Waters of the United States (WOTUS):
February 6, 2023
Frequently Asked Questions About the Scope
Kate R. Bowers
of the Clean Water Act
Legislative Attorney

Congress established the Federal Water Pollution Control Act, also known as the Clean Water
Laura Gatz
Act (CWA), to restore and protect the quality of the nation’s surface waters. The CWA protects
Specialist in Environmental
“navigable waters,” defined in the statute as “waters of the United States, including the territorial
Policy
seas.” The CWA does not further define the term waters of the United States (WOTUS), which

determines which waters are federally regulated. Thus, in implementing the CWA, the Army
Corps of Engineers (Corps) and the Environmental Protection Agency (EPA)—the two agencies

that administer the statute—have defined the term in regulations. However, Congress’s intent as
to the meaning of WOTUS has been debated and litigated for more than four decades.
For much of the past several decades, regulations promulgated by the Corps and EPA in the 1980s have been in effect.
(These regulations, as further interpreted by the courts and agencies are often referred to as the pre-2015 rules.) The agencies
supplemented these regulations with guidance, which they developed in response to Supreme Court rulings related to the
scope of the federal government’s ability to regulate WOTUS. The Corps and EPA acknowledged that their guidance did not
provide the public or agency staff with the information needed to ensure timely, predictable, and consistent jurisdictional
determinations. Diverse stakeholders and Members of Congress requested a formal rulemaking to revise existing regulations.
Successive presidential administrations have engaged in efforts to define WOTUS in regulation. Both the Obama
Administration’s 2015 Clean Water Rule and the Trump Administration’s 2020 Navigable Waters Protection Rule prompted
strong reactions from a variety of stakeholders, with numerous groups filing lawsuits challenging the rules. On January 18,
2023, the Corps and EPA, under the Biden Administration, issued a new rule (the 2023 WOTUS Rule) redefining WOTUS in
the agencies’ regulations. The Corps and EPA have asserted that their intent in promulgating the 2023 WOTUS Rule was to
redefine WOTUS in a durable regulation, updating the pre-2015 rules to reflect consideration of Supreme Court decisions,
science, and the agencies’ experience and technical expertise. In general, the rule defines WOTUS more narrowly than the
Clean Water Rule and more broadly than the Navigable Waters Protection Rule.
While some stakeholders have expressed support for the 2023 WOTUS Rule, others believe that it defines WOTUS too
broadly, does not provide regulatory clarity, and should not have been issued prior to the resolution of a pending Supreme
Court case addressing aspects of the scope of WOTUS. The new rule is the subject of stakeholder commentary, congressional
action, and litigation.
Some stakeholders have urged Congress to take actions regarding regulation of WOTUS. In the 118th Congress, Members
have introduced a joint resolution to revoke the 2023 WOTUS Rule through the Congressional Review Act. Members may
take action to specifically define the term through amendments to the CWA, introducing legislation, for example, to narrow
the term’s scope, as was done in the 117th Congress. Committees in the 117th Congress and the 116th Congress held multiple
oversight hearings to assess the impacts of rules at that time, and the 118th Congress may conduct similar oversight.

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Waters of the United States (WOTUS): Frequently Asked Questions

ongress established the Federal Water Pollution Control Act, also known as the Clean
Water Act (CWA), to restore and protect the quality of the nation’s surface waters.1 The
C Clean Water Act protects “navigable waters,” defined in the statute as “waters of the
United States, including the territorial seas.”2 The CWA does not define “waters of the United
States” (WOTUS). The scope of the term determines which waters are federally regulated, and
thus which waters are subject to CWA requirements and programs. These include CWA
permitting requirements; water quality certifications; water quality standards, impaired waters,
and total maximum daily loads; and other CWA and non-CWA programs.
Successive administrations have struggled to interpret the term waters of the United States for the
purpose of implementing various requirements of the CWA. Prior to the Biden Administration,
executive branch efforts to define WOTUS administratively included regulations promulgated by
the Army Corps of Engineers (Corps) and the Environmental Protection Agency (EPA) in the
1980s and supplemented with interpretive guidance developed in response to Supreme Court
rulings; the 2015 Clean Water Rule; and the 2020 Navigable Waters Protection Rule.3 The
agencies’ efforts to define WOTUS in regulation during both the Obama and Trump
Administrations were controversial and led to litigation. Many observers viewed the Obama
Administration’s 2015 Clean Water Rule as defining WOTUS too broadly, while many viewed
the Trump Administration’s 2020 Navigable Waters Protection Rule as defining WOTUS too
narrowly. A federal district court vacated the Navigable Waters Protection Rule in September
2021, after which the Corps and EPA announced that they had halted implementation of the rule.4
On January 18, 2023, the Corps and EPA published a new rule (the 2023 WOTUS Rule) revising
the definition of WOTUS.5 The agencies have asserted that their intent in promulgating the 2023
WOTUS Rule was to redefine WOTUS in a durable regulation, updating the pre-2015 rules to
reflect consideration of Supreme Court decisions, science, and the agencies’ experience and
technical expertise.6
Some stakeholders have expressed support for the 2023 WOTUS Rule, in some cases observing
that the rule takes a middle road between the Clean Water Rule and the Navigable Waters
Protection Rule.7 Others have expressed opposition to the 2023 WOTUS Rule, arguing that it
does not provide regulatory clarity, is overly broad, and that the Corps and EPA should have
delayed issuing a rule pending the resolution of a Supreme Court case addressing aspects of the
scope of WOTUS. The new rule is scheduled to take effect on March 20, 2023, though it is

1 33 U.S.C. §1251 et seq.
2 33 U.S.C. §1362(7).
3 Army Corps of Engineers and EPA, “Clean Water Rule: Definition of ‘Waters of the United States’; Final Rule,” 80
Federal Register 37054, June 29, 2015 (hereinafter “2015 Clean Water Rule”); Army Corps of Engineers and EPA,
“The Navigable Waters Protection Rule: Definition of ‘Waters of the United States,’” 85 Federal Register 22250, April
21, 2020 (hereinafter “Navigable Waters Protection Rule”).
4 Pascua Yaqui Tribe v. EPA, 557 F. Supp. 3d 949 (D. Ariz. 2021).
5 Revised Definition of “Waters of the United States,” 88 Federal Register 3004, January 18, 2023 (hereinafter “2023
WOTUS Rule”). The final rule was published on January 18, 2023. The agencies released a pre-publication version of
the rule on December 30, 2022.
6 2023 WOTUS Rule, p. 3019. See also Corps and EPA, Final Rule: Revised Definition of ‘Waters of the United States’
Fact Sheet, December 2022, https://www.epa.gov/system/files/documents/2022-12/Public%20Fact%20Sheet.pdf
(hereinafter 2022 WOTUS Fact Sheet).
7 See, for example, David LaRoss, “Touting ‘Durable’ Approach, EPA Adopts Dual Tests in Revised WOTUS Rule,”
InsideEPA.com, December 30, 2022.
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Waters of the United States (WOTUS): Frequently Asked Questions

already the subject of litigation. Additionally, Members have introduced a joint resolution
disapproving the rule under the Congressional Review Act.
This report addresses frequently asked questions about WOTUS and the 2023 WOTUS Rule,
including actions taken by prior administrations, the contents of the new rule, stakeholder
responses and litigation, and options for Congress.
What Actions Have Previous Administrations Taken
to Define WOTUS?
Pre-2015 Rules and Guidance
For much of the past several decades, regulations promulgated by the Corps and EPA in 1986 and
1988, respectively, have been in effect.8 The agencies have supplemented these regulations with
interpretive guidance developed in response to Supreme Court rulings related to the scope of the
federal government’s ability to regulate WOTUS.9
One such Supreme Court case remains particularly relevant to the most recent efforts to redefine
WOTUS. In Rapanos v. United States, the Court considered the extent of CWA jurisdiction over
wetlands near ditches or man-made drains that emptied into traditional navigable waters.10 The
Court’s decision in Rapanos yielded three different opinions, none of which garnered a
controlling majority for a single standard to govern future jurisdictional disputes. Instead, the
decision resulted in two alternative tests for evaluating jurisdictional waters: a “relatively
permanent” test set forth by a four-Justice plurality in an opinion authored by Justice Antonin
Scalia, and a “significant nexus” test proposed by Justice Anthony Kennedy in a concurring
opinion.

8 Army Corps of Engineers, “Final Rule for Regulatory Programs of the Corps of Engineers,” 51 Federal Register
41206, November 13, 1986 (hereinafter “1986 Corps Rule”); EPA, “Clean Water Act Section 404 Program Definitions
and Permit Exemptions; Section 404 State Program Regulations,” 53 Federal Register 20764, June 6, 1988 (1988 EPA
Rule).
9 Army Corps of Engineers and EPA, “Appendix A, Joint Memorandum,” 68 Federal Register 1995, January 15, 2003;
Benjamin H. Grumbles, Assistant Administrator for Water, EPA, and John Paul Woodley Jr., Assistant Secretary of the
Army (Civil Works), Department of the Army, Clean Water Act Jurisdiction Following the U.S. Supreme Court’s
Decision in Rapanos v. United States & Carabell v. United States, memorandum, December 2, 2008 (hereinafter “2008
Guidance”).
10 547 U.S. 715 (2006).
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Rapanos and the Relatively Permanent and Significant Nexus Tests
The Plurality’s “Relatively Permanent” Test: Writing for a four-Justice plurality, Justice Scalia wrote that
the word “waters” in “waters of the United States” means only “relatively permanent, standing or continuously
flowing bodies of water”—that is, streams, rivers, and lakes.11 Wetlands could be included only when they have a
“continuous surface connection” to such waters.12
Justice Kennedy’s “Significant Nexus” Test: In a concurring opinion joined by no other Justice, Justice
Kennedy wrote that the Corps should determine on a case-by-case basis whether wetlands have a “significant
nexus” to traditionally navigable waters based on whether the wetland, either alone or in connection with similarly
situated properties, significantly impacts the chemical, physical, and biological integrity of a traditionally navigable
water.13
In response to the rulings, the agencies developed guidance to help clarify how EPA and Corps
offices should implement the Court’s decisions. In particular, the agencies expressed the view that
waters meeting either the relatively permanent standard articulated by Justice Scalia, or the
significant nexus standard articulated by Justice Kennedy, were subject to federal jurisdiction
under the act.14 However, the Corps and EPA acknowledged that their written guidance did not
provide the public or agency staff with the information needed to ensure timely, predictable, and
consistent jurisdictional determinations.15 Diverse stakeholders—including Members of
Congress, states, the regulated community, and nongovernmental organizations—requested a
formal rulemaking to revise the existing rules.16
2015 Clean Water Rule
In 2015, the Corps and EPA issued the Clean Water Rule, which redefined WOTUS in the
agencies’ regulations for the first time since the 1980s.17 The Clean Water Rule retained aspects of
the agencies’ earlier guidance and also incorporated new features, including a new definition of
tributaries and definitions and criteria related to adjacency.18
Some stakeholders and observers viewed the Clean Water Rule as an expansion of CWA
jurisdiction, while others argued that it excluded too many waters from federal jurisdiction.19
Numerous parties challenged the Clean Water Rule, and some district courts issued preliminary
injunctions temporarily barring the Clean Water Rule from taking effect in certain states.20 Two
courts also remanded the rule to the Corps and EPA, concluding that it violated the

11 Id. at 739.
12 Id. at 742.
13 Id. at 782 (Kennedy, J., concurring).
14 2008 Guidance; see also Rapanos, 547 U.S. at 810 (Stevens, J., dissenting).
15 2015 Clean Water Rule, p. 37056.
16 See EPA Web Archive at https://archive.epa.gov/epa/cleanwaterrule/what-clean-water-rule-does.html, which
includes a list of stakeholders requesting a rulemaking (https://archive.epa.gov/epa/sites/production/files/2014-03/
documents/wus_request_rulemaking.pdf).
17 2015 Clean Water Rule.
18 2015 Clean Water Rule, pp. 37057-37059, 37105-37106.
19 See, for example, Carolina Bolado, “Fla., Others Sue EPA, Corps Over Clean Water Act Expansion,” Law360, June
30, 2015; Center for Biological Diversity, “EPA and Army Corps Issue Weak Clean Water Rule,” press release, May
27, 2015, https://www.biologicaldiversity.org/news/press_releases/2015/clean-water-rule_05-27-2015.html.
20 North Dakota v. EPA, 127 F. Supp. 3d 1047 (D.N.D. 2015); Georgia v. Pruitt, 326 F. Supp. 3d 1356 (S.D. Ga. 2018);
Texas v. EPA, No. 3:15-cv-162, 2018 WL 4518230 (S.D. Tex. Sept. 12, 2018); Or. Cattlemen’s Ass’n v. EPA, No. 19-
00564 (D. Or. July 26, 2019).
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Administrative Procedure Act (APA) and exceeded the agencies’ statutory authority under the
CWA.21 As a result, until its rescission, the Clean Water Rule was in effect in a patchwork of
states. In states that were subject to a preliminary injunction or an order remanding the rule to the
Corps and EPA, the pre-2015 regulatory framework applied.
2020 Navigable Waters Protection Rule
The Trump Administration described the Clean Water Rule as an example of federal “overreach,”
and the Corps and EPA engaged in a two-step process to rescind and revise it.22 In Step One, the
Corps and EPA rescinded the Clean Water Rule and recodified the pre-2015 regulations.23
Accordingly, the pre-2015 regulations and guidance were in effect beginning on the effective date
of the Step One Rule (December 23, 2019), and until the agencies’ redefinition of WOTUS went
into effect. In April 2020, the Corps and EPA published a final Step Two Rule to redefine
WOTUS, titled the Navigable Waters Protection Rule.24 The rule went into effect on June 22,
2020, replacing the Step One Rule.
Overall, the Navigable Waters Protection Rule narrowed the scope of waters and wetlands that
were considered WOTUS (and were therefore under federal jurisdiction) compared to both the
Clean Water Rule and the pre-2015 rules. As with the Clean Water Rule, the Navigable Waters
Protection Rule prompted a range of reactions from a variety of stakeholders and resulted in
many lawsuits around the country.
President Biden signaled interest in reconsidering the Navigable Waters Protection Rule
immediately upon taking office.25 After announcing in June 2021 that they intended to revise the
definition of WOTUS again, the Corps and EPA asked courts where legal challenges to the
Navigable Waters Protection Rule were pending to remand the rule while they developed a new
regulation.26
On August 30, 2021, the U.S. District Court for the District of Arizona granted the agencies’
request for voluntary remand, but also vacated the rule.27 While the court did not issue a ruling on
the merits of the Navigable Waters Protection Rule, it found that both the plaintiffs and the United

21 Georgia v. Wheeler, 418 F. Supp. 3d 1336 (S.D. Ga. 2019); Texas v. EPA, 389 F. Supp. 3d 497 (S.D. Tex. 2019). In
this context, to “remand” means to return the rule to the agencies to reconsider possible errors or defects in their action.
A court order that remands a rule may or may not render the rule unenforceable during any further proceedings.
22 For example, EPA, “EPA, U.S. Army Repeal 2015 Rule Defining ‘Waters of the United States’ Ending Regulatory
Patchwork,” September 12, 2019, https://www.epa.gov/newsreleases/epa-us-army-repeal-2015-rule-defining-waters-
united-states-ending-regulatory-patchwork.
23 Army Corps of Engineers and EPA, “Definition of ‘Waters of the United States’—Recodification of Pre-Existing
Rules,” 84 Federal Register 56626, October 22, 2019.
24 Army Corps of Engineers and EPA, “The Navigable Waters Protection Rule: Definition of ‘Waters of the United
States,’” 85 Federal Register 22250, April 21, 2020.
25 Executive Order 13990, “Protecting Public Health and the Environment and Restoring Science to Tackle the Climate
Crisis,” 86 Federal Register 7037-7043, January 20, 2021.
26 EPA, “EPA, Army Announce Intent to Revise Definition of WOTUS,” press release, June 9, 2021, at
https://www.epa.gov/newsreleases/epa-army-announce-intent-revise-definition-wotus (hereinafter “June 2021 Press
Release”); see also, e.g., Motion for Remand Without Vacatur, Conservation Law Found. v. EPA, No. 1:20-cv-10820,
Doc. No. 112 (D. Mass. June 6, 2021).
27 Pascua Yaqui Tribe v. EPA, 557 F. Supp. 3d 949 (D. Ariz. 2021). One other court subsequently vacated the
Navigable Waters Protection Rule, adopting similar reasoning to the Pascua Yaqui court. Memorandum Opinion and
Order, Navajo Nation v. Regan, No. 2:20-cv-00602, Doc. No. 43 (D.N.M. Sept. 27, 2021). In this context, to “vacate”
the rule means to declare it invalid, as if the rule had never been in effect.
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States had identified concerns with the rule that involved fundamental, substantive, and incurable
flaws. In response to the order, the Corps and EPA announced that they had halted
implementation of the Navigable Waters Protection Rule and would interpret WOTUS consistent
with the pre-2015 regulatory regime until further notice.28
How Does the 2023 WOTUS Rule Define WOTUS?
The Corps and EPA have asserted that their intent in promulgating the 2023 WOTUS Rule was to
redefine WOTUS in a durable regulation, updating the pre-2015 rules to reflect consideration of
Supreme Court decisions, science, and the agencies’ experience and technical expertise.29 Overall,
the definition of WOTUS in the 2023 WOTUS Rule is narrower in scope than the Clean Water
Rule and broader than the Navigable Waters Protection Rule.
The 2023 WOTUS Rule is divided into three parts: jurisdictional waters (WOTUS), exclusions,
and definitions. These parts are summarized below, and compared to the pre-2015 rules and
guidance.
Jurisdictional Waters (WOTUS)
The 2023 WOTUS Rule includes seven WOTUS categories (Table 1).
Table 1. Jurisdictional Waters (WOTUS) Under the 2023 WOTUS Rule
Regulatory
Category of
Text
WOTUS
Description
Paragraph
Traditional Navigable Waters, such as large rivers and lakes, which are, were, or could be used
(a)(1)
Waters
in interstate or foreign commerce, including waters affected by tides.
Territorial Seas
The territorial seas are the belt of the seas extending three miles out
(a)(1)
from the coast.
Interstate Waters
Waters, such as rivers, lakes, streams, or wetlands that flow across or
(a)(1)
form part of state boundaries.
Impoundments of
Impounded waters created in or from jurisdictional waters, whether
(a)(2)
Jurisdictional Waters
natural (e.g., beaver ponds) or artificial (e.g., reservoirs).
Tributaries
Waters such as branches of creeks, streams, rivers, lakes, ponds, ditches,
(a)(3)
and impoundments that flow into traditional navigable waters, the
territorial seas, interstate waters, or impoundments of jurisdictional
waters. Tributaries are WOTUS if they meet either the relatively
permanent standard or the significant nexus standard as described further
in the 2023 WOTUS Rule.

28 See EPA, “Definition of ‘Waters of the United States’: Rule Status and Litigation Update,” December 30, 2022,
https://www.epa.gov/wotus/definition-waters-united-states-rule-status-and-litigation-update.
29 2023 WOTUS Rule, p. 3019; and 2022 WOTUS Fact Sheet.
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Regulatory
Category of
Text
WOTUS
Description
Paragraph
Adjacent Wetlands
Wetlands that are (1) adjacent to a traditional navigable water, the
(a)(4)
territorial seas, or an interstate water; (2) adjacent and with a continuous
surface connection to either relatively permanent jurisdictional
impoundments or jurisdictional tributaries that meet the relatively
permanent standard; or (3) wetlands adjacent to jurisdictional
impoundments or jurisdictional tributaries when the wetlands meet the
significant nexus standard.
Wetlands, defined in the rule, generally include swamps, marshes, bogs,
and similar areas. Adjacent is defined in the rule to mean “bordering,
contiguous, or neighboring.” The definition also specifies that wetlands
separated from other WOTUS by man-made dikes or barriers, natural
river berms, beach dunes, and the like are “adjacent wetlands.”
“Additional
Lakes, ponds, streams, or wetlands that do not fall under one of the other (a)(5)
waters”—intrastate
WOTUS categories. Such waters are jurisdictional if they meet either the
lakes and ponds,
relatively permanent or significant nexus standard.
streams, or wetlands
Source: CRS analysis; 2023 WOTUS Rule; 2022 WOTUS Fact Sheet.
Traditional Navigable Waters, the Territorial Seas and Interstate Waters
(Paragraph (a)(1) Waters)
The 2023 WOTUS Rule retains three categories without changes to the text or substance from
pre-2015 regulations.30 These include the traditional navigable waters, the territorial seas, and
interstate waters. However, the agencies restructured the rule to streamline the regulatory text,
and combined these three still-separate categories under one paragraph (i.e., (a)(1) waters)
because, as the agencies explain in the rule’s preamble, the jurisdictional status of other
categories of waters relies on their connection to waters from one of these three categories.31
Impoundments of Jurisdictional Waters
The 2023 WOTUS Rule also retains the impoundments of jurisdictional waters category with one
change from the pre-2015 regulations.32 The pre-2015 regulations included impoundments of any
WOTUS, but the 2023 WOTUS Rule would exclude impoundments of waters determined to be
jurisdictional under paragraph (a)(5), which the Corps and EPA in their fact sheet refer to as
“additional waters.”33 These “additional waters” are a subset of what was previously referred to as
the “other waters” category. (See further discussion on “additional waters” below.)
Tributaries, Adjacent Wetlands, and “Additional Waters”
The remaining three categories—tributaries, adjacent wetlands, and “additional waters”—reflect
the definition of WOTUS from pre-2015 regulations, but include changes that the agencies assert

30 2023 WOTUS Rule, p. 3068.
31 Ibid.
32 2023 WOTUS Rule, pp. 3075-3076.
33 2023 WOTUS Rule, p. 3066; and 2022 WOTUS Fact Sheet, p. 2. Note that impoundments of (a)(5) waters may still
be determined to be jurisdictional if they meet the requirements of another category of WOTUS.
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reflect Supreme Court precedent, science, and their technical expertise.34 For example, the 2023
WOTUS Rule clarifies that the waters in these three categories may meet either the relatively
permanent standard or the significant nexus standard for purposes of determining jurisdiction.35
The Corps and EPA explained that this aspect of the 2023 WOTUS Rule is not an application or
interpretation of the multiple opinions in Rapanos.36 Instead, these standards are contained in the
2023 WOTUS Rule text and are informed by, but separate from, the two tests identified by the
Supreme Court. In addition, the agencies made certain changes to each of the categories that
constrain which waters are jurisdictional, in comparison to the pre-2015 regulations.
 Tributaries: A tributary is considered a WOTUS under the 2023 WOTUS Rule if
it is a tributary of a traditional navigable water, the territorial seas, an interstate
water, or an impoundment of a jurisdictional water and also meets either the
relatively permanent or significant nexus standard.37
As compared to the pre-2015 regulations, the 2023 WOTUS Rule adds the
territorial seas to the list of waters to which a water may be a tributary. The
agencies note that, in practice, this is not a significant change as most tributaries
will reach a traditional navigable water before they reach the territorial seas.38
The 2023 WOTUS Rule also deletes the “additional waters” category from the
list of waters to which a water may be a tributary.39 The pre-2015 regulations
included the comparable “other waters” category on the list, and the “other
waters” category itself was broader, as discussed below.40
Similar to the pre-2015 regulations, the 2023 WOTUS rule does not contain a
definition of “tributary.”41 In addition, consistent with the pre-2015 regulations,
the 2023 WOTUS rule does not include or exclude tributaries as WOTUS based
on their flow regime (i.e., meaning whether they flow year-round, seasonally, or
only in response to precipitation events).42
 Adjacent wetlands: Under the 2023 WOTUS Rule, adjacent wetlands are
considered WOTUS if (1) they are adjacent to traditional navigable waters,
interstate waters, or the territorial seas; (2) they are adjacent to and with a

34 2023 WOTUS Rule, pp. 3005-3006; and 2022 WOTUS Fact Sheet.
35 Ibid.
36 2023 WOTUS Rule, p. 3022.
37 2023 WOTUS Rule, p. 3142.
38 2023 WOTUS Rule, pp. 3079-3080.
39 Ibid.
40 1986 Corps Rule, p. 41250.
41 2023 WOTUS Rule, pp. 3080-3081. Both the Clean Water Rule and the Navigable Waters Protection Rule included
a definition of “tributary.” In the preamble to the 2023 WOTUS Rule, the agencies concluded that a definition was not
required because the agencies have decades of experience implementing the 1986 regulations, which also did not
include a definition. Further, the agencies assert that they “articulate and explain the agencies’ well-established
interpretation and practices for identifying tributaries” in the preamble.
42 2023 WOTUS Rule, pp. 3080-3081. The rule’s preamble clarifies that “a tributary for purposes of this rule includes
rivers, streams, lakes, ponds, and impoundments, regardless of their flow regime, that flow directly or indirectly
through another water or waters to a traditional navigable water, the territorial seas, or an interstate water.” Note that
the Navigable Waters Protection Rule’s definition required that a tributary be perennial (i.e., flow year-round) or
intermittent (i.e., flow continuously only during certain times of the year, such as seasonally) and excluded ephemeral
streams (i.e., those that flow only in response to precipitation events). The Clean Water Rule’s definition provided that
a tributary could be perennial, intermittent, or ephemeral as long as other criteria in the definition were met.
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continuous surface connection to jurisdictional impoundments or tributaries that
meet the relatively permanent standard; or (3) they are adjacent to jurisdictional
impoundments or tributaries and meet the significant nexus standard.43 The pre-
2015 regulations more broadly included wetlands adjacent to waters in any of the
WOTUS categories, other than wetlands themselves.44 Thus, in comparison to the
pre-2015 regulations, the 2023 WOTUS Rule requires an additional
demonstration for wetlands adjacent to waters that are not (a)(1) waters, that the
wetlands have a continuous surface connection to a relatively permanent water or
a significant nexus to an (a)(1) water.45
 “Additional waters”: Under the 2023 WOTUS Rule, intrastate lakes, ponds,
streams, or wetlands not identified in the other WOTUS categories similarly must
meet either the relatively permanent standard or the significant nexus standard.46
The agencies clarify that this category is substantially narrower than the non-
exclusive list of “other waters” that was included under the pre-2015
regulations.47 The agencies also replaced the broad Commerce Clause basis for
jurisdiction from the pre-2015 regulations with the relatively permanent and
significant nexus standards.48
Exclusions
The 2023 WOTUS Rule includes eight exclusions from the definition of WOTUS.49 Some are
longstanding exclusions for prior converted cropland and waste treatment systems that were
included in pre-2015 regulatory text. Others exclude features that were generally considered non-
jurisdictional under the pre-2015 regime, but were listed as such in preamble language and
guidance rather than the regulatory text.50 Furthermore, these eight features were excluded in each
of the subsequent rules defining WOTUS (the Clean Water Rule and the Navigable Waters
Protection Rule), so the exclusions of the 2023 WOTUS Rule do not substantially change the
scope of federal jurisdiction.51 The exclusions include
 Waste treatment systems, including treatment ponds or lagoons designed to
meet the requirements of the CWA;
 Prior converted cropland (see discussion below);
 Ditches (including roadside ditches), excavated wholly in and draining only dry
land and that do not carry a relatively permanent flow of water;
 Artificially irrigated areas that would revert to dry land if the irrigation ceased;

43 2023 WOTUS Rule, p. 3142.
44 1986 Corps Rule, p. 41250.
45 2023 WOTUS Rule, pp. 3090, 3142.
46 2023 WOTUS Rule, p. 3142.
47 2023 WOTUS Rule, p. 3097.
48 Ibid. The pre-2015 regulatory framework included as jurisdictional waters “the use, degradation, or destruction of
which could affect interstate or foreign commerce.” 1986 Corps Rule, p. 41250.
49 2023 WOTUS Rule, pp. 3066-3067 and 3142-3143.
50 Ibid.
51 2023 WOTUS Rule, p. 3103. See also 2015 Clean Water Rule, p. 37118; 2020 Navigable Waters Protection Rule, p.
22340. Note these exclusions were either explicitly listed, or were excluded under a broader exclusion category.
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 Artificial lakes or ponds created by excavating or diking dry land to collect and
retain water and which are used exclusively for such purposes as stock watering,
irrigation, settling basins, or rice growing;
 Artificial reflecting pools or swimming pools or other small ornamental
bodies of water created by excavating or diking dry land to retain water for
primarily aesthetic reasons;
 Waterfilled depressions created in dry land incidental to construction activity
and pits excavated in dry land for the purpose of obtaining fill, sand, or gravel
unless and until the construction is abandoned and the resulting body of water
meets the definition of WOTUS; and
 Swales and erosional features (e.g., gullies, small washes) characterized by low
volume, infrequent, or short duration flow.
Regarding prior converted cropland, in the 2023 WOTUS Rule, the agencies repromulgated the
pre-2015 regulatory exclusion, but also made certain changes to the regulatory text in what the
agencies described as an effort to improve clarity and consistency with the implementation by the
U.S. Department of Agriculture (USDA) of the Food Security Act of 1985, as amended.52 The
Food Security Act includes a provision (the “Swampbuster” exception) which requires USDA to
make determinations about whether wetland areas qualify as prior converted cropland.53 The new
regulatory text in the 2023 WOTUS Rule specifies that prior converted cropland designated by
USDA is excluded. The regulatory text also clarifies that the exclusion would cease upon a
change of use, meaning the area is no longer available for the production of agricultural
commodities.54 This change aligns the WOTUS regulatory exclusion with the Swampbuster
exception for prior converted cropland.55
Definitions
The 2023 WOTUS Rule includes six definitions. Five of the six definitions are unchanged from
the pre-2015 regulations, including the definitions for “wetlands,” “adjacent,” “high tide line,”
“ordinary high water mark,” and “tidal water.”56
The 2023 WOTUS Rule newly defines the term “significantly affect,” for purposes of
determining whether a water meets the significant nexus standard, to mean “a material influence
on the chemical, physical, or biological integrity” of an (a)(1) water (i.e., traditional navigable
waters, the territorial seas, or interstate waters).57 The definition also identifies functions to be
assessed and factors to be considered in determining whether waters, either alone or in
combination with similarly situated waters in the region, significantly affect an (a)(1) water.58

52 2023 WOTUS Rule, pp. 3105-3107.
53 See CRS In Focus IF11136, Prior Converted Cropland Under the Clean Water Act, by Laura Gatz and Megan
Stubbs for more information.
54 2023 WOTUS Rule, p. 3142.
55 2023 WOTUS Rule, pp. 3105-3107.
56 2023 WOTUS Rule, pp. 3067, 3143.
57 Ibid.
58 Ibid. Functions, as listed in the rule, include contribution of flow; trapping, transformation, filtering, and transport of
materials (including nutrients, sediment, and other pollutants); retention and attenuation of floodwaters and runoff;
modulation of temperature in paragraph (a)(1) waters; or provision of habitat and food resources for aquatic species in
paragraph (a)(1) waters. Factors, as listed in the rule, include the distance from a paragraph (a)(1) water; hydrologic
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Which Rule Is in Effect Now?
The 2023 WOTUS Rule is scheduled to take effect on March 20, 2023. Until the 2023 WOTUS
Rule takes effect, the pre-2015 regulatory framework applies, as it has since a federal district
court vacated the Navigable Waters Protection Rule in August 2021.59
Litigation could change which rule is in effect. Previous lawsuits challenging the Clean Water
Rule and the Navigable Waters Protection Rule resulted in preliminary injunctions and other
rulings that barred implementation of the challenged rule and resulted in a prior regulatory
framework returning to effect, at least in some places.60 While no party challenging the 2023
WOTUS Rule has sought a preliminary injunction, future rulings could result in similar
limitations on the rule’s implementation.
A change in regulatory regime does not result in the retroactive application of a new rule to all
potentially covered waters. In particular, the transition to the 2023 WOTUS Rule does not
necessarily invalidate approved jurisdictional determinations (or AJDs), which the Corps issues to
identify whether a particular parcel of land contains WOTUS, and which may be used in the
CWA permitting process.61 Approved jurisdictional determinations completed when the
Navigable Waters Protection Rule or pre-2015 regulatory framework was in effect will not be
reopened before their expiration date unless they satisfy specific criteria for revision.62
Additionally, enforcement actions for violations of the CWA are typically based on the statutory
and regulatory framework that was in effect at the time the violations occurred, even if the rule
has since changed.
Has the 2023 WOTUS Rule Been Challenged in
Court?
To date, two pending lawsuits challenge the 2023 WOTUS Rule. Both lawsuits were filed on
January 18, 2023, in the U.S. District Court for the Southern District of Texas.
First, the State of Texas argues that the rule unlawfully expands the Corps and EPA’s jurisdiction
beyond the bounds of the CWA, violates the major questions doctrine63 because the CWA does
not authorize the agencies to determine the scope of their own jurisdiction, intrudes upon state
sovereignty, and violates due process by failing to provide adequate notice of what conduct is
prohibited under the statute.64 Second, a coalition of agricultural and industry groups argues that

factors such as the frequency, duration, magnitude, timing, and rate of hydrologic connections, including shallow
subsurface flow; the size, density, or number of waters that have been determined to be similarly situated; landscape
position and geomorphology; and climatological variables such as temperature, rainfall, and snowpack.
59 EPA, “Definition of ‘Waters of the United States’: Rule Status and Litigation Update,” December 30, 2022,
https://www.epa.gov/wotus/definition-waters-united-states-rule-status-and-litigation-update.
60 For a discussion of litigation regarding the 2015 Clean Water Rule, see 2023 WOTUS Rule, p. 3016.
61 See 33 C.F.R. § 331.2.
62 See EPA, “Current Implementation of Waters of the United States,” January 18, 2023, https://www.epa.gov/wotus/
current-implementation-waters-united-states; and U.S. Army Corps of Engineers, Regulatory Guidance Letter No. 05-
02 (June 14, 2005).
63 Under the major questions doctrine, an agency must provide clear congressional authorization in certain cases when
it seeks to decide an issue of major national significance. For additional background on the major questions doctrine,
see CRS In Focus IF12077, The Major Questions Doctrine, by Kate R. Bowers.
64 Complaint, Texas v. EPA, No. 3:23-cv-00017, Doc. No. 1 (S.D. Tex. Jan. 18, 2023).
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the rule is unsupported by law and scientific and economic evidence; violates the Commerce
Clause, the Due Process Clause of the Fifth Amendment, the major questions doctrine, and the
nondelegation doctrine;65 exceeds the Corps’ and EPA’s statutory authority; and unlawfully fails
to include a regulatory flexibility analysis.66
Other stakeholders could challenge the 2023 WOTUS Rule, and some have indicated that they
intend to do so.67 Consistent with the statute of limitations for Administrative Procedure Act
(APA) claims, potential litigants would generally be required to file suit within six years after
their claim accrues.68 Early lawsuits are the most likely to be closely watched, as they will be the
courts’ first opportunities to issue rulings that may be binding in later cases, and because they will
occur before the regulated public has substantially relied on the rule.
Prior rules defining WOTUS were the subject of numerous lawsuits filed by industry groups,
environmental groups, and states. In 2018, the Supreme Court held that challenges to a rule
defining WOTUS are typically governed by the APA and must be reviewed first in federal district
court.69 That holding limited the degree to which the agencies, under rules of court procedure, can
seek a single nationwide decision about the validity of the 2023 WOTUS Rule.
If states or stakeholders challenge the 2023 WOTUS Rule, individual courts may consider
whether to bar implementation of the rule while litigation is pending. As in litigation over the
2015 and 2020 rules, the issuance of one or more preliminary injunctions would limit the
applicability of the rule and leave in place the prior regulatory framework where any such
injunction was in effect.
A case currently pending before the Supreme Court could also affect the definition of WOTUS. In
Sackett v. EPA, landowners challenging a particular compliance order have asked the Court more
broadly to revisit Rapanos and adopt Justice Scalia’s plurality test for determining whether
certain adjacent wetlands are WOTUS.70 The U.S. Court of Appeals for the Ninth Circuit upheld
EPA’s conclusion that the Sacketts’ property contained WOTUS that were subject to federal
jurisdiction under the CWA and relevant regulations.71 EPA has argued that the Court should
continue to allow the use of Justice Kennedy’s significant nexus test to identify covered
wetlands.72
The Supreme Court held oral argument in Sackett on October 3, 2022, and a decision is expected
later this term. Although no agency regulation is presented for the Court’s review in Sackett, a
decision from the Court could affect the implementation or future judicial review of the 2023
WOTUS Rule, particularly with respect to the rule’s provisions regarding the jurisdiction of
adjacent wetlands. Additionally, although the Corps and EPA stated in the 2023 WOTUS Rule

65 The nondelegation doctrine is the separation-of-powers principle that limits Congress’s ability to cede its legislative
power to other branches of government or non-governmental entities. For further discussion of the nondelegation
doctrine, see Nondelegation Doctrine, Constitution Annotated, https://constitution.congress.gov/browse/article-1/?
anchor=I_S1_5#I_S1_5.
66 Complaint, Am. Farm Bureau Fed’n v. EPA, No. 3:23-cv-00020, Doc. No. 1 (S.D. Tex. Jan. 18, 2023).
67 E.g., Office of the Governor, State of North Dakota, “Burgum issues statement calling on Biden administration to
withdraw new Waters of the U.S. rule,” January 18, 2023, https://www.governor.nd.gov/news/burgum-issues-
statement-calling-biden-administration-withdraw-new-waters-us-rule.
68 28 U.S.C. § 2401(a).
69 Nat’l Ass’n of Mfrs. v. Dep’t of Def., 138 S. Ct. 617 (2018).
70 Sackett v. EPA, cert. granted, 142 S. Ct. 896 (No. 21-454) (U.S. Jan. 24, 2022).
71 Sackett v. EPA, 8 F.4th 1075 (9th Cir. 2021).
72 Brief for Respondents at 31, 33–34, 35, Sackett v. EPA, No. 21-454 (U.S. June 10, 2022).
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preamble that their interpretation of the CWA is “not an interpretation of the multiple opinions in
Rapanos,”73 a Supreme Court holding that considers the continued viability of the standards
outlined in Rapanos would be relevant to the corresponding relatively permanent and significant
nexus tests that the agencies incorporated into the 2023 WOTUS Rule.
What Options Are Available to Congress Regarding
the Definition of WOTUS?
Considering the numerous court rulings, ongoing legal challenges, and issues that successive
administrations have faced in defining the scope of WOTUS, some stakeholders have urged
Congress to more specifically define the term through amendments to the CWA. Others argue that
the Corps and EPA, with their specific knowledge and expertise, are in the best position to
determine the scope of the term.
Congress can also stop agency rulemaking or regulatory enforcement through provisions added to
agency appropriations legislation. Such appropriations provisions could include (1) restrictions on
the finalization of particular proposed rules, (2) restrictions on regulatory activity within certain
areas, (3) implementation or enforcement restrictions, and (4) conditional restrictions (e.g.,
preventing implementation of a rule until certain actions are taken).74
In the 118th Congress, 152 Members of the House of Representatives and 48 Senators introduced
joint resolutions disapproving the 2023 WOTUS Rule.75 The resolutions were introduced under
the Congressional Review Act (CRA), a law that allows Congress to overturn certain agency
actions in the form of a joint resolution of disapproval.76 Under the CRA, if both houses pass a
joint resolution for disapproval, it is sent to the President for signature or veto. If the President
were to veto a resolution, Congress could vote to override the veto with a two-thirds majority in
both chambers. If a joint resolution of disapproval is submitted within the CRA-specified
deadline, passed by Congress, and signed by the President (or if Congress votes to override a
presidential veto), the disapproved rule “shall not take effect (or continue),” and would be
deemed not to have had any effect at any time. Furthermore, if a joint resolution of disapproval is
enacted, the CRA provides that a rule may not be issued in “substantially the same form” as the
disapproved rule unless it is specifically authorized by a subsequent law.
In the 117th and 116th Congresses, some Members introduced legislation related to the scope of
WOTUS. Some of these bills would have enacted the Navigable Waters Protection Rule’s
definition of WOTUS into law, or amended the CWA to add a narrower definition of navigable
waters.77 Other bills introduced prior to the vacatur of the Navigable Waters Protection Rule or

73 2023 WOTUS Rule, p. 3021.
74 CRS Report RL32240, The Federal Rulemaking Process: An Overview, coordinated by Maeve P. Carey.
75 H.J.Res. 27 (118th Cong.); S.J.Res. 7 (118th Cong.).
76 5 U.S.C. § 801. For additional information about the CRA, see CRS Report R43992, The Congressional Review Act
(CRA): Frequently Asked Questions, by Maeve P. Carey and Christopher M. Davis.
77 For example, Withstanding Attempts to Encroach on our Resources (WATER) Act, H.R. 2660 (117th Congress);
H.Res. 318 (117th Congress); S.Res. 17 (117th Congress); Define WOTUS Act of 2021, H.R. 4570 and S. 2168 ((117th
Congress); Defense of Environment and Property Act of 2021, H.R. 5849 and S. 2517 (117th Congress); Navigable
Waters Protection Act of 2022, S. 3456 (117th Congress). Because WOTUS is a statutory phrase that defines navigable
waters, a different definition of the latter term could obviate the need to interpret the former, though it could introduce
new interpretive questions.
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the repeal of the Clean Water Rule addressed the implementation of those rules, respectively.78
Additionally, committees in the 117th and 116th Congresses held hearings regarding WOTUS.79
Moving forward, Congress may oversee the Biden Administration’s implementation of the
revised definition, or may consider introducing legislation that provides a definition of WOTUS
or expresses a clearer intent as to how Congress believes the term should be defined.

Author Information

Kate R. Bowers
Laura Gatz
Legislative Attorney
Specialist in Environmental Policy

Disclaimer
This document was prepared by the Congressional Research Service (CRS). CRS serves as nonpartisan
shared staff to congressional committees and Members of Congress. It operates solely at the behest of and
under the direction of Congress. Information in a CRS Report should not be relied upon for purposes other
than public understanding of information that has been provided by CRS to Members of Congress in
connection with CRS’s institutional role. CRS Reports, as a work of the United States Government, are not
subject to copyright protection in the United States. Any CRS Report may be reproduced and distributed in
its entirety without permission from CRS. However, as a CRS Report may include copyrighted images or
material from a third party, you may need to obtain the permission of the copyright holder if you wish to
copy or otherwise use copyrighted material.

78 E.g., Clean Water for All Act, H.R. 6745 (116th Congress); Federal Regulatory Certainty for Water Act, H.R. 2287
(116th Congress); Regulatory Certainty for Navigable Waters Act, H.R. 667 (116th Congress).
79 U.S. Congress, House Committee on Appropriations, Subcommittee on Interior, Environment, and Related Agencies,
Hearing on the Fiscal Year 2023 Budget Request for the Environmental Protection Agency, 117th Cong., 2nd sess.,
April 29, 2022. U.S. Congress, Senate Committee on Environment and Public Works, Hearing on Fiscal Year 2023
Environmental Protection Agency Budget, 117th Cong., 2nd sess., April 6, 2022. U.S. Congress, House Committee on
Transportation and Infrastructure, Subcommittee on Water Resources and Environment, President Biden’s Fiscal Year
2022 Budget Request: Agency Policies and Perspectives (Part II), 117th Cong., 1st sess., July 14, 2021. U.S. Congress,
House Committee on Transportation and Infrastructure, Subcommittee on Water Resources and Environment,
President Biden’s Fiscal Year 2022 Budget Request: Agency Policies and Perspectives (Part I), 117th Cong., 1st sess.,
June 24, 2021. U.S. Congress, Senate Committee on Environment and Public Works, Hearing on the Nomination of
Michael S. Regan to be Administrator of the Environmental Protection Agency, 117th Cong., 1st sess., February 3, 2021,
S.Hrg. 117-1; U.S. Congress, House Committee on Transportation and Infrastructure, Subcommittee on Water
Resources and Environment, The Administration’s Priorities and Policy Initiatives Under the Clean Water Act, 116th
Cong., 1st sess., September 18, 2019, H.Hrg. 116-31. U.S. Congress, Senate Committee on Environment and Public
Works, Hearing on the Nomination of Andrew Wheeler to be Administrator of the Environmental Protection Agency,
116th Cong., 1st sess., January 16, 2019, S.Hrg. 116-9. U.S. Congress, Senate Committee on Environment and Public
Works, A Review of Waters of the U.S. Regulations: Their Impact on States and the American People, 116th Cong., 1st
sess., June 12, 2019, S.Hrg. 116-45. U.S. Congress, Senate Committee on Environment and Public Works, Oversight of
the Environmental Protection Agency, 116th Cong., 2nd sess., May 20, 2020, S.Hrg. 116-391. U.S. Congress, Senate
Committee on Environment and Public Works, Stakeholder Reactions: The Navigable Waters Protection Rule under
the Clean Water Act, 116th Cong., 2nd sess., September 16, 2020.
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