California Water Views

On November 17, 2025, the Environmental Protection Agency (EPA) and Army Corps of Engineers (Corps) (collectively, Agencies) announced a proposed rule (Proposed Rule) to revise the regulatory definition of “waters of the United States” (WOTUS). The Proposed Rule was published in the Federal Register on November 20, 2025, starting the 45-day public comment period, which closes on January 5, 2026.

This Proposed Rule represents the latest iteration of the WOTUS definition, which has seen five finalized rules and one U.S. Supreme Court decision since 2015.

Background

As the Agencies detailed in their Proposed Rule, the definition of WOTUS, especially since 2015, has involved substantial instability both as a result of varying regulatory changes across presidential administrations and decisions issued by federal courts.

Most recently, and previously detailed, the U.S. Supreme Court (SCOTUS) issued a decision in Sackett v. Environmental Protection Agency, 598 U.S. 651 (2023), in which SCOTUS held that a wetland only qualifies as a WOTUS if it is “as a practical matter indistinguishable from waters of the United States.” (Id. at 678 [quotation marks and citation omitted.) To meet this “indistinguishable” test, a party must prove (1) that the wetland is adjacent to a WOTUS (i.e., “a relatively permanent body of water connected to traditional interstate navigable waters”) and (2) “that the wetland has a continuous surface connection with that water, making it difficult to determine where the ‘water’ ends and the ‘wetland’ begins.” (Id. at 678-679 [emphases added].) We analyzed the practical impact of this decision here.

Although the Biden administration had already promulgated a revised definition of WOTUS, in response to Sackett, the administration issued an updated 2023 WOTUS rule (Conforming Rule). The Conforming Rule represented a relatively broad approach to the definition of WOTUS while attempting to be consistent with the Court’s holding in Sackett. The Conforming Rule was stayed in court and is still subject to litigation. Shortly following his inauguration in 2025, President Trump signaled that his administration would be issuing its own WOTUS rule, taking a much narrower view of Sackett (as briefed here and detailed here).

Proposed Changes

The Proposed Rule would revise the EPA and Corps’ Clean Water Act implementing regulations (Regulations) found at 40 CFR § 120.2 and 33 CFR § 328.3 respectively (note: the regulations are the same for both agencies).

Definitional Changes

The Proposed Rule seeks to change subsections (c) of the regulations, which set out the definitions that apply to those Regulations.

• (3) Continuous surface connection is defined as “having surface water at least during the wet season and abutting (e., touching) a jurisdictional water.”
  • The Proposed Rule goes into depth on what qualifies as a wet season, including noting that there will be different wet seasons in different parts of the country.
  • The Proposed Rule acknowledges that this definition will likely lead to “few wetlands being found to have a continuous surface connection under the proposed rule, particularly in the arid West.”
• (4) Ditch is defined as “a constructed or excavated channel used to convey water.”
• (7) Prior converted cropland is completely re-defined. The two primary changes are (1) removing the necessity of a designation from the U.S. Department of Agriculture (USDA) to qualify as prior converted cropland and (2) removing “change of use” as the way to lose prior converted cropland status and replacing it with “abandonment”, which is defined in the broader definition.
• (8) Relatively permanent is defined as “standing or continuously flowing bodies of surface water that are standing or continuously flowing year-round or at least during the wet season.”
  • Through its inclusion here and in the definition of “continuous surface connection”, the definition of what constitutes the “wet season” will become a significant undefined term. The preamble for the rule and any changes therein between the proposed and final rule will likely be utilized by courts to interpret that term.
• (10) Tributary is defined as “a body of water with relatively permanent flow, and a bed and banks, that connects to a downstream traditional navigable water or the territorial seas, either directly or through one or more waters or features that convey relatively permanent flow.” The definition also provides details on what does not qualify (and lists examples) and on tributaries in water transfers.
• (11) Waste treatment system adds that the term “means all components of a waste treatment system …. designed to either convey or retain, concentrate, settle, reduce, or remove pollutants, either actively or passively, from wastewater prior to discharge (or eliminating any such discharge.”

Changes to What Qualifies as WOTUS

The Proposed Rule would revise subsection (a) of the Regulations, which define what features qualify as WOTUS.

• Removal of “Interstate waters” from the WOTUS definition.
  • According to the Proposed Rule, the practical impact of this removal is to remove only those interstate waters that do not otherwise qualify as WOTUS under a different part of the definition.
    • The Proposed Rule describes an analysis that found only 15 waterbodies qualified specifically as interstate (e., not under any other part of the definition) from 2015-2025 and thus it states “The change would likely have few practical impacts and would not undermine significant reliance interests”.
• Removal of “Intrastate” as an adjective for ponds and lakes.
  • This is described as a “ministerial change” flowing from removing “interstate waters” as its own category.
  • Together, the practical impact of eliminating “interstate waters” as an independent basis for jurisdictional and removing the “intrastate” qualifier for ponds and lakes is that lakes and ponds (whether interstate or intrastate) now only qualify as WOTUS where they are “relatively permanent, standing or continuously flowing bodies of water with a continuous surface connection to” other WOTUS. In other words, the fact that a lake or pond is interstate alone is insufficient to qualify as WOTUS, it must also meet the latter condition as well.

Changes to What Does Not Qualify

The Proposed Rule seeks to change subsections (b) of the regulations, which define exceptions for waterbodies that would otherwise qualify as WOTUS.

• Simplified exclusions: waste treatment systems and prior converted cropland
  • The Proposed Rule removes the descriptive language from the two above exclusions, instead just listing those terms by themselves and relying on the new definitions in section (c).
  • The practical impacts of the simplified exclusions combined with the new definitions are:
    • For waste treatment systems, the effect of the changes is unclear, as the new definition seems to align with the prior exception while providing additional details. In net, it seems like the new definition is broader than the existing exception, so any practical change would likely be a broader exception and thus a shrinking of what qualifies as WOTUS.
    • For prior converted cropland, the removal of the USDA from the designation process appears to expand the exception and the change from “change of use” to “abandonment” seems to shrink the exception to the exception. Thus, both make the exception more broadly applicable and shrink the definition of what qualifies as WOTUS.
• Modified exclusion: ditches.
  • The three primary modifications are (1) removing the requirement that ditches drain only dry land to qualify for the exception; (2) removing the requirement that ditches “do not carry a relatively permanent flow of water” to qualify for the exception; and (3) adding that ditches can qualify for the exception if they were “constructed … entirely in dry land.”
    • Modifications (1) and (2) make it easier to qualify for the exception and (3) adds in new ditches that would not have otherwise qualified. As such, this modification expands the exception to the WOTUS definition and results in less area qualifying as WOTUS.
• New exclusion: Groundwater, including groundwater drained through subsurface drainage systems.
  • The Proposed Rule notes that while pollutants released via groundwater can reach surface water, excluding groundwater is more consistent with the focus on “navigable waters” that underlies the WOTUS definition.
    • Although groundwater is generally regulated by states and therefore pollutants released via groundwater would similarly be managed by states, a primary effect of this change is to expand the exception for treatment systems that use infiltration as a treatment method. A second primary effect of the revision is to better assure that groundwater connections to surface water are no longer considered in delineating agency permitting authority. The administration likely desires this additional assurance because groundwater connections were prominently considered under the prior significant nexus test for determining connectivity of surface waters to traditionally navigable waters (TNWs) establishing regulatory jurisdiction over non-TNW surface waters.

Other Potential Changes

On top of the changes listed in the Proposed Rule, the Agencies are also soliciting comments on a variety of other issues that may expand or contract the definition of WOTUS. Some of the most noteworthy issues are:

• “[A]pproaches for increasing predictability in jurisdictional determinations, including options for leveraging data and tools”;
• Utilizing a completely different approach to WOTUS – only “encompass[ing] traditional navigable waters, tributaries that directly flow into these waters, and wetlands with a continuous surface water connection to such waters”;
• How to define key terms including “relatively permanent waters”, “wet season”, and “continuous surface connection”;
  • The Proposed Rule lists multiple potential approaches to each of these terms.
• Whether to remove the lakes and ponds category altogether; and
• Whether to significantly expand the ditch exclusion

Impacts

According to the Agencies’ respective press releases, the Proposed Rule “would establish a clear, durable, common-sense definition of” WOTUS. It is meant to “Protect Water Resources, Accelerate Growth & Economic Opportunity” and “will cut red tape and provide predictability, consistency, and clarity for American industry, energy producers, the technology sector, farmers, ranchers, developers, businesses, and landowners for permitting under the Clean Water Act.”

It is all but a foregone conclusion that various groups will challenge any final rule revising the definition of WOTUS. In the days since the Agencies’ release of the Proposed Rule, it is clear that opponents view the Proposed Rule as improperly narrowing the scope of Clean Water Act jurisdiction. The National Resources Defense Council (NRDC) notes that a study it completed based on anticipated changes similar to those set forth in the Proposed Rule would risk 38-70 million acres of wetlands and would remove coverage for ephemeral streams, which contribute over half of the water flowing in larger mainstem rivers.

One thing that is not debatable is that the Proposed Rule removes a substantial number of waterbodies from the definition of WOTUS that would have been jurisdictional under some previous iterations and, thus, the Proposed Rule is de-regulatory in nature. By defining key terms such as “continuous surface connection” and “relatively permanent” on the principles set forth in Sackett, the Proposed Rule should provide additional clarity on the definition of WOTUS for some within the regulated community, something that it has long sought, as discussed in all of the various WOTUS rules proposed since 2015.

Next Steps

Now that the Proposed Rule has been posted in the Federal Register, the public has 45 days to provide comment on the rule, ending on January 5, 2026. Comments may be made via online submission, email, mail, and hand delivery. All comments should include the docket number for this rulemaking: EPA-HQ-OW-2025-0322.

The Agencies will also host two hybrid public meetings. Once finalized, the details for those meetings should be on EPA’s page for the rulemaking and/or EPA’s page for public outreach.