On September 9, 2026, the Environmental Protection Agency (“EPA”) released a proposed rule to supplement and seek additional public comment on certain aspects on an earlier proposal to redefine the Clean Water Act (“CWA”) term “waters of the United States,” (“WOTUS”). EPA issued its latest proposed WOTUS definition on November 20, 2025, but has yet to finalize the rule. By releasing a supplement to that proposed rule, EPA is asking for feedback on whether the final WOTUS definition should more closely reflect the initial November 2025 proposal or the whether the agency should adopt the supplemental proposal instead. Should EPA ultimately issue a final WOTUS definition in line with the supplemental proposal, it would be the narrowest definition of WOTUS that the agency has enforced.

Background: WOTUS & the CWA

Passed by Congress and signed by the President in 1972, the CWA is the leading federal statute regulating water pollution in the United States. The purpose of the CWA is to “restore and maintain the chemical, physical, and biological integrity of the Nation’s waters.” 33 U.S.C. § 1251(a). To facilitate that purpose, the CWA uses permitting programs to limit the amount of pollution discharged into waters and wetlands. Under the National Pollution Discharge Elimination System (“NPDES”) program, anyone who discharges a pollutant from a fixed, concrete source into a “navigable water” without first receiving a permit from EPA will be in violation of the CWA and subject to civil penalties. 33 U.S.C. § 1342. Similarly, the CWA section 404 permitting program prohibits the discharge of “dredged or fill material” into “navigable waters” without first obtaining a permit. 33 U.S.C. § 1344. Importantly, both permitting programs cover activities that occur in “navigable waters.” While the term “navigable waters” is typically recognized as a legal term of art that is used to describe waters that can be used to as highways for commerce, the CWA defines “navigable waters” as “waters of the United States, including the territorial seas.” 33 U.S.C. § 1362(7). However, Congress did not further define the term “waters of the United States” in the text of the CWA itself. Instead, it has been left up to EPA to define the term.

In the decades since the CWA was passed, crafting a durable definition of WOTUS has proven a challenge for EPA and courts alike. The formal regulatory definition of WOTUS has changed numerous times over the years and the United States Supreme Court has weighed in more than once. A full timeline of the WOTUS definition is available here.

Most recently, the definition of WOTUS was updated in 2023 following the Supreme Court’s ruling in Sackett v. EPA, 566 U.S. 120 (2023), issued that same year. In the Sackett case, the Supreme Court was asked to consider the scope of WOTUS and to what extent wetlands should be included in the WOTUS definition. Ultimately, the Court concluded that WOTUS only includes waters that are “relatively permanent, standing or continuously flowing […] described in ordinary parlance as streams, oceans, rivers, and lakes,” and wetlands that are “indistinguishable” from such waters due to a continuous surface connection. The Sackett decision served to narrow the WOTUS definition which had previously been defined to include broader categories of waterbodies and wetlands that “neighbored,” but did not necessarily directly abut, waters considered WOTUS. To learn more about the Sackett ruling, click here.

Following the Supreme Court’s ruling, EPA updated the WOTUS definition to better reflect the Court’s decision. Known as the Conforming Rule, the 2023 update amended the definition of WOTUS to include only the following categories of water bodies:

• Traditional navigable waters which may be used to facilitate interstate or foreign commerce, including all waters subject the ebb and flow of the tide, the territorial seas, and all interstate waters (collectively, “traditional navigable waters”);
• Impoundments of waters otherwise identified as WOTUS;
• Tributaries of traditional navigable waters that are relatively permanent, standing, or continuously flowing;
• Wetlands that share a continuous surface connection with traditional navigable waters or relatively permanent, standing, or continuously flowing tributaries of such waters;
• Intrastate lakes and ponds that do not fall into any of the above categories, but that are relatively permanent, standing, or continuously flowing bodies of water that share a surface connection with a recognized WOTUS.

A full breakdown of the Conforming Rule is available here.

As of September 2026, the 2023 Conforming Rule remains the current legal definition of WOTUS. However, in November 2025, EPA proposed a new WOTUS definition with the goal of updating the term to more closely reflect the Supreme Court’s ruling in Sackett. Along with removing some types of waters, such as interstate waters, from the WOTUS definition, the November 2025 proposed rule also advanced for the first time, definitions for the terms “relatively permanent,” “continuous surface connection,” and “tributary.” Importantly, the proposal would define “relatively permanent” waters as though that are “standing or continuously flowing year-round or at least during the wet season” with the wet season described as a predictable and extended period of time when surface water is present in a geographical feature in response to an annual wet season when precipitation is greater than average. It would also define “continuous surface connection” as “having surface water at least during the wet season and abutting (i.e. touching) a jurisdictional water.” Full analysis of the November 2025 proposed rule can be found here.

The November 2025 proposed WOTUS definition was open for public comment through January 5, 2026. While a final rule was initially anticipated some time before the end of the year, EPA has now put forth a supplemental proposed rule seeking additional public input on the new WOTUS definition. Specifically, the supplemental rule proposes revised definitions of “relatively permanent” and “continuous surface connection,” while adding a definition for the term “perennial.” EPA notes that it will continue to consider public comments on both the WOTUS definition originally proposed in November 2025 and the definition as modified by the new supplemental proposal when drafting the final rule.

Supplemental Proposed Rule

In the supplemental WOTUS rule, EPA is proposing to add a definition for the word “perennial” while offering new definitions for the terms “relatively permanent” and “continuous surface connection.” If finalized as proposed, the three revised definitions would narrow the waters and wetlands that fall under CWA jurisdiction.

First, EPA proposing to define the term “perennial” as “having standing or continuously flowing water every day of the year during ordinary conditions.” EPA explains that it would then understand “extraordinary” or “anomalous” conditions as “something that is unusual or caused by unforeseen circumstances or conditions.” In other words, EPA would consider a “perennial” water to be one that has “standing or continuously flowing water” every day unless something unusual or unforeseen causes the water to stop flowing. For example, EPA says a drought would be considered an extraordinary condition that could cause an otherwise perennial water to dry up but not lose its perennial status. Similarly, EPA notes that a water body which experiences a regular annual dry period that does not exceed 30 consecutive days in any given year but contains standing or continuously flowing water for the rest of the year would be considered a perennial water. However, a water that is dry for more than 30 consecutive days in the year would not be considered a perennial water even if it had standing or continuously flowing water during the rest of the year. Additionally, a body of water that experiences regular periods of intermittent flow would likely not be considered “perennial” under this proposed definition. For example, a stream that experiences an annual period where it flows, then dries out for less than 30 days, then flows again, then dries out for less than 30 days before flowing again, would likely not be considered “perennial” because the proposed definition would include only those waters that contain water year-round except for 30 consecutive days.

Next, EPA proposes to define “relatively permanent” waters as “perennial bodies of water” with “perennial” defined as described above. The proposed rule elaborates that a water would not lose its relatively permanent status if “it dries up as the result of anomalous events such as drought or a dry spell.” A water would also not lose relatively permanent status if it “dries up for no more than a single period of up to 30 consecutive days in any given year as a result of non-anomalous events resulting in a temporary interruption such as low tide or a regularly occurring dry spell.” In other words, a water would be classified as “relatively permanent” for the purposes of WOTUS and CWA permitting jurisdiction if it contains relatively permanent water year-round except for a regular dry period of no more than 30 consecutive days. Under this definition, a stream that contains water year-round except for an annual dry period that lasts around 20 days, it would retain its status as relatively permanent. However, a stream that contains water year-round except for an annual dry period that lasts around 40 days, it would not be considered relatively permanent. Similarly, a stream that otherwise contains standing water year-round but experiences an annual period of intermittent flow where water may cease to flow for 10 days, flow again for 10 days, then cease to flow for another 10 days before flowing again, would not be considered relatively permanent because the cessation of flow would not occur over consecutive days.

Importantly, EPA notes that a water would not lose its relatively permanent status due to an extraordinary circumstance such as drought. The United States Drought Monitor uses four levels of drought classification: moderate (D1), severe (D2), extreme (D3), and exceptional (D4). EPA explains that, for purposes of implementing the proposed rule, it would consider only extreme (D3) and exceptional (D4) droughts as anomalous drought conditions that could temporarily interrupt a water’s perennial flow without the water losing relatively permanent status. However, EPA notes that if the drought extends continuously for more than five years, the drought would no longer be considered anomalous and the water would lose its relatively permanent status. If EPA implements the definition of “relatively permanent” as described in the supplemental proposed rule, a water could lose relatively permanent status and thus no longer be subject to CWA permitting jurisdiction if it experiences a moderate (D1) or severe (D2) drought that causes the water to stop flowing for more than 30 days. However, if the water experiences an extreme (D3) or exceptional (D4) drought that causes water to stop flowing for more than 30 days, that water would not lose relatively permanent status unless the drought extends for longer than five years. EPA does not discuss whether a water that loses relatively permanent status due to a drought could later regain that status when the drought ends and the water once again meets the definition of “perennial” or “relatively permanent.”

Finally, EPA is proposing to define “continuous surface connection” as meaning “perennial surface water in a wetland that is continuously connected with the surface water in [a water otherwise recognized as WOTUS] such that it is difficult to determine where the jurisdictional water ends and the wetland begins.” Similar to relatively permanent waters, EPA notes that a wetland with a continuous surface connection to a water recognized as WOTUS would not lose its WOTUS status due to temporary interruptions in the surface water connection as the result of “anomalous events such as a drought or dry spell” so long as the temporary interruption does not last for more than 30 consecutive days in any given year. Should the continuous surface connection between a wetland and a water that falls under WOTUS jurisdiction be disrupted for more than 30 days or for intermittent periods of time, then the wetland would lose WOTUS status and no longer fall under CWA permitting jurisdiction. EPA further notes that only the portion of the wetland that shares a continuous surface water connection with another WOTUS would be considered a WOTUS. The agency does not elaborate on how it will determine which portions of larger wetlands qualify as WOTUS and which do not.

Going Forward

Should the supplemental WOTUS rule be finalized as proposed, it would represent the narrowest definition of WOTUS that EPA has ever enforced. The agency acknowledges that it would mean many waters that are currently considered WOTUS or that would retain WOTUS status under the November 2025 proposed rule would no longer be considered WOTUS. While EPA is unable to say exactly how many waters would fall out of CWA permitting jurisdiction, it notes that the impact would fall more heavily on the Western United States.

A 30-day period of public comment is currently open on the supplemental rule and will run through October 9, 2026. After the comment period closes, EPA will review all comments and ultimately issue a final WOTUS rule. Whether the final rule more closely reflects the November 2025 proposal or the new supplemental proposal, it is likely to face legal challenges.

To view the supplemental proposed WOTUS rule and learn how to submit a comment, click here.

To view the November 2025 proposed WOTUS rule, click here.

To view the text of the CWA, click here.

For more information from EPA on the status of WOTUS, click here.

For more information on the CWA from NALC, click here.