Trump Administration Issues Draft Rule Redefining “Waters of the United States”

Today, the Environmental Protection Agency (EPA) and the Army Corps of Engineers (USACE) published a proposed rule to further revise the definition of “waters of the United States” or WOTUS. For more than 50 years, this definition has determined which water bodies the federal government regulates under the Clean Water Act (CWA) and which may be regulated—if at all—under state law. The Trump administration first announced plans to amend CWA’s scope through a new WOTUS definition in March 2025.

The draft rule narrows federal jurisdiction in alignment with a landmark Supreme Court decision: focusing on “relatively permanent” standing or continuously flowing waters, plus wetlands that have a continuous surface connection to those waters.

History of WOTUS

To put the proposed rule in context, it’s helpful to know something about the history of how WOTUS has been defined. Although the CWA established federal jurisdiction over WOTUS with the primary goals of restoring and protecting the quality of the nation’s surface waters, it does not define the term WOTUS but instead authorizes EPA and USACE to do so in regulations.

For decades, the jurisdictional scope of the CWA was detailed in regulations promulgated by USACE and EPA in 1986 and 1988, respectively. These regulations defined WOTUS as traditional navigable waters, interstate waters, all other waters that could affect interstate or foreign commerce, impoundments of waters of the United States, tributaries, the territorial sea and adjacent wetlands. A 2006 Supreme Court ruling in Rapanos v. United States, 547 U.S. 715, however, put pressure on these regulatory definitions but did not provide clear guidance because the court could not agree on a definition of WOTUS; a four-justice plurality opinion set forth a “relatively permanent” flow standard, while Justice Anthony Kennedy concurred in the judgment but wrote separately to apply a “significant nexus” standard. See our June 8, 2023, Client Alert for more on the Rapanos decision.

In light of the ambiguity caused by Rapanos, in 2015 the Obama administration issued the Clean Water Rule that redefined WOTUS in regulations for the first time since the 1980s. While this rule maintained much of the agencies’ prior regulations, it adopted a clear definition of “tributaries.” The 2015 rule defined tributaries as waters characterized by physical indicators of flow, such as a bed and a bank with an ordinary high water mark. This definition also required tributaries to contribute flow directly or indirectly to a traditional navigable water, an interstate water, or the territorial seas. The Clean Water Rule also defined the term “adjacent waters” as those “bordering, contiguous, or neighboring,” including those separated from other WOTUS.

The Trump administration repealed this rule in 2019 and later replaced it with the Navigable Waters Protection Rule (NWPR) in 2020. This rule maintained tributaries as a jurisdictional water, but redefined the term to exempt ephemeral tributaries, which flow only during precipitation. The rule also excluded ditches and redefined adjacent waters to include only wetlands that (1) directly abut other regulated waters or (2) are separated from other jurisdictional waters by natural berms, banks, dunes, or permeable artificial barriers such as dikes, levees or roads. The NWPR was stayed pending litigation until it was vacated by two district courts and replaced in early 2023.

In January 2023, the Biden administration published the Revised Definition of “Waters of the United States” (Conforming Rule). This rule aimed to return to the pre-2015 WOTUS definition, with amendments and exemptions to incorporate principles laid out in Rapanos:

• The “relatively permanent standard” requires relatively permanent, standing or continuously flowing water connected to traditional navigable waters with a continuous surface connection.
• The “significant nexus standard” requires water, either alone or in combination, to significantly affect the chemical, physical or biological integrity of a navigable water.

As noted in our January 2023 Client Alert, the 2023 rule stated that tributaries, adjacent wetlands, and “additional waters” are under federal jurisdiction if they satisfy either of the two standards set forth in Rapanos. The Biden administration also codified the agencies’ longstanding guidance excluding from WOTUS prior converted cropland that remains available for crop production and waste treatment.

However, the 2023 Conforming Rule had to be amended quickly: in May 2023, the Supreme Court further narrowed the scope of WOTUS in Sackett v. EPA, 598 U.S. 651 (2023) (“Sackett II”). In a 5-4 decision, the court rejected the Ninth Circuit’s application of the “significant nexus” test from Rapanos and held that EPA and USACE may only regulate wetlands “with a continuous surface connection” to a WOTUS such that they are “indistinguishable” from those waters. In August 2023, EPA and USACE released Amended 2023 Rule to update the definition of WOTUS in response to the Sackett II decision. Litigation quickly ensued based on claims that the 2023 Amended Rule did not hew closely enough to Sackett II. Currently, the revised 2023 WOTUS rule is in effect in 24 states and the District of Columbia. As a result of ongoing litigation, however, in the other 26 states WOTUS is implemented under the pre-2015 regulatory regime and the Supreme Court’s Sackett II decision.

The 2025 Proposed WOTUS Rule

The 2025 proposed rule aims to more fully implement the Sackett II decision by clarifying the definition of WOTUS. It proposes to narrow which waters are under federal jurisdiction in accordance with Sackett II and aims to make enforcement clearer and more predictable. Among the significant proposed changes:

• Redefining “relatively permanent”as “standing or continuously flowing bodies of surface water that are standing or continuously flowing year-round or at least during the wet season,” and eliminate ephemeral waters from jurisdiction “because they are not relatively permanent” as it pertains to waters that are standing or continuously flowing year-round, or at least during the “wet season.”
• Deleting “interstate waters” and the delimiter “intrastate” from “intrastate lakes and ponds” in the definition of WOTUS because they can otherwise encompass bodies of water that are not relatively permanent, standing, or continuously flowing or that are not connected to a downstream traditional navigable water or the territorial seas.
• Defining “tributary” to ensure that only relatively permanent bodies of water that meet specific requirements be considered under federal jurisdiction. The proposed rule would clarify that the definition does not include “a body of water that contributes surface water flow to a downstream jurisdictional water through a feature such as a channelized non-jurisdictional surface water feature, subterranean river, culvert, dam, tunnel, or similar artificial feature, or through a debris pile, boulder field, wetland, or similar natural feature, if such feature does not convey relatively permanent flow.” However, a tributary would retain jurisdictional status when it is part of an operational “water transfer” (40 C.F.R. § 122.3).
• “Continuous surface connection” would now require wetlands to meet a new two-part testto be jurisdictional: (1) they must abut (i.e., touch) a jurisdictional water, and(2) they must have surface water at least during the “wet season.” Both adjacent wetlands and relatively permanent lakes and ponds (paragraphs (a)(4) and (5)) must have a continuous surface connection to a WOTUS to be jurisdictional. The rule would not disturb the current the definition of “adjacent” (“having a continuous surface connection”). 33 C.F.R. § 328.3(c)(2), 40 C.F.R. § 120.2(c)(2).
• Groundwater, including groundwater drained through subsurface drainage systems (e.g., tile drains), would be explicitly excluded from WOTUS, although this exclusion would not apply to groundwater that becomes part of baseflow in relatively permanent streams.

The proposed rule would also provide regulatory definitions for “ditch,” “prior converted cropland,” and “waste treatment system” to clarify the application of statutory exemptions from WOTUS coverage. For example, under the proposal, the exclusion for “prior converted cropland” would no longer apply when the cropland is abandoned and the land has reverted to wetlands. This updated definition would enable agencies to more readily identify prior converted cropland.

The proposal’s effects on wetlands and streams will likely vary, with arid states generally the most likely to see decreases in federal jurisdiction.

Next Steps

Once the rule is published in the Federal Register, the public will have 45 days to submit comments. EPA and USACE will host two hybrid public meetings. Details about commenting either in writing or during the public meetings can be found on EPA’s website here.

Once the rule is final, we expect it will draw legal challenges from environmental groups and attorneys general across the country. In past legal challenges to WOTUS rules, district court decisions have created a patchwork across the country where in some places the rule has been suspended, while in others it has gone into effect. We expect such challenges will further fragment the status of federal jurisdiction nationwide and make project planning and compliance more difficult, at least until litigation is resolved.

The Brownstein team will continue to monitor the regulatory landscape and can assist in evaluating the possible impacts and developing a strategy to respond, including through public comment.

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This document is intended to provide you with general information regarding the definition of “waters of the United States.” The contents of this document are not intended to provide specific legal advice. If you have any questions about the contents of this document or if you need legal advice as to an issue, please contact the attorneys listed or your regular Brownstein Hyatt Farber Schreck, LLP attorney. This communication may be considered advertising in some jurisdictions. The information in this article is accurate as of the publication date. Because the law in this area is changing rapidly, and insights are not automatically updated, continued accuracy cannot be guaranteed.