Revised Definition of "Waters of the United States"
Response to Comments Document
Section 16 - Technical Support Document (TSD) and Other Science
See the Introduction to this Response to Comments Document for a discussion of the U.S. Environmental
Protection Agency and the U.S. Department of the Army's (hereinafter, the agencies ) comment response
process and organization of the eighteen sections.
16 Technical Support Document and Other Science 2
16.1 Technical Support Document and the Science Report 2
16.1.1 Support for the Technical Support Document and the Science Report 2
16.1.2 Criticisms of the Technical Support Document and the Science Report 3
16.1.3 General Comments on the Agencies' Use of Science 7
16.2 Review of the Scientific Literature Published Since the Release of the Science
Report 12
16.2.1 Comments on the Review of Literature Published Since the Science Report's Release .... 12
16.2.2 Consideration of Additional Relevant Science/Literature 14
16.3 Climate Change 28
16.3.1 Effects of Climate Change in Specific Regions and Specific Aquatic Resource Types 28
16.3.2 Comments on the Use of Climate Change Science in Developing Policy 29
16.4 Comments on the Importance of Clean Water for Humans and Wildlife 31
16.4.1 Comments on the Importance of Clean Water to Humans 31
16.4.2 Comments on the Importance of Clean Water to Wildlife 32
16.5 Additional Literature Provided to the Agencies 33
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16
Technical Support Document and Other Science
This topic includes comments related to the science supporting the proposed rule, specific to the
Technical Support Document for the Proposed Rule, the 2015 EPA report Connectivity of Streams and
Wetlands to Downstream Waters: A Review and Synthesis of the Scientific Evidence1 (hereinafter, the
"Science Report") and related literature, climate change science, the functions of multiple aquatic
resources, and the role of science in this rulemaking. Comments on the science supporting individual
categories of waters, such as tributaries, wetlands, and other water types, are in the Response to
Comments sections for those specific topics.
16.1 Technical Support Document and the Science Report
16.1.1 Support for the Technical Support Document and the Science Report
Several commenters wrote in support of the Technical Support Document for the Proposed "Revised
Definition of 'Waters of the United States'" Rule (Proposed Rule TSD) and the Science Report. More
specifically:
Several commenters remarked that the agencies should follow and incorporate the science
outlined in the Science Report, and discussed the connections between tributaries, wetlands, and
downstream waters, and the importance of headwaters, ephemeral and intermittent streams,
"isolated" wetlands such as prairie potholes and vernal pools, and groundwater.
One commenter expressed support for the Science Report and stated that the Report and
continuing scientific research provide the basis for why some headwater tributaries, wetlands, and
floodplains warrant protection as "waters of the United States."
One commenter expressed support for the Science Report, explicitly referencing attributes of
floodplains that support the vital ecosystem functions of riverine systems, including connectivity,
variable flow/inundation, spatial extent, habitat, and structural diversity.
One commenter expressed support for the agencies' respect for and application of accepted
science in the Proposed Rule TSD. The commenter further stated that the proposed rule is an
appropriate interim measure to guide the agencies' implementation of the Clean Water Act while
they work to develop a new, updated definition of "waters of the United States" that addresses
environmental justice and climate change concerns.
One commenter expressed support for the tools included in the Proposed Rule TSD including
remote sensing, United States Geological Survey (USGS) and topographical maps, aerial
photography, gage data, satellite imagery, watershed studies, modeling tools, scientific literature,
and more.
Agencies' Response: The agencies agree with commenters who stated that the Proposed
Rule TSD and the Science Report provide a strong scientific basis for the rule. The
agencies' interpretation of the Clean Water Act's scope in this final rule is informed by the
best available peer-reviewed science, including on the connectivity and effects that streams,
wetlands, and open waters have on the chemical, physical, and biological integrity of
traditional navigable waters, the territorial seas, or interstate waters. See Section III of the
1 U.S. Environmental Protection Agency. 2015. Connectivity of Streams and Wetlands to Downstream Waters: A
Review and Synthesis of the Scientific Evidence (Final Report). EPA/600/R-14/475F. U.S. Environmental Protection
Agency, Washington, D.C. ("Science Report").
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Technical Support Document2 for additional detail of the scientific literature and the
agencies' reasoning in support of the final rule.
Regarding the comment on a subsequent rulemaking, in the preamble to the proposed rule,
the agencies stated that they would consider changes through a second rulemaking that they
anticipated proposing in the future, which would build upon the foundation of this rule. The
agencies have concluded that this rule is durable and implementable because it is founded
on the familiar framework of the 1986 regulations, fully consistent with the statute,
informed by relevant Supreme Court decisions, and reflects the record before the agencies,
including consideration of the best available science, as well as the agencies' expertise and
experience implementing the pre-2015 regulatory regime. The agencies may consider
further refinements in a future rule to address implementation or other issues that may
arise.
The agencies also appreciate the comment expressing support for the tools included in the
Proposed Rule TSD. As discussed in the Final Rule Preamble and in Section IV of the
Technical Support Document, the agencies have identified a variety of implementation
guidance, tools, and methods available for use to determine if a water is jurisdictional under
the final rule. The agencies conclude that the final rule, together with the preamble and
existing tools, provides sufficient clarity to allow consistent implementation of the final rule.
16.1.2 Criticisms of the Technical Support Document and the Science Report
Some commenters expressed concern with the Proposed Rule TSD or the Science Report.
One commenter claimed that because the preamble to the proposed rule states that "[a]ll tributary
streams, including perennial, intermittent, and ephemeral streams, are chemically, physically, and
biologically connected to larger downstream waters via channels and associated alluvial deposits
where water and other materials are concentrated, mixed, transformed, and transported" (86 FR
69390), that the agencies have implied that all ephemeral and intermittent streams are
jurisdictional.
One commenter argued that the Science Report and the Proposed Rule TSD do not scientifically
support the unique geography and climate of Alaska. The commenter added that the maps and
illustrations in the Science Report do not even depict Alaska.
A few commenters stated that it is inappropriate for the agencies to draw conclusions about
streamflow in the arid Southwest based on the San Pedro River study. One of these commenters
suggested that the Science Report and the Proposed Rule TSD are overly broad and not especially
relevant to determining jurisdiction, especially with respect to ephemeral drainages in the arid
Southwest.
2 Note that in this document, references to the Technical Support Document for the Proposed "Revised Definition of
'Waters of the United States'" Rule will be denoted as "Proposed Rule TSD" while references to the Technical
Support Document for the Final "Revised Definition of 'Waters of the United States Rule will be denoted as
"Technical Support Document."
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One commenter opined that most of the discussion and information in the Science Report and the
Science Advisory Board's (SAB) review of the Science Report3 "focused on 'streams' and there
was very little consideration given to the dry ephemeral drainages of the arid West."
One commenter opined that the agencies have failed to meaningfully respond to the SAB
Review's numerous suggestions of ways to improve the Science Report. The commenter also
critiqued the proposal by remarking that the agencies should address comments from the SAB
Review by defining which connections are "significant" and providing metrics for determining
whether connections establish a "significant nexus." The commenter also claimed that the lack of
clarity in the proposed rule and Proposed Rule TSD around how to determine the significance of
the various factors and functions "suggests that there is no gradient of hydrologic connection that
would in fact be determined to be 'insubstantial and speculative.'"
Agencies' Response: The agencies disagree with commenters who stated that the rule is not
supported by science. The agencies' interpretation of the Clean Water Act's scope in this
final rule is informed by the best available peer-reviewed science, including on the
connectivity and effects that streams, wetlands, and open waters have on the chemical,
physical, and biological integrity of traditional navigable waters, the territorial seas, or
interstate waters. The Science Report provides much of the scientific basis of the final rule,
and the agencies were also informed by other sources of scientific information and
literature, particularly for topics that were not addressed in the Science Report, and by
their review of the scientific literature that had been published since the Science Report's
publication. See Section III of the Technical Support Document for additional detail of the
scientific literature and the agencies' reasoning in support of the final rule.
The agencies disagree that the proposed rule implied that all intermittent and ephemeral
streams would be jurisdictional as tributaries. The agencies have made clear in the proposal
and the final rule that streams must meet the agencies' longstanding interpretation of
tributary to be assessed as paragraph (a)(3) tributaries, and that only those tributary
streams that meet the relatively permanent standard or the significant nexus standard are
jurisdictional as tributaries. Consistent with the pre-2015 regulatory regime and prior rules
defining "waters of the United States," jurisdictional decisions under the final rule are
made on a case-specific basis, with consideration of site-specific circumstances. See Final
Rule Preamble Section IV.C.4 for additional discussion of the tributary provision under the
final rule.
The agencies disagree with the commenter who stated that the Science Report and the
Proposed Rule TSD do not scientifically support the unique geography and climate of
Alaska, and with commenters who stated that the agencies' conclusions on ephemeral
streams in the arid Southwest are overly board, including allegations that the agencies
relied only on the San Pedro River. The agencies also disagree with the commenter who
implied that ephemeral streams in the arid West are not "streams" and who claimed that
the Science Report and SAB Review gave very little consideration to such ephemeral
streams. The Science Report synthesized the available evidence from peer-reviewed studies
3 U.S. Environmental Protection Agency Science Advisory Board. 2014. SAB review of the draft EPA report
Connectivity of Streams and Wetlands to Downstream Waters: A Review and Synthesis of the Scientific Evidence
(October 17, 2014). EPA-SAB-15-001, U.S. Environmental Protection Agency, Washington, D.C. ("SAB Review").
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in different climate-landscape settings to identify the range of functions provided by
streams, floodplain wetlands and open waters, and non-floodplain wetlands and open
waters in the United States. This included studies from Alaska and studies from the arid
Southwest other than the San Pedro River study. Additionally, the San Pedro case study in
Science Report Appendix Section B.5.4 does not focus solely on the San Pedro River itself
but evaluates the entire tributary network within the San Pedro River Basin, including the
Walnut Gulch sub-watershed. Walnut Gulch is a highly studied tributary of the San Pedro
River, and Science Report Section 3 (Streams: Physical, Chemical, and Biological
Connections to Rivers) also describes findings from Walnut Gulch. Furthermore, the
Science Report also summarizes findings from other Southwestern tributaries. Goodrich et
al. (2018),4 which is cited in the Proposed Rule TSD and the Technical Support Document,
provides additional citations and support regarding streams in the arid Southwest. In
addition, in response to the SAB Review, more literature regarding the importance of
episodic connections between ephemeral and intermittent streams and downstream waters
was added to Appendix Section B.5 (Southwestern Intermittent and Ephemeral Streams)
and Section 3 (Streams: Physical, Chemical, and Biological Connections to Rivers) of the
final Science Report. These sections and others in the Science Report highlight
consideration of scientific research on ephemeral streams in the arid West. Similarly, the
SAB Review contains consideration of ephemeral streams in the arid West. The SAB
Review states, "Important cumulative effects are exemplified by ephemeral flows in arid
landscapes, low-frequency events that may nevertheless provide most of the subsidies to
downgradient waters" (SAB Review at 22; citations omitted). The SAB Review also
concluded "the review and synthesis of the literature describing connectivity of streams to
downstream waters reflects the pertinent literature and is well grounded in current science.
The literature review provides strong scientific support for the conclusion that ephemeral,
intermittent, and perennial streams exert a strong influence on the character and
functioning of downstream waters and that tributary streams are connected to downstream
waters." (SAB Review cover letter at 3). In addition, the agencies are not using the Science
Report or the Technical Support Document to make categorical determinations in the final
rule that tributaries, their adjacent wetlands, or waters evaluated under paragraph (a)(5)
are jurisdictional based on the significant nexus standard. Consistent with the pre-2015
regulatory regime, jurisdictional decisions under the final rule are made on a case-specific
basis, with consideration of site-specific circumstances.
The agencies disagree with the commenter who stated that the agencies had failed to
address the SAB Review's suggestions to improve the Science Report. Though the SAB
Review of the Science Report is outside the scope of this rulemaking, revisions were made to
the final Science Report in response to the review, including Section 2.4.6, which is a
summary of the literature on metrics and approaches for measuring connectivity and
supplemented existing text in the draft report on estimating and understanding
connectivity. These revisions did not have a significant bearing or effect on the report's
overall assessment of connectivity or conclusions. Rather, the revisions ensure that the
Science Report includes a more complete evaluation of the dynamics of connectivity and the
available literature. Although outside the scope of this rulemaking, EPA's Response to
4 Goodrich, D.C., W.G. Kepner, and L.R. Levick. 2018. "Southwestern intermittent and ephemeral stream
connectivityJournal of the American Water Resources Association 54(2): 400-422.
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Comments from the SAB Review is also available at
http://cfpub.epa.gov/ncea/cfm/recordisplay.cfm?deid=296414.
The agencies also disagree with the commenter who claimed the agencies did not address
comments from the SAB Review by defining in the rule what is "significant" and providing
the agencies' approach for determining whether connections establish a "significant nexus."
The definition of "significantly affect" in the final rule is derived from the objective of the
Clean Water Act and is informed by and consistent with Supreme Court case law. It is also
informed by the agencies' technical and scientific judgment and supported by the best
available science regarding the functions provided by upstream waters to paragraph (a)(1)
waters relevant to achieving the Clean Water Act's objective. The agencies disagree "that
there is no gradient of hydrologic connection that would in fact be determined to be
'insubstantial and speculative.'" The agencies have established a definition of "significantly
affect" in this rule, provided additional guidance on applying the significant nexus
standard, and identified implementation tools and resources that will work together to
provide clarity and further consistency in implementing the significant nexus standard. The
agencies have concluded that these actions, along with the agencies' experience making
determinations under the significant nexus standard, will increase the clarity and
consistency of determinations of jurisdiction. The factors in the final rule are readily
understood criteria that influence the types and strength of chemical, physical, or biological
connections and associated effects on paragraph (a)(1) waters. Section IV.C.9.C of the Final
Rule Preamble provides the agencies' general approach to implementing the definition of
"significantly affect" for purposes of the significant nexus standard, including evaluation of
the functions and factors. See Sections IV.C.4, IV.C.5, IV.C.6 of the Final Rule Preamble
for additional information on how the agencies will implement the significant nexus
standard for tributaries, adjacent wetlands and paragraph (a)(5) waters, respectively. See
also the agencies' response to comments in Section 12.2.
The agencies recognize that regional differences in climate, geology, topography, soils, and
other variables (such as vegetation and land use) mean that the functions and connections
present in any given water (when considered alone or in combination with similarly situated
waters in the region) will likely be a subset of those functions and connections identified in
the Science Report. Furthermore, the agencies have clearly identified the specific functions
and factors to be considered in a significant nexus determination under the rule. See the
definition of "significantly affect" at paragraph (c)(6).
The agencies are deeply familiar with the variations in climate, geology, and terrain within
and among watersheds and over time that affect the functions performed by streams, open
waters, and wetlands and, therefore, the chemical, physical, and biological integrity of
paragraph (a)(1) waters. The agencies' field staff have gained extensive familiarity and
practical experience making decisions on jurisdiction based on the significant nexus
standard, using national and regional field methods, literature, datasets, models, and tools
that are required to make such determinations. The agencies' immersion in the science,
along with the practical expertise developed through more than a decade of case-specific
"significant nexus" determinations across the country, have helped the agencies determine
which waters have a significant nexus and where to draw boundaries demarking the
"waters of the United States." Further, based on the agencies' experience, many waters
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under this rule will not have a significant nexus to paragraph (a)(1) waters, and thus will
not be jurisdictional under the Clean Water Act.
16.1.3 General Comments on the Agencies' Use of Science
Many commenters offered general support for a rule that is supported by science.
Several commenters requested that the agencies incorporate consensus-driven, evidence-based
science in the rulemaking process.
Several commenters stated that scientific support for the proposed rule should be one of the most
important factors that the agencies rely on.
One commenter supported the reliance on science to establish the proposed rule. They also wrote
in support of extending the protection of water quality beyond pollutants to include hydrological
effects, biological dependencies, and habitat needs.
One commenter urged the agencies to develop a clear, science-based rule based on their expertise
and the latest science on hydrologic and functional connectivity.
One commenter asserted that strong regulations are needed now based on water quality
information. They specifically mentioned lakes and ponds, rivers and streams, wetlands, and
other waters.
One commenter stated that the Science Report explains the importance of small or temporary
streams and non-floodplain wetlands.
A few commenters supported the watershed-scale approach in the proposed rule, relative to the
2020 NWPR, to ensure adequate protection of a broad array of ecosystem services. They
discussed the importance of evaluating headwater streams, ephemeral streams, and wetlands
lacking a surface connection in a watershed context.
One commenter voiced their support for a broad approach to defining a linkage of a water or
wetland to the chemical, physical, and biological integrity of a traditional navigable water by
including both surface and shallow subsurface flow.
One commenter stated that the science supports categorical protections to all tributaries, adjacent
wetlands, and "other waters," and restoring cross references to "other waters" in the tributaries
and adjacent wetlands categories.
One commenter stated that the agencies must consider the National Oceanic and Atmospheric
Administration's (NOAA) Atlas 14's updated rainfall frequency values when defining the proper
scope of jurisdiction.
Other commenters offered general comments that propose limiting or eliminating the use of science in
defining "waters of United States."
One commenter expressed concern that the agencies will use the Science Report to regulate
waters beyond their authority.
A few commenters argued that the proposed rule relies too much on science in a way that is not
compatible with legal limitations and case law. They referenced the terms "connection" and
"significant nexus" and stated that jurisdiction under the proposed rule is too broad.
One commenter stated that the agencies should not consider the Science Report because
interpretations of a statute must be founded on statutory text and not scientific studies.
One commenter supported the use of relevant science to determine a definition of "waters of the
United States," but also encouraged the agencies to "rebalance" the proposed rule and consider
the use of science, case law, and statute when determining jurisdiction.
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One commenter wrote that it is not only important to base the definition of "waters of the United
States" on science, but also on the constraints established by statute and judicial precedent. They
further wrote that individual determinations should be based on real evidence and not
assumptions or speculations.
One commenter argued that the definition of "waters of the United States" must be grounded in a
legal analysis of the limits on Clean Water Act jurisdiction reflected in the statute and Supreme
Court case law.
Some commenters provided input on how science supports including certain categories of aquatic
resources as "waters of the United States."
One commenter wrote that adjacent and neighboring wetlands without a hydrological surface
water connection and adjacent lakes and ponds that are not classified as tributaries should all be
considered jurisdictional.
One commenter wrote that the agencies should create additional categories of "waters of the
United States" that do not require a case-specific analysis supported by scientific literature.
One commenter requested that altered or urban rural waterbodies be clearly defined and
protected, and stated that altered waterbodies still can carry nutrients, sediment, and pollution.
Some commenters discussed other scientific topics related to the Science Report.
One commenter stated that the agencies need to incorporate the science of connectivity as
described in the Science Report more completely into the rulemaking.
Another commenter argued that the Science Report contained a conservative view of non-
floodplain waters' downstream connectivity. The commenter further discussed the degrees of
connectivity outlined in the Science Report.
One commenter listed several examples from the Science Report and 2015 Clean Water Rule
Technical Support Document to discuss how seemingly "geographically isolated" Texas coastal
prairie wetlands can be collectively connected both geographically and hydrologically to
downstream waters.
One commenter stated that the Science Report and SAB Review are limited to examining the
connectivity of waters with a significant nexus to downstream waters, and that the agencies
should not use the significant nexus standard as a basis to categorically exclude all tributaries,
adjacent wetlands, and "other waters" as jurisdictional waters in the definition because of this
bias.
One commenter asserted that the agencies must address the corresponding frequency, duration, and water
quality-based risk factors of short-term wet weather (e.g., storm water) events that should be applied to
jurisdictional waters. The commenter also asked how the agencies will establish water quality standards
and monitoring requirements for ephemeral streams under short-term wet weather conveyance conditions
and recommended that statistical stormwater flow boundary conditions be evaluated for each of those
cases.
One commenter opined that the agencies relied on only a subset of available scientific evidence and
emphasized those aspects of the scientific record that support more expansive federal jurisdiction.
Agencies' Response: The agencies agree with commenters who offered general support for a
rule that is supported by science. The agencies' interpretation of the Clean Water Act's
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scope in this final rule is informed by the best available peer-reviewed science, including on
the connectivity and effects that streams, wetlands, and open waters have on the chemical,
physical, and biological integrity of traditional navigable waters, the territorial seas, or
interstate waters. The Science Report provides much of the scientific basis of the final rule,
and the agencies were also informed by other sources of scientific information and
literature, particularly for topics that were not addressed in the Science Report, and by
their review of the scientific literature that had been published since the Science Report's
publication. See Section III of the Technical Support Document for additional detail
regarding the scientific literature and the agencies' reasoning in support of the final rule.
The agencies agree with the commenter who stated that the Science Report explains the
importance of small or temporary streams and non-floodplain wetlands. See Science Report
Chapters 3, 4, and 6. The agencies acknowledge commenters who supported the watershed-
scale approach to aggregation in the proposed rule and who advocated for evaluating
waters in a watershed context. In implementing the significant nexus standard under the
final rule, all tributaries and adjacent wetlands within the catchment area of the tributary
of interest will be analyzed as part of the significant nexus analysis. See Section IV.C.4.c.iii
of the Final Rule Preamble (discussing how to evaluate whether a tributary meets the
significant nexus standard). The agencies acknowledge the comment regarding surface and
shallow subsurface flow as an important connection. The agencies' final rule allows for
consideration of an unbroken surface or shallow subsurface hydrologic connection to a
jurisdictional water to demonstrate adjacency, consistent with longstanding practice. See
Section IV.C.5 of the Final Rule Preamble (addressing the final rule's approach to adjacent
wetlands). Separately, for purposes of the significant nexus standard, the agencies will
consider "[hjydrologic factors, such as the frequency, duration, magnitude, timing, and rate
of hydrologic connections, including shallow subsurface flow" (paragraph (c)(6)(ii)(B) of the
final rule regulatory text) when determining if a water has a material influence on
traditional navigable waters, the territorial seas, or interstate waters. See Section IV.C.9 of
the Final Rule Preamble (discussing the final rule's definition of "significantly affect"). The
agencies appreciate the commenter who suggested that the agencies consider NOAA Atlas
14's updated rainfall frequency values and recognize that climate change is affecting storm
frequency and intensity in some areas. However, the agencies disagree that data providing
the historical frequency of rainfall events are appropriate for determining the proper scope
of jurisdiction.
The agencies disagree with commenters who stated that the agencies will use the Science
Report to regulate waters beyond their authority; that the agencies have relied on science in
a way that is incompatible with legal limitations and case law; and that the agencies should
not consider the science reviewed in the Science Report in defining "waters of the United
States." See also the agencies' response to comments in Section 2.1 (addressing the agencies'
reliance on the Clean Water Act's statutory objective in developing the final rule). While
the agencies agree with commenters who stated that scientific evidence is important, the
agencies also acknowledge that science is not the only factor that they must consider when
defining "waters of the United States." As discussed in Final Rule Preamble Section IV.A,
the agencies are finalizing a definition of "waters of the United States" that is within the
agencies' authority under the Act; that advances the objective of the Clean Water Act; that
establishes limitations that are consistent with the statutory text, supported by the scientific
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record, and informed by relevant Supreme Court decisions; and that is both familiar and
implementable. As the agencies charged with construing the statute, EPA and the Army
Corps of Engineers must develop the outer bounds of the scope of the Clean Water Act. The
agencies agree with commenters who stated that science alone cannot dictate where to draw
the line defining "waters of the United States." But science is critical to understanding what
scope of jurisdiction furthers Congress's objective to restore and maintain the chemical,
physical, and biological integrity of the nation's waters and properly determining which
waters are the subject of federal jurisdiction due to their effects on paragraph (a)(1) waters.
Thus, the agencies disagree with the commenter who implied that the agencies' proposed
rule did not properly balance science, case law, and the statute. The agencies have
concluded that the rule establishes limits that appropriately draw the boundary of waters
subject to federal protection.
The agencies appreciate comments providing input on how science supports including
certain categories of aquatic resources as "waters of the United States." However, this final
rule, unlike the 2015 Clean Water Rule, is not based on categorical significant nexus
determinations. Instead, the final rule is founded on the longstanding and familiar 1986
regulations and includes a framework for applying the relatively permanent and significant
nexus standards to certain categories of waters in the rule. See Final Rule Preamble Section
IV.B.l for a discussion of the agencies' conclusion that the 2015 Clean Water Rule, while
designed to advance the objective of the Clean Water Act, is not the best alternative to meet
the agencies' policy goals; see Final Rule Preamble Section IV.B for the agencies'
consideration of alternatives to the final rule.
The agencies acknowledge the commenter who argued that the Science Report contained a
conservative view of the downstream connectivity of non-floodplain waters. The agencies
have concluded that the Science Report accurately synthesized the peer-reviewed, published
scientific information that was available at the time of its publication regarding the
connectivity and effects of non-floodplain waters on downstream waters. The agencies
recognize that since the publication of the Science Report in 2015, the published literature
has expanded scientific understanding and quantification of the functions of these waters
that affect the integrity of larger waters, including traditional navigable waters, the
territorial seas, and interstate waters, particularly in the aggregate. More recent literature
(i.e., 2014-present, as some literature from 2014 and 2015 may not have been included in the
Science Report) has determined that non-floodplain wetlands can have demonstrable
hydrologic and biogeochemical downstream effects, such as decreasing peak flows,
maintaining baseflows, and performing nitrate removal, particularly when considered
cumulatively. The Science Report's major conclusions state that "[e]valuations of individual
[non-floodplain] wetlands or groups of wetlands, however, could be possible through case-
by-case analysis," and the agencies' in the final rule will allow for such consideration on a
case-by-case basis for such waters under other the (a)(4) adjacent wetlands category or the
(a)(5) category for waters that do not meet the jurisdictional criteria under other categories
of the final rule. Consistent with the pre-2015 regulatory regime, jurisdictional decisions
under the final rule are made on a case-specific basis, with consideration of site-specific
circumstances. Thus site-specific information, including any relevant literature (not limited
to just the Science Report), would be considered.
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The agencies acknowledge the commenter who stated that Texas coastal prairie wetlands
can be collectively connected both geographically and hydrologically to downstream waters.
Such information can be used for a case-specific analysis under the final rule of whether
such waters meet either the relatively permanent standard or the significant nexus standard
and are therefore "waters of the United States." See Final Rule Preamble Section IV.C for
additional information on implementation of the final rule. With respect to the comment
that the significant nexus standard should not be used as a basis to categorically exclude all
tributaries, adjacent wetlands, or waters that do not meet the jurisdictional criteria under
other categories of the final rule, the agencies are not using significant nexus standard to
categorically exclude waters under this rule. The significant nexus standard does represent
a limitation on the scope of jurisdictional waters. Thus tributaries, adjacent wetlands, or
waters assessed under paragraph (a)(5) that do not meet the jurisdictional criteria under
the final rule will be determined not to meet the standards established under the rule and
will therefore not be "waters of the United States." Under the final rule, tributaries meeting
either the relatively permanent standard or significant nexus standard are jurisdictional.
Based on the agencies' longstanding exclusions and practice, the final rule establishes
exclusions for certain waters and features under paragraph (b), where such waters and
features are not paragraph (a)(1) waters, even if they otherwise meet the jurisdictional
criteria to be impoundments, tributaries, adjacent wetlands, or paragraph (a)(5) waters. See
Section IV.C. of the Final Rule Preamble for additional information about the categories of
"waters of the United States" and exclusions under the final rule.
In regard to the commenter who asserted that the agencies must address the corresponding
frequency, duration, and water quality-based risk factors of short-term wet weather
conditions, the agencies agree that frequency and duration of surface flow are relevant to
the significant nexus standard, as well as the relatively permanent standard. The agencies
do not agree that frequency and duration of surface flow are the only factors relevant to the
significant nexus standard, as demonstrated by the factors in the final rule's definition of
"significantly affect" in paragraph (c)(6). Additionally, while water quality standards and
monitoring requirements are outside the scope of this rulemaking, the agencies note that for
many years EPA has reviewed and approved state water quality standards for ephemeral
waters under Clean Water Act section 303(c), and authorized Tribes and States have
developed water quality standards for broad classifications of waters, including ephemeral
waters. In addition, as described in Final Rule Preamble Section IV.C.9.b, the Clean Water
Act itself does not require that "waters of the United States" must be identified based on a
quantitative or statistical thresholds.
The agencies disagree with the commenter who implied that the agencies have relied on
only favorable evidence from the scientific record. The agencies have considered the totality
of the scientific evidence. The Science Report, which forms much of the scientific basis for
the final rule, is a peer-reviewed synthesis of over 1,300 peer-reviewed scientific articles,
and the report's major conclusions are based on the totality of the scientific evidence. In
addition, the agencies' assessment of the literature published since the report's release has
found that the vast majority of the more recent literature was supportive of or augmented
the report's conclusions. Literature provided to the agencies during the public comment
period has been reviewed and incorporated where appropriate. See the agencies' response
to comments in Section 16.2.2. The agencies found that the peer-reviewed literature
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published since 2014 provided via public comments either do not address the report's
conclusions or were supportive of the report's conclusions. See also Section I.C.vi and
Appendix C3 of the Technical Support Document. Unlike in the 2015 Clean Water Rule, the
agencies are not making any categorical determinations of significant nexus in the final
rule. Rather, jurisdictional decisions under the final rule will be made on a case-specific
basis with consideration of site-specific circumstances and site-specific information,
including any relevant literature.
16.2 Review of the Scientific Literature Published Since the Release of the Science
Report
16.2.1 Comments on the Review of Literature Published Since the Science Report's Release
A few commenters provided feedback on the agencies' review and summarization of scientific literature
published since the Science Report's publication and discussion included in section II.C of the Technical
Support Document for the proposed rule.
One commenter remarked that since the 2015 Clean Water Rule, the agencies have identified
more than 1,200 studies demonstrating connections between waters. They stated that nothing has
been done to creditably challenge the agencies' own findings and evidence that support broad-
based protections.
One commenter argued that the agencies drew conclusions when reviewing the Science Report
that were based solely on the review of abstract papers and this creates some uncertainty in the
agencies' findings.
One commenter argued that the proposed rule reflects scientific developments made since the
Science Report which warrants an extended comment period prior to rulemaking.
One commenter questioned the credibility of the agencies' use of science, given that the "same
Agencies can publish such radically different rules in such a short [2015 to 2021] time with each
iteration 'supported by the science.'"
Agencies' Response: The agencies agree with commenters who state that relevant literature
published since the release of the Science Report supports the conclusions of that report,
and that literature on ephemeral streams and non-floodplain wetlands has expanded the
agencies' understanding of the functions by which these waters affect the integrity of larger
bodies of water, particularly when evaluated in the aggregate. Section I.C.i of the Technical
Support Document details the agencies' systematic review of abstracts (summaries) of
12,659 scientific papers on topics reviewed in the Science Report. The purpose of this effort
was to screen new publications for information that may not have been considered in the
Science Report or contained evidence that contradicted the major conclusions of that
report. Systematic review avoids bias in the selection of literature to be screened and uses
explicit, reproducible methods to evaluate findings. Section I.C.i of the Technical Support
Document also summarizes results from the screened papers. This approach enabled the
agencies to efficiently screen results from a large number of publications to search for new
evidence relating to the Science Report. The scientific papers published since 2014 and
reviewed by the agencies provided overwhelming support substantiating the findings and
conclusions of the Science Report, and the use of systematic review increased confidence
Revised Definition of "Waters of the United States" - Response to Comments Document
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that recent research does not contradict the main findings from that report (see Section
I.C.i of the Technical Support Document).
The agencies disagree with the commenter who opined that the proposed rule reflects
scientific developments made since the Science Report that warrant an extended comment
period prior to rulemaking. Since the release of the Science Report, additional published
peer-reviewed scientific literature has strengthened and supplemented the report's
conclusions. The agencies' analysis of the scientific literature published since 2014 found
overwhelming support for the major conclusions of the Science Report. The small number
of papers that the agencies screened and found to individually "refute" or "neither support
or refute" the major conclusions of the report have not provided sufficient evidence to
contradict the synthesis of scientific literature in those major conclusions. In addition, the
Administrative Procedure Act (APA) does not specify a minimum number of days for
accepting comments on a proposed rule. The agencies complied with their obligation under
the APA to provide a reasonable length of time for interested parties to comment on the
proposed rule. See also the agencies' response to comments in Section 5.1 for responses to
comments on the comment period.
The agencies acknowledge that, while the scientific foundation for the rulemaking has not
changed from the 2015 Clean Water Rule, the definition of "waters of the United States"
has changed multiple times. However, the agencies disagree with the commenter who
questioned the credibility of the agencies' use of science in this rulemaking. The agencies
agree that the 2015 Clean Water Rule was informed by the best available science and was
designed to advance the objective of the Clean Water Act but decided against returning to
the 2015 Clean Water Rule for the reasons set forth in Section IV.B.l of the Preamble to the
Final Rule. Following a careful review of the 2020 NWPR and its administrative record
including the text, structure, and history of the Clean Water Act; relevant Supreme Court
case law; concerns raised by co-regulators and stakeholders; and issues raised in ongoing
litigation challenging the 2020 NWPR, the agencies concluded that the 2020 NWPR did not
properly consider the extensive scientific evidence demonstrating the interconnectedness of
waters and their downstream effects, thereby undermining Congress's objective to restore
and maintain the chemical, physical, and biological integrity of the nation's waters. See
Section II.B.iii of the Technical Support Document. The 2020 NWPR's exclusion of major
categories of waters from the protections of the Clean Water Act, specifically in the
definitions of "tributary" and "adjacent wetlands," runs counter to the scientific record
demonstrating how such waters can affect the integrity of downstream waters. See Section
II.B.i of the Technical Support Document. In contrast, the agencies have concluded that the
final rule is informed by the best available science. As discussed in Final Rule Preamble
Section IV.A, the agencies are finalizing a definition of "waters of the United States" that is
within the agencies' authority under the Act; that advances the objective of the Clean
Water Act; that establishes limitations that are consistent with the statutory text, supported
by the scientific record, and informed by relevant Supreme Court decisions; and that is
both familiar and implementable. Science alone cannot dictate where to draw the line
defining "waters of the United States" but science is critical to understanding what scope of
jurisdiction furthers Congress's objective to restore and maintain the chemical, physical,
and biological integrity of the nation's waters and properly determining which waters are
the subject of federal jurisdiction due to their effects on paragraph (a)(1) waters.
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16.2.2
Consideration of Additional Relevant Science/Literature
As part of the notice and comment process, the agencies solicited comment on the scientific literature
contained in Appendix C of the Proposed Rule TSD and requested the public provide additional scientific
literature and references relevant to the Science Report's conclusions on the connectivity and effects of
streams, floodplain wetlands and open waters, and non-floodplain wetlands and open waters on the
chemical, physical, and biological integrity of larger downstream waters. Commenters provided 43
citations of peer-reviewed scientific literature that have been published since 2014 but were not included
in the agencies' initial review (as discussed in Section II.C. of the Proposed Rule TSD) of literature
published since 2014.
Agencies' Response: The agencies appreciate commenters who provided additional citations
of scientific literature published since the Science Report's release. The agencies reviewed
those citations submitted as part of the notice and comment process. Fifty-one references
provided by commenters (see Table 1) were already included in Appendix C of the
Proposed Rule TSD (e.g., Cohen et al. 2016s and Rains et al. 20166) and were not reviewed
because they had already been screened by the agencies, as described further in section
I.C.i. of the Technical Support Document. Other submitted references were determined to
not meet the agencies' criteria (i.e., they were not published in or after 2014, they were not
peer-reviewed, or the agencies could not ascertain if the references had undergone peer
review; see Table 2). Other references were determined to not be relevant to the conclusions
of the Science Report (i.e., the findings of the paper were outside the context described in
Section I.C of the Technical Support Document). The agencies have considered such
references for relevance to other aspects of the Technical Support Document and have
included such relevant references where appropriate (e.g., where they were relevant to
implementation of the final rule).
The agencies assessed 47 peer-reviewed citations published in or after 2014 that were
submitted as part of the public comment process. The agencies were able to discern the
appropriate and relevant aquatic system typology in 22 of the papers. The agencies were
able to assess a conclusion on findings relevant to the Science Report in 13 of those 22
papers. In all 10 citations where sufficient information was available, the conclusions of the
Science Report were substantiated by these scientific references. See Section I.C.vi and
Appendix C3 of the Technical Support Document for additional information.
The following tables list the literature published since 2014 that was provided to the
5 Cohen, M.J., I.F. Creed, L. Alexander, N.B. Basu, A.J.K. Calhoun, C. Craft, E. D'Amico, E. Dekeyser, L. Fowler,
H.E. Golden, J.W. Jawitz, P. Kalla, L.K. Kirkman, C.R. Lane, M. Lang, S.G. Leibowitz, D.B. Lewis, J. Marton,
D.L. McLaughlin, D.M. Mushet, H. Raanan-Kiperwas, M.C. Rains, L. Smith, and S.C. Walls. 2016. "Do
geographically isolated wetlands influence landscape functions?" Proceedings of the National Academy of Sciences
of the United States of America 113(8): 1978-1986.
6 Rains, M.C., S.G. Leibowitz, M.J. Cohen, I.F. Creed, H.E. Golden, J.W. Jawitz, P. Kalla, C.R. Lane, M.W. Lang,
and D.L. McLaughlin. 2016. "Geographically isolated wetlands are part of the hydrological landscape."
Hydrological Processes 30(1): 153-160.
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agencies in response to their request in the Proposed Rule TSD. Table 1 lists the 44 citations
provided to the agencies that was already cited in Appendix CI of the Proposed Rule TSD.
Table 2 lists the 15 citations provided by commenters that did not meet the agencies'
criteria for review. These references were determined to not meet the agencies' criteria
because the publication date was unknown; the references were not peer-reviewed; or the
agencies could not ascertain if the references had undergone peer review. If the agencies
found that the citation did not meet one of the criteria, they may not have evaluated it for
relevance to the Science Report. Note that some of these papers were cited in the Proposed
Rule TSD (e.g., regarding implementation or topics outside the scope of the Science Report)
but were not cited in Appendix CI of that document.
Table 3 contains the 34 citations provided to the agencies during the public comment period
but for the which the agencies did not have sufficient information to discern system
typology (e.g., stream, non-floodplain wetlands and open waters, floodplain wetlands and
open waters); the system typology was not applicable to the Science Report (e.gestuarine
wetlands); or that were found not to be relevant to the conclusions of the Science Report.
Note that if the agencies found that the system typology was not relevant or not discernible,
they may not have also determined relevance to conclusions of the Science Report and vice
versa. Note that some of these papers were cited in the Proposed Rule TSD (e.g., regarding
implementation or topics outside the scope of the Science Report) but were not cited in
Appendix CI of that document and thus were not part of the agencies' initial screening of
peer-reviewed literature published since 2014.
Table 2 in Appendix C3 of the Technical Support Document contains the 13 references
provided to the agencies during the public comment period that were peer-reviewed and
published in or after 2014 and that the agencies found were relevant to the conclusions of
the Science Report. See also Section I.C.vi and Appendix C of the Technical Support
Document.
In addition, four references were provided to the agencies that were included in the list of
37 citations the agencies had identified in Appendix C2 of the Proposed Rule TSD as being
potentially relevant to the conclusions of the Science Report, but that were not identified as
part of the agencies' initial screening process (see Appendix C3 of the Technical Support
Document). The agencies have since reviewed those additional citations for relevance to the
conclusions of the Science Report. Of the four citations that were provided to the agencies
in timely public comments and that were cited in Appendix C2 of the Proposed Rule TSD,
one reference was found not have the relevant system topology and was found to not to be
relevant to the conclusions of the report (Dages, C., A. Samouelian, S. Negro, V. Storck, O.
Huttel, and M. Voltz. 2015. "Seepage patterns of Diuron in a ditch bed during a sequence of
flood events." Science of The Total Environment 537: 120-128.
https://www.sciencedirect.com/science/article/pii/S0048969715304721). One refence as
found to have relevant system typology but was found not to be relevant to the Science
Report's conclusions (Gala, T.S., and D. Young. 2021. "Geographically Isolated
Depressional Wetlands - Hydrodynamics, Ecosystem Functions and Conditions." Applied
Ecology and Environmental Sciences 3 (4): 108-116. http://pubs.sciepub.com/.) Two
references were found to have relevant system typology and were relevant to the
Revised Definition of "Waters of the United States" - Response to Comments Document
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conclusions of the Science Report. In both cases, the agencies found that the references
supported the major conclusions of the Science Report. The two citations are:
Gall, H.E., S.A. Sassman, B. Jenkinson, L.S. Lee, and C.T. Jafvert. 2015.
"Comparison of export dynamics of nutrients and animal-borne estrogens from a
tile-drained Midwestern agroecosystem." Water Research 72: 162-173.
Rau, G.C., L.J.S. Halloran, M.O. Cuthbert, M.S. Andersen, R.I. Acworth, and J.H.
Tellam. 2017. "Characterising the dynamics of surface water-groundwater
interactions in intermittent and ephemeral streams using streambed thermal
signatures." Advances in Water Resources 107: 354-369.
https://www.sciencedirect.com/science/article/pii/S0309170817300891.
Information about the agencies' review of additional literature published since 2014 is
contained in Section I.C.vi and Appendix C of the Technical Support Document.
Table 1: References published since 2014provided by commenters that were already cited in the
Proposed Rule TSD Appendix CI
Table 1 Citations
Ameli, A.A., and I.F. Creed. 2017. "Quantifying hydrologic connectivity of wetlands to
surface water systems." Hydrol. Earth Syst. Sci. 21: 1791-1808.
Calhoun, A. J.K., D.M. Mushet, K.P. Bell, D. Boix, J.A. Fitzsimons, and F. Isselin-Nondedeu.
2017. "Temporary wetlands: challenges and solutions to conserving a 'disappearing'
ecosystem." Biological Conservation 211: 3-11.
Calhoun, A.J.K., D.M. Mushet, L.C. Alexander, E.S. DeKeyser, L. Fowler, C.R. Lane, M.W.
Lang, M.C. Rains, S.C. Richter, and S.C. Walls. 2017. "The Significant Surface-Water
Connectivity of 'Geographically Isolated Wetlands.'" Wetlands 37(4): 801-806.
Callahan, M.K., D.F. Whigham, M.C. Rains, K.C. Rains, R.S. King, C.M. Walker, J.R.
Maurer, and S.J. Baird. 2017. "Nitrogen Subsidies from Hillslope Alder Stands to Streamside
Wetlands and Headwater Streams, Kenai Peninsula, Alaska." Journal of the American Water
Resources Association 53(2): 478-492.
Cheng, F.Y., and N.B. Basu. 2017. "Biogeochemical hotspots: Role of small water bodies in
landscape nutrient processing." Water Resources Research 53(6): 5038-5056.
Cohen, M.J., I.F. Creed, L. Alexander, N.B. Basu, A.J.K. Calhoun, C. Craft, E. D'Amico, E.
Dekeyser, L. Fowler, H.E. Golden, J.W. Jawitz, P. Kalla, L.K. Kirkman, C.R. Lane, M. Lang,
S.G. Leibowitz, D.B. Lewis, J. Marton, D.L. McLaughlin, D.M. Mushet, H. Raanan-
Kiperwas, M.C. Rains, L. Smith, and S.C. Walls. 2016. "Do geographically isolated wetlands
influence landscape functions?" Proceedings of the National Academy of Sciences of the
United States of America 113(8): 1978-1986.
Colvin, S.A.R., S.M.P. Sullivan, P.D. Shirey, R.W. Colvin, K.O. Winemiller, R.M. Hughes,
K.D. Fausch, D.M. Infante, J.D. Olden, K.R. Bestgen, R.J. Danehy, and L. Eby. 2019.
"Headwater Streams and Wetlands are Critical for Sustaining Fish, Fisheries, and Ecosystem
Services." Fisheries 44(2): 73-91.
Revised Definition of "Waters of the United States" - Response to Comments Document
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Table 1 Citations
Craft, C., J. Vymazal, and L. Kropfelova. 2018. "Carbon sequestration and nutrient
accumulation in floodplain and depressional wetlands." Ecological Engineering 114: 137-
145.
Creed, I.F., C.R. Lane, J.N. Serran, L.C. Alexander, N.B. Basu, A.J.K. Calhoun, J.R.
Christensen, M.J. Cohen, C. Craft, E. D'Amico, E. DeKeyser, L. Fowler, H.E. Golden, J.W.
Jawitz, P. Kalla, L.K. Kirkman, M. Lang, S.G. Leibowitz, D.B. Lewis, J. Marton, D.L.
McLaughlin, H. Raanan-Kiperwas, M.C. Rains, K.C. Rains, and L. Smith. 2017. "Enhancing
protection for vulnerable waters." Nature Geosciences 10 (11): 809-815.
https://www.ncbi.nlm.nih.gov/pubmed/30079098.
Datry, T., A.J. Boulton, N. Bonada, K. Fritz, C. Leigh, E. Sauquet, K. Tockner, B. Hugueny,
and C.N. Dahm. 2018. "Flow intermittence and ecosystem services in rivers of the
Anthropocene " Journal of Applied Ecology 55(1): 353-364.
Datry, T., K. Fritz, and C. Leigh. 2016. "Challenges, developments and perspectives in
intermittent river ecology." Freshwater Biology 61(8): 1171-1180.
Evenson, G.R., H.E. Golden, C.R. Lane, andE. D'Amico. 2015. "Geographically isolated
wetlands and watershed hydrology: A modified model analysis." Journal of Hydrology 529:
240-256.
Fritz, K.M., et al. 2018. "Physical and Chemical Connectivity of Streams and Riparian
Wetlands to Downstream Waters: A Synthesis." Journal of the American Water Resources
Association 54: 323-345.
Golden, H.E., H.A. Sander, C.R. Lane, C. Zhao, K. Price, E. D'Amico, and J.R. Christensen.
2016. "Relative effects of geographically isolated wetlands on streamflow: a watershed-scale
analysis." Ecohydrology 9(1): 21-38.
Golden, H.E., I.F. Creed, G. Ali, N.B. Basu, B.P. Neff, M.C. Rains, D.L. McLaughlin, L.C.
Alexander, A.A. Ameli, J.R. Christensen, G.R. Evenson, C.N. Jones, C.R. Lane, and M.G.
Lang. 2017. "Integrating geographically isolated wetlands into land management decisions."
Frontiers in Ecology and the Environment 15(6): 319-327.
Goodrich, D.C., W.G. Kepner, and L.R. Levick. 2018. "Southwestern intermittent and
ephemeral stream connectivity." Journal of the American Water Resources Association 54(2):
400-422.
Harvey, J., et al. 2019. "How Hydrologic Connectivity Regulates Water Quality in River
Corridors." Journal of the American Water Resources Association 55(2): 369-381.
Hosen, J.D., A.W. Armstrong, andM.A. Palmer. 2018. "Dissolved organic matter variations
in coastal plain wetland watersheds: The integrated role of hydrological connectivity, land
use, and seasonality." Hydrological Processes 32(11): 1664-1681.
Lane, C.R., and B.C. Autrey. 2017. "Sediment accretion and accumulation of P, N and
organic C in depressional wetlands of three ecoregions of the United States." Marine &
Freshwater Research. 68(12): 2253-2265. https://www.ncbi.nlm.nih.gov/pubmed/30505203.
Revised Definition of "Waters of the United States" - Response to Comments Document
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Table 1 Citations
Lane, C.R., and E. D'Amico. 2016. "Identification of Putative Geographically Isolated
Wetlands of the Conterminous United States." Journal of the American Water Resources
Association 52: 705-722.
Lane, C.R., S.G. Leibowitz, B.C. Autrey, S.D. LeDuc, and L.C. Alexander. 2018.
"Hydrological, Physical, and Chemical Functions and Connectivity of Non-Floodplain
Wetlands to Downstream Waters: A Review." Journal of the American Water Resources
Association 54(2): 346-371.
Leibowitz, S. G., Mushet, D. M., & Newton, W. E. (2016). "Intermittent surface water
connectivity: fill and spill vs. fill and merge dynamics." Wetlands 36(2), 323-342.
Leibowitz, S.G., P.J. Wigington, K.A. Schofield, L.C. Alexander, M.K. Vanderhoof, and H.E.
Golden. 2018. "Connectivity of Streams and Wetlands to Downstream Waters: An Integrated
Systems Framework. "Journal of the American Water Resources Association 54(2): 298-322.
Leigh, C., A.J. Boulton, J.L. Courtwright, K.M. Fritz, C.L. May, R.H. Walker, and T. Datry.
2016. "Ecological research and management of intermittent rivers: an historical review and
future directions." Freshwater Biology 61(8): 1181-1199.
Marton, J.M., I.F. Creed, D.B. Lewis, C.R. Lane, N.B. Basu, M.J. Cohen, and C.B. Craft.
2015. "Geographically Isolated Wetlands are Important Biogeochemical Reactors on the
Landscape." Bioscience 65(4): 408-418.
Mihelcic, J.R., and M. Rains. 2020. "Where's the Science? Recent Changes to Clean Water
Act Threaten Wetlands and Thousands of Miles of Our Nation's Rivers and Streams."
Environmental Engineering Science 37(3): 173-177.
Miller, J.O., T.F. Ducey, P.W. Brigman, C.O. Ogg, and P.G. Hunt. 2017. "Greenhouse Gas
Emissions and Denitrification within Depressional Wetlands of the Southeastern US Coastal
Plain in an Agricultural Landscape." Wetlands 37(1): 33-43.
Mushet, D.M., A.J.K. Calhoun, L.C. Alexander, M.J. Cohen, E.S. DeKeyser, L. Fowler, C.R.
Lane, M.W. Lang, M.C. Rains, and S.C. Walls. 2015. "Geographically isolated wetlands:
rethinking a misnomer." Wetlands 35: 423-431.
Neff, B.P., D.O. Rosenberry, S.G. Leibowitz, D.M. Mushet, H.E. Golden, M.C. Rains, J.R.
Brooks, and C.R. Lane. 2020. "A Hydrologic Landscapes Perspective on Groundwater
Connectivity of Depressional Wetlands." Water 12(1).
Perkin, J.S., K.B. Gido, J.A. Falke, K.D. Fausch, H. Crockett, E.R. Johnson, and J. Sanderson.
2017. "Groundwater declines are linked to changes in Great Plains stream fish assemblages."
Proceedings of the National Academy of Sciences 114(28).
Revised Definition of "Waters of the United States" - Response to Comments Document
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Table 1 Citations
Rains, M.C., S.G. Leibowitz, M.J. Cohen, I.F. Creed, H.E. Golden, J.W. Jawitz, P. Kalla,
C.R. Lane, M.W. Lang, and D.L. McLaughlin. 2016. "Geographically isolated wetlands are
part of the hydrological landscape." Hydrological Processes 30(1): 153-160.
Schofield, K.A., L.C. Alexander, C.E. Ridley, M.K. Vanderhoof, K.M. Fritz, B.C. Autrey,
J.E. DeMeester, W.G. Kepner, C.R. Lane, S.G. Leibowitz, and A.I. Pollard. 2018. "Biota
Connect Aquatic Habitats throughout Freshwater Ecosystem Mosaics." Journal of the
American Water Resources Association 54(2): 372-399.
Serran, J.N., and I.F. Creed. 2016. "New mapping techniques to estimate the preferential loss
of small wetlands on prairie landscapes." Hydrological Processes 30(3): 396-409.
Steen, V., S.K. Skagen, and B.R. Noon. 2018. "Preparing for an uncertain future: migrating
shorebird response to past climatic fluctuations in the Prairie Potholes." Ecosphere 9(2).
Sullivan, S.M.P., M.C. Rains, and A.D. Rodewald. 2019. "Opinion: The proposed change to
the definition of "waters of the United States" flouts sound science." Proceedings of the
National Academy of Sciences 116(24).
Thorslund, J., M.J. Cohen, J.W. Jawitz, G. Destouni, I.F. Creed, M.C. Rains, P. Badiou, and J.
Jarsjo. 2018. "Solute evidence for hydrological connectivity of geographically isolated
wetlands." Land Degradation & Development 29(11): 3954-3962.
Walker, C.M., D.F. Whigham, I.S. Bentz, J.M. Argueta, R.S. King, M.C. Rains, C.A.
Simenstad, C. Guo, S.J. Baird, and C.J. Field. 2021. "Linking landscape attributes to salmon
and decision-making in the southern Kenai Lowlands, Alaska, USA." Ecology and Society
26(1).
Watson, K.B., T. Ricketts, G. Galford, S. Polasky, and J. O'Niel-Dunne. 2016. "Quantifying
flood mitigation services: The economic value of Otter Creek wetlands and floodplains to
Middlebury, VT " Ecological Economics 130: 16-24.
Welter, J.R., and S.G. Fisher. 2016. "The influence of storm characteristics on hydrological
connectivity in intermittent channel networks: implications for nitrogen transport and
denitrification." Freshwater Biology 61(8): 1214-1227.
Wohl, E. 2017. "The significance of small streams." Frontiers of Earth Science 11(3): 447-
456.
Wu, Q., and C.R. Lane. 2016. "Delineation and Quantification of Wetland Depressions in the
Prairie Pothole Region of North Dakota." Wetlands 36(2): 215-227.
Yarra, A.N., and D.D. Magoulick. 2018. "Stream permanence is related to crayfish occupancy
and abundance in the Ozark Highlands, USA." Freshwater Science 37(1): 54-63.
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Table 1 Citations
Yu, X., J. Hawley-Howard, A.L. Pitt, J.J. Wang, R.F. Baldwin, and A.T. Chow. 2015. "Water
quality of small seasonal wetlands in the Piedmont ecoregion, South Carolina, USA: Effects
of land use and hydrological connectivity." Water Research 73: 98-108.
Zhu, J., G. Sun, W.H. Li, Y. Zhang, G.F. Miao, A. Noormets, S.G. McNulty, J.S. King, M.
Kumar, and X. Wang. 2017. "Modeling the potential impacts of climate change on the water
table level of selected forested wetlands in the southeastern United States." Hydrology and
Earth System Sciences 21(12): 6289-6305.
Table 2: List of the 14 citations provided by commenters that the agencies found did not meet the
criteria for review7
Table 2 Citations
Notes
Beck, M., Mazor, R. D., Stein, E. D., Maas, R., De Mello, D., & Bram, D. 2017.
Mapping of non-perennial and ephemeral streams in the Santa Ana Region.
California Coastal Water Research Project.
Cannot
discern if
peer-
reviewed
Cooper, D., Shaw, J., Wohl, E., Harry, D., Sutfin, N., Kampf, S., & Faulconer, J.
2015. Watershed to Local Scale Characteristics and Function of Intermittent and
Ephemeral Streams on Military Lands. Colorado State University Fort Collins
United States.
Not peer-
reviewed
Emerton, L. 2016. Economic valuation of wetlands: total economic value. The
wetland book, 1-6.
Cannot
discern if
peer-
reviewed;
book
chapter;
Not
relevant
(Economic
study)
Guinessey, Elizabeth, et al. 2019. A Literature Review: The Chemical, Physical
and Biological Significance of Geographically Isolated Wetlands and Non-
Perennial Streams in the Southeast. Accessed at
https://www.southernenvironment.org/wp-
content/uploads/legacy/words docs/Exhibit A.pdf.
Cannot
discern if
peer-
reviewed
7 For purposes of Table 2, "not relevant" means that the agencies reviewed the papers for their relevance to
questions related to the connectivity and/or effects of (a) ephemeral, intermittent, and perennial streams, (b)
floodplain wetlands and open waters, or (c) non-floodplain wetlands and open waters and found that the citation was
not relevant to such questions and thus was not relevant to the conclusions of the Science Report.
Revised Definition of "Waters of the United States" - Response to Comments Document
Section 16: Technical Support Document (TSD) and Other Science
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Table 2 Citations
Notes
Meyer, R., and A. Robertson. 2019. Clean Water Rule spatial analysis: A GIS-
based scenario model for comparative analysis of the potential spatial extent of
jurisdictional andnon-jurisdictional wetlands. Saint Mary's University of
Minnesota, Winona, Minnesota.
Not peer-
reviewed
Monfils, M. J., Corace III, R. G., Forbes, A., River, U. M., & Venture, G. L. R. J.
2018. Marsh bird response to hydrologic alteration and restoration of wetlands
in the boreal hardwood transition. Michigan Natural Features Inventory,
Lansing, USA.
Cannot
discern if
peer-
reviewed
Narayan, S., Beck, M. W., & Wilson, P. 2016. Coastal Wetlands and Flood
Damage Reduction: Using Risk Industry-based Models to Assess Natural
Defenses in the Northeastern USA. doi: 10.7291.
Cannot
discern if
peer-
reviewed
Olden, J., & Lytle, D. 2015. Hydroecology of Intermittent and Ephemeral
Streams: Will Landscape Connectivity Sustain Aquatic Organisms in a Changing
Climate? SERDP Project RC-1724. University of Washington, Seattle,
Washington.
Not peer-
reviewed
Phelan, J., Jones, P., & Mathews, K. 2015. Montana prairie wetlands and
intermittent/ephemeral streams: hydrologic needs assessment for healthy
watersheds. Report prepared for the U.S. Environmental Protection Agency,
Healthy Watersheds Program by RTI International, Research Triangle Park,
North Carolina.
Not peer-
reviewed
Schwarz, M. S., Davis, D. R., & Kerby, J. L. 2018. An evaluation of agricultural
tile drainage exposure and effects to wetland species and habitat within Madison
Wetland Management District, South Dakota. U.S. Fish and Wildlife Service
contaminants report 6N61, Pierre, South Dakota.
Not peer-
reviewed
Stromberg, J. C., Gallo, E. L., Lohse, K. A., Meixner, T., Moody, E. K., Sabo, J.
L., & Setaro, D. L. 2015. Structure andfunction of ephemeral streams in the arid
and semiarid southwest: implications for conservation and management. Arizona
State University, Tempe, Arizona.
Not peer-
reviewed
U.S. Environmental Protection Agency. "The National Rivers and Streams
Assessment 2008/2009." https://www.epa.gov/sites/default/files/2016-
03/documents/fact_sheet_draft_variation_march_2016_revision.pdf
No
publication
date; Not
peer-
reviewed;
Not
relevant
U.S. Environmental Protection Agency. "Stream Flows." Report on the
Environment. https://cfpub.epa.gov/roe/indicator.cfm?i=29; can also navigate to
this document through Docket ID No. EPA-HQ-OW-2021-0602-0329
No
publication
date; Not
peer-
reviewed;
Not
relevant
Revised Definition of "Waters of the United States" - Response to Comments Document
Section 16: Technical Support Document (TSD) and Other Science
21
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Table 2 Citations
Notes
U.S. Department of the Agriculture. 2017. "Role of Prior Converted Croplands
on Nitrate Processing in Mid-Atlantic Agricultural Landscapes."
httDs://directives.sc.egov.usda.gov/ODenNonWebContent.asDx?content=41460.w
Cannot
discern if
peer
reviewed
ba
Wu, Q. 2018. "GIS and remote sensing applications in wetland mapping and
monitoring." Pages 140-157 in Comprehensive Geographic Information Systems,
Vol. 2. B. Huang, ed. Elsevier, Oxford, UK. DOI: 10.1016/B978-0-12-409548-
9.10460-9.
Book
chapter;
Cannot
discern if
peer
reviewed.
Not
relevant
(focus on
mapping,
not
effects)
Table 3: Citations provided during the comment period that were determined not to be relevant to the
Science Report8
Table 3 Citations
Notes (Including
Relevance to the
Conclusions of the
Science Report)
Barbier, E. B. 2015. "Valuing the storm protection service of estuarine and
coastal ecosystems " Ecosystem Services 11: 32-38.
Addresses estuarine
systems and
valuation methods.
Not relevant to
connectivity and/or
effects.
BenDor, T., Lester, T. W., Livengood, A., Davis, A., & Yonavjak, L.
2015. "Estimating the size and impact of the ecological restoration
economy." PloS one 10(6): e0128339.
Economic study.
Not relevant to
connectivity and/or
effects.
8 For purposes of Table 3, "not relevant to connectivity and/or effects" means that the agencies reviewed the papers
for their relevance to questions related to the connectivity and/or effects of (a) ephemeral, intermittent, and perennial
streams, (b) floodplain wetlands and open waters, or (c) non-floodplain wetlands and open waters and found that the
citation was not relevant to such questions and thus was not relevant to the conclusions of the Science Report. The
relevant typology column denotes if the citation was found to be of a relevant system typology. Citations that were
cited in other sections of the Proposed Rule TSD but that were not cited in Appendix CI of that document are
denoted with **.
Revised Definition of "Waters of the United States" - Response to Comments Document
Section 16: Technical Support Document (TSD) and Other Science
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Table 3 Citations
Notes (Including
Relevance to the
Conclusions of the
Science Report)
Bergstrom, J. C., & Loomis, J. B. 2017. "Economic valuation of river
restoration: An analysis of the valuation literature and its uses in decision-
making." Water Resources and Economics 17: 9-19.
Economic study on
river restoration
valuation. Not
relevant to
connectivity and/or
effects.
Bratt, A. R., Finlay, J. C., Hobbie, S. E., Janke, B. D., Worm, A. C., &
Kemmitt, K. L. 2017). "Contribution of leaf litter to nutrient export during
winter months in an urban residential watershed." Environmental Science
& Technology 51(6): 3138-3147.
Nitrogen and
phosphorus in
urban watersheds.
Not relevant to
connectivity and/or
effects.
Demaria, E. M., Palmer, R. N., & Roundy, J. K. 2016. "Regional climate
change projections of streamflow characteristics in the Northeast and
Midwest US." Journal of Hydrology: Regional Studies 5: 309-323.
Streamflow in
Northeast and
Midwest USA. Not
specific to stream
connectivity and/or
effects. Not
relevant to
connectivity and/or
effects.
Dhungel, S., Tarboton, D. G., Jin, J., & Hawkins, C. P. 2016. "Potential
effects of climate change on ecologically relevant streamflow regimes."
River Research and Applications 32(9): 1827-1840.
Climate change.
Not relevant to
connectivity and/or
effects.
Flower, H., Rains, M., & Fitz, C. 2017. "Visioning the Future: Scenarios
Modeling of the Florida Coastal Everglades." Environmental Management
60(5): 989-1009.
Resource typology
(estuarine
wetlands) is not
applicable.
Flower, H., etal. 2019. "Shifting ground: landscape-scale modeling of
biogeochemical processes under climate change in the Florida
Everglades." Environmental Management 64(4): 416-435.
Climate change.
Not relevant to
connectivity and/or
effects.
Flower, H., Rains, M., Lewis, D., & Zhang, J. Z. 2017. "Rapid and intense
phosphate desorption kinetics when saltwater intrudes into carbonate
rock." Estuaries and Coasts 40(5): 1301-1313.
Geological study of
desorption kinetics
in rocks. Not
relevant to
connectivity and/or
effects.
Revised Definition of "Waters of the United States" - Response to Comments Document
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Table 3 Citations
Notes (Including
Relevance to the
Conclusions of the
Science Report)
Flower, H., Rains, M., Lewis, D., Zhang, J. Z., & Price, R. 2016. "Control
of phosphorus concentration through adsorption and desorption in shallow
groundwater of subtropical carbonate estuary." Estuarine, Coastal and
Shelf Science 169: 238-247.
Mangrove ecotone
of the Everglades.
Resource typology
(estuarine
wetlands) is not
applicable.
Flower, H., Rains, M., Lewis, D., Zhang, J. Z., & Price, R. 2017.
"Saltwater intrusion as potential driver of phosphorus release from
limestone bedrock in a coastal aquifer." Estuarine, Coastal and Shelf
Science 184: 166-176.
Effects of salt
intrusion on soluble
reactive
phosphorus
bedrock. Not
relevant to
connectivity and/or
effects.
Gosejohan, M. C., Weisberg, P. J., & Merriam, K. E. 2017. "Hydrologic
influences on plant community structure in vernal pools of northeastern
California." Wetlands 37(2): 257-268.
Not relevant to
connectivity and/or
effects.
Hiatt, D. L., el a/. 2017. "Catchment-scale alder cover controls nitrogen
fixation in boreal headwater streams." Freshwater Science 36(3): 523-532.
Not relevant to
connectivity and/or
effects.
Interis, M. G., & Petrolia, D. R. 2016. "Location, location, habitat: how the
value of ecosystem services varies across location and by habitat." Land
Economics 92(2): 292-307.
Economics of
ecosystem services
in oyster reef, salt
marsh, and black
mangrove. Not
relevant to
connectivity and/or
effects.
Jenkins, C. N., Van Houtan, K. S., Pimm, S. L., & Sexton, J. O. 2015. "US
protected lands mismatch biodiversity priorities." Proceedings of the
National Academy of Sciences 112(16): 5081-5086.
Maps of
biodiversity -
vertebrates, fish,
and trees and how
they crosswalk with
locations of
protected lands.
Not relevant to
connectivity and/or
effects.
Revised Definition of "Waters of the United States" - Response to Comments Document
Section 16: Technical Support Document (TSD) and Other Science
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Table 3 Citations
Notes (Including
Relevance to the
Conclusions of the
Science Report)
Kaushal, S. S., McDowell, W. H., Wollheim, W. M., Newcomer Johnson,
T. A., Mayer, P. M., Belt, K. T., & Pennino, M. J. 2015. "Urban evolution:
The role of water." Water 7(8): 4063-4087.
Review/concept
paper describing
urban evolution.
Not relevant to
connectivity and/or
effects.
Keiser, D. A., et al. 2021. "A water rule that turns a blind eye to
transboundary pollution." Science 372(6539): 241-243.
Policy piece. Not
relevant to
connectivity and/or
effects.
Keith, D. A., Ferrer-Paris, J. R., Nicholson, E., & Kingsford, R. T. 2020.
The IUCN Global Ecosystem Typology 2.0: Descriptive profiles for biomes
and ecosystem functional groups. IUCN, Gland, Switzerland.
Encyclopedic entry
describing
typologies of
systems. Not
relevant to
connectivity and/or
effects.
Kleindl, W. J., Rains, M. C., Marshall, L. A., & Hauer, F. R. 2015. "Fire
and flood expand the floodplain shifting habitat mosaic concept."
Freshwater Science 34(4): 1366-1382.
Fire and landscape
variables affect
floodplain patch
dynamics. Not
relevant to
connectivity and/or
effects.
Lalika, M. C., Meire, P., Ngaga, Y. M., & Sanga, G. J. 2017. "Willingness
to pay for watershed conservation: are we applying the right paradigm?"
Ecohydrology & Hydrobiology 17(1): 33-45.
Economic
valuation and
willingness to pay.
Not relevant to
connectivity and/or
effects.
Levick, L., Hammer, S., Lyon, R., Murray, J., Birtwistle, A., Guertin, P.,
Goodrich, D., Bledsoe, B., & Laituri, M. 2018. "An ecohydrological
stream type classification of intermittent and ephemeral streams in the
southwestern United States ''Journal of Arid Environments 155: 16-35.
Methodological
paper for stream
classification
methods. Not
relevant
connectivity and/or
effects
Mitsch, W. J., Bernal, B., & Hernandez, M. E. 2015. "Ecosystem services
of wetlands." International Journal of Biodiversity Science, Ecosystem
Services & Management 11(1): 1-4.
Introduction to a
special issue. Not
relevant to
connectivity and/or
effects.
Revised Definition of "Waters of the United States" - Response to Comments Document
Section 16: Technical Support Document (TSD) and Other Science
25
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Table 3 Citations
Notes (Including
Relevance to the
Conclusions of the
Science Report)
Mittermeier, R. A., van Dijk, P. P., Rhodin, A. G., & Nash, S. D. 2015.
"Turtle hotspots: an analysis of the occurrence of tortoises and freshwater
turtles in biodiversity hotspots, high-biodiversity wilderness areas, and
turtle priority areas." Chelonian Conservation and Biology 14(1): 2-10.
Regional turtle
biodiversity
hotspots at global
scales. Not relevant
to connectivity
and/or effects.
Mushet, D. M. 2016. "Midcontinent prairie-pothole wetlands and climate
change: an introduction to the supplemental issue." Wetlands 36(2): 223-
228.
Introduction to a
special section. Not
relevant to
connectivity and/or
effects.
Pericak, A. A., Thomas, C. J., Kroodsma, D. A., Wasson, M. F., Ross, M.
R., Clinton, N. E., Campagna, D. J., Franklin, Y., Bernhardt, E. S., &
Amos, J. F. 2018. "Mapping the yearly extent of surface coal mining in
Central Appalachia using Landsat and Google Earth Engine." PloS one
13(7): e0197758.
Mapping annual
surface coal mining
operations in
southern
Appalachia. Not
relevant to
connectivity and/or
effects.
Poudel, J., Henderson, J. E., & Munn, I. A. 2016. "Economic contribution
of hunting expenditure to the southern United States of America."
International Journal of Environmental Studies 73(2): 236-254.
Economic impacts
of hunting in the
Southeast. Not
relevant to
connectivity and/or
effects.
Powell, K. M., Wynn, J. G., Rains, M. C., Stewart, M. T., & Emery, S.
2019. "Soil indicators of hydrologic health and resilience in cypress domes
of West-Central Florida." Ecological Indicators 97: 269-279.
Investigates soil
health of wetlands.
Not relevant to
connectivity and/or
effects.
Soria, M., Leigh, C., Datry, T., Bini, L. M., & Bonada, N. 2017.
"Biodiversity in perennial and intermittent rivers: A meta-analysis." Oikos
126(8): 1078-1089.
Focus on
biodiversity. Not
relevant to
connectivity and/or
effects.
**Stanislawski, L. V., Survila, K., Wendel, J., Liu, Y., & Buttenfield, B. P.
2018. "An open source high-performance solution to extract surface water
drainage networks from diverse terrain conditions." Cartography and
Geographic Information Science 45(4): 319-328.
Methodological
paper on mapping
stream networks.
Not relevant to
connectivity and/or
effects.
Revised Definition of "Waters of the United States" - Response to Comments Document
Section 16: Technical Support Document (TSD) and Other Science
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Table 3 Citations
Notes (Including
Relevance to the
Conclusions of the
Science Report)
Stubbington, R., etal. 2019. "A comparison of biotic groups as dry-phase
indicators of ecological quality in intermittent rivers and ephemeral
streams." Ecological Indicators 97: 165-174.
Efficacy of biota
assemblages for
indicating
headwater and
ephemeral streams
ecosystem health.
Not relevant to
connectivity and/or
effects.
**U.S. Global Change Research Program. 2018. Impacts, Risks, and
Adaptation in the United States: Fourth National Climate Assessment,
Volume II. [Reidmiller, D.R., C.W. Avery, D.R. Easterling, K.E. Kunkel,
K.L.M. Lewis, T.K. Maycock, and B.C. Stewart (eds.)]. U.S. Global
Change Research Program, Washington, DC, USA, 1515 pp. doi:
10.7930/NCA4.2018. Accessed at
httDs://nca2018.globalchange.gov/downloads/NCA4 2018 FullReDort.Ddf.
Report on climate
change. Not
relevant to
connectivity and/or
effects.
van der Valk, A., & Mushet, D. M. 2016. "Interannual water-level
fluctuations and the vegetation of prairie potholes: potential impacts of
climate change." Wetlands 36(2): 397-406.
Effects of climate
change on prairie
pothole wetlands;
Not relevant to
connectivity and/or
effects.
Woelfle-Erskine, C., Larsen, L. G., & Carlson, S. M. 2017. "Abiotic
habitat thresholds for salmonid over-summer survival in intermittent
streams." Ecosphere 8(2): e01645.
Focus was on in-
stream effects. Not
relevant to
connectivity and/or
effects
(downstream).
Zipper, S. C., Hammond, J. C., Shanafield, M., Zimmer, M., Datry, T.,
Jones, C. N., Kaiser, K. E., Godsey, S. E., Burrows, Ryan M., Blaszczak, J.
R., Busch, M. H., Price, A. N., Boersma, K. S., Ward, A. S., Costigan, K.,
Allen, G. H., Krabbenhoft, C. A., Dodds, W. K., Mims, M. C., Olden, J.
D., Kampf, S. K., Burgin, A. J., & Allen, D. C. 2021. "Pervasive changes
in stream intermittency across the United States." Environmental Research
Letters 16(8): 084033.
Not relevant to
connectivity and/or
effects.
Revised Definition of "Waters of the United States" - Response to Comments Document
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16.3 Climate Change
16.3.1 Effects of Climate Change in Specific Regions and Specific Aquatic Resource Types
Several commenters discussed how climate change has already impacted specific areas of the United
States.
Several commenters stated that flow regimes in the arid Southwest have already been altered due
to climate change and that it is unlikely that flows of many ephemeral drainages will reach a
traditional navigable water or downstream "permanent" waters in the future with the drying
climate in the arid Southwest. They claimed that the proposed rule does not appear to have
addressed this. One of these commenters stated, "Any final rule should clarify that drier
conditions in the arid west, or rarer but more extreme weather events, should not be used as a
justification to expand jurisdiction further."
Another commenter stated that with changing climate patterns and more severe storm and
drought events, resiliency is a priority for the state of North Carolina.
One commenter stated that due to climate change, surface water drying will reduce groundwater
recharge and thereby impact the future of drinking water supplies in Santa Fe County, New
Mexico.
One commenter stated that climate change and urbanization impacts are greatly increasing the
flows and flashiness of the Cahaba River (Alabama) and its tributaries.
One commenter discussed the importance of broad federal jurisdiction over streams and wetlands
in the City and State of New York. They stressed that these aquatic resources play a large role in
maintaining New York City's current level of resiliency to climate change and these aquatic
resources are vulnerable to being lost due to development.
Several commenters discussed the effects of climate change, including extreme weather events, on
aquatic resources, with some commenting on the need to protect such resources in light of climate change.
One commenter stated that in the face of increasing effects from climate change, more and more
streams are going dry part of the year, wetlands are drying, and pollutant loads to waters are
increasing.
A few commenters mentioned that the kinds of wetlands that have lost protections under prior
rules are also at increased risk from climate change.
One commenter stated that the effects of climate change will impact already biologically
impaired rivers and streams unless there is greater protection.
One commenter stated that waters with less than perennial flow are becoming more and more
common and should be protected.
One commenter stated that the rulemaking must consider climate change because ecosystem
services provided by small streams, non-floodplain wetlands, ditches, and other waterbodies are
essential for climate resilience, as well as the combined effects of climate change and
urbanization on increased flows and flashiness in river systems.
Another commenter argued that strong clean water protections are necessary to mitigate and
adapt to the effects of a changing climate. They added that climate change is already causing
widespread and varied harm to the nation's water resources.
One commenter stated that with predicted more frequent extreme weather, increased flows and
flashes, and loss of stormwater runoff control and delivery, greater protections will be needed for
carbon storage, groundwater filtration, drought resilience, and aquatic habitat resources.
Revised Definition of "Waters of the United States" - Response to Comments Document
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Another commenter stated that it is critical to preserve wetlands because they serve as buffers
against flooding and storm surges, as well as protecting seasonal streams which may often be dry
but are needed for extreme weather events.
Another commenter stated that the agencies should consider the adverse side effects that would
be caused by removing protections for any waters at a time when climate change is already
causing adverse impacts. The commenter further stated that fewer waters will be subject to the
Clean Water Act due to climate change causing perennial streams to become intermittent, and
intermittent streams to become ephemeral. They urged the agencies to thoroughly consider the
effects of climate change in the final rule.
One commenter stated that intact, healthy wetlands and headwater streams absorb precipitation
and floodwaters, reduce the risk and severity of flooding, protect lives and livelihoods, and
promote the goals behind the Clean Water Act, as well as the current administration's
overarching climate resilience goals.
Agencies' Response: The agencies considered comments on the proposed rule discussing
climate change. The agencies recognize and agree that climate change will have a variety of
impacts, including on aquatic resources. The agencies also recognize the important roles
that streams, wetlands, and other aquatic resources can play in climate change mitigation
and adaptation. See Section II.C of the Technical Support Document. The agencies disagree
with the commenter who stated that the agencies are using climate change to expand
jurisdiction. When the agencies assess whether or not a water is a "water of the United
States," consistent with longstanding practice, they do not assess future conditions based on
potential climatic changes.
The agencies recognize that commenters had varying views on how climate change should
or should not be considered in determining which waters should be federally protected as
"waters of the United States." There are ways the agencies can consider a changing climate
under the significant nexus standard, but only to the extent it is relevant to the evaluation of
whether the subject waters significantly affect the chemical, physical, or biological integrity
of paragraph (a)(1) waters. See Final Rule Preamble Section IV.C.9.c.ii for further
discussion of how the agencies can consider a changing climate under the significant nexus
standard consistent with the best available science.
16.3.2 Comments on the Use of Climate Change Science in Developing Policy
Several commenters submitted general comments on climate change.
One commenter asserted that a final rule should not unduly burden efforts to reduce the
greenhouse gas emissions that cause climate change, including construction of solar energy
facilities.
One commenter recommended additional guidance and streamlined permitting for projects
located in jurisdictional waters which are proposed to mitigate climate change by building
resiliency.
One commenter stated they recognize that the burdens of environmental pollution fall
disproportionately on minority, low-income, and indigenous populations and that climate change
will exacerbate these existing environmental risks and associated health risks.
Revised Definition of "Waters of the United States" - Response to Comments Document
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One commenter stated they appreciate that the agencies acknowledge climate change in the
proposed rule, but criticized the lack of proposed language that could have been included to
address climate change.
One commenter wrote that the preamble of the proposed rule discusses climate change but does
not address how "waters of the United States" will be impacted by a changing climate.
One commenter requested stronger protection for waterbodies that improve resilience to drought,
wildfire, and flooding.
Several commenters asserted that the agencies should use the significant amount of scientific
information and advice obtained from experts, and the scientific understanding of upstream
waters and climate change in particular, when creating the proposed rule.
One commenter suggested that the agencies consider impacts of climate change and climate
resiliency when developing a definition of "waters of the United States," and when listing
examples of how flow regime and other ecosystem services related to significant nexus
determinations.
One commenter stated that climate-induced change in watershed hydrology increases society's
reliance on the ecosystem services such as flood abatement, water quality, and baseflow
maintenance. They also stated that to maintain climate resilience, as many of the nation's wetland
and water resources that can provide such services should be protected as is practicable.
Agencies' Response: The agencies recognize and agree that climate change will have a
variety of impacts, including on aquatic resources. The agencies also recognize the
important roles that streams, wetlands, and other aquatic resources can play in climate
change mitigation and adaptation. See Section II.C of the Technical Support Document.
The agencies recognize that commenters had varying views on how climate change should
or should not be considered in determining which waters should be federally protected as
"waters of the United States." There are ways the agencies can consider a changing climate
under the significant nexus standard, but only to the extent it is relevant to the evaluation of
whether the subject waters significantly affect the chemical, physical, or biological integrity
of paragraph (a)(1) waters. See Final Rule Preamble Section IV.C.9.c.ii for a discussion of
how the agencies can consider a changing climate under the significant nexus standard
consistent with the best available science.
Regarding the recommendation for additional guidance, as with any final regulation, the
agencies will consider developing new guidance to facilitate implementation of the final rule
should questions arise in the field regarding application of the final rule. Nevertheless, the
agencies conclude that the final rule, together with the preamble and existing tools, provides
sufficient clarity to allow consistent implementation of the final rule. Comments regarding
permitting are outside the scope of this rulemaking. The agencies agree with the commenter
who stated that the burdens of environmental pollution can fall disproportionately on
communities with environmental justice concerns. The agencies acknowledge that climate
change may exacerbate environmental risks and associated health risks for those
communities.
Revised Definition of "Waters of the United States" - Response to Comments Document
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16.4 Comments on the Importance of Clean Water for Humans and Wildlife
16.4.1 Comments on the Importance of Clean Water to Humans
Several commenters discussed the importance of clean water to humans and stated that aquatic resources
provide a variety of ecosystem services that benefit humans.
One commenter discussed the water cycle and how the cycle can be altered by pumping or
artificially injecting surface water into an aquifer. They questioned how this will impact
waterways and the determination of the relatively permanent standard.
One commenter requested that the agencies be mindful of the proposed rule's impact on source
waters, specifically those used for drinking water. They recommended that the agencies include
language to protect these vital resources.
One commenter stated that ephemeral and headwater streams and wetlands not directly connected
to streams and rivers are part of the critical natural structure that supplies clean drinking water,
and that such aquatic resources should be protected.
Several commenters emphasized that clean water is necessary to support tribal lifeways. They
stated that a tribe's cultural, spiritual, and subsistence practices require much more fish, wildlife,
and plants than the general population and that wetlands, small streams, and ephemeral waters
play a critical role in this natural environment.
One commenter discussed the need for protection of wetlands and ephemeral streams in large
waterbodies such as the Mississippi River. They further outlined the effort to reduce nutrient
pollution and how progress is hampered by the disruption of natural stream flows due to the loss
of wetlands, stream channelization, and other actions.
One commenter stated that science makes the importance of ephemeral streams and upstream
waters to overall water quality clear. They further discussed the significant nexus standard and
how it allows for the consideration of all adjacent wetlands.
One commenter stressed the importance of protecting streams and wetlands, specifically in the
Great Lakes ecoregion. They stated that it is important that stronger protections go along with
recent funding efforts for restoration. They discussed the importance of flood mitigation, carbon
sequestration, water recharge, water purification, and wildlife habitat with respect to climate
change, drought, and clean and affordable drinking water.
One commenter discussed the importance of providing protection for water supply. They
requested that the agencies be mindful of the impact that the proposed rule has on source waters
and finalize language that is protective of these resources.
One commenter stated that clean water is vital to the health of communities, businesses,
agriculture, and the natural environment, especially in the face of climate change and increased
demand from a growing population.
One commenter stated that there are many "non-traditional waters" in Missouri that are used for
drinking water, agriculture, businesses, and recreation and that have not been consistently defined
and protected as "waters of the United States" or at the state level.
One commenter requested that the agencies go further than returning to the 1986 regulations and
the "significant nexus" guidance, and argued that science demonstrating the connectivity of
wetlands to traditional navigable waters is more compelling and critical every year.
Agencies' Response: The agencies agree with commenters who noted the importance of
clean water, and that wetlands, streams, and open waters are well-known to provide a wide
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variety of functions that translate into ecosystem services that benefit humans, including
tribal customs and lifeways. However, it is also important to note that the agencies'
significant nexus standard in the final rule is carefully tailored so that only particular types
of functions provided by upstream waters can be assessed. A significant nexus analysis is
limited to an assessment of only those functions identified in the final rule that have a nexus
to the chemical, physical, or biological integrity of paragraph (a)(1) waters. Thus, there are
some important functions provided by wetlands, tributaries, and paragraph (a)(5) waters
that will not be assessed by the agencies when making jurisdictional decisions under this
rule. See also Final Rule Preamble Section IV.C.9.b.i.
The agencies disagree with the commenter who requested that the agencies go further than
returning to the 1986 regulations and the "significant nexus guidance." In this rule, the
agencies are exercising their authority to interpret "waters of the United States" to mean
the waters defined by the familiar 1986 regulations, with amendments to reflect the
agencies' determination of the statutory limits on the scope of the "waters of the United
States" informed by the text of the relevant provisions of the Clean Water Act and the
statute as a whole, the scientific record, relevant Supreme Court precedent, and the
agencies' experience and technical expertise after more than 45 years of implementing the
longstanding pre-2015 regulations defining "waters of the United States." In developing the
final rule, the agencies thoroughly considered alternatives to this rule, including the 2015
Clean Water Rule, and have concluded that this final rule best accomplishes the agencies'
goals to promulgate a rule that advances the objective of the Clean Water Act, is consistent
with Supreme Court decisions, is informed by the best available science, and promptly and
durably restores vital protections to the nation's waters. See Section IV.B.l of the Preamble
to the Final Rule for further discussion of the agencies' grounds for concluding that the
2015 Clean Water Rule is not a suitable alternative to the final rule.
16.4.2 Comments on the Importance of Clean Water to Wildlife
Several commenters discussed the importance of clean water with respect to wildlife.
One commenter stated that all subsurface waters should be regulated as part of "waters of the
United States" under the Clean Water Act. They discussed how groundwater provides a "base
flow" to rivers and streams, is an asset to bird habitat, and helps maintain fish and invertebrate
populations during dry seasons.
One commenter stated that prairie potholes and headwater streams are important habitat for trout
and ducks and these areas need protection.
One commenter stated that birds use lakes, tributaries, streams, ponds, "isolated" wetlands,
prairie potholes, and other water bodies for breeding, nesting, and raising young and these areas
should be protected.
One commenter asserted that strong protections for clean water are critical to sustain fish and
wildlife, as well as to enhance climate resilience.
One commenter stated that headwater ecosystems, wetlands, and other waters provide habitat for
many threatened species, specifically frogs and salamanders.
A few commenters emphasized that intermittent and ephemeral streams, as well as seasonal and
"isolated" wetlands, also provide critical habitat for a diverse array of species, including
endangered and threatened species.
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Several commenters specifically noted the importance of freshwater habitatsriparian wetlands
and depressional wetlands in particularand clean water to resident and migratory birds.
Agencies' Response: While the agencies recognize that clean water and associated wetland
and aquatic resource habitats are critical resources for birds and humans, the agencies also
acknowledge the Supreme Court's decision in SWANCC9 finding that the use of "isolated"
non-navigable intrastate ponds by migratory birds was not by itself a sufficient basis for the
exercise of federal authority under the Clean Water Act. In this rule, the agencies are not
protecting tributaries, adjacent wetlands, or paragraph (a)(5) waters based on their
potential use as habitat for migratory birds. Rather, this rule includes tributaries, adjacent
wetlands, and paragraph (a)(5) waters on a case-specific basis based on their importance to
the integrity of traditional navigable waters, the territorial seas, and interstate waters where
such waters meet either the relatively permanent standard or the significant nexus
standard. As such, under the final rule, consideration of biological functions does not
constitute an assertion of jurisdiction over a water based solely on its use by migratory
birds. Rather, the agencies consider biological functions for purposes of significant nexus
determinations under this rule only to the extent that the functions provided by tributaries,
adjacent wetlands, and paragraph (a)(5) waters significantly affect the biological integrity
of the traditional navigable waters, the territorial seas, or interstate waters, consistent with
the objective of the Act. For example, the final rule's definition of "significantly affect"
includes the following biological function that will be assessed as part of the significant
nexus analysis related to integrity of the paragraph (a)(1) water: the provision of habitat
and food resources for aquatic species located in waters identified in paragraph (a)(1). See
also the agencies' response to comments in Section 16.4.1 regarding the importance of clean
water to humans. See Section IV.C.7 of the Final Rule Preamble for further discussion of
the jurisdictional status of groundwater.
16.5 Additional Literature Provided to the Agencies
Commenters also asked the agencies to consider other references, though those suggestions were not
always specific to the solicitation of comment on the scientific literature contained in Appendix C of the
Proposed Rule TSD (see the agencies' response to comments in Section 16.2.2), or did not likewise
address the agencies' request for additional scientific literature and references relevant to the Science
Report's conclusions on the connectivity and effects of streams, floodplain wetlands and open waters, and
non-floodplain wetlands and open waters on the chemical, physical, and biological integrity of larger
downstream waters. Additional citations provided to the agencies included:
Audubon. 2020. "The Importance of Arizona's Ephemeral Streams. Attachment to Comments
Submitted by Save the Scenic Santa Ritas. Docket ID No. EPA-HQ-OW-2021-0602-0556.
https://www.regulations.gov/comment/EPA-HQ-OW-2021-0602-0556.
Kline, J., T. Bernthal, M. Cain, A. Gries, R. Grasshoff, L. Jack, N. Larson, N. Miller, S.
Peterson, & J. Wagner. 2021. Wetlands and Waterways in Wisconsin: Navigating Changes to the
Federal Waters of the United States (WOTUS) Rule. Opportunities Now: An Analysis of Priority
Issues and Actions for Wisconsin's Natural Resources. Wisconsin's Green Fire. Rhinelander,
WI. Docket ID No. EPA-HQ-OW-2021-0602-0553. Available at:
https://www.regulations.gov/comment/EPA-HQ-OW-2021-0602-0553.
9 Solid Waste Agency of Northern Cook County v. U.S. Army Corps of Engineers, 531 U.S. 159 (2001) ("SWANCC')
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Lefebvre, L,,et al. 2013. Survey of OHWMIndicator Distribution Patterns across Arid West
Landscapes. ERDC/CRREL TR-13-2. U.S. Army Corps of Engineers, Hanover, NH.
Levick, L. 2021. Report to Save the Scenic Santa Ritas. Attachment to Comments Submitted by
Save the Scenic Santa Ritas. Docket ID No. EPA-HQ-OW-2021-0602-0556.
https://www.regulations.gov/comment/EPA-HQ-OW-2021-0602-0556.
Tennessee Department of Environment and Conservation, Division of Water Resources. 2020.
Guidance for Making Hydrologic Determinations. Version 1.5. Available at
https://www.tn.gov/content/dam/tn/environment/water/policy-and-guidance/dwr-nr-g-03-
hydrologic-determinations%E2%80%9304012020.pdf.
U.S. Environmental Protection Agency, Department of the Army, U.S. Fish and Wildlife
Service, and National Marine Fisheries Service. 1994. Alaska Wetlands Initiative: Summary
Report. Available at: https://dec.alaska.gov/media/13267/1994-wetlands-initiative.pdf.
The following citation provided to the agencies was already cited in the Proposed Rule TSD and in the
Science Report:
Levick, L., et al. 2008. The Ecological and Hydrological Significance of Ephemeral and
Intermittent Streams in the Arid and Semi-arid American Southwest. EPA/600/R-08/134 and
ARS/233046. U.S. Environmental Protection Agency, Office of Research and Development and
U.S. Department of Agriculture/Agricultural Research Service. Southwest Watershed Research
Center, Washington, D.C. Available at https://www.epa.gov/sites/default/files/2015-
03/documents/ephemeral_streams_report_final_508-kepner.pdf.
The following citation provided to the agencies was already cited in the Proposed Rule TSD:
Lichvar, R.W., and S.M. McColley. 2008. A Field Guide to the Identification of the Ordinary
High Water Mark (OHWM) in the Arid West Region of the Western United States: A Delineation
Manual. ERDC/CRREL TR-08-12. U.S. Army Engineer Research and Development Center,
Hanover, NH.
Agencies' Response: With respect to the citations and references commenters provided for
consideration, the agencies have responded to the substantive comments received in
Sections 1-18 of the agencies' response to comments, as well as in other locations in the
administrative record for this rule. In doing so, the agencies have responded to the
commenters' reference or citation as it was used to support the commenters' statements.
The agencies have also considered references that were provided to the agencies in response
to their request for additional literature relevant to the conclusions of the Science Report
that had been published since 2014 but that was not included in the agencies' analysis in the
Proposed Rule TSD (e.g., literature that was not cited in Appendix CI of the Proposed Rule
TSD). The agencies' response to such literature is provided in Section 16.2.2.
In addition, the agencies have reviewed reports, citations, and other documents provided by
commenters and have incorporated some of these references, as relevant and appropriate,
into the final Technical Support Document for the rule. The agencies note that some of the
citations provided to them were already cited in the Proposed Rule TSD.
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