UNITED STATES ENVIRONMENTAL PROTECTION AGENCY

 WASHINGTON D.C. 20460

OFFICE OF THE ADMINISTRATOR

SCIENCE ADVISORY BOARD

September 2, 2014

MEMORANDUM

FROM: Dr. Amanda D. Rodewald, Chair /Signed/

Science Advisory Board (SAB) Panel for the Review of the EPA Water Body 

Connectivity Report 

TO: Dr. David Allen, Chair

EPA Science Advisory Board

SUBJECT: Comments to the chartered SAB on the Adequacy of the Scientific and Technical Basis 

of the Proposed Rule Titled “Definition of ‘Waters of the United States’ Under the Clean 

Water Act.”

In your memorandum of June 25, 2014 you requested that members of the SAB Panel for the Review of 

the EPA Water Body Connectivity Report provide comments to the chartered SAB on the adequacy of 

the scientific and technical basis of the proposed rule titled “Definition of ‘Waters of the United States’ 

Under the Clean Water Act.” You indicated that comments from members of the Panel would inform a 

separate SAB letter to the Administrator, which the chartered SAB will prepare, regarding the adequacy 

of the scientific and technical basis of the proposed rule. 

In response to your request, the SAB Panel held public teleconferences on August 20th and 21st, 2014 to 

develop comments on the adequacy of the science supporting the proposed rule. Panel members 

provided comments in response to five questions focused on the scientific and technical basis of the 

following aspects of the proposed rule: 1) the definition of tributaries as Waters of the United States; 2) 

the definition of adjacent waters and wetlands as Waters of the United States; 3) the definition of other 

waters on a case-by-case basis as Waters of the United States; 4) other definitions and the exclusion of 

specified waters, and 5) other aspects of the proposed rule. Responses to these questions and other 

matters of concern were discussed during the Panel’s two public teleconferences. This memorandum 

summarizes the main points of discussion. The attached individual written comments from Panel 

members provide additional details.

Key Points Discussed in Response to the Questions Provided to the Panel 

Summary: Most Panel members commented that the available science supported the key points of the 

EPA’s proposed rule – namely that tributaries, adjacent waters, and adjacent wetlands should be 

considered Waters of the United States whereas “other waters” should not be categorically included. 

Rather, Panel members commented in general that “other waters” could be considered (a) on an 
individual case-by-case basis, (b) in aggregate for similarly-situated other waters, or (c) regionally 

jurisdictional for other groups of similarly situated waters (e.g., prairie potholes). The Panel members 

raised a number of concerns about the proposed definitions and offered suggestions to improve clarity 

and applicability. There also was concern that several broad exclusions (e.g., groundwater, ditches, 

gullies/rills/swales, and artificial lakes and ponds) were not supported by the available science. 

Question 1. The proposed rule has defined Waters of the U.S. under the jurisdiction of the Clean 

Water Act to mean all tributaries of a traditional navigable water, interstate water, the territorial 

seas, or impoundment. This definition is based on the conclusion that a significant nexus exists 

between tributaries (as defined in the proposed rule) and the traditional navigable waters, 

interstate waters, and the territorial seas into which they flow. Please comment on the adequacy of 

the scientific and technical basis of this proposed definition. 

Nearly all Panel members agreed that even though connectivity occurs along a gradient, there is 

nonetheless strong scientific evidence that tributaries, as a group, have strong influence on the physical, 

chemical, and biological integrity of downstream waters, and therefore the available science supports 

making all tributaries jurisdictional under the Clean Water Act. Two panelists objected to any inclusion 

of tributaries in the Waters of the U.S. by rule. They commented that connectivity occurs along a 

gradient and consequently necessitates case-by-case examination. 

Several panelists raised concerns about the definition of tributaries in the proposed rule. One important 

criticism was that, while the proposed rule states that “tributary” means a water physically characterized 

by the presence of a bed and banks and ordinary high water mark, not all tributaries have ordinary high 

water marks (OHWM). The absence of OHWM is relatively common in ephemeral streams within arid 

and semi-arid environments or low gradient landscapes. In these contexts, the flow of water is unlikely 

to cause OHWM. In addition, some types of tributaries, such as spring-fed streams, lack an obvious 

OHWM because their groundwater sources dominate the water budget, are temporally stable, and do not 

produce sufficient fluctuations in the hydrograph to generate an OHWM. For this reason, the panelists 

recommended that the presence of OHWM not be a required attribute of a tributary and suggested that 

the wording in the definition could be changed to “bed, bank, and other evidence of flow.”

Another concern expressed by panelists was that the definition of “tributary” in the proposed rule 

includes lentic systems (e.g., lakes, ponds, wetlands) as well as lotic (stream-type) systems. Because 

tributaries are not typically defined this way, there was concern that the definition in the proposed rule 

would generate confusion. Panel members discussed whether flow-through lentic systems should be 

defined as tributaries or as adjacent waters and wetlands. The latter option was favored by most 

panelists. 

Another topic of discussion was that the concept of a connectivity gradient should be introduced early in 

the preamble of the proposed rule, not solely in the section dealing with “other waters.” Panelists 

commented that the concept of a connectivity gradient applies to all waters, including tributaries and 

adjacent waters and wetlands, though most panelists agreed that certain types of water bodies typically 

fall at the higher end of the connectivity gradient.

Question 2. The proposed rule has defined Waters of the U.S. under the jurisdiction of the Clean 

Water Act to mean all waters, including wetlands, adjacent to a traditional navigable water, 

interstate water, the territorial seas, impoundment, or tributary. This definition is based on the 

conclusion that a significant nexus exists between adjacent water bodies (as defined in the 

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proposed rule) and traditional navigable waters, interstate waters, and the territorial seas. Please 

comment on the adequacy of the scientific and technical basis of this proposed definition.

There was widespread agreement among panelists that, although connectivity occurs along a gradient, 

adjacent waters and wetlands have a strong influence on the physical, chemical, and biological integrity 

of traditional navigable waters. Therefore, nearly all members of the Panel agreed that the available 

science supports the categorical determination in the proposed rule that adjacent waters and wetlands are 

jurisdictional under the Clean Water Act. Two members did not agree that the available science supports 

any categorical determination of jurisdiction by rule.

Concerns were raised by Panel members about the definition of adjacent waters and wetlands. The 

proposed rule defines the term “adjacent” to mean bordering, contiguous, or neighboring. Neighboring 

waters are defined to include those with a shallow subsurface hydrological connection or a confined 

surface hydrologic connection to a jurisdictional water. The main issues raised by panelists were that 

adjacent waters and wetlands should not be defined solely on the basis of: 1) geographical proximity / 

distance to jurisdictional waters, 2) surface or shallow subsurface water connections to jurisdictional 

waters, or 3) hydrologic connections to jurisdictional waters. First and foremost, the panel members 

agreed that any definition or determination of adjacency should be based on functional relationships, not 

distance. The relationship between distance and connectivity was seen as ambiguous, and panelists 

commented that it was not a good indicator of the degree of connectivity. Panelists also discussed the 

role of groundwater in connecting adjacent waters and wetlands to jurisdictional waters. Panel members 

commented that, while the proposed rule indicates that neighboring waters connected to jurisdictional 

waters through a shallow subsurface connection would be included in the Waters of the U.S., the science 

indicates that regional groundwater sources can strongly affect connectivity. In addition, Panel members 

commented that the importance of biological and chemical connectivity should be more thoroughly 

discussed in the preamble of the proposed rule because the scientific literature clearly shows that these 

kinds of connectivity are important. 

The Panel also discussed the role that the temporal component of connectivity should play in defining 

adjacent waters and wetlands. The proposed rule indicates that “neighboring” waters include those 

located within the riparian area or floodplain of a jurisdictional water. Panel members discussed whether 

there is a particular flood interval (e.g., 10-20 year) that would be useful in defining the floodplain. 

There was general agreement among panelists that use of best professional judgment is probably the 

most realistic and practical option in this regard. Panelists also commented that consideration of the 

temporal dimension of connectivity is particularly important in arid systems with intermittent and 

ephemeral waters. Finally, members recognized that the definition of adjacent waters and wetlands is 

critical because it will delineate where “other waters” begin. The Panel’s draft review of the EPA Draft 

Report, Connectivity of Streams and Wetlands to Downstream Waters: A Review and Synthesis of the 

Scientific Evidence, provides extensive text on issues related to delineation of floodplain waters and 

wetlands.

Question 3. The proposed rule has defined Waters of the U.S. under the jurisdiction of the Clean 

Water Act to mean, on a case-specific basis, other waters including wetlands, provided that those 

waters alone, or in combination with other similarly situated waters, including wetlands, located 

in the same region, have a significant nexus to a traditional navigable water, interstate water, or 

the territorial seas. Please comment on the adequacy of the scientific and technical basis of this 

proposed definition. 

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There was general agreement among panelists that, based on the available science, it is appropriate to 

define “other waters” as Waters of the U.S. on a case-by-case basis, either alone or in combination with 

similarly-situated waters in the same region. That said, panel members recognized that the scientific 

literature has clearly established that “other waters” can have very strong effects on downstream waters, 

particularly when considered in aggregate. 

Panel members discussed various aspects of case-by-case evaluation of the connectivity of “other 

waters.” Panelists agreed that “other waters” should not be identified by means of a listing process such 

as that previously used to identify “Type 3” wetlands. Rather, members commented that use of a 

flowpath approach (broadly considering hydrological, chemical, and biological flowpaths) was the most 

scientifically rigorous way to identify “other waters” and the extent to which they are similarly situated. 

In this regard, Panel members commented that explicit reference to the type of flowpath, and 

information indicating whether it is surface only, shallow subsurface, or includes all hydrologic 

connections, would be particularly useful. The descriptions in the preamble of the proposed rule of 

evidence of physical, hydrological, and biological connectivity would be more scientifically rigorous if 

they focused on the magnitude or impact of the connection instead of a presence/absence (binary) 

perspective. Several Panel members commented that it would be useful for the agency to consider the 

conceptual flowpath model developed in the SAB Connectivity Panel’s draft review of the EPA draft 

report, Connectivity of Streams and Wetlands to Downstream Waters: A Review and Synthesis of the 

Scientific Evidence. Panel members noted that Panel’s the review can provide useful guiding principles 

for decisions.

Many panelists commented that distance should not be the primary metric used to evaluate significance 

of connection of “other waters” to jurisdictional waters. Panelists commented that using distance in this 

way is inconsistent with the scientific understanding of how hydrological, geochemical, and biological 

processes affect connectivity. Members further commented that the determination of connection via 

shallow subsurface pathways must take into account topographic gradient and soil and aquifer hydraulic 

properties as well as distance separating water bodies. For example, some highly permeable 

soils/aquifers with high hydraulic conductivity and a strong topographic gradient can transport water and 

dissolved solutes over longer distances between upgradient and downgradient waters than lower 

permeability soils/aquifers. Panel members commented that, in order to evaluate the connectivity of 

“other waters,” it is important to understand hydrogeologic conditions and groundwater flow. In 

addition, panelists noted that it is important to consider the movement of biota (which varies temporally 

and by species), and the variability in water flows through shallow subsurface connections (due, for 

example, to the availability of water or the nature of the substrate).

Some panelists expressed concern about the use of the term “in the region” in the definition of other 

waters on a case-by-case basis as Waters of the U.S. Panel members noted that it could be problematic if 

“in the region” were to mean “in the watershed” because surface and ground-watershed units may not 

align. Panel members commented that a more scientifically justified approach would include surface and 

subsurface waters in watershed delineation. Members also commented that it would not be appropriate 

to use ecoregions to identify ”similarly situated” “other waters” because ecoregions were developed on 

the basis of terrestrial vegetation communities, in combination with soils and climate, and do not reflect 

hydrologic regions. Panel members commented that use of Hydrologic-Landscape Regions would be a 

good alternative approach for identifying similarly situated “other waters.” 

Panel members generally agreed that aggregating “similarly situated” waters is scientifically justified, 

given that the combined effects of these waters on downstream waters are often only measurable in 

aggregate. Panelists also were generally comfortable with the idea of using “similarly situated” waters to 

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guide aggregation. However, there was much discussion about the most scientifically justified method 

for aggregating waters. Panel members agreed that the available science supported aggregating waters 

based on functional attributes and flowpaths. 

In the preamble of the proposed rule, the EPA and the U.S. Army Corps of Engineers requested input on 

the following four options for determining which waters and wetlands are “similarly situated”: (1)

“Other waters” are similarly situated only in certain areas of the country (e.g. in certain ecoregions); (2) 

Certain subcategories of “other waters” as a class have a significant nexus; (3) No “other waters” are 

similarly situated and all “other waters” must be evaluated individually; and (4) All “other waters” in the 

watershed are similarly situated. Panel members generally expressed a preference for combining options 

1 and 2 so that both the geographic region and type of water would be considered. There was general 

agreement among Panel members that the rule should not prescribe methods for determining which 

waters are similarly situated given that these methods are constantly improving and changing. Rather, 

Panel members suggested developing a set of questions that must be addressed when determining 

whether “other waters” are similarly situated. Panel members commented that there are certain 

subcategories / types of other waters in certain regions/areas where there is sufficient scientific evidence 

to categorically determine that these types of waters are jurisdictional (e.g., prairie potholes, Carolina 

and Delmarva Bays, pocosins, Texas coastal prairie wetlands, western vernal pools). Members also 

commented that the science does not support a determination to exclude any groups of “other waters” 

(or subcategories thereof, e.g., Great Plains playa lakes) from jurisdictional status. 

Panel members commented that as the science continues to develop, other sets of wetlands may be 

identified as “similarly situated.” Panel members further noted that before such determinations are 

made, additional research will be required to establish degree of connectivity and analyze spatial and 

temporal variability and threshold levels of connectivity. This research will be a requisite step in further 

development of rules relative to the jurisdictional status of “additional other waters of the U.S.” In 

particular, research will be needed to determine whether categories of “other waters” are similarly 

situated, have a significant nexus, and are jurisdictional by rule, or whether as a class they do not have 

such a significant nexus and might not be jurisdictional. Vernal pools in the eastern and Midwestern 

U.S. are especially in need of this attention.

Question 4. The proposed rule defines other terms and excludes specified waters and features 

from the definition of Waters of the U.S. Please comment on the adequacy of the scientific and 

technical basis of the other definitions and exclusions.

Panel members commented on the following proposed definitions and exclusions of specified waters 

and features from the Waters of the U.S.

Definitions.

Tributary. Several Panel members raised concerns about the definition of tributaries. As previously 

mentioned, one criticism discussed by Panel members was that not all tributaries will have ordinary high 

water marks (OHWM). The absence of OHWM is relatively common in ephemeral streams within arid 

and semi-arid environments or low gradient landscapes. Some types of tributaries, such as spring-fed 

streams, lack an obvious OHWM because their groundwater sources dominate the water budget, are 

temporally stable, and do not produce sufficient fluctuations in the hydrograph to generate an OHWM. 

For this reason, some panelists recommended that the presence of OHWM not be a required attribute of 

a tributary, and suggested that the wording in the definition could be changed to “bed, bank, and other 

evidence of flow.” Others spoke of the need to allow for variation among regions (e.g., the arid west).

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Shallow subsurface connection. Panel members commented that the definition of shallow subsurface 

connection in the proposed rule is not clear. Members noted that the definition does not indicate how 

deep a “shallow” subsurface connection could be. The examples on p. 22208 in the preamble of the 

proposed rule imply that this definition includes only very shallow (in the soil) connections rather than 

deeper geologic (except in karst systems) connections. Some panel members noted that shallow 

unconfined aquifers provide hydrologic and chemical connections among many wetland types, often on 

reasonably short time scales (i.e., 1-20 years). Members commented that such connections are critical to 

the integrity of these wetlands and should be included in the definition of a shallow subsurface 

connection. Members commented that these types of shallow unconfined aquifers meet the criteria listed 

on p. 22208 in the preamble of the rule because they “exhibit a direct connection to the water found on 

the surface in wetlands and open waters.” Panel members noted, for example, that a sand dune aquifer 

connects emergent marshes on the Oregon coast to the Coos Bay estuary and the nearshore coastal zone 

via shallow groundwater flowpaths.

Adjacent waters. As previously mentioned, Panel members commented that adjacent waters should not 

be defined solely on the basis of: 1) geographical proximity (as suggested on p. 22209), or 2) a 

hydrologic connection. Members also commented that it should be acknowledged that the movement of 

biota establishes connectivity. 

Riparian area. Panel members commented that the definition of riparian area in the proposed rule is 

problematic because it is based on hydrologic flows and not the host of other functions that riparian 

areas provide. Likewise, Panel members commented that upland also needs to be defined, especially as 

related to ditches.

Significant and significant nexus. Panel members generally found that the term “significant nexus” 

was poorly defined in the proposed rule and that the use of the term “significant” was vague. Panel 

members commented that the little guidance was provided in the preamble of the rule to interpret these 

terms. There was agreement among Panel members that it was important to articulate in the proposed 

rule that (1) “significant nexus” is not a scientific term but rather legal term that requires a policy 

determination in light of the law and science and (2) the relative strength of downstream effects should 

inform the conclusions about the significance of those effects for purposes of interpreting the Clean 

Water Act. 

Exclusions. The proposed rule excludes certain waters from jurisdiction under the Clean Water Act. 

Panel members noted that many of the exclusions in the proposed rule do not have strong scientific 

justification and, rather, reflect policy decisions that account for stakeholder concerns and / or historical 

practices.

Groundwater and shallow subsurface connections. The proposed rule excludes groundwater, 

(including groundwater drained through subsurface drainage systems) from jurisdiction under the Clean 

Water Act. Panelists commented that the available science clearly shows that groundwater connections, 

particularly via shallow flowpaths in unconfined aquifers, are critical in supporting the hydrology and 

biogeochemical processes of wetlands and other waters and serve to connect waters and wetlands that 

have no apparent surface connections. Panel members commented that there is a vast scientific literature 

on the hyporheic zone on this topic. Indeed, in the arid and semi-arid lands, groundwater is the dominant 

source of flow to both tributaries and the main stem river segments. Panel members noted that in some 

volcanic and karst regions, springs and gaining streams are the dominant source of flow for both 

tributary and main stem river segments. For example, the middle section of the Snake River, including 

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the Twin Falls and Boise, Idaho region of the Snake River Plain Province, is mostly sustained by 

groundwater, and various sections of the Green River in Kentucky are sustained by groundwater in the 

Karst region near Mammoth Cave National Park. Vast sections of the Rio Grande River and its 

tributaries in southern Colorado through central New Mexico (Taos, Santa Fe, and Albuquerque) are 

sustained mostly by groundwater. 

EPA Office of Water staff explained that groundwater quality is not regulated under the Clean Water 

Act, but shallow subsurface waters can serve to establish connectivity between a water body and a 

Water of the U.S. Although this clarification was very useful, panelists commented that the preamble of 

the proposed rule did not provide a clear understanding of what are considered to be “shallow” 

subsurface connections. Panelists were also concerned that role of regional groundwater systems in 

establishing connectivity was not addressed by the proposed rule. Panelists commented that this is a 

problem because regional ground water flows commonly interact with the surface environment at sinks 

and springs. For example, the Floridan aquifer underlies all of Florida as well as portions of Mississippi, 

Alabama, Georgia, and South Carolina and commonly interacts with the surface environment through 

sinks, springs, and outcrops. Panelists commented that an understanding of regional ground water flow 

systems is critical to the understanding of four-dimensional hydrologic connectivity on both the local 

and regional scales. Understanding ground water flow in unique hydrogeologic settings, including the 

Floridan aquifer system (karst systems), the High Plains aquifer system (semi-arid systems), and the 

Snake River Plain and Rio Grande Rift aquifer systems (volcanic bedrock systems), is especially 

important.

Ditches. The proposed rule excludes from Clean Water Act jurisdiction ditches that are excavated 

wholly in uplands, drain only uplands, and have less than perennial flow. In addition, the proposed rule 

excludes ditches that are not tributaries. There was extensive discussion among panelists of the proposed 

exclusion of these ditches. Panelists generally agreed that many research needs must be addressed in 

order to discriminate between ditches that should be excluded and included. Panel members commented 

that using the criterion of “less-than-perennial” flow to exclude ditches may not be consistent with 

addressing nutrient and sediment loading that affects drinking water, beach use, fishing, and other uses. 

Panel members also commented that ditches are perennial, intermittent, or ephemeral water conveyors,

and that constructed ditches can change the hydrologic flow paths of local and subregional hydrologic 

systems. 

Panel members offered specific comments about the proposed exclusion of two types of ditches. 

Members commented that exclusion of “ditches that are excavated wholly in uplands, drain only 

uplands, and have less than perennial flow” may be problematic because many such ditches now drain 

areas that previously would have been identified as wetlands under the Cowardin classification system 

(e.g., in the Midwestern U.S.). Such ditches now drain uplands and may not experience perennial flow, 

but rather, may pond water without flow except under heavy precipitation events or during snowmelt, or 

may contain water and flow only during wet conditions. Because such ditches exist in heavily 

agricultural areas which are subject to runoff containing high concentrations of sediments, nutrients, and 

pesticides, these ditches may be important for certain ecosystem services such as attenuation of nonpoint 

source pollution. Panel members also expressed concern about the exclusion of ditches that are 

embedded in landscapes that were previously wetlands but, due to drainage, are now upland. Panelists 

suggested that historical evidence of the “upland” status of these ditches include historic reconstructions 

from surveyor’s notes. Panel members commented that this is critical in some areas because many 

headwaters have been either converted to or networked with ditches, as in the Midwest. 

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Panelists noted that the proposed rule would exclude from jurisdiction ditches that are excavated in 

uplands and drain uplands but presumably drain into jurisdictional waters. Members commented that it 

is therefore important to consider the ditch drainage flowpath. It was noted, for example, that the 

exclusion of “ditches that are excavated wholly in uplands, drain only uplands, and have less than 

perennial flow” might apply to much of northwestern Ohio, which is so flat that it is difficult to move 

water off the land. When ditches in this region do flow, they move water and much agricultural run-off 

to Lake Erie. This can result in harmful algal blooms and the loss of drinking water (e.g., as has 

occurred in Toledo and surrounding areas). Panelists commented that these ditches clearly have an effect 

on downstream water quality in the broad sense. 

Panel members also commented that, because of the relative ease with which tile drains can now be 

installed, ephemeral channels without a bed and bank could easily be eliminated from jurisdiction under 

the proposed rule. It was noted that when ephemeral channels within farm fields are tiled, these waters 

deliver nutrient and pesticide-laden waters directly to downstream waters and increase “flashy” flows by 

reducing infiltration potential. Increased flows increase erosion and, along with increased nutrients and 

pesticides, degrade water and habitat quality and biotic integrity of downstream waters.

Gullies, rills, and non-wetland swales. Panelists commented that although gullies, rills, and nonwetland swales are excluded from jurisdiction under the proposed rule, the preamble of the rule notes 

that these features are important conduits for moving water between jurisdictional waters, making them 

important forms of hydrological and other types of connectivity. The preamble indicates that gullies, 

rills, and non-wetland swales are important in “fill and spill” waters, where flows spill from other 

waters/wetlands through gullies to stream channels (for example). Panel members commented that it is 

not clear how or why gullies that link two jurisdictional waters can be excluded from jurisdiction. A 

Panel member suggested that gullies that have been allowed to become permanent and minimally 

ephemeral, such as those caused by over grazing of livestock, should be included in the Waters of the 

U.S. Such gullies are observed throughout the Western U.S. Some Panel members suggested that 

gullies, rills, and non-wetland swales be assessed along a gradient of connectivity on a case-specific 

basis to determine whether they should be jurisdictional until the science is available to make an 

appropriate determination for the respective class as a whole.

Artificial lakes and ponds. Panel members commented that, although excluded from jurisdiction under 

the proposed rule, artificial lakes or ponds, or reflection pools, created by excavation, diking, or 

construction may be directly connected to the Waters of the U.S. by shallow or deeper groundwater. 

Panel members commented that a “blanket” exemption should therefore not be provided for these 

features. It was suggested that each feature be evaluated for exclusion through a hydrologic system 

analysis. Members commented that exemptions for artificial lakes and ponds could invite multiple 

abuses to the rule, particularly when land ownership and land use are changed with time. 

Panel members commented that the manner in which decisions would be made about excluding other 

manmade features was not clearly explained in the preamble of the proposed rule. Members noted, for 

example, that it was not clear whether the proposed rule would exclude: artificial lakes and ponds that 

have connections to downstream waters, underground stormwater drainage, natural versus artificial 

swales, roadside ditches, stormwater quality basins, bioswales, detention basins, industrial water 

processing and/or treatment facilities, desalination brine storage basins, cooling systems, oil and gas 

tank basins, fish farms, and rice paddies. 

Question 5. If you have any other comments about the adequacy of the scientific and technical 

basis of the proposed rule, please provide them as well. 

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In their individual written comments Panel members provided statements about other aspects of the 

scientific and technical basis of the proposed rule. Please refer to these individual comments. 

Because the Panel was asked to provide comments to the chartered SAB and not consensus advice, we 

will not be providing a formal report. I hope this summary of the major points discussed and the 

attached comments from individual Panel members will be helpful to the chartered SAB as it develops 

advice to the agency on the adequacy of the scientific and technical basis of the proposed rule.

Attachment

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Individual comments from members of the SAB Panel for the Review of the EPA Water Body Connectivity Report. 

These comments do not represent consensus SAB advice or EPA policy.

Attachment

Individual Comments from Members of the SAB Panel for the Review of the EPA 

Water Body Connectivity Report on the Scientific and Technical Basis of the 

Proposed Rule Titled “Definition of ‘Waters of the United States’ Under the Clean 

Water Act”

September 2, 2014

Dr. Allison Aldous....................................................................................................................... 2

Dr. Genevieve Ali ........................................................................................................................... 6

Dr. David Allan ............................................................................................................................ 14

Dr. Lee Benda .............................................................................................................................. 15

Dr. Emily Bernhardt .................................................................................................................... 22

Dr. Robert Brooks........................................................................................................................ 23

Dr. Kurt Fausch........................................................................................................................... 24

Dr. Siobhan Fennessy.................................................................................................................. 29

Dr. Michael Gooseff..................................................................................................................... 32

Dr. Judson Harvey ....................................................................................................................... 35

Dr. Lucinda Johnson ................................................................................................................... 37

Dr. Michael Josselyn.................................................................................................................... 42

Dr. Latif Kalin.............................................................................................................................. 50

Dr. Kenneth Kolm ........................................................................................................................ 52

Dr. Judith Meyer.......................................................................................................................... 88

Dr. Mark Murphy......................................................................................................................... 89

Dr. Duncan Patten..................................................................................................................... 100

Dr. Mark Rains .......................................................................................................................... 103

Dr. Amanda Rodewald............................................................................................................... 108

Dr. Emma Rosi-Marshall .......................................................................................................... 112

Dr. Mazeika Sullivan ................................................................................................................. 116

Dr. Jennifer Tank ...................................................................................................................... 124

Dr. Maurice Valett ..................................................................................................................... 127

Page 1
Individual comments from members of the SAB Panel for the Review of the EPA Water Body Connectivity Report. 

These comments do not represent consensus SAB advice or EPA policy.

Dr. Allison Aldous

Responses to questions regarding the definition of “Waters of the United States” under the Clean Water Act.

Revised Aug 22, 2014

The definition of Waters of the United States by the EPA and ACOE bases a determination of a “significant 

nexus” on the physical, chemical, and biological processes that connect and link wetlands waters to each other. 

These key processes are integral to the functioning of aquatic ecosystems, and the Rule is, for the most part, 

grounded in ecological, hydrological, and other physical sciences. 

The agencies appropriately recognize that “significant nexus” is not a scientific term and that “there is a gradient 

in the relation of waters to each other” (p. 22193). This gradient in connectivity runs from a continuous and 

significant physical and ecological connection, to an infrequent and insignificant connection. Specific 

scientifically-grounded, objective methods must be put in place to draw the line between those waters having or 

not having a significant nexus to other jurisdictional waters. In some cases methods and/or criteria are proposed, 

and often the agencies seek feedback on these approaches, implying that technical guidance will be issued after 

the Rule is complete. Nevertheless, evaluating the technical accuracy of the definition is difficult in the absence of 

clear criteria. 

1. The proposed rule has defined Waters of the U.S. under the jurisdiction of the Clean Water Act to mean all 

tributaries of a traditional navigable water, interstate water, the territorial seas, or impoundment. This 

definition is based on the conclusion that a significant nexus exists between tributaries (as defined in the 

proposed rule) and the traditional navigable waters, interstate waters, and the territorial seas into which they 

flow. Please comment on the adequacy of the scientific and technical basis of this proposed definition. 

The agencies are correct that tributaries and their associated ecosystems significantly affect the chemical, 

physical, and biological integrity of downstream waters. 

Under this proposed definition, tributaries include (i) stream-type (lotic) tributaries which are identified using the 

indicators of a bed and banks and ordinary high water mark (OHWM), and which also contributes flow, either 

directly or indirectly to a jurisdictional water; and (ii) stillwater-type (lentic) tributaries which may lack a bed and 

banks or OHWM, as long as they contribute flow to a jurisdictional water. Thus even though the criteria of bed, 

banks, and OHWM are useful for defining lotic tributaries, the only criteria that a tributary must have under this 

definition is that it contributes flow to a jurisdictional water. 

The definition of the lentic-type tributary (contributing flow from wetlands, lakes, and ponds) is not the way in 

which tributaries are traditionally defined in the scientific literature. It also makes the definition of a tributary 

confusing because there might be stream-type tributaries without one or more of the indicators (bed, bank, 

OHWM) but which could still be considered a tributary within the lentic-type. The lentic-type of freshwater 

ecosystems that often are connected to jurisdictional waters might be better included within the group of “adjacent 

waters,” as suggested on p. 22203.

The definition of the lotic-type tributary is appropriately comprehensive because it inherently includes ephemeral 

and intermittent streams (as well as perennial) streams. The former types are often overlooked but ecologically 

important, particularly in arid landscapes with seasonal patterns of precipitation. However, there may be some 

types of tributaries that lack an obvious OHWM, for example ephemeral streams in arid locations. Therefore the 

definition should be “bed and bank, and sometimes an OHWM”.

Aldous Comments Page 2
Individual comments from members of the SAB Panel for the Review of the EPA Water Body Connectivity Report. 

These comments do not represent consensus SAB advice or EPA policy.

2. The proposed rule has defined Waters of the U.S. under the jurisdiction of the Clean Water Act to mean all 

waters, including wetlands, adjacent to a traditional navigable water, interstate water, the territorial seas, 

impoundment, or tributary. This definition is based on the conclusion that a significant nexus exists between 

adjacent water bodies (as defined in the proposed rule) and traditional navigable waters, interstate waters, and 

the territorial seas. Please comment on the adequacy of the scientific and technical basis of this proposed 

definition. 

The agencies are correct that adjacent water bodies significantly affect the chemical, physical, and biological 

integrity of downstream waters. 

One problem with the way that ‘adjacents waters’ are defined is that groundwater is not adequately recognized as 

providing a connection (nexus) among water bodies. Groundwater flowpaths can be in the shallow subsurface, 

where flow is limited to the soil, and where water flows from one water body to another in hours to weeks. At the 

other end of the scale, groundwater can flow through deep bedrock deposits with travel times in the order of 

decades to centuries. In the proposed rule, only the shortest shallow flowpaths are recognized as providing a 

significant nexus among water bodies. The definition of a “shallow subsurface connection” is not entirely clear, 

but through the examples listed on p. 22208, it appears to be very shallow (i.e., in the soils) rather than within the 

surficial geology (except in karst systems).

Drawing the line at only the shortest shallow subsurface flowpaths is not supported by the science. Aquifers 

(particularly surficial unconfined ones) may provide hydrologic and chemical connections among wetland types, 

often on reasonably short time scales (i.e., 1-20 years) and so can meet the criteria listed on p. 22208 in that they 

“exhibit a direct connection to the water found on the surface in wetlands and open waters”. Examples include 

glacial till and sand deposits. For example, a sand dune aquifer connects emergent marshes on the Oregon coast to 

the Coos Bay estuary and the nearshore coastal zone via shallow groundwater flowpaths (Jones 1992).

The agencies suggest distance as a metric to determine if a shallow subsurface connection significantly connects a 

water body to a jurisdictional water (p. 22207). However, some highly permeable soils / aquifers with high 

hydraulic conductivity and a strong topographic gradient can transport water and dissolved solutes over longer 

distances between upgradient and downgradient waters. Effects on the downgradient (jurisdictional) waters 

include, for example, a more prolonged and muted hydrograph and transport of dissolved compounds. In contrast, 

lower permeability soils/aquifers with low k in flatter landscapes will have a lesser effect over shorter distances. 

Therefore the determination of connection via shallow subsuface pathways must take into account gradient and 

soil and aquifer hydraulic properties as well as distance separating water bodies. 

3. The proposed rule has defined Waters of the U.S. under the jurisdiction of the Clean Water Act to mean, on 

a case-specific basis, other waters including wetlands, provided that those waters alone, or in combination with 

other similarly situated waters, including wetlands, located in the same region, have a significant nexus to a 

traditional navigable water, interstate water, or the territorial seas. Please comment on the adequacy of the 

scientific and technical basis of this proposed definition. 

The agencies are correct that many types of water bodies that are not included as tributaries or adjacent waters 

may significantly affect the chemical, physical, and biological integrity of downstream waters. It is scientifically 

justified to aggregate similar waters for this analysis, for two reasons. First, wetlands within a region may be 

functionally similar in terms of their effects on downstream waters. For example, small pumice fens in the Upper 

Klamath Basin were found to have similar functions and relationships to downgradient perennial streams to 

warrant developing one hydrogeologic model representative of the entire group (Aldous and Bach 2014). Second, 

for some smaller wetlands, their effects on downstream waters are often only measurable in aggregate. 

The agencies ask a number of questions related to how a significant nexus analysis should be done. The method 

ultimately selected for aggregating waters geographically (i.e., “in the region”) and functionally (i.e., “similarly 

Aldous Comments Page 3
Individual comments from members of the SAB Panel for the Review of the EPA Water Body Connectivity Report. 

These comments do not represent consensus SAB advice or EPA policy.

situated”), and for making a significant nexus determination, must be based primarily on hydrologic principles, 

because hydrology is the key ecosystem driver for most other processes. This must include both surface 

hydrologic processes as well as subsurface (i.e., shallow groundwater) processes occurring with the soils and 

within any shallow unconfined aquifers that serve to connect surface water bodies to one another. The latter is 

often implied (e.g., p. 22214, bottom of 1st column) but not explicitly discussed.

Using the “single point of entry” watershed based on NHD watersheds appears to be an appropriate approach. 

However, the agencies suggest that for regions where there are few previously-defined jurisdictional waters that 

10-digit HUCs be used (p. 22212). If this is the case, some of those HUCs may not contain a jurisdictional water, 

and so how would a determination be made?

In proposing ways that “other waters” might be found to be “similarly situated”, the agencies suggest using the 

Omernik Level III ecoregions (p. 22215) or Hydrologic Landscape Regions (p. 22216) approaches for considering 

wetlands and waters to be similarly situated. Omernik ecoregions may not be appropriate because they are based 

largely on patterns of terrestrial vegetation. Other approaches to regional classification of freshwater ecosystems 

are also available, including TNC’s Ecological Drainage Units (Higgins 2003; Higgins et al. 2005) and WWF’s 

Freshwater Ecoregions (Abell et al. 2008). 

The approach ultimately taken should rely on a conceptual framework for wetland connectivity, such as the one 

described in the SAB final report. This framework described the pathways in 3 dimensions + time by which 

waters and wetlands are connected to one another. 

Given that the science is constantly evolving, it is preferable to have an adaptive process for making jurisdiction 

determinations, rather than a list of waters that are defined as jurisdictional (or not) from the outset. 

4. The proposed rule defines other terms and excludes specified waters and features from the definition of 

Waters of the U.S. Please comment on the adequacy of the scientific and technical basis of the other 

definitions and exclusions. 

As described above, groundwater connections, particularly via shallow flowpaths in unconfined aquifers, are 

critical in supporting the hydrology and biogeochemical processes of wetlands and other waters, and they serve to 

connect waters and wetlands when they have no apparent surface connections. This is recognized in part in the 

Rule, yet not to the extent that these flowpaths are integral to supporting Waters of the US. Furthermore, 

groundwater is on the list of excluded waters. More clarity is needed in how groundwater is considered in making 

a jurisdictional determination, and a more inclusive definition is required that incorporates more than just shallow 

subsurface flow in soils.

Even if groundwater is excluded as a Waters of the US, it is important to recognize that activities that occur on the 

surface above those subsurface flows, such as ground disturbance (e.g., logging, road construction), introduction 

of contaminants (e.g., oil spills, application of agricultural chemicals), or groundwater abstraction (e.g., pumping 

shallow wells) will significantly affect the integrity of the downstream receiving waters (Brown et al. 2011).

Prior converted cropland is excluded from the list of jurisdictional waters. Cropland that historically was wetland, 

and is being restored to wetland, should not be excluded from the list of jurisdictional waters. It is not clear if this 

is included or excluded. 

References:

Aldous, A.R. and L.B. Bach. 2014. Hydro-ecology of groundwater-dependent ecosystems: applying basic science 

to groundwater management, Hydrological Sciences Journal 59: 530-544.

Aldous Comments Page 4
Individual comments from members of the SAB Panel for the Review of the EPA Water Body Connectivity Report. 

These comments do not represent consensus SAB advice or EPA policy.

Brown, J. B., L. B. Bach, A. R. Aldous, A. Wyers and J. DeGagné. 2011. Groundwater-dependent ecosystems in 

Oregon: an assessment of their distribution and associated threats. Frontiers in Ecology and the Environment 9: 

97-102.

Higgins, J.V. 2003. Maintaining the ebbs and flows of the landscape – conservation planning for freshwater 

ecosystems. Pages 291-318 in Groves, C.R. Ed. Drafting a conservation blueprint: a practitioner’s guide to 

regional planning for biodiversity. Island Press, Washington, D.C.

Higgins, J. V., M. T. Bryer, M. L. Khoury and T. W. Fitzhugh. 2005. A Freshwater classification approach for 

biodiversity conservation planning. Conservation Biology 19: 432-445.

Jones, M.A. 1992. Groundwater availability from a dune-sand aquifer near Coos Bay and North Bend, Oregon. 

U.S. Geological Survey Open-File Report 90-563. Portland, Oregon. 

Aldous Comments Page 5
Individual comments from members of the SAB Panel for the Review of the EPA Water Body Connectivity Report. 

These comments do not represent consensus SAB advice or EPA policy.

Dr. Genevieve Ali

I would like to start by congratulating the EPA and the U.S. Army Corps of Engineers for putting the

draft rule up for discussion to the public as well as the scientific community. It is true that many

determinations of jurisdictional waters have been traditionally made on a case-specific basis rather than

using a predetermined framework for categorical (or automatic) determinations; the agencies’ efforts to

make the determination process more straightforward, consistent and transparent are therefore highly

commendable. My answers to the charge questions can be found below.

4. The proposed rule defines other terms and excludes specified waters and features from the

definition of Waters of the U.S. Please comment on the adequacy of the scientific and technical basis

of the other definitions and exclusions.

Here I chose to answer the fourth charge question first as it addresses the “definition of other terms”;

including that of “significant nexus”. The draft rule does include a definition for “significant nexus”;

however, I find it rather vague and subject to interpretation. Indeed, the EPA science report made a

very eloquent demonstration that connections exist between streams and wetlands, regardless of whether

they are at the head of a hydrographic network or not, and located in riparian and floodplain settings

or not. The science report also made a very strong case for the multiple nature of those connections

with biological, chemical, and hydrological exchanges, and with surface and subsurface components

in some cases. The SAB panel tasked with reviewing the science report went on to discuss that

connectivity expresses itself over a continuum or gradient and as such, it is reasonable to assume that

“all is connected” to a certain extent, although the magnitude, frequency and duration of the

connections are highly variable. The EPA science report did not, however, explicitly discuss the notion

of significance, and I find that the definition provided in the draft rule does not resolve the issue as it

equates “significant” with “significantly affects the chemical, physical, or biological integrity” of a

jurisdictional water, therefore never explaining what the root term “significant” means. The proposed

rule goes on to say that “for an effect to be significant, it must be more than speculative or

insubstantial”, but it does not put forward any threshold for deciding what is not speculative or

insubstantial. This definition of “significant nexus” is especially problematic when it comes to the

“other waters” and the case-specific analyses needed to determine jurisdiction. The proposed rule

would be more robust if the definition of “significant nexus” itself hinted at a tangible tool or

methodology to make the job of the Corps Districts more straightforward and transparent when it

comes to deciding what is not speculative or insubstantial.

I understand that the phrase “significant nexus” is a legal term and I appreciate the clarifications

provided by Dr. David Evans during the teleconference. I however persist that the proposed rule would

be stronger and less susceptible to contestation if the legal definition of “significant nexus” was paired

with a scientific definition of “significant nexus”, thus leading to a perfect translation between policy

and science. This would also serve the purpose of a more transparent determination process, which is

one of the goals pursued with the proposed rule. Although the Agencies made it clear that they did not

want to rely on specific flow rates, etc. to define the “significance” of a nexus, it would be important to

clarify the meaning of the word “significant” here. Is the significance of a nexus evaluated in terms of

the magnitude of connections, frequency, duration or all of the above? What about predictability? The

example of Prairie potholes and their significant nexus to downstream waters is an interesting puzzle

Ali Comments Page 6
Individual comments from members of the SAB Panel for the Review of the EPA Water Body Connectivity Report. 

These comments do not represent consensus SAB advice or EPA policy.

related to that question as some body of literature has argued that potholes might attenuate

“hydrological” floods but have no impact on so-called “economic” floods. In that literature,

“hydrological” floods are considered by high frequency, low to medium magnitude events that occur

commonly without economic damage while “economic” floods are low frequency, high magnitude

events that tend to cause economic damage. If relying on that literature and on the “significant nexus”

language contained in the proposed rule, I fear that it would fall on the local Agencies’ shoulders to

resolve the following questions/dilemma:

 Hydrological floods occur 4 out of 5 years but move relatively little water out of the potholes:

there is a frequent nexus but is it significant?

 Economic floods have a 1 in 100 or 1 in 500 years recurrence interval and have catastrophic

consequences downstream as water spills out of the potholes and reaches streams and rivers:

there is an infrequent nexus but it is quite strong; is it, then, significant?

Another question that comes to mind is: since the CWA concerns the chemical, physical and biological

integrity of (downstream) waters, do all three types of integrity need to be threatened simultaneously

for the nexus to be deemed significant, non-speculative or substantial? Besides, an additional element

of complexity (or uncertainty) has to do with whether the significance of a nexus should be measured

in terms of socioeconomic impact as well. Indeed, under the existing regulations, ‘‘other waters’’ can

be deemed jurisdictional if their use, degradation or destruction could affect interstate or foreign

commerce, thus hinting towards a possible social assessment of the significance as well. At one point in

the draft rule we can read that “a case-specific analysis allows for a determination of jurisdiction at the

point on the gradient in the relationship that constitutes a ‘‘significant nexus’’. I would be in favor of

more guidance being provided within the framework of the draft rule to facilitate that “critical point” or

“threshold” determination and there again make the process more transparent to the public.

While the connectivity-related literature does not use the term ‘‘significant’’, this term has

mathematical (or statistical) meanings and it would be important for the Agencies to assess whether

they can work with those meanings/definitions or not. For instance, the concept of “statistical

significance” is usually associated with a statistical test and rejecting a null hypothesis and would not

be of any use here. However, another interesting concept is that of “practical significance”, which

basically asks the question of whether the differences between two groups of data are big enough to

have a real meaning. I find that the concept of “practical significance” could be applied to the

“significant nexus” idea as the notion of significance here is relative, i.e., the word “significant” is used

to signify “with respect to” or “in comparison to” a system devoid of downstream connections. Each

category (by rule) of jurisdictional water (e.g., tributaries, adjacent waters) could be associated with a

very simple “Nexus Score” calculated as follows:

Nexus Score = ScoreChem + ScorePhys + ScoreBiol + ScoreComm (1)

The individual scores ScoreChem, ScorePhys, ScoreBiol and ScoreComm appearing in Equation (1) would have

been derived from a site-specific assessment done using the framework outlined in Table 1:

Ali Comments Page 7
Individual comments from members of the SAB Panel for the Review of the EPA Water Body Connectivity Report. 

These comments do not represent consensus SAB advice or EPA policy.

Table 1: Components of the Nexus Score for a given water

Does the

water...

If answer is

“No”

If answer is “Yes”

Frequency (freq)

of connection

Magnitude (mag)

of connection

Duration (dur)

of connection Total score

... affect the

chemical

(chem) integrity

of downstream

waters?

ScoreChem = 0

Low: zfreq = 1

Medium: zfreq = 2

High: zfreq = 3

Low: zmag = 1

Medium: zmag = 2

High: zmag = 3

Low: zdur = 1

Medium: zdur = 2

High: zdur = 3

ScoreChem =

zfreq + zmag +

zdur

... affect the

physical (phys)

integrity of

downstream

waters?

ScorePhys = 0

Low: zfreq = 1

Medium: zfreq = 2

High: zfreq = 3

Low: zmag = 1

Medium: zmag = 2

High: zmag = 3

Low: zdur = 1

Medium: zdur = 2

High: zdur = 3

ScorePhys =

zfreq + zmag +

zdur

... affect the

biological

(biol) integrity of

downstream

waters?

ScoreBiol = 0

Low: zfreq = 1

Medium: zfreq = 2

High: zfreq = 3

Low: zmag = 1

Medium: zmag = 2

High: zmag = 3

Low: zdur = 1

Medium: zdur = 2

High: zdur = 3

ScoreBiol =

zfreq + zmag +

zdur

... use,

degradation or

destruction

affect interstate

or foreign

commerce

(comm)?

ScoreComm = 0 ScoreComm = 3

In this framework, the maximum possible Nexus Score attainable by any water would be 30. The

Nexus Score equation (Equation (1)) could even be re-written by multiplying the different individual

scores by different weights:

Weighted Nexus Score = WChem × ScoreChem + WPhys × ScorePhys + WBiol × ScoreBiol + WComm × ScoreComm (2)

With WChem, WPhys, WBiol and WComm being user-defined weights between 0 and 1. Ideally, the weights

would need to make consensus either through public consultation or based on literature reviews. One

could foresee that if the assessment was done in a region where downstream populations are dependent on

water supply for drinking water, for example, the physical and chemical integrity scores could have a

higher weight than the biological integrity score.

A decision matrix like the one in Table 2 could then be used to assess an “other water” by comparing it to 

well-documented jurisdictional and non-jurisdictional waters:

Table 2: Practical significance of “other water” Nexus Score

Nexus score of the

well-documented

water

Nexus score of the

“other water” being

assessed

% difference between the

well-documented water

and “other water” Nexus

Scores

Tributary example 24

16

-33%

Adjacent water example 20 -20%

Non-jurisdictional water example 9 +78%

Ali Comments Page 8
Individual comments from members of the SAB Panel for the Review of the EPA Water Body Connectivity Report. 

These comments do not represent consensus SAB advice or EPA policy.

The tributary, adjacent water and non-jurisdictional water examples included in Table 2 would need to

be similarly situated (based on hydrologic landscape regions or ecoregions) as the “other water” being

evaluated. Then, by relying on “practical significance” principles, a significant nexus could be deemed

present if:

 The (unweighted) Nexus Score of the “other water” is more than 25% higher (for example) than

that of the similarly situated non-jurisdictional water; or

 The (unweighted) Nexus Score of the “other water” is equal or greater than that of any of the

similarly situated jurisdictional waters.

For regions that are very well documented, the Corps Districts could even forego the practical significance

assessment and just decide on a threshold (or critical) Nexus Score value (between 1 and

30) above which “significance” would be deemed present.

The (very coarse) idea of a Nexus Score (weighted or unweighted) builds upon the EPA science report

and the scientific literature stating that “all is connected” to a certain extent in watersheds. The (very

coarse there again) practical significance assessment outlined above however has the advantage of

showing how the nexus of an “other water” compares to that of jurisdictional and non-jurisdictional

waters before making a decision about its significance. I do not here suggest that the rule be re-written

to include methodological details similar to the ones outlined above because it is not the place to do it;

however the issue of “significance” being absolute versus relative should be addressed. This might

prevent the public from asking questions similar to the ones that panel members asked during the

teleconference, for example:

 Why do ditches need to have perennial flow to be jurisdictional even when they are located in

areas where most of the jurisdictional tributaries are less than perennial? It gives the impression

that the determination is made in absolute terms for ditches but in relative terms for tributaries

and suggests a lack of consistent framework.

 What is the best scientific framework for aggregation? If significance is assessed relative to

surroundings (rather than in absolute terms), then the concept of “similarly situated” becomes

more difficult to quantify given issues of process timescales and spatial scales and map scales.

Etc.

Still on the topic of definitions within the proposed rule, beyond the word “significant”, the term

“nexus” should be explained more clearly (i.e., what is a nexus, regardless of whether it is significant

or not?). From the proposed rule, it is sometimes unclear to me whether nexus = connection or nexus =

impact or influence? With the former definition, only connectivity is deemed important while with the

latter, both connectivity and isolation can have an impact on downstream waters. At one point in the

rule, we can read: “Connectivity for purposes of interpreting the scope of ‘‘waters of the United

States’’ under the CWA serves to demonstrate the ‘‘nexus’’ between upstream water bodies and the

downstream traditional navigable water, interstate water, or the territorial sea”: this statement strongly

downplays the beneficial effects of the isolation of some waters from downstream waters. There

again, the EPA science report made a great job in citing literature that shows that the isolation of certain

“other waters” can be critical to the health/integrity of downstream waters, and it might be important

to reiterate that fact by clarifying what a nexus is. The draft rule rightfully mentions that functions

Ali Comments Page 9
Individual comments from members of the SAB Panel for the Review of the EPA Water Body Connectivity Report. 

These comments do not represent consensus SAB advice or EPA policy.

that might demonstrate a significant nexus include sediment trapping, retention or attenuation of flood

waters, etc. and those functions all refer to isolation: those clarifications would however carry more 

power if they were closely associated with the definition of a “nexus” per se.

Lastly, about the definition of a wetland, it seems that the wording included in the draft rule is not

aligned with that of the EPA science report. Indeed, the draft rule mentions that wetlands are “areas

that are inundated or saturated by surface or groundwater at a frequency and duration sufficient to

support, and that under normal circumstances do support, a prevalence of vegetation typically adapted

for life in saturated soil conditions. Wetlands generally include swamps, marshes, bogs and similar

areas”. This slightly deviates from the science report which relied on the Cowardin definition and

required only one out of the three Cowardin criteria to select wetland-related literature. At the time of

the SAB panel discussions in Washington D.C., there were also multiple discussions regarding the use

of a broader Cowardin definition (only one out of three criteria) that was not aligned with the current

federal regulatory wetland definition (based on all three Cowardin criteria). The Agencies should

clarify how the new wetland definition agrees with (or contradicts) not only the current federal regulatory

definition but also the approach that was used in the science report that serves as a basis for the new rule.

1. The proposed rule has defined Waters of the U.S. under the jurisdiction of the Clean Water Act to

mean all tributaries of a traditional navigable water, interstate water, the territorial seas, or

impoundment. This definition is based on the conclusion that a significant nexus exists between

tributaries (as defined in the proposed rule) and the traditional navigable waters, interstate waters,

and the territorial seas into which they flow. Please comment on the adequacy of the scientific and

technical basis of this proposed definition.

Overall, I agree with all tributaries of a traditional navigable water, interstate water, the territorial seas

or impoundment being jurisdictional. The scientific literature reviewed in the EPA science report

supports the argument that tributaries, as a category, are involved in tremendous exchanges with

downstream waters and as such, they do not need to be subject to individual case-by-case evaluations

before they are deemed jurisdictional. Even though the current version of the EPA science report does

not address man-made/artificial waterways, I also agree with the identified features that could qualify

as jurisdictional ditches, namely natural streams that have been altered, ditches excavated in

jurisdictional waters, ditches that have perennial flow and ditches that connect jurisdictional waters.

In light of one of the objectives pursued with this new rule, i.e. a more consistent and transparent

determination of jurisdictional waters, I think that the inclusion of a regulatory definition of “tributary” is

great. However, I am not sure that the majority of the literature supports the categorization of run-ofstream wetlands and lakes as tributaries, especially since the majority of the literature defines tributaries

as longitudinal features that have directional flow. In the draft rule itself, it is somewhat confusing to

define a tributary as “a longitudinal surface feature that results from directional surface water movement

and sediment dynamics demonstrated by the presence of bed and banks, bottom and lateral boundaries,

or other indicators of OHWM” and still call run-of-river wetlands and lakes tributaries when they do not

fit that definition. The agencies did recognize that uncertainty and said they could rather categorize

wetlands that connect tributary segments as adjacent waters rather than tributaries: I favor that option.

Also, the EPA science report was well structured with 1) streams, 2) riparian and floodplain wetlands,

and 3) non-riparian and non-floodplain wetlands and I think that the proposed rule should build upon

that structure and consider, separately, 1) tributaries = streams, 2) adjacent waters in riparian and

Ali Comments Page 10
Individual comments from members of the SAB Panel for the Review of the EPA Water Body Connectivity Report. 

These comments do not represent consensus SAB advice or EPA policy.

floodplain areas, including run-of-river features, and 3) other waters in non-riparian and non-floodplain

areas.

2. The proposed rule has defined Waters of the U.S. under the jurisdiction of the Clean Water Act to

mean all waters, including wetlands, adjacent to a traditional navigable water, interstate water, the

territorial seas, impoundment, or tributary. This definition is based on the conclusion that a

significant nexus exists between adjacent water bodies (as defined in the proposed rule) and

traditional navigable waters, interstate waters, and the territorial seas. Please comment on the

adequacy of the scientific and technical basis of this proposed definition.

I support the change from ‘‘adjacent wetlands’’ to ‘‘adjacent waters’’ in the proposed rule because it is

more aligned with the contents of the EPA science report that the proposed rule relies on. By using a

broader Cowardin definition to select wetland-related literature, the science report in fact considered

multiple types of water bodies (e.g., oxbow lakes) located in riparian and floodplain settings. Equating

the term “neighbouring” with “being located in (the same) riparian or floodplain area” is also aligned

with the EPA science report.

I also agree with the statement that “for waters outside of the riparian area or floodplain, confined

surface hydrologic connections (as described above) are the only types of surface hydrologic

connections that satisfy the requirements for adjacency.” To me, this does not mean that waters outside

of the riparian area or floodplain and without confined surface hydrologic connections necessarily lack a

significant nexus but simply that they cannot be considered as adjacent waters and rather need to be

considered as “other waters” and be evaluated on a case-by-case basis.

The Agencies did request comments about how to deal with shallow subsurface flow connections when

determining adjacency. They considered four options, namely:

1. Asserting jurisdiction over adjacent waters only if they are located in the floodplain or riparian

zone of a jurisdictional water;

2. Considering only confined surface connections but not shallow subsurface connections for

purposes of determining adjacency;

3. Establishing specific geographic limits for using shallow subsurface or confined surface

hydrological connections as a basis for determining adjacency, including, for example, distance

limitations based on ratios compared to the bank-to-bank width of the water to which the water

is adjacent; or

4. Asserting jurisdiction over all waters connected through a shallow subsurface hydrologic

connection or confined surface hydrologic connection regardless of distance.

Option (1) is the one that the proposed rule currently puts forward, and I find that it is the most aligned

with the EPA science report. In my opinion, option (2) is too limiting and disregards the very large

body of literature demonstrating the importance of shallow subsurface flow paths, especially in riparian

and floodplain settings. Option (3) is a good idea but the ratios mentioned would likely be site-specific

Ali Comments Page 11
Individual comments from members of the SAB Panel for the Review of the EPA Water Body Connectivity Report. 

These comments do not represent consensus SAB advice or EPA policy.

and may be correlated to riparian and floodplain morphology, thus making option (1) a much easier and

straightforward one to implement. As for option (4), I find it to be the most impractical as it would be

difficult to test the presence of unbroken, perennial or intermittent shallow subsurface connections over

long distances.

3. The proposed rule has defined Waters of the U.S. under the jurisdiction of the Clean Water Act to

mean, on a case-specific basis, other waters including wetlands, provided that those waters alone, or

in combination with other similarly situated waters, including wetlands, located in the same region,

have a significant nexus to a traditional navigable water, interstate water, or the territorial seas.

Please comment on the adequacy of the scientific and technical basis of this proposed definition.

The approach put forward by the proposed rule, i.e. that waters not located in riparian and floodplain

settings be assessed on a case-by-case basis, is well aligned with the EPA science report: while the

presence of a nexus is not contested, the demonstration of its significance has to be made.

The draft rule mentions that the agencies “considered multiple approaches and options for how best to

address whether ‘‘other waters’’ were jurisdictional under the CWA”, including determining, “by rule,

that ‘‘other waters’’ are similarly situated in certain areas of the country”. I agree that ecoregions and

hydrologic landscape regions (HLRs) could be used for aggregation purposes. Those concepts are

widely used for research purposes and could become powerful regulatory tools by providing a scientific

equivalent to the phrase “similarly situated” that was used in previous court rulings and decisions.

Still in relation to “other waters”, the draft rule mentions that the agencies considered the possibility of

determining “by rule that certain additional subcategories of waters would be jurisdictional rather

than addressed with a case-specific analysis”. The draft rule builds on the examples of “waters such as

prairie potholes, Carolina and Delmarva bays, pocosins, Texas coastal prairie wetlands, and western

vernal pools” that could be deemed jurisdictional, as a category, while “playa lakes in the Great Plains,

even in combination with other playa lakes in a single point of entry watershed” would be considered

non jurisdictional for they lack a significant nexus. I am a bit reluctant about this option and do not

think that the currently available scientific literature supports that approach. The draft rule goes on to

say that “the [EPA science] Report indicates that there is evidence of very strong connections in some

subcategories that are not included as jurisdictional by rule” but there again, it is unclear to me

whether that very qualitative terminology (“very strong”) is a synonym for “significant”. Having other

groups or types of waters being determined jurisdictional by rule or category would only be possible if

we could rank them according to the frequency and/or magnitude and/or duration with which they

actively transfer materials (or prevent the transfer of materials) to downstream waters (see coarse

schematic in Figure 1).

Ali Comments Page 12
Individual comments from members of the SAB Panel for the Review of the EPA Water Body Connectivity Report. 

These comments do not represent consensus SAB advice or EPA policy.

Figure 1: Hypothesized/idealized ranking of other waters according to their nexus to downstream

waters

While reviewing the EPA science report, the SAB panel discussed – at length – the issue of

connectivity being a gradient rather than a dichotomous property, and the issue with “other waters” is

that they can be on both extremes of the spectrum (or gradient), i.e. be strongly connected or strongly

isolated from downstream waters depending on the prevailing conditions. This makes the assessment of

“significant nexus” particularly difficult and until (or unless) rankings or classifications similar to the

one hypothesized in Figure 1 are available, I do not think that it would be possible to determine that

certain additional subcategories of waters are jurisdictional by rule.

5. If you have any other comments about the adequacy of the scientific and technical basis of

the proposed rule, please provide them as well.

Just a quick comment about fill and spill hydrology: This is a detail which I do not believe has a major

impact on the legal implications of the proposed rule but I do not agree with the definition of “fill-andspill” that is used in the document. Indeed, the document reads that:

“For the purposes of [this] rule, ‘‘fill and spill’’ describes situations where wetlands or open waters

fill to capacity during intense precipitation events or high cumulative precipitation over time and then

spill to the downstream jurisdictional water.”

However most of the literature on fill-and-spill deals with subsurface flow connections over irregular

soil-bedrock interface or Prairie potholes and in such cases, the phrase “fill and spill” simply means

that water is going over the rim of the pothole or subsurface depression; it does not necessarily mean

that the water spilling over in fact discharges into a jurisdictional water. When modelling “fill and

spill”, most algorithms go with a four-phase sequence from dry  fill  spill  connect: the

“connect” phase corresponds to a spill large enough that it actually reaches a stream. It should be

clarified in the proposed rule that some spills occur very far from jurisdictional waters (i.e., in uplands)

and in fact never Reach or influence downstream waters.

Ali Comments Page 13
Individual comments from members of the SAB Panel for the Review of the EPA Water Body Connectivity Report. 

These comments do not represent consensus SAB advice or EPA policy.

Dr. David Allan

Statement of J. David Allan regarding EPA’s Proposed Rule “Definitions of “Waters of the United States’ Under 

the Clean Water Act”.

The Federal Register (vol 79 No. 76, April 21, 2014) reporting of the proposed rule and supporting science is 

excellent. It thoroughly covers the supporting science, and defines each of the elements of “significant nexus”. I 

believe the proposed rule and its supporting language define to the greatest degree possible which waters are 

jurisdictional under the CWA, and set forth the criteria by which “other waters” may be determined to be 

jurisdictional on a case by case basis. Yet to be resolved in whether broad categories of “other waters” may be 

considered jurisdictional as a category.

Those waters to be excluded deserve careful scrutiny as there is no recapture provision following this rulemaking. I wish to raise possible concerns regarding Exclusion b (3) and Exclusion b (5-vi).

Exclusion b (3) – “ditches that are excavated wholly in uplands, drain only uplands, and have less that perennial 

flow” – together, these three criteria may suffice, but the distinction between perennial and less-than-perennial 

flow may be a cause for concern. P 22203 states, “Under this exclusion, water that only stands or pools in a 

ditch is not considered perennial flow and therefore any such upland ditch would not be subject to regulation”. 

In parts of southeast Michigan, Ohio and Indiana, topography is very flat and ditches flow primarily during times 

of heavy rain. Some ditches are sufficiently deep that they will pond water until the receiving river stage drops 

enough for water to flow from the ditch to the river. Yet such ditches commonly receive from surrounding 

lands, and episodically deliver, significant nutrients to downstream waters. In the aggregate, they are the 

source/conduit for the majority of contaminants reaching downstream waters (“most of the materials found in 

rivers originate outside of them.” P 22247). Indeed, this situation describes much of the drainage into western 

Lake Erie, where harmful algal blooms due to excessive nutrient loading have caused beach closings, and in 

August 2014 a three-day ban on drinking water for some 400,000 of the residents in and near Toledo, OH. In 

short, using the criterion of “less-than-perennial” flow to exclude ditches may not be consistent with addressing 

nutrient and sediment loading that affects drinking water, beach use, fishing, and other uses.

Exclusion b (5-vi) – “Groundwater, including groundwater drained through subsurface drainage systems”. An 

important pathway for some nutrients and contaminants is via subsurface drainage systems to ditches that may 

not have perennial flow, but which may deliver much of the nonpoint runoff to downstream waters. Thus this 

exclusion is a concern, and should be recognized as such. 

The aggregate influence of these two exclusions can be estimated by models such as SWAT, which then might 

serve as a basis for determining when these exclusions have sufficient impact to be considered.

If the agencies prefer criteria related to flow regime rather than the delivery of non-point pollutants, they might 

consider aggregate flow during a 90-day window spanning the time of fertilizer application.

Allan Comments Page 14
Individual comments from members of the SAB Panel for the Review of the EPA Water Body Connectivity Report. 

These comments do not represent consensus SAB advice or EPA policy.

Dr. Lee Benda

Preliminary Written Comments on proposed new CWA rule.

August 18, 2014

Overall comment.

Overall, the EPA has written a very good comprehensive overview of the new CWA rule, including numerous 

explanatory details, that reflects the amount and care of the effort involved, including the scientific literature 

review (Report), the SAB’s review of that document, previous and existing rules and case law. In total, I would 

say that the proposed new CWA rule largely reflects the state of the science as articulated in the EPA 

Connectivity Report and as reviewed and enlarged in the SAB panel review. However, there are several areas in 

the proposed rule that could be strengthened.

In addition, it appears that the Connectivity Report that is cited in the proposed rule is the original one reviewed 

by SAB and not a revised version in response to SAB comments. Hence, some of the text in the rule regarding 

scientific evidence may change in subsequent rule versions.

Question 1. The proposed rule has defined Waters of the U.S. under the jurisdiction of the Clean Water Act to 

mean all tributaries of a traditional navigable water, interstate water, the territorial seas, or impoundment. This 

definition is based on the conclusion that a significant nexus exists between tributaries (as defined in the 

proposed rule) and the traditional navigable waters, interstate waters, and the territorial seas into which they 

flow. Please comment on the adequacy of the scientific and technical basis of this proposed definition.

A key element in the determination that all tributaries to all navigable rivers (including desert ephemeral 

headwater channels) have a significant nexus to larger downstream (navigable) waters is that they must be 

considered in aggregate, as a population (although the distinction between individual tributary effects and 

aggregate tributary effects in the science literature review, including in Appendix A, is vague). Although this 

aspect of channel networks was discussed and embraced by the SAB, even suggesting that EPA create a separate 

section covering this topic in their Connectivity Report, it appears that the aggregate concept (for wetlands 

specifically, but which EPA extends to tributaries and neighboring waters) also originates from Justice Kennedy’s 

Opinion in Rapanos, in that they (wetlands) are jurisdictional, if they “either alone or in combination with 

similarly situated wetlands in the region, significantly affect...navigable waters”. However, Justice Kennedy 

wrote that there needs to be “some measure of significance of the connection for downstream water quality”.

The proposed CWA rule uses various terms to describe the “in combination” aspect of the argument of 

significantly effecting (e.g., significant nexus), including ‘in combination’, ‘in aggregate’ , ‘cumulatively’ and ‘an 

integrated system’. However, the EPA proposed rule language (and the science argument behind it) could be 

strengthened by describing in more detail what is meant by the terms ‘aggregate’ and ‘in combination’ (e.g., 

what is the “measure of significance of the connection for downstream water quality” in the context of 

aggregate effects). In addition, the aggregate issue that covers both tributaries and neighboring waters may 

become a touchstone for future challenges or litigation regarding the proposed rule. For example, what 

proportion of headwater streams would need to be adversely impacted (or eliminated) to create a significant 

negative impact on larger streams and rivers? Or taken in a larger frame of reference, what is the “measure of 

Benda Comments Page 15
Individual comments from members of the SAB Panel for the Review of the EPA Water Body Connectivity Report. 

These comments do not represent consensus SAB advice or EPA policy.

significance” in regards to aggregation of tributary effects on the chemical, physical and biological integrity of 

the nation’s waters, downstream (navigable)? 

As we have seen in the public comments, some take issue with the concept that everything is connected to 

everything else, including in an aggregate sense, and that waters, including headwater tributaries, should be 

considered on an individual basis (e.g., such as desert ephemeral channels that are only activated once per 

decade or even at a lower frequency).

The EPA may consider this issue and thus could include more detail about the scientific basis of the “aggregate” 

concept and how it can be determined (briefly summarized from the Connectivity Report and the SAB review or 

even expanded upon). The aggregate function of smaller tributaries to the mainstem rivers in regards to water, 

sediment, organic material and nutrients is well established in the scientific literature, conceptually and 

quantitatively. However, calculating the effect of a single headwater tributary or water body on a larger 

downstream system (which may be negligible) or calculating a threshold regarding the number, or proportion, 

of impaired tributaries on the full functionality of a downstream system may lie outside of present science 

capabilities (although simulation modeling offers an avenue to address this issue).

I think it is fair to say, in stating the scientific basis for aggregate effects in the proposed rule, that there is a 

sound scientific basis that tributaries, in aggregate (including ephemeral, intermittent and perennial), lead to 

significant nexus and that it is not speculative nor insubstantial. However, given the stochastic and episodic 

nature of the connections between tributaries and larger (navigable) rivers, it is not currently feasible to 

estimate thresholds regarding the effect of various proportions of impaired/non impaired tributaries on 

conditions of downstream waters; thus, all tributaries fall under the jurisdiction of the waters of the United 

States. This argument would also be extended to neighboring waters (wetlands, ponds, oxbows) that occur in 

riparian areas and in floodplains. However, there should be some effort to articulate the strength of these 

connections (in aggregate) and how they are determined in the Scientific Evidence (Appendix A). In addition, 

some editing might be in order such as including “aggregation”, in addition to “connectivity” as one of the 

foundational concepts in hydrology and freshwater ecology.

The proposed rule states that “...the tributary connection may be traced using direct observation or US 

Geological Survey maps, aerial photography or other reliable remote sensing information...”. I would add to this 

“the use of digital elevation or terrain models (DEMs, DTMs) of the highest resolution available in conjunction 

with flow routing algorithms to generate synthetic river networks...”.

Question 2. The proposed rule has defined Waters of the U.S. under the jurisdiction of the Clean Water Act to 

mean all waters, including wetlands, adjacent to a traditional navigable water, interstate water, the territorial 

seas, impoundment, or tributary. This definition is based on the conclusion that a significant nexus exists 

between adjacent water bodies (as defined in the proposed rule) and traditional navigable waters, interstate 

waters, and the territorial seas. Please comment on the adequacy of the scientific and technical basis of this 

proposed definition.

The issue raised about aggregate effects, in the context of significant nexus, in Question #1 also applies to 

Question #2 regarding all waters adjacent to rivers and tributaries.

Benda Comments Page 16
Individual comments from members of the SAB Panel for the Review of the EPA Water Body Connectivity Report. 

These comments do not represent consensus SAB advice or EPA policy.

Regarding adjacent waters, the rule states “...the agencies will also assess the distance between the water body 

and the tributary in determining whether or not the water body is adjacent.” As the EPA indicates in the 

proposed rule, this issue is ambiguous and sets the stage for confusion and disagreement. There should be some 

measure of quantification (hydrologic connectivity) that is easily measured (in the field or using remote sensing) 

to reduce the ambiguity.

Question 3. The proposed rule has defined Waters of the U.S. under the jurisdiction of the Clean Water Act to 

mean, on a case-specific basis, other waters including wetlands, provided that those waters alone, or in 

combination with other similarly situated waters, including wetlands, located in the same region, have a 

significant nexus to a traditional navigable water, interstate water, or the territorial seas. Please comment on 

the adequacy of the scientific and technical basis of this proposed definition.

The proposed rule states “...where effects will be analyzed in combination, the agencies will aggregate these 

effects...”. This statement is unclear on its own and it raises the issues outlined in my comments in Question #1 

about aggregate effects. This same issue comes up again in the proposed rule “...the agencies would assess the 

combined effects of similarly situated “other waters” in the region on the chemical, physical and biological 

integrity...”.

The use of Level III ecoregions may be appropriate for their use in defining areas where “waters are similarly 

situated and aggregation could be used (Map A in docket). However, it might be prudent, unless a more 

comprehensive analysis is done, to not provide such lists. Rather, it might be best to provide the criteria upon 

which to consider “aggregation”. However, the issue of “aggregation could be used” raises the complexities 

outlined in responses to Question #1. For example, how exactly would “aggregation” be done (e.g., 

conceptually, qualitatively or quantitatively)?

The term “landscape unit” is used in the context of aggregate effects and relates to similar hydrologic features 

and processes, or proximity of features. The EPA could consider using another term, rather than ‘landscape unit’ 

that is somewhat ambiguous, and in keeping with the science, may use terms such as similar hydrologic or 

geomorphic feature having similar processes.

The proposed rule in several areas raises the issue of a “desktop” analysis, presumably using remote sensing and 

digital data (including DEMs). The rule language might be strengthened if more definition or examples were 

provided of what constitutes a ‘desktop analysis’.

Question 4. The proposed rule defines other terms and excludes specified waters and features from the definition 

of Waters of the U.S. Please comment on the adequacy of the scientific and technical basis of the other 

definitions and exclusions.

Overall, I think the addition of key definitions in the proposed rule is necessary and important. I agree with most 

definitions as written. However, there are a few that could use some editing.

“The term riparian area means an area bordering a water where surface or subsurface hydrology directly 

influence the ecological processes and plant and animal community structure in that area.” This definition could 

be tightened up by including “...where surface or subsurface hydrology directly related to channelized flow or 

the associated alluvial aquifer (including hyphoreic zone) directly influence...”.

Benda Comments Page 17
Individual comments from members of the SAB Panel for the Review of the EPA Water Body Connectivity Report. 

These comments do not represent consensus SAB advice or EPA policy.

“...wetlands, lakes and ponds are tributaries (even if they lack a bed and banks or ordinary high water mark...”. 

As EPA in the proposed rule later acknowledges, the definition of wetlands, lakes and ponds as tributaries (in the 

case where tributaries and other waters are contiguous or overlapping such as in headwaters) may be 

problematic. I concur, since tributaries in the scientific literature have a specific physical description as does 

wetlands and ponds. I would propose that such wetlands, lakes and ponds be named something else, such as 

“instream wetlands”, “instream ponds” etc., or some other naming convention that clearly classifies these 

features.

Riparian areas, as defined in the rule, could exclude those areas that strongly influence aquatic systems 

(regulated waters) through the flux of solar radiation, woody material and litterfall; the zone of influence is 

generally considered equivalent to the height of riparian vegetation, regardless of hydrological influences.

Regarding the definition of floodplains and how flood frequency (or other event frequency such as mudflows) 

can be used to delineate floodplains, one approach is to choose the process and frequency that dominantly 

controls the channel morphology in the area of interest. In lower gradient (<0.01) and larger channels, this might 

be the 2-year flood. In higher gradient channels with boulder beds, the channel forming flood recurrence 

interval may be on the order of 10-years or longer. In steeper headwaters prone to debris flows, the scour line 

associated with those events would define the zone of interest. This approach would be similar to what the EPA 

proposes, but would extend it to include event frequency - morphological dependency and non fluvial events 

that shape channels.

In the proposed rule there is discussion about the uppermost extent of channels or where a channel begins. The 

rule should include some discussion that in some landscapes (semi arid and even humid) that channel head

locations can be transient. Channel heads and thus the uppermost extent of channel networks can extend 

upwards (by gully erosion) post wildfire or during very large storms. During a hiatus of fire or storms, the upper 

extent of channels can be reduced. In this context, gullies = channels, by definition.

The proposed rule states “...absolutely no uplands located in riparian areas and floodplains can ever be waters of 

the United States...”. By definition, uplands cannot be floodplains. If I understand this wording correctly, 

floodplain landforms can encompass higher areas of land (uplands) that will never fall under the waters of the 

US rule. Perhaps, this distinction could be made clearer in the rule.

The use of the term “watershed” to inform spatial relationships between tributaries, adjacent waters and other 

waters and larger (navigable) rivers is appropriate. EPA indicates that this spatial scale will often be HUC 10 digit 

(5th field) and I would suggest that they provide an example of river place names and areas associated with this 

watershed scale. For example, HUC 5th field areas are on the order of 225 mi2 (40,000 – 250,000 acres) or 160 to 

1,000 km2

.

Benda Comments Page 18
Individual comments from members of the SAB Panel for the Review of the EPA Water Body Connectivity Report. 

These comments do not represent consensus SAB advice or EPA policy.

Dr. Emily Bernhardt

Comments on the adequacy of the scientific and technical basis of the proposed 

rule titled Definition of Waters of the United States Under the Clean Water Act (79FR 22188-

22274)

I want to begin my comments by complimenting the authors of this new rule on preparing a cogent, clear and well 

reasoned set of clarifications on the critically important policy issue of the definition of waters of the United 

States. I believe that this rule will, as intended, greatly simplify permit application and regulatory procedures for 

the administration of the CWA for tributaries and for floodplain and adjacent waters. The authors have done an 

excellent job laying out the need for and purpose of this new rule; detailing and explaining the changes in the rule; 

and providing a concise and well-cited summary of the scientific literature that underpins these new guidelines.

In regards to Question 1 – Definition of tributaries as Waters of the United States: I am very pleased to see that 

the policy language is now consistent with the best available science and simple common sense. Every tributary 

stream of a navigable water, whether it carries permanent or occasional flow, is now explicitly recognized as a 

water of the United States. It is well known that the materials delivered by headwaters provide essential energy 

and nutrient resources to the biota of downstream waters, and also that pollutants that enter tributaries must 

inevitably be transported downstream. Thus in order to protect the chemical and biological integrity of major 

rivers, it is essential to protect the chemical, physical and biological integrity of contributing tributaries and of any 

bodies of water (lakes, ponds, wetlands) that are connected within these tributary networks. This section of the 

rule was quite clear and unequivocal and is entirely consistent with the body of scientific literature in hydrology, 

aquatic ecology and aquatic chemistry. I appreciate that the rule explicitly recognizes that “manmade breaks” 

(bridges, dikes, dams) or extreme alterations of channels (e.g. piping, damming) do not alter the potential of that 

water conveyance to affect downstream waters and thus do not affect its jurisdictional status. As the rule states 

clearly and simply “The discharge of a pollutant into a tributary generally has the same effect downstream 

whether the tributary waterway is natural or manmade”.

Given this statement (and the obvious truth behind it), I am sorry to see that the rule maintains exceptions for 

nearly all agricultural ditches and makes no mention of stormwater pipes. These vast systems of engineered 

channels have been created for the express purpose of routing water as rapidly as possible off of the landscape or 

fertilized agricultural fields or urban impervious surfaces. Those stormwaters bring with them any sediments that 

can be eroded and any chemicals that can be washed from those landscape surfaces. These exclusions may be 

politically necessary, but they are scientifically unjustifiable as the negative effects of agricultural and urban 

runoff on the quality of our surface waters has been exhaustively demonstrated in the scientific literature (see 

section 3.3.6 of SAB report). 

In regards to Question 2 – Definition of adjacent waters and wetlands as waters of the United States: The 

newly worded rule places protections on all waters of the United States that are adjacent to (~ bordering, 

contiguous or neighboring) a navigable water or any of its tributaries. A critically important feature of this new 

wording is that any water within the riparian zone or floodplain of a stream or river is recognized as a water of the 

United States, even in the absence of a direct surface water connection. Since, by definition, water bodies situated 

within floodplains are engulfed by occasional floods, it is an important improvement to recognize that the water, 

biota and chemicals within these systems are at least episodically hydrologically connected to downstream waters. 

This argument could be further strengthened by explicitly acknowledging that water bodies alongside streams or 

river are quite likely to be connected to those systems through extensive subsurface hydrologic exchange. The 

authors should consider whether they can provide further guidance in how the term floodplain is to be defined. 

There are considerable differences in the scope of protection depending upon whether regulators consider a 1 year 

or 500 year flood return interval to delineate a floodplain. Being more explicit about how a floodplain should be 

defined would allow for more consistent application of the rule.

Bernhardt Comments Page 19
Individual comments from members of the SAB Panel for the Review of the EPA Water Body Connectivity Report. 

These comments do not represent consensus SAB advice or EPA policy.

That said, I remain concerned about the vagueness of the word “adjacency” as it is used in the rule. The way that 

this line is drawn is critically important in evaluating whether a water body is automatically protected as an 

adjacent/floodplain/riparian water or whether it requires further justification as an “other water”. The rule authors 

requested comment about how to define adjacency and specifically discount the idea of using the concept of flood 

risk maps. In our SAB comments on the guidance we specifically recommended discussion of using flood return 

intervals and flood predictions to underpin the concept of adjacency. While I understand that the rule must allow 

flexibility for the differences in climate and topography across U.S. regions, it seems that some discussion of the 

specific questions that must be answered within any region to delineate floodplains, riparian zones or neighboring 

waters should be more explicitly set forward. 

In regards to Question 3 – Definition of other waters on a case-by-case basis as waters of the United States:

Having clarified the status of all tributaries and all waters adjacent to tributaries as waters of the United States, the 

authors are left with the challenge of determining what water bodies outside of these categories must also be 

protected in order to maintain the physical, biological and chemical integrity of downstream waters. The rule 

acknowledges that as water bodies become more distant from tributaries and rivers, the extent of their 

connectivity also declines. It would be useful for the rule to also mention that the size of these water bodies 

matters as well, small water bodies far from any flowing water system are more isolated (both hydrologically and 

via transfers of biota) than are large water bodies that are closer. I appreciate that the rule makes a strong case for 

considering that the aggregate effect of many minimally connected water bodies may be critical for maintaining 

the biological, chemical and physical integrity of water bodies in one or both of the previous, clearcut categories 

of jurisdictional waters. Many watersheds have a large number of non-floodplain wetlands that are collectively 

responsible for the maintenance of baseflows; the attenuation of floods; the production of organic material that 

fuels downstream food webs; and the trapping or removal of sediments, nutrients and contaminants that would 

otherwise contribute to the degradation of downstream water quality. Although individually these wetlands may 

each have minimal connections to downstream waters, the cumulative impact of these diffuse connections is 

tremendously important to the maintenance of downstream biota and ecosystem integrity. Historically, the 

destruction of wetlands has caused serious declines in the water quality of U.S. waters and it is crucial that our 

CWA works to prevent similar degradation in the future. I found the list of criteria that could be used to assess 

whether an “other water” was connected to downstream waters was comprehensive, reasonable, and well 

articulated. I found the text of the rule in this section very close in spirit, substance and argument to SRB panel 

discussion and recommendations on this issue. 

Though I am highly supportive of the overarching conceptual approach in the language regarding “other 

waters” I have many concerns about the applicability of the rule in actual decision making. Since the rule 

is intended to reduce ambiguity, it seems very important that the document set forward a more explicit set 

of requirements (or perhaps questions) that must be met (answered) in order to determine whether an 

“other water” is sufficiently “connected” to a downstream water that CWA regulations ought to apply. 

There are modern methods for assessing connectivity (see individual panel comments for numerous 

suggestions). These methods are constantly improving and being developed, thus the rule should avoid 

proscribing specific methods that may become outdated. Instead the rule would be improved by more 

explicitly stating the questions that must be answered in order to establish sufficient proof of a significant 

nexus or of similar situation.

The EPA requested input on how to approach the classification of “other waters” within the context of the 

final rule and set forward 4 options. The SAB review is clearly most consistent with the option whereby 

Certain subcategories of “other waters” as a class can already be recognized as having a significant nexus

as a result of prior empirical research (e.g. prairie potholes, Carolina DelMarva bays). Outside of these 

“waters” that have been the subject of prior study there must be some mechanism whereby new 

information can be used to bring new categories of “other waters” under the CWA should they be found 

to have a “significant nexus” with downstream waters.

Bernhardt Comments Page 20
Individual comments from members of the SAB Panel for the Review of the EPA Water Body Connectivity Report. 

These comments do not represent consensus SAB advice or EPA policy.

The rule authors write on p. 22217, column 1, first full paragraph “If waters are categorized as nonjurisdictional because of a lack of science available today, the agencies request comment on how to best 

accommodate evolving science in the future that could indicate a significant nexus for these ‘‘other 

waters.’’ Specifically, the agencies request comment as to whether this should be done through 

subsequent rulemaking, or through some other approach, such as through a process established in this 

rulemaking. “

It would seem to be quite helpful to use the rule to establish the process by which new categories of 

“other waters” with “significant nexus” can be established. If the rule includes explicit requirements or 

questions by which to determine whether a water has a significant nexus, it must also have a clear set of 

guidelines/questions for determining whether two or more waters are sufficiently “similarly situated” to 

one another to allow them to be considered in the aggregate.

The use of the word “close” in the definition of “similarly situated” implies that physical distance (or 

geographic isolation) is the most important aspect of this determination. 

In the wording about “similarity” and “significant nexus” increased emphasis should be placed on 

functional similarity and functional connections. 

More attention could and should be devoted to the scale of the water bodies in question (their individual 

and aggregated volumes and area relative to the watershed or basin size).

Other Comments:

Throughout the rule text, I hope the authors will alter the language to be more compatible with the revised 

guidance document and the SAB comments on that document. In particular:

• Connectivity is 4-D (hydrologic, biological, chemical, temporal)

Although rule authors have been careful to describe connections beyond hydrologic ones in the preamble 

and in the review of the literature, the text of the rule too often loses sight of the multiple dimensions of 

connectivity. This was an issue that the SAB pointed out in the guidance document as well. Loose 

language on this topic is particularly problematic for the non-floodplain, non-riparian waters (see section 

3.7.2 of SAB report).

To remedy this the rule should scrupulously avoid confusing statements such as:

“Lack of connection does not necessarily translate to lack of impact; even when lacking connectivity, 

waters can still impact chemical, physical, and biological conditions downstream.” p. 22248 top of 2nd 

column

“Wetlands that lack surface connectivity in a particular season or year can, nonetheless, be highly 

connected in wetter seasons or years.” p. 22248, 2nd column

in each case, the authors clearly intend to make the point that an “other water” can have a significant 

nexus to a downstream water even without a surface water hydrologic connection or with only 

occasionally hydrologic connections but in both cases they implicitly support the idea that only surface 

water hydrologic connections matter. Text such as this must be modified to address 4-D connectivity.

Bernhardt Comments Page 21
Individual comments from members of the SAB Panel for the Review of the EPA Water Body Connectivity Report. 

These comments do not represent consensus SAB advice or EPA policy.

• The use of the new terms uni-direction and bi-directional to classify U.S. waters is confusing and 

overemphasizes surface water connectivity above any other connections. These terms should be avoided 

(see SAB comments section 3.5.2.).

Bernhardt Comments Page 22
Individual comments from members of the SAB Panel for the Review of the EPA Water Body Connectivity Report. 

These comments do not represent consensus SAB advice or EPA policy.

Dr. Robert Brooks

Brooks comments on proposed rule: Definitions of Waters of the United States ... 7-28-14

22193 (column 1)- bullet – All impoundments...

Does this apply only to human impoundments, or also those caused by beaver activities, 

substantial debris dams, and/or geological events, such as landslides or subsidences?

22193 (col. 2) – Use of the term gradient – is appropriate, and should be linked to our review of the 

science report diagram of gradients.

22193 (co. 3) – Groundwater is expressly excluded as a water. (Same as in rule itself: 

22251(col. 1) – In this section on vernal pools, there is emphasis given to Western vernal pools, with 

accompanying citations. Eastern vernal pools seem to get short shrift, so additional literature should be 

included for this type of water.

22263 Sec. 328.3 Definitions – (b)(5)(vi) – Groundwater...)

This seems ill-advised because of the likely connectivity of surface flows into features such as 

karst sinkholes, with a potential to contaminate groundwater aquifers used for human water supplies, 

plus the possibility of reconnections to surface water a reasonable distance away.

22263 – adjacent, riparian area, floodplain, tributary 

I concur with the definitions provided for the above terms. However, from 22199 (bottom column 

2), I recommend including the additional description ...“the term “adjacent” to includes waters located 

within the riparian area or floodplain of a water ...”. This clarifies that these waters are jurisdictional by 

definition without need of demonstrating a significant nexus.

General comment: Although burdensome, for consistency between the science report (and our 

committee’s recommendations) and the proposed rule, revisions to the science report should be 

substituted for the text of Appendix A. For example, this will remove confusing terms such as 

unidirectional and bidirectional wetlands, and provide updated literature, which provides further 

evidence of connectivity to downstream waters.

Brooks Comments Page 23
Individual comments from members of the SAB Panel for the Review of the EPA Water Body Connectivity Report. 

These comments do not represent consensus SAB advice or EPA policy.

Dr. Kurt Fausch

Revised Comments by Kurt D. Fausch on the proposed rule: 

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

I read the proposed rule published in the Federal Register, and focus my comments specifically on the 

portions that addressed tributaries to the Nation’s waters, and on how these affect biological integrity of 

downstream waters. These are my areas of particular expertise.

Background:

The purpose of this rulemaking is to clarify and simplify the determination of which waters “possess a 

significant nexus” to the navigable waters of the U.S., and are therefore under the jurisdiction of the 

Clean Water Act (CWA). ‘Significant nexus’ was further defined by Justice Kennedy as waters that 

either alone or in combination with similarly situated waters significantly affect the chemical, physical, 

or biological integrity of navigable waters that are downgradient and downstream.

The standard of significantly affecting biological integrity - In the context of the CWA, biological 

integrity was defined in the early 1980s as the ability to support and maintain “a balanced, integrated, 

adaptive community of organisms having a species composition, diversity, and functional organization 

comparable to that of natural habitat of the region” (Karr and Dudley 1981; see also Karr 1991, Karr and 

Chu 1999). 

Therefore, human actions that degrade or fragment habitat in tributaries, adjacent waters, and other 

waters and, in doing so, alter the species composition, diversity, and functional organization of the 

assemblages of aquatic and semi-aquatic biota in navigable waters under the jurisdiction of the CWA 

then meet the definition above of significantly affecting the biological integrity of the nation’s waters. 

Given unlimited time and funds, this would be the ultimate test of the biological integrity standard – that 

altering habitat in, or connections to, these tributaries, adjacent waters, or other waters, significantly 

affects the composition, diversity, or functional organization of biota in covered waters.

Question 1: The proposed rule has defined Waters of the U.S. under the jurisdiction of the Clean Water 

Act to mean all tributaries of a traditional navigable water, interstate water, the territorial seas, or 

impoundment. This definition is based on the conclusion that a significant nexus exists between 

tributaries (as defined in the proposed rule) and the traditional navigable waters, interstate waters, and 

the territorial seas into which they flow. Please comment on the adequacy of the scientific and technical 

basis of this proposed definition. 

Response: Overall, there is abundant scientific evidence published in the peer-reviewed literature, as 

reviewed in the EPA Connectivity Report1 that was evaluated by this SAB panel, to support the rule that 

tributaries as category of waters strongly influence the chemical, physical, and biological integrity of 

downstream waters. Although the SAB commented that connectivity can vary among streams, the 

consequences of this connectivity for the physical, chemical, and biological integrity of downstream 

waters are sufficiently strong that streams can be justifiably viewed as a category.

1 Connectivity of Streams and Wetlands to Downstream Waters: A Review and Synthesis of the Scientific Evidence

(EPA/600/R-11/098B, September 2013, External Review Draft)

Fausch Comments Page 24

 
Individual comments from members of the SAB Panel for the Review of the EPA Water Body Connectivity Report. 

These comments do not represent consensus SAB advice or EPA policy.

Much of the focus in the Connectivity report, the proposed rule, and comments on it by some reviewers 

was on the hydrological connections and their consequences for moving sediment, nutrients, and 

contaminants downstream. However, in their response to the EPA Connectivity Report, the SAB 

emphasized that effects on biological integrity can often be by organisms moving up-gradient into 

tributaries to use habitats that are critical to sustain their populations, perhaps only at certain times of 

year or when water flows.

Biological organisms are uniquely adapted via natural selection to use all habitable portions of 

waterways, including ones that are ephemeral, and may move against flow to do this. For example, 

larval fishes in intermittent and ephemeral streams of the Great Plains drift downstream from source 

areas and rear in off-channel backwaters that form only after rainstorms and later dry up (Falke et al. 

2010a, 2010b). Juveniles of economically-important Chinook and coho salmon in a short Oregon 

coastal river move laterally into tidal marshes to feed and grow during summer and into the tiny 

headwater tributaries of these marshes to rear during winter, even though these headwater tributaries 

then dry up during summer (Bottom et al. 2005; Jones et al. 2014). Diking of these tidal marshes before 

the 1960s virtually eliminated several life-history types of each species, and removing the dikes has 

since then restored them. These unique life-history types of salmon are likely critical to the resilience of 

these populations (Bottom et al. 2011). Indeed, Oregon coast coho salmon are listed as threatened under 

the Endangered Species Act. The key role of these very small and sometimes intermittent habitats in 

sustaining the biological integrity of downstream waters is one of many reasons that tributaries as a 

category should be “jurisdictional” waters.

Overall, I found that the rule was written clearly, and identified the specific conditions by which these 

tributaries affect the biological integrity of downstream streams and rivers. In Appendix A, I found that 

these connections were well supported by relevant examples from the primary scientific literature, 

although I would urge the EPA to consider the comments of the SAB panel on this report.

In summary, with regard to the information supporting the assertion that tributaries as a water body type 

are connected to downstream waters and significantly affect their physical, chemical, and biological 

integrity, the rule is clearly written and this assertion is well supported by the scientific literature.

Concerns by other reviewers about including tributaries as a class:

I found that I disagreed with several statements in the initial response by Dr. Josselyn

“The Draft Science Report cites a number of studies that focus on headwater streams, but usually within 

the third or fourth order, not the first or second that would be covered by the Proposed Rule definition.” 

“The Draft Science report found only two studies that included first order streams in their analysis.”

These statements in Dr. Josselyn’s response are not true, and I disagree with them. Many references in 

the report and the additional references cited by the panel include 1-2nd order streams (e.g., see review 

by Meyer and Wallace 2001, cited there). As panelist Dr. David Allan pointed out, most research on 

stream ecology on which much of the report is based has been done on small streams. Connectivity has 

been well studied and documented in these streams. I also disagree with the point made that effects on 

downstream systems are lowest and minimal from these small streams, because they must be considered 

in the aggregate as a cumulative effect. 

Fausch Comments Page 25
Individual comments from members of the SAB Panel for the Review of the EPA Water Body Connectivity Report. 

These comments do not represent consensus SAB advice or EPA policy.

I also disagreed with several statements in the initial response by Dr. Murphy:

“There is no better way of assessing the impact of a watershed connection than its potential to degrade

the water quality of receiving waters or violate water quality standards for those waters. Yet no

reference to either water quality standards or the science for setting them appears in the Proposed

Rule”

Although I agree that effects of tributaries on chemical and physical integrity are important, this 

statement ignores the potential for biological organisms to make connections that are often against the 

flow, and even overland (e.g., by amphibians), and hence connect tributaries to downstream 

jurisdictional waters in ways that significantly affect biological integrity.

“The scientific significance of these flowpaths is a function of the disturbance scale, which can

be measured in the frequency, duration, predictability, and magnitude of the disturbance. The

probability of such a disturbance having a scientifically significant disintegrative effect on a

downstream ecosystem creates the gradient of connectivity described in the SAB review, as currently

used by the ecological sciences.”

Here again, connections made by biological organisms may cause important effects on biological 

integrity that are outside of the realm of using disturbance ecology via flowpaths to understand 

“significant nexus” among waters. Many organisms go against the flow.

Additional comments: Several additional comments come to mind:

1. Converted croplands – Following on Dr. Aldous’s response, I was uncertain about the case 

where, for example, wetlands or ditches that would previously have been covered waters, before 

being converted to human use, are then restored. Do these then become covered waters (which 

would be a good thing)? If so, would this create a backlash so that private landowners would not 

want to restore them (which would be a bad thing)?

2. Ditches – As was pointed out during the SAB teleconference, many ditches in the West divert 

water from jurisdictional waters, and transport fish and other biota downstream to their terminus, 

often to their demise. However, in some regions substantial amounts of the water in the 

landscape are in these ditches, and the intermittent and permanent ones constitute much of the 

aquatic habitat. They also raise the groundwater in their vicinity, then causing other natural 

ephemeral channels nearby to flow and become spring streams (e.g., called seep ditches in 

southeastern Colorado). As a result of the drying of the original streams in the region by 

diversions or groundwater pumping for irrigation, these seep ditches are used in some cases for 

reintroducing fishes that are listed as threatened or endangered on state lists, such as the 

Arkansas darter (see Groce et al. 2011), because they are the best remaining aquatic habitat in the 

region. As a result of these complexities, I had difficulty determining whether I could agree to 

excluding ditches as a category, even with the definitions made.

Fausch Comments Page 26
Individual comments from members of the SAB Panel for the Review of the EPA Water Body Connectivity Report. 

These comments do not represent consensus SAB advice or EPA policy.

3. Defining the start of a tributary – It is clear that this definition will be difficult, as Dr. Mark 

Rains pointed out. Nevertheless, the inclusion of tributaries as a class is well supported, and I 

agree that the requirement of the Ordinary High Water Mark should be optional, because of the 

many cases of spring streams that lack them.

I hope these comments are useful to the standing SAB and the EPA in their efforts to clarify the rule. I 

commend the EPA on writing a clear and well-supported preamble and rule.

References:

Bottom DL, Jones KK, Cornwell TJ, Gray A, Simenstad CA. 2005. Patterns of Chinook salmon 

migration and residency in the Salmon River estuary (Oregon). Estuarine, Coastal, and Shelf 

Science 64:79–93.

Bottom DL, Jones KK, Simenstad CA, Smith CL. 2011. Reconnecting social and ecological resilience in 

salmon ecosystems. In Bottom DL, Jones KK, Simenstad CA, Smith CL, Cooper R, editors. 

Pathways to Resilience: Sustaining Salmon Ecosystems in a Changing World, 3–38. Oregon Sea 

Grant. Oregon State University, Corvallis.

Falke, J. A., K. R. Bestgen, and K. D. Fausch. 2010. Streamflow reductions and habitat drying affect 

growth, survival, and recruitment of brassy minnow across a Great Plains riverscape. 

Transactions of the American Fisheries Society 139:1566-1583.

Falke, J. A., K. D. Fausch, K. R. Bestgen, and L. L. Bailey. 2010. Spawning phenology and habitat use 

in a Great Plains, USA, stream fish assemblage: an occupancy estimation approach. Canadian 

Journal of Fisheries and Aquatic Sciences 67:1942-1956.

Groce, M. C., K. D. Fausch, and L. L. Bailey. 2012. Evaluating the success of Arkansas darter 

translocations in Colorado: an occupancy sampling approach. Transactions of the American 

Fisheries Society 141:825-840.

Karr, J. R. 1991. Biological integrity: a long-neglected aspect of water resource management. 

Ecological Applications 1:66-84.

Karr, J. R., and E. W. Chu. 1999. Restoring life in running waters. Island Press, Covelo, CA.

Karr, J. R., and D. R. Dudley. 1981. Ecological perspectives on water quality goals. Environmental 

Management 5:55-68.

Jones KK, Cornwell TJ, Bottom DL, Campbell LA, Stein S. 2014. The contribution of estuary-resident 

life histories to the return of adult Oncorhynchus kisutch. Journal of Fish Biology 85:52-80.

Fausch Comments Page 27
Individual comments from members of the SAB Panel for the Review of the EPA Water Body Connectivity Report. 

These comments do not represent consensus SAB advice or EPA policy.

Meyer, J.L., and J.B. Wallace. 2001. Lost linkages and lotic ecology: Rediscovering small streams. In: 

Ecology: Achievement and Challenge, eds. M.C. Press, N.J. Huntly, and S. Levin, 295-317. 

Blackwell Science, Oxford, UK.

Fausch Comments Page 28
Individual comments from members of the SAB Panel for the Review of the EPA Water Body Connectivity Report. 

These comments do not represent consensus SAB advice or EPA policy.

Dr. Siobhan Fennessy

Generally speaking I think the USEPA has done an excellent job in drafting the rule. It is based on sound science 

and will strengthen and clarify the regulatory scheme that protects the integrity of aquatic ecosystems. It is clearly 

written and its arguments cogently made. However, I was surprised about the release date of the draft rule, and to 

see that it does not reflect the many suggestions made by the SAB panel to strengthen the EPA Connectivity 

Report. While I understand the timing of the release is typical, it possibly weakens the value of the SAB process, 

which is designed to strengthen the scientific basis upon which the draft rule is based. I hope the draft rule can be 

modified to reflect the work of the SAB panel. A second, related issue is that the report does not use the 

connectivity gradient framework that was suggested by the SAB panel. Establishing the framework early in the 

draft rule would aid in the discussions about what constitutes a significant degree of connectivity, which could 

help define jurisdictional waters. 

Q1. The proposed rule has defined Waters of the U.S. under the jurisdiction of the Clean Water Act to mean all 

tributaries of a traditional navigable water, interstate water, the territorial seas, or impoundment. This 

definition is based on the conclusion that a significant nexus exists between tributaries (as defined in the 

proposed rule) and the traditional navigable waters, interstate waters, and the territorial seas into which they 

flow. Please comment on the adequacy of the scientific and technical basis of this proposed definition. 

I fully support this definition of tributaries as Waters of the U.S. in the draft rule. It is based on sound science (as 

reflected in the Connectivity and SAB Pane reports) and provides a clear and defensible policy acknowledging 

that tributaries, by definition, are connected to navigable waters. This recognizes their role in transporting 

sediment and organic matter, processing nutrients and other chemicals, and providing habitat whether or not flows 

are perennial. The Connectivity Report is used as a basis for this definition, where the draft rule states, “The 

Report concludes that the scientific literature clearly demonstrates that streams, regardless of their size or how 

frequently they flow, strongly influence how downstream waters function.” One concern is that the Connectivity 

Report (Report) and the draft rule use different definitions of “tributary;” this may create unnecessary confusion 

as the Report is relied upon as the scientific basis of the proposed rule. The Report defines a tributary simply as:

“a stream or river that flows into a higher-order stream or river,” 

while the definition in the draft rule is:

“The term tributary means a water physically characterized by the presence of a bed and banks and ordinary 

high water mark, as defined at 33 CFR 328.3(e), which contributes flow, either directly or through another water, 

to a water identified in paragraphs (a)(1) through (4) of this section. In addition, wetlands, lakes, and ponds are 

tributaries (even if they lack a bed and banks or ordinary high water mark) if they contribute flow, either directly 

or through another water to a water identified in paragraphs (a)(1) through (3) of this section. A water that 

otherwise qualifies as a tributary under this definition does not lose its status as a tributary if, for any length, 

there are one or more man-made breaks (such as bridges, culverts, pipes, or dams), or one or more natural 

breaks (such as wetlands at the head of or along the run of a stream, debris piles, boulder fields, or a stream that 

flows underground) so long as a bed and banks and an ordinary high water mark can be identified upstream of 

the break. A tributary, including wetlands, can be a natural, man-altered, or man-made water and includes 

waters such as rivers, streams, lakes, ponds, impoundments, canals, and ditches not excluded in paragraph 

(2)(iii) or (iv) of this definition.”

The lack of specificity in the Report’s definition may be problematic since it does not make clear that the full 

extent of the tributary network is included (e.g., headwaters, perennial/ephemeral/intermittent streams), and so the 

Report does not clearly support the draft rule. 

I welcome the clarification that tributaries includes headwaters, and tributaries do not lose their status due to manFennessy Comments Page 29
Individual comments from members of the SAB Panel for the Review of the EPA Water Body Connectivity Report. 

These comments do not represent consensus SAB advice or EPA policy.

made or natural breaks. I also support the clarification that wetlands at the head of a stream (headwater wetlands) 

are included in the definition (P. 22203). This is very clearly supported by the available literature and the Report, 

which concludes that wetlands can (for instance) be important water sources, habitats, and exporters of organic 

carbon. 

The draft rule asks for comments about whether wetlands that connect tributary segments and adjacent wetlands 

should be considered tributaries (noting that tributaries have beds, banks and OHWM), or are they best considered 

jurisdictional as adjacent waters. To keep the definition of tributary as clean as possible, I recommend that 

wetlands be removed from the definition of tributaries. Typically they do not have the features used to define 

tributaries (bed, banks, and OHWM). Basing their jurisdiction on adjacency is more clear, and removes 

ambiguity about the interpretation of what is a tributary. Wetlands that connect tributaries or sit at the top of 

headwater streams (headwater wetlands) would remain jurisdictional. 

2. The proposed rule has defined Waters of the U.S. under the jurisdiction of the Clean Water Act to mean all 

waters, including wetlands, adjacent to a traditional navigable water, interstate water, the territorial seas, 

impoundment, or tributary. This definition is based on the conclusion that a significant nexus exists between 

adjacent water bodies (as defined in the proposed rule) and traditional navigable waters, interstate waters, and 

the territorial seas. Please comment on the adequacy of the scientific and technical basis of this proposed 

definition. 

I support the definition of “adjacent waters” as Waters of the U.S. in the draft rule, and the change from the more 

limited inclusion of “adjacent wetlands.” The definition recognizes the importance of adjacent waters to the 

chemical, physical, or biological functions of other waters (defined as (a)(1) to (a)(5) water bodies). The term 

“neighboring” is used as a means to determine adjacency. The draft rule includes definitions of “riparian area” 

and “floodplain” to define the lateral reach of what is “neighboring.” This seems reasonable, but again relies on 

how the riparian areas and floodplains are identified on the ground. 

Adjacent (neighboring) waters can also be defined by having a shallow subsurface hydrologic connection to a 

jurisdictional water (which is vaguely defined as water within or below the root zone (12”) of the soil, p 22208). 

The draft rule goes on to say that the strength of the connection, and the determination of neighboring 

(adjacency), can be assessed by the distance (proximity) between water bodies and jurisdictional waters. While in 

some circumstances distance can serve as a proxy for the degree of connectivity, it may also be misleading, for 

example in considering the movement of biota (which varies temporally and by species), or the variability in 

water flows through shallow subsurface connections (due for example, to the availability of water, or the nature of 

the substrate). The definition of adjacent waters should not rest solely on either 1) geographical proximity (as 

suggested on p. 22209) or 2) a hydrologic connection. In particular, the movement of biota as a means to establish 

connectivity should be acknowledged. Limiting the definition of connectivity only to hydrologic connectivity 

ignores a wealth of literature, and the findings of both the Connectivity Report and the SAB report that discuss the 

integrated nature of physical, chemical and biological connectivity – as Justice Kennedy stated, we should 

consider a functional definition of how connectivity ‘benefits the chemical, physical and biological integrity of 

the Nation’s waters.’ The SAB report makes many suggestions on incorporating the four dimensions of 

connectivity into an integrated landscape view of ‘riverscapes’ to aid in our understanding of waters in riparian 

and floodplain settings. Implementing this will require metrics for chemical and biological connectivity. 

The definition of ‘riparian’ is problematic as it is based (once again) on hydrologic flows and not the host of other 

functionas that riparian areas provide. The SAB report contains extensive comments on the role of riparian zones 

in temperature regulation, carbon export, etc. 

Finally, there are inconsistencies in how riparian/floodplain waters are described, for example by referring to 

them on p. 22224 as “bidirectional.” The SAB panel clearly disagreed with the terms unidirectional and 

bidirectional, stating, “ these terms do not adequately describe the four-dimensional (longitudinal, lateral, vertical, 

and temporal) nature of connectivity, and the SAB recommends that the Report use more commonly understood 

Fennessy Comments Page 30
Individual comments from members of the SAB Panel for the Review of the EPA Water Body Connectivity Report. 

These comments do not represent consensus SAB advice or EPA policy.

terms that are grounded in the peer-reviewed literature.” 

3. The proposed rule has defined Waters of the U.S. under the jurisdiction of the Clean Water Act to mean, on 

a case-specific basis, other waters including wetlands, provided that those waters alone, or in combination with 

other similarly situated waters, including wetlands, located in the same region, have a significant nexus to a 

traditional navigable water, interstate water, or the territorial seas. Please comment on the adequacy of the 

scientific and technical basis of this propose. 

This definition of other waters works conceptually, and it acknowledges the cumulative effects of wetlands and 

other waters on downstream water integrity on a watershed basis, but I wonder how it will be put into practice. 

Defining waters that, ‘either alone or in combination with other waters similarly situated in the region 

significantly affect the chemical, physical, or biological integrity of waters of the U.S. in a way that is more than 

speculative or insubstantial’, will need substantial guidance to operationalize its implementation in the field. 

When is an effect more than speculative or insubstantial? Adopting the framework suggested in the SAB Panel 

report would help address this by recognizing the gradient of connectivity and where thresholds may be crossed. 

And while evaluation of ‘other waters’ on a case-by-case basis (with no specified criteria) does not further the 

goal of providing regulatory predictability, in some cases the BPJ of agencies in the field will have to be relied 

upon. This again will require the development of methods to determine when a nexus is significant, including 

metrics based on hydrologic, chemical and biological connectivity. As it stands now, the draft rule stresses 

hydrologic connectivity with little recognition of other vectors of connectivity such as the movement of biota. A 

key question is where, along the gradient of connectivity, do the effects of other waters become significant? 

Basing the definition on similarly situated waters, and their cumulative contribution to the integrity of 

downstream waters, is a sound approach. It is well established that wetlands that share a common 

hydrogeomorphic setting have similar functions and make similar contributions to downstream waters. I also 

support the recognition in the draft rule that other waters that lack ‘bidirectional hydrologic exchanges’ can have 

important effects on the integrity of downstream waters (pg 22223), however this should be reflected more fully 

in the working definitions provided. 

4. The proposed rule defines other terms and excludes specified waters and features from the definition of 

Waters of the U.S. Please comment on the adequacy of the scientific and technical basis of the other 

definitions and exclusions.

There are several problematic exclusions. Removing a selection of ditches from jurisdiction includes those that 

are excavated in uplands, drain uplands, but presumably drain into jurisdictional waters (which begs the question, 

where do they drain to?). For example, the exclusion of “ditches that are excavated wholly in uplands, drain only 

uplands, and have less than perennial flow” might apply to much of northwestern Ohio, which is notoriously flat, 

so much so that it is difficult to move water off the land. When they do flow, they move water and much 

agricultural run-off to Lake Erie, resulting in this summer’s HAB and the loss of drinking water Toledo and 

surrounding areas. These ditches clearly have an effect on downstream water quality (in the broad sense). 

The exclusion of gullies and rills is also problematic. These are noted at several points in the draft rule as 

important conduits for moving water between jurisdictional waters, making them an important form of 

hydrological (and other types of) connectivity. Page 22210 says that “Examples of confined surface water 

hydrologic connections that demonstrate adjacency are swales, gullies, and rills. The frequency, duration, and 

volume of flow associated with these confined surface connections can vary greatly depending largely on factors 

such as precipitation, snowmelt, landforms, soil types, and water table elevation. It is the presence of this 

hydrologic connection which provides the opportunity for neighboring waters to influence the chemical, physical, 

or biological integrity of (a)(1) through (a)(5) waters.” The draft rule goes on to say that they are important in “fill 

and spill” waters, where flows spill from other waters/wetlands through gullies to stream channels (for example). 

It isn’t clear how or why gullies that link two jurisdictional waters can be excluded.

Fennessy Comments Page 31
Individual comments from members of the SAB Panel for the Review of the EPA Water Body Connectivity Report. 

These comments do not represent consensus SAB advice or EPA policy.

Dr. Michael Gooseff

Preliminary Written Comments on proposed new EPA CWA rule. 

13 August 2014

1. The proposed rule has defined Waters of the U.S. under the jurisdiction of the Clean Water Act to 

mean all tributaries of a traditional navigable water, interstate water, the territorial seas, or 

impoundment. This definition is based on the conclusion that a significant nexus exists between 

tributaries (as defined in the proposed rule) and the traditional navigable waters, interstate waters, and 

the territorial seas into which they flow. Please comment on the adequacy of the scientific and technical 

basis of this proposed definition. (lead discussants are: Drs. Emma Rosi-Marshall and Jennifer Tank) 

This is a reasonable linkage to make. We generally understand that headwaters flow into higher order, 

larger streams and eventually into rivers, moving down the river network. This obvious connectivity 

directly implies that the degradation of any point of the network will cause some change to the 

downstream parts of the network, where the covered waters are found. The converse is also true –

that the improvement of quality of tributaries can also improve the quality of downstream waters. The 

condition of a stream or river is not solely a function of tributary conditions, but upstream tributaries 

provide the greatest amount of stream flow (and dissolved and suspended material loads) to 

downstream waters, and therefore, tributaries are generally accepted to have a significant influence 

on downstream conditions.

2. The proposed rule has defined Waters of the U.S. under the jurisdiction of the Clean Water Act to 

mean all waters, including wetlands, adjacent to a traditional navigable water, interstate water, the 

territorial seas, impoundment, or tributary. This definition is based on the conclusion that a significant 

nexus exists between adjacent water bodies (as defined in the proposed rule) and traditional navigable 

waters, interstate waters, and the territorial seas. Please comment on the adequacy of the scientific and 

technical basis of this proposed definition. (lead discussants are: Drs. Siobhan Fennessy and Mazeika 

Sullivan) 

The qualification of neighboring water bodies to covered waters is reasonable. It is rare, if ever, to find 

no connection between the covered water body and those that are within the riparian zone or 

floodplain of the water body. One challenge here, however, is that the reference to floodplains and 

riparian zones ultimately infers connectivity of a stream or river to water bodies within these adjacent 

regions. A reasonable question to ask is to what similar extent should other water bodies (e.g. lakes) 

have significant nexus with neighboring water bodies? Lakes, for example, may have a definable 

riparian zone, but rarely have “floodplains” or high water marks that induce such a dynamic change in 

stage and width of the surrounding area as the floodplains of streams and rivers. While great size is not 

necessarily a requirement of such consideration, it seems likely that the typical geomorphic position of 

lakes (as low points in the local area) lend themselves to physical connection via defined surface flow 

or shallow subsurface flow to neighboring water bodies (streams, ponds, wetlands, etc.). Biological 

connections are perhaps more likely among neighboring water bodies and non-stream or river waters 

as different water bodies may provide different habitat conditions for different life stages, prey 

communities, etc. 

Gooseff Comments Page 32
Individual comments from members of the SAB Panel for the Review of the EPA Water Body Connectivity Report. 

These comments do not represent consensus SAB advice or EPA policy.

3. The proposed rule has defined Waters of the U.S. under the jurisdiction of the Clean Water Act to 

mean, on a case-specific basis, other waters including wetlands, provided that those waters alone, or in 

combination with other similarly situated waters, including wetlands, located in the same region, have a 

significant nexus to a traditional navigable water, interstate water, or the territorial seas. Please comment 

on the adequacy of the scientific and technical basis of this proposed definition. (lead discussants are: 

Drs. Emily Bernhardt and Michael Gooseff) 

I interpret this to mean that the other waters are those that are not neighboring. When this is the 

case, it seems the significant nexus concept provides two extreme opportunities to determine 

jurisdiction of a single other water body under the CWA – 1) assume all other waters are under 

jurisdiction of the CWA until otherwise proven to have no significant nexus [though may have some 

nexus regardless], and 2) assume all other waters are not under the jurisdiction of the CWA until 

otherwise proven to have a significant nexus to a covered water body. The approach of the new rule 

provides a reasonable intermediate, that a case-specific assessment must be made to determine 

whether and what sort of nexus may exist between the water bodies (physical, chemical, and/or 

biological), and how significant the nexus is. Connections between other water bodies and covered 

waters may be infrequent and may be invisible at the surface because of a groundwater-mediated 

exchange of mass and energy between the water bodies. This may indeed prove to be either 

significant or less than significant after assessment. In my opinion, the case-specific analysis still 

provides the opportunity for the determination to go either way, rather than de facto categorization 

(the two cases suggested above) that would have to be overturned to determine the true state of the 

other water body. Ultimately, the variety of these water bodies and the potential connection types, 

strengths, and frequencies will determine both whether and how significant any connection could be. 

This variety of possibilities makes it difficult if not impossible to broadly categorize connection type and 

significance.

4. The proposed rule defines other terms and excludes specified waters and features from the definition 

of Waters of the U.S. Please comment on the adequacy of the scientific and technical basis of the other 

definitions and exclusions. (lead discussants are: Drs. David Allan and Mark Rains) 

The determination of waste treatment systems, converted cropland, upland ditches with no direct 

connection to a covered water body, reflecting pools and swimming pools, ornamental waters, and rills 

and gullies, and water-filled depressions from construction activities as specific exclusions of the CWA 

jurisdiction seem reasonable to me. I question two of these exclusions in part – 1) artificial lakes and 

ponds and 2) groundwater. Firstly, I recognize that artificially generated stock ponds, irrigation ponds, 

settling basins, or rice ponds are generated for specific anthropogenic and utilitarian reasons. 

However, assuming de facto that they have no connection to a downstream water without any 

assessment is an over simplification of most systems. What happens when any of these artificial water 

bodies over flow? A low frequency connection between these water body types could occur via a 

direct surface connection. The flux of material (solutes, sediment, etc.) may impair the receiving water 

body, thereby degrading the physical, chemical, and/or biological status of the receiving water, even if 

Gooseff Comments Page 33
Individual comments from members of the SAB Panel for the Review of the EPA Water Body Connectivity Report. 

These comments do not represent consensus SAB advice or EPA policy.

temporary. I am not sure of a solution to this issue, but it seems that these are likely to be similarly 

situated to other water bodies that may be considered adjacent without being considered to be 

neighboring and a case by case analysis of these may be warranted for similar reasoning. Secondly, I 

generally agree that groundwater, sourced from infiltration at locations distal to the covered water 

body is reasonably out of jurisdiction of the CWA, particularly because groundwater is regulated 

separately. However, it is well recognized that one often found connection between water bodies is 

that of a shallow subsurface flow path. Is infiltrating surface water considered groundwater or not? 

This is a reasonable question to debate. Hyporheic zones of streams and rivers are characterized by a 

mixing of two waters: surface water and groundwater. But if the surface water has left the channel by 

following hydraulic gradients that force it into the subsurface, is it still surface water? How long does it 

need to be in the subsurface to become groundwater? Infiltrating surface water carries with it the 

energy (i.e., temperature), chemical, and biological signatures that it had at the surface, and some of 

these change quickly and some change slowly in response to reactions with subsurface constituents, 

interactions with microbial communities, redox gradients that drive chemical species change, and 

mixing with groundwater (in this case, water that infiltrated from precipitation distant from the water 

body and floodplain and has been slowly transported through an aquifer or series of aquifers to the 

subsurface vicinity of the surface water body). In the case of hyporheic exchange, at least some 

proportion of the water that left a stream channel will come back to the channel, but it will have 

different chemical, thermal, and biological signatures than it did when it left the channel. My sense is 

that some hydrologists would consider this exchanging surface water to be groundwater as soon as it 

leaves the channel. Is it possible to differentiate groundwaters or define a threshold of residence time 

in the subsurface that qualifies exchanging surface water to be surface water in the subsurface, and 

not groundwater?

Gooseff Comments Page 34
Individual comments from members of the SAB Panel for the Review of the EPA Water Body Connectivity Report. 

These comments do not represent consensus SAB advice or EPA policy.

Dr. Judson Harvey

Jud Harvey, USGS, Comments on EPA Proposed Definition of “Waters of the United States”

1. This reviewer suggests clarifying in the proposed technical definition of a tributary that tributaries have 

definable bed and banks and evidence of a high water mark or other evidence of surface flow. Variable 

contributing areas (VBAs) have long been recognized scientifically as the principal source of surface 

water runoff to headwater channels during and immediately following storms. The concern is that 

because VBAs may not necessarily have bed for banks, and may not necessarily have easily recognizable 

high water marks, and that they may not always exhibit the three characteristics normally associated 

with a jurisdictional wetland. Thus VBAs may not be deemed jurisdictional despite their well understood 

role in collecting and concentrating rainfall and shallow subsurface flow and generating shallow surface 

flows that transfer the waters downstream in ways that ultimately exert a strong influence on discharge 

and water quality of navigable waters. These areas deserve careful consideration in the definition of 

tributaries (through the suggested amendment of the definition shown in bold above.) 

2. The technical definition of wetlands “adjacent” to navigable waters used in the proposed rule is not well 

defined in a manner that can accomplish the stated objective of creating “bright line” distinctions 

between jurisdictional and non-jurisdictional settings. This reviewer suggests clarifying the boundaries 

of adjacency and its relation to the term “floodplain wetlands” used in the SAB technical review 

document. Using “adjacency” as a criterion has the advantage of identifying wetlands that EPA clearly 

means to be jurisdictional (e.g. wetlands located directly upstream of a tributary channel head) that may 

not meet the definition of “floodplain” wetlands because such areas typically lack clear evidence of 

sediment erosion and accretion. However, using adjacency as a criterion has the disadvantage that it 

offers little useful guidance for defining the outer boundaries of adjacency. On the other hand, using 

floodplain extent as a useful boundary for defining adjacency is problematic as well since the spatial 

extent of floods varies with the timescale of flooding across the spectrum of intra-annual floods to 

floods with return periods of many centuries. 

3. Suggest clarifying in the proposed technical definition the possible relation between ephemeral 

tributaries, which are proposed to be jurisdictional, and natural swales, which presently are not 

proposed to be jurisdictional unless they meet the strict definition of a wetland and the test of 

adjacency or significant nexus. Portions of natural swales often are located directly upstream of 

tributary channel heads often become saturated and generate overland flow during storms that creates 

flow in perennial streams, rivers, and downstream navigable waters. These areas have been described 

in the scientific literature for more than fifty years and are summarized in the SAB technical review of 

the EPA connectivity document as “variable contributing areas”, i.e., VBAs. On page 22219 EPA asks for 

guidance on the possible jurisdictional nature of such swales. This reviewer suggests that the subset of 

swales that generate surface flow into headwaters during “typical” storm conditions, e.g. rains of 

intensities exceeding 0.25 inches per hour, are principal generators of the flow in headwater streams 

and have a major influence on hydrological and chemical conditions of headwaters and should be 

Harvey Comments Page 35
Individual comments from members of the SAB Panel for the Review of the EPA Water Body Connectivity Report. 

These comments do not represent consensus SAB advice or EPA policy.

considered for inclusion as part of tributaries (see bold text suggested for addition to tributary definition 

in point 1 above). Such inclusion is well supported by watershed science. 

4. Suggest clarifying in the proposed definition why manmade ditches must have to have perennial flow to 

be jurisdictional whereas tributaries only must have ephemeral flow. On page 2203 the EPA seeks 

guidance on the appropriate flow requirements for a ditch located wholly in uplands to be jurisdictional. 

In particular it would appear that ditches with intermittent flow would supply considerable water, 

sediment, nutrients, metals such as zinc from tire wear, etc. to headwater streams and there would 

appear to be no reason such features should not be considered jurisdictional. Although it is true that 

there is only a relatively small literature on hydrological and chemical effects of manmade ditches the 

list is growing and is summarized in the SAB technical review of the EPA connectivity document. 

Harvey Comments Page 36
Individual comments from members of the SAB Panel for the Review of the EPA Water Body Connectivity Report. 

These comments do not represent consensus SAB advice or EPA policy.

Dr. Lucinda Johnson

Lucinda Johnson comments to Draft Rule

I wish to commend the authors of the proposed rule for drafting a document that largely reflects the 

existing science and do not expand the regulatory authority of the EPA unnecessarily. The proposed 

rule protects precious aquatic resources and acknowledges the important ecosystem services that are 

provided by waters, alone or in aggregate. One of the important features of the rule is the definition 

the term “significant nexus”, and the acknowledgement that a connection can exist along a gradient. 

(“The relationship that waters can have to each other and connections downstream that affect the chemical, 

physical, or biological integrity of traditional navigable waters , interstate waters, or the territorial seas is not 

an all or nothing situation. The existence of a connection, a nexus, does not by itself establish that it is a 

‘‘significant nexus.’’ There is a gradient in the relation of waters to each other, and this is documented in 

the Report.” The existence of a gradient is an important component of the SAB panel’s findings.

Questions 

1. The proposed rule has defined Waters of the U.S. under the jurisdiction of the Clean Water Act to mean all 

tributaries of a traditional navigable water, interstate water, the territorial seas, or impoundment. This 

definition is based on the conclusion that a significant nexus exists between tributaries (as defined in the 

proposed rule) and the traditional navigable waters, interstate waters, and the territorial seas into which they 

flow. Please comment on the adequacy of the scientific and technical basis of this proposed definition. (lead 

discussants are: Drs. Emma Rosi-Marshall and Jennifer Tank) 

This definition is completely consistent with the science, the conclusions of the draft report and the SAB 

panel findings. It is significant that this definition includes wetlands, natural, man-altered, or man-made 

waters that contribute flow to “water of the U.S.” and that breaks such as bridges, culverts, pipes and dams) 

do not change the status of those waters. Streams that disappear underground as a function of human 

alteration or natural geology must retain their protection as they clearly contribute to the integrity of the 

tributaries to which they connect above-ground, and to the integrity of the downstream waters. 

As noted in the SAB review report, the scale of maps used to define tributaries is a critical consideration, as 

the vast majority of ephemeral streams that meet the criteria of having a bed and bank and ordinary high 

water mark may not be depicted on most existing maps. It is critical that the appropriate agencies continue to 

invest in high-resolution mapping products that will facilitate the identification of these waters without onsite inspection. 

Regarding the exclusion of two types of ditches: Exclusion of “Ditches that are excavated wholly in uplands, 

drain only uplands, and have less than perennial flow”, may be problematic because many such ditches now 

drain areas that previously would have qualified as wetlands under the Cowardin system (e.g., 

Midwestern U.S.). Such ditches now drain uplands, and may not experience perennial flow, but rather, 

may pond water without flow except under heavy precipitation events or during snowmelt, or may 

contain water and flow only during wet conditions. Because such ditches exist in heavily agricultural 

areas which are subject to runoff containing high concentrations of sediments, nutrients, and pesticides, 

these features may be important for certain ecosystem services such as attenuation nonpoint source 

pollution. It may be necessary to define a category of ditch that is embedded in a landscape that was 

previously flooded, but is now considered upland. Historical evidence of “upland” status should include 

Johnson Comments Page 37
Individual comments from members of the SAB Panel for the Review of the EPA Water Body Connectivity Report. 

These comments do not represent consensus SAB advice or EPA policy.

historic reconstructions from surveyor’s notes.

Exclusion of ephemeral features located on agricultural land that do not possess a bed and bank due to past 

farming practices seem to grant an unnecessary and potentially harmful exclusion and should be 

reconsidered. Because of the relative ease in which tile drains can now be installed, ephemeral channels 

without a bed and bank could easily be eliminated from jurisdiction. When ephemeral channels within farm 

fields are tiled, these waters deliver nutrient and pesticide-laden waters directly to downstream waters and 

increase flashy flows by reducing infiltration potential. Increased flows increase erosion and along with 

increased nutrients and pesticides, degrade water and habitat quality and biotic integrity of downstream 

waters.

The science, the EPA report, and the SAB panel all support the definition of headwater wetlands as 

jurisdictional, whether they are regarded as a tributary or under the definition of adjacent waters. To provide 

clarity for the definition, the inclusion of such wetlands as jurisdictional under the definition of “adjacent” 

waters seems the most practical, while still affording the protection necessary for these features. To further 

clarify this definition and afford protection to the full population of wetlands in this category, the definition 

of such wetlands should be based on the Cowardin classification rather than necessitating the presence of all 

three components of the Cowardin definition. If the agency is not able to apply this expanded definition to 

this class of wetland, it should maintain the current definition of headwater wetlands as tributaries, which 

entails defining such water bodies through their location in the network, rather than through their physical 

structure as possessing a bed and bank and OHWM. That said, the presence of extensive biological 

connections between these headwater wetlands and downstream jurisdictional waters should be sufficient to 

establish a “significant nexus”. As discussed extensively by the EPA’s SAB panel, the presence of 

biological connections should be considered equivalent to hydrologic connections. Such biological 

connections can be direct, e.g., through movement along corridors connection the wetlands to downstream 

flowing waters; they also can be more indirect, through microbial processes that alter nutrients, thereby 

sequestering them in sediments or in the food chain, or converting them to alternate forms.

2. The proposed rule has defined Waters of the U.S. under the jurisdiction of the Clean Water Act to mean all 

waters, including wetlands, adjacent to a traditional navigable water, interstate water, the territorial seas, 

impoundment, or tributary. This definition is based on the conclusion that a significant nexus exists between 

adjacent water bodies (as defined in the proposed rule) and traditional navigable waters, interstate waters, 

and the territorial seas. Please comment on the adequacy of the scientific and technical basis of this proposed 

definition. (lead discussants are: Drs. Siobhan Fennessy and Mazeika Sullivan) 

See comments on headwater wetlands above.

This definition is well supported by the science, the EPA report and the SAB’s panel review. In particular it 

should be noted that the vast majority of waters that are adjacent to jurisdictional waters have with a shallow 

subsurface connection, or a biological connection that would quality as a “significant nexus”. I did not see 

the term “shallow subsurface” defined in the rule document. This should be added to the set of definitions to 

ensure consistent application of this concept.

The agency is requesting comments regarding options for providing clarity for connections through confined 

surface or subsurface hydrology. “Options could include:

1. asserting jurisdiction over all waters connected through a shallow subsurface hydrologic connection or confined surface 

hydrologic connection regardless of distance; 

2. asserting jurisdiction over adjacent waters only if they are located in the floodplain or riparian zone of a jurisdictional 

water; 

Johnson Comments Page 38
Individual comments from members of the SAB Panel for the Review of the EPA Water Body Connectivity Report. 

These comments do not represent consensus SAB advice or EPA policy.

3. considering only confined surface connections but not shallow subsurface connections for purposes of determining 

adjacency; 

4. establishing specific geographic limits for using shallow subsurface or confined surface hydrological connections as basis

for determining adjacency, including, for example, distance limitations based on ratios compared to the bank-to-bank width 

of the water to which the water is adjacent.”

I feel that the only practical, and scientifically valid choice is # 1. The science supports the contention that waters 

outside the riparian zone and floodplain connected via shallow groundwater connections OR biological 

connections can be significant, thus # 2 is not a reasonable option. (Note the references contained in the SAB 

panel report for support of the biological connection argument.) Similarly, the science strongly supports the 

contention that shallow subsurface connections are important to the chemical and physical integrity of 

downstream waters by contributing to baseflow, influencing chemical and biological processes. There is a vast 

scientific literature on the hyporheic zone on this topic. Finally, geographic limits do not seem like a practical 

option since the importance of these is likely to vary seasonally and over periods of low to high moisture regimes. 

Furthermore, the distance criterion would not account for differences in permeability and hydraulic gradient 

between the channel and source areas. Highly permeable sediment may contribute flow over longer distances 

than nearby areas with less permeable sediments.

Tools that can be used to quantify the contributions (or at minimum the presence of connections) between 

areas with shallow subsurface flows include chemical analysis of ions or isotopes to assess chemical 

signatures of the two water bodies. Since biological connections are not addressed in this portion of the rule, 

but are deemed important by the SAB panel, these connections also should be considered. Analysis of the 

biological communities and food webs (with appropriate genetic markers) may reveal the extent of biological 

connections.

Consideration of connectivity via the definition of adjacency through a shallow subsurface connection appears to 

contradict the statement “Waters located near an adjacent water but which are not themselves (independently) adjacent to an 

(a)(1)through (a)(5) water would, under the proposed rule, not be regulated under(a)(6). However, waters, including wetlands, that are 

adjacent to a wetland that meets the definition of a tributary would be considered adjacent waters.” This condition must be 

examined through the lens of the presence or absence of a shallow subsurface connection for this determination to 

be made. In the absence of a shallow subsurface connection, a biological connection should be considered as per 

the SAB panel recommendations. As the SAB panel has noted, biological connections contribute in many 

significant ways to the integrity of downstream waters through transport of energy, nutrients, introduction of 

disease vectors, and provision of habitat for biota (“...the bulk exchange of materials via biota, e.g., energy (Lowe et al. 

2005; Norlin 1967; Mason and MacDonald 1982; Polis et al. 1997; Sabo and Power 2002; Baxter et al. 2005; Spinola et al. 

2008; Pearse et al. 2011); the movement of nutrients by biota (McColl and Burger 1976; Johnston and Naiman 1987; Davis 

2003; Vrtiska and Sullivan 2009); the introduction of disease vectors (Blanchong et al. 2006); and the provisioning of 

habitat essential for biological integrity and completion of life cycles of downstream species (Brooks et al. 1998; Miyazano et 

al. 2010; Julian et al. 2013).” Pg 53 SAB panel report.

Similarly, the statement “It is the presence of this hydrologic connection which provides the opportunity 

for neighboring waters to influence the chemical, physical, o0r biological integrity of (a)(1) through (a)(5) 

waters.” Does not account for the possibility of significant biological connections, whose importance and 

existence is noted above.

3. The proposed rule has defined Waters of the U.S. under the jurisdiction of the Clean Water Act to mean, 

on a case-specific basis, other waters including wetlands, provided that those waters alone, or in combination 

with other similarly situated waters, including wetlands, located in the same region, have a significant nexus 

to a traditional navigable water, interstate water, or the territorial seas. Please comment on the adequacy of 

the scientific and technical basis of this proposed definition. (lead discussants are: Drs. Emily Bernhardt and 

Michael Gooseff)

Johnson Comments Page 39
Individual comments from members of the SAB Panel for the Review of the EPA Water Body Connectivity Report. 

These comments do not represent consensus SAB advice or EPA policy.

“Other Waters”

Based on the science and the SAB’s panel findings, consideration must be given to both the presence and the 

absence of a significant hydrologic connection; furthermore, biological connections must also be considered 

in the criteria to establish a “significant nexus” (see comments and citations for CQ2). Biological factors that 

might be added to the potential criteria (i.e., increasing size and decreasing distance, increased density of the 

“other water” in similarly situated areas) might include evidence of genetic similarity in key biotic 

assemblages; evidence of transfer of biotic materials (e.g., propagules, disease vectors) among “other waters, 

similarly situated), evidence of biota (that contribute to biological integrity of downstream waters) that 

require the downstream waters to complete their life cycle (life cycle dependency). The science suggests that 

some non-resident migratory species may significantly influence downstream waters (a)(1)-(a)(3) waters 

through a significant transfer of disease vectors, nutrients or biomass (e.g., energy (Lowe et al. 2005; Norlin 1967; 

Mason and MacDonald 1982; Polis et al. 1997; Sabo and Power 2002; Baxter et al. 2005; Spinola et al. 2008; Pearse et al. 

2011); the movement of nutrients by biota (McColl and Burger 1976; Johnston and Naiman 1987; Davis 2003; Vrtiska and 

Sullivan 2009); the introduction of disease vectors (Blanchong et al. 2006); and the provisioning of habitat essential for 

biological integrity and completion of life cycles of downstream species (Brooks et al. 1998; Miyazano et al. 2010; Julian et

al. 2013).” Pg 53 SAB panel report) in addition to the examples listed. 

It is exactly true that the determination of these waters may be resource-intensive. Thus it would behoove the 

agencies to establish a set of baseline criteria that would enable a hierarchically structured decision framework 

that would first establish the potential for hydrologic connections via surface, shallow subsurface, or groundwater 

flowpaths. The SAB panel recognized that such connections occur across a gradient that varies through time. Yet 

hydrologic modeling and / or spatial modeling in conjunction with satellite remote sensing and aerial photography 

may provide the basis for determining the presence of physical connections over time frames that include long 

duration wet regimes (c.f. Winter and Rosenberry 1998). Such an empirical depiction of “connected” landscapes 

could form the starting point for further assessments that would be followed by more rigorous analyses of 

subsurface flow paths, and subsequently biological studies that would establish whether the observed connections 

meet the standard of a “significant nexus”. While the SAB panel recognized that over space and time most water 

bodies are connect, they acknowledged that such connections may not significantly affect the integrity of

jurisdictional waters (a)(1) – (a)(3) and thus would not meet the standard of a “significant nexus”.

Determine by rule that ‘‘other waters’’ are similarly situated in certain areas of the country.

Response: Ecoregions are not appropriate spatial units over which to determine the issues of whether or 

not a region is deemed to be “similar”. Ecoregions were mainly developed based on terrestrial vegetation 

communities, in combination with soils and climate. These units are not meant to reflect hydrologic 

regions. The SAB panel recommended the use of Hydrologic Landscape Regions as a more appropriate 

base from which to delineate similar regions.

Determine by rule that certain additional subcategories of waters would be jurisdictional rather than addressed 

with a case-specific analysis, and that other subcategories of waters would be non-jurisdictional.

Response: Some specific wetland types and regions have been sufficiently well-studied to determine that they 

should be considered jurisdictional, e.g., Prairie Potholes, Carolina bays, coastal prairie wetlands. The agency 

should accelerate efforts to further establish the basis for such determinations for other classes of waters. I 

especially suggest that the in addition to western vernal ponds, that vernal ponds on the east coast and the upper 

Midwest be considered. Recent efforts to map vernal pools in northern Minnesota reveal that the density far 

exceeds previous estimates.

I do not support the proposal that remaining “other waters” automatically be classified as non-jurisdictional; 

rather, there should be an established protocol that establish the decision framework for such a decision. The 

Johnson Comments Page 40
Individual comments from members of the SAB Panel for the Review of the EPA Water Body Connectivity Report. 

These comments do not represent consensus SAB advice or EPA policy.

more structured and spatially-relevant this decision framework can be, the fewer resources each case by case 

determination will require. 

4. The proposed rule defines other terms and excludes specified waters and features from the definition of 

Waters of the U.S. Please comment on the adequacy of the scientific and technical basis of the other 

definitions and exclusions. (lead discussants are: Drs. David Allan and Mark Rains) 

I have some concern about the blanket exclusion of the “prior converted cropland” exclusion due to the fact 

that there is not timeframe defining the term ”prior”, and it is unclear how the EPA would operationalize this 

definition. The US has lost millions of acres of wetlands to cropland conversion, and losses continue as the 

technology for installing drain tiles has made it increasingly easy for individual land owners to install drain 

tiles. Wetlands perform clearly documented roles in holding flood waters, recharging water tables, removing 

sediments and nutrients, and proving essential habitat for biota that contribute to the integrity of downstream 

waters. These water bodies perform functions that benefit society at large, and not just the landowner. The 

collective loss of wetlands has resulted in millions of dollars of direct and indirect economic losses. 

Comments repeated from response to CQ 1 above. 

Regarding the exclusion of two types of ditches: Exclusion of “Ditches that are excavated wholly in uplands, 

drain only uplands, and have less than perennial flow”, may be problematic because many such ditches now 

drain areas that previously would have qualified as wetlands under the Cowardin system (e.g., 

Midwestern U.S.). Such ditches now drain uplands, and may not experience perennial flow, but rather, 

may pond water without flow except under heavy precipitation events or during snowmelt, or may 

contain water and flow only during wet conditions. Because such ditches exist in heavily agricultural 

areas which are subject to runoff containing high concentrations of sediments, nutrients, and pesticides, 

these features may be important for certain ecosystem services such as attenuation nonpoint source 

pollution. It may be necessary to define a category of ditch that is embedded in a landscape that was 

previously flooded, but is now considered upland. Historical evidence of “upland” status should include 

historic reconstructions from surveyor’s notes.

5. If you have any other comments about the adequacy of the scientific and technical basis of the proposed 

rule, please provide them as well. 

Johnson Comments Page 41
Individual comments from members of the SAB Panel for the Review of the EPA Water Body Connectivity Report. 

These comments do not represent consensus SAB advice or EPA policy.

Dr. Michael Josselyn

SAB Connectivity Panel

Comments on Adequacy of the Science to Support Proposed Rule

Dr. Michael Josselyn

August 21, 2014

My comments relating to the charge questions focus in three main areas: (1) definitions used in the proposed 

rule differ from those used in the Draft Science Report and could lead to differences in the interpretation of the 

science as it relates to the proposed legal definitions; (2) the concept of connection versus the degree of 

connectivity (e.g. gradient) and its relevance to a determination of significant effect on “navigable waters” needs 

to be clarified; and (3) the concept of aggregation of similarly situated waters and wetlands needs further 

analysis in order to inform a Final Rule.

Proposed definition of “waters of the US” to include all tributaries

Definitions

Under the proposed rule, all tributaries of navigable waters would be included as “waters of the United States” 

and subject to regulation based on their effects on navigable waters. It is important to note that the Draft 

Science Report utilizes a different definition of tributaries (e.g. streams and rivers) that relies on the presence of 

flowing water (of varying volume) whereas the Proposed Rule includes any feature that possesses certain 

indicators of an ‘ordinary high water mark’. The indicators used by the Corps and EPA to determine the 

‘ordinary high water’ mark (e.g. natural line on the shore, matted vegetation, sediment sorting) can be observed 

in very small drainages that are not usually considered in the scientific studies that deal with headwater 

streams. 

These low order features may have flow for only a few hours or days following storm events and are the most 

likely candidates for being on the low end of the gradient where effects on downstream systems are lowest or 

minimal. Because of the importance of the issue on the extent of federal jurisdiction in these headwaters, the 

science needs to be more substantial than currently demonstrated in the Draft Science Report (see comments 

below). The uncertainty and limits of the scientific knowledge should be discussed related to these features in 

the Science Report and where information is lacking, it should acknowledged.

Term Draft Science Report Proposed Rule

Tributary “a stream or river that flows into a 

higher order stream or river”

“a water physically characterized by the presence of a bed and 

banks and ordinary high water mark, as defined at 33 CFR 

328.3(e), which contributes flow, either directly or through 

another water, to a water identified in paragraphs (1)(i) through 

(iv) of this definition. In addition, wetlands, lakes, and ponds are 

tributaries (even if they lack a bed and banks or ordinary high 

water mark) if they contribute flow, either directly or through 

another water to a water identified in paragraphs (1)(i) through 

(iii) of this definition. A water that otherwise qualifies as a 

tributary under this definition does not lose its status as a 

tributary if, for any length, there are one or more man-made 

Josselyn Comments Page 42
Individual comments from members of the SAB Panel for the Review of the EPA Water Body Connectivity Report. 

These comments do not represent consensus SAB advice or EPA policy.

Term Draft Science Report Proposed Rule

breaks (such as bridges, culverts, pipes, or dams), or one or more 

natural breaks (such as wetlands at the head of or along the run of 

a stream, debris piles, boulder fields, or a stream that flows 

underground) so long as a bed and banks and an ordinary high 

water mark can be identified upstream of the break.

A tributary, including wetlands, can be a natural, man-altered, or 

man-made water and includes waters such as rivers, streams, 

lakes, ponds, impoundments, canals, and ditches not excluded in 

paragraph (2)(iii) or (iv) of this definition.”

River “A relatively large volume of flowing 

water within a visible channel, 

including subsurface water moving in 

the same direction as the surface 

water, and lateral flows exchanged 

with associated floodplain and riparian 

areas.”

Not defined. However, it is stated that tributaries include rivers 

and that some rivers are considered “navigable waters”.

Stream “A relatively small volume of flowing 

water within a visible channel, 

including subsurface water moving in 

the same direction as the surface 

water, and lateral flows with associated 

floodplain and riparian areas.”

Not defined. 

The tributary definition in the Proposed Rule also includes other features such as flood control channels, some 

ditches, underground stormwater drainage works that are not part of, nor discussed in, the Draft Science 

Report. Presumably such man-made features may alter the functions associated with the tributary or alter the 

water quality considerably—either beneficially (sediment deposition in reservoirs) or adversely (addition of 

urban storm water). The Draft Science Report focused on research from natural systems and therefore does 

not provide sufficient information on which to discuss the role of these man-made features. The Panel 

recommended that more information be provided in the Science Report on the effect of man-made features on 

connectivity—either elimination or enhancement of connectivity. In urban environments where water flows are 

largely in man-made structures, this information will be necessary to support the conclusion that impacts to 

upstream features not part of the urban infrastructure would have a significant impact on navigable waters, 

when in fact the urban infrastructure itself is the cause of the impact to water quality. 

Connectivity Gradient

Both the Draft Science Report and the Proposed Rule state that “connectivity is the degree to which 

components of a system are joined, or connected, by various transport mechanisms and is determined by the 

characteristics of both the physical landscape and the biota of the specific system”. The Panel took 

considerable time to address this issue and acknowledged that for tributary systems there is strong evidence for 

a high degree of connectivity; however, also recognized that there is a gradient for streams based on frequency, 

magnitude, and duration of flows. As stated above, the extent of the federal jurisdiction under the Proposal 

Rule would be based on indicators that can be observed in very small features that may flow for only a few 

hours or days following a rain event. The Draft Science Report acknowledged that most databases and maps do 

not portray these features (Page 4-2 lines 32-36). While they comprise a significant percentage of total stream 

length, the primary differences are that they exhibit very low durations of flow and the frequency between flow 

events, especially in the arid west, may be measured in years. As a result, while no one would argue that they 

Josselyn Comments Page 43
Individual comments from members of the SAB Panel for the Review of the EPA Water Body Connectivity Report. 

These comments do not represent consensus SAB advice or EPA policy.

are not connected via water flow at some time, their function and role in biological integrity of navigable waters 

should be considered on a gradient. 

The Draft Science report found only two studies that compared functions between various stream orders for 

headwater streams. One composite analysis that reviewed a number of studies found that nitrogen nutrient 

cycling increased with stream order (Ensign and Doyle 2006). Another study on fish diversity (Harrel et al. 1967) 

showed a direct correlation between higher stream order and fish diversity. Obviously, the presence of 

microbiota involved in nutrient transformation and occurrence of fish would be directly related to the duration 

and frequency of flow as would other ecological functions within these very low order drainages. Most of the 

other studies cited in the Draft Science Report dealt with higher order streams and it is assumed that the 

processes occurring in these systems also apply to the low (1st and 2nd) order streams. Some Panel members 

during the August discussion disagreed with this finding and stated that studies for Hubbard Brook Ecosystem 

Study should be cited. I did not have sufficient time to investigate all reports from this extensive research 

project; however, the one study that related to stream order found a gradient in the processes studied (Paul and 

Hall, 2002). Panel members also referred to Dr. Meyer’s work small streams (Meyer et al 2007). This review 

paper provided good evidence that headwater streams contribute to downstream biodiversity, but that 

gradients can and do exist for some biological organisms (e.g. fish). A reference in the Meyer paper also 

observed gradients among first to third order streams in primary production, invertebrate productivity, and fish 

(Lotrich 1973).

I was also asked if there were any papers where headwater streams were found not to be important. 

Confirmation of such a null hypothesis is not generally published and is a known constraint to evaluating the 

scientific literature. My point during the discussion was not that connectivity has not been demonstrated; but 

whether such connectivity meets the standard of being more than “insubstantial” and that all tributaries should 

be jurisdictional “by rule”. The charge questions asked if the science is sufficient to reach a conclusion on 

making all tributaries jurisdictional by rule because they all have an effect on the biological integrity of the 

navigable waters. I encourage other Panel members and the EPA to provide additional references that reject 

the null hypothesis that there is no difference in function related to headwater streams. However, if the science 

demonstrates a gradient in ecological function, there would be some situations in which low order streams, in 

and of themselves, should have a significant nexus evaluation rather than being assumed.

Aggregation

The Proposed Rule states that “the agencies conclude that tributaries, including headwaters, intermittent, and 

ephemeral streams, and especially when all tributaries in a watershed are considered in combination, have a 

significant nexus to traditional navigable waters....and when considered at a watershed scale, the scientific 

evidence supports a legal determination that they meet the “significant nexus” standard”. The Proposed Rule 

contains no definition of watershed, but does discuss the term “region” as the basis upon which to base the 

aggregation of similarly situated waters and define the “region” as the watershed of the nearest navigable 

water. Obviously, this could be a very large area that may drain significant portions of a single State2

. It would 

be hard to argue that including all the streams within such a large area in one grouping would not have an effect 

on the downstream water.

The Draft Science Report states that the “watershed scale is the appropriate context for interpreting technical 

evidence about individual watershed components” (Page 3-1) and defines a watershed as the area drained by a 

stream, river, or other water body, typically divided between one water body and another”. While this would 

2 The Proposed Rule also states that in the Arid West it may use a 10 digit hydrologic unit code watershed to deal with 

especially large watersheds; however, this issue may extend to other parts of the US.

Josselyn Comments Page 44

 
Individual comments from members of the SAB Panel for the Review of the EPA Water Body Connectivity Report. 

These comments do not represent consensus SAB advice or EPA policy.

include a watershed defined by the point of entry to a navigable water, most of the studies have focused on 

much smaller watersheds. There is considerable geologic, vegetative, and topographic variation within such a 

large area and the determination of what constitutes similarity among the tributaries within that region would 

be difficult. The Panel Report requested that the Corps and EPA “more explicitly address the cumulative effects 

of streams and wetlands on downstream waters and the spatial and temporal scales at which functional 

aggregation should be evaluated” and I recommend that this be re-emphasized in our review of the Proposed 

Rule. 

Proposed definition of adjacent wetlands and other “waters”

Definitions

The Panel discussed the issue of the difference between the definitions of wetlands as applied in the Draft 

Science Report and as regulated under the Clean Water Act and recommended that the EPA consider and 

explain how the differences between those definitions may affect the interpretation of the science to regulated 

features. In particular, the wetland definition used in the Draft Science Report is much broader than the 

wetland definition in the Proposed Rule. It is important to note that the Proposed Rule combines both 

wetlands (as defined below) and “other waters” as defined by the “ordinary high water mark” as subject to the 

same interpretation. The Draft Science Report, on the other hand, does not demonstrate, at present, the 

similarity in function and role that such features have when making its case in using the Cowardin definition. It 

is necessary that the Draft Science Report provide more scientific documentation on the functional similarities 

and differences between vegetated wetlands and open waters within floodplains and, in particular, how the 

scientific literature addresses their role in affecting biological integrity in downstream waters.

Term Draft Science Report Proposed Rule

Adjacent Not defined Means bordering, contiguous, or neighboring. 

Waters, including wetlands, separated from other 

waters of the United States by man-made dikes or 

barriers, natural river berms, beach dunes and the 

like are “adjacent waters”

Wetland An area that generally exhibits at least one of 

the following three attributes (Cowardin et al. 

1979): (1) is inundated or saturated at a 

frequency sufficient to support, at least 

periodically, plants adapted to a wet 

environment, (2) contains undrained hydric 

soil; or (3) contains nonsoil saturated by 

shallow water for part of the growing season.

Those areas that are inundated or saturated by 

surface or groundwater at a frequency and 

duration sufficient to support, and that under 

normal circumstances do support, a prevalence of 

vegetation typically adapted for life in saturated 

soil conditions. Wetlands generally include 

swamps, marshes, bogs, and similar areas.

Floodplain A level area bordering a stream or river 

channel that was built by sediment deposition 

from the stream or river under present 

climatic conditions and is inundated during 

moderate to high flow events. Floodplains 

formed under historic or prehistoric climatic 

conditions can be abandoned by rivers and 

form terraces.

An area bordering inland or coastal waters that 

was formed by sediment deposition from such 

water under present climatic conditions and is 

inundated during periods of moderate and high 

water flows. In Preamble, it states that the 

agencies will use “best professional judgment” to 

determine which flood interval to use (for 

example 10 to 20 year flood interval zone).

Riparian Transition areas or zones between terrestrial 

and aquatic ecosystems that are distinguished 

by gradients in biophysical conditions, 

ecological processes, and biota. They are 

areas which surface and subsurface hydrology 

An area bordering a water where surface or 

subsurface hydrology directly influence the 

ecological processes and plant and animal 

community structure in that area. Riparian areas 

are transitional areas between aquatic and 

Josselyn Comments Page 45
Individual comments from members of the SAB Panel for the Review of the EPA Water Body Connectivity Report. 

These comments do not represent consensus SAB advice or EPA policy.

Term Draft Science Report Proposed Rule

connect water bodies with their adjacent 

uplands. They include those portions of 

terrestrial ecosystems that significant 

influence exchanges of energy and matter with 

aquatic ecosystems.

terrestrial ecosystems that influence the exchange 

of energy and materials between these 

ecosystems.

Connectivity

By definition, all wetlands within the floodplain would be considered jurisdictional under the Proposed Rule. 

However, there is ambiguity in the definition of floodplain within the Draft Science Report and the Proposed 

Rule—both of which state that it is an area of sediment deposition and subject to flooding during moderate to 

high flood events. However, at present, there is no definition of what that flooding frequency means except the 

brief statement in the Proposed Rule that the agencies will use Best Professional Judgment and generally use 

something between a 10 and 20 year flood event. In another section, the Proposed Rule also states that 

“floodplain as defined in today’s proposed rule does not necessarily equate to the 100-year floodplain as 

defined by the Federal Emergency Management Agency (FEMA). However, the FEMA defined floodplain may 

often coincide with the current definition proposed in this rule.” Thus, there is considerable confusion over 

what the Proposed Rule is stating would be included within the category of floodplain wetlands subject to 

jurisdiction. Some panel members stated that perhaps best professional judgment is acceptable; however, it 

would run contrary to EPA’s position to provide more certainty to jurisdictional determinations. 

This is an area where science could address what is an appropriate degree of connectivity between floodplain 

wetlands and downstream waters. As the Panel has stated, over long time frames, everything is connected; 

however, the question for regulators is more limited and focuses on the measureable effects on biological 

integrity of downstream waters. Flooding frequency is a statistical analysis and should be easily equated to 

such effects and where the science is available, should be evaluated in the Final Science Report. Otherwise, 

there will be considerable confusion and uncertainty under the guidance currently contained in the Proposed 

Rule. I recommend that the Science Panel be charged by the EPA with providing more guidance, based on the 

scientific literature, how best to approach this issue.

Aggregation

Because all wetlands within floodplains are considered jurisdictional under the Proposed Rule, an analysis of 

similarly situated wetlands is not required. The change that is proposed is to define “neighboring” such that it 

would include wetlands with a confined surface water connection or a shallow groundwater connection within 

the definition of adjacent. The Proposed Rule is requesting further clarification as to what types of connections 

would suffice to make a determination that the wetland was adjacent to a regulated tributary. The Panel’s 

recommended Conceptual Framework could assist in this determination; however, it does not specifically 

address the temporal or spatial issues necessary to determine whether the wetland (or “other water”) has a 

significant effect on biological integrity of navigable waters downstream. For example, a groundwater 

connection may be the result of a very slow infiltration rate and not have any immediate effects to the adjacent 

tributary. As Izbicki (2007) found for streams in the arid west such connections may be measured in thousands 

of years. This is an area where science can provide some guidance; however, it may also be an area of 

uncertainty that the Draft Science Report should recognize.

Proposed rule related to wetlands and “waters” related to case specific analysis

Definitions

Josselyn Comments Page 46
Individual comments from members of the SAB Panel for the Review of the EPA Water Body Connectivity Report. 

These comments do not represent consensus SAB advice or EPA policy.

The Panel Report found that non-floodplain wetlands can have an effect on the biological integrity of 

downstream waters as shown in the scientific literature; however, the degree of that effect will vary on 

numerous factors and should be viewed on a gradient. The Proposed Rule requires a case-by-case analysis for 

these types of wetlands and proposes a definition for a determination of a significant nexus. The elements 

included in a significant nexus determination are from the Supreme Court decision and is not necessarily a 

hypothesis that has been tested in the scientific literature.

Term Draft Science Report Proposed Rule

Significant Nexus Not defined; not 

considered a scientific 

term

A water, including wetlands, either alone or in combination with 

other similarily situated waters in the region (i.e. the watershed that 

drains to the nearest water identified in paragraphs (1)(i) through (iii) 

of this definition significantly affects the chemical, physical, or 

biological integrity of the water. For an effect to be significant, it 

must be more than speculative or insubstantial. Other waters, 

including wetlands, are similarly situated when they perform similar 

functions and are located sufficient close together or sufficiently 

close to a “water of the United States” so that they can be evaluated 

as a single landscape unit with regard to their effect on the chemical, 

physical, or biological integrity of a water identified in the definition.

Connectivity

The Proposed Rule states that a variety of functions would need to be evaluated, including “sediment trapping, 

nutrient cycling, pollutant trapping and filtering, retention or attenuation of flood flows, runoff storage, export 

of organic matter, export of food resources, and provision of aquatic habitat”. The Proposed Rule presents a 

number of lines of evidence that can be used to assess such a connection. However, the Proposed Rule focuses 

on finding evidence of a connection; not evidence that such a connection actually plays a role in affecting the 

biological integrity of the navigable water in question. The agencies indicate that they are seeking additional 

information on how to make these judgments especially on how the analysis can be more than just speculative 

or insubstantial. A section may need to be added to the Final Science Report that addresses what type of 

connections should be evaluated and the methods by which these connections can be measured. The 

vagueness of the term “insubstantial” is more difficult to address in the Final Science Report but is an important 

question that will require quantification on a case-by-case basis. I concur with an approach that is more 

quantitative as proposed in Dr. Ali in her comments.

Aggregation

The Proposed Rule acknowledges that there are many issues that have not been resolved by the Draft Science 

Report on how similarly situated wetlands may be addressed and proposes a number of ways to either classify 

wetlands into various types or to use ecoregions. These aggregations have the advantage of being simple to 

apply by regulators; however, they are likely not entirely valid from a scientific standpoint. The Panel’s 

recommended Conceptual Model can be very useful in this type of analysis and examined these processes on a 

watershed approach.

I believe that the scientific literature has been largely organized by watershed analysis and depending upon the 

size of the watershed, there is a similarity in geology, vegetation types, and flow paths. The appropriate 

watershed may vary depending upon the geographic region of the country and the topography. The Proposed 

Rule suggests using the HUC 10 watershed unit in the arid west and this may be appropriate for other regions of 

Josselyn Comments Page 47
Individual comments from members of the SAB Panel for the Review of the EPA Water Body Connectivity Report. 

These comments do not represent consensus SAB advice or EPA policy.

the country. Watershed units are also a basis for much of the planning of TMDLs and for wetland restoration 

and rehabilitation in the US. I do not agree with the concept of “region” as proposed as it is artificial based on 

the presence of a navigable water and can result in a large area of very different wetlands being aggregated. 

I disagree with an option that would categorize certain wetlands as being jurisdictional by rule as this would 

“freeze” the science, so to speak. Given how difficult it has been to get the rule to this point, I doubt that these 

would be revisited and as mentioned by some panel members it would be difficult to figure out what categories 

would be set up and how various types of wetlands within categories would be best represented. 

Proposed definitions and exclusions

The proposed exclusions are largely androgenic features which are not addressed by the Draft Science Report. 

It is not clear, except by precedent, why other features are not also excluded such as stormwater quality basins, 

bioswales, detention basins, industrial water processing and/or treatment facilities, desalination brine storage 

basins, cooling systems, oil and gas tank basins, fish farms, rice paddies, and the like. It seems that such 

facilities, even though water is present, would deserve similar exclusions due to their specific use for water 

treatment or their isolation from navigable waters. The Panel recommended that the Draft Science Report 

discuss how human alterations may affect connectivity—either by promoting connectivity or further isolating 

tributaries and wetlands from downstream navigable waters. However, the Science Report might also discuss 

how some man-made features are designed to avoid connectivity in order to protect the environment from toxic 

or polluted water sources that are present in some of these features. The construction of any facility designed 

to retain, store, pond, treat, or process water used in industrial processes and to assure that such liquids do not 

enter the environment should be excluded from jurisdiction as a matter of rule.

The exclusion for ditches seems quite narrow. If it is meant to exclude roadside ditches, for example, the ditch 

must be entirely constructed in uplands and drain only uplands. This could mean that a highway drainage ditch, 

even though constructed mostly through wetlands, but perhaps impacting wetlands or streams along 1-2% of its 

length would then be considered a “water of the US”. The Draft Science Report did not address this issue as it 

focused on natural streams and wetlands. Ditches, especially vegetated ditches, can have functions similar to 

wetlands. Yet to regulate such features would place a considerable burden on public and private landowners 

and, in some cases, on public safety where these ditches are needed to drain floodwaters. 

Other comments/issues

The Panel’s recommended Conceptual Model includes surface and groundwater flows as a means to consider 

connectivity. The Proposed Rule only uses shallow groundwater flow as a means to address jurisdiction under 

the Clean Water Act, especially between wetland features. The Final Science Report should more fully address 

differences between shallow groundwater connections and how they are defined. 

I understand that these comments are to be appended to a Summary Report on our discussions held on August 

20-21st. However, the Summary Report has not been distributed to the Panel members for review prior to 

submission to the SAB nor is a separate report as was prepared for the Charge Questions related to the Draft 

Science Report been prepared. Given the importance of the science to the Proposed Rule, the lack of time for 

deliberate consultation by the Panel members diminishes the value of our expertise in responding to these 

Charge Questions. Additional time should have been allocated to this process as Panel members were 

specifically requested during the review of the Draft Science Report to not discuss the Proposed Rule itself.

References

Josselyn Comments Page 48
Individual comments from members of the SAB Panel for the Review of the EPA Water Body Connectivity Report. 

These comments do not represent consensus SAB advice or EPA policy.

Izbicki, J.A. 2007. Physical and temporal isolation of mountain headwater streams in the western Mojave 

Desert, Southern California. JAWRA 43(1) 26-40.

Victor A. Lotrich 1973. Growth, Production, and Community Composition of Fishes Inhabiting a First-, Second-, 

and Third-Order Stream of Eastern Kentucky. Ecological Monographs 43:377–397.

Meyer, J.L. et al. 2007. The contribution of headwater streams to biodiversity in river networks. JAWRA 43(1): 

86-103

Paul, M.J. and R.O.Hall 2002. Particle transport and transient storage along a stream-size gradient in the 

Hubbard Brook Experimental Forest. J.N. Am. Benthol. Soc. 21(2) 195-205.

Josselyn Comments Page 49
Individual comments from members of the SAB Panel for the Review of the EPA Water Body Connectivity Report. 

These comments do not represent consensus SAB advice or EPA policy.

Dr. Latif Kalin

I think EPA and the Corps have done a fantastic job. I really enjoyed reading it. The proposed rule is 

written very clearly, is comprehensive and relies on scientific evidence. Obviously, when this draft rule 

was prepared the SAB’s review of the Report was still going on (which is now complete). I would 

assume and hope that the draft rule will consider many of the recommendations in that review. For 

instance the SAB review does not recommend the use of the terms unidirectional and bidirectional, yet 

these terms appear in the draft rule. I will ignore those recommendations and list few of things I realized 

in the ruling that think need further clarification, improvement or rewording. In few places I disagree 

with the ruling.

I have seen comments on not enough emphasis on biological connectivity. If there is a clear significant 

hydrologic nexus, then that water will be considered WOTUS. Additional evidences of significant 

biological, chemical and physical nexus will only make the case stronger only. Therefore, biological 

connectivity should be concern for “other waters”, where the strength of the hydrologic connectivity is 

harder to prove. I believe the rule has enough emphasis on biological, chemical and physical 

connectivity under the “other waters” section.

The two critical areas in the draft rule that need in-depth scrutiny are “other waters of the US” and the 

“excluded waters”.

Below are my specific comments

1. I do not recommend considering wetlands as tributaries. The type of wetlands discussed in the 

rule (e.g. headwater wetlands) should still be under adjacent water body theme.

2. The report uses the term “artificially irrigated areas”. I suggest deleting the word “artificially”. 

Scientifically there is no such a term. Irrigation itself is artificial application of water.

3. On page 22213, last paragraph it is stated that “Functions of waters that might demonstrate a 

significant nexus include sediment trapping, nutrient recycling, pollutant trapping and filtering, 

retention or attenuation of flood waters, runoff storage, export of organic matter, export of food 

resources, and provision of aquatic habitat.” I suggest removing “nutrient cycling” and “export 

of organic matter” from this list. Nutrient cycling happens everywhere. Consider an agricultural 

field for example. The full N, and P cycles (mineralization, denitrification, immobilization, etc.) 

always take place. Organic matter can be exported from excluded waters too (e.g. agricultural 

ditches).

4. Page 22214, middle column: “Information derived from field observation is not required in cases 

where a “desktop” analysis can provide sufficient information to make the requisite findings.” 

Does the term “desktop analysis” mean analysis with simple tools (usually called screening 

tools), or computer models. I suggest rewriting this statement.

5. The rule solicits information on whether ecoregions or HLRs could be used in determining 

similarly situated other waters. For biological connectivity maybe level IV ecoregions could be 

Kalin Comments Page 50
Individual comments from members of the SAB Panel for the Review of the EPA Water Body Connectivity Report. 

These comments do not represent consensus SAB advice or EPA policy.

used (level III is too coarse), but this is not my expertise. I would say no to the use of HLRs, 

because it does not have a flowpath framework. 

6. The draft rule suggests excluding “Ditches that are excavated wholly in uplands, drain only 

uplands, and have less than perennial flow.” I disagree with this, because it totally ignores 

potential significant biological nexus. 

Kalin Comments Page 51
Individual comments from members of the SAB Panel for the Review of the EPA Water Body Connectivity Report. 

These comments do not represent consensus SAB advice or EPA policy.

Dr. Kenneth Kolm

Comments Regarding the Adequacy of the Scientific and Technical Basis of the Proposed Rule Titled 

Definition of Waters of the United States Under the Clean Water Act (79FR 22188-22274)

Submitted on August 13, 2014

I have thoroughly and critically read the Rule and attached documentation, and have noted the text that needs 

addressing. In order to coordinate the SAB's efforts with the suggested changes to the Rule, i have cross 

referenced the original EPA Draft Report comments and the current (7-7-14) Draft Report comments with the 

suggested changes. The comments may appear repetitious, but the appropriate comments will be best 

determined during the teleconferences. 

The broader request make in the Rule is made on Page 22198:

" In addition to the proposed ‘‘other waters’’ approach in this rule, the agencies are requesting comment on a 

range of alternate approaches to inform their decision on how best to address ‘‘other waters.’’ The agencies will 

consider the full administrative record, including comments requested and received, and the final Report, as 

revised in response to the SAB review, when developing the final rule, and may adopt one of the alternative 

approaches or combination of approaches and the proposal."

This is more difficult to address since these approaches are usually not found in the "refereed literature" due to 

being too "applied" or not fitting the format of "single-variable" research that is more favored. However, there 

are approaches that are exactly what the agency is requesting and these approaches with case histories are 

written up in various Proceedings at State of the Art Meetings. i could provide a listing of these references if the 

SAB thinks this would help the Rule and Agency. The basis of these approaches are referenced:

"These elements, in context with the HLRs and Ecoregions, can then be integrated to create a flowpath network 

that describes connectivity (Heath 1983; ASTM 1996; Kolm et al. 1996; Winter et al. 1998). This approach has 

been extended to biological connectivity and hydrogeomorphic (HGM) wetland classifications (e.g., Kolm et al. 

1998)." 

The multi-temporal and multi-scale approach is called Hydrologic and Environmental Systems Analysis (HESA) for 

holistic Conceptual Site Model development, and has been applied to mine and resource development and 

mined-land restoration, municipal management of groundwater system supply and pollution, watershed and 

site-scale pollution prevention and Superfund cleanup, and water rights and water quality expert witness and 

litigation support. The most high profile case history written up in the literature is based on an NSF long term 

study where the paleohydrologic system of the Anasazi living in the Four Corners Region of the Colorado Plateau 

was assessed in the context of societal collapse: 

Kolm, K.E. and S.M. Smith. 2012. Chapter 5. Modeling Paleohydrological System Structure and Function. In 

Emergence and Collapse of Early Villages: Models of Central Mesa Verde Archaeology. Edited by T.A. Kohler and 

M.D. Varien, University of California Press; Los Angeles, CA., pp. 73-83.

Essentially, the collapse of the Ancient One's society was hypothesized to be the connectivity of the surface 

water and ground water systems and the relation to climate change (drought) and land use. Using HESA and 

Mathematical modeling, the connectivity of the surface water and ground water systems was established and 

Kolm Comments Page 52
Individual comments from members of the SAB Panel for the Review of the EPA Water Body Connectivity Report. 

These comments do not represent consensus SAB advice or EPA policy.

quantified. However, the hypothesized collapse of the society based on water resources was found to not be 

true. 

HESA is exactly what the agency is calling for in the Rule to determine connectivity or nexus, however, the 

refereed book that documents the approach is not yet completed for publication. 

Questions 

1. The proposed rule has defined Waters of the U.S. under the jurisdiction of the Clean Water Act to mean all 

tributaries of a traditional navigable water, interstate water, the territorial seas, or impoundment. This 

definition is based on the conclusion that a significant nexus exists between tributaries (as defined in the 

proposed rule) and the traditional navigable waters, interstate waters, and the territorial seas into which they 

flow. Please comment on the adequacy of the scientific and technical basis of this proposed definition. (lead 

discussants are: Drs. Emma Rosi-Marshall and Jennifer Tank) 

Page 22205:

Tributaries, even when seasonally dry, are the dominant source of water in most rivers, rather than direct 

precipitation or groundwater input to main stem river segments.

In the arid and semi-arid lands, this statement is not necessarily true, and groundwater is the dominant 

source of flow to both tributaries and the main stem river segments. For example, various gaining 

reaches of the Meadow Creek Wash (Nevada, Las Vegas region, Basin and Range Province) and the 

Virgin River (Utah, Zion National Park and St. George region, Colorado Plateau Province) sustain the 

middle and lower reaches of their watersheds. In some volcanic and karst regions, springs and gaining 

streams are the dominant source of flow for both tributary and main stem river segments. For example, 

the middle section of the Snake River including the Twin Falls and Boise, Idaho region of the Snake 

River Plain Province is mostly sustained by groundwater, and various sections of the Green River in 

Kentucky are sustained in the Karst region near Mammoth Cave National Park. Vast sections of the Rio 

Grande River and its tributaries in southern Colorado through central New Mexico (Taos, Santa Fe, and 

Albuquerque) are sustained mostly by groundwater. 

In general, the role of regional groundwater systems is not addressed by this Rule and leaves the waters 

of the US vulnerable. The Rule focuses primarily on the site and subregional scales, perhaps due to the 

legal aspects. This tends to either ignore or at least downplay the potential significance of regional-scale 

hydrologic connectivity, especially as it relates to ground water. This is a problem because regional 

ground water flows commonly interact with the surface environment at sinks and springs. For example, 

the Floridan aquifer underlies all of Florida as well as portions of Mississippi, Alabama, Georgia, and 

South Carolina and commonly interacts with the surface environment through sinks, springs, and 

outcrops (see Sun et al. 1997 and references therein). To provide a better understanding of ground water 

connectivity, and the way that ground water connectivity might vary spatially, the SAB recommends 

that the EPA also consider using the ASTM D5979-96 Standard Guide for Conceptualization and 

Characterization of Ground Water Systems (ASTM 1996; Kolm et al. 1996). To better characterize 

regional-scale ground water connectivity, the SAB recommends that the EPA also consider using 

findings from the U.S. Geological Survey Regional Aquifer Systems Analysis (RASA) Program. An 

understanding of regional ground water flow systems is critical to the understanding of four-dimensional 

hydrologic connectivity on both the local and regional scales. Understanding ground water flow in 

Kolm Comments Page 53
Individual comments from members of the SAB Panel for the Review of the EPA Water Body Connectivity Report. 

These comments do not represent consensus SAB advice or EPA policy.

unique hydrogeologic settings, including the Floridan aquifer system (karst systems), the High Plains 

aquifer system (semi-arid systems), and the Snake River Plain and Rio Grande Rift aquifer systems 

(volcanic bedrock systems), is especially important. These and other unique hydrogeological settings are 

covered by the RASA Program (Sun et al. 1997). 

Page 22206:

The agencies are seeking comment on whether it would provide greater regulatory clarity to exclude 

such wetlands from the definition of ‘‘tributary’’ because they generally lack

a defined bed, bank and OHWM.

Wetlands in this landscape are a continuum with the tributary and\or main stem stream, and should NOT 

be excluded in this context, particularly if the main weg or flowpath is directly through the wetland from 

one upstream channel to a downstream channel. This goes along with the SAB flowpath concept: “The 

definition of connectivity in the Report should be extended to the entire landscape through a broad 

vision of local- to landscape-scale physical, chemical, and biological exchanges.”

2. The proposed rule has defined Waters of the U.S. under the jurisdiction of the Clean Water Act to mean all 

waters, including wetlands, adjacent to traditional navigable water, interstate water, the territorial seas, 

impoundment, or tributary. This definition is based on the conclusion that a significant nexus exists between 

adjacent water bodies (as defined in the proposed rule) and traditional navigable waters, interstate waters, 

and the territorial seas. Please comment on the adequacy of the scientific and technical basis of this proposed 

definition. (lead discussants are: Drs. Siobhan Fennessy and Mazeika Sullivan) 

Page 22203:

An alternate approach would be to clarify that wetlands that connect tributary segments are adjacent 

wetlands, and as such are jurisdictional waters of the United States under (a)(6). In this approach, a 

tributary would be defined as having a bed and bank and OHWM, and the upper limit of the tributary 

would be defined by the point where these features cease to be identifiable.

(Note that natural or manmade breaks would still not sever jurisdiction if a tributary segment with a bed 

and bank and OHWM could be identified upstream of the break.) Wetlands would not be considered 

tributaries, but would remain jurisdictional as adjacent waters. Wetlands that contribute flow, for 

example at the upper reaches of the tributary system, would be considered adjacent waters.

This approach would work as well as the straight tributary approach and would split off the geomorphic 

bed, bank, OHWM measurement scheme to a flowpath analysis scheme. If this adds these wetlands to 

the jurisdiction, this would be adequate for legal purposes. To clarify the connectivity of wetlands to 

“waters of the US”, the SAB recommends that a conceptual framework be established expressed as 

continuous hydrological (surface and subsurface), chemical, and biological flowpaths connecting 

watersheds from top to bottom, and therefore connecting waters and wetlands to downgradient waters. 

The flowpath framework should highlight the four-dimensional nature of connectivity, because fourdimensional connectivity scaled in a habitat-to-catchment context is a foundational aspect of freshwater 

ecology (e.g., Ward 1989). The flux and transformation of water, materials, and organisms – which 

fundamentally control the integrity of downgradient freshwater ecosystems – occur at varying rates 

primarily determined by climate, geology, topographic relief, and biology and are expressed in terms of 

surface water and ground water storage and flow through the landscape (e.g., uplands, wetlands, lakes, 

Kolm Comments Page 54
Individual comments from members of the SAB Panel for the Review of the EPA Water Body Connectivity Report. 

These comments do not represent consensus SAB advice or EPA policy.

rivers, and floodplains). Therefore, these flowpaths are inherently four-dimensional (i.e., longitudinal, 

lateral, vertical, and through time).

Page 22207:

Waters, including wetlands, determined to have a shallow subsurface hydrologic connection or confined 

surface hydrologic connection to an (a)(1) through (a)(5) water would also be ‘‘waters of the United 

States’’ by rule as adjacent waters falling within the definition of ‘‘neighboring.’’

This should be added to the adjacent waters ruling. However, why just “shallow subsurface hydrologic 

connection”? Why not deep connections as well? “Deep” could include bedrock or unconsolidated 

groundwater systems, and should include shallow, subregional, and regional systems if these waters 

proved critical to maintaining the integrity of the “waters of the United States”. Examples of this type of 

adjacent waters ruling should include the case histories of the arid and semi-arid western US systems, 

and the Karst, Fractured Rock, Sedimentary Rock, and Volcanic bedrock systems well studied across the 

US. Is interflow determined to be part of this process? Interflow is definitely a process for 

connectivity.

In general, the role of regional groundwater systems in neighboring systems is not addressed by this 

Rule and leaves the waters of the US vulnerable. The Rule focuses primarily on the site and subregional 

scales, perhaps due to the legal aspects. This tends to either ignore or at least downplay the potential 

significance of regional-scale hydrologic connectivity, especially as it relates to ground water in adjacent 

and /or neighboring systems. This is a problem because regional ground water flows commonly interact 

with the surface environment at sinks and springs. For example, the Floridan aquifer underlies all of 

Florida as well as portions of Mississippi, Alabama, Georgia, and South Carolina and commonly 

interacts with the surface environment through sinks, springs, and outcrops (see Sun et al. 1997 and 

references therein). To provide a better understanding of ground water connectivity, and the way that

ground water connectivity might vary spatially, the SAB recommends that the EPA also consider using 

the ASTM D5979-96 Standard Guide for Conceptualization and Characterization of Ground Water 

Systems (ASTM 1996; Kolm et al. 1996). To better characterize regional-scale ground water 

connectivity, the SAB recommends that the EPA also consider using findings from the U.S. Geological 

Survey Regional Aquifer Systems Analysis (RASA) Program. An understanding of regional ground 

water flow systems is critical to the understanding of four-dimensional hydrologic connectivity on both 

the local and regional scales. Understanding ground water flow in unique hydrogeologic settings, 

including the Floridan aquifer system (karst systems), the High Plains aquifer system (semi-arid 

systems), and the Snake River Plain and Rio Grande Rift aquifer systems (volcanic bedrock systems), is 

especially important. These and other unique hydrogeological settings are covered by the RASA 

Program (Sun et al. 1997). 

To clarify the connectivity of adjacent waters to “waters of the US”, the SAB recommends that a 

conceptual framework be established expressed as continuous hydrological (surface and subsurface), 

chemical, and biological flowpaths connecting watersheds from top to bottom, and therefore connecting 

waters and wetlands to downgradient waters. The flowpath framework should highlight the fourdimensional nature of connectivity, because four-dimensional connectivity scaled in a habitat-tocatchment context is a foundational aspect of freshwater ecology (e.g., Ward 1989). The flux and 

transformation of water, materials, and organisms – which fundamentally control the integrity of 

Kolm Comments Page 55
Individual comments from members of the SAB Panel for the Review of the EPA Water Body Connectivity Report. 

These comments do not represent consensus SAB advice or EPA policy.

downgradient freshwater ecosystems – occur at varying rates primarily determined by climate, geology, 

topographic relief, and biology and are expressed in terms of surface water and ground water storage 

and flow through the landscape (e.g., uplands, wetlands, lakes, rivers, and floodplains). Therefore, these 

flowpaths are inherently four-dimensional (i.e., longitudinal, lateral, vertical, and through time).

Ground water connectivity, in particular, could be better represented in the Rule. The U.S. Geological 

Survey (USGS) has published numerous reports and learning tools on ground water connectivity, 

including examples of flowpath frameworks expressed in block diagrams (Heath 1983, 1984; Winter et 

al. 1998), that contain flows through floodplains. Care should be taken not to imply that bedrock is 

impermeable because ground water flows through bedrock are important flowpaths that connect 

hydrologic landscapes over long distances and often across watershed boundaries (e.g., Roses et al. 

1996). 

Page 22207:

In circumstances where a particular water body is outside of the floodplain and riparian area of a 

tributary, but is connected by a shallow subsurface hydrologic connection or confined surface 

hydrologic connection with such tributary, the agencies will also assess the distance between the water 

body and tributary in determining whether or not the water body is adjacent. ‘‘Adjacent’’ as defined in 

the agencies’ regulations has always included an element of reasonable proximity.

Distance to water body frequently is not the story. Regarding groundwater connectivity, the 

hydrogeologic framework and properties (thickness, continuity, for example), including hydraulic 

conductivity and storativity/storage; and the subsurface source, pathway, and discharge region are 

important for relevance in protecting “waters of the US”. We need to know the hydrogeologic 

framework and groundwater flow system for connectivity. Is interflow determined to be part of this 

process? Interflow is definitely a process for connectivity. The U.S. Geological Survey (USGS) has 

published numerous reports and learning tools on ground water connectivity, including examples of 

flowpath frameworks expressed in block diagrams (Heath 1983, 1984; Winter et al. 1998), that contain 

flows through floodplains. Care should be taken not to imply that bedrock is impermeable because 

ground water flows through bedrock are important flowpaths that connect hydrologic landscapes over 

long distances and often across watershed boundaries (e.g., Roses et al. 1996). 

To clarify the connectivity of adjacent waters to “waters of the US”, the SAB recommends that a 

conceptual framework be established expressed as continuous hydrological (surface and subsurface), 

chemical, and biological flowpaths connecting watersheds from top to bottom, and therefore connecting 

waters and wetlands to downgradient waters. The flowpath framework should highlight the fourdimensional nature of connectivity, because four-dimensional connectivity scaled in a habitat-tocatchment context is a foundational aspect of freshwater ecology (e.g., Ward 1989). The flux and 

transformation of water, materials, and organisms – which fundamentally control the integrity of 

downgradient freshwater ecosystems – occur at varying rates primarily determined by climate, geology, 

topographic relief, and biology and are expressed in terms of surface water and ground water storage 

and flow through the landscape (e.g., uplands, wetlands, lakes, rivers, and floodplains). Therefore, these 

flowpaths are inherently four-dimensional (i.e., longitudinal, lateral, vertical, and through time). 

Kolm Comments Page 56
Individual comments from members of the SAB Panel for the Review of the EPA Water Body Connectivity Report. 

These comments do not represent consensus SAB advice or EPA policy.

In general, the role of regional groundwater systems is not addressed by this Rule and leaves the waters 

of the US vulnerable. The Rule focuses primarily on the site and subregional scales, perhaps due to the 

legal aspects. This tends to either ignore or at least downplay the potential significance of regional-scale 

hydrologic connectivity, especially as it relates to ground water. This is a problem because regional 

ground water flows commonly interact with the surface environment at sinks and springs. For example, 

the Floridan aquifer underlies all of Florida as well as portions of Mississippi, Alabama, Georgia, and 

South Carolina and commonly interacts with the surface environment through sinks, springs, and 

outcrops (see Sun et al. 1997 and references therein). To provide a better understanding of ground water 

connectivity, and the way that ground water connectivity might vary spatially, the SAB recommends 

that the EPA also consider using the ASTM D5979-96 Standard Guide for Conceptualization and 

Characterization of Ground Water Systems (ASTM 1996; Kolm et al. 1996). To better characterize 

regional-scale ground water connectivity, the SAB recommends that the EPA also consider using 

findings from the U.S. Geological Survey Regional Aquifer Systems Analysis (RASA) Program. An 

understanding of regional ground water flow systems is critical to the understanding of four-dimensional 

hydrologic connectivity on both the local and regional scales. Understanding ground water flow in 

unique hydrogeologic settings, including the Floridan aquifer system (karst systems), the High Plains 

aquifer system (semi-arid systems), and the Snake River Plain and Rio Grande Rift aquifer systems 

(volcanic bedrock systems), is especially important. These and other unique hydrogeological settings are 

covered by the RASA Program (Sun et al. 1997). 

Page 22208:

Therefore, the determination of whether a particular water meets the definition of ‘‘neighboring’’ 

because the water is connected by a shallow subsurface or confined surface hydrologic connection is 

made in the context of the terms ‘‘neighboring’’ and ‘‘adjacent’’ as used

in the regulation.

Why just shallow subsurface? Is this groundwater or interflow or both? Distance to water body 

frequently is not the story. Regarding groundwater connectivity, the hydrogeologic framework and 

properties (thickness, continuity, for example), including hydraulic conductivity and storativity/storage; 

and the subsurface source, pathway, and discharge region are important for relevance in protecting 

“waters of the US”. Need to know the hydrogeologic framework and groundwater flow system for 

connectivity. Is interflow determined to be part of this process? Interflow is definitely a process for 

connectivity. The U.S. Geological Survey (USGS) has published numerous reports and learning tools 

on ground water connectivity, including examples of flowpath frameworks expressed in block diagrams 

(Heath 1983, 1984; Winter et al. 1998), that contain flows through floodplains. Care should be taken not 

to imply that bedrock is impermeable because ground water flows through bedrock are important 

flowpaths that connect hydrologic landscapes over long distances and often across watershed boundaries 

(e.g., Roses et al. 1996).

To clarify the connectivity of neighboring waters to “waters of the US”, the SAB recommends that a 

conceptual framework be established expressed as continuous hydrological (surface and subsurface), 

chemical, and biological flowpaths connecting watersheds from top to bottom, and therefore connecting 

waters and wetlands to downgradient waters. The flowpath framework should highlight the fourdimensional nature of connectivity, because four-dimensional connectivity scaled in a habitat-tocatchment context is a foundational aspect of freshwater ecology (e.g., Ward 1989). The flux and 

Kolm Comments Page 57
Individual comments from members of the SAB Panel for the Review of the EPA Water Body Connectivity Report. 

These comments do not represent consensus SAB advice or EPA policy.

transformation of water, materials, and organisms – which fundamentally control the integrity of 

downgradient freshwater ecosystems – occur at varying rates primarily determined by climate, geology, 

topographic relief, and biology and are expressed in terms of surface water and ground water storage 

and flow through the landscape (e.g., uplands, wetlands, lakes, rivers, and floodplains). Therefore, these 

flowpaths are inherently four-dimensional (i.e., longitudinal, lateral, vertical, and through time). 

Page 22208:

While the agencies’ best professional judgment has always been a factor in determining whether a 

particular wetland is ‘‘adjacent’’ under the existing definition, the agencies recognize that this may 

result in some uncertainty as to whether a particular water connected through confined surface or 

shallow subsurface hydrology is an ‘‘adjacent’’ water. The agencies therefore request comment on 

whether there are other reasonable options for providing clarity for jurisdiction over waters with these 

types of connections.

Regarding shallow subsurface hydrology of an “adjacent water’, the U.S. Geological Survey (USGS) 

has published numerous reports and learning tools on ground water connectivity, including examples of 

flowpath frameworks expressed in block diagrams (Heath 1983, 1984; Winter et al. 1998), that contain 

flows through floodplains. Care should be taken not to imply that bedrock is impermeable because 

ground water flows through bedrock are important flowpaths that connect hydrologic landscapes over 

long distances and often across watershed boundaries (e.g., Roses et al. 1996). Future efforts to 

determine whether a particular wetland is “adjacent” and to quantify connectivity can be informed by 

the wide variety of conceptual models and quantitative tools that have been developed to evaluate the 

connectivity of both surface and subsurface hydrological systems in different settings, including nonfloodplain wetlands. The standard approach involves first characterizing the surface and subsurface 

elements of landscapes. Important elements include climate, geology, topographic relief, and the 

amount, distribution and types of waters and wetlands. These elements can then be integrated to create a 

flowpath network that describes connectivity (Heath 1983; ASTM 1996; Kolm et al. 1996; Winter et al. 

1998). This approach has been extended to biological connectivity and hydrogeomorphic (HGM) 

wetland classifications (e.g., Kolm et al. 1998). Of course, the approach to quantifying hydrologic 

connectivity is not identical across systems, and careful attention must be given to identifying the most 

appropriate techniques (Healy et al. 2007; Bracken et al. 2013) and metrics (Ali and Roy 2010). 

Other examples can be found in the literature related to water quantity and quality modeling (Appel and 

Reilly 1994; Sun et al. 1997; Harbaugh 2005; Parkhurst et al. 2010; Cunningham and Schalk 2011), and 

integrated surface water ground water modeling (Markstrom et al. 2008; Ely and Kahle 2012; 

Huntington and Niswonger 2012; Woolfenden and Nishikawa 2014), sediment transport modeling 

(Nelson et al. 2003; McDonald et al. 2005), and watershed and biological/habitat/landscape modeling 

(Kinzel et al. 1999; Kinzel et al. 2005; Hunt et al. 2013). Approaches have also been developed to 

quantify linkages due to ground water movement and storage (Heath 1983) and the effects of “flood 

pulses” (Kolm et al. 1998). Likewise, the role of chemical movement and storage to ground water 

systems in floodplains has been quantified by flow and transport modeling (Winter et al. 1998; 

Markstrom et al. 2008; Woolfenden and Nishikawa 2014) as well as with steady-state and transient 

analyses that simulate temporal changes (Appel and Reilly 1994; Winter et al. 1998; Nelson et al. 2003; 

Kolm Comments Page 58
Individual comments from members of the SAB Panel for the Review of the EPA Water Body Connectivity Report. 

These comments do not represent consensus SAB advice or EPA policy.

Conaway and Moran 2004; Harbaugh 2005; McDonald et al. 2005; Markstrom et al. 2008; Huntington 

and Niswonger 2012). 

Page 22208:

Options could include asserting jurisdiction over all waters connected through a shallow subsurface 

hydrologic connection or confined surface hydrologic connection regardless of

distance; asserting jurisdiction over adjacent waters only if they are located in the floodplain or riparian 

zone of a jurisdictional water; considering only confined surface connections but not shallow subsurface 

connections for purposes of determining adjacency; or establishing specific geographic limits for using 

shallow subsurface or confined surface hydrological connections as a basis for determining adjacency, 

including, for example, distance limitations based on ratios compared to the bank-to-bank width of the 

water to which the water is adjacent. The agencies note that under the proposed rule any waters not 

fitting within (a)(1) through (a)(6) categories would instead be treated as ‘‘other waters.’’ Options could 

include asserting jurisdiction over all waters connected through a shallow subsurface hydrologic 

connection or confined surface hydrologic connection regardless of distance; asserting jurisdiction over 

adjacent waters only if they are located in the floodplain or riparian zone of a jurisdictional water; 

considering only confined surface connections but not shallow subsurface connections for purposes of 

determining adjacency; or establishing specific geographic limits for using shallow subsurface or 

confined surface hydrological connections as a basis for determining adjacency, including, for example, 

distance limitations based on ratios compared to the bank-to-bank width of the water to

which the water is adjacent. The agencies note that under the proposed rule any waters not fitting within 

(a)(1) through (a)(6) categories would instead be treated as ‘‘other waters.’’ 

Regarding shallow subsurface connections, the U.S. Geological Survey (USGS) has published numerous 

reports and learning tools on ground water connectivity, including examples of flowpath frameworks 

expressed in block diagrams (Heath 1983, 1984; Winter et al. 1998), that contain flows through 

floodplains. Care should be taken not to imply that bedrock is impermeable because ground water flows 

through bedrock are important flowpaths that connect hydrologic landscapes over long distances and 

often across watershed boundaries (e.g., Roses et al. 1996). Future efforts to assert jurisdiction over all 

waters connected through a shallow subsurface hydrologic connection or confined surface hydrologic 

connection regardless of distance and to quantify connectivity can be informed by the wide variety of 

conceptual models and quantitative tools that have been developed to evaluate the connectivity of both 

surface and subsurface hydrological systems in different settings, including non-floodplain wetlands. 

The standard approach involves first characterizing the surface and subsurface elements of landscapes. 

Important elements include climate, geology, topographic relief, and the amount, distribution and types 

of waters and wetlands. These elements can then be integrated to create a flowpath network that 

describes connectivity (Heath 1983; ASTM 1996; Kolm et al. 1996; Winter et al. 1998). This approach 

has been extended to biological connectivity and hydrogeomorphic (HGM) wetland classifications (e.g., 

Kolm et al. 1998). Of course, the approach to quantifying hydrologic connectivity is not identical across 

systems, and careful attention must be given to identifying the most appropriate techniques (Healy et al. 

2007; Bracken et al. 2013) and metrics (Ali and Roy 2010). 

Other examples can be found in the literature related to water quantity and quality modeling (Appel and 

Reilly 1994; Sun et al. 1997; Harbaugh 2005; Parkhurst et al. 2010; Cunningham and Schalk 2011), and 

Kolm Comments Page 59
Individual comments from members of the SAB Panel for the Review of the EPA Water Body Connectivity Report. 

These comments do not represent consensus SAB advice or EPA policy.

integrated surface water ground water modeling (Markstrom et al. 2008; Ely and Kahle 2012; 

Huntington and Niswonger 2012; Woolfenden and Nishikawa 2014), sediment transport modeling 

(Nelson et al. 2003; McDonald et al. 2005), and watershed and biological/habitat/landscape modeling 

(Kinzel et al. 1999; Kinzel et al. 2005; Hunt et al. 2013). Approaches have also been developed to 

quantify linkages due to ground water movement and storage (Heath 1983) and the effects of “flood 

pulses” (Kolm et al. 1998). Likewise, the role of chemical movement and storage to ground water 

systems in floodplains has been quantified by flow and transport modeling (Winter et al. 1998; 

Markstrom et al. 2008; Woolfenden and Nishikawa 2014) as well as with steady-state and transient 

analyses that simulate temporal changes (Appel and Reilly 1994; Winter et al. 1998; Nelson et al. 2003; 

Conaway and Moran 2004; Harbaugh 2005; McDonald et al. 2005; Markstrom et al. 2008; Huntington 

and Niswonger 2012). 

Page 22208:

A shallow subsurface hydrologic connection is lateral water flow through a shallow subsurface layer, 

such as can be found, for example, in steeply sloping forested areas with shallow soils, or in soils with a 

restrictive layer that impedes the vertical flow of water, or in karst systems, specially karst pans. K.J. 

Devito, et al., ‘‘Groundwater-Surface Water Interactions in Headwater

Forested Wetlands of the Canadian Shield,’’ Journal of Hydrology 181:127–47 (1996); M.A.’Driscoll, 

and R.R. Parizek, ‘‘The Hydrologic Catchment Area of a Chain of Karst Wetlands in Central 

Pennsylvania, USA,’’ Wetlands 23:171–79 (2003); B.J. Cook, and F.R. Hauer, ‘‘Effects of Hydrologic 

Connectivity on Water Chemistry, Soils, and Vegetation Structure and Function in an Intermontane 

Depressional Wetland Landscape,’’ Wetlands 27:719– 38 (2007). A shallow subsurface connection also 

exists, for example, when the adjacent water and neighboring (a)(1) through (a)(5) water are in contact 

with the same shallow aquifer. Shallow subsurface connections may be found both within the ordinary 

root zone and below the ordinary root zone (below 12 inches), where other wetland delineation factors 

may not be present. A combination of physical factors may reflect the presence of a shallow subsurface 

connection, including (but not limited to) stream hydrograph (for example, when the hydrograph 

indicates an increase in flow in an area where no tributaries are entering the stream), soil surveys (for 

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

indicating the water table in the stream is lower than in the shallow subsurface.

Shallow subsurface connections are distinct from deeper groundwater connections, which do not satisfy 

the requirement for adjacency, in that the former exhibit a direct connection to the water found on the 

surface in wetlands and open waters. Water does not have to be continuously present in the confined 

surface or shallow subsurface hydrologic connection and the flow between the adjacent water and the 

jurisdictional water may move in one or both directions. While they may provide the connection 

establishing jurisdiction, these shallow subsurface flows are not ‘‘waters of the United States.’’ For 

waters outside of the riparian area or floodplain, confined surface hydrologic connections (as described 

above) are the only types of surface hydrologic connections that satisfy the requirements for adjacency. 

Waters outside of the riparian area or floodplain that lack a shallow subsurface hydrologic connection or 

a confined surface hydrologic connection would be analyzed as ‘‘other waters’’ under paragraph (a)(7) 

of the proposed rule.

Saturated zone groundwater and interflow must be clearly defined. This definition allows for both if 

SHALLOW. However, as indicated with the Karst references, deep groundwater should be included as 

Kolm Comments Page 60
Individual comments from members of the SAB Panel for the Review of the EPA Water Body Connectivity Report. 

These comments do not represent consensus SAB advice or EPA policy.

well for connectivity and include not only Karst, but certainly sedimentary systems, fractured rock 

systems, and volcanic systems as well. Many regional groundwater systems sustain the navigable 

waters and should be included. The real issue is both temporal and spatial as the SAB has clearly and 

thoroughly discussed. Also, magnitude issues need to be considered. 

The U.S. Geological Survey (USGS) has published numerous reports and learning tools on ground water 

connectivity, including examples of flowpath frameworks expressed in block diagrams (Heath 1983, 

1984; Winter et al. 1998), that contain flows through floodplains. Care should be taken not to imply that 

bedrock is impermeable because ground water flows through bedrock are important flowpaths that

connect hydrologic landscapes over long distances and often across watershed boundaries (e.g., Roses et 

al. 1996). 

There are methods for quantification regarding connectivity of these types of systems – both physical 

(fluids) and chemical (transport), and biological. Future efforts to assert jurisdiction over all waters 

connected through a shallow subsurface hydrologic connection or confined surface hydrologic 

connection regardless of distance and to quantify connectivity can be informed by the wide variety of 

conceptual models and quantitative tools that have been developed to evaluate the connectivity of both 

surface and subsurface hydrological systems in different settings, including non-floodplain wetlands. 

The standard approach involves first characterizing the surface and subsurface elements of landscapes. 

Important elements include climate, geology, topographic relief, and the amount, distribution and types 

of waters and wetlands. These elements can then be integrated to create a flowpath network that 

describes connectivity (Heath 1983; ASTM 1996; Kolm et al. 1996; Winter et al. 1998). This approach 

has been extended to biological connectivity and hydrogeomorphic (HGM) wetland classifications (e.g., 

Kolm et al. 1998). Of course, the approach to quantifying hydrologic connectivity is not identical across 

systems, and careful attention must be given to identifying the most appropriate techniques (Healy et al. 

2007; Bracken et al. 2013) and metrics (Ali and Roy 2010). 

Other examples can be found in the literature related to water quantity and quality modeling (Appel and 

Reilly 1994; Sun et al. 1997; Harbaugh 2005; Parkhurst et al. 2010; Cunningham and Schalk 2011), and 

integrated surface water ground water modeling (Markstrom et al. 2008; Ely and Kahle 2012; 

Huntington and Niswonger 2012; Woolfenden and Nishikawa 2014), sediment transport modeling 

(Nelson et al. 2003; McDonald et al. 2005), and watershed and biological/habitat/landscape modeling 

(Kinzel et al. 1999; Kinzel et al. 2005; Hunt et al. 2013). Approaches have also been developed to 

quantify linkages due to ground water movement and storage (Heath 1983) and the effects of “flood 

pulses” (Kolm et al. 1998). Likewise, the role of chemical movement and storage to ground water 

systems in floodplains has been quantified by flow and transport modeling (Winter et al. 1998; 

Markstrom et al. 2008; Woolfenden and Nishikawa 2014) as well as with steady-state and transient 

analyses that simulate temporal changes (Appel and Reilly 1994; Winter et al. 1998; Nelson et al. 2003; 

Conaway and Moran 2004; Harbaugh 2005; McDonald et al. 2005; Markstrom et al. 2008; Huntington 

and Niswonger 2012). 

Page 22209:

When determining whether a water is located in a floodplain, the agencies will use best professional 

judgment to determine which flood interval to use (for example, 10 to 20- year flood interval zone). The 

Kolm Comments Page 61
Individual comments from members of the SAB Panel for the Review of the EPA Water Body Connectivity Report. 

These comments do not represent consensus SAB advice or EPA policy.

agencies request comment on whether the rule text should provide greater specificity with regard to how 

the agencies will determine if a water is located in the

floodplain of a jurisdictional water.

Besides the 10 to 20- year flood interval, the major connectivity could be shallow groundwater, which 

may be ongoing. The flood plain can be defined geomorphically and hydrologically, via groundwater 

connection. If there is a “permanent” or even seasonal water table that connects the floodplain waters to 

the surface waters in the channels, the concept of actual flood frequency is a moot point. If the water 

table exists naturally for some part of the year, the systems are connected.

Page 22209:

The agencies intend to similarly interpret the new definition of ‘‘neighboring.’’ This new definition is 

designed to provide greater clarity by identifying specific areas and characteristics for jurisdictional 

adjacent waters, but the agency’s request comment for additional clarification. Commenters should 

support where possible from scientific literature any suggestions for additional clarification of current 

explicit limits on adjacency, such as a specific distance or a specific floodplain interval. The agencies 

seek comment on specific options for establishing additional precision in the definition of 

‘‘neighboring’’ through: explicit language in the definition that waters connected by shallow subsurface 

hydrologic or confined surface hydrologic connections to an (a)(1) through (a)(5) water must be 

geographically proximate to the adjacent water; circumstances under which waters outside the 

floodplain or riparian zone are jurisdictional if they are reasonably proximate; support for or against 

placing geographic limits on what waters outside the floodplain or riparian zone are jurisdictional; 

determining that only waters within the floodplain, only waters within the riparian area, or only waters 

within the

floodplain and riparian area (but not waters outside these areas with a shallow subsurface or confined 

surface hydrologic connection) are adjacent; identification of particular floodplain intervals within 

which waters would be considered adjacent; and any other scientifically valid criteria, guidelines or 

parameters that would increase clarity with respect to neighboring waters.

The basis should also include groundwater connectivity which may not need a frequency basis. There 

are methods for quantification regarding connectivity of these types of systems – both physical (fluids) 

and chemical (transport), and biological. Future efforts to assert jurisdiction over all waters connected 

through a shallow subsurface hydrologic connection or confined surface hydrologic connection 

regardless of distance and to quantify connectivity can be informed by the wide variety of conceptual 

models and quantitative tools that have been developed to evaluate the connectivity of both surface and 

subsurface hydrological systems in different settings, including non-floodplain wetlands. The standard 

approach involves first characterizing the surface and subsurface elements of landscapes. Important 

elements include climate, geology, topographic relief, and the amount, distribution and types of waters 

and wetlands. These elements can then be integrated to create a flowpath network that describes 

connectivity (Heath 1983; ASTM 1996; Kolm et al. 1996; Winter et al. 1998). This approach has been 

extended to biological connectivity and hydrogeomorphic (HGM) wetland classifications (e.g., Kolm et 

al. 1998). Of course, the approach to quantifying hydrologic connectivity is not identical across 

systems, and careful attention must be given to identifying the most appropriate techniques (Healy et al. 

2007; Bracken et al. 2013) and metrics (Ali and Roy 2010). 

Kolm Comments Page 62
Individual comments from members of the SAB Panel for the Review of the EPA Water Body Connectivity Report. 

These comments do not represent consensus SAB advice or EPA policy.

Other examples can be found in the literature related to water quantity and quality modeling (Appel and 

Reilly 1994; Sun et al. 1997; Harbaugh 2005; Parkhurst et al. 2010; Cunningham and Schalk 2011), and 

integrated surface water ground water modeling (Markstrom et al. 2008; Ely and Kahle 2012; 

Huntington and Niswonger 2012; Woolfenden and Nishikawa 2014), sediment transport modeling 

(Nelson et al. 2003; McDonald et al. 2005), and watershed and biological/habitat/landscape modeling 

(Kinzel et al. 1999; Kinzel et al. 2005; Hunt et al. 2013). Approaches have also been developed to 

quantify linkages due to ground water movement and storage (Heath 1983) and the effects of “flood 

pulses” (Kolm et al. 1998). Likewise, the role of chemical movement and storage to ground water 

systems in floodplains has been quantified by flow and transport modeling (Winter et al. 1998; 

Markstrom et al. 2008; Woolfenden and Nishikawa 2014) as well as with steady-state and transient 

analyses that simulate temporal changes (Appel and Reilly 1994; Winter et al. 1998; Nelson et al. 2003; 

Conaway and Moran 2004; Harbaugh 2005; McDonald et al. 2005; Markstrom et al. 2008; Huntington 

and Niswonger 2012). 

3. The proposed rule has defined Waters of the U.S. under the jurisdiction of the Clean Water Act to mean, 

on a case-specific basis, other waters including wetlands, provided that those waters alone, or in combination 

with other similarly situated waters, including wetlands, located in the same region, have a significant nexus 

to a traditional navigable water, interstate water, or the territorial seas. Please comment on the adequacy of 

the scientific and technical basis of this proposed definition. (lead discussants are: Drs. Emily Bernhardt and 

Michael Gooseff) 

Page 22211:

For purposes of analyzing whether an ‘‘other water’’ has a significant nexus, the agencies are proposing 

that ‘‘other waters’’ are similarly situated if they perform similar functions and they are either (1) 

located sufficiently close together so that they can be evaluated as a single landscape unit with regard to 

their effect on the chemical, physical, or biological integrity of a water identified in paragraphs (a)(1) 

through (a)(3), or (2) located sufficiently close to a ‘‘water of the United States’’ for such an evaluation 

of their effect. These criteria are explained in a subsequent section. Consistent with Justice Kennedy’s 

opinion in Rapanos, the agencies propose today and are soliciting comment on establishing a casespecific analysis of whether ‘‘other waters,’’ including wetlands, that do not meet the criteria for any of 

the proposed jurisdictional categories in (a)(1) through (a)(6) and are not proposed to be excluded by 

rule under section (b),

are susceptible to a case-specific analysis of whether they alone, or in combination with other similarly 

situated waters, have a significant nexus to a traditional navigable water, an interstate water, or the 

territorial seas, and therefore are ‘‘waters of the United States.’’

This Rule is still reliant on distance and needs to be flow path oriented with spatial and temporal 

components! To clarify the connectivity of “other waters” to “waters of the US”, the SAB recommends 

that a conceptual framework be established expressed as continuous hydrological (surface and 

subsurface), chemical, and biological flowpaths connecting watersheds from top to bottom, and 

therefore connecting other waters and wetlands to downgradient waters. The flowpath framework should 

highlight the four-dimensional nature of connectivity, because four-dimensional connectivity scaled in a 

habitat-to-catchment context is a foundational aspect of freshwater ecology (e.g., Ward 1989). The flux 

and transformation of water, materials, and organisms – which fundamentally control the integrity of

downgradient freshwater ecosystems – occur at varying rates primarily determined by climate, geology, 

topographic relief, and biology and are expressed in terms of surface water and ground water storage 

Kolm Comments Page 63
Individual comments from members of the SAB Panel for the Review of the EPA Water Body Connectivity Report. 

These comments do not represent consensus SAB advice or EPA policy.

and flow through the landscape (e.g., uplands, wetlands, lakes, rivers, and floodplains). Therefore, these 

flowpaths are inherently four-dimensional (i.e., longitudinal, lateral, vertical, and through time). 

Page 22212:

The agencies also request comment and information below on how the science could support other 

approaches that could provide greater regulatory certainty regarding the jurisdictional status of ‘‘other 

waters’’

There are methods for quantification regarding connectivity of these types of systems specifically the 

“other waters” – both physical (fluids) and chemical (transport), and biological. Future efforts to assert 

jurisdiction over “other” waters connected through a shallow subsurface hydrologic connection or 

confined surface hydrologic connection regardless of distance and to quantify connectivity can be 

informed by the wide variety of conceptual models and quantitative tools that have been developed to 

evaluate the connectivity of both surface and subsurface hydrological systems in different settings, 

including non-floodplain wetlands. The standard approach involves first characterizing the surface and 

subsurface elements of landscapes. Important elements include climate, geology, topographic relief, and 

the amount, distribution and types of waters and wetlands. These elements can then be integrated to 

create a flowpath network that describes connectivity (Heath 1983; ASTM 1996; Kolm et al. 1996; 

Winter et al. 1998). This approach has been extended to biological connectivity and hydrogeomorphic 

(HGM) wetland classifications (e.g., Kolm et al. 1998). Of course, the approach to quantifying 

hydrologic connectivity is not identical across systems, and careful attention must be given to 

identifying the most appropriate techniques (Healy et al. 2007; Bracken et al. 2013) and metrics (Ali and 

Roy 2010). 

Other examples can be found in the literature related to water quantity and quality modeling (Appel and 

Reilly 1994; Sun et al. 1997; Harbaugh 2005; Parkhurst et al. 2010; Cunningham and Schalk 2011), and 

integrated surface water ground water modeling (Markstrom et al. 2008; Ely and Kahle 2012; 

Huntington and Niswonger 2012; Woolfenden and Nishikawa 2014), sediment transport modeling 

(Nelson et al. 2003; McDonald et al. 2005), and watershed and biological/habitat/landscape modeling 

(Kinzel et al. 1999; Kinzel et al. 2005; Hunt et al. 2013). Approaches have also been developed to 

quantify linkages due to ground water movement and storage (Heath 1983) and the effects of “flood 

pulses” (Kolm et al. 1998). Likewise, the role of chemical movement and storage to ground water 

systems in floodplains has been quantified by flow and transport modeling (Winter et al. 1998; 

Markstrom et al. 2008; Woolfenden and Nishikawa 2014) as well as with steady-state and transient 

analyses that simulate temporal changes (Appel and Reilly 1994; Winter et al. 1998; Nelson et al. 2003; 

Conaway and Moran 2004; Harbaugh 2005; McDonald et al. 2005; Markstrom et al. 2008; Huntington 

and Niswonger 2012). 

Page 22212: 

Water sheds are used solely, the effects of regional groundwater systems or basins is ignored! Connectivity 

via regional groundwater systems needs to be considered! In general, the role of regional groundwater 

systems in neighboring systems is not addressed by this Rule and leaves the waters of the US vulnerable.

The Rule focuses primarily on the site and subregional scales, and on watershed boundaries. This tends 

to either ignore or at least downplay the potential significance of regional-scale hydrologic connectivity, 

Kolm Comments Page 64
Individual comments from members of the SAB Panel for the Review of the EPA Water Body Connectivity Report. 

These comments do not represent consensus SAB advice or EPA policy.

especially as it relates to ground water in adjacent and /or neighboring systems. This is a problem 

because regional ground water flows commonly interact with the surface environment at sinks and 

springs. For example, the Floridan aquifer underlies all of Florida as well as portions of Mississippi, 

Alabama, Georgia, and South Carolina and commonly interacts with the surface environment through 

sinks, springs, and outcrops (see Sun et al. 1997 and references therein). To provide a better 

understanding of ground water connectivity, and the way that ground water connectivity might vary 

spatially, the SAB recommends that the EPA also consider using the ASTM D5979-96 Standard Guide 

for Conceptualization and Characterization of Ground Water Systems (ASTM 1996; Kolm et al. 1996). 

To better characterize regional-scale ground water connectivity, the SAB recommends that the EPA also 

consider using findings from the U.S. Geological Survey Regional Aquifer Systems Analysis (RASA) 

Program. An understanding of regional ground water flow systems is critical to the understanding of 

four-dimensional hydrologic connectivity on both the local and regional scales. Understanding ground 

water flow in unique hydrogeologic settings, including the Floridan aquifer system (karst systems), the 

High Plains aquifer system (semi-arid systems), and the Snake River Plain and Rio Grande Rift aquifer 

systems (volcanic bedrock systems), is especially important. These and other unique hydrogeological 

settings are covered by the RASA Program (Sun et al. 1997). 

To clarify the connectivity of other waters to “waters of the US”, the SAB recommends that a 

conceptual framework be established expressed as continuous hydrological (surface and subsurface), 

chemical, and biological flowpaths connecting watersheds from top to bottom, and therefore connecting 

waters and wetlands to downgradient waters. The flowpath framework should highlight the fourdimensional nature of connectivity, because four-dimensional connectivity scaled in a habitat-tocatchment context is a foundational aspect of freshwater ecology (e.g., Ward 1989). The flux and 

transformation of water, materials, and organisms – which fundamentally control the integrity of 

downgradient freshwater ecosystems – occur at varying rates primarily determined by climate, geology, 

topographic relief, and biology and are expressed in terms of surface water and ground water storage 

and flow through the landscape (e.g., uplands, wetlands, lakes, rivers, and floodplains). Therefore, these 

flowpaths are inherently four-dimensional (i.e., longitudinal, lateral, vertical, and through time).

Ground water connectivity, in particular, could be better represented in the Rule. The U.S. Geological 

Survey (USGS) has published numerous reports and learning tools on ground water connectivity, 

including examples of flowpath frameworks expressed in block diagrams (Heath 1983, 1984; Winter et 

al. 1998), that contain flows through floodplains. Care should be taken not to imply that bedrock is 

impermeable because ground water flows through bedrock are important flowpaths that connect 

hydrologic landscapes over long distances and often across watershed boundaries (e.g., Roses et al. 

1996). 

Page 22213:

In determining whether other waters are sufficiently close to each other or to a water of the United 

States, the agencies would also consider hydrologic connectivity to each other or

a jurisdictional water. 

In determining whether groups of other waters perform ‘‘similar functions’’ the agencies would also 

consider functions such as habitat, water storage, sediment retention, and pollution sequestration. These 

Kolm Comments Page 65
Individual comments from members of the SAB Panel for the Review of the EPA Water Body Connectivity Report. 

These comments do not represent consensus SAB advice or EPA policy.

and other relevant considerations would be used by the agencies to document the hydrologic, 

geomorphic and ecological characteristics and circumstances of the water.

The agencies solicit comment regarding this approach to ‘‘other waters,’’ recognizing that a casespecific analysis of significant nexus is resource intensive for the regulating agencies and the regulated 

community alike. In addition, the agencies solicit comment on additional scientific research and data 

that might further inform decisions about ‘‘other waters.’’ In particular the agencies solicit information 

about whether current scientific research and data regarding particular types of waters are sufficient to 

support the inclusion of subcategories of types of ‘‘other waters,’’ either alone or in combination with 

similarly situated waters, that can appropriately be identified as always lacking or always having a 

significant nexus.

The agencies acknowledge that there may be more than one way to determine which waters are 

jurisdictional as ‘‘other waters.’’ This proposal is for a case-specific analysis of whether ‘‘other

waters,’’ including wetlands, alone, or in combination with other similarly situated waters located in the 

same region, have a significant nexus to a traditional navigable water, interstate water, or the territorial 

seas. The agencies make this proposal based on an analysis of the current state of the science available 

to them. In this proposal, the agencies continue to solicit additional science (peer-reviewed whenever 

possible) that could lead to greater clarity, certainty, and predictability of which waters are and are not 

within the jurisdiction of the CWA.

There are methods for quantification regarding connectivity of these types of systems specifically the 

“other waters” – both physical (fluids) and chemical (transport), and biological. Future efforts to assert 

jurisdiction over “other” waters connected through a shallow subsurface hydrologic connection or 

confined surface hydrologic connection regardless of distance and to quantify connectivity can be 

informed by the wide variety of conceptual models and quantitative tools that have been developed to 

evaluate the connectivity of both surface and subsurface hydrological systems in different settings, 

including non-floodplain wetlands. The standard approach involves first characterizing the surface and 

subsurface elements of landscapes. Important elements include climate, geology, topographic relief, and 

the amount, distribution and types of waters and wetlands. These elements can then be integrated to 

create a flowpath network that describes connectivity (Heath 1983; ASTM 1996; Kolm et al. 1996; 

Winter et al. 1998). This approach has been extended to biological connectivity and hydrogeomorphic 

(HGM) wetland classifications (e.g., Kolm et al. 1998). Of course, the approach to quantifying 

hydrologic connectivity is not identical across systems, and careful attention must be given to 

identifying the most appropriate techniques (Healy et al. 2007; Bracken et al. 2013) and metrics (Ali and 

Roy 2010). 

Other examples can be found in the literature related to water quantity and quality modeling (Appel and 

Reilly 1994; Sun et al. 1997; Harbaugh 2005; Parkhurst et al. 2010; Cunningham and Schalk 2011), and 

integrated surface water ground water modeling (Markstrom et al. 2008; Ely and Kahle 2012; 

Huntington and Niswonger 2012; Woolfenden and Nishikawa 2014), sediment transport modeling 

(Nelson et al. 2003; McDonald et al. 2005), and watershed and biological/habitat/landscape modeling 

(Kinzel et al. 1999; Kinzel et al. 2005; Hunt et al. 2013). Approaches have also been developed to 

quantify linkages due to ground water movement and storage (Heath 1983) and the effects of “flood 

pulses” (Kolm et al. 1998). Likewise, the role of chemical movement and storage to ground water 

systems in floodplains has been quantified by flow and transport modeling (Winter et al. 1998; 

Kolm Comments Page 66
Individual comments from members of the SAB Panel for the Review of the EPA Water Body Connectivity Report. 

These comments do not represent consensus SAB advice or EPA policy.

Markstrom et al. 2008; Woolfenden and Nishikawa 2014) as well as with steady-state and transient 

analyses that simulate temporal changes (Appel and Reilly 1994; Winter et al. 1998; Nelson et al. 2003; 

Conaway and Moran 2004; Harbaugh 2005; McDonald et al. 2005; Markstrom et al. 2008; Huntington 

and Niswonger 2012). 

Page 22215:

Ecoregion discussion: 

In general, the role of regional groundwater systems is important for the Ecoregion discussion and 

approaches particularly for the potential significance of regional-scale hydrologic connectivity, 

especially as it relates to ground water in adjacent and /or neighboring systems. Regional ground water 

flows commonly interact with the surface environment at sinks and springs and control many of the 

ecoregion -scale structures and functions. For example, the Floridan aquifer underlies all of Florida as 

well as portions of Mississippi, Alabama, Georgia, and South Carolina and commonly interacts with the 

surface environment through sinks, springs, and outcrops (see Sun et al. 1997 and references therein). 

To provide a better understanding of ground water connectivity, and the way that ground water 

connectivity might vary spatially, the SAB recommends that the EPA also consider using the ASTM 

D5979-96 Standard Guide for Conceptualization and Characterization of Ground Water Systems

(ASTM 1996; Kolm et al. 1996). To better characterize regional-scale ground water connectivity and 

ecoregion analysis, the SAB recommends that the EPA also consider using findings from the U.S. 

Geological Survey Regional Aquifer Systems Analysis (RASA) Program. An understanding of regional 

ground water flow systems is critical to the understanding of four-dimensional hydrologic connectivity 

on both the local and regional scales. Understanding ground water flow in unique hydrogeologic 

settings, including the Floridian aquifer system (karst systems), the High Plains aquifer system (semiarid systems), and the Snake River Plain and Rio Grande Rift aquifer systems (volcanic bedrock 

systems), is especially important. These and other unique hydrogeological settings are covered by the 

RASA Program (Sun et al. 1997). 

Page 22216:

The factors the agencies used in developing the list above are: 

a. Density of ‘‘other waters’’ such that there can be periodic surface hydrologic connections among the 

waters, for example in West Coast vernal pools.

b. Soil permeability and surface or shallow subsurface flow such that the ‘‘other waters’’ can be 

considered hydrologically connected, such as many Texas coastal prairie wetlands.

c. Water chemistry which indicates that the ‘‘other waters’’ are part of the same system and influenced 

by the same processes.

d. Physical capacity of ‘‘other waters’’ to provide flood and sediment retention; this is a case where 

several small wetlands together may have a different effect than a single large wetland providing the 

same function, for example prairie potholes in the Missouri Coteau.

e. Co-location of waters to each other or similarly to the tributary system such that their cumulative and 

additive effects on pollutant removal through parallel, serial, or sequential processing are apparent, such 

as the role of pocosins in maintaining water quality in estuaries.

Kolm Comments Page 67
Individual comments from members of the SAB Panel for the Review of the EPA Water Body Connectivity Report. 

These comments do not represent consensus SAB advice or EPA policy.

f. ‘‘Other waters’’ that are sufficiently near each other or the tributary system and thus function as an 

integrated habitat that can support the life cycle of a species or more broadly provide habitat to a large 

number of a single species.

The agencies request comment on the factors above and whether this list of factors is appropriate, and 

whether there are other factors that should be included or excluded from this list. Comments should 

address the science that supports each comment.

Factors restated from above:

There are methods for quantification regarding connectivity of these types of systems specifically the 

“other waters” – both physical (fluids) and chemical (transport), and biological. Future efforts to assert 

jurisdiction over “other” waters connected through a shallow subsurface hydrologic connection or 

confined surface hydrologic connection regardless of distance and to quantify connectivity can be 

informed by the wide variety of conceptual models and quantitative tools that have been developed to 

evaluate the connectivity of both surface and subsurface hydrological systems in different settings, 

including non-floodplain wetlands. The standard approach involves first characterizing the surface and 

subsurface elements of landscapes. Important elements include climate, geology, topographic relief, and 

the amount, distribution and types of waters and wetlands. These elements can then be integrated to 

create a flowpath network that describes connectivity (Heath 1983; ASTM 1996; Kolm et al. 1996; 

Winter et al. 1998). This approach has been extended to biological connectivity and hydrogeomorphic 

(HGM) wetland classifications (e.g., Kolm et al. 1998). Of course, the approach to quantifying 

hydrologic connectivity is not identical across systems, and careful attention must be given to 

identifying the most appropriate techniques (Healy et al. 2007; Bracken et al. 2013) and metrics (Ali and 

Roy 2010). 

Other examples can be found in the literature related to water quantity and quality modeling (Appel and 

Reilly 1994; Sun et al. 1997; Harbaugh 2005; Parkhurst et al. 2010; Cunningham and Schalk 2011), and 

integrated surface water ground water modeling (Markstrom et al. 2008; Ely and Kahle 2012; 

Huntington and Niswonger 2012; Woolfenden and Nishikawa 2014), sediment transport modeling 

(Nelson et al. 2003; McDonald et al. 2005), and watershed and biological/habitat/landscape modeling 

(Kinzel et al. 1999; Kinzel et al. 2005; Hunt et al. 2013). Approaches have also been developed to 

quantify linkages due to ground water movement and storage (Heath 1983) and the effects of “flood 

pulses” (Kolm et al. 1998). Likewise, the role of chemical movement and storage to ground water 

systems in floodplains has been quantified by flow and transport modeling (Winter et al. 1998; 

Markstrom et al. 2008; Woolfenden and Nishikawa 2014) as well as with steady-state and transient 

analyses that simulate temporal changes (Appel and Reilly 1994; Winter et al. 1998; Nelson et al. 2003; 

Conaway and Moran 2004; Harbaugh 2005; McDonald et al. 2005; Markstrom et al. 2008; Huntington 

and Niswonger 2012). 

Page 22216:

Discussion of Hydrologic-Landscape Regions. Then: 

The agencies seek comment on the technical bases for using ecoregions and hydrologic-landscape 

regions under this option. Commenters may also address whether some other method or combination of 

Kolm Comments Page 68
Individual comments from members of the SAB Panel for the Review of the EPA Water Body Connectivity Report. 

These comments do not represent consensus SAB advice or EPA policy.

methods (certain ecoregions and hydrologic-landscape regions, for example) of mapping geographic 

boundaries is better supported by the science. Comments should also address whether and how this 

option is consistent with the science and the caselaw.

Using Hydrologic-Landscape Regions and Ecoregions as a basis for determining the connectivity of 

hydrologic and biologic systems to “waters of the U.S.” is an excellent first step in understanding the 

holistic nature of these systems in any location when combined with the standard approach that involves 

characterizing the surface and subsurface elements of landscapes to determine flowpath networks at 

multiple temporal and spatial scales. Important elements include climate, geology, topographic relief, 

and the amount, distribution and types of waters and wetlands. These elements, in context with the 

HLRs and Ecoregions, can then be integrated to create a flowpath network that describes connectivity 

(Heath 1983; ASTM 1996; Kolm et al. 1996; Winter et al. 1998). This approach has been extended to 

biological connectivity and hydrogeomorphic (HGM) wetland classifications (e.g., Kolm et al. 1998).

Page 22217:

3. Additional ‘‘other waters’’ approaches. The agencies request comment on additional ‘‘other waters’’ 

approaches considered, but not proposed by the agencies.

Restated and note references: Using Hydrologic-Landscape Regions and Ecoregions as a basis for 

determining the connectivity of hydrologic and biologic systems to “waters of the U.S.” is an excellent 

first step in understanding the holistic nature of these systems in any location when combined with the 

standard approach that involves characterizing the surface and subsurface elements of landscapes to 

determine flowpath networks at multiple temporal and spatial scales. Important elements include 

climate, geology, topographic relief, and the amount, distribution and types of waters and wetlands.

These elements, in context with the HLRs and Ecoregions, can then be integrated to create a flowpath 

network that describes connectivity (Heath 1983; ASTM 1996; Kolm et al. 1996; Winter et al. 1998). 

This approach has been extended to biological connectivity and hydrogeomorphic (HGM) wetland 

classifications (e.g., Kolm et al. 1998).

4. The proposed rule defines other terms and excludes specified waters and features from the definition of 

Waters of the U.S. Please comment on the adequacy of the scientific and technical basis of the other 

definitions and exclusions. (lead discussants are: Drs. David Allan and Mark Rains) 

Page 22203:

The agencies specifically seek comment on the appropriate flow regime for a ditch excavated wholly in 

uplands and draining only uplands to be included in the exclusion of paragraph (b)(3). In particular, the 

agencies seek comment on whether the flow regime in such ditches should be less than intermittent flow 

or whether the flow regime in such ditches should be less than perennial flow as proposed.

Waters and wetlands are "connected" in the sense that they are integrated into the broader hydrological 

landscape and therefore can play important roles in maintaining the chemical, physical, and biological 

integrity of downgradient waters. They perform a variety of functions (which are broadly classified in 

the Report as source, sink, lag, transformation, and refuge functions) at rates that are a characteristic of 

where these waters and wetlands are located on the gradient of connectivity. Therefore, downgradient 

Kolm Comments Page 69
Individual comments from members of the SAB Panel for the Review of the EPA Water Body Connectivity Report. 

These comments do not represent consensus SAB advice or EPA policy.

waters might suffer consequences if the degree of connectivity is altered by human activities. Alterations 

can be of three types: some can directly decrease connectivity, such as dams (Ward and Stanford 1983) 

and ground water pumping that lowers local water tables and causes surface-water connections to cease 

(Haag and Pfeiffer 2012); some can directly increase connectivity, such as ditches (Min et al. 2010) and 

tile drains (Randall et al. 1997); and some can indirectly change the frequency, magnitude, timing, 

duration, and/or rate of change of connectivity, such as impervious surfaces in the contributing 

watershed (Walsh et al. 2012). Each of these types of human alterations affect connectivity and therefore 

can impact the chemical, physical, and biological integrity of the downgradient waters. 

As surface water features, ditches and canals function as either perennial or intermittent streams or 

tributaries and should be legally treated as such. Regardless of source, these ditches convey or store 

water and chemical/physical/biological sediment and materials spatially on a temporal basis (rate, 

magnitude, and frequency). 

The water from ditches can leak to provide groundwater recharge to the sediments or bedrock beneath 

the ditch, or accumulate groundwater discharge in its flow (serve as a drain) or both. These functions 

can be temporal (seasonal) and spatial. In all, the ditch impacts many of the hydrologic systems in the 

vicinity of its location, and is connected. 

Land use and water rights changes affect the function of the ditch and can be critical to the “waters of 

the US”. In the western US, land use changes are mostly from agriculture to urbanization, and the 

ditches are frequently “shut off” as water is passed downstream to thirsty cities, and local aquifers “dry 

up” since irrigation and ditch leakance is reduced. This, in turn, affects the local tributaries and springs, 

many of which had water rights partitioned during the agricultural times. 

Page 22218:

The following features are exempt:

Artificially irrigated areas that would revert to upland should application of irrigation water to that area 

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, including groundwater drained through subsurface drainage systems; and

Gullies and rills and non-wetland swales.

In no cases should groundwater that is shown to be connected to “waters of the US” be exempt (see 

comments above). Each of these features listed may be connected to “waters of the US” depending on 

the hydrogeologic framework that is underneath the features, and the hydrologic system that the features 

are constructed within. Artificial lakes or ponds, or reflection pools, etc., created by excavation, diking, 

or construction may be directly connected to the “waters of the US” by shallow or deeper groundwater, 

therefore, a “blanket” exemption is not recommended. Each feature should be cleared by a systematic 

Kolm Comments Page 70
Individual comments from members of the SAB Panel for the Review of the EPA Water Body Connectivity Report. 

These comments do not represent consensus SAB advice or EPA policy.

hydrologic system analysis. These exemptions may invite multiple abuses to the Rule, particularly 

when land ownership and land use are changed with time. 

Page 22220:

The agencies request comment on how they could provide greater clarity on how to distinguish between 

erosional features such as gullies, which are excluded from jurisdiction, and ephemeral tributaries, 

which are categorically jurisdictional.

A gully that has been allowed to become permanent and minimally ephemeral, such as gullies observed 

throughout the Western US caused by over grazing of livestock, should be in the jurisdiction of the 

waters of the US. The landowner should have a specified amount of time to correct the situation, or the 

conversion is permanent. 

The agencies request comment on how they could provide greater clarity on how to distinguish swales, 

which are excluded from jurisdiction, and ephemeral tributaries, which are categorically jurisdictional.

A distinction between natural and human-made swales is necessary, and the functions of the swales 

should be determined on a case by case basis regarding the effects on the chemical, physical, and 

biological aspects of the system. 

The agencies request comment on this formulation of the ditch exclusion. The agencies specifically seek 

comment on the appropriate flow regime for a ditch excavated wholly in uplands and draining only 

uplands to be covered by the exclusion in paragraph (b)(3). In particular, the agencies seek comment on 

whether the flow regime in such ditches should be less than intermittent flow or whether the flow regime 

in such ditches should be less than perennial flow as proposed.

Constructed ditches change the hydrologic flow paths of local and subregional hydrologic systems. 

Ditches are perennial, intermittent, or ephemeral water conveyors, and should be regulated as such. See 

discussion above on changing land use and ground water recharge that flows to jurisdiction waters, 

which is an issue in the Western US. A classic example is the gutters on houses in the Western US –

water can be harmlessly deflected off the houses as long as the runoff is allowed to reach the streams via 

drains, sewers, etc. If individuals collect the runoff and water their gardens, it is a direct violation of 

water law (Milagro Bean Field War). However, our laws do not cover the increase of impermeable 

structures that prevent groundwater recharge where our houses are built. 

5. If you have any other comments about the adequacy of the scientific and technical basis of the proposed 

rule, please provide them as well. 

To restate, there is a tremendous understatement of the role of groundwater in connectivity particularly in the 

adjacent water bodies and other waters sections of the Rule, and the exemptions of the Rule; this leaves the 

waters of the US vulnerable. The Rule focuses primarily on the site and subregional scales, perhaps due 

to the legal aspects. This tends to either ignore or at least downplay the potential significance of 

regional-scale hydrologic connectivity, especially as it relates to ground water. This is a problem 

because regional ground water flows commonly interact with the surface environment at sinks and 

springs. For example, the Floridan aquifer underlies all of Florida as well as portions of Mississippi, 

Alabama, Georgia, and South Carolina and commonly interacts with the surface environment through 

Kolm Comments Page 71
Individual comments from members of the SAB Panel for the Review of the EPA Water Body Connectivity Report. 

These comments do not represent consensus SAB advice or EPA policy.

sinks, springs, and outcrops (see Sun et al. 1997 and references therein). To provide a better 

understanding of ground water connectivity, and the way that ground water connectivity might vary 

spatially, the SAB recommends that the EPA also consider using the ASTM D5979-96 Standard Guide 

for Conceptualization and Characterization of Ground Water Systems (ASTM 1996; Kolm et al. 1996). 

EPA’s Proposed Rule 

The following sections of the proposed rule may be most relevant for your review: 

Preamble (explains the basis and purpose for the proposed rule) 

The agencies acknowledge that there may be more than one way to determine which waters are 

jurisdictional as ‘‘other waters.’’ To best meet their goals and responsibilities, the agencies request 

comment on alternate approaches to determining whether ‘‘other waters’’ are similarly situated and have 

a ‘‘significant nexus’’ to a traditional navigable water, interstate water, or the territorial seas. In the 

discussion of ‘‘other waters’’ later in the preamble, the agencies seek comment on these other 

approaches and whether they could better meet the goals of greater predictability and consistency 

through increased clarity, while simultaneously fulfilling the agencies’ responsibility to the CWA’s 

objectives and policies to protect water quality, public health, and the environment.

Commenters will specifically be asked to comment on whether and how these alternate approaches may 

be more consistent with the goal of clarity, and the CWA, the best available science, and the case law. In 

particular, the agencies are interested in comments, scientific and technical data, case law, and other 

information that would further clarify which ‘‘other waters’’ should be considered similarly situated for 

purposes of a case-specific significant nexus determination. The agencies seek comment on a number of 

alternative approaches. These alternatives include potentially determining waters in identified ecological 

regions (ecoregions) or hydrologic-landscape regions are similarly situated for purposes of evaluating a 

significant nexus, as well as the basis for determining which ecoregions or hydrologic-landscape regions 

should be so identified.

Restated from above and note references: Using Hydrologic-Landscape Regions and Ecoregions as a 

basis for determining the connectivity of hydrologic and biologic systems to “waters of the U.S.” is an 

excellent first step in understanding the holistic nature of these systems in any location when combined 

with the standard approach that involves characterizing the surface and subsurface elements of 

landscapes to determine flowpath networks at multiple temporal and spatial scales. Important elements 

include climate, geology, topographic relief, and the amount, distribution and types of waters and 

wetlands. These elements, in context with the HLRs and Ecoregions, can then be integrated to create a 

flowpath network that describes connectivity (Heath 1983; ASTM 1996; Kolm et al. 1996; Winter et al. 

1998). This approach has been extended to biological connectivity and hydrogeomorphic (HGM) 

wetland classifications (e.g., Kolm et al. 1998).

II. Background -- Page 22190

A. Executive Summary -- Page 22190

Page 22193: 

Kolm Comments Page 72
Individual comments from members of the SAB Panel for the Review of the EPA Water Body Connectivity Report. 

These comments do not represent consensus SAB advice or EPA policy.

Under the proposed first section of the regulation, section (a), the agencies propose to define the ‘‘waters 

of the United States’’ for all sections (including sections 301, 311, 401, 402, 404) of the CWA to mean: 

• All waters which are currently used, were used in the past, or may be susceptible to use in interstate or 

foreign commerce, including all waters which are subject to the ebb and flow of the tide;

• All interstate waters, including interstate wetlands;

• The territorial seas;

• All impoundments of a traditional navigable water, interstate water, the territorial seas or a tributary;

• All tributaries of a traditional navigable water, interstate water, the territorial seas or impoundment;

• All waters, including wetlands, adjacent to a traditional navigable water, interstate water, the territorial 

seas, impoundment or tributary; and

• On a case-specific basis, other waters, including wetlands, provided that those waters alone, or in 

combination with other similarly situated waters, including wetlands, located in the same region, have a 

significant nexus to a traditional navigable water, interstate water or the territorial seas.

Nexus definition is weak on groundwater connectivity. Please see comments in previous sections. To 

restate, there is a tremendous understatement of the role of groundwater in connectivity particularly in the 

adjacent water bodies and other waters sections of the Rule, and the exemptions of the Rule; this leaves the 

waters of the US vulnerable. The Rule focuses primarily on the site and subregional scales, perhaps due 

to the legal aspects. This tends to either ignore or at least downplay the potential significance of 

regional-scale hydrologic connectivity, especially as it relates to ground water. This is a problem 

because regional ground water flows commonly interact with the surface environment at sinks and 

springs. For example, the Floridan aquifer underlies all of Florida as well as portions of Mississippi, 

Alabama, Georgia, and South Carolina and commonly interacts with the surface environment through 

sinks, springs, and outcrops (see Sun et al. 1997 and references therein). To provide a better 

understanding of ground water connectivity, and the way that ground water connectivity might vary 

spatially, the SAB recommends that the EPA also consider using the ASTM D5979-96 Standard Guide 

for Conceptualization and Characterization of Ground Water Systems (ASTM 1996; Kolm et al. 1996). 

Page 22194:

The proposed section (b) excludes specified waters and features from the definition of ‘‘waters of the 

United States.’’ Waters and features that are determined to be excluded under section (b) of the 

proposed rule will not be jurisdictional under any of the categories in the proposed rule under section 

(a), even if they would otherwise satisfy the regulatory definition. Those waters and features that would 

not be ‘‘waters of the United States’’ are:..... groundwater including groundwater drained through 

subsurface drainage systems; and...

See comments in text above. In no cases should groundwater that is shown to be connected to “waters 

of the US” be exempt (see comments above). Each of the features listed in (b) may be connected to 

“waters of the US” depending on the hydrogeologic framework that is underneath the features, and the 

hydrologic system that the features are constructed within. Artificial lakes or ponds, or reflection pools, 

etc., created by excavation, diking, or construction may be directly connected to the “waters of the US” 

by shallow or deeper groundwater, therefore, a “blanket” exemption is not recommended. Each feature 

should be cleared by a systematic hydrologic system analysis. These exemptions invited multiple 

abuses to the Rule, particularly when land ownership and land use are changed with time. 

Kolm Comments Page 73
Individual comments from members of the SAB Panel for the Review of the EPA Water Body Connectivity Report. 

These comments do not represent consensus SAB advice or EPA policy.

Page 22195:

EPA and the Corps are very interested in identifying other emerging technologies or approaches that 

would save time and money and improve efficiency for regulators and the regulated community in 

determining which waters are subject to CWA jurisdiction. The agencies specifically invite comment on 

this topic.

Restated from above and note references: Using Hydrologic-Landscape Regions and Ecoregions as a 

basis for determining the connectivity of hydrologic and biologic systems to “waters of the U.S.” is an 

excellent first step in understanding the holistic nature of these systems in any location when combined 

with the standard approach that involves characterizing the surface and subsurface elements of 

landscapes to determine flowpath networks at multiple temporal and spatial scales. Important elements 

include climate, geology, topographic relief, and the amount, distribution and types of waters and 

wetlands. These elements, in context with the HLRs and Ecoregions, can then be integrated to create a 

flowpath network that describes connectivity (Heath 1983; ASTM 1996; Kolm et al. 1996; Winter et al. 

1998). This approach has been extended to biological connectivity and hydrogeomorphic (HGM) 

wetland classifications (e.g., Kolm et al. 1998).

B. Background on Scientific Review and Significant Nexus Analysis – Page 22195

Page 22198:

In addition to the proposed ‘‘other waters’’ approach in this rule, the agencies are requesting comment 

on a range of alternate approaches to inform their decision on how best to address ‘‘other waters.’’ The 

agencies will consider the full administrative record, including comments requested and received, and 

the final Report, as revised in response to the SAB review, when developing the final rule, and may 

adopt one of the alternative approaches or combination of approaches and the proposal.

To clarify the connectivity of “other waters” to “waters of the US”, the SAB recommends that a 

conceptual framework be established expressed as continuous hydrological (surface and subsurface), 

chemical, and biological flowpaths connecting watersheds from top to bottom, and therefore connecting 

other waters and wetlands to downgradient waters. The flowpath framework should highlight the fourdimensional nature of connectivity, because four-dimensional connectivity scaled in a habitat-tocatchment context is a foundational aspect of freshwater ecology (e.g., Ward 1989). The flux and 

transformation of water, materials, and organisms – which fundamentally control the integrity of 

downgradient freshwater ecosystems – occur at varying rates primarily determined by climate, geology, 

topographic relief, and biology and are expressed in terms of surface water and ground water storage 

and flow through the landscape (e.g., uplands, wetlands, lakes, rivers, and floodplains). Therefore, these 

flowpaths are inherently four-dimensional (i.e., longitudinal, lateral, vertical, and through time). 

Using Hydrologic-Landscape Regions and Ecoregions as a basis for determining the connectivity of 

hydrologic and biologic systems to “waters of the U.S.” is an excellent first step in understanding the 

holistic nature of these systems in any location when combined with the standard approach that involves 

characterizing the surface and subsurface elements of landscapes to determine flowpath networks at 

multiple temporal and spatial scales. Important elements include climate, geology, topographic relief, 

and the amount, distribution and types of waters and wetlands. These elements, in context with the 

Kolm Comments Page 74
Individual comments from members of the SAB Panel for the Review of the EPA Water Body Connectivity Report. 

These comments do not represent consensus SAB advice or EPA policy.

HLRs and Ecoregions, can then be integrated to create a flowpath network that describes connectivity 

(Heath 1983; ASTM 1996; Kolm et al. 1996; Winter et al. 1998). This approach has been extended to 

biological connectivity and hydrogeomorphic (HGM) wetland classifications (e.g., Kolm et al. 1998).

III. Proposed Definition of Waters of the United States – Page 22198 

Page 22199: Primary source of connectivity is groundwater, yet:

CWA Exclusions: groundwater, including groundwater drained through subsurface drainage systems.

Restated from above text: In no cases should groundwater that is shown to be connected to “waters of 

the US” be exempt (see comments above). Each of the features listed for exemptions to the Rule may be 

connected to “waters of the US” depending on the hydrogeologic framework that is underneath the 

features, and the hydrologic system that the features are constructed within. Artificial lakes or ponds, or 

reflection pools, etc., created by excavation, diking, or construction may be directly connected to the 

“waters of the US” by shallow or deeper groundwater, therefore, a “blanket” exemption is not 

recommended. Each feature should be cleared by a systematic hydrologic system analysis. These 

exemptions can invite multiple abuses to the Rule, particularly when land ownership and land use are 

changed with time. 

Appendix A. Overview of the Scientific Literature on Aquatic Resource Connectivity and 

Downstream Effects -- Page 22222 

Comments listed above by category.

The regulatory text of the proposed rule -- Page 22262. 

Comments listed above by category.

Additional Comments Regarding the Adequacy of the Scientific and Technical Basis of the Proposed 

Rule Titled Definition of Waters of the United States Under the Clean Water Act (79FR 22188-22274)

Kenneth E. Kolm, Ph.D.

Submitted on August 25, 2014

Questions 

1. The proposed rule has defined Waters of the U.S. under the jurisdiction of the Clean Water Act to mean all 

tributaries of a traditional navigable water, interstate water, the territorial seas, or impoundment. This 

definition is based on the conclusion that a significant nexus exists between tributaries (as defined in the 

proposed rule) and the traditional navigable waters, interstate waters, and the territorial seas into which they 

flow. Please comment on the adequacy of the scientific and technical basis of this proposed definition. (lead 

discussants are: Drs. Emma Rosi-Marshall and Jennifer Tank) 

Kolm Comments Page 75
Individual comments from members of the SAB Panel for the Review of the EPA Water Body Connectivity Report. 

These comments do not represent consensus SAB advice or EPA policy.

2. The proposed rule has defined Waters of the U.S. under the jurisdiction of the Clean Water Act to mean all 

waters, including wetlands, adjacent to traditional navigable water, interstate water, the territorial seas, 

impoundment, or tributary. This definition is based on the conclusion that a significant nexus exists between 

adjacent water bodies (as defined in the proposed rule) and traditional navigable waters, interstate waters, 

and the territorial seas. Please comment on the adequacy of the scientific and technical basis of this proposed 

definition. (lead discussants are: Drs. Siobhan Fennessy and Mazeika Sullivan) 

Page 22203:

An alternate approach would be to clarify that wetlands that connect tributary segments are adjacent 

wetlands, and as such are jurisdictional waters of the United States under (a)(6). In this approach, a 

tributary would be defined as having a bed and bank and OHWM, and the upper limit of the tributary 

would be defined by the point where these features cease to be identifiable.

(Note that natural or manmade breaks would still not sever jurisdiction if a tributary segment with a bed 

and bank and OHWM could be identified upstream of the break.) Wetlands would not be considered 

tributaries, but would remain jurisdictional as adjacent waters. Wetlands that contribute flow, for 

example at the upper reaches of the tributary system, would be considered adjacent waters.

Add:

HESA is an approach that is based on four-dimensional flowpaths and can be used to clarify the 

connectivity of wetlands to “waters of the US” (ASTM 1996; Kolm et al. 1996; Kolm et al. 1998; Kolm 

and Smith 2012; see description below).

Page 22207:

Waters, including wetlands, determined to have a shallow subsurface hydrologic connection or confined 

surface hydrologic connection to an (a)(1) through (a)(5) water would also be ‘‘waters of the United 

States’’ by rule as adjacent waters falling within the definition of ‘‘neighboring.’’

Add:

HESA is an approach that is based on four-dimensional flowpaths and can be used to clarify the 

connectivity of adjacent waters to “waters of the US (ASTM 1996; Kolm et al. 1996; Kolm et al. 1998; 

Kolm and Smith 2012; see description below).

Page 22207:

In circumstances where a particular water body is outside of the floodplain and riparian area of a 

tributary, but is connected by a shallow subsurface hydrologic connection or confined surface 

hydrologic connection with such tributary, the agencies will also assess the distance between the water 

body and tributary in determining whether or not the water body is adjacent. ‘‘Adjacent’’ as defined in 

the agencies’ regulations has always included an element of reasonable proximity.

Add:

Kolm Comments Page 76
Individual comments from members of the SAB Panel for the Review of the EPA Water Body Connectivity Report. 

These comments do not represent consensus SAB advice or EPA policy.

HESA is an approach that is based on four-dimensional flowpaths and can be used to clarify the 

connectivity of adjacent waters to “waters of the US (ASTM 1996; Kolm et al. 1996; Kolm et al. 1998; 

Kolm and Smith 2012; see description below).

Page 22208:

Therefore, the determination of whether a particular water meets the definition of ‘‘neighboring’’ 

because the water is connected by a shallow subsurface or confined surface hydrologic connection is 

made in the context of the terms ‘‘neighboring’’ and ‘‘adjacent’’ as used in the regulation.

Add:

HESA is an approach that is based on four-dimensional flowpaths and can be used to clarify the 

connectivity of neighboring waters to “waters of the US (ASTM 1996; Kolm et al. 1996; Kolm et al. 

1998; Kolm and Smith 2012; see description below).

Page 22208:

While the agencies’ best professional judgment has always been a factor in determining whether a 

particular wetland is ‘‘adjacent’’ under the existing definition, the agencies recognize that this may 

result in some uncertainty as to whether a particular water connected through confined surface or 

shallow subsurface hydrology is an ‘‘adjacent’’ water. The agencies therefore request comment on 

whether there are other reasonable options for providing clarity for jurisdiction over waters with these 

types of connections.

HESA is an approach that is based on four-dimensional flowpaths and can be used to clarify the 

connectivity of adjacent waters to “waters of the US (ASTM 1996; Kolm et al. 1996; Kolm et al. 1998; 

Kolm and Smith 2012; see description below).

Page 22208:

Options could include asserting jurisdiction over all waters connected through a shallow subsurface 

hydrologic connection or confined surface hydrologic connection regardless of

distance; asserting jurisdiction over adjacent waters only if they are located in the floodplain or riparian 

zone of a jurisdictional water; considering only confined surface connections but not shallow subsurface 

connections for purposes of determining adjacency; or establishing specific geographic limits for using 

shallow subsurface or confined surface hydrological connections as a basis for determining adjacency, 

including, for example, distance limitations based on ratios compared to the bank-to-bank width of the 

water to which the water is adjacent. The agencies note that under the proposed rule any waters not 

fitting within (a)(1) through (a)(6) categories would instead be treated as ‘‘other waters.’’ Options could 

include asserting jurisdiction over all waters connected through a shallow subsurface hydrologic 

connection or confined surface hydrologic connection regardless of distance; asserting jurisdiction over 

adjacent waters only if they are located in the floodplain or riparian zone of a jurisdictional water; 

considering only confined surface connections but not shallow subsurface connections for purposes of 

determining adjacency; or establishing specific geographic limits for using shallow subsurface or 

confined surface hydrological connections as a basis for determining adjacency, including, for example, 

Kolm Comments Page 77
Individual comments from members of the SAB Panel for the Review of the EPA Water Body Connectivity Report. 

These comments do not represent consensus SAB advice or EPA policy.

distance limitations based on ratios compared to the bank-to-bank width of the water to which the water 

is adjacent. The agencies note that under the proposed rule any waters not fitting within (a)(1) through 

(a)(6) categories would instead be treated as ‘‘other waters.’’ 

Add:

HESA is an approach that is based on four-dimensional flowpaths and can be used for asserting 

jurisdiction over all waters connected through a shallow subsurface hydrologic connection or confined 

surface hydrologic connection regardless of distance (ASTM 1996; Kolm et al. 1996; Kolm et al. 1998; 

Kolm and Smith 2012; see description below).

Page 22208:

A shallow subsurface hydrologic connection is lateral water flow through a shallow subsurface layer, 

such as can be found, for example, in steeply sloping forested areas with shallow soils, or in soils with a 

restrictive layer that impedes the vertical flow of water, or in karst systems, specially karst pans. K.J. 

Devito, et al., ‘‘Groundwater-Surface Water Interactions in Headwater

Forested Wetlands of the Canadian Shield,’’ Journal of Hydrology 181:127–47 (1996); M.A.’Driscoll, 

and R.R. Parizek, ‘‘The Hydrologic Catchment Area of a Chain of Karst Wetlands in Central 

Pennsylvania, USA,’’ Wetlands 23:171–79 (2003); B.J. Cook, and F.R. Hauer, ‘‘Effects of Hydrologic 

Connectivity on Water Chemistry, Soils, and Vegetation Structure and Function in an Intermontane 

Depressional Wetland Landscape,’’ Wetlands 27:719– 38 (2007). A shallow subsurface connection also 

exists, for example, when the adjacent water and neighboring (a)(1) through (a)(5) water are in contact 

with the same shallow aquifer. Shallow subsurface connections may be found both within the ordinary 

root zone and below the ordinary root zone (below 12 inches), where other wetland delineation factors 

may not be present. A combination of physical factors may reflect the presence of a shallow subsurface 

connection, including (but not limited to) stream hydrograph (for example, when the hydrograph 

indicates an increase in flow in an area where no tributaries are entering the stream), soil surveys (for 

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

indicating the water table in the stream is lower than in the shallow subsurface.

Shallow subsurface connections are distinct from deeper groundwater connections, which do not satisfy 

the requirement for adjacency, in that the former exhibit a direct connection to the water found on the 

surface in wetlands and open waters. Water does not have to be continuously present in the confined 

surface or shallow subsurface hydrologic connection and the flow between the adjacent water and the 

jurisdictional water may move in one or both directions. While they may provide the connection 

establishing jurisdiction, these shallow subsurface flows are not ‘‘waters of the United States.’’ For 

waters outside of the riparian area or floodplain, confined surface hydrologic connections (as described 

above) are the only types of surface hydrologic connections that satisfy the requirements for adjacency. 

Waters outside of the riparian area or floodplain that lack a shallow subsurface hydrologic connection or 

a confined surface hydrologic connection would be analyzed as ‘‘other waters’’ under paragraph (a)(7) 

of the proposed rule.

Add:

Kolm Comments Page 78
Individual comments from members of the SAB Panel for the Review of the EPA Water Body Connectivity Report. 

These comments do not represent consensus SAB advice or EPA policy.

HESA is an approach that is based on four-dimensional flowpaths and can be used for asserting 

jurisdiction over all waters connected through a shallow or deep subsurface hydrologic connection or 

confined surface hydrologic connection regardless of distance (ASTM 1996; Kolm et al. 1996; Kolm et 

al. 1998; Kolm and Smith 2012; see description below).

Page 22209:

The agencies intend to similarly interpret the new definition of ‘‘neighboring.’’ This new definition is 

designed to provide greater clarity by identifying specific areas and characteristics for jurisdictional 

adjacent waters, but the agency’s request comment for additional clarification. Commenters should 

support where possible from scientific literature any suggestions for additional clarification of current 

explicit limits on adjacency, such as a specific distance or a specific floodplain interval. The agencies 

seek comment on specific options for establishing additional precision in the definition of 

‘‘neighboring’’ through: explicit language in the definition that waters connected by shallow subsurface 

hydrologic or confined surface hydrologic connections to an (a)(1) through (a)(5) water must be 

geographically proximate to the adjacent water; circumstances under which waters outside the 

floodplain or riparian zone are jurisdictional if they are reasonably proximate; support for or against 

placing geographic limits on what waters outside the floodplain or riparian zone are jurisdictional; 

determining that only waters within the floodplain, only waters within the riparian area, or only waters 

within the floodplain and riparian area (but not waters outside these areas with a shallow subsurface or 

confined surface hydrologic connection) are adjacent; identification of particular floodplain intervals 

within which waters would be considered adjacent; and any other scientifically valid criteria, guidelines 

or parameters that would increase clarity with respect to neighboring waters.

Add:

HESA is an approach that is based on four-dimensional flowpaths and can be used to clarify the 

connectivity of neighboring waters to “waters of the US (ASTM 1996; Kolm et al. 1996; Kolm et al. 

1998; Kolm and Smith 2012; see description below).

3. The proposed rule has defined Waters of the U.S. under the jurisdiction of the Clean Water Act to mean, 

on a case-specific basis, other waters including wetlands, provided that those waters alone, or in combination 

with other similarly situated waters, including wetlands, located in the same region, have a significant nexus 

to a traditional navigable water, interstate water, or the territorial seas. Please comment on the adequacy of 

the scientific and technical basis of this proposed definition. (lead discussants are: Drs. Emily Bernhardt and 

Michael Gooseff)

Page 22211:

For purposes of analyzing whether an ‘‘other water’’ has a significant nexus, the agencies are proposing 

that ‘‘other waters’’ are similarly situated if they perform similar functions and they are either (1) 

located sufficiently close together so that they can be evaluated as a single landscape unit with regard to 

their effect on the chemical, physical, or biological integrity of a water identified in paragraphs (a)(1) 

through (a)(3), or (2) located sufficiently close to a ‘‘water of the United States’’ for such an evaluation 

of their effect. These criteria are explained in a subsequent section. Consistent with Justice Kennedy’s 

opinion in Rapanos, the agencies propose today and are soliciting comment on establishing a casespecific analysis of whether ‘‘other waters,’’ including wetlands, that do not meet the criteria for any of 

Kolm Comments Page 79
Individual comments from members of the SAB Panel for the Review of the EPA Water Body Connectivity Report. 

These comments do not represent consensus SAB advice or EPA policy.

the proposed jurisdictional categories in (a)(1) through (a)(6) and are not proposed to be excluded by 

rule under section (b),

are susceptible to a case-specific analysis of whether they alone, or in combination with other similarly 

situated waters, have a significant nexus to a traditional navigable water, an interstate water, or the 

territorial seas, and therefore are ‘‘waters of the United States.’’

Add:

HESA is an approach that is based on four-dimensional flowpaths and can be used to clarify the 

connectivity of “other waters” to “waters of the US” (ASTM 1996; Kolm et al. 1996; Kolm et al. 1998; 

Kolm and Smith 2012; see description below).

Page 22212:

The agencies also request comment and information below on how the science could support other 

approaches that could provide greater regulatory certainty regarding the jurisdictional status of ‘‘other 

waters’’

Add:

HESA is an approach that is based on four-dimensional flowpaths and can be used to clarify the 

connectivity of “other waters” connected through a shallow subsurface hydrologic connection or 

confined surface hydrologic connection regardless of distance and to quantify connectivity to “waters of 

the US” (ASTM 1996; Kolm et al. 1996; Kolm et al. 1998; Kolm and Smith 2012; see description 

below).

Page 22212: 

Add:

HESA is an approach that is based on four-dimensional flowpaths and can be used to provide a better 

understanding of ground water connectivity, and the way that ground water connectivity might vary 

spatially, based on the ASTM D5979-96 Standard Guide for Conceptualization and Characterization of 

Ground Water Systems (ASTM 1996; Kolm et al. 1996) to “waters of the US” (also Kolm et al. 1998; 

Kolm and Smith 2012; see description below).

Page 22213:

In determining whether other waters are sufficiently close to each other or to a water of the United 

States, the agencies would also consider hydrologic connectivity to each other or

a jurisdictional water. 

In determining whether groups of other waters perform ‘‘similar functions’’ the agencies would also 

consider functions such as habitat, water storage, sediment retention, and pollution sequestration. These 

and other relevant considerations would be used by the agencies to document the hydrologic, 

geomorphic and ecological characteristics and circumstances of the water. The agencies solicit 

Kolm Comments Page 80
Individual comments from members of the SAB Panel for the Review of the EPA Water Body Connectivity Report. 

These comments do not represent consensus SAB advice or EPA policy.

comment regarding this approach to ‘‘other waters,’’ recognizing that a case-specific analysis of 

significant nexus is resource intensive for the regulating agencies and the regulated community alike. In 

addition, the agencies solicit comment on additional scientific research and data that might further 

inform decisions about ‘‘other waters.’’ In particular the agencies solicit information about whether 

current scientific research and data regarding particular types of waters are sufficient to support the 

inclusion of subcategories of types of ‘‘other waters,’’ either alone or in combination with similarly 

situated waters, that can appropriately be identified as always lacking or always having a significant 

nexus.

The agencies acknowledge that there may be more than one way to determine which waters are 

jurisdictional as ‘‘other waters.’’ This proposal is for a case-specific analysis of whether ‘‘other

waters,’’ including wetlands, alone, or in combination with other similarly situated waters located in the 

same region, have a significant nexus to a traditional navigable water, interstate water, or the territorial 

seas. The agencies make this proposal based on an analysis of the current state of the science available 

to them. In this proposal, the agencies continue to solicit additional science (peer-reviewed whenever 

possible) that could lead to greater clarity, certainty, and predictability of which waters are and are not 

within the jurisdiction of the CWA.

Add:

HESA is an approach that is based on four-dimensional flowpaths and can be used to clarify the 

connectivity of “other waters” to “waters of the US” (ASTM 1996; Kolm et al. 1996; Kolm et al. 1998; 

Kolm and Smith 2012; see description below).

Page 22216:

The factors the agencies used in developing the list above are: 

a. Density of ‘‘other waters’’ such that there can be periodic surface hydrologic connections among the 

waters, for example in West Coast vernal pools.

b. Soil permeability and surface or shallow subsurface flow such that the ‘‘other waters’’ can be 

considered hydrologically connected, such as many Texas coastal prairie wetlands.

c. Water chemistry which indicates that the ‘‘other waters’’ are part of the same system and influenced 

by the same processes.

d. Physical capacity of ‘‘other waters’’ to provide flood and sediment retention; this is a case where 

several small wetlands together may have a different effect than a single large wetland providing the 

same function, for example prairie potholes in the Missouri Coteau.

e. Co-location of waters to each other or similarly to the tributary system such that their cumulative and 

additive effects on pollutant removal through parallel, serial, or sequential processing are apparent, such 

as the role of pocosins in maintaining water quality in estuaries.

f. ‘‘Other waters’’ that are sufficiently near each other or the tributary system and thus function as an 

integrated habitat that can support the life cycle of a species or more broadly provide habitat to a large 

number of a single species.

Kolm Comments Page 81
Individual comments from members of the SAB Panel for the Review of the EPA Water Body Connectivity Report. 

These comments do not represent consensus SAB advice or EPA policy.

The agencies request comment on the factors above and whether this list of factors is appropriate, and 

whether there are other factors that should be included or excluded from this list. Comments should 

address the science that supports each comment.

Add:

HESA is an approach that is based on four-dimensional flowpaths and can be used to clarify the 

connectivity of “other waters” connected through a shallow or deep subsurface hydrologic connection or 

confined surface hydrologic connection regardless of distance and to quantify connectivity to “waters of 

the US” (ASTM 1996; Kolm et al. 1996; Kolm et al. 1998; Kolm and Smith 2012; see description 

below).

Page 22216:

Discussion of Hydrologic-Landscape Regions. Then: 

The agencies seek comment on the technical bases for using ecoregions and hydrologic-landscape 

regions under this option. Commenters may also address whether some other method or combination of 

methods (certain ecoregions and hydrologic-landscape regions, for example) of mapping geographic 

boundaries is better supported by the science. Comments should also address whether and how this 

option is consistent with the science and the caselaw.

Modify paragraph to state:

Using Hydrologic-Landscape Regions and Ecoregions as a basis for determining the connectivity of 

hydrologic and biologic systems to “waters of the U.S.” is an excellent first step in understanding the 

holistic nature of these systems in any location when combined with the HESA approach that involves 

characterizing the surface and subsurface elements of landscapes to determine flowpath networks at 

multiple temporal and spatial scales. Important elements include climate, geology, topographic relief, 

and the amount, distribution and types of waters and wetlands. These elements, in context with the 

HLRs and Ecoregions, can then be integrated to create a flowpath network that describes connectivity 

(Heath 1983; ASTM 1996; Kolm et al. 1996; Winter et al. 1998). The HESA approach has been 

extended to biological connectivity, paleohydrologic analysis (Kolm and Smith 2012), and 

hydrogeomorphic (HGM) wetland classifications (e.g., Kolm et al. 1998).

Page 22217:

3. Additional ‘‘other waters’’ approaches. The agencies request comment on additional ‘‘other waters’’ 

approaches considered, but not proposed by the agencies.

Add:

HESA is an approach that is based on four-dimensional flowpaths and can be used to clarify the 

connectivity of “other waters” connected through a shallow or deep subsurface hydrologic connection or 

confined surface hydrologic connection regardless of distance and to quantify connectivity to “waters of 

Kolm Comments Page 82
Individual comments from members of the SAB Panel for the Review of the EPA Water Body Connectivity Report. 

These comments do not represent consensus SAB advice or EPA policy.

the US” (ASTM 1996; Kolm et al. 1996; Kolm et al. 1998; Kolm and Smith 2012; see description 

below).

4. The proposed rule defines other terms and excludes specified waters and features from the definition of 

Waters of the U.S. Please comment on the adequacy of the scientific and technical basis of the other 

definitions and exclusions. (lead discussants are: Drs. David Allan and Mark Rains) 

Page 22203:

The agencies specifically seek comment on the appropriate flow regime for a ditch excavated wholly in 

uplands and draining only uplands to be included in the exclusion of paragraph (b)(3). In particular, the 

agencies seek comment on whether the flow regime in such ditches should be less than intermittent flow 

or whether the flow regime in such ditches should be less than perennial flow as proposed.

The agencies request comment on this formulation of the ditch exclusion. The agencies specifically seek 

comment on the appropriate flow regime for a ditch excavated wholly in uplands and draining only 

uplands to be covered by the exclusion in paragraph (b)(3). In particular, the agencies seek comment on 

whether the flow regime in such ditches should be less than intermittent flow or whether the flow regime 

in such ditches should be less than perennial flow as proposed.

Add:

HESA is an approach that is based on four-dimensional flowpaths and can be used to clarify the 

connectivity of ditches or other exempted features, including those features connected through a shallow 

or deep subsurface hydrologic connection or confined surface hydrologic connection regardless of 

distance, and to quantify feature connectivity to “waters of the US” (ASTM 1996; Kolm et al. 1996; 

Kolm et al. 1998; Kolm and Smith 2012; see description below).

5. If you have any other comments about the adequacy of the scientific and technical basis of the proposed 

rule, please provide them as well. 

EPA’s Proposed Rule 

Preamble (explains the basis and purpose for the proposed rule) 

The agencies acknowledge that there may be more than one way to determine which waters are 

jurisdictional as ‘‘other waters.’’ To best meet their goals and responsibilities, the agencies request 

comment on alternate approaches to determining whether ‘‘other waters’’ are similarly situated and have 

a ‘‘significant nexus’’ to a traditional navigable water, interstate water, or the territorial seas. In the 

discussion of ‘‘other waters’’ later in the preamble, the agencies seek comment on these other 

approaches and whether they could better meet the goals of greater predictability and consistency 

through increased clarity, while simultaneously fulfilling the agencies’ responsibility to the CWA’s 

objectives and policies to protect water quality, public health, and the environment.

Kolm Comments Page 83
Individual comments from members of the SAB Panel for the Review of the EPA Water Body Connectivity Report. 

These comments do not represent consensus SAB advice or EPA policy.

Commenters will specifically be asked to comment on whether and how these alternate approaches may 

be more consistent with the goal of clarity, and the CWA, the best available science, and the caselaw. In 

particular, the agencies are interested in comments, scientific and technical data, caselaw, and other 

information that would further clarify which ‘‘other waters’’ should be considered similarly situated for 

purposes of a case-specific significant nexus determination. The agencies seek comment on a number of 

alternative approaches. These alternatives include potentially determining waters in identified ecological 

regions (ecoregions) or hydrologic-landscape regions are similarly situated for purposes of evaluating a 

significant nexus, as well as the basis for determining which ecoregions or hydrologic-landscape regions 

should be so identified.

Add:

HESA is an approach that is based on four-dimensional flowpaths and can be used to clarify the 

connectivity of “other waters” connected through a shallow or deep subsurface hydrologic connection or 

confined surface hydrologic connection regardless of distance and to quantify connectivity to “waters of 

the US” (ASTM 1996; Kolm et al. 1996; Kolm et al. 1998; Kolm and Smith 2012; see description 

below).

II. Background -- Page 22190

C. Executive Summary -- Page 22190

Page 22195:

EPA and the Corps are very interested in identifying other emerging technologies or approaches that 

would save time and money and improve efficiency for regulators and the regulated community in 

determining which waters are subject to CWA jurisdiction. The agencies specifically invite comment on 

this topic.

Add:

HESA is an approach that is based on four-dimensional flowpaths and can be used to clarify the 

connectivity of “adjacent waters”, “neighboring waters”, and “other waters” connected through a 

shallow or deep subsurface hydrologic connection or confined surface hydrologic connection regardless 

of distance and to quantify connectivity to “waters of the US” (ASTM 1996; Kolm et al. 1996; Kolm et 

al. 1998; Kolm and Smith 2012; see description below).

D. Background on Scientific Review and Significant Nexus Analysis – Page 22195

Page 22198:

In addition to the proposed ‘‘other waters’’ approach in this rule, the agencies are requesting comment 

on a range of alternate approaches to inform their decision on how best to address ‘‘other waters.’’ The 

agencies will consider the full administrative record, including comments requested and received, and 

the final Report, as revised in response to the SAB review, when developing the final rule, and may 

adopt one of the alternative approaches or combination of approaches and the proposal.

Kolm Comments Page 84
Individual comments from members of the SAB Panel for the Review of the EPA Water Body Connectivity Report. 

These comments do not represent consensus SAB advice or EPA policy.

Add:

HESA is an approach that is based on four-dimensional flowpaths and can be used to clarify the 

connectivity of “other waters” connected through a shallow or deep subsurface hydrologic connection or 

confined surface hydrologic connection regardless of distance and to quantify connectivity to “waters of 

the US” (ASTM 1996; Kolm et al. 1996; Kolm et al. 1998; Kolm and Smith 2012; see description 

below).

The following description of HESA is modified from or described in ASTM Standard D5979. “Standard 

Guide for Conceptualization and Characterization of Groundwater Systems.” (ASTM 1996); Kolm et 

al. (1996); Kolm et al. (1998); and Kolm and Smith (2012):

DESCRIPTION OF HYDROLOGIC SYSTEMS ANALYSIS (HESA)

APPROACH

HESA is an approach used to conceptualize and 

characterize relevant features of hydrologic and 

environmental systems, integrating relevant considerations 

of climate, topography, geomorphology, groundwater and 

surface water hydrology, geology, ecosystem structure and 

function, and the human activities associated with these 

systems into a holistic, three-dimensional dynamic 

conceptual site model (CSM). Using HESA, all relevant 

controlling factors of a particular environment can be 

identified at the planning/characterization stage, leading to 

more focused, cost effective strategies and better decisionmaking throughout a project or study. 

HESA is completed by an interdisciplinary expert science and engineering team to ensure a rapid, cost-effective 

analysis resulting in cutting-edge regional and site-scale conceptual modeling and characterization of the 

hydrologic and environmental systems. This approach adds breadth and depth to standard modeling by identifying 

formerly unobserved relationships and interconnections at 

the micro, macro, and regional scales. This approach can 

be used during all stages of the project to develop a 

rigorous understanding of the past, present, and future 

behaviors of systems and processes. The resulting multitemporal and multi-scale views allow for the users to 

reduce costs and incorporate sustainable practices in site 

decision-making through development of improved 

engineering solutions and mitigation of long-term 

environmental liabilities. 

DOCUMENTED APPLICATIONS

HESA is used for mine and resource development and 

mined-land restoration, local and regional development and 

protection of groundwater and surface water supplies, watershed and site-scale pollution prevention and regulatory 

cleanup, and water rights and water quality regulation, expert witness and litigation support. 

Kolm Comments Page 85
Individual comments from members of the SAB Panel for the Review of the EPA Water Body Connectivity Report. 

These comments do not represent consensus SAB advice or EPA policy.

$ Site-scale analysis for water resource characterization, remediation, modeling, and/or management

$ Wetlands analysis for characterization and/or remediation – restoration, pollution prevention, cleanup

$ Watershed-scale analysis for urbanization, water supply and quality, pollution, and superfund cleanup 

applications

$ Multiple-scale analysis for environmentally sensitive resource development and mine/petroleum site closure 

applications

$ Connectivity or Nexus of water bodies 

SELECTED REFEREED REFERENCES

Kolm, K.E. and S.M. Smith. 2012. Chapter 5. Modeling Paleohydrological System Structure and Function. In 

Emergence and Collapse of early Villages: Models of Central Mesa Verde Archaeology. Edited by T.A. Kohler 

and M.D. Varien, University of California Press; Los Angeles, CA., pp. 73-83.

Kolm, K.E., and W.H. Langer. 2001. Hierarchical systems analysis in karst terrains: Part A. 

Approaches and applications to environmental characterization. U.S. Geological Survey Open File 

Report 00-429A, CD-ROM.

Langer, W.H., and K.E. Kolm. 2001. A systems approach to characterize and evaluate environmental 

impacts from aggregate mining, in Kuula-Väisänen, P., and R. Uusinoka, (eds). Aggregate 2001 –

Environment and economy. Tampere University of Technology Publication no. 51, pp. 401–406.

Langer, W.H., and K.E. Kolm. 2001. Hierarchical systems analysis in karst terrains: Part B. Analysis of 

environmental impacts of aggregate mining. U.S. Geological Survey Open File Report 00-429B, CDROM.

Kolm, K.E., R.M. Harper-Arabie, and J.C. Emerick. 1998. A stepwise, integrated hydrogeomorphic 

approach for the classification of wetlands and assessment of wetland hydrological and geochemical 

function in the Southern Rocky mountains of Colorado. Colorado Geologic Survey, Colorado 

Department of Natural Resources Technical Report, Denver, CO. 

Kolm, K.E. 1996. Conceptualization and characterization of ground-water systems using geographical 

information systems. In: Remote Sensing and GIS for Site Characterization: Applications and 

Standards, ASTM STP 1279, V.H. Singhroy, D.D. Nebert, and A.L. Johnson (eds). American Society for 

Testing and Materials, West Conshohocken, PA. pp. 120–134.

Kolm, K.E. 1996. Conceptualization and characterization of ground-water systems using geoscientific 

information systems. In: Special Issue: Advanced Techniques for Solving Groundwater Contaminant 

Problems. J. May, and K.E. Kolm (eds). Engineering Geology 42:(2–3):111–118.

Kolm Comments Page 86
Individual comments from members of the SAB Panel for the Review of the EPA Water Body Connectivity Report. 

These comments do not represent consensus SAB advice or EPA policy.

Kolm, K.E., P.K.M. van der Heijde, J.S. Downey, and E.D. Gutentag. 1996. Conceptualization and 

characterization of ground-water flow systems. In: Subsurface Fluid-Flow (Ground-Water and Vadose 

Zone) Modeling, Ritchey, J.D., and J.O. Rumbaugh (eds). ASTM STP 1288, American Society for Testing 

and Materials, West Conshohocken, PA., pp. 61–80.

Talbot, W.R., and K.E. Kolm. 1996. Application of a step-wise, integrated method of characterizing 

hydrologic systems using GIS: A site-specific case study at an NPL site near Cheyenne, Wyoming. In: 

Special Issue: Advanced Techniques for Solving Groundwater Contaminant Problems. J. May and K.E. 

Kolm (eds). Engineering Geology 42(2-3):139–153.

May, J., and K.E. Kolm (eds). 1996. Special Issue: Advanced Techniques for Solving Groundwater 

Contaminant Problems: Engineering Geology 42(2-3):109–215.

The following logic chart, developed for applications regarding municipality water management (the word 

“county” could be replaced by “agency”, for example), is modified from Kolm and Smith (2012):

Kolm Comments Page 87
Individual comments from members of the SAB Panel for the Review of the EPA Water Body Connectivity Report. 

These comments do not represent consensus SAB advice or EPA policy.

Dr. Judith Meyer

Comments from Dr. Judy Meyer

I will not be able to participate in the teleconferences to be held this week, but look forward to being 

able to provide comments on the resulting report. I have read the proposed rule as well as the 

comments provided by other panel members. Since I won’t be on the call, I am providing some brief 

comments in a slightly different form, namely as thoughts on the comments provided by other panel 

members in response to question 1, which covers my area of expertise. Essentially I am writing 

down some of the points I would have made had I been able to participate in the call.

I agree with the statements of most panel members that EPA and the Corps should be congratulated 

because of the clarity with which the strong scientific support for the proposed rule has been 

presented.

I agree with the statements of most panel members that the inclusion of all tributaries is consistent with 

best available science. Several panel members have provided extensive explanations of the scientific 

support for the inclusion of tributaries, and these explanations should be incorporated into our report. 

Dr. Aldous raises what seems to be a legitimate concern about whether spring-fed tributaries with 

constant flow meet the OHWM requirement, but others with more experience with designation of 

OHWM in these types of streams may be able to clarify how OHWM is determined in these systems. 

Presumably if flow is that constant, the OHWM would simply be the current water level. 

Dr. Allan and Dr. Johnson both raise important concerns about the exclusion of ditches that are in 

uplands. Dr. Tank’s point that the flow regime in identified ditches be less than intermittent rather 

than less than perennial has merit. In addition to these important points raised, I wonder if the term 

“upland” has been adequately defined.

I do not agree with Dr. Josselyn’s comments on the absence of scientific support for inclusion of 

headwater streams. Considerable scientific research has been done on first and second order 

headwater streams; the scientific research supporting the inclusion of tributaries is not limited to

third and fourth order streams as he has stated.

I agree with several panel members who noted the scientific support for inclusion of human-altered 

channels in the definition of tributaries.

Dr. .Johnson makes an important point about the need for high resolution mapping products that should 

be part of our report.

Meyer Comments Page 88
Individual comments from members of the SAB Panel for the Review of the EPA Water Body Connectivity Report. 

These comments do not represent consensus SAB advice or EPA policy.

Dr. Mark Murphy`

`

Date: August 13, 2014

Subject: EPA Proposed Rule; Definition of ‘‘Waters of the United States’’ Under the Clean

Water Act; 40 CFR Parts 110, 112, 116, et al.1

I have read and considered the Proposed Rule, as requested by the Chair of the SAB. I appreciate the

opportunity to represent the technical community in this extended dialogue on the matter of Clean Water

Act (CWA) applicability. This is a subject that my colleagues and I have pondered for many years

and we welcome EPA’s attempt to provide clarity. The complexities and subtleties of how to interpret

the CWA are formidable. I might add as a disclosure, that I am a strong supporter of the CWA and

have seen numerous examples of its protective power. My encouragement and criticisms over the course

of this process only reflect my desire to establish a solidly defensible rule that can add to this power.

In this light, I must say I am puzzled as to why EPA has decided to release the Proposed Rule before

receipt of our review of the Connectivity Report (EPA 2013). While I was told at our December 2013

meeting that a draft rule was in preparation, I hardly expected that the draft would be released to the

public before our review. The usual protocol in science is not to release a report before the review is 

complete, the purpose being to allow a frank and honest appraisal of the work before positions are

‘hardened’ and reputations are placed in jeopardy. The sequence employed by EPA suggests to the public

that there is no critical input needed by the SAB - - just a few minor additions. If I believed this to be

the case, I would be very dismayed.

In point of fact, the SAB Review suggested that some major additions be made to the Connectivity

Report. The most fundamental conclusion of the review was that a dichotomous, binary approach to

connectivity is not supported by the existing scientific literature. As was stated in the letter to the EPA 

Administrator,

“The (Connectivity) Report often refers to connectivity as though it is a binary property

(connected versus not connected) rather than as a gradient. In order to make the Report more

technically accurate, the SAB recommends that the interpretation of connectivity be revised to

reflect a gradient approach that recognizes variation in the frequency, duration, magnitude,

predictability, and consequences of those connections.” (EPA 2014)

1

Revised following 8/21/14 SAB teleconference. See final page.

Murphy Comments Page 89
Individual comments from members of the SAB Panel for the Review of the EPA Water Body Connectivity Report. 

These comments do not represent consensus SAB advice or EPA policy.

Nature rarely gives yes or no answers. For this reason, jurisdiction by rule based upon dichotomous

categories is simply not scientifically valid and appears to be based upon legal convenience.

Jurisdiction by rule, as applied in the Proposed Rule, is not supported by the best available science.

The legal record also seems to support this conclusion. A gradient in connectivity is clearly directed

by a common-sense reading of the Rapanos decision. The Proposed Rule states in several places that

the term ‘significant nexus,’ used in the decision, is not a scientific term. That may be correct in the

sense that the term is not found in the scientific literature; however, the phrase should be examined in

the context of Justice Kennedy’s next several comments,

“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.’”

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

Justice Kennedy, here and elsewhere, repeatedly relates the term ‘nexus’ and ‘significant nexus’ to

‘chemical, physical, and biological integrity,’ which are scientific terms. Nexus is defined by Webster as

a connection and a connection of one part of an ecosystem to the chemical, physical, and biological

integrity of another ecosystem, directly requires a cause-and-effect relationship to be a consequence.

Therefore, significant nexus, scientifically defined, clearly requires that there be a cause-and-effect,

connective relationship between the water body under examination and some downstream aquatic

ecosystem, ‘traditionally navigable’ if we continue with Justice Kennedy’s opinion.

The term ‘significant’ still needs better clarity. Non-technical significance is a vague concept,

whether legally or politically approached. It is never defined in the Proposed Rule other than to say

that it’s not ‘speculative’ or ‘insubstantial.’ Scientific significance is not at all vague, as any first-year

grad student quickly learns. The definition of significance in science is directly dependent upon a

proposed cause-and-effect hypothesis and the repeated testing of the explanatory adequacy of that

hypothesis. For example, if I flip a coin, I hypothesize that it will land as either heads or tails. Repeated

trials of the coin-flipping experiment show the repeatability of the results and the adequacy of my

explanation. If the coin always comes up heads or tails, then the ‘always’ part of the result is the

‘significance’ of the hypothesis, which can be quantified in many ways using statistical methodologies

(Ellison 1996, Johnson 2014).

In actuality, the coin could actually land on its edge. I’ve never seen that happen, but it could happen.

However, if the statistically based likelihood of this outcome is less than some accepted level, the

hypothesis of a non-heads-or-tails outcome is called ‘insignificant.’ This is not the same as creating a

dichotomous model of the coin flipping hypothesis; it simply states that most of the time coins come up

heads or tails. Using this simple example, jurisdiction by rule is akin to saying the coin will never land

Murphy Comments Page 90
Individual comments from members of the SAB Panel for the Review of the EPA Water Body Connectivity Report. 

These comments do not represent consensus SAB advice or EPA policy.

on its edge - - a reasonable conclusion only if we know the ‘one in a million’ statistical data for the

coin flipping experiment. And in Nature, the experiments are almost never this simple.

In any case, if the term ‘significant’ has any scientific relationship to ‘chemical, physical, and biological

integrity’ there would be a hypothetical cause for the consequential harm to that integrity. Repeatable

trials (or more likely in ecology, observations) of that cause- and-effect hypothesis would demonstrate

the scientific significance of its power to explain the downstream effect.

During the SAB Review, the panel was explicitly told not to discuss the definition of significance;

however, the cause-and-effect based definition discussed above is clearly implied throughout. For

example, in section 3.1 of the SAB Review, the authors state:

“As noted in the many public comments to the SAB, the binary perspective in the

(Connectivity) Report implies that any connectivity must significantly affect the biological,

physical, or chemical integrity of downstream waters. Although connectivity is known to be

ecologically important even at the lower end of the gradient, the frequency, duration,

predictability, and magnitude of connectivity will ultimately determine the consequences to 

downstream waters.” (EPA 2014)

This must be the approach used by the Proposed Rule, if it is to have a defensible basis in science. The

significance of the connection must be defined by the likelihood of a measurable effect, which is

controlled by the transport mechanism and pathway through the watershed.

This concept of a gradient of connectivity and downstream consequences is taken from the science of

disturbance ecology (Fisher 1983, Resh et al 1988, Poff et al 1997, Stanley et al 2010), which was not

characterized in the Connectivity Report and is not represented in the Proposed Rule. Given a cause

in the watershed, disturbance ecology characterizes the downstream effect on the physical, chemical

and biological integrity of the affected community.

These effects are scientifically related to the magnitude (the absolute or relative size of the

disturbance), the duration (how long the disturbance lasts), the frequency (how often does it return) and

the predictability (how regularly the disturbance returns). Effects upon the geological morphology of a

stream, the watering of the riparian plant community, the life cycle of fish or invertebrates and the

biodegradation of chemical pollutants can be characterized as effective or trivial based upon established

dependencies between harm to physical, chemical and biological integrity of the downstream ecosystem

and the values of these four data. For example, in the case of an ecological risk assessment, these

metrics could define the exposure risk of a target organism to a chemical stressor (EPA 1998).

Any hypothesis of a upstream disturbance cause and downstream disintegrative effect can be tested for

Murphy Comments Page 91
Individual comments from members of the SAB Panel for the Review of the EPA Water Body Connectivity Report. 

These comments do not represent consensus SAB advice or EPA policy.

scientific significance using these four parameters, in addition to, or combination with, other factors

specific to the target population. These four parameters establish the temporal scale of scientific

significance, in this case, and it is the lack of this fundamental ecological concept that causes the

Proposed Rule to be flawed.

Where the spatial scale is conflated with the temporal scale, these flaws become even more damaging.

For example, on page FR22263 and subsequent pages the term ‘floodplain’ is defined as:

“. . . an area bordering inland or coastal waters that was formed by sediment deposition

from such water under present climatic conditions and is inundated during periods of moderate

to high water flows.”

- FR, vol.79, no.76, p.22263

While this definition might work for a casual description of a local stream, it is not otherwise

useful. This definition would include my backyard - - far outside of the hydrologically defined

floodplain of my local watercourse (Painted Hills Wash), inundated by water as I type this because

of a cloudburst. Such a definition would have no scientific utility unless there was a way to incorporate

a temporal and spatial scale for the disturbing ‘high water flow’ that would exclude a summer 

thunderstorm.

The curious thing about the Proposed Rule is that the need to establish the disturbance scale and its

scientific significance to downstream traditional waters is discussed in the section on ‘adjacent’ and

‘other’ waters. There is no scientific justification presented in the Proposed Rule to explain this abrupt

shift away from the dichotomous definition of connectivity used elsewhere. For example, the preamble 

states:

“Examples of confined surface water hydrologic connections that demonstrate adjacency are

swales, gullies, and rills. The frequency, duration, and volume of flow associated with these

confined surface connections can vary greatly depending largely on factors such as

precipitation, snowmelt, landforms, soil types, and water table elevation. It is the presence of

this hydrologic connection which provides the opportunity for neighboring waters to influence

the chemical, physical, or biological integrity of (a)(1) through (a)(5) waters.”

- FR, vol.79, no.76, p.22210

This statement admits that disturbance parameters (‘frequency, duration, and volume of flow’) and

other spatially and temporally variable factors (‘precipitation, snowmelt, landforms, soil types, and

water table elevation’) provide the opportunity for influence, not the simple existence of a channel

(i.e., swales, gullies or rills), which in this case are exempted by rule.

Murphy Comments Page 92
Individual comments from members of the SAB Panel for the Review of the EPA Water Body Connectivity Report. 

These comments do not represent consensus SAB advice or EPA policy.

Further, on page FR22214, the preamble states, in reference to ‘other waters:’

“When evaluating an ‘‘other water’’ individually or cumulatively for the presence of a significant

nexus to an (a)(1) through (a)(3) water, there are a variety of factors that can be considered that

will influence the chemical, physical, or biological connections the ‘‘other water’’ has with

the downstream (a)(1) through (a)(3) water. The likelihood of a significant connection is greater

with increasing size and decreasing distance from the identified (a)(1) through (a)(3) water,

as well as with increased density of the ‘‘other waters’’ for ‘‘other waters’’ that can be

considered in combination with similarly situated waters.”

- FR, vol.79, no.76, p.22202

The preamble then goes into specifics on the physical, chemical and biological basis for determining

the ‘likelihood of significant connection,’ which in each case resembles a simplistic disturbance

analysis conducted to ascertain the scientific significance of a cause-effect hypothesis for an aquatic

ecosystem.

Such a ‘likelihood of significant connection’ is well understood and utilized across regulatory science,

including EPA's National Center for Environmental Assessment (NCEA). NCEA is a professional

leader in research on the quantitative and predictive risk-based effects of human disturbance on

ecosystems. It is inconceivable that the Proposed Rule would have no input from the nearly 40 years

of connective ecological risk research conducted by NCEA.

The consequences of measurable effects due to disturbance are also well researched by EPA, under

the Office of Water, Water Quality Standards and Criteria program. Water quality criteria are an

explicit result of measuring what constitutes a scientifically significant nexus between a surface water

pathway exposure and a resident aquatic species. There is no better way of assessing the impact of a

watershed connection than its potential to degrade the water quality of receiving waters or violate water

quality standards for those waters. Yet no reference to either water quality standards or the science

for setting them appears in the Proposed Rule.

There is no scientific justification for applying case-by-case jurisdiction to ‘adjacent’ and ‘other’ waters

and not applying it to all potentially jurisdictional waters. The SAB review suggested that the EPA

apply a pathway model to establish a scientifically significant nexus, to wit:

“The conceptual framework in the Connectivity Report should generally express the importance

of climate, geology (surface and subsurface), topographic relief, and biology on flow and

transport. The resulting three-dimensional structure should show potential surface, near surface,

and subsurface pathways, which then can be analyzed in terms of hydrological, chemical, and

biological connectivity in four dimensions (i.e., with the temporal dimension included).” (EPA

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Individual comments from members of the SAB Panel for the Review of the EPA Water Body Connectivity Report. 

These comments do not represent consensus SAB advice or EPA policy.

2014, Italicized for emphasis)

This is the approach that has been followed by the US Army Corps of Engineers in their jurisdictional

determinations for many years. It is the only way that is compatible with current scientific theory and

practice.

A good example can be found in the arid Southwestern US. It is interesting that the preamble 

specifically mentions the Southwest, to wit:

“Also, in many intermittent and ephemeral tributaries, including dry-land systems in the arid

and semi-arid west, OHWM (ordinary high water mark) indicators can be discontinuous within

an individual tributary due to the variability in hydrologic and climatic influences. The agencies

proposed definition of ‘‘tributary’’ addresses these circumstances and states that waters that

meet the definition of tributary remain tributaries even if such breaks occur.”

- FR, vol.79, no.76, p.22202

The fact is that OHWM indicators are discontinuous because flow paths are discontinuous and

connectivity across them can drop to a near-zero scientific significance. For example, the bed and banks

of the Santa Cruz River are quite clear where Painted Hills Wash leaves my neighborhood and joins

the river and there would be little difficulty in establishing that a disturbance in the wash, which flows

a couple of times a year, has a scientifically significant nexus to the Santa Cruz River ecosystem.

However, the river completely loses all physical, chemical and biological character about 40 miles south

of the wash on the Santa Cruz Flats. According to Webb and co-workers (2014),

“Little if any sediment entrained upstream of Marana (immediately north of Tucson) makes it

through the Santa Cruz Flats to the Gila River, except during rare, large floods. Indeed, most

maps do not show a channel crossing this nearly featureless plain. Most of the time, the lower

Santa Cruz valley functions as a closed basin, with all the water and sediment from the Tucson

Basin trapped on the alluvial plain downstream of Marana.”

Given this, it is unclear, and scientifically unjustified, why the jurisdictional determination of ‘adjacent

and other waters’ needs to consider the ‘likelihood of significant connection,’ yet the Santa Cruz

River at Tucson is included by rule, as a tributary of the Colorado River, a traditionally navigable

water of the US.

In the case of some waters (probably the vast majority of perennial, intermediate and ephemeral

streams, floodplain and non-floodplain wetlands) a pathway analysis would be simple and beyond

dispute. In other cases, the results would be less clear. These other cases may be the subject of intense

scientific debate. But such is science when it properly serves the public good. Case-by-case evaluation

Murphy Comments Page 94
Individual comments from members of the SAB Panel for the Review of the EPA Water Body Connectivity Report. 

These comments do not represent consensus SAB advice or EPA policy.

may be legally inconvenient; however Nature is rarely respectful of the Law.

1.0 SPECIFIC COMMENTS:

1.1 The proposed rule has defined Waters of the U.S. under the jurisdiction of the Clean

Water Act to mean all tributaries of a traditional navigable water, interstate water, the

territorial seas, or impoundment.

As stated in my introductory comments, the inclusion by rule of all tributaries to traditional navigable

waters is not scientifically justified by the published literature, the Connectivity report or the SAB

review. Inclusion by rule violates the conclusion of the SAB review that connectivity exists as a

gradient of causal phenomena that operate variably over flowpaths, and result in consequential

disturbances in the watershed. These consequences contribute to or harm the integrity of the physical,

chemical and biological functions supporting the affected ecosystem to a highly varied degree. The

scientific significance of these flowpaths is a function of the disturbance scale, which can be

measured in the frequency, duration, predictability, and magnitude of the disturbance. The probability

of such a disturbance having a scientifically significant disintegrative effect on a downstream

ecosystem creates the gradient of connectivity described in the SAB review, as currently used by the

ecological sciences.

1.2 The proposed rule has defined Waters of the U.S. under the jurisdiction of the Clean

Water Act to mean all waters, including wetlands, adjacent to a traditional navigable

water, interstate water, the territorial seas, impoundment, or tributary.

The definition of and inclusion by rule of adjacent waters also is inconsistent with the published

literature, the Connectivity report or the SAB review. Once again, the concepts of ‘connectivity,’ ‘spatial

and temporal scale,’ ‘connective flowpaths,’ ‘disturbance ecology’ and ‘ecological function’ are

implicitly defined as dichotomous conditions or parameters and this violate the idea of a gradient in

connectivity that is found throughout the SAB and at the heart of ecological theory and practice. The

definition of significant nexus used in the Proposed Rule is scientifically flawed and does not employ

modern concepts of scientific significance and statistical inference.

1.3 The proposed rule has defined Waters of the U.S. under the jurisdiction of the Clean

Water Act to mean, on a case-specific basis, other waters including wetlands, provided

that those waters alone, or in combination with other similarly situated waters, including

wetlands, located in the same region, have a significant nexus to a traditional navigable

water, interstate water, or the territorial seas.

This part of the Proposed Rule has the closest conformity to existing scientific practice, admitting in

numerous places the validity of the conclusions of the SAB review that connectivity is a gradient

Murphy Comments Page 95
Individual comments from members of the SAB Panel for the Review of the EPA Water Body Connectivity Report. 

These comments do not represent consensus SAB advice or EPA policy.

and not dichotomous property of a watershed and that jurisdiction by rule is not scientifically valid.

The suggested defeat of EPA in addressing ‘other waters’ is only reasonable given that they did not

take the same approach as the SAB members, namely,

“If the goal of defining and estimating connectivity is to protect downstream waters, the

interpretation must move from a dichotomous, categorical distinction (connected vs. not

connected) towards a gradient approach that recognizes variation in the strength, duration and

magnitude and effect of those connections. The SAB recommends that an integrated systematic

approach be taken to conceptualize the structure and function of non-floodplain wetlands.” (EPA

2014)

which is taken from section 3.8 addressing non-floodplain wetlands (aka ‘other waters’) of the SAB

review. The gradient approach to connectivity is recommended twenty-eight times in the SAB review

and ten times in sections 3.7 and 3.8 with regard to other waters. If an approach is used that recognizes

that the temporal and spatial variation in transport properties fundamentally produces this gradient in

connectivity, EPA could define the level of connectivity that would be protective or non-protective of

downstream traditional waters of the US and have a fully workable definition. Stated briefly, a

jurisdiction by rule of ‘other waters’ is intractable because science does not support such a distinction.

1.4 The proposed rule defines other terms and excludes specified waters and features

from the definition of Waters of the U.S. Please comment on the adequacy of the

scientific and technical basis of the other definitions and exclusions.

In general, the excluded waters defined in the Rule seem reasonable but are vague in definition. For

example, it is important to distinguish between artificial or natural systems that are still within the

wastewater treatment train and receiving waters of the US. There is currently no general demarcation

made between treatment wetlands versus receiving waters and this causes a great deal of confusion in

the regulated community. For example, requiring compliance of constructed treatment wetlands to the

same standards as wetlands defined as waters of the US may impede the treatment techniques employed

by the constructed wetlands and degrade their protective function. Once again, the scientifically

significant effect on downstream traditional waters of the US needs to be technically established in

order for this distinction to have meaning, particularly in the case of constructed wetlands that have 

been engineered to be isolated during treatment.

The exclusion of ditches by rule is a good first step. There is some uncertainty about the requirement

that excluded ditches that:

“do not contribute flow, either directly or through another water, to a water identified in 

paragraphs (a)(1) through (4) of this section.”

- FR, vol.79, no.76, p.22263

Murphy Comments Page 96
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These comments do not represent consensus SAB advice or EPA policy.

Once again, this is a dichotomous distinction and is not consistent with either the SAB review or

published scientific opinion. Given enough rain, all ditches have the potential to contribute flow to a

downslope waterbody, even in a topographically closed basin. Thus, it would be impossible to meet

these criteria, unless some gradation, based upon scientifically significant effects, was established in

the Proposed Rule.

It is not obvious why ditches that flow only in response to rainfall runoff, aka ephemeral ditches, are

excluded by rule yet ephemeral streams are included by rule. This seems to imply that there are

mitigating factors in the construction of ditches that make them more protective of downstream waters.

This may be the case; however, without further discussion there is no technical reason in the Proposed 

Rule to presume this, in general. The exclusion of rills and gullies by rule is also an excellent proposal.

Much regulatory and industry effort has been expended on defining rills and gullies, particularly in

the surface mining industry. Some progress has been made on the technical definition of rills and

gullies, aka, temporary erosional features. It is important to understand that there is a distinction between

transitory rills and gullies that lead to a stable, integrated hillslope drainage system and destructive

rills and gullies that indicate faulty slope design or unintended changes in hillslope rainfall/runoff

behavior. It is the latter that usually produces degradation of the physical and biological ecosystem.

Once again, a gradient in the temporal and spatial scale is critical to the definition of a jurisdictional

exclusion by either rule or on a case-specific basis. It is important for the Proposed Rule to define

excluded rills and gullies with temporal and spatial criteria of landscape stability that can be refined by

the agencies in regulation or guideline.

2.0 REFERENCES CITED

Ellison, A.M. (1996). An introduction to Bayesian inference for ecological research and environmental decisionmaking. Ecol. Appl., 6, 1036–1046.

EPA, U.S. Environmental Protection Agency

EPA (1998) Guidelines for Ecological Risk Assessment. U.S. Environmental Protection Agency, Risk Assessment

Forum, Washington, DC, EPA/630/R095/002F

EPA (2013) Connectivity of Streams and Wetlands to Downstream Waters: A Review and Synthesis of the

Scientific Evidence EPA/600/R-11/098B, September 2013, External Review Draft

EPA (2014), Science Advisory Board Draft Report on the Connectivity of Streams and Wetlands to Downstream

Waters: A Review and Synthesis of the Scientific Evidence (7/14/14)

Fisher, S. G. (1983). Succession in streams. In Stream Ecology (pp. 7-27). Springer US.

Murphy Comments Page 97
Individual comments from members of the SAB Panel for the Review of the EPA Water Body Connectivity Report. 

These comments do not represent consensus SAB advice or EPA policy.

Johnson, V. E. (2013). Revised standards for statistical evidence. Proceedings of the National Academy of 

Sciences, 110(48), 19313-19317.

Poff, N. L., Allan, J. D., Bain, M. B., Karr, J. R., Prestegaard, K. L., Richter, B. D., ... & Stromberg, J.

C. (1997). The natural flow regime. BioScience, 769-784.

Resh, V. H., Brown, A. V., Covich, A. P., Gurtz, M. E., Li, H. W., Minshall, G. W., ... & Wissmar, R. C. (1988). The

role of disturbance in stream ecology. Journal of the North American Benthological Society, 433-455.

Stanley, E. H., Powers, S. M., & Lottig, N. R. (2010). The evolving legacy of disturbance in stream ecology:

concepts, contributions, and coming challenges. Journal of the North American Benthological Society, 29(1),

67-83.

Webb, R.H., J.L. Betancourt, R.R. Johnson, R.M. Turner. (2014) Requiem for the Santa Cruz: An Environmental

History of an Arizona River, The University of Arizona Press, Tucson, AZ, xvi+296 pp.

Murphy Comments Page 98
Individual comments from members of the SAB Panel for the Review of the EPA Water Body Connectivity Report. 

These comments do not represent consensus SAB advice or EPA policy.

Statement added for clarification: Responding to the DFO’s request to modify comments, if

necessary, I don’t wish to change any of the preceding comments; however, I do wish to respond to one

comment made by a fellow SAB member. During the discussion of issue 1, regarding tributaries to navigable

waters, Dr. Josselyn was asked if he could provide any scientific papers that supported the idea that headwater

streams in the arid West were ‘not important’ to downstream waters. I think both Dr. Josselyn and I were

taken aback since this question suggested such a fundamental misunderstanding of our shared position - - that

it was scientifically unsupported to claim that ALL headwater streams, particularly in the arid West, had a 

significant nexus with downstream waters. Disagreement with this claim certainly does not include the

converse to the Proposed Rule, that NO headwater streams have a significant nexus to downstream waters.

Some do and some clearly do not.

As both Dr. Josselyn and I pointed out in our comments, the SAB report and the ecological literature consistently

indicate that connectivity exists on a gradient and for the arid West, because of the abundance of ephemeral

streams, that gradient varies strongly in space and time. This ecological fact differs fundamentally from studies of

the more mesic regions of the country, for example, Hubbard Brook Experimental Forest (Fisher et al 1982, Graf

1988, Benke 2000, Osterkamp & Friedman 2000, Stromberg 2001, RWRD 2002, Levick et al 2008, Arriana Brand 

2011). This variation occurs in the magnitude, duration, frequency and predictability of flow in ephemeral

streams and creates a strong gradient in the effects of headwater ephemeral streams on downstream 

jurisdictional waters.

The misapprehension of this fact by EPA in developing the rule is suggested in the Power Point slide presented 

in the August 21st teleconference, which stated:

‘Streams are “hydraulic highways” transporting materials, chemicals, organisms’

No, they are not. Streams, and particular watersheds, are not unbroken transport engines, regularly

churning out water and nutrients. I would point out that the ‘streams as highways,’ analogy is the kind of

simplistic thinking that brought the country such ecological disasters as the Los Angeles River, the

Peripheral Canal and the Kissimmee River. Watersheds are better served by the Gaia analogy, a living

organism, constantly adapting to changes in weather and geology. In the arid West, streams reflect a 

quite different geographical environment than the White Mountains of New Hampshire.

In summary, while ephemeral headwater streams in the arid West are always ‘important,’ their effects on

downstream waters are scaled by temporal and spatial variability in the transport of mass and energy and the

magnitude, frequency, duration and predictability of flow events. This variation supplies the scientific basis of 

their significance to downstream jurisdictional waters. For this reason, inclusion by rule of all ephemeral

tributaries, ‘regardless of size or flow duration,’ is not scientifically justified.

Murphy Comments Page 99
Individual comments from members of the SAB Panel for the Review of the EPA Water Body Connectivity Report. 

These comments do not represent consensus SAB advice or EPA policy.

Dr. Duncan Patten

Patten Response to Questions Re: Scientific adequacy of draft policy of Waters of the US. 

Question 1 response. The development of scientific support for there being a significant nexus between 

tributaries and traditional “waters” is more than adequate. The proposed rule explains how tributaries both 

individually and in aggregate can influence the physical, chemical and biological integrity of traditional 

waters. This is true as the tribs are shown to be an integral part of the watersheds that “feed” traditional 

waters. The science demonstrates that this is true whether the tributaries are perennial, intermittent or 

ephemeral.

Question 2 response. The significant nexus related to adjacent waters (including wetlands) to traditional 

waters is based on the science of hydrology and the demonstration of shallow aquifer connections. Without 

the shallow aquifer connections the wetlands would tend to fall into the “isolated” wetlands category and not 

be connected. Ecological science shows limited biological connections but these are important aspects of the 

connectivity and can be demonstrated scientifically through studies of the hyporheic zone.

Question 3 response. This description of a significant nexus of other waters that have to be considered on a 

case-specific basis requires a strict understanding of the actual connection that can be satisfied through 

relationships to other waters. Without the significant nexus which requires a thorough understanding of 

physical, chemical or biological connectivity, the connection will not hold. Thus, the qualifier of this 

condition is the need for scientific studies of each case and a general discussion of significant nexus in the 

policy and its supporting science is inadequate. 

Question 4 response. The exclusion of specified waters in the policy where that exclusion occurs is generally 

sound and the science that supports these exclusions is also adequate to make such exclusions. Most of the 

exclusions are not interstate waters and are modified by human activity. Where modifications are made of 

traditional waters, those waters continue to be considered Waters of the US and though scientific studies 

might show the connectivity has been altered the status remains. 

Question 5 response. The following text was prepared during a general review of the draft policy and might 

have several points that can be used in the discussion of the scientific adequacy of the policy. 

General Comments:

The document uses the scientific foundation established in the “review of literature” document reviewed 

by the SAB panel. This whole document was included in the Federal Register document for draft policy. 

The document also bases some of its recommendations on interpretations of the several US Supreme 

Court decisions, thus both science and legal standing are a foundation of the draft policy. 

The document lists what are recognized presently as Waters of US, i.e., interstate waters, navigable 

waters, tidal waters...how other waters relate to these, i.e., physical, biological and chemical influence

(i.e., “connections to and interactions with”). These are then used to define and explain what are or will 

be considered Waters of US in the future and thus open to regulation. 

The importance of the aggregated influence by water bodies on recognized Waters of the US is used 

throughout the document and science is used as the foundation for this. This, along with use of 

Patten Comments Page 100
Individual comments from members of the SAB Panel for the Review of the EPA Water Body Connectivity Report. 

These comments do not represent consensus SAB advice or EPA policy.

watershed as a spatially integrating entity, ecologically helps expand the concept of what might be 

defined as Waters of the US. 

The document lists many water bodies that are not considered Waters of US and justification (science 

and legal) for these exclusions is sound and adds strength to justification for those water bodies that are 

included under this new policy. 

In an attempt to explain “significance”, which is described as a non-scientific term “in light of law and 

science”, the document side steps to the use of “relative strength of downstream effects” to inform 

conclusions of significance; however, there is no clear explanation of what “relative strength” means or 

how it might be developed or determined. One assumes that use of “information” from the scientific 

literature review will address this, but this is not clear and a gradient of strength of connection should be 

developed as an influence of a water body on recognized Waters of the US that is small may be as 

important as one that is great. 

Later in the document, “significant nexus” is explained as waters (including wetlands), either alone or in 

combination that significantly affects chemical, biological or chemical integrity of recognized Waters of 

US. Use of “significantly” in the definition of “significant nexus” is bothersome and there is little or no 

explanation (science or legal) of what “significant effect” means. 

The document offers good and sound explanations of chemical, physical and biological connectivity 

which support other discussion points on these issues. Under physical connectivity there is some 

mention of “depth to water table” which is not clear. Under biological connectivity emphasis is placed 

on “life cycle dependency” on the aquatic resource which rightly eliminates many biological 

connections that are transitory, such as migratory birds that have no life cycle dependency of the water 

body. 

Specific Comments:

Tributaries as Waters of the US. The document presents several ways nearly all tributaries are 

included as waters of the US and answers its own question of “why conclude all tributaries are Waters of 

the US?” These include: 

A. Those the flow directly into recognized Waters of US.

B. Those that flow into or through tributaries included in A above. 

C. Those that in aggregate influence the Waters of US. 

When tributaries are considered “Waters of US”, the document uses both science and legal concepts of 

“significant nexus” to demonstrate that the tributaries can be perennial, intermittent or ephemeral. This 

is a legitimate use of these water types as they all are scientifically shown to influence the physical, 

chemical or biological integrity of recognized Waters of US. This is explained in the text and 

demonstrated in the literature review. The importance of their being included as Waters of US is 

supported when the document states “the effects of small water bodies in a watershed need to be 

Patten Comments Page 101
Individual comments from members of the SAB Panel for the Review of the EPA Water Body Connectivity Report. 

These comments do not represent consensus SAB advice or EPA policy.

considered in aggregate” which emphasizes the importance of integration of effects from several water 

bodies. The proposed definition of waters of the US also emphasizes the importance of tributaries that 

“flow directly or indirectly” to a recognized water of the US. These waters would become “Waters of 

the US”... this legitimately builds on the concept of tributaries being Waters of US if they flow into or 

through tributaries that are recognized as “Wters of US”. Science included in the literature review 

section supports this integration of the cumulative effects of several water bodies. 

Other waters: the document mentions that there are “other waters” (than those already described as 

waters of US), which includes tributaries, that may be considered but emphasizes that these will be 

considered on a case specific basis. The use of case specific approach was much more common in 

earlier definitions of Waters of US and thus those being considered on a case-specific basis are fewer 

than earlier. 

Concept of “adjacent” and/or “neighbor” appears to be used to support wetlands and riparian areas that 

are next to Waters of US, especially if there are shallow subsurface hydrological connections. This 

concept is confusing as in the past riparian areas were not included as “waters of US”, so does this mean 

that they will be in the new policy? Wetlands as sources of water of parts of tributaries do become 

“Waters of US” under new policy. This is scientifically defensible because they are influencing 

hydrology and ecology of recognized Waters of US. 

Ditches. The document discusses ditches that are not excluded. One such ditch, those with perennial 

flow is included but the source of this perennial flow should be considered as a part of accepting this 

kind of ditch as a Water of US. 

Other water bodies mentioned: Playa lakes are discussed. They are excluded unless they are interstate 

bodies of water. This appears to be the only way “geographically isolated wetlands” are included under 

Waters of the US. These types of waters are fully described in Tiner’s Wetland paper, “Geographically 

Isolated Wetlands of the United States” which describe the importance of these water bodies but also 

their isolation from recognized waters of the US. Is there science (hydrologic and/or ecologic) that 

should be considered that may make some of these isolated waters (wetlands) Waters of the US in 

addition to the interstate rule?

Patten Comments Page 102
Individual comments from members of the SAB Panel for the Review of the EPA Water Body Connectivity Report. 

These comments do not represent consensus SAB advice or EPA policy.

Dr. Mark Rains

Comments of the Proposed Definition of Waters of the United States

These comments are focused on and organized around the proposed definition of Waters of the United States, 

hereafter referred to as waters of the US. However, these comments in many cases resonate throughout the 

other sections of the proposed rule.

Summary

In general, the proposed rule is well-reasoned and adheres to the core conclusions in Connectivity of Streams 

and Wetlands to Downstream Waters: A Review and Synthesis of the Scientific Evidence (EPA/600/R-11/098B, 

September 2013, External Review Draft), hereafter referred to as the Connectivity Report. To date, the SAB has 

recommended numerous revisions to the Connectivity Report. These recommended revisions are largely aimed 

at strengthening the Connectivity Report, rather than at changing the core conclusions of the Connectivity 

Report. Therefore, the proposed rule does not require major revisions. However, there are remaining issues that 

could be better addressed in the proposed rule and therefore better enable to regulated community to 

understand the scope of the proposed rule.

Type (a)(1) Waters: Traditional Navigable Waters

The Constitution and legal statutes provide clear authority for the federal government to regulate this type of 

water of the US. No further comment is offered.

Type (a)(2) Waters: Interstate Waters

The Constitution and legal statutes provide clear authority for the federal government to regulate this type of 

water of the US. No further comment is offered.

Type (a)(3) Waters: Territorial Seas

The Constitution and legal statutes provide clear authority for the federal government to regulate this type of 

water of the US. No further comment is offered.

Type (a)(4) Waters: Impoundments

The Connectivity Report and other literature clearly establish that impounding waters affects the chemical, 

physical, and biological integrity of both downgradient and upgradient waters. Downgradient effects are well 

established in the literature, with fundamental effects on ecosystem structure and function extending well 

downstream of the impoundment (e.g., Ward and Stanford 1995; Stanford and Ward 2001). In the upgradient 

direction, impoundments obviously inundate the impounded area, but also can have substantive effects further 

upgradient of the impounded area, such as raising groundwater and changing vegetation in adjacent wetland 

areas (e.g., Rains et al., 2004) and restricting upstream migration of anadromous fish (Raymond 1979). 

Therefore, there is a well-established and well-reasoned justification for defining these waters as waters of the 

US.

Type (a)(5) Waters: Tributaries

Rains Comments Page 103
Individual comments from members of the SAB Panel for the Review of the EPA Water Body Connectivity Report. 

These comments do not represent consensus SAB advice or EPA policy.

The Connectivity Report and other literature clearly establish that tributaries affect the chemical, physical, and 

biological integrity of downgradient waters. However, the definition of tributary remains somewhat unclear. 

This is typical of any effort to classify continuous landscapes (e.g., flowpaths from ridges to reefs) into discreet 

categories (e.g., hillslopes, headwater streams, mainstem rivers, nearshore marine environments). Still, this is an 

extremely important classification, especially on the upgradient edge where there is a transition from “not a 

water of the US” (e.g., hillslope) to “water of the US” (e.g., tributary). This “edge”, of course, is not an edge at all 

– rather, it is a transitional area that changes in time. 

The time element is particularly problematic, because the areas over which runoff is generated change in time. 

These “variable source areas” expand and contract and therefore change the way that landscapes connect 

through storms and seasons (Dunne and Black 1970). This has particularly important implications in regards to 

both infiltration-excess and saturation-excess overland flow, both of which being highly variable in space and 

time. It is through variable source area expansion and contraction that waters can be surface-water isolated at 

times to being the headward extent of tributaries at other times (e.g., Rains et al. 2008). In many landscapes, 

especially the arid and semi-arid western US, these intermittent or ephemeral connections are critical, providing 

much of the connectivity that facilitates the transport of mass, energy, and organisms to downgradient waters 

(e.g., Izbicki 2007).

Given these complexities, I think it important to clearly define the headward extent of tributaries. The proposed 

rule tries to do so, and does an admirable job of trying to draw that bright line. However, I think it important for 

the proposed rule to clearly discuss the difficulty of drawing such a bright line on a continuous landscape, 

allowing the flexibility to for field personnel to define functional tributaries, even where those functional 

tributaries might lack obvious indicators of bed and bank (e.g., alluvial deposits on the bed of a headwater 

stream in a humid mountain setting) but have less obvious indicators of tributary flows (e.g., directionally bent 

herbaceous vegetation and subtle debris lines in swales connecting vernal pools to downstream waters in arid

and semi-arid settings). One way to do so would be to allow the use of additional indicators and/or field data 

(e.g., stage or flow data, or the equivalent) in the absence of clearly defined bed-and-bank features.

Type (a)(6) Waters: Adjacent Waters

The Connectivity Report and other literature clearly establish that adjacent waters affect the chemical, physical, 

and biological integrity of downgradient waters. However, the Connectivity Report and this proposed rule could 

go a step further, defining adjacent waters as part of the waters to which they are adjacent. Rivers are not just 

channels – rather, rivers are channels and adjacent riparian areas, including all adjacent wetlands (Ward and 

Stanford 1995). Therefore, the proper functioning of the river, and therefore the chemical, physical, and 

biological integrity of downgradient waters, is a function of both channel and adjacent riparian areas, including 

all lateral exchanges of mass, energy, and organisms between the channel and the riparian area. While it may be 

convenient to separately define channels as type (a)(1) or type (a)(5) waters and adjacent wetlands as type 

(a)(6) waters, it is nevertheless important to acknowledge that this is a matter of convenience and that these are 

in fact one continuous and interconnected hydrologic system. Such an explanation would help justify the 

extension of the definition of waters of US to include these adjacent wetlands.

The proposed rule clears some existing confusion as to the meaning of “bordering, contiguous, or neighboring” 

by defining riparian area and floodplain consistent with the literature and common scientific usage and further 

explaining that short, surface and shallow subsurface connections can connect wetlands outside the immediate 

riparian area and/or floodplain to the river. The proposed rule should consider stating that wetlands in the 

riparian area and/or on the floodplain are always adjacent, while wetlands outside the riparian area and the 

floodplain might or might not be adjacent, depending upon a significant nexus determination. (See “Other 

Waters”, below for further discussion about case-by-case decisions.)

Rains Comments Page 104
Individual comments from members of the SAB Panel for the Review of the EPA Water Body Connectivity Report. 

These comments do not represent consensus SAB advice or EPA policy.

Type (a)(7) Waters: Other Waters

The Connectivity Report and other literature clearly establish that other waters can affect the chemical, physical, 

and biological integrity of downgradient waters, though they do so on a gradient from having negligible to 

important effects. The proposed rule therefore will treat these not as waters of the US by definition but, rather, 

as waters of the US on a case-by-case basis if there proves to be a significant nexus between the other wetland 

or group of wetlands and the chemical, physical, and biological integrity of downgradient waters. While the 

science supports this as a general approach, it will be important to carefully define what is meant by “case-bycase”, and what happens following a case in which specific other wetland or group of wetlands are determined 

to be waters of the US.

The proposed rule defines a group of wetlands geographically, grouping wetlands only within a given watershed. 

The proposed rule then defines watershed as all land from which surface water could drain to the nearest single 

entry point to a type (a)(1)-(a)(3) water. Such a definition has some problems. 

There could be innumerable groups on uplands directly adjacent to a linear type (a)(1)-(a)(3) water. Imagine, for 

example, a navigable river running along the toe of a hillslope with innumerable seeps and springs, each of 

which or small groups of which discharging at different single points of entry to the river. Further imagine that 

the seeps and springs are a single hydrologic system, recharging due to infiltration of precipitation at the 

ridgetop and expressing along a linear geologic contact that outcrops at a common elevation all along the 

hillslope. By the proposed definition of watershed, one might conclude that a significant nexus assessment 

would need to be conducted above every single point of entry, thereby conducting a significant nexus 

assessment many times over on the same hydrologic system. This would be a clear waste of effort, because a 

single, well-designed and well-conducted significant nexus assessment would likely suffice. And, if a single, welldesigned and well-conducted significant nexus assessment would likely suffice in the case above, then the 

logical extension might be that a single, well-designed and well-conducted significant nexus assessment might 

also likely suffice for any single type of hydrologic system, if such a type of hydrologic system were well defined. 

Consider, for example, vernal pools in the Sacramento Valley. Both east and west sides of the Sacramento Valley 

are draped with Pleistocene to Pliocene alluvial fans terminating at the Holocene basin floor along the 

Sacramento River. These alluvial fans are nearly level to undulating but gently slope toward the basin floor. They 

have well-developed drainage networks, being dissected by streams and rivers tributary to the Sacramento 

River. Major geologic formations include the Riverbank and Red Bluff formations, with the Riverbank formation 

being 130K-450K BP in age and the Red Bluff formation being 450K-1.08M BP in age (Helley and Harwood, 

1985), both of which being old enough for substantive pedogenic processes to have occurred (Helley and 

Harwood, 1985; Smith and Verrill, 1998). The USDA–Natural Resources Conservation Service has mapped several 

soil series with silica- and iron-cemented duripans on these formations, including the Redding series. These 

formations are also old enough for substantive subaerial erosion to have occurred, so microtopographic relief 

also is well developed, with mound-depression topography and irregular to coherent and intermittent to 

seasonal drainage networks commonly connecting depressions to streams and rivers tributary to the Sacrament 

o River (Smith and Verrill, 1998). The vernal pools and swales that occur on these hardpan soils have been 

extensively studied (e.g., Rains et al. 2006; 2008). Wherever they occur, they have common hydrological, 

geochemical, and biological attributes and processes, with such attributes and processes a function of the 

underlying geologic setting. This geologic setting does not only occur in a small, closely centered area – rather, 

this geologic setting repeats in mappable units all over both sides of the Sacramento Valley. If a significant nexus 

assessment is done on these types of vernal pools in one location, then it quite likely suffices for another 

similarly situated location. 

Rains Comments Page 105
Individual comments from members of the SAB Panel for the Review of the EPA Water Body Connectivity Report. 

These comments do not represent consensus SAB advice or EPA policy.

The summary of this is that case-by-case should not be defined simply by proximity. Such a definition is 

inconsistent with scientific understanding of the controls on hydrological, geochemical, and biological structure 

and function. Such a definition also would place an undue burden on the regulated public, who would be 

required to repeatedly perform significant nexus assessments on the same types of wetlands. It would therefore 

be better to have a clear pathway by which entire classes of wetlands can be determined to have a significant 

nexus with the chemical, physical, and biological integrity of downstream waters and can thereafter be 

considered waters of the US by definition.

Not Waters by Rule

The proposed rule proposes that many features be non-waters by rule. A few of these are concerning. 

The proposal that certain types of ditches be non-waters by rule is particularly concerning. The proposed rule 

proposes that tributaries be waters by definition because the Connectivity Report and other literature clearly 

establish that tributaries affect the chemical, physical, and biological integrity of downgradient waters. Any ditch 

connected to any water of the US effectively acts like a tributary, whether it is a channelized natural tributary or 

a ditch wholly excavated in uplands (e.g., Jones and Grant 1996). I can appreciate the political difficulty of 

extending CWA jurisdiction to these waters, and the economic hardship that such extension of jurisdiction could 

place on the regulated public. However, I would be remiss if I didn’t point out that any decision to not cover 

these types of ditches is wholly a policy decision and completely unsupported by scientific evidence.

The proposal that groundwaters be non-waters by rule, though consistent with past interpretations, remains 

troubling. Globally, the total volume of groundwater exceeds the total volume of surface water by nearly two 

orders of magnitude (Fetter 2001). Groundwater contributes approximately half of the annual streamflow, 

though precise contributions vary widely and range from 14% to 90% (Winter et al. 1998). Furthermore, 

groundwater comprises ~20% of the total annual withdrawals nationwide, and upwards towards 100% in many 

specific regions (Kenny et al. 2009). Therefore, it is incomprehensible that the chemical, physical, and biological 

integrity of the nation’s waters could be protected and the national goal that all waters of the US could be 

fishable and swimmable could be achieved without also extending CWA protections to groundwaters. Again, I 

can appreciate the political difficulty of extending CWA jurisdiction to these waters, and the economic hardship 

that such extension of jurisdiction could place on the regulated public. I also appreciate that groundwaters are 

protected under other federal statutes, such as the Safe Water Drinking Act and the Superfund Act. However, 

again, I would be remiss if I didn’t point out that any decision to not cover groundwaters is wholly a policy 

decision and completely unsupported by scientific evidence. I also nevertheless strongly recommend that they 

continue to be used to extend connectivity to certain surface-water isolated features. Such connections are the 

rule rather than the exception, and play critical roles in facilitating the exchange of water and dissolved 

constituents between different waters (Rains et al. 2006).

References

Dunne, T, Black, RD. (1970) Partial area contributions to storm runoff in a small New England watershed. Water 

Resources Research 6:1296-1311.

Fetter CW (2001) Applied Hydrogeology, 3d ed. Prentice Hall, Upper Saddle River, New Jersey.

Helley EJ, Harwood DS. 1985. Geologic Map of Late Cenozoic Deposits of the Sacramento Valley and Northern 

Sierran Foothills, California. U.S. Geological Survey, Miscellaneous Field Studies Map MF-1790. U.S. Government 

Printing Office, Washington, DC.

Rains Comments Page 106
Individual comments from members of the SAB Panel for the Review of the EPA Water Body Connectivity Report. 

These comments do not represent consensus SAB advice or EPA policy.

Izbicki JA (2007) Physical and temporal isolation of headwater streams in the Western Mojave Desert, Southern 

California. Journal of the American Water Resources Association 43:26-40.

Jones JA, Grant GE (1996) Peak flow responses to clear-cutting and roads in small and large basins, western 

Cascades, Oregon. Water Resources Research 32:959-974.

Kenny JF, Barber NL, Hutson SS, Linsey KS, Lovelace JK, Maupin MA (2009) Estimated Use of Water in the United 

States in 2005. US Geological Survey Circular 1344.

Rains MC, Mount JF, Larsen EW (2004) Simulated changes in shallow groundwater and vegetation distributions 

under different reservoir operations scenarios. Ecological Applications 14:192-207.

Rains MC, Fogg GE, Harter T, Dahlgren RA, Williamson RJ (2006) The role of perched aquifers in hydrological 

connectivity and biogeochemical processes in vernal pool landscapes, Central Valley, California. Hydrological 

Processes 20:1157-1175.

Rains MC, Dahlgren RA, Williamson RJ, Fogg GE, Harter T (2008) Geological control of physical and chemical 

hydrology in vernal pools, Central Valley, California. Wetlands 28:347-362.

Raymond HL (1979) Effects of dams and impoundments on migrations of juvenile chinook salmon and steelhead 

from the Snake River, 1966 to 1975. Transactions of the American Fisheries Society 108:505-529.

Smith DW, Verrill, WL. 1998. Vernal pool-soil-landform relationships in the Central Valley, California. Pages 15-

23 in: Witham CW, Bauder ET, Belk D, Ferren Jr. WR, Ornduff R (eds), Ecology, Conservation,

and Management of Vernal Pool Ecosystems – Proceedings from a 1996 Conference, California Native Plant 

Society, Sacramento, California.

Stanford JA, Ward JV (2001) Revisiting the serial discontinuity concept. Regulated Rivers: Research & 

Management 17:303-310.

Ward JV, Stanford JA (1995) The serial discontinuity concept: extending the model to floodplain rivers. 

Regulated Rivers: Research & Management 10:159-168.

Winter TC, Harvey JW, Franke OL, Alley WM (1998) Ground Water and Surface Water: A Single Resource. US 

Geological Survey Circular 1139.

Rains Comments Page 107
Individual comments from members of the SAB Panel for the Review of the EPA Water Body Connectivity Report. 

These comments do not represent consensus SAB advice or EPA policy.

Dr. Amanda Rodewald

Comments on scientific basis for rule – A. Rodewald

1. The proposed rule has defined Waters of the U.S. under the jurisdiction of the Clean Water Act 

to mean all tributaries of a traditional navigable water, interstate water, the territorial seas, or 

impoundment. This definition is based on the conclusion that a significant nexus exists between 

tributaries (as defined in the proposed rule) and the traditional navigable waters, interstate 

waters, and the territorial seas into which they flow. Please comment on the adequacy of the 

scientific and technical basis of this proposed definition. 

The scientific literature does support the idea that tributaries greatly impact the physical, chemical, and 

biological integrity of downstream waters through a wide variety of processes, including supplying 

water to rivers & other waters, transport of sediment and organic matter, provide habitat, and nutrient 

spiraling. In addition, most jurisdictional waters are fed by tributaries, many of which are intermittent 

in certain regions. In a report currently undergoing quality review by the Chartered SAB, the 

Connectivity Panel agreed that the scientific literature provided strong support that ephemeral, 

intermittent, and perennial streams have important downstream effects, and that connectivity occurs 

along a gradient determined by the frequency, duration, magnitude, predictability, and consequences of 

stream, watershed, and landscape processes. Although connectivity can vary among streams, the 

consequences of connectivity for the physical, chemical, and biological integrity of downstream waters 

are sufficiently strong that streams can be justifiable viewed as a category. For example, even short 

duration and highly episodic flow connections and/or long periods of dry conditions could be important 

to downstream waters. Based on the Panel’s recent deliberations, the ruling that tributaries remain 

jurisdictional even with natural or human-caused interruptions seems consistent with the science even 

though interrupted streams also can show high variability in the degree of connectivity. 

One concern that I have relates to what seems to be different definitions of tributary used in the 

scientific review and the rule. The scientific review focused on perennial, ephemeral, and intermittent 

streams, whereas the rule seems to include a wide range of waters, including lakes, ponds, ditches, and 

impoundments. In the below text excerpted from the proposed rule, I have underlined two sentences 

that seem to expand what is commonly thought of as a tributary to any type of water. This definition 

confused me because the extent to which non-stream waters are jurisdictional seems to be addressed 

under adjacent waters. 

“Tributary: a water physically characterized by the presence of a bed and banks and ordinary high water mark, which 

contributes flow, either directly or through another water, to a water identified in paragraphs a1-a4. In addition, wetlands, 

lakes, and ponds are tributaries (even if they lack a bed and banks or ordinary high water mark) if they contribute flow, 

either directly or through another water to a water identified in paragraphs a1-a3. A water that otherwise qualifies as a 

tributary under this definition does not lose its status as a tributary if, for any length, there are one of more man-made breaks 

(e.g., culverts, dams, pipes, bridges) or one or more natural breaks (e.g., wetlands, debris piles, boulder fields) so long as a 

bed and banks and an ordinary high water mark can be identified upstream of the break. A tributary, including wetlands, 

can be a natural, man-altered, or man-made water and includes waters such as rivers, streams, lakes, ponds, impoundments, 

canals, and ditches not otherwise excluded.”

2. The proposed rule has defined Waters of the U.S. under the jurisdiction of the Clean Water Act 

to mean all waters, including wetlands, adjacent to a traditional navigable water, interstate water, 

the territorial seas, impoundment, or tributary. This definition is based on the conclusion that a 

Rodewald Comments Page 108
Individual comments from members of the SAB Panel for the Review of the EPA Water Body Connectivity Report. 

These comments do not represent consensus SAB advice or EPA policy.

significant nexus exists between adjacent water bodies (as defined in the proposed rule) and 

traditional navigable waters, interstate waters, and the territorial seas. Please comment on the 

adequacy of the scientific and technical basis of this proposed definition. 

The Connectivity Panel supported the conclusion in the EPA’s report that floodplain wetlands and 

waters have strong impacts on the physical, chemical, and biological integrity of downstream waters. 

Wetlands and waters in floodplain settings are important buffers to pollution and nutrients, provide 

habitat, and retain sediments and nutrients and contaminants. This warrants the consideration of waters 

and wetlands in floodplain settings as a class falling under CWA jurisdiction. 

As noted above, there was a mismatch between the definition of adjacent waters used in the rule and the 

floodplain settings in the review document. I assume that floodplain waters and wetlands are one type 

of adjacent water (i.e., neighboring and floodplain definitions), but not all of them. 

3. The proposed rule has defined Waters of the U.S. under the jurisdiction of the Clean Water Act 

to mean, on a case-specific basis, other waters including wetlands, provided that those waters 

alone, or in combination with other similarly situated waters, including wetlands, located in the 

same region, have a significant nexus to a traditional navigable water, interstate water, or the 

territorial seas. Please comment on the adequacy of the scientific and technical basis of this 

proposed definition. 

The Connectivity Panel disagreed with the EPA Report’s conclusion that the literature did not provide 

sufficient information to evaluate or generalize about the degree of connectivity or its downstream 

consequences. As such, the Panel requested better acknowledgement that the science does show that

non-floodplain waters and wetlands can have strong and important impacts on the physical, chemical, 

and biological integrity of downstream waters. 

The Connectivity Panel agreed that downstream consequences of waters and wetlands in non-floodplain 

settings will likely require a case-by-case evaluation that considers the magnitude, duration, frequency, 

predictability, and consequences of water, material, and biotic fluxes to downstream waters, and their 

impact on the integrity of downstream waters. An additional recommendation was to establish relevant 

guidelines identifying baseline temporal intervals that are likely to meaningfully connect non-floodplain 

wetlands and waters to downstream waters. 

I’m unclear about the jurisdiction of wetlands that have a surface or subsurface water connection 

(italicized text from draft rule below). If a wetland in a non-floodplain setting has a connection to the 

river network, then is it a tributary or an “other water”? Or is seeing the connection effectively the 

“case-specific analysis” needed to make it jurisdictional?

Regarding wetlands and open waters located outside of floodplains and riparian areas, the Report finds that

they provide many benefits to rivers, lakes, and other downstream waters. If the wetland or open water has a

surface or shallow subsurface water connection to the river network, it affects the condition of downstream

waters. Where the wetland or open water is not connected to the river network through surface or shallow

subsurface water, the type and degree of connectivity varies geographically, topographically, and

ecologically, such that the significance of the connection is difficult to generalize across the entire group of

waters.

Rodewald Comments Page 109
Individual comments from members of the SAB Panel for the Review of the EPA Water Body Connectivity Report. 

These comments do not represent consensus SAB advice or EPA policy.

There was strong agreement among Panel members that connectivity assessments should explicitly 

consider aggregate and cumulative effects of wetland complexes. I was pleased to see that the rule 

provided guidance about how and when to aggregate with the phrase “similarly situated”. 

“Other waters’’ will be evaluated either individually, or as a group of waters where they are determined to be similarly 

situated in the region. Waters are similarly situated where they perform similar functions and are located sufficiently close 

together or when they are sufficiently close to a jurisdictional water. How these ‘‘other waters’’ are aggregated for a casespecific significant nexus analysis depends on the functions they perform and their spatial arrangement within the ‘‘region’’

or watershed. For other waters that perform similar functions, their landscape position within the watershed (i.e., the 

‘‘region’’) relative to each other or to a jurisdictional water is generally the determinative factor for aggregating waters in a 

significant nexus analysis, which will focus on the degree to which the functions provided by those ‘‘other waters’’ affect the 

chemical, physical, or biological integrity of (a)(1) through (a)(3) waters and whether such effects are significant.”

The similarly-situated case for aggregation requires similar functions, but what if there is a wetland 

complex where some wetlands are connected and others are important for storage due to lack of 

connection?

“A hydrologic connection is not necessary to establish a significant nexus, because, as Justice Kennedy stated, in some cases 

the lack of a hydrologic connection would be a sign of the water’s function in relationship to the traditional navigable water, 

interstate water or the territorial seas. These functional relationships include retention of flood waters or pollutants that 

would otherwise flow downstream to the traditional navigable water, interstate water or the territorial seas.”

I support the Agency’s consideration of using subcategories that identify groups for which there is 

evidence of strong connections and thus should be jurisdictional. 

I appreciate that they are trying to provide guidance on how to evaluate different kinds of connectivity, 

but these are largely describing how to identify the presence or absence of different “types” of 

connections, rather than the degree of those connections. (below)

p. 22214: 

Evidence of chemical connectivity and the effect on waters can be found by identifying: Whether the properties of the water 

in question are similar or dissimilar to an identified (a)(1) through (a)(3) water; signs of retention, release, or 

transformation of nutrients or pollutants; and the effect of landscape position on the strength of the connection to the nearest 

‘‘water of the United States,’’ and through it to an (a)(1) through (a)(3) water. In addition, relevant factors influencing 

chemical connectivity include hydrologic connectivity (see physical factors, below), surrounding land use and land cover, the

landscape setting, and deposition of chemical constituents (e.g. acidic deposition).

Evidence of physical connectivity and the effect on (a)(1) through (a)(3) waters can be found by identifying evidence of 

physical connections, such as flood water or sediment retention (flood prevention). Presence of indicators of hydrologic 

connections between the other water and jurisdictional water are also indictors of a physical connection. Factors influencing

physical connectivity include rain intensity, duration of rain events or wet season, soil permeability, and distance of 

hydrologic connection between the ‘‘other water’’ and the (a)(1) through (a)(3) water, depth from surface to water table, and

any preferential flowpaths.

Evidence of biological connectivity and the effect on waters can be found by identifying: resident aquatic or semi-aquatic 

species present in the ‘‘other water’’ and the tributary system (e.g., amphibians, aquatic and semi-aquatic reptiles, aquatic 

birds); whether those species show life-cycle dependency on the identified aquatic resources (foraging, feeding, nesting, 

breeding, spawning, use as a nursery area, etc.); and whether there is reason to expect presence or dispersal around the 

‘‘other water,’’ and if so whether such dispersal extends to the tributary system or beyond or from the tributary system to the 

‘‘other water.’’ Factors influencing biological connectivity include species’ life history traits, species’ behavioral traits, 

dispersal range, population size, timing of dispersal, distance between ‘‘other water’’ and an (a)(1) through (a)(3) water, the 

Rodewald Comments Page 110
Individual comments from members of the SAB Panel for the Review of the EPA Water Body Connectivity Report. 

These comments do not represent consensus SAB advice or EPA policy.

presence of habitat corridors or barriers, and the number, area, and spatial distribution of habitats. Non-aquatic species or 

species such as non-resident migratory birds that are not demonstrating a life cycle dependency on the identified aquatic 

resources are not evidence of biological connectivity for purposes of this rule”

4. The proposed rule defines other terms and excludes specified waters and features from the 

definition of Waters of the U.S. Please comment on the adequacy of the scientific and technical 

basis of the other definitions and exclusions. 

Tributary – it seems that the definition for tributary includes most types of water, by way of adding the 

two sentences underlined above in the response to question 1. Also on p 22197, the text talks about 

tributary streams, which were the focus of the scientific review, but then the rule adopts the broader 

definition.

How would the categorical exclusion of ditches that do not contribute flow, directly or indirectly, to a 

traditional navigable water affect the outcome of a request to establish a connection? Wouldn’t that be 

important and jurisdictional under tributary definition? However, at the time of impact / construction/ 

alteration, the ditch would be excluded. (p.22194, bottom of 2nd column and top of 3rd column 

recognizes that the significance of certain adjacent waters is to prevent or delay a hydrological 

connection with downstream waters and store water or pollutants) 

p. 22204: I am unclear about the following text. I thought that swales were one of the exclusions? If 

not, does that mean it is a case-specific other water?

“ Non-jurisdictional geographic features (e.g., non-wetland swales, ephemeral upland ditches) may still serve

as a confined surface hydrologic connection between an adjacent wetland or water and a traditional

navigable water, interstate water or the territorial sea, provided there is an actual exchange of water

between those waters, and the water is not lost to deep groundwater through infiltration (i.e., transmission

losses).”

5. If you have any other comments about the adequacy of the scientific and technical basis of the 

proposed rule, please provide them as well. 

p. 22195-22196: It is really important that they articulate that (1) “significance” is not a scientific term 

but rather a determination of the agencies in light of the law and science and (2) the relative strength of 

downstream effects informs the agencies’ conclusions about the significance of those effects for 

purposes of interpreting the CWA.

p. 22199 footnote: is it appropriate to use “in the region” and “watershed” interchangeably? In general, 

regions seem to include many watersheds.

p. 22208: Does the following text mean that connections via groundwater cannot establish connectivity? 

“Shallow subsurface connections are distinct from deeper groundwater connections, which do not satisfy the requirement for 

adjacency, in that the former exhibit a direct connection to the water found on the surface in wetlands and open waters”

p. 22209: Here again, I’m confused b/c it sounds like nothing farther than an adjacent wetland or water will be jurisdictional; 

is that so? “Waters located near an adjacent water but which are not themselves (independently) adjacent to an (a)(1) 

through (a)(5) water would, under the proposed rule, not be regulated under (a)(6). However, waters, including wetlands 

that are adjacent to a wetland that meets the definition of a tributary would be considered adjacent waters.”

Rodewald Comments Page 111
Individual comments from members of the SAB Panel for the Review of the EPA Water Body Connectivity Report. 

These comments do not represent consensus SAB advice or EPA policy.

Dr. Emma Rosi-Marshall

Aug 26, 2014

To Dr. Amanda Rodewald, Chair, Science Advisory Board (SAB) Panel for the Review of the EPA Water 

Body Connectivity Report 

Below are my revised comments on the US EPA proposed rule entitled “Definition of ‘Waters of the 

United States’ Under the Clean Water Act”. As requested in your memorandum dated July 16, 2014, I 

have revised these comments in response to the SAB conference calls in August and now provide final 

comments on “the adequacy of the scientific and technical basis of the proposed rule cited above.” 

Thank you for considering these preliminary comments on the EPA Proposed Rule. 

Specific Charge Questions 

1. The proposed rule has defined Waters of the U.S. under the jurisdiction of the Clean Water Act to 

mean all tributaries of a traditional navigable water, interstate water, the territorial seas, or 

impoundment. This definition is based on the conclusion that a significant nexus exists between 

tributaries (as defined in the proposed rule) and the traditional navigable waters, interstate waters, and 

the territorial seas into which they flow. Please comment on the adequacy of the scientific and technical 

basis of this proposed definition. (lead discussants are: Drs. Emma Rosi-Marshall and Jennifer Tank) 

Response: The proposal includes tributaries in the definition of waters of the United States is based on a 

strong foundation of scientific research. There is ample scientific evidence that tributary streams are 

connected to downstream waters and that these connections can fundamentally influence the biological 

integrity of downstream waters. To reiterate, there is ample scientific evidence that headwater streams 

are not simply connected to downstream waters, but the scientific literature reviewed in the EPA 

Connectivity Report and the follow up comments by the SAB demonstrate that these connections 

strongly influence the physical, chemical and biological integrity of downstream waters. For example, 

the nutrient cycling and removal of nitrogen that occurs in headwater streams reduces the downstream 

inputs of nitrogen to downstream waters (e.g. Mulholland et al. 2008, and others as reviewed in the 

Connectivity Report). Nitrogen pollution is known to be a major contribution to impairment of 

waterbodies due to eutrophication. This is one example, of many, provided in the Connectivity Report 

and the SAB comments on the report, of how headwater streams are not simply connected to 

downstream waters, but that these connections fundamentally influence the integrity of downstream 

waters. The significant nexus determination that tributaries influence the integrity of waters as a policy 

decision is well justified by the best available science. Inclusion of tributary streams in the definition of 

waters the US is based on a large body of scientific knowledge. In addition, effective maintenance 

and/or restoration of the integrity of downstream waters will require protection of these tributary 

systems which feed into downstream waters. 

The scientific and technical basis for the inclusion of tributaries is based on the well established 

evidence that the flux of water, nutrients, materials such as organic matter and contaminants, and the 

movement of biota, from tributaries to larger water bodies influences the biological integrity of 

downstream waters. The movement of multiple materials, beyond simply water, is essential for the 

maintenance of the chemical and biological integrity of downstream waters. The connections that exist 

between tributary streams and their downstream receiving waters are well described in the draft report 

Rosi-Marshall Comments Page 112
Individual comments from members of the SAB Panel for the Review of the EPA Water Body Connectivity Report. 

These comments do not represent consensus SAB advice or EPA policy.

by the EPA, in the comments by the SAB, and are well documented in the peer reviewed scientific 

literature. The wealth of information on these connections provides a very strong basis for this 

rulemaking and the proposed rule is defensible. 

The definition of a tributary: “a water physically characterized by the presence of a bed and banks and 

ordinary high water mark as defined at 33 CFR, 328.3(e), which contributes flow either directly or 

through another water, to a water defined in paragraphs (a)(1) through (4)” is scientifically defensible. 

However, the EPA may reconsider their reliance on the ordinary high water mark because of the lack of 

an OHWM in some systems. Much of the water and materials that enter downstream waters originate in 

small headwater streams high up in watersheds. In some locations in the US, small headwater streams 

are intermittent, but intermittency does not negate the influence of these tributaries on downstream 

waters. Indeed, scientific research has shown that flows that occur intermittently, e.g. during a flood or 

spring snowmelt, can exert a strong influence on downstream systems. A definition of tributary that 

includes these small but extremely important systems, which are inherently connected to downstream 

waters via water and material flow, is necessary. Headwater streams, even when they only flow 

intermittently, exert a strong influence on the chemical and biological integrity of downstream waters. 

This assertion is based on a wealth of scientific evidence (reviewed in the EPA draft report on 

Connectivity, further elaborated on in the SAB’s comments on the draft report, and found in the peerreviewed scientific literature). 

Including wetlands, lakes and ponds in the definition of a tributary although defensible may lead to 

confusion as these systems are not often thought of as tributaries. Although there is substantial evidence 

that maintaining these systems will allow for maintaining the integrity of downstream, it may clarify the 

definition of tributaries to include these systems under the “adjacent” waterbodies. In the course of 

water flowing through a river network, the landscape can change and a small stream may flow into and 

then out of a pond, lake or wetland. These chains of aquatic habitats can be thought of as beads on a 

string that can act in concert to influence the biological integrity of downstream waters. In addition, 

pollution that enters into an aquatic system anywhere along a river network will be transported 

downstream and potentially impair the integrity of downstream waters. Whether the discharge occurs in 

a wetland, pond or headwater stream does not reduce its eventual downstream transport to larger waters 

and does not eliminate its impact and I concur that there is scientific evidence to demonstrate that these 

systems contribute to the integrity of downstream waters, but it may be more clear to include them in the 

definition of “adjacent”. 

In addition, I agree with the proposed definition that the “upper limit of a tributary is established where 

the channel begins”. A great deal of scientific research demonstrates that these very small streams that 

begin high up in a watershed have high biological activity and can exert a strong influence of the 

downstream flow of water and materials, including nutrients, organic matter and animals. The flow of 

these materials has a large influence on the biological integrity of downstream waters as defined in in 

paragraphs (a)(1) through (4) of the proposed rule. In addition, pollutants that are discharged into a very 

small tributary stream will not remain in place, but will be transported downstream and have the 

potential to affect downstream waters. I concur that there is sufficient scientific evidence to include 

tributaries in the definition of waters of the US to maintain the biological and chemical integrity of 

downstream waters. 

The additional need to consider the effects of small waterbodies in aggregate (see page 22196 of the 

proposed rule) were highlighted as an important conclusion of the EPA Report on Connectivity and the 

subsequent comments from the SAB Panel on Connectivity. This is an extremely important finding and 

Rosi-Marshall Comments Page 113
Individual comments from members of the SAB Panel for the Review of the EPA Water Body Connectivity Report. 

These comments do not represent consensus SAB advice or EPA policy.

there is scientific evidence that small waterbodies that are distributed throughout a river landscape can 

have effects in the aggregate. At times, the effects of one small system on a much larger downstream 

waterbody may be challenging to ascertain, but many small systems in aggregate can have a large effect 

on the biological and chemical integrity of the larger downstream water bodies. This aggregation effect 

should be explicitly considered in the rulemaking process. 

2. The proposed rule has defined Waters of the U.S. under the jurisdiction of the Clean Water Act to 

mean all waters, including wetlands, adjacent to a traditional navigable water, interstate water, the 

territorial seas, impoundment, or tributary. This definition is based on the conclusion that a significant 

nexus exists between adjacent water bodies (as defined in the proposed rule) and traditional navigable 

waters, interstate waters, and the territorial seas. Please comment on the adequacy of the scientific and 

technical basis of this proposed definition. (lead discussants are: Drs. Siobhan Fennessy and Mazeika 

Sullivan) 

Response: The inclusion of adjacent waters, including floodplain aquatic habitats and wetlands, in the 

definition of waters of the United States is also based on sound science. The biological integrity of river 

ecosystems is strongly linked to maintaining the connections between water bodies and their adjacent 

aquatic habitats. River ecologists have known for a long time that it is more appropriate to think of 

rivers as part of a larger landscape or “riverscape” comprised of a river’s mainstem and adjacent 

floodplain or wetland habitats. The connections between the river and adjacent habitats, e.g. floodplain 

wetlands and marginal aquatic habitats, include the flux of materials (water, nutrients and contaminants) 

and the flux of organisms. The flux of these materials (e.g. the connectivity of these systems) is 

essential for maintaining the chemical and biological integrity of downstream waters. There are 

numerous examples of these connections provided in the EPA Draft Report on Connectivity, the SAB 

comments on the report and in the published peer reviewed literature. 

The inclusion of adjacent waters, including wetlands, in the definition of waters of the United States is 

also based on a large body of scientific evidence that demonstrates that these systems are connected to 

larger water bodies and that these connections are crucial for maintaining the chemical and biological 

integrity of surface waters. Indeed, when these connections are severed, due to dikes, levees or wetland 

draining, research demonstrates that there are negative consequences for the integrity of downstream 

waters. The inclusion of these habitats in the definition of waters of the US is well grounded in 

scientific and technical understanding of how rivers are connected to adjacent aquatic habitats and how 

these connections influence the chemical and biological integrity of waters.

As mentioned above in response to question 1, the need to consider the effects of small waterbodies such 

as adjacent aquatic habitats in aggregate (see page 22196 of the proposed rule) is very important. There 

is strong scientific evidence that small waterbodies that are distributed throughout a river landscape have 

effects in the aggregate. The effects of one small adjacent system on a larger adjacent waterbody may 

be difficult to determine, but many small adjacent systems in aggregate will influence the biological and 

chemical integrity of waters.

3. The proposed rule has defined Waters of the U.S. under the jurisdiction of the Clean Water Act to 

mean, on a case-specific basis, other waters including wetlands, provided that those waters alone, or in 

combination with other similarly situated waters, including wetlands, located in the same region, have a 

significant nexus to a traditional navigable water, interstate water, or the territorial seas. Please comment 

on the adequacy of the scientific and technical basis of this proposed definition. (lead discussants are: 

Drs. Emily Bernhardt and Michael Gooseff) 

Rosi-Marshall Comments Page 114
Individual comments from members of the SAB Panel for the Review of the EPA Water Body Connectivity Report. 

These comments do not represent consensus SAB advice or EPA policy.

Response: The justification for “other waters” being evaluated on a “case by case” basis or as a group to 

determine the extent to which they have a significant nexus with downstream waters is well described in 

the proposed rule. I agree that considering groups of “similarly situated” waters and the extent to which

they affect downstream waters in aggregate is justified and would alleviate the need for extensive “case 

by case” analysis. The approach to consider “similarly situated” systems and evaluate their connectivity 

as a group makes sense based on our ecological understanding of these systems, i.e. that similar systems 

in a region may act in similar ways and that not every water is unique. In addition, these systems should 

be considered in aggregate, as the degree to which they influence downstream waters will be more 

apparent when considered in aggregate. 

The SAB Report provides additional information on how “other waters” should be defined and how they 

may be connected to downstream waters even when an apparent hydrologic surface flow is lacking. It is 

very important that the ideas put forward by the SAB in response to this section of the Connectivity 

Report be considered when making the final rule about “other waters”. Although these systems may 

not be adjacent to downstream waters and therefore may lack an explicit surface water hydrologic 

connection, they may function, especially in aggregate, in ways that influence the biological and 

chemical integrity of downstream waters. These ideas are well developed in the SAB report and these 

ideas should be explicitly considered during the final rulemaking in regards to these “other waters”. 

4. The proposed rule defines other terms and excludes specified waters and features from the definition 

of Waters of the U.S. Please comment on the adequacy of the scientific and technical basis of the other 

definitions and exclusions. (lead discussants are: Drs. David Allan and Mark Rains) 

No comment.

5. If you have any other comments about the adequacy of the scientific and technical basis of the 

proposed rule, please provide them as well. 

Appendix A, in the CFR document (starting on page 22222) appears to be a draft or a synopsis of the 

Connectivity Report. I assume that because the Connectivity report is still in draft form that this 

Appendix will be revised in the future. As such, I did not provide detailed comments or additional 

suggested references on Appendix A, as that is the content of the SAB’s report. I hope that these 

suggestions will be incorporated into the draft report and that Appendix A will be revised accordingly. 

References: Mulholland, Patrick J., et al. "Stream denitrification across biomes and its response to anthropogenic nitrate 

loading." Nature 452.7184 (2008): 202-205.

Rosi-Marshall Comments Page 115
Individual comments from members of the SAB Panel for the Review of the EPA Water Body Connectivity Report. 

These comments do not represent consensus SAB advice or EPA policy.

Dr. Mazeika Sullivan

Revised Preliminary Comments on “Waters of the United States Proposed Rule”

Mazeika Sullivan, 08.25.2014

Introductory Comments: 

The scientific evidence supports a broad, systemic view of the goal of maintaining and improving water 

quality, as presented in the proposed rule. Consistent with the recommendations of the EPA SAB Panel, the 

collective scientific evidence indicates that there exists a gradient of connectivity between tributaries, 

adjacent waters, “other waters” and downstream waters. Although this gradient of connectivity is recognized 

at multiple locations in the proposed rule (e.g., 22193, 22198, 22223, 22226, 22248), this concept should 

figure as the conceptual backbone of the preamble in order to clearly establish the rationale for those cases 

where important connectivity exists and for those cases where it may not. This gradient framework would 

then provide the basis on which subsequent discussion of various types of water bodies and whether or not a 

“significant nexus” exists with traditional navigable water, interstate water, or the territorial seas. 

Within this context, variation in the strength of connectivity as measured through frequency, duration, 

magnitude, predictability (and other metrics) supports the conclusions that streams and wetlands (and other 

waters) in riparian and floodplain settings are unambiguously connected to and have impacts on downstream 

traditional navigable waters, interstate waters, and the territorial seas (or they are connected via tributaries). 

For “other waters”, a gradient of connectivity can be used to interpret the magnitude of impacts on 

downstream waters and whether this magnitude justifies jurisdictional status under the CWA. Establishing a 

gradient of connectivity as the scientific framework would also clarify that there may not exist cases wherein 

there is no connectivity (in contrast to the statement on 22192: “Waters in a watershed in which there is no 

connection to a traditional navigable water, interstate water, or the territorial seas ... ”), although the degree 

of connectivity may not be sufficient to effect meaningful downstream impacts and, therefore, warrant 

classification as “waters of the United States”.

The proposed rule addresses aggregate effects of streams, wetlands, and other waters on downstream waters 

(e.g., 22196, 22215, 22217, 22222, 22226) and mentions temporal variability in that “connectivity varies 

within a watershed and over time” (22197). The science supports this explicit recognition of the spatial and 

temporal scales at which streams, groundwater systems, and wetlands are functionally aggregated. 

Understanding the interactions of cumulative and temporal effects on downstream waters will also be critical 

to properly assess connectivity both over space and time. 

It is my understanding that the agencies will review the SAB Report and make adjustments to the final rule 

that are deemed appropriate. Given that my comments and contributions relative to the synthesis of the 

supporting scientific literature are incorporated within the SAB Report, I have not provided extensive 

comments on this section (starting on 22222) at this time. I will briefly comment, however, that the synthesis 

of scientific evidence presented in the proposed rule is overall technically accurate and relatively thorough 

and provides support for the conclusions that streams and adjacent wetlands are physically, chemically, 

and/or biologically connected to downstream navigable waters; however, these connections should be 

considered in terms of a connectivity gradient that includes frequency, magnitude, predictability, and 

consequences of connectivity pathways. On the other hand, the scientific literature supports more definitive 

statements that reflect how numerous functions of “other waters” sustain the physical, chemical, and/or 

biological integrity of downstream waters, although the amount of connectivity can vary widely. 

Additionally, as noted below, the role of biological connectivity, while recognized in the synthesis of 

scientific information, is not sufficiently represented as a mechanism of connectivity in the determinations of 

Sullivan Comments Page 116
Individual comments from members of the SAB Panel for the Review of the EPA Water Body Connectivity Report. 

These comments do not represent consensus SAB advice or EPA policy.

a significant nexus. For example, the science and rule related to adjacency could be clarified by including 

biological (and chemical) connections in addition to hydrological linkages. 

1. The proposed rule has defined Waters of the U.S. under the jurisdiction of the Clean Water Act to mean all 

tributaries of a traditional navigable water, interstate water, the territorial seas, or impoundment. This 

definition is based on the conclusion that a significant nexus exists between tributaries (as defined in the 

proposed rule) and the traditional navigable waters, interstate waters, and the territorial seas into which 

they flow. Please comment on the adequacy of the scientific and technical basis of this proposed definition. 

(lead discussants are: Drs. Emma Rosi-Marshall and Jennifer Tank)

In keeping with the SAB Panel’s conclusions, there is strong scientific support that streams exert strong 

impacts on downstream waters and that all tributary streams are physically, chemically, and biologically 

connected to downstream waters. In particular, the proposal that all waters that meet the definition of a 

tributary are “waters of the United States” by rule is technically sounds and supported by the available 

science, as perennial, ephemeral, and intermittent streams all influence the physical, chemical, and biological 

nature of downstream aquatic systems. 

The science clearly supports protection of tributaries, including headwater streams and man-made or manaltered tributaries, under the CWA given the critical functions they perform relative to the larger drainage 

network (e.g., 22227, 22230, 222235). Relative to the proposed definition of “tributary”, a broad definition 

that includes, in addition to streams and rivers, fluvial impoundments, canals, ditches (otherwise not 

excluded), and wetlands that connect tributary segments (i.e., wetland tributaries – which could also would 

be jurisdictional as “adjacent” waters”) that are part of the tributary network is reasonable. However, 

including other features as tributaries that do not have a bed and bank and OHWM (e.g., 22202: “A tributary 

is a longitudinal surface feature that results from directional surface water movement and sediment dynamics 

demonstrated by the presence of bed and banks, bottom and lateral boundaries, or other indicators of 

OHWM.”) seems to extend the classification beyond the scope of the definition provided and is unnecessary 

as these water bodies are jurisdictional as “adjacent” waters. Additionally, adding a descriptor along the lines 

of “or other evidence of flow” to the current definition would more adequately capture variability in tributary 

characteristics in different geographic settings, particularly those in low-gradient, semi-arid and arid systems 

that may not have, for example, a OHWM. 

In determining tributaries, map scale will be an important consideration as differences in map resolution can 

lead to appreciable differences in estimating the extent of the watershed (e.g., Meyer and Wallace 2001, 

Heine et al. 2004). The following language (22201), “When considering whether the tributary being 

evaluated eventually flows to an (a)(1) through (a)(4) water, the tributary connection may be traced using 

direct observation or U.S. Geological Survey maps, aerial photography or other reliable remote sensing 

information, or other appropriate information.”, may be insufficiently specific to ensure adequate estimation 

of the tributary network across different geographic regions that vary in land cover, geology, etc. Additional 

consideration of the aggregate impacts of tributaries to downstream waters is needed.

For further comment on aspects of the proposed definition related to non-jurisdictional features, see response 

to Question #4, below. 

2. The proposed rule has defined Waters of the U.S. under the jurisdiction of the Clean Water Act to mean all 

waters, including wetlands, adjacent to a traditional navigable water, interstate water, the territorial seas, 

impoundment, or tributary. This definition is based on the conclusion that a significant nexus exists between 

adjacent water bodies (as defined in the proposed rule) and traditional navigable waters, interstate waters, 

and the territorial seas. Please comment on the adequacy of the scientific and technical basis of this 

proposed definition. (lead discussants are: Drs. Siobhan Fennessy and Mazeika Sullivan) 

Sullivan Comments Page 117
Individual comments from members of the SAB Panel for the Review of the EPA Water Body Connectivity Report. 

These comments do not represent consensus SAB advice or EPA policy.

There is clear scientific evidence to support strong connectivity between adjacent wetlands and waters, 

including those waters separated from other “waters of the United States” by man-made barriers, natural 

river berms, dunes, etc., and traditional navigable water, interstate water, and the territorial seas, 

impoundments, or tributaries. In particular, the proposal to include adjacent waters, not only adjacent 

wetlands, as “waters of the United States” (e.g., 22199, 22272) is supported by the available science and is a 

technically sound recommendation (i.e., 22207: “The proposed rule proposes to change “adjacent wetlands” 

to “adjacent waters” so that water bodies such as ponds and oxbow lakes, as well as wetlands, adjacent to 

jurisdictional waters are “waters of the United States” by rule.”). Consistent with the SAB Panel’s 

assessment, the scientific literature unequivocally supports the finding that floodplains and waters and 

wetlands in floodplain and riparian settings support the physical, chemical and biological integrity of 

downstream waters. Indeed, river-floodplain systems are integrated ecological units (i.e., riverine landscapes 

and riverscapes, e.g., Thorp et al. 2006) and as such, adjacent wetlands and waters are intimately linked to 

downstream systems. The literature review on this subject (starting 22236) clearly supports strongly 

connectivity of adjacent waters, although a broader riverine landscape perspective would help provide a 

foundational underpinning for the literature synthesis.

The definition of the term riparian area (22207, 22263, 22272) as “an area bordering a water where surface 

or subsurface hydrology directly influence the ecological processes and plant and animal community 

structure in that area” is somewhat narrow in scope given the importance of riparian zones to stream function 

and water quality. Both the EPA Connectivity Report and SAB Panel Report provide ample documentation 

of the science supporting the myriad functions of riparian zones and connections that extend beyond 

hydrologic pathways. Some riparian zones in high-relief headwater catchments, for example, may have 

limited hydrological connections relative to downstream riparian zones but are still critical for maintaining 

stream function via controls on temperature, inputs of organic material, etc. 

Relative to the proposed definitions of “adjacent” and “neighboring” (e.g., 22272), additional consideration 

should be given to the distance between the water body and the tributary in determining whether or not the 

water body is adjacent (in situations where a water body lies outside of the floodplain and riparian area of a 

tributary). In determining a significant nexus, functional adjacency is key, not simply distance. Although 

distance can be one measure to help ascertain the degree of hydrological connectivity, biological and 

chemical connectivity should also be considered. Biological connectivity, in particular, can integrate 

spatially disparate water bodies through movement of organisms. This point is well articulated in the SAB 

Panel Report and could be used as guidance in refining how best to assess connectivity of water bodies 

outside of the floodplain and riparian zone and the question of “reasonable proximity” (e.g., 22208). Using 

hydrological connectivity here as the only linkage measure also seems inconsistent with other parts of the 

proposed rule. For example, relative to “other waters”: (22213) “A hydrological connection is not necessary 

to establish a significant nexus, because, as Justice Kennedy stated, in some cases the lack of a hydrological 

connection would be a sign of the water’s function in relationship to the traditional navigable water, 

interstate water or the territorial seas”. Furthermore, the role of chemical and biological connectivity is 

clearly recognized elsewhere in Section G. For instance, the proposed rule states: (22210) “The agencies 

proposal to determine “adjacent waters” to be jurisdictional by rule is supported by the substantial chemical, 

physical, and biological relationships between adjacent waters, alone or in combination with similarly 

situated waters and (a)(1) through (a)(5) waters.” 

The temporal component is of particular importance in floodplain systems and requires additional discussion. 

The SAB Panel Report suggests using the science of flood frequency-floodplain inundation to estimate 

connectivity, which may help in in ascertaining the appropriate flood interval to use. Nonetheless, 

regional/climatic differences in stream-floodplain dynamics, variable human impacts, and other sources of 

Sullivan Comments Page 118
Individual comments from members of the SAB Panel for the Review of the EPA Water Body Connectivity Report. 

These comments do not represent consensus SAB advice or EPA policy.

variability may suggest that the determination of the appropriate flood interval is best left to the professional 

judgment of the agency (22209). 

Inasmuch as I understand that the agencies are seeking to reduce the burden of many case-specific situations, 

caution is warranted in some cases when the science may not be available to adequately determine where 

jurisdiction should or should not be asserted. Of the alternative options presented (22208), I do not believe 

that current scientific evidence supports asserting jurisdiction over adjacent waters only if they are located in 

the floodplain or riparian zone. However, other proposed options likely would need additional investigation 

at this point. Along a connectivity gradient, there may exist threshold levels of connectivity above which 

downstream influences are impactful to water quality and below which they are not. See responses to 

Question #5 for additional discussion of thresholds. 

22208: “While they may provide the connection establishing jurisdiction, these shallow subsurface flows are 

not “waters of the United States”. Similar to my comment below (Question #4), if the pathway of 

connectivity is not protected, then ultimately neither are downstream water bodies. Ensuring the mechanism

of connectivity (i.e., that defines the “significant nexus”) is critical. 

3. The proposed rule has defined Waters of the U.S. under the jurisdiction of the Clean Water Act to mean, 

on a case-specific basis, other waters including wetlands, provided that those waters alone, or in 

combination with other similarly situated waters, including wetlands, located in the same region, have a 

significant nexus to a traditional navigable water, interstate water, or the territorial seas. Please comment 

on the adequacy of the scientific and technical basis of this proposed definition. (lead discussants are: Drs. 

Emily Bernhardt and Michael Gooseff)

Recognizing the myriad connections between non-floodplain and non-riparian waters and wetlands and 

downstream waters (via surface water, shallow subsurface flowpaths, shallow or deep ground water 

flowpaths, or through chemical and biological connections) with specific attention paid to the magnitude, 

duration, frequency, predictability, and consequences of these connections is critical to understanding that all 

water bodies are likely connected to some extent to downstream waters, although the degree of connectivity 

can vary widely. The proposed rule draws heavily on hydrological connections, and should weight other 

connections equally. For instance, there is growing scientific evidence regarding biological connections 

between non-floodplain wetlands and other water bodies and downstream waters, including the bulk 

exchange of materials via biota, biota as disease vectors, and the movement of nutrients by biota. Other water 

bodies can also provide critical habitat, which can be essential for the life-cycle requirements of downstream 

species. There is some discussion of these points (e.g., 22214, 22222), but the full scope of biological 

connectivity is not fully established in the proposed rule (particularly relative to the role of biota as vectors of 

nutrients, contaminants, and other materials). For example, the proposed rule recognizes that even when 

hydrological connections are visibly absent, many waters still can influence downstream waters, yet states 

that, “However, such circumstances would be uncommon” (22249). To the contrary, birds and other 

organisms can be key movers of nutrients, plants (seeds), and invertebrates between wetlands and 

downstream waters across ranges of spatial scales (e.g., Figuerola et al. 2003, Green et al. 2008).

I believe that the science is currently available (partially summarized starting 22250) to demonstrate that 

sufficient connectivity exists without a case-specific analysis for certain subcategories of “other waters” 

(22216) (e.g., prairie potholes, Carolina and Delmarva bays, pocosins, Texas coastal prairie wetlands, 

western vernal pools). However, further subcategories of these may be appropriate that incorporates a 

combination of water-body type and regional context. I do not believe that the science is sufficiently 

developed to support a determination to exclude any groups of “other waters” (or subcategories thereof, e.g., 

Great Plains playa lakes) from jurisdictional status at this time in spite of the resource-intensive nature of a 

case-specific analytical approach. Before such determinations are made, additional research is required to 

Sullivan Comments Page 119
Individual comments from members of the SAB Panel for the Review of the EPA Water Body Connectivity Report. 

These comments do not represent consensus SAB advice or EPA policy.

establish degree of connectivity, analysis of spatial and temporal variability, and threshold levels of 

connectivity. This research will be a requisite step in further refining rules relative to the jurisdictional status 

of “additional other waters of the US” and in particular, if “categories of ‘other waters’ are similarly situated 

and have a significant nexus and are jurisdictional by rule, or that as a class they do not have such a 

significant nexus and might not be jurisdictional” (22216-22217). 

Determining if waters are “similarly situated” is a reasonable approach with scientific support (22247). 

Biotic community assemblage and presence/absence of species might be other metrics used to assess 

similarity, along with the factors currently provided as examples in the proposed rule (22213: habitat, water

storage, sediment retention, pollution sequestration). Whereas analyzing the chemical, physical, and/or 

biological effects of “other waters” in concert with other similarly situated water bodies is technically sound, 

supported by the science, and provides a basis for decision-making, water bodies that are disparate relative to 

their characteristics and function may also contribute to the cumulative effects of the water bodies in a 

region, and thus there may be cases wherein it is appropriate to analyze “other waters” in the aggregate (in 

contrast to a whole-scale statement indicating that it would be “inappropriate ... to consider ‘other waters’ as 

‘similarly situated’ if these ‘other waters’ are located in different landforms, have different elevation profiles, 

or have differ soil and vegetation characteristics ...” (22213). Determining by rule that “other waters” are 

similarly situated in certain areas of the country is an intriguing idea, although my initial reaction is that 

Level 3 Ecoregions may be too broad of a classification. Additionally, human alteration of watersheds can 

alter the types of connections to downstream waters as well as the magnitude, frequency, duration, 

predictability, and consequences of these connections. How would variability stemming from the role of 

humans on the watershed landscape be captured within a regional approach?

Relative to a case-specific basis for other waters, the proposed rule correctly recognizes the role of aggregate 

and temporal effects. This is a key point in relation to assessing whether a water body has a “significant 

nexus”. Determining when (temporally) surveys will be conducted, what map scale will be used (although 

this point is somewhat addressed on 22212, 22226), and how aggregate effects will be determined is critical 

to appropriate assessment of these case-by-case situations. For example, many current databases do not 

represent the full extent and/or size of the drainage network. For additional comments on this point, see 

responses to Question #1. This topic is also addressed in the SAB Panel Report. 

4. The proposed rule defines other terms and excludes specified waters and features from the definition of 

Waters of the U.S. Please comment on the adequacy of the scientific and technical basis of the other 

definitions and exclusions. (lead discussants are: Drs. David Allan and Mark Rains)

Discriminating between shorter-term erosional features (e.g., rills and gullies) and longer-term headwater 

channels represents a challenge relative to mapping (e.g., James et al. 2007) as well as to the nature of 

ecological transitions between, for example, gullies and ephemeral streams. However, to exclude these and 

other variable source areas (e.g., swales) from jurisdiction is not fully supported by the available science as 

they can be important components of integrated aquatic systems with measurable impacts to downstream 

systems. For instance, Hansen and Law (2006) found that small gullies in South Carolina contributed runoff 

and sediment during tropical storm episodes of a magnitude of 48 tonnes from a 0.1-ha discontinuous valley 

side gully over 9.5 years. Thus, consideration of these features in the aggregate and over variable temporal 

scales is important relative to downstream impacts. The SAB Panel Report provides further suggestions and 

guidance relative to these erosional features, and emphasizes that the important role of these source areas to 

downstream connectivity. Thus, the agencies should maintain the right to classify specific gullies, rills, and 

swales (either separately or in the aggregate) as jurisdictional when warranted. The agencies are proposing to 

not retain authority to determine in a particular case that these waters are a “water of the United States” 

(22218), and I remain unconvinced that this determination is fully in keeping with the available science. 

Sullivan Comments Page 120
Individual comments from members of the SAB Panel for the Review of the EPA Water Body Connectivity Report. 

These comments do not represent consensus SAB advice or EPA policy.

In general, the rationale for excluded waters focuses on physical features (channel morphology, flow 

permanence, etc.). There is an alarming lack of evidence provided relative to making the case for a lack of 

biological and/or chemical connectivity. While I agree that some of these waters should not be jurisdictional, 

consideration of other measures of connectivity may aid in making appropriate determinations as to which 

should be considered on a case-specific basis (or potentially as a class). To determine regulatory practices 

only on one dimension of connectivity is problematic and may indicate it is premature to move fully away 

from a case-specific basis for all the waters listed on 22218, 22263, 22274. For example, drainage ditches 

have been shown to exhibit a range of ecological functions (see Herzon and Helenius 2008) and while 

hydrological connectivity is clearly important, other types of connectivity should also be considered. 

In general, I do not agree that there is sufficient scientific evidence to support the exclusion of ditches, and it 

may be appropriate to move some categories of ditches into “other waters”. In the Midwest, for example, 

ditches dominate headwaters in many watersheds. Excluding by rule certain ditches from these systems 

could be highly problematic and further fragment these watersheds. Currently, the definition of “uplands” is 

unclear in the proposed rule and I do not agree that perennial flow should be a requirement for jurisdiction. 

How is connectivity that may not be initially present but would be expected to develop over time viewed? 

For instance, does an artificial lake or pond created by excavating and/or diking dry land and used 

exclusively for stock watering, irrigation, settling basins, etc. that is likely to develop a strong connection 

with a traditional navigable water body in the future remain non-jurisdictional? 

There are other points that warrant attention. For example, 22219: “It is important to note, however, that 

even when not jurisdictional waters, these non-wetland swales, gullies, rills and specific types of ditches may 

still be a surface hydrologic connection for purposes of the proposed definition of adjacent under paragraph 

(a)(6) or for purposes of a significant nexus analysis under paragraph (a)(7). For example, a wetland may be 

a ‘’water of the United States,’’ meeting the proposed definition of ‘neighboring’ because it is connected to 

such a tributary by a non-jurisdictional ditch that does not meet the definition of a ‘tributary’.” The entire 

concept of water body connectivity is that integrated ecological units composed of aquatic systems 

distributed across the landscape are intimately linked through a suite of pathways. How is it consistent with 

this notion or in the spirit of the CWA that the ditch that connects two “waters of the US” is not 

jurisdictional?

In summary, the current science supports that some “other waters” are unlikely to be sufficiently connected 

to warrant jurisdiction (e.g., artificial reflecting pools, swimming pools, artificially irrigated areas, 

depressions with water following construction) but I am not convinced that the science currently exists to 

summarily exclude certain groups other waters including gullies, swales, artificial lakes and ponds, and 

ditches that do not contribute flow to a jurisdictional water body. These waters should be assessed along a 

gradient of connectivity on a case-specific basis until the science is available to make an appropriate 

determination for the respective class as a whole. 

5. If you have any other comments about the adequacy of the scientific and technical basis of the proposed 

rule, please provide them as well. 

Significance: The Proposed Rule points out that “significance” is not a scientific term (e.g., 22195). 

However, it is a statistical term, often used in scientific contexts to indicate when observations are “real” 

versus those observed by chance. Other terms that do not carry such meaning may be more appropriate: e.g., 

important, substantial, impactful. 

Ecological thresholds: Ecosystems may not respond to gradual changes in smooth and/or linear ways, but 

rather with sudden, discontinuous shifts to an alternative stable state as the ecosystem exceeds a tipping point 

Sullivan Comments Page 121
Individual comments from members of the SAB Panel for the Review of the EPA Water Body Connectivity Report. 

These comments do not represent consensus SAB advice or EPA policy.

in one or more of its principal processes (Ludwig et al. 1997). Such thresholds – conditions beyond which an 

abrupt change in a quality, property, or function of an ecosystem are precipitated – are tightly linked to 

ecosystem condition (see Turner 2002). Understanding and targeting potential threshold levels of 

connectivity between water bodies and downstream waters could substantially contribute to our current 

understanding if and where threshold levels of connectivity occur along the connectivity gradient that 

includes frequency, magnitude, predictability, and consequences of connectivity pathways. There is a 

growing body of literature on environmental and ecological thresholds (e.g., Friedel 1991, Bledsoe and 

Watson 2001, Church 2002, Richardson et al. 2007, Evans-White et al. 2009, King et al. 2011, Chambers et 

al. 2012, Goss et al. 2014) as well as suite of analytical methods (e.g., Clements et al. 2007, Gido et al. 2007, 

King and Richardson 2003, Richardson and Qian 2007, Richardson et al. 2007, Sonderegger et al. 2009, 

King et al. 2011, Daily et al. 2012). This could be an area of importance for future research. 

Literature Cited

Bledsoe, B.P. and C.C. Watson. 2001. Logistic analysis of channel pattern thresholds: meandering, braiding, 

and incising. Geomorphology 38:281-300.

Chambers, P.A., J.M. Culp, E. S. Roberts, and M. Bowerman. 2012. Development of environmental 

thresholds for streams in agricultural watersheds. Journal of Environmental Quality 41:1-6.

Church, M. 2002. Geomorphic thresholds in riverine landscapes. Freshwater Biology 47:541-557.

Clements, W., B. Noon, and H. Wang. 2007. Ecological thresholds and responses of stream benthic 

communities to heavy metals. Ecological Thresholds in Aquatic Ecosystems: The Role of Climate 

Change, Anthropogenic Disturbance, and Invasive Species Progress Review Workshop. US EPA, 

Washington, DC, USA, http://www.scgcorp.com/eco-thresholds07/docs/13-Clements.pdf.

Daily, J.P., N.P. Hitt, D.R. Smith, and D.R. Snyder. 2012. Experimental and environmental factors affect 

spurious detection of ecological thresholds. Ecology 93:17-23.

Evans-White, M.A., W.K. Dodds, D.G. Huggins, and D.S. Baker. 2009. Thresholds in macroinvertebrate 

biodiversity and stoichiometry across water-quality gradients in Central Plains (USA) streams. 

Journal of the North American Benthological Society 28:855-868.

Friedel, M.H. 1991. Range condition assessment and the concept of thresholds: a viewpoint. Journal of range 

management 44:422-426.

James, L.A., Watson, D.G., and W.F. Hansen. 2007. Using LiDAR to map gullies and headwater streams 

under forest canopy: South Carolina, USA. Catena 71:132-144.

Figuerola, J., A. J. Green, and L. Santamaria. 2003. Passive internal transport of aquatic organisms by

waterfowl in Doñana, south-west Spain. Global Ecology and Biogeography 12:427-436.

Gido, K., W. Dodds, J. Koelliker, K. With, D. Walks, D. Chandler, and J. Aguilar. 2007. Ecosystem 

thresholds and alternate states in Great Plains rivers and streams: cascading effects of anthropogenic 

hydrologic disturbance. Ecological Thresholds in Aquatic Ecosystems: The Role of Climate Change, 

Anthropogenic Disturbance, and Invasive Species Progress Review Workshop. US EPA, 

Washington, DC, USA, http://www.scgcorp.com/eco-thresholds07/docs/05-GIDO-DODDS.pdf 

Goss, C.W., P.C. Goebel, and S.M.P. Sullivan. 2014. Shifts in attributes along agricultural-forest transitions 

of two streams in central Ohio, USA. Agriculture, Ecosystems & Environment 197: 106-117.

Green, A. J., K. M. Jenkins, D. Bell, P. J. Morris, and R. T. Kingsford. 2008. The potential role of waterbirds 

in dispersing invertebrates and plants in arid Australia. Freshwater Biology 53:380-392.

Hansen, W.F., and D.L. Law, 2006. Sediment from a small ephemeral gully in South Carolina. In: Proc. Soc. 

American Foresters National Convention, Fort Worth, Texas, 2005.

Heine, R.A., Lant, C.L., and R.R. Sengupta. 2004. Development and comparison of approaches for 

automated mapping of stream channel networks. Annals of the Association of American Geographers 

94: 477–490.

Herzon, I. and J. Helenius. 2008. Agricultural drainage ditches, their biological importance and functioning. 

Biological Conservation 141: 1171-1183.

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Individual comments from members of the SAB Panel for the Review of the EPA Water Body Connectivity Report. 

These comments do not represent consensus SAB advice or EPA policy.

King, R.S. and C.J. Richardson. 2003. Integrating bioassessment and ecological risk assessment: An 

approach to developing numerical water-quality criteria. Environmental Management 31:795-809.

King, R.S., M.E. Baker, P.F. Kazyak, and D.E. Weller. 2011. How novel is too novel? Stream community 

thresholds at exceptionally low levels of catchment urbanization. Ecological Applications 21:1659-

1678.

Ludwig, D., B. Walker, and C.S. Holling. 1997. Sustainability, stability and resilience. Conservation 

Ecology 1:7.

Meyer, J.L., and L.B. Wallace. 2001. Lost linkages and lotic ecology: rediscovering small streams. In: Press, 

M.C., Huntly, N.J., and S. Levin (Eds.), Chapter 14. Ecology: Achievement and Challenge. 

Blackwell Science, Oxford, UK.

Richardson, C.J., R.S. King, S.S. Qian, P. Vaithiyanathan, R.G. Qualls, and C.A. Stow. 2007. Estimating 

ecological thresholds for phosphorus in the Everglades. Environmental Science and Technology 

41:8084-8091.

Richardson, C.J. and S.S. Qian. 2007. A statistical methodology for the detection, quantification, and 

prediction of ecological thresholds. Ecological Thresholds in Aquatic Ecosystems: The Role of 

Climate Change, Anthropogenic Disturbance, and Invasive Species Progress Review Workshop. US 

EPA, Washington, DC, USA http://www.scgcorp.com/eco-thresholds07/docs/03-

RICHARDSON.ppt.pdf.

Sonderegger, D.L., H.N. Wang, W.H. Clements, and B.R. Noon. 2009. Using SiZer to detect thresholds in 

ecological data. Frontiers in Ecology and the Environment 7:190-195.

Thorp, J.H., M.C. Thoms, and M.D. DeLong. 2006. The riverine ecosystem synthesis: biocomplexity in river 

networks across space and time. River Research and Applications 22:123-157.

Turner, M. 2002. Landscape pattern, ecological processes and critical thresholds. In: Workshop on 

Ecological Thresholds. USEPA, Office of Research and Development, Washington, DC, 

http://www.environmentalfutures.org/agenda.htm.

Sullivan Comments Page 123
Individual comments from members of the SAB Panel for the Review of the EPA Water Body Connectivity Report. 

These comments do not represent consensus SAB advice or EPA policy.

Dr. Jennifer Tank

Comments to the chartered EPA-SAB on the adequacy of the scientific and technical basis of the 

proposed rule titled Definition of Waters of the United States Under the Clean Water Act. 

Jennifer L. Tank, Department of Biological Sciences, University of Notre Dame, Notre Dame, IN 46556

Questions

1. The proposed rule has defined Waters of the U.S. under the jurisdiction of the Clean Water Act to 

mean all tributaries of a traditional navigable water, interstate water, the territorial seas, or 

impoundment. This definition is based on the conclusion that a significant nexus exists between 

tributaries (as defined in the proposed rule) and the traditional navigable waters, interstate waters, and 

the territorial seas into which they flow. Please comment on the adequacy of the scientific and technical 

basis of this proposed definition. (lead discussants are: Drs. Emma Rosi-Marshall and Jennifer Tank)

General Comment:

Given my expertise and familiarity with the science associated with the Connectivity Report, informing 

the proposed rule, I found the proposed definition of “tributaries” to be accurate and clearly written. 

Specific Comments: 

P22203, C1, P2, L16 AND P22206, C2, P2: I am also supportive of the alternate interpretation that 

wetlands that connect tributary segments would be considered “adjacent wetlands”, and as such would 

be jurisdictional waters of the United States under (a)(6). As such, wetlands would not be considered 

tributaries, but would remain jurisdictional as adjacent waters.

P22203, C2, P2. L50: In response to the query, I suggest that the flow regime in identified ditches 

should be less than intermittent flow, rather than less than perennial flow as proposed, based on my 

familiarity with the science associated with the Connectivity Report. This would apply only to those 

ditches not excluded by the proposed regulation and that meet the proposed definition of tributary as 

‘‘waters of the United States.’’

2. The proposed rule has defined Waters of the U.S. under the jurisdiction of the Clean Water Act to 

mean all waters, including wetlands, adjacent to a traditional navigable water, interstate water, the 

territorial seas, impoundment, or tributary. This definition is based on the conclusion that a significant 

nexus exists between adjacent water bodies (as defined in the proposed rule) and traditional navigable 

waters, interstate waters, and the territorial seas. Please comment on the adequacy of the scientific and 

technical basis of this proposed definition. (lead discussants are: Drs. Siobhan Fennessy and Mazeika 

Sullivan)

General Comment:

Given my expertise and familiarity with the science associated with the Connectivity Report, informing 

the proposed rule, I found the proposed definition of “adjacent water bodies” to be accurate and clearly 

written, which includes definitions of the terms “neighboring”, “riparian area” and “floodplain”. 

Specific Comment: 

Tank Comments Page 124
Individual comments from members of the SAB Panel for the Review of the EPA Water Body Connectivity Report. 

These comments do not represent consensus SAB advice or EPA policy.

P22209, C1, P2, L38: I am supportive of keeping text as written whereas best professional judgment is 

used to determine which flood interval is appropriate to determine if a water is located in the floodplain 

of a jurisdictional water, rather than providing greater specificity.

P22209, C2, P3, L1: I am supportive of the proposed deletion of the parenthetical text from the existing 

‘‘adjacent wetlands’’ regulatory provision of the phrase ‘‘other than waters that are themselves 

wetlands’’. 

3. The proposed rule has defined Waters of the U.S. under the jurisdiction of the Clean Water Act to 

mean, on a case-specific basis, other waters including wetlands, provided that those waters alone, or in 

combination with other similarly situated waters, including wetlands, located in the same region, have a 

significant nexus to a traditional navigable water, interstate water, or the territorial seas. Please 

comment on the adequacy of the scientific and technical basis of this proposed definition. (lead 

discussants are: Drs. Emily Bernhardt and Michael Gooseff)

General Comment:

Given my expertise and familiarity with the science associated with the Connectivity Report, informing 

the proposed rule, I found the proposed definition of “other waters” to be accurate and clearly written. 

Specific Comment: 

Pg 22212, C1, P2, L14: In response to the request by the agencies for comments on the listing of “other 

waters”, I am supportive of the rule as it stands whereby the agencies “do not propose to re-promulgate 

this list of ‘‘other waters’’ because it is unnecessary and has led to confusion where it has been 

incorrectly read as an exclusive list.”

Pg22214, C3, P1, L2: In response to the request by the agencies for feedback on “the inclusion of 

subcategories of types of ‘‘other waters,’’ either alone or in combination with similarly situated waters, 

that can appropriately be identified as always lacking or always having a significant nexus”, I suggest 

that Comments made through the SAB review of the Connectivity Report could provide suggestions 

appropriate for inclusion. 

4. The proposed rule defines other terms and excludes specified waters and features from the definition 

of Waters of the U.S. Please comment on the adequacy of the scientific and technical basis of the other 

definitions and exclusions. (lead discussants are: Drs. David Allan and Mark Rains)

General Comment:

Given my expertise and familiarity with the science associated with the Connectivity Report, informing 

the proposed rule, I found the descriptions proposed other definitions and exclusions to be accurate. 

5. If you have any other comments about the adequacy of the scientific and technical basis of the 

proposed rule, please provide them as well.

Pg 22193,C2, P3, L8 AND Pg 22197, C3, P4, L8: Replace “is not an all or nothing situation”, with “is a 

gradient” as that concept is central to the Connectivity Report on which the rule is based. 

Pg 22194, C3, P1, L5: Recommend inserting “and recurring” after “systematic” to better reflect the 

nature of the interactions occurring in a watershed. 

Tank Comments Page 125
Individual comments from members of the SAB Panel for the Review of the EPA Water Body Connectivity Report. 

These comments do not represent consensus SAB advice or EPA policy.

Pg 22196, C1, P2, L34: Recommend replacing “mercury” with “contaminants” as the Connectivity 

Report covers contaminants more broadly than just mercury. 

Pg 22196, C1, P3, and continuing in C2: Up until this point, the term tributary has been used, and here 

the term “stream” is introduced, presumably interchangeably. This may be confusing, and if tributary

rather than stream is appropriate, then it should be used consistently throughout. 

Pg 22196, C2, P1, L3: Recommend “take up and change nutrients” be replaced with “assimilate and 

transform nutrients”, if not deemed too technical. 

Pg 22196, C2, P2, L15: Recommend that the statement “such that the significance of the connection is 

difficult to generalize across the entire group of waters.” be modified so as to be consistent with revision 

to the Connectivity Report, where the concept of “gradient of connectivity” was introduced in this 

context. 

Pg 22197, C2, P1, L24: Recommend replacing “nitrogen” with “nutrients”, to be consistent with role of 

streams in transforming multiple nutrients, not just nitrogen. 

Pg 22197, C2, P3 and continuing in C3: This text should be revised to be consistent with any changes 

made to the Connectivity Report in response to SAB review. At present, the content does not reflect the 

consensus that “non-adjacent waters reflect a continuum of connectivity” which is the sentiment of the 

SAB Review based on current scientific understanding.

Pg 22222, C1, Appendix A: The text provided in this summary of scientific evidence should be updated 

and consistent with any changes that are incorporated in response to the SAB Review of the 

Connectivity Report. 

Tank Comments Page 126
Individual comments from members of the SAB Panel for the Review of the EPA Water Body Connectivity Report. 

These comments do not represent consensus SAB advice or EPA policy.

Dr. Maurice Valett

Proposed Rule for Definition of Waters of the United States Under the Clean Water Act:

Comments from HM Valett

Proposed Rule for Definition of Waters of the United States Under the Clean Water Act:

I. General Info

none

II. Background

22195: use of the term ‘significant’- The text on this page indicates that ‘significant is not a scientific term’. It 

would be better to state that ‘significant’ is not meant to be used in a scientific manner at this point (i.e., refer 

to Kennedy’s intent, as employed on page 22196; ...more than speculative or insubstantial). I make this point 

because ‘significant’ is indeed a scientific term with implications of the probability of quantitative relationships 

among statistical estimates to effectively reflect reality (i.e., P values, etc).

III. Proposed definition of Waters of the United States

22204: proposed definition of ‘tributary’ - OHWM and semi-arid channels - Central to the proposed definition is 

the notion of the existence of an ‘ordinary high water mark’ (OHWM) and indirect or direct linkage to 

jurisdictional water. Recognition of both direct and indirect (i.e., through an additional entity that connects 

directly to the jurisdictional water) appropriately employs a ‘systems’ approach as emphasized in the Rapanos

case (547 US 1t 781-782). This is a great strength of the definition. 

Reliance on the OHWM to distinguish ‘streams’ from gullies or rills is perfectly appropriate in environments 

where climatic conditions result in fluvial geomorphic features that are formed by perennial flows and 

effectively represent ‘permanent’ waters. The science behind perspectives addressing where ‘streams’ start and 

the progression of hydrologic and geomorphic character, however, is hugely biased towards perennial systems. 

Other work (has emphasized environments and biomes where flow is not ‘ordinary’ and the concept of OHWM 

just doesn’t work well. In truth, the transition from terrestrial to aquatic is a continuum and while I recognize 

the need for distinction, care must be taken to incorporate channels in semi-arid environments where flows 

occur uncommonly but are critical to the ‘aquatic system’. Accordinlgy, I am worried about how this definition 

will be employed (or not) in semi-arid (i.e., desert) biomes where water issues are likely to first become 

apparent. 

On the bottom of the first column on page #22202 the text reads ‘The flow in a tributary may be ephemeral, 

intermittent, or perennial...’ but on page #22203 in the middle column, half way down the page, the text reads 

‘The scientific concept of perennial flow is a widely accepted and well understood hydrologic characteristic of 

tributaries’. Written in that manner, it would suggest that perennial flow is a ‘necessary’ component for a 

channel to qualify as a tributary. This seems inconsistent. The inconsistency continues as the text on page 

#22205, middle column near top, reads that ‘Sediment transport is also provided by ephemeral streams’, 

provided as part of a description of how tributaries have significant nexus with jurisdictional waters. This sort of 

Valett Comments Page 127
Individual comments from members of the SAB Panel for the Review of the EPA Water Body Connectivity Report. 

These comments do not represent consensus SAB advice or EPA policy.

statement suggests that ‘ephemeral’ systems qualify first as streams and second as tributaries. My concern is 

that the terminology used here (ephemeral, intermittent, perennial) must be clearly identified and quantifiable. 

Determining a ‘sig nexus’ for the headwater (i.e., intermittent) streams of semi-arid landscapes will be greatly 

complicated by the ‘atypical’ geomorphology of these systems. Without the OHWM these channels may be 

categorized as ‘other waters’ and, therefore, will require establishment of a significant nexus to be categorized 

as ‘adjacent’ or ‘neighboring’.

22205: significant nexus for tributaries - Biological linkage is argued to occur among tributaries and the text 

here emphasizes anadromous fishes. This is accurate and appropriate, but these fishes are rare at a national 

scale. Benthic insects, however, are robustly common and integrate streams and tributaries through drift and 

upstream flight (i.e., Colonization Cycle, Muller, K. 1982. The colonization cycle of freshwater insects. Oecologia 

52:202-207.)

22206: exclusion of wetlands as ‘tributaries’, middle column - I agree with the agencies recognition that 

wetlands may play critical roles linked to lotic systems, but I feel it is best not to incorporate them in the more 

robust definition of tributary contributed by the proposed rule. Inclusion will dilute the clarity intended and 

promote confusion. It is far better to rely on ‘adjacent’ or ‘neighboring’ status to link wetlands to jurisdictional 

waters.

22208 & 22209: clarification on waters with ‘these types of connections’ - This portion of the proposed rule 

addresses waters that are ‘neighboring’ or ‘adjacent’ and how ‘waters with these types of connections’ may be 

identified via ‘reasonable options for providing clarity’. 

Two responses come to mind in regard to this issue, 1) there is no simple way to address the existence of a 

significant nexus....the concept is the correct one and addressing the existence of the nexus will be the burden of 

the agencies as recognized, and 2) claiming the ‘floodplain’ waters as adjacent is theoretically sound but 

operationally problematic. In studies of larger river systems, it is clear that current climatic conditions may 

support flooding and inundation of a given frequency, but its occurrence may be eliminated by modifications to 

stream banks (e.g., levees) and flow regimes (e.g., extractions, impoundments). Flood recurrence intervals are 

logical for ‘connected’ floodplains but there will be a need to establish new flow assessment to determine how a 

given magnitude will translate to ‘connection’ and influence nexus. The ultimate issue is one of connection and 

distinction as ‘riparian’ may or may not correspond to ‘floodplain’ landscape position. I do believe that the 

agencies are correct to claim the floodplain waters as ‘adjacent’ but the ‘riparian’ definition suggests that 

‘surface or subsurface hydrology’ influences these environments. First of all, ‘hydrology’ is the study of water 

movements and distribution. That’s not really the correction term to use in the riparian definition. I will admit 

that the term is commonly used (in peer-re viewed literature) to mean the movement and distribution of water, 

but the definition fails to link ‘riparian’ environments to the lotic systems of concern. The floodplain definition 

takes care of this issue.

Regarding how to approach designation, there isn’t a ‘desktop’ version available. Floodplains and their 

surrounding environments are linked over vastly differing spatial and temporal scale and I don’t believe that the 

agencies are going to be able to ‘categorize’ without due diligence. Costly, but accurate.

22211: ‘other waters’ and case-specific assessment - I think the agencies have it right here. There is a clear 

need to address on a ‘case-specific’ basis the status of a water body designated as ‘other’. In fact on page 

Valett Comments Page 128
Individual comments from members of the SAB Panel for the Review of the EPA Water Body Connectivity Report. 

These comments do not represent consensus SAB advice or EPA policy.

#22211, right column, ‘other waters’ are specifically defined as those that require assessment of a ‘case-specific 

significant nexus determination’. The agencies clarify that they will remove an old list of ‘others’ to eliminate 

confusion (i.e., the mistaken notion that the list was exhaustive).

The larger issue is whether ‘similarly situated’ water bodies need to be addressed individually or can be assessed 

as a ‘landscape unit’ (see page #22213. left column) in a cumulative context. This language appropriately 

embraces the cumulative effects of ‘neighboring’ waters, characteristic of dendritic drainages and ‘watersheds’ 

as a whole. I really like the use of ‘landscape unit’ as it suggests integrated function. The request to employ a 

‘landscape unit’ approach is a tricky one, but one that seems like it can be operationalized (i.e., aggregation on a 

‘local’ basis to establish the landscape unit).

22212-22213: ‘in the region’ and ‘similarly situated’ - The agencies have correctly engaged in addressing this 

issue by clarifying their position on Justice Kennedy’s use of ‘in the region’ and ‘similarly situated’. With their 

approach, ‘region’ becomes synonymous with watershed (really catchment is the correct term). Later there 

appears to be recognition that ‘regions’ are larger things. Their interpretation does, however, keep the 

hydrologic linkage (i.e., and evident nexus) at the core of the distinction and that is a strength of the approach. 

Use of the NHD and HUC-10 tools are appropriate for designation as they are based on the same notion of 

‘watershed’ delineation.

The definition employed for ‘similarly situated’ waters is nicely rooted in function and appropriately employs the 

‘landscape unit’ concept. While geographic proximity can be misleading (i.e., some things nearby may be 

disconnected while others afar remain fully integrated), it needs to be included in the use of the term as 

geographic proximity is the basis of the ‘region’ notion above and the notion of similarity employed here....even 

given the clear focus on function. Note, however, when the definition of ‘similarly situated’ is addressed (left 

column, bottom, 22213), it is rooted in characteristics of the terrestrial environment (soils, vegetation, 

landform). Given the emphasis that the SAB has placed on a ‘flowpath’ conceptual basis for the Water Body 

Connectivity report, I find it strange that ‘hydrologic connectivity to each other or a jurisdictional water’ arrives 

as a caveat...almost an afterthought. I would propose elevating it to the same level of importance as the 

terrestrial characteristics. 

At the same time, the use of ‘relatively homogenous soils, vegetation and landform’ is a vague distinction. Soils 

and vegetation are notoriously heterogeneous at different scales. I’m not sure if this notion helps aggregate at 

all.

22214: use of the term ‘report’ – In the left column, top of page, the text reads ‘For example, a report that 

reviewed the results....’. The use of the term ‘report’ is misleading. The citation provided indicates a peerreviewed publication and the product should be named as such. There are no standards for reports that cross 

agencies and institutions.

22214: clarifying chemical nexus – Mid-point of left column the text argues that landscape position influences 

the strength of connection to the nearest water of the US. This may be a true statement, but it is not specific to 

chemical nexus and seems out of place. 

22214: regional and national studies and ‘desktop evaluation’ – Despite the very specific definition of region 

and the efforts to consider ‘similarly situated’, the agencies now suggest that ‘national’ scale assessments are 

Valett Comments Page 129
Individual comments from members of the SAB Panel for the Review of the EPA Water Body Connectivity Report. 

These comments do not represent consensus SAB advice or EPA policy.

applicable. Moreover, they make the statement that ‘desktop’ assessment will be appropriate if ‘sufficient’ 

information exists. Without any protocol established a priori, this statement is arrogant and borders 

oninflamatory. Is it their intent to say that they dont have to do field work when it isn’t necessary? Again, 

without established protocol to address, this statement should be seriously reconsidered.

22214: ‘additional scientific research and data that might further inform decisions about other waters’ – The 

rule to be promulgated addresses specific relationships among water bodies across multiple scales. It is clear 

that the agencies are concerned about ‘resources’ for case-specific assessment. I suggest that a series of specific 

RFPs address these needs in the future to focus research on just these issues. Back-fitting research originally 

addressing a different question will only go so far in this sense.

22215-22216: request for comment on ‘these alternative approaches’ – Determining by rule that ‘other waters 

are similarly situated’ in certain areas is proposed to be applicable by recognition of the idea that 

streams/waters within an ‘ecoregion’ behave similarly. The ecoregions addressed by the agencies are thought to 

have similar ecosystems and resources. Omernik’s work comes from a geography background (Omerink, J.M. 

1987. Ecoregions of the conterminous United States. Annals of the Association of American Geographers. 

77:118-125). This (and the list of Leve III ecoregions) compiles associations based again on terrestrial entities. 

What about HUC-10 or aggregation based on flow characteristics (Poff, N. L., and J. V. Ward. 1989. Implications 

of streamflow variability and predictability for lotic community structure: A regional analysis of streamflow 

patterns. Canadian Journal of Fisheries and Aquatic Sciences 46:1805-1818.)? While the focus is on Waters of 

the United States, there seems to be tie to terrestrial geography here at the expense of ‘water-based’ 

categorization. Result may be similar or not but the focus should be on distribution and flow of water within 

‘regions’ directly assessed rather than inferred from terrestrial association. A comparison of the two (terrestrial 

vs. aquatic) should yield insight.

Such an approach would ‘group’ streams as similar in the context of their flow characteristics and derive a 

geographic association simultaneously. The issue of whether those streams within a ‘region’ are ‘similarly 

situated’ remains unsolved. Position along the flow continuum and discontinuities associated with different 

processing domains (Montgomery, D. R. 199. Process domains and the river continuum. Journal of the American 

Water Resources Association 35:397-410.) will be important in determining ‘landscape position’ and addressing 

the question of ‘similarly situated’.

22217: general tendencies – Middle column half way down – I’m not sure it make any sense to telegraph the 

interpretation of aggregation at this point. This may raise the ire and appears to be pre-judging the issue of 

aggregation. How does including this help with clarity?

2217 & 2218: agriculture and the CWA – While this is not the task of the SAB, the agencies and the US as a 

whole need to start thinking about the logic of regulating all but the largest polluters of its waters.

IV. Related Acts of Congress, Executive Orders, and Agency Initiatives 

none

Valett Comments Page 130
Individual comments from members of the SAB Panel for the Review of the EPA Water Body Connectivity Report. 

These comments do not represent consensus SAB advice or EPA policy.

Appendix A: Scientific Evidence

Part I: synthesis of peer-reviewed literature

22222: upper right column, bidirectional vs. unidirectional – These terms continue to hang around even as we 

have clearly deemed them confusing and inappropriate. I expect they will be eliminated from future versions?

Part II: additional scientific support

Under section ‘i. tributaries’ the outline form breaks down with the following errors:

i. tributaries

A. tribs have nexus

B. tribs affect physical integrity

C. tribs affect chemical integrity

mistake C. tribs affect biological integrity

mistake D. headwater tribs influence phys, chem, biol

F. non-permanent streams via phys, chem, biol

mistake E. Trib lake, pponds, wetlands

mistake F. man-made tirbs

Valett Comments Page 131