headwater streams convert carbon in leaf litter making it available to species downstream).30 

Disruptions in these biological processes can significantly affect the functional capacity of the 

entire downstream system.31 Tributaries help to maintain base flow in the larger rivers 

downstream, which is particularly important in times of drought. At the same time, a network of 

tributaries can regulate the flow of water into downstream waters, moderate low flow and high 

flow extremes, reduce local and downstream flooding, and prevent excess erosion caused by 

flooding.32 

Section 5: Adjacent Wetlands 

The agencies will assert Clean Water Act jurisdiction over adjacent wetlands that meet either the 

plurality standard or the Kennedy standard under Rapanos. 

Wetlands Covered Under the Rapanos Plurality Standard 

EPA and the Corps will assert jurisdiction over “wetlands with a continuous surface 

connection to” “relatively permanent, standing or continuously flowing bodies of water” 

connected to traditional navigable waters.ix 

 

 The plurality opinion in Rapanos created a standard for finding statutory jurisdiction 

under the CWA for wetlands, which is related to the presence of a physical connection between 

the wetland and the relatively permanent water to which it is adjacent. Under the plurality 

standard, wetlands with a continuous surface connection to relatively permanent waters are 

jurisdictional without the legal obligation to make a significant nexus finding. 

Under the plurality standard, an adjacent wetland is jurisdictional when it satisfies the 

following characteristics: 

(1)	 The wetland is adjacent to a relatively permanent, non-navigable tributary, that is 

connected to a downstream traditional navigable water, and 

(2)	 A continuous surface connection exists between the wetland and a relatively 

permanent tributary where the wetland directly abuts the water (e.g., they are not 

separated by uplands, a berm, dike, or similar feature). A “continuous surface 

connection” does not require the presence of water at all times in the connection 

between the wetland and the jurisdictional water. 

Wetlands Covered Under the Rapanos Kennedy Standard 

 

ix 547 U.S. at 739, 742. As noted, the agencies will not assert jurisdiction over such waters under the plurality 

standard within the Eleventh Circuit, i.e., waters in the states of Florida, Georgia and Alabama. See United States v. 

Robison, supra, footnote h. 

15
 
The agencies will assert Clean Water Act jurisdiction over wetlandsx

 adjacent to 

traditional navigable waters or non-wetland interstate waters or to another water of the U.S. 

where such wetlands have a significant nexus with downstream traditional navigable or interstate 

waters.xi Adjacent wetlands will be considered to have a significant nexus if they, alone or in 

combination with similarly situated wetlands, have an effect on the chemical, physical, or 

biological integrity of traditional navigable waters or interstate waters that is more than 

“speculative or insubstantial.”33 As a general matter, “similarly situated” adjacent wetlands 

include all adjacent wetlands located in the point-of-entry watershed. Wetlands adjacent to 

traditional navigable waters or non-wetland interstate waters are per se jurisdictional and do not 

require a showing of significant nexus.34 

Thus, an adjacent wetland is jurisdictional where such wetland meets the definition of 

“adjacent” as that term is defined in the agencies’ regulations and is either: 

(1) Adjacent to a traditional navigable water or non-wetland interstate water; or 

(2) Adjacent to a tributary, lake, reservoir, or other jurisdictional water (except another 

wetland) and either alone or in combination with other adjacent wetlands in the 

watershed has a significant nexus to the nearest downstream traditional navigable or 

interstate water. 

The regulations define “adjacent” as follows: “The term adjacent means bordering, 

contiguous, or neighboring. Wetlands separated from other waters of the United States by manmade dikes or barriers, natural river berms, beach dunes and the like are ‘adjacent wetlands.’”35 

Under this definition, a wetland does not need to meet all criteria to be considered adjacent. The 

agencies consider wetlands to be bordering, contiguous, or neighboring, and therefore “adjacent” 

if at least one of following three criteria is satisfied: 

(1) There is an unbroken surface or shallow sub-surface hydrologic connection between 

the wetland and jurisdictional waters; or 

(2) The wetlands are physically separated from jurisdictional waters by “man-made dikes 

or barriers, natural river berms, beach dunes, and the like”; or 

(3) Where a wetland’s physical proximity to a jurisdictional water is reasonably close, 

that wetland is “neighboring” and thus adjacent. For example, wetlands located 

within the riparian area or floodplain of a jurisdictional water will generally be 

considered neighboring, and thus adjacent. One test for whether a wetland is 

sufficiently proximate to be considered “neighboring” is whether there is a 

demonstrable ecological interconnection between the wetland and the jurisdictional 

waterbody. For example, if resident aquatic species (e.g., amphibians, aquatic turtles, 

fish, or ducks) rely on both the wetland and the jurisdictional waterbody for all or 

part of their life cycles (e.g., nesting, rearing, or feeding), that may demonstrate that 

 

x

 Under normal circumstances, a wetland will meet all three factors of hydrology, hydrophytic vegetation, and 

hydric soils, as required by agency regulations, and described in the United States, U.S. Army Corps of Engineers, 

Wetlands Delineation Manual (Washington, D.C.: U.S. Army Corps of Engineers,1987) or appropriate Regional 

Supplement. The regulatory definition of waters of the U.S. includes “wetlands adjacent to waters (other than 

waters that are themselves wetlands) identified [as jurisdictional].” 33 C.F.R. § 328.3(a)(7); 40 C.F.R. § 230.3(s)(7). xi The plurality standard in Rapanos may provide an alternative basis for asserting jurisdiction. See Section 5. 

16
 
the wetland is neighboring and thus adjacent. The agencies recognize that as the 

distance between the wetland and jurisdictional water increases, the potential 

ecological interconnection between the waters is likely to decrease. 

An unbroken surface or shallow sub-surface hydrologic connection to jurisdictional 

waters may be established by a physical feature or discrete conveyance that supports periodic 

flow between the wetland and a jurisdictional water. Water does not have to be continuously 

present in this hydrologic connection and the flow between the wetland and the jurisdictional 

water may move in either or both directions. The hydrologic connection need not itself be a 

water of the U.S. A shallow subsurface hydrologic connection is lateral water flow through a 

shallow subsurface layer, such as may be found in steeply sloping forested areas with shallow 

soils, soils with a restrictive horizon, or in karst systems.36 Shallow subsurface connections may 

be found 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, position in the landscape (for example, on a slope 

directing flow from wetland to jurisdictional waters), stream hydrograph, and soil surveys (for 

example, exhibiting indicators of high transmissivity over an impermeable layer). 

If uplands separating a wetland from jurisdictional water can reasonably be characterized 

as “man-made dikes or barriers, natural river berms, beach dunes, and the like,” then, under the 

agencies’ regulations, the wetlands are adjacent even if no apparent hydrologic connection exists. 

It is important to note that natural river berms are formed by sediment deposits accumulating at 

or near the stream bank during flood events. Such berms vary in height from inches to feet, and 

also can be quite wide.37 Similarly, multiple beach dunes may exist between a wetland and 

jurisdictional water (including primary and secondary dunes), because beach dunes typically 

function as an interdunal system (particularly on barrier islands). 

The link between physical proximity and a physical or ecological (biological) connection 

is well documented in the scientific literature. A wetland within the riparian area38 or 

floodplain39 typically has such an interconnection. For example, adjacent wetlands typically help 

to store floodwaters, pollutants, and sediments that could otherwise reach a jurisdictional water.40 

Adjacent wetlands often provide important sources of stored water that augment stream flow 

during low-flow periods.41 Species, such as amphibians, certain reptiles (e.g., watersnakes), 

waterfowl, invertebrates, and fish (including anadromous and catadromous fish), move between 

an adjacent wetland and a jurisdictional water for spawning, nesting, feeding, refuge, and other 

life stage requirements.42 Species that move between an adjacent wetland and a jurisdictional 

water are distinguishable from migratory species. Migratory species use the wetland during a 

journey to a different area43 and are not to be used as a scientific basis for demonstrating an 

ecological interconnection for adjacency. While it is not appropriate to determine adjacency 

based solely on any specific threshold of distance, as the distance between the wetland and 

jurisdictional water increases, the potential interconnection between the waters will decrease and 

a finding of adjacency is less likely. The distance between a tributary and its adjacent wetlands 

may vary by region, as well as based on site-specific factors within regions. 

All wetlands within a wetland mosaic should ordinarily be considered collectively when 

determining adjacency. Wetlands present in such systems act generally as a single ecological 

17
 
unit. A “wetland mosaic” refers to a landscape where wetland and non-wetland components are 

too numerous and closely associated to be appropriately delineated or mapped separately. These 

areas often have complex microtopography, with repeated small changes in elevation occurring 

over short distances. Tops of ridges and hummocks are often non-wetland but are interspersed 

with wetlands having hydrophytic vegetation, hydric soils, and wetland hydrology. 

Under Justice Kennedy’s standard, the following legal test for Clean Water Act 

jurisdiction applies: If a wetland is adjacent to a traditional navigable water or a non-wetland 

interstate water, a finding of adjacency is sufficient in and of itself to demonstrate that the 

wetland is subject to Clean Water Act jurisdiction. On the other hand, a finding that a particular 

wetland is adjacent to a jurisdictional waterbody other than a traditional navigable water or nonwetland interstate water is not sufficient in and of itself to establish Clean Water Act jurisdiction 

over that wetland. For the latter category of adjacent wetlands, in order to establish Clean Water 

Act jurisdiction, field staff, on a case-by-case basis, must determine whether the particular 

adjacent wetland, alone or in combination with similarly situated wetlands in that watershed, has 

a significant nexus with traditional navigable waters or non-wetland interstate waters (see 

discussion below). 

A determination of adjacency is based on an evaluation of the relationship between a 

wetland and the nearest jurisdictional water, which includes consideration of both physical and 

ecological connections between those waterbodies. In contrast, a determination of significant 

nexus is a different inquiry, which is based on evaluating whether there is a significant nexus 

between that adjacent wetland (in combination with similarly situated adjacent wetlands in the 

watershed) and a traditional navigable water or a non-wetland interstate water. 

As discussed in Section 3, the agencies generally consider all wetlands within the 

watershed that are adjacent to jurisdictional waters to be “similarly situated” waters “in the 

region.” (Wetlands adjacent to non-jurisdictional waters are considered “other waters.”) The 

relevant watershed is defined by the topographic area draining into the nearest traditional 

navigable water or interstate water. However, as with tributaries, field staff may utilize a smaller 

area for a significant nexus analysis where this is sufficient to establish the presence or absence 

of a significant nexus for adjacent wetlands within the watershed as a whole. When identifying 

other adjacent wetlands in the watershed to be considered in the significant nexus analysis, field 

staff may use resources such as direct observation or U.S. Geological Survey maps, aerial 

photography, or other reliable remote sensing information. Using such information, staff should 

include in the evaluation as many adjacent wetlands as is necessary to support and document the 

presence or absence of a significant nexus. Field staff are not required to identify or evaluate 

every adjacent wetland located within a particular watershed being assessed and are generally 

not expected to develop new information on the location of such wetlands. As with tributaries, 

field staff should use the best available information on the adjacent wetlands in the point of entry 

watershed, which may include scientific literature on the functions and effects of wetlands within 

the watershed generally and how those wetlands significantly affect the physical, chemical, or 

biological integrity of the traditional navigable waters or interstate waters. For affirmative 

determinations especially, consideration of a subset of adjacent wetlands may be sufficient, since 

including additional adjacent wetlands in the analysis would only establish a more significant 

nexus to the traditional navigable water or interstate water. 

18
 
When evaluating significant nexus for adjacent wetlands, field staff should consider the 

many functions of waters such as sediment trapping, nutrient recycling, pollutant trapping and 

filtering, retention or attenuation of flood waters, runoff storage, and provision of habitat. In 

general, tributaries and their adjacent wetlands function as an integrated hydrologic system, and 

as a unit they may affect the amount of pollutants and floodwaters that reach the downstream 

traditional navigable waters or interstate waters. 

Section 6: Other Waters 

The “other waters” or “(a)(3) waters” provision of EPA’s and the Corps regulations 

includes: 

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. . . . 44 

The agencies recognize that Supreme Court decisions in SWANCC and Rapanos have 

identified limitations on the scope of (a)(3) waters that may be determined to be jurisdictional 

under the CWA. The agencies expect to further clarify the scope of waters subject to CWA 

jurisdiction, including jurisdiction over (a)(3) waters after SWANCC and Rapanos, as part of a 

notice and comment rulemaking. In the meantime, the agencies will make case-by-case, factspecific determinations of jurisdiction under (a)(3) in the manner discussed below. 

Physically Proximate Other Waters 

EPA and the Corps will make fact-specific determinations of jurisdiction for other waters 

that are in close physical proximity to traditional navigable waters, interstate waters, or their 

jurisdictional tributaries, and that alone or in combination with similarly situated proximate other 

waters in the region significantly affect the chemical, physical, or biological integrity of 

traditional navigable waters or interstate waters. For purposes of this guidance, proximate other 

waters are non-wetland waters that would satisfy the regulatory definition of “adjacent” if they 

were wetlands. They include lakes, ponds, and other non-wetland waters that are bordering, 

contiguous, or neighboring to jurisdictional waters, including waters that are separated from 

jurisdictional waters by man-made dikes or barriers, natural river berms, beach dunes and the 

like. Such waters have many of the same functions and effects with respect to jurisdictional 

waters as adjacent wetlands. The agencies believe it is scientifically appropriate and consistent 

with Justice Kennedy’s opinion to evaluate significant nexus for such waters in the same manner 

as for adjacent wetlands. 

For purposes of the significant nexus analysis, all physically proximate other waters in 

the same point-of-entry watershed should be evaluated together as similarly situated waters in 

the region. This is appropriate for the same reasons as it is appropriate to evaluate all adjacent 

wetlands in the point-of-entry watershed together as similarly situated waters. 

19
 
Other Waters that Are Not Physically Proximate to Jurisdictional Waters 

Non-physically proximate other waters are isolated, intrastate, non-navigable waters and 

wetlands that would not meet the regulatory definition of “adjacent” with respect to jurisdictional 

waters. The agencies note that the (a)(3) provisions of our regulations remain in effect and that 

the SWANCC decision specifically addressed only the presence of migratory birds as a basis for 

asserting jurisdiction, and not the validity of the (a)(3) provisions generally. However, the 

agencies interpret Justice Kennedy’s opinion as suggesting that the same significant nexus 

standard that he articulated for adjacent wetlands is appropriate for (a)(3) waters, and we have 

thus clarified above how this standard should be applied in the case of (a)(3) waters that are in 

close physical proximity to jurisdictional waters. At the same time, we recognize that for other 

waters that are geographically separated from jurisdictional tributaries, establishing a significant 

nexus may be more challenging. Thus, at this time, we are not providing specific guidance on 

making such determinations and are instead directing agency field staff to continue the current 

practice of referring determinations for non-physically proximate other waters to their respective 

Headquarters and obtaining formal project-specific approval before asserting or denying 

jurisdiction. 

The general approach for determining significant nexus for such waters would be the 

same as discussed in Section 3. Because such waters may be widely scattered geographically, 

and physically remote from jurisdictional waters, field staff should generally conduct significant 

nexus analyses for such waters individually, unless there is a compelling scientific basis for 

treating a group of such waters as similarly situated waters in the same region. In accordance 

with the decision in SWANCC, consideration of use by migratory species is not relevant to the 

significant nexus determination for such waters. 

The agencies emphasize that this document is guidance, which lacks the force of law; the 

agencies expect to proceed with notice and comment rulemaking to further clarify the regulatory 

definition of the term “waters of the United States.” As a part of that process, we will further 

consider, based on a review of the scientific literature, how a significant nexus analysis should be 

conducted for non-physically proximate other waters. 

Section 7: Waters Generally Not Jurisdictional 

The scope of “waters of the United States” does not include all waters. EPA and the 

Corps previously have described in preambles to CWA regulations waters that the agencies 

generally do not consider to be waters of the U.S.45 The agencies’ position regarding these 

waters is unchanged. The categories of waters generally not “waters of the U.S.” include: 

•	 Wet areas that are not tributaries or open waters and do not meet the regulatory definition 

of wetlands.46 

•	 Waterbodies excluded from coverage under the CWA by existing regulations. 

•	 Waters that lack a significant nexus when one is required for jurisdiction. 

20
 
•	 Artificially irrigated areas which would revert to upland if the irrigation ceased. 

•	 Artificial lakes or ponds created by excavating and/or diking dry land to collect and retain 

water and which are used exclusively for such purposes as stock watering, irrigation, 

settling basins, or rice growing. 

•	 Artificial reflecting pools or swimming pools excavated in uplands. 

•	 Small ornamental bodies of water created by excavating and/or diking dry land to retain 

water for primarily aesthetic reasons. 

•	 Water-filled depressions created in dry land incidental to construction activity and pits 

excavated in dry land for the purpose of obtaining fill, sand, or gravel, unless and until 

the construction or excavation operation is abandoned and the resulting body of water 

meets the definition of waters of the United States. 

•	 Groundwater drained through subsurface drainage systems.xii 

•	 Erosional features (gullies and rills), and swales and ditches that are not tributaries or 

wetlands (see Section 4). 

Section 8: Documentation 

EPA and Corps field staff should document in the administrative record the available 

information supporting a jurisdictional determination. In addition to location and other 

descriptive information regarding the water at issue, the record should include a clear 

explanation of the rationale for the jurisdictional conclusion, and include, as appropriate: 

•	 Information leading to a conclusion that a water falls within a category considered in this 

guidance to be jurisdictional without the need to demonstrate a significant nexus; 

•	 Information used to conclude that a water has a significant nexus when one is required 

for jurisdiction; 

•	 Information supporting a conclusion that a water lacks a significant nexus, when one is 

required for jurisdiction; or 

•	 Information supporting a conclusion that a water falls within one of the categories of 

geographic features generally considered non-jurisdictional. 

In short, both affirmative and negative jurisdictional determinations should be welldocumented, to ensure both public transparency and defensibility should a jurisdictional 

 

xii A “subsurface” drainage system is an agricultural practice designed to drain subsurface water through a below 

ground pipe system in order to maintain the groundwater table below the root zone to facilitate crop production. The 

construction or maintenance of subsurface drain systems may require a CWA permit, if it involves discharges of 

dredged or fill material into waters of the U.S. 

21
 
 

conclusion be challenged. The level of documentation may be greater for jurisdictional 

determinations associated with complex projects. 

Other sections of this guidance discuss the findings necessary for particular categories of 

waters to be considered jurisdictional and/or to have a significant nexus. Information relevant to 

these findings can come from many sources, including but not limited to maps, aerial 

photography, soil surveys, watershed studies, local development plans, literature citations, and 

references from studies pertinent to the parameters being reviewed. 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 

jurisdictional 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 important to supplement such information with field 

observation. 

An important part of a jurisdictional analysis is the location and type of water under 

consideration, so as to readily determine if the jurisdictional status of similarly situated waters in 

the region has been previously determined. If so, the jurisdictional conclusion, rationale, and 

supporting information for a similarly situated water are directly relevant. As Justice Kennedy 

noted in Rapanos, where a significant nexus has been established for a particular wetland, “it 

may be permissible, as a matter of administrative convenience or necessity, to presume covered 

status for other comparable wetlands in the region.”47 Therefore, once the jurisdictional status 

for a particular water within a watershed has been established, field staff can apply the 

significant nexus analysis for that water to any subsequent determinations if they establish (and 

document) that the water at issue is the same type and in the same watershed as the jurisdictional 

water. 

22
 
APPENDIX 

DISCUSSION OF LEGAL AND SCIENTIFIC BASIS FOR 

GUIDANCE SECTIONS 

The U.S. Supreme Court has addressed the scope of waters of the United States protected 

by the CWA in three cases. In United States v. Riverside Bayview Homes, Inc. (474 U.S. 121 

(1985)), the Supreme Court held that wetlands adjacent to a traditional navigable water were 

properly considered to be “waters of the United States.” In SWANCC, the Court addressed the 

question of CWA jurisdiction over isolated, non-navigable, intrastate ponds, and concluded that 

CWA jurisdiction could not be based solely on the presence of migratory birds. In Rapanos, the 

Court addressed CWA protections for wetlands adjacent to non-navigable tributaries, and issued 

five opinions with no single opinion commanding a majority of the Court. The plurality opinion, 

authored by Justice Scalia, stated that “waters of the United States” extended beyond traditional 

navigable waters to include “relatively permanent, standing or flowing bodies of water.”48 The 

plurality went on to clarify that relatively permanent waters ”do not necessarily exclude” 

streams, rivers, or lakes that might dry up in extraordinary circumstances, such as drought, and 

seasonal rivers, which contain continuous flow during some months of the year but no flow 

during dry months. The plurality opinion also asserted that only wetlands with a “continuous 

surface connection” to other jurisdictional waters are considered “adjacent” and protected by the 

CWA.49 Justice Kennedy’s concurring opinion took a different approach than Justice Scalia’s. 

Justice Kennedy concluded that “waters of the United States” included wetlands that had a 

significant nexus to traditional navigable waters, “if the wetlands, 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). 

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 (id. at 810). Neither SWANCC nor the opinions in 

Rapanos invalidated any of the regulatory provisions defining “waters of the United States.” 

Section 1: Traditional Navigable Waters 

Legal Basis 

The Supreme Court has recognized that navigability is a flexible concept and “[e]ach 

application of [the Daniel Ball test] . . . is apt to uncover variations and refinements which 

require further elaboration.”50 EPA and the Corps will be guided by examples of the types of 

evidence found relevant and sufficient for a traditional navigable waters determination in court 

decisions, although these will be fact-specific determinations and not every type of evidence will 

be available or needed in every circumstance. Field staff have sought guidance in particular on 

how to determine whether a water is susceptible to being used for commercial navigation such 

that it is a traditional navigable water. The cases discussed below provide specific examples of 

the types of evidence courts have found sufficient to demonstrate such susceptibility. 

23
 
 

 

 

 In FPL Energy Marine Hydro L.L.C. v. FERC, a case involving the Federal Power Act, 

the U.S. Court of Appeals for the District of Columbia 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.”51 In that case, the D.C. Circuit upheld a Federal Energy 

Regulatory Commission navigability determination that was based upon three experimental 

canoe trips taken specifically to demonstrate the river’s navigability.52 The navigability 

determination was affirmed although the stream had five sets of rapids, and all parties agreed that 

the stream has never been used for commercial traffic, that there was no evidence of recreational 

use of the stream, and that the only evidence indicating actual use of the stream came from the 

three trips made for the purpose of litigation.53 

The U.S Court of Appeals for the Ninth 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. In Alaska v. Ahtna, Inc., the Ninth Circuit held that current use of an 

Alaskan river for commercial recreational boating is sufficient evidence of the water’s capacity 

to carry waterborne commerce at the time that Alaska became a state.54 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 recreational boating showed that the river always had the capacity to 

support navigation by the types of boats that were in use at the time of statehood.55 Here, the 

stream was found to be navigable although the shallowest part of the river is just a foot deep 

during the low season; the river is customarily used, or is susceptible to use, by watercraft such 

as powerboats, 12-foot-long inflatable rafts, and motorized freight canoes and double-ended 

paddle canoes; hunters and fishermen travelled the river by boat in the past; most of the use of 

the river is recreational; and it is possible to take guided fishing and sightseeing trips on the 

river.56 

Section 2: Interstate Waters 

Legal Basis 

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.xiii 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. 

xiii See endnote 13. Section 2(d)(1) of the Water Pollution Control Act of 1948, 62 Stat. at 1156, stated: 

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 hereby declared to be a public nuisance and subject to abatement as 

herein provided. 

24
 

Other provisions of the statute provide additional textual evidence of the scope of the 

primary jurisdictional term of the Act. Congress defined “navigable waters” in CWA section 

502(7) to mean “the waters of the United States, including the territorial seas.” Interstate waters 

are the waters of the several States and, thus, the United States. While the 1972 Act was clearly 

not limited to interstate waters, it was equally clearly intended to include interstate waters. 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, including “interstate waters.” CWA section 303(a)(1) states: 

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. . . . 

(Emphasis added.) Thus, Congress intended continued protection of interstate waters. 

While EPA and the Corps believe congressional intent is clear, the agencies also have a 

longstanding regulatory interpretation that interstate waters fall within the scope of CWA 

jurisdiction.57 The agencies’ interpretation was promulgated contemporaneously with the 

passage of the CWA and is consistent with the statutory and legislative history of the Act. 

Furthermore, the Supreme Court has never addressed the CWA’s coverage of interstate waters, 

and its decisions in SWANCC and Rapanos do not question the jurisdictional status of interstate 

waters or impose additional jurisdictional requirements on interstate waters. 

As noted above, the precursor statutes to the CWA always subjected interstate waters and 

their tributaries to federal jurisdiction. While Congress intended tributaries to interstate waters to 

be subject to the CWA, the statute does not define the extent of tributaries that are covered. In 

light of Justice Kennedy’s opinion, the agencies believe it is reasonable to assert jurisdiction over 

tributaries, adjacent wetlands and other waters which 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 (see sections 4, 5, 

and 6 of this guidance for additional information). 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 covered waters have important 

beneficial effects on those waters, and by recognizing that polluting or destroying waters with a 

significant nexus can harm downstream covered waters. 

Section 3: Significant Nexus 

Legal and Scientific Basis 

25
 
 

 

In Rapanos, Justice Kennedy provides an approach for determining what constitutes a 

“significant nexus” that can serve as a basis for statutory jurisdiction.xiv “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,’ §§ 1311(a), 1362(12).”58 Justice Kennedy provided further guidance 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 [wetlands] in the region, significantly affect the chemical, physical, and 

biological integrity of other covered waters more readily understood as ‘navigable.’”59 While 

Justice Kennedy focused on adjacent wetlands in light of the facts of the cases before him, it is 

reasonable to utilize the same analysis for tributaries and other waters such as ponds, lakes and 

non-adjacent wetlands that are not themselves directly connected to a tributary system but may 

still have a significant nexus to a traditional navigable water or interstate water. 

In determining which waters to consider “similarly situated” for purposes of analyzing 

whether they have a significant nexus “in combination” with the water at issue, it is reasonable to 

begin with the categories of waters the agencies identified in promulgating their definition of 

“water of the United States.” For example, tributaries are similarly situated within the landscape 

because they are part of a stream network that provides flow to the downstream traditional 

navigable water or interstate water. Adjacent wetlands are similarly situated within the landscape 

because the agencies’ definition is focused on their proximity to another water of the United 

States – “adjacent” is defined in regulations as bordering, neighboring or contiguous (see Section 

5 for further discussion). Similarly, other waters (“(a)(3) waters”) that are in close physical 

proximity to traditional navigable or interstate waters or their tributaries are similarly situated 

with respect to those waters in much the same way as adjacent wetlands. Justice Kennedy’s 

standard allows the agencies to analyze whether all similarly situated waters in a region together 

have a significant nexus to the downstream traditional navigable water. With this standard, 

Justice Kennedy has recognized that even where it is difficult to demonstrate that a particular 

individual wetland adjacent to a small headwater tributary has a significant nexus to a traditional 

navigable water, the destruction of all such adjacent wetlands in a region could have a significant 

effect on the traditional navigable water and, thus, the CWA must protect those wetlands in order 

to protect the traditional navigable water. The same logic applies to tributaries and physically 

proximate other waters. 

Waters should generally be considered “in the region” if they are within a watershed that 

drains to a traditional navigable water or interstate water, defined by the point at which a 

tributary system first enters a traditional navigable water or interstate water. 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 

xiv 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 concludes that Riverside Bayview and SWANCC “establish the framework for” 

determining whether an assertion of jurisdiction constitutes a reasonable interpretation of “navigable waters” - “the 

connection between a nonnavigable 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”; “[a]bsent a significant nexus, 

jurisdiction under the Act is lacking.” 547 U.S. at 767. 

26
 
  

management.60 Anthropogenic actions and natural events can have widespread effects within the 

watershed that collectively impact the quality of the relevant traditional navigable water or 

interstate water.61 For this reason, 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 that contributes flow to the point of entry to a traditional navigable or 

interstate water is a logical spatial framework for the evaluation of the nexus. The functions of 

the contributing waters are inextricably linked and have a cumulative effect on the integrity of 

the traditional navigable water or interstate water. The size of that watershed can be determined 

by identifying the topographic area that drains to the nearest traditional navigable water or 

interstate water, and then using that point of entry watershed to conduct a significant nexus 

evaluation.62 

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, runoff storage, and provision of 

habitat.63 Furthermore, Justice Kennedy noted that a hydrologic connection is not necessary to 

establish a significant nexus, because in some cases the lack of 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.64 Finally, Justice Kennedy was clear that the requisite nexus must be more than 

“speculative or insubstantial”65 in order to be significant. 

Section 4: Tributaries 

Legal and Scientific Basis 

Tributaries Covered Under the Rapanos Plurality Standard 

As noted above, jurisdictional determinations based on the plurality standard would have 

the support of the four justices joining the plurality opinion as well as the four dissenting 

justices. The plurality concluded that the agencies’ regulatory authority should extend only to 

“relatively permanent, standing or continuously flowing bodies of water”66 connected to 

traditional navigable waters, and to “wetlands with a continuous surface connection to” such 

relatively permanent waters.67 “Relatively permanent waters” were described as waters that 

typically flow year-round except in times of drought, or waters that have a continuous flow at 

least seasonally. The plurality opinion emphasized that relatively permanent waters do not 

include tributaries “whose flow is ‘[c]oming and going at intervals . . . [b]roken, fitful.’”68 

Therefore, “relatively permanent waters” do not include ephemeral tributaries which flow only in 

response to precipitation and intermittent streams which do not have continuous flow at least 

seasonally.xv 

 

xv Note that under the Kennedy standard, such waters may be jurisdictional where they have a significant nexus. 

27
 
 

 

 

 

 

 

Moreover, waters that have had at least seasonal flow on a historic basis remain 

jurisdictional despite the fact that man-made diversions for irrigation, water supply or other 

reasons have caused a tributary, or portion thereof, to flow less than seasonally.xvi 

Field staff have flexibility to determine what seasonal flow means in each particular 

case.69 Seasonal flow can be the result of snow melt, seasonal patterns in precipitation, and 

seasonal fluctuations in ground water levels. In the arid west, stream discharges are driven by 

three large-scale weather patterns.70 Precipitation produced by these weather patterns varies 

greatly for any given locality, but generally, precipitation shifts from winter in the north to 

summer in the south. The variation of precipitation in time, coupled with the highly variable 

topography of the arid west, results in spatially variable precipitation patterns.71 For example, 

seasonal flow in most of New Mexico and large portions of Arizona and Colorado would be 

during the period of two months, July and August, when they normally receive between 30-50 

percent of their annual precipitation as rain.72 In some areas, snow melt drives stream flow, and 

seasonal flow is typically in the spring.73 Seasonal patterns of flow may be less pronounced in 

the semi-arid Midwest, perhaps because of less seasonal precipitation patterns and relatively 

more vegetative cover.74 In the east precipitation is more uniform but increased 

evapotranspiration during the growing season can reduce ground water levels and surface flows 

to create seasonal and ephemeral flows.75 

Tributaries Covered Under the Rapanos Kennedy Standard 

Justice Kennedy rejected the plurality’s approach that only “relatively permanent” 

tributaries are within the scope of CWA jurisdiction. 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 states that Congress has done “[q]uite the opposite.”76 Further, Justice 

Kennedy concludes, based on “a full reading of the dictionary definition” of “water,” that “the 

Corps can reasonably interpret the Act to cover the paths of such impermanent streams.”xvii 

Even in Justice Kennedy’s rejection of Justice Stevens' opinion it is clear that he was specifically 

rejecting the broad scope of jurisdiction over wetlands without further analysis, and not 

specifically addressing jurisdiction over tributaries: “[T]he dissent would permit federal 

regulation whenever wetlands lie alongside a ditch or drain, however remote and insubstantial, 

that eventually may flow into traditional navigable waters. The deference owed to the Corps’ 

interpretation of the statute does not extend so far.”77 

Elsewhere, Justice Kennedy suggests that it may be appropriate to assert jurisdiction over 

all tributaries with an ordinary high-water mark. Justice Kennedy described the Corps’ standard 

xvi 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."). 

xvii 547 U.S. at 770. First, Justice Kennedy notes that the term “waters” can mean “‘flood or inundation,’” according 

to the Webster’s Second definition, and that these events are “impermanent by definition.” Id. Second, even looking 

to the plurality’s preferred dictionary definition of “waters,” i.e., “‘water “[a]s found in streams and bodies forming 

geographical features such as oceans, rivers, [and] lakes,”’” Justice Kennedy notes that “intermittent flow can 

constitute a stream.” Id. (alteration in original). And finally, Justice Kennedy notes that the plurality’s reference to 

the statement by the Riverside Bayview Court comparing “wetlands to ‘rivers, streams, and other hydrographic 

features more conventionally identifiable as “waters”’ . . . .could just as well refer to intermittent streams.” Id. at 

771 (citations omitted). 

28
 
for asserting jurisdiction over tributaries: “[T]he 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 . . . 

.”78 Justice Kennedy concluded that this standard “presumably provides a rough measure of the 

volume and regularity of flow.”79 In addition, if it is applied reasonably consistently, the Corps’ 

existing standard for tributaries “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.”80 Thus, Justice Kennedy’s opinion may reasonably be read as allowing 

the agencies to determine that a case-specific significant nexus determination is not necessary for 

tributaries possessing an ordinary high water mark, though it also indicates that he considers the 

presence of a significant nexus to be the appropriate test. 

The agencies have decided that, given Justice Kennedy’s indication that significant nexus 

is still the guiding standard, it is appropriate for purposes of this guidance to assert jurisdiction 

over tributaries utilizing the same standard Justice Kennedy articulated for adjacent wetlands. In 

establishing the significant nexus standard, Justice Kennedy recognized that upstream adjacent 

wetlands can have significant effects on the physical, chemical and biological integrity of 

downstream waters covered under the CWA. As a scientific matter, tributaries can, of course, 

have similar effects and it is reasonable to utilize the same standard for determining whether 

tributaries have a significant nexus to downstream covered waters. Through rule making, the 

agencies will further consider whether the existence of an ordinary high-water mark alone is 

sufficient to establish a significant nexus to downstream traditional navigable or interstate 

waters, without requiring a site-specific analysis, as Justice Kennedy invites in his opinion. 

As noted in Section 3, it is reasonable to consider all tributaries in a watershed to be 

“similarly situated” for purposes of a significant nexus analysis because they contribute flow to 

the downstream traditional navigable water or interstate water and provide similar functions to 

those downstream waters. Further, Section 3 demonstrated that it is reasonable to consider the 

region for significant nexus analysis to be a watershed defined by the area draining into the 

nearest traditional navigable water or interstate water through a single point of entry. 

The agencies’ identification of the presence of an ordinary high water mark as one of the 

factors for considering a water to be a tributary for purposes of this guidance is consistent with 

Justice Kennedy’s observation that an ordinary high water mark may be a reasonable measure of 

whether a tributary possesses a significant nexus with a traditional navigable water or interstate 

water. This observation, in turn, is supported by both the agencies’ scientific judgment in the 

past and the scientific literature of the present. As the Corps stated in promulgating the 

definition of “waters of the U.S.” in 1977 to include tributaries, “[t]he regulation of activities that 

cause water pollution cannot rely on . . . artificial lines, however, but must focus on all waters 

that together form the entire aquatic ecosystem. Water moves in hydrologic cycles, and the 

pollution of . . . part of the aquatic ecosystem . . . will affect the water quality of the other 

waters within that aquatic ecosystem.”81 For more than 30 years, EPA and the Corps have 

interpreted the CWA to protect “the many tributary streams that feed into the tidal and 

commercially navigable waters . . . since the destruction and/or degradation of the physical, 

chemical, and biological integrity of each of these waters is threatened by the unregulated 

discharge of dredged or fill material.”82 As Congress and the Supreme Court have recognized, 

29
 
 

 

“‘[w]ater moves in hydrologic cycles and it is essential that discharge of pollutants be controlled 

at the source.’”83 

A large volume of scientific literature documents the important functions that tributaries, 

including headwater streams, provide to downstream waters.xviii Headwater streams, which may 

include perennial, intermittent, and ephemeral streams, are the most common streams in the 

United States. Collectively, they determine the chemical, physical, and biological integrity of 

downstream waters, and provide many of the same functions as non-headwater streams.84 

Headwater streams reduce the amount of sediment delivered to downstream waters by trapping 

sediment from water and runoff.85 Headwater streams are responsible for most nutrient cycling 

and removal, and thus transforming and changing the amount of nutrients delivered to 

downstream waters.86 A close connection exists between the water quality of these streams and 

the water quality of downstream water bodies.87 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.88 These streams provide 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, including traditional navigable waters, for other portions of their life stages.89 They also 

serve as migratory corridors for fish. Tributaries can improve or maintain biological integrity 

and control water temperatures in the downstream waters. 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.90 Disruptions in 

these biological processes affect the ecological functions of the entire downstream system.91 

Headwater streams help to maintain base flow in the larger rivers downstream, which is 

particularly important in times of drought. 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.92 

Section 5: Adjacent Wetlands 

Legal and Scientific Basis 

Adjacent Wetlands Covered under the Rapanos Plurality Standard 

Under the plurality standard, wetlands that have a continuous surface connection with a 

relatively permanent, non-navigable tributary are jurisdictional without the need for a significant 

nexus finding. The plurality opinion indicates that “continuous surface connection” is a 

“physical connection requirement.”93 A continuous surface connection does not, however, 

require surface water to be continuously present between the wetland and the tributary. 

Adjacent Wetlands Covered under the Rapanos Kennedy Standard 

 

xviii For purposes of applying the current body of scientific literature to the questions created by the Rapanos 

Supreme Court decision, traditional navigable waters can be considered analogous to downstream waters. This is 

because the vast majority of traditional navigable waters are downstream of headwater streams. 

30
 
 

 

 

 

Because the question in Rapanos was whether particular adjacent wetlands were “waters 

of the U.S.,” Justice Kennedy’s opinion focused on the standard for determining whether 

wetlands have the requisite nexus: 

With respect to wetlands, the rationale for Clean Water Act regulation is, as the 

Corps has recognized, that wetlands can perform critical functions related to the 

integrity of other waters—functions such as pollutant trapping, flood control, and 

runoff storage. 33 CFR § 320.4(b)(2). Accordingly, wetlands possess the requisite 

nexus, and thus come within the statutory phrase “navigable waters,” if the 

wetlands, 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.” When, in contrast, 

wetlands’ effects on water quality are speculative or insubstantial, they fall 

outside the zone fairly encompassed by the statutory term “navigable waters.”94 

With respect to wetlands adjacent to traditional navigable waters, Justice Kennedy 

concluded that the agencies’ 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.”95 The agencies will apply Justice Kennedy’s reasoning to 

conclude wetlands adjacent to non-wetland interstate waters are similarly jurisdictional without 

the need of demonstrating a significant nexus. 

For wetlands adjacent to tributaries that have a significant nexus to a traditional navigable 

water or interstate water, however, absent more specific regulations, the agencies must establish 

that the wetland alone or in combination with other adjacent wetlands in the watershed has a 

significant nexus to a traditional navigable water or interstate water. Justice Kennedy provided 

some guidance as to the analysis necessary to conclude that a water has a sufficient nexus. 

Justice Kennedy’s concern was that neither the Corps nor the reviewing courts applied the proper 

legal standard.xix Although evidence was presented in one of the consolidated cases that the 

wetlands were providing habitat, sediment trapping, nutrient recycling, flood peak diminution 

and reduction, and flow water augmentation, the Corps did not marshall this evidence to 

conclude that the wetlands had a significant nexus to downstream traditional navigable waters.96 

The administrative record in the other case noted the wetland’s connection to wildlife habitat and 

water quality and “also noted that the project would have a major, long-term detrimental effect 

on wetlands, flood retention, recreation and conservation and overall ecology.”97 Justice 

Kennedy did not indicate that this evidence was irrelevant, in fact, he concluded that “[m]uch the 

same evidence” previously analyzed by the Corps could establish a significant nexus with 

traditional navigable waters, particularly with additional evidence about the connection between 

the wetlands and the navigable water.98 

A hydrologic connection is neither determinative of nor required to show a significant 

nexus. Justice Kennedy noted that a “mere hydrologic connection should not suffice in all cases; 

xix Justice Kennedy thought that in both the consolidated cases before the Supreme Court, “the record contains 

evidence suggesting the possible existence of a significant nexus according to the principles outlined above. Thus 

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.” 547 U.S. at 783. 

31
 
 

 

the connection may be too insubstantial for the hydrologic linkage to establish the required nexus 

with navigable waters as traditionally understood.”99 On the other hand, Justice Kennedy was 

also clear that a hydrologic connection between a wetland and a tributary is not required to 

establish a significant nexus: “Given the role wetlands play in pollutant filtering, flood control, 

and runoff storage, it may well be the absence of hydrologic connection (in the sense of 

interchange of waters) that shows the wetlands’ significance for the aquatic system.”100 

Section 6: Other Waters 

Legal and Scientific Basis 

 Other waters are those for which jurisdiction was previously asserted under section 

(a)(3) of the Corps’ regulations, which provide for CWA jurisdiction over “[a]ll other waters . . . 

the use, degradation, or destruction of which could affect interstate or foreign commerce. . . .” 

These include isolated, non-navigable intrastate waters. This provision of the regulations was 

the focus of the SWANCC decision. In that case, the Court was considering the validity of the 

Corps’ assertion of jurisdiction over ponds and mudflats under (a)(3). In rejecting the assertion 

of jurisdiction in that case, the Court held that “[i]t was the significant nexus between the 

wetlands and ‘navigable waters’ that informed our reading of the CWA in Riverside Bayview 

Homes.”101 Justice Kennedy further explained the SWANCC decision – and his understanding of 

when EPA and the Corps could assert jurisdiction over “other waters” – 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.”102 

Because 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, it is reasonable to 

conclude that Justice Kennedy intends his significant nexus standard to apply to the “other 

waters” of this regulation. 

An “other water” is jurisdictional only if it both has a significant nexus to a traditional 

navigable water or interstate water and meets the regulatory definition. One of the ways of 

demonstrating that a water is one “the use, degradation or destruction of which could affect 

interstate or foreign commerce” is through demonstration that the water has a significant nexus 

to a traditional navigable water or interstate water. If a water meets Justice Kennedy’s 

significant nexus standard, the degradation or destruction of that water could harm the traditional 

navigable water or interstate water and therefore could affect interstate or foreign commerce. 

While all adjacent wetlands are reasonably proximate to a jurisdictional water by 

regulation and, therefore, “similarly situated,” the other waters provision of the regulations 

encompasses a wide-range of waters. For purposes of this guidance, the agencies have decided 

that it is appropriate to divide other waters into two classes, those that are physically proximate 

to traditional navigable or interstate waters or their tributaries, and those that are not. For the 

first group, it is reasonable to treat these in much the same manner as adjacent wetlands, since 

they stand in the same relationship to and serve many of the same functions as such wetlands 

with respect to the aquatic systems that they are near. For instance, physically proximate waters 

32
 
can function to retain floodwaters, recharge groundwater, provide habitat for waterfowl and other 

species, and process and retain nutrients and pollutants that may otherwise enter tributaries; they 

may even be connected to a river during high floods and provide a protected habitat for eggs and 

young of many fish species, as well as provide refuge for spawning for some species.103 

For the reasons articulated in Section 3 of this guidance, the agencies will interpret “in 

the region” for such proximate other waters to be the watershed boundary defined by the 

geographic area that drains to the nearest downstream traditional navigable or interstate water 

through a single point of entry. 

 In applying the significant nexus standard to such waters, it is important to note that 

Justice Kennedy concluded that a water may have a significant nexus even if it does not have a 

hydrologic connection to the traditional navigable water or interstate water: “Given the role 

wetlands play in pollutant filtering, flood control, and runoff storage, it may well be the absence 

of a hydrologic connection (in the sense of interchange of waters) that shows the wetlands’ 

significance for the aquatic system.”104 This statement applies equally to proximate other waters. 

Thus, effects that should be considered include circumstances where proximate other waters trap 

pollutants such as nutrients or sediment, for example, or where they hold precipitation or snow 

melt, thereby reducing contamination or flooding of traditional navigable or interstate waters. 

In contrast, applying the significant nexus standard to geographically isolated other 

waters is more challenging. Justice Kennedy recognized that physical proximity can be an 

important factor in the analysis of significant nexus.xx In light of the challenges in applying the 

significant nexus standard to geographically isolated other waters, the agencies have identified 

physical proximity as an important factor when conducting a significant nexus analysis for such 

waters. 

The agencies believe that the significant nexus test articulated by Justice Kennedy is the 

right theoretical approach for assessing all other waters, isolated and proximate, but because of 

the greater practical difficulty of applying this standard to geographically isolated other waters, 

we are directing field staff to continue for now the current practice of referring determinations 

for non-physically proximate other waters to their respective Headquarters and obtaining formal 

project-specific approval before asserting or denying jurisdiction. Because such waters are often 

geographically dispersed and isolated from each other, as well as from other jurisdictional 

waters, it is also not clear at this time how such waters should be grouped for purposes of 

considering them “similarly situated” and “in the region.” For this reason, until the agencies are 

able to further consider this issue through rule making, significant nexus determination will 

generally evaluate such waters individually, unless there is a compelling scientific basis for 

treating a group of such waters as similarly situated waters in the same region. In accordance 

with the decision in SWANCC, consideration of use by migratory species is not relevant to the 

significant nexus determination for such waters. 

 

xx "Through regulations 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.” 547 U.S. at 780. 

33
 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

ENDNOTES 

1 The Federal Water Pollution Control Act Amendments of 1972, Pub. L. No. 92-500, 86 Stat. 816. The 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 changed the popular name of the statute to the “Clean 

Water Act.” See Pub. L. No. 95-217, 91 Stat. 1566; 33 U.S.C. 1251 note. The current FWPCA is codified at 33 

U.S.C. §§ 1251-1387. This guidance will refer to provisions of the current act by relevant “CWA section.” 2

 531 U.S. 159 (2001). 

3 Carabell v. U.S. Army Corps of Eng’rs, 391 F.3d 704 (6th Cir. 2004); United States v. Rapanos, 376 F.3d 629 (6th
 

Cir. 2004). After certiorari was granted, these cases were consolidated, and the resulting opinion cited as Rapanos v. 

United States, 547 U.S. 715 (2006). 4

 CWA section 101(a). 

5

 While 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 C.F.R. 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 Fed. Reg. 47,042 (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. D.C. 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). 

6

 For example, the CWA section 402 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. 

7 33 C.F.R. § 328.3(a)(8); 40 C.F.R. § 230.3(s); 40 C.F.R. § 122.2 (“waters of the U.S.”).
 8

 CWA section 404(f); 40 C.F.R. § 232.3; 33 C.F.R. § 323.4. 9

 CWA section 402(l)(1) ("The Administrator shall not require a permit under this section for discharges composed 

entirely of return flows from irrigated agriculture. . . .”); CWA section 502(14)("[The] term [point source] does not
 

include agricultural stormwater discharges and return flows from irrigated agriculture."); 40 C.F.R. § 122.3(f)
 

(return flows from irrigated agriculture are excluded from the NPDES program); 40 C.F.R. § 122.2 (The term "point
 

source" "does not include return flows from irrigated agriculture or agricultural storm water runoff."). 10 See, e.g., 33 C.F.R. § 328.3(a)(1); 40 C.F.R. § 230.3(s)(1); 40 C.F.R. § 122.2 (“waters of the U.S.”(a)); 40 C.F.R.
 

§ 110.1 (“navigable waters” (a)).

11 Rivers and Harbors Appropriation Act of 1899, § 10, 33 U.S.C. § 403.
 12 See, e.g., 33 C.F.R. § 328.3(a)(2); 40 C.F.R. § 230.3(s)(2); 40 C.F.R. § 122.2 (“waters of the U.S.”(b)), 40 C.F.R.
 

§110.1 (“navigable waters” (b)).

13 Water Pollution Control Act of 1948, § 10(e), 62 Stat. 1155, 1161. 

14 Field staff generally should use the Strahler method. In Strahler’s method, a first-order stream has no tributaries,
 

a second-order stream is formed by the joining of any two first-order streams, and a third order stream is formed by 

the junction of any two second-order streams. Arthur N. Strahler, "Quantitative Analysis of Watershed 

Geomorphology," American Geophysical Union Transactions 38 (1957): 913-920. 15 33 C.F.R. § 328.3(a)(5); 40 C.F.R. § 230.3(s)(5); 40 C.F.R. § 122.2 (“waters of the U.S.”(e)).
 16 33 C.F.R. § 328.3(a)(7); 40 C.F.R. § 230.3(s)(7); 40 C.F.R. § 122.2 (“waters of the U.S.”(e)).
 17 547 U.S. at 759. 

34
 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

18 James M. Omernik, “The Misuse of Hydrologic Unit Maps for Extrapolation, Reporting and Ecosystem 

Management,” Journal of the American Water Resources Association 39.3 (2003): 563-73. 

19 The country is divided and subdivided into successively smaller watersheds, and the U.S. Geological Survey has 

developed a standardized watershed classification system--the Hydrologic Unit System--to organize watershed 

boundaries in a nested hierarchy by size. A unique hydrologic unit code (HUC) consisting of two to twelve digits 

(based on the level of classification) identifies each watershed in the country. The system divides the country into 21 

regions, and progressively smaller sub-regions, accounting units, cataloging units, watersheds, and sub-watersheds, 

with the Natural Resources Conservation Service delineating the boundaries for the smallest two levels. The 10-digit 

HUC, for instance, is the "watershed" level in the classification system. See United States, Department of 

Agriculture, Natural Resources Conservation Service, "Overview and History of Hydrologic Units and the 

Watershed Boundary Dataset," Natural Resource Conservation Service. Web. 25 Jan. 2011.; United States, United 

States Geological Survey, USGS Water-Supply Paper 2294, Hydrologic Unit Maps (Washington, D.C.: U.S. 

Government Printing Office, Paul R. Seaber, F. Paul Kapinos, and George L. Knapp, 1987). 20 33 C.F.R. § 328.3(e). 

21 Luna B. Leopold, M. Gordon Wolman, and John P. Miller, Fluvial Processes in Geomorphology (San Francisco: 

W.H. Freeman and Company, 1964). 22 Nyle C. Brady and Ray R. Weil, The Nature and Properties of Soils, 13th Edition (Upper Saddle River, NJ: 

Prentice Hall).

23 Luna B. Leopold, A View of the River (Cambridge: Harvard University Press, 1994) 3.
 24 United States, U.S. Environmental Protection Agency, EPA/600/R-06/126: Field Operations Manual for 

Assessing the Hydrologic Permanence and Ecological Condition of Headwater Streams (Washington D.C.: U.S. 

Environmental Protection Agency, Ken M. Fritz, Brent R. Johnson, and David M. Walters, 2006) 5.

25 See, e.g., 33 C.F.R. § 328.3(a)(2), (5); 40 C.F.R. § 230.3(s)(2)(5). 26 Richard B. Alexander, et al., “The Role of Headwater Streams in Downstream Water Quality,” Journal of the
 

American Water Resource Association 43.1 (2007): 41-59; Stephen R. Carpenter, et al., “Nonpoint Pollution of
 

Surface Waters with Phosphorous and Nitrogen,” Ecological Applications 8.3 (1998): 559-68; Dana W. Kolpin, et 

al., “Pharmaceuticals, Hormones and Other Organic Wastewater Contaminants in U.S. Streams: 1999-2000: A 

National Reconnaissance,” Environmental Science and Technology 36.6 (2002): 1202-1211.
 27 United States, U.S. Army Engineer Research and Development Center, Cold Regions Research and Engineering 

Laboratory, ERDC TR-04-1: Review of Ordinary High Water Mark Indicators for Delineating Arid Streams in the 

Southwestern United States (Hanover, NH: U.S. Army Engineer Research and Development Center, Robert W. 

Lichvar and James S. Wakeley, 2004). 

28 Generally, only the very large streams and rivers in the U.S. are monitored with stream gages for flow and the 

U.S. Geological Service maintains a network of only 7500 stream gages. United States, USGS, Fact Sheet 2009-

3020, National Stream Flow Information Program Implementation Status Report (March 2009). Smaller streams 

often do not have gages located on them, and not only would it be costly to monitor flow at sites like small 

headwater streams that are not currently gaged (Ken M. Fritz, Brent R. Johnson, and David M. Walters, "Physical
 

Indicators of Hydrologic Permanence in Forested Headwater Streams." Journal of the North American
 

Benthological Society 27.3 (2008): 690-704), monitoring studies can take one to two years (United States, U.S.
 

EPA, EPA 600/R-06/126, Field Operations Manual for Assessing the Hydrologic Permanence and Ecological
 

Condition of Headwater Streams (Cincinnati, Ohio: U.S. EPA Office of Research and Development, National 

Exposure Research Laboratory, Fritz et al., 2006)).
 29 Joan L. Florsheim, Jeffery F. Mount, and Anne Chin, “Bank Erosion as a Desirable Attribute of Rivers,” 

Bioscience 58 (2008): 519-29. 30 Takashi Gomi, Roy C. Sidle, and John S. Richardson, “Understanding Processes and Downstream Linkages of 

Headwater Systems,” BioScience 52 (2002): 905-16 (Gomi, et al.). 31 Louis A. Kaplan, Richard A. Larson, and Thomas L. Bott, “Patterns of Dissolved Organic Carbon in Transport,” 

Limnology and Oceanography 25 (1980): 1034-43; Robin L. Vannote, et al., “The River Continuum Concept,” 

Canadian Journal of Fisheries and Aquatic Sciences 37 (1980): 130-37; J. Bruce Wallace, Sue L. Eggert, Judith L. 

Meyer, and Jackson R. Webster, “Multiple Trophic Levels of a Stream Linked to Terrestrial Litter Inputs,” Science 

277 (1997): 102-04; Mark S. Wipfli and David P. Gregovich, “Export of Invertebrates and Detritus from Fishless 

Headwater Streams in Southeastern Alaska: Implications for Downstream Salmonid Production,” Freshwater
 

Biology 47.5 (2002): 957-69. 32 Id.
 33 547 U.S. at 779-80. 

35
 
 

 

 

 

 

 

34 Id. at 780. 35 33 CFR § 328.3(c); 40 CFR § 230.3(b). 36 Kevin J. Devito, Alan R. Hill, and Nigel Roulet, “Groundwater-Surface Water Interactions in Headwater Forested
 

Wetlands of the Canadian Shield,” Journal of Hydrology 181 (1996): 127-47; Michael A. O’Driscoll and Richard R. 

Parizek, “The Hydrologic Catchment Area of a Chain of Karst Wetlands in Central Pennsylvania, USA,” Wetlands
 

23 (2003): 171-79; Bradley J. Cook and F. Richard Hauer, “Effects of Hydrologic Connectivity on Water
 

Chemistry, Soils, and Vegetation Structure and Function in an Intermontane Depressional Wetland Landscape,”
 

Wetlands 27 (2007): 719-38. 37 Charles H. Wharton, Wiley M. Kitchens, and Timothy W. Sipe, The Ecology of Bottomland Hardwood Swamps 

of the Southeast: A Community Profile (Washington, D.C.: U.S. Fish and Wildlife Service, FWS/OBS-81/37, 1982)
 

9.
 38 As defined by the National Research Council, “riparian areas” are “transitional between terrestrial and aquatic
 

ecosystems and are distinguished by gradients in biophysical conditions, ecological processes, and biota. They are 

areas through which surface and subsurface hydrology connect waterbodies with their adjacent uplands. They 

include those portions of terrestrial ecosystems that significantly influence exchanges of energy and matter with
 

aquatic ecosystems (i.e., a zone of influence). Riparian areas are adjacent to perennial, intermittent, and ephemeral 

streams, lakes, and estuarine-marine shorelines.” United States, National Research Council, Riparian Areas:
 

Functions and Strategies for Management (Washington, D.C. : National Academy Press, 2002) 33. 

39 A “flood plain” is the relatively broad and smooth valley floor that is constructed by an active river and 

periodically covered with floodwater from that river during intervals of overbank flow. See also Theodore H.
 

Schmudde, “Floodplain,” The Encyclopedia of Geomorphology, ed. Rhodes W. Fairbridge (New York: Reinhold, 

1968) 359-62. 

40 William J. Mitsch and James G. Gosselink, “The Value of Wetlands: Importance of Scale and Landscape
 

Setting,” Ecological Economics 35.200 (2000): 25-33; Curtis J. Richardson, “Ecological Functions and Human
 

Values in Wetlands: A Framework for Assessing Forestry Impacts,” Wetlands 14.1 (1994): 1-9. 41 Arid West Water Quality Research Project, Habitat Characterization Study Final Report (Phoenix: URS 

Corporation, 2002); William J. Mitsch and James G. Gosselink, Wetlands, 4th ed. (Hoboken, NJ: John Wiley & 

Sons, Inc., 2007) 347. 

42 Robin L. Wellcomme, Fisheries Ecology of Floodplain Rivers (London: Longman, 1979); Virginia Carter, 

“Wetland Hydrology, Water Quality, and Associated Functions,” National Water Summary on Wetland Resources, 

eds. Judy D. Fretwell, John S. Williams, and Phillip J. Redman (Washington, D.C.: U.S. Department of the Interior, 

U.S. Geological Survey, USGS Water-Supply Paper 2425, 1996) 35-48; Alexander D. Huryn and K. Elizabeth 

Gibbs, “Riparian Sedge Meadows in Maine: A Macroinvertebrate Community Structured by River-Floodplain
 

Interaction,” Invertebrates in Freshwater Wetlands of North America: Ecology and Management, eds. Darold
 

Batzer, Russell B. Rader, and Scott A. Wissinger (New York: John Wiley & Sons, 1999), 363-82; Victor S.
 

Lamoureux and Dale M. Madison, “Overwintering Habitats of Radio-Implanted Green Frogs, Rana clamitans,” 

Journal of Herpetology 33 (1999): 430-35; Leonard A. Smock, “Riverine Floodplain Forests of the Southeastern
 

United States: Invertebrates in an Aquaticterrestrial Ecotone,” Invertebrates in Freshwater Wetlands of North 

America: Ecology and Management, eds. Darold Batzer, Russell B. Rader, and Scott A. Wissinger (New York: John
 

Wiley & Sons, 1999) 137-65; James H. Harding, Amphibians and Reptiles of the Great Lakes Region (Ann Arbor, 

MI: University of Michigan Press, 2000); Ted R. Sommer, Louise Conrad, Gavin O’Leary, Frederick Feyrer, and
 

William C. Harrell, “Spawning and Rearing of Splittail in a Model Floodplain Wetland,” Transactions of the 

American Fisheries Society 131 (2002): 966-74; Daniel D. Magoulick, and Robert M. Kobza,“The Role of Refugia 

for Fishes During Drought: A Review And Synthesis,” Freshwater Biology 48 (2003): 1186-98; Joseph L. Ebersole, 

et al., “Juvenile Coho Salmon Growth and Survival Across Stream Network Seasonal Habitats,” Transactions of the 

American Fisheries Society 135 (2006): 681-1697. 43 United States, U.S. Fish and Wildlife Service, Semipalmated Sandpiper Habitat Model (Washington, D.C.: U.S.
 

Fish and Wildlife Service, 2001). 

(<http://www.fws.gov/r5gomp/gom/habitatstudy/metadata/semipalmated_sandpiper_model.htm>.) 44 33 C.F.R. § 328.3(a)(3); 40 C.F.R. § 230.3(s)(3); see also 40 C.F.R. § 122.2 (“waters of the U.S.” (c)). 45 51 Fed. Reg. at 41,217; 53 Fed. Reg. at 20,765. 

46 33 C.F.R. § 328.3(b); 40 C,F.R. § 230.3(t), 40 C.F.R. § 122.2 (“waters of the U.S.” (b)). 47 547 U.S. at 782. 

48 Id. at 739. 

49 Id. at 742. 

36
 
 

 

 

 

 

 

 

50 United States v. Appalachian Elec. Power Co., 311 U.S. 377, 406 (1940). 51 FPL Energy Marine Hydro L.L.C. v. FERC, 287 F.3d at 1157 (internal quotation omitted). 52 Id. at 1157-59.
 53 Id. at 1157. 54 Alaska v. Ahtna, Inc., 891 F.2d 1401, 1405 (9th Cir. 1989). 55 Id. at 1404. 56 Id. at 1402-03.
 57 The term "waters of the United States" is defined by regulation to include "all interstate waters including interstate 

wetlands." 33 C.F.R. § 328.3(a)(2), (5); 40 C.F.R. § 230.3(s)(2)(5). 58 Id. at 779. 

59 Id. at 780.
 60 See, e.g., 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); James M. Omernik and Robert G. Bailey, “Distinguishing Between Watersheds and 

Ecoregions,” Journal of the American Water Resources Association 33.5 (1997): 939-40; David R. Montgomery, 

“Process Domains and the River Continuum,” Journal of the American Water Resources Association 35 (1999): 

397-410; Thomas C. Winter ,“The Concept of Hydrologic Landscapes,” Journal of the American Water Resources 

Association 37 (2001): 335-49; Jill S. Baron, et al., “Meeting Ecological and Societal Needs for Freshwater,”
 

Ecological Applications 12 (2002): 1247-60; J. David Allan, “Landscapes and Riverscapes: The Influence of Land
 

Use on Stream Ecosystems,” Annual Review of Ecology Evolution and Systematics 35 (2004): 257-84. 

 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.). 62 Peter E. Black, “Watershed Functions,” Journal of the American Water Resources Association 33.1 (1997): 1-11. 63 547 U.S. at 775, 779-80. 

64 Id. at 775. 65 Id. at 780. 66 547 U.S. at 739. 

67 Id. at 742. 68 Id. at 732-33 n.5 (alteration in original). 69 United States, U.S. Environmental Protection Agency, “Memorandum to Assert Jurisdiction for NWP-2007-945
 

(Marks Creek)” (Washington D.C.: U.S. Environmental Protection Agency, 23 January 2008). 70 United States, U.S. Army Engineer Research and Development Center, Cold Regions Research and Engineering 

Laboratory, ERDC TR-04-1: Review of Ordinary High Water Mark Indicators for Delineating Arid Streams in the 

Southwestern United States (Hanover, NH: U.S. Army Engineer Research and Development Center, Robert W. 

Lichvar and James S. Wakeley, 2004); Lisa L. Ely, “Response of Extreme Floods in the Southwestern United States 

to Climatic Variations in Holocene,” Geomorphology 19 (1997): 175-201. 71 Ian Reid and Lynne E. Frostick, “Channel Form, Flow and Sediments in Deserts,” Arid Zone Geomorphology:
 

Process, Form and Change in Drylands 2nd Edition, ed. David S.G. Thomas (Chichester, England: John Wiley & 

Sons, 1977) 205-29; William L. Graf, “Definition of Floodplains Along Arid-Region Rivers,” Flood 

Geomorphology, ed. Victor R. Baker, R. Craig Kochel, and Peter C. Patton (New York: Springer-Verlag, 1988) 231-

242.
 72 Levick, et al. 14-15. (See endnote 60.)
 73 “Memorandum to Assert Jurisdiction for NWP-2007-945 (Marks Creek).” (See endnote 69.) 74 N. Leroy Poff and James V. Ward, “Implications of Streamflow Variability and Predictability for Lotic 

Community Structure: a Regional Analysis of Streamflow Patterns,” Canadian Journal of Fisheries and Aquatic 

Science 46 (1989): 1805-18, 1809. 75 Matthew J. Czikowsky and David R. Fitzjarrald, “Evidence of Seasonal Changes in Evapotranspiration in Eastern 

U.S. Hydrological Records,” Journal of Hydrometeorology 5 (2004): 974-88. 76 547 U.S. at 770. 

77 Id. at 778-79. 78 Id. at 781. 79 Id.
 80 Id.
 

37
 
 81 42 Fed. Reg. 37,122, 37,128 (July 19, 1977). 

82 Id. at 37,123. 83 474 U.S. at 133 (quoting S.Rep.No. 414, 92d. Cong., 1st Sess., at 77 (1972)). 84 Gomi, et al.; Tracie L. Nadeau and Mark C. Rains, “Hydrological Connectivity Between Headwater Streams and 

Downstream Waters: How Science Can Inform Policy,” Journal of the American Resources Association 43 (2007): 

118-33.; Levick, et al. (See endnote 60.) 85 Martin Dieterich and Norman H. Anderson, “Dynamics of Abiotic Parameters, Solute Removal and Sediment 

Retention in Summer-Dry Headwater Stream of Western Oregon,” Hydrobiologia 379 (1998): 1-15; State of Ohio 

Environmental Protection Agency (2003a); S H. Duncan, R E. Bilby, J W. Ward, and J T. Heffner, "Transport of 

Road-Surface Sediment through Ephemeral Stream Channels," Water Resources Bulletin 23.1 (1987): 113-19. 86 Bruce J. Peterson, et al., “Control of Nitrogen Export from Watersheds by Headwater Streams,” Science 292 

(2001): 86-90; Judith.L. Meyer and J. Bruce Wallace, “Lost Linkages and Lotic Ecology: Rediscovering Small 

Streams,” Ecology: Achievement and Challenge, ed. Malcolm C. Press, Nancy J. Huntly, and Simon Levin 

(Orlando: Blackwell Science, 2001) 295- 317, 310; Ken J. Hall and Bruce C. Anderson, “The Toxicity and 

Chemical Composition of Urban Stormwater Runoff,” Canadian Journal of Civil Engineering 15 (1988): 98-106; 

David A. Lieb and Robert F. Carline, “Effects of Urban Runoff from a Detention Pond on Water Quality, 

Temperature and Caged Gammarus Minus (Say) (Amphipoda) in a Headwater Stream,” Hydrobiologia 441.1 

(2000): 107-16; Robert E. Pitt, “Receiving Water Impacts Associated with Urban Runoff,” Handbook of 

Ecotoxicology, eds. David J. Hoffman, Barnett A. Rattner, G. Allen Burton Jr., and John Cairns Jr. (Boca Raton, FL: 

CRC Press, 2002); Richard B. Alexander, Richard A. Smith, Gregory E. Schwarz, “Effect of Stream Channel Size 

on the Delivery of Nitrogen to the Gulf of Mexico,” Nature 403 (2000): 758-61. 87 State of Ohio Environmental Protection Agency (2003a); United States, State of Ohio Environmental Protection 

Agency, Nonpoint Source Impacts on Primary Headwater Streams (Columbus, OH: Ohio Environmental Protection 

Agency, 2003) (identified as 2003b) 

[<http://www.epa.state.oh.us/portals/35/wqs/headwaters/HWH_nonpoint_jan2003.pdf >]; Wipfli and Gregovich; 

Winsor H. Lowe and Gene E. Likens, “Moving Headwater Streams to the Head of the Class,” BioScience 55 

(2005):196-97; Mary C. Freeman, Catherine M. Pringle, and C. Rhett Jackson, “Hydrologic Connectivity and the 

Contribution of Stream Headwaters to Ecological Integrity at Regional Scales,” Journal of the American Water 

Resources Association 43.1 (2007): 5-14. (See endnote 31). 88 United States, National Research Council, Committee on the U.S. Geological Survey, Watershed Research in the 

U.S. Geological Survey (Washington, D.C.: National Academy Press, 1997) 4; Frank M. Dunnivant and Elliot 

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).
 89 Judith L Meyer, et al., "The Contribution of Headwater Streams to Biodiversity in River Networks," Journal of
 

the American Water Resources Association 43.1 (2007): 86-103.
 90 Gomi, et al.911. (See endnote 30.) 

91 Kaplan. et al.; Vannote, et al.; Wallace, et al.; Wipfli and Gregovich. (See endnote 31.)
 92 State of Ohio Environmental Protection Agency (2003a); State of Ohio Environmental Protection Agency (2001);
 

Levick, et al.. (See endnote 31.) 

93 547 U.S. at 747. 

94 Id. at 779-80. 

95 Id. at 780
 96 Id. at 783. 97 Id. at 785. 

98 Id. at 784. 99 Id. at 784-85. 100 Id. at 786. 101 531 U.S. at 167. 102 547 U.S. at 759. 103 See, e.g., Ralph W. Tiner, “Geographically Isolated Wetlands of the United States,” Wetlands 23.3(2003): 494-

516; Dennis F. Whigham and Thomas E. Jordan, “Isolated Wetlands and Water Quality,” Wetlands 23.3 (2003): 

541-49; Charles R. Goldman and Alexander J. Horne, Limnology (New York: McGraw-Hill, Inc., 1983); Paul H.
 

Zedler, “Vernal Pools and the Concept of ‘Isolated Wetlands,’” Wetlands 23.3 (2003): 597-607; Ellen T. Bauder, 

Andrew J. Bohonak, Barry Hecht, Marie A. Simovich, David Shaw, David G. Jenkins, and Mark Rains, A Draft 

Regional Guidebook for Applying the Hydrogeomorphic Approach to Assessing Wetland Functions of Vernal Pool
 

38
 
 Depressional Wetlands in Southern California (SanDiego, CA: San Diego State University, 2009).
 104 547 U.S. at 786. 

39