On September 9, 2026, the U.S. Environmental Protection Agency (“EPA”) and U.S. Army Corps of Engineers (“USACE”) issued a supplemental notice of proposed rulemaking (“SNPRM”) proposing additional changes to the regulatory definition of waters of the United States (“WOTUS”). The SNPRM supplements the agencies’ November 20, 2025 proposed WOTUS rule and responds to comments received on that proposal. Most significantly, the SNPRM proposes additional definitions of “relatively permanent” waters and the “continuous surface connection” required for wetlands to be jurisdictional. If finalized, these changes could substantially reduce the number of waters and wetlands subject to federal Clean Water Act (“CWA”) jurisdiction. The agencies will accept comments on the SNPRM until October 9, 2026.

The definition of WOTUS determines the geographic scope of several major CWA regulatory programs, including the Section 404 program governing discharges of dredged or fill material. There has been significant uncertainty regarding how WOTUS is defined and applied over the last eleven years due to five rule revisions and various court decisions, including the U.S. Supreme Court’s decision in Sackett v. EPA in 2023. Sackett significantly altered the federal government’s authority under the CWA by curtailing the definition of WOTUS. A discussion of the limits on federal CWA jurisdiction in the wake of Sackett can be found here. In November 2025, the agencies issued a proposed rule to revise what constitutes a WOTUS, as discussed here. The SNPRM does not replace the November 2025 proposal, but in light of the public comments received, it now seeks feedback on additional proposals for defining “relatively permanent” and “continuous surface connection,” while leaving the other portions of the November proposal, including its proposed changes to exclusions and definitions for ditches, prior converted cropland, tributaries, and waste treatment systems, unchanged.

Relatively Permanent Tributaries

Under the SNPRM’s proposed definition of “relatively permanent,” a water would be subject to CWA jurisdiction as a “relatively permanent” tributary to a WOTUS only if it is perennial, meaning “having standing or continuously flowing water every day of the year during ordinary conditions.” But, a perennial body of water would not lose its relatively permanent status if it dries up as a result of non-anomalous events, such as regularly occurring dry spells. The SNPRM explains that a water would still be “relatively permanent” if ordinary conditions cause it to dry up once for no more than 30 consecutive days in a year, such as during a regularly recurring dry spell—a non-anomalous event. But if a body of water dries up entirely for more than 30 consecutive days as part of a dry season or if flow is interrupted on multiple occasions for more than 30 total days in a year due to a regularly occurring dry spell, the water will not be considered “relatively permanent” and therefore not a WOTUS. The 30-day cutoff is intended to provide “certainty and clarity for landowners.”

Additionally, a perennial body of water would not lose its relatively permanent status and would still be jurisdictional if it dries up as for more than 30 days because of an anomalous event resulting in extraordinary circumstances, such as extreme drought.

Wetlands

In Sackett, the Supreme Court held that wetlands should be considered WOTUS only where they are “as a practical matter indistinguishable from [WOTUS],” which requires a continuous surface connection to a jurisdictional water. Under the previous NPRM, the agencies proposed that adjacent wetlands would be a WOTUS if they had “surface water at least during the wet season and abutting (i.e., touching) a jurisdictional water [WOTUS].” In response to public comments expressing concern with the introduction of the term “wet season,” the SNPRM proposes to instead define jurisdictional wetlands as those that have “perennial surface water” and a “continuous surface connection” to a WOTUS.

Under the SNPRM, a wetland must have perennial surface water that has a continuous surface connection to a WOTUS—meaning that it must maintain standing or continuously flowing water throughout the year except for the non-anomalous events and anomalous events described above. Only the portion of a wetland that is indistinguishable from the jurisdictional WOTUS would itself be jurisdictional. Although the proposed definition turns on year-round flow, the agencies do not expect landowners to continuously monitor a water for an entire year. Instead, they anticipate using multiple sources of information, including remote and field-based indicators, to determine whether the perennial standard is satisfied.

Expected Impacts

If finalized, the SNPRM could significantly reduce the number of streams and wetlands subject to federal jurisdiction under the CWA. This is expected particularly for intermittent streams and wetlands in the western states with arid and semiarid climatic conditions, more of which have historically been regulated as WOTUS than would be jurisdictional under a definition of “relatively permanent” that relied on “wet season.” The agencies expect the greatest programmatic effects in the Section 404 permitting program, including fewer required permits and less compensatory mitigation. Reduced federal jurisdiction does not necessarily mean that a water or wetland is unregulated. States and Tribes may regulate waters beyond the scope of federal CWA jurisdiction. This SNPRM is, in part, based on “recognizing and respecting the primary responsibilities and rights of States to regulate their land and water resources.”

The revised definition of WOTUS has been highly anticipated by project developers and landowners so that they can obtain greater regulatory clarity regarding whether a project is subject to CWA jurisdiction.

This article summarizes aspects of the law and opinions that are solely those of the authors. This article does not constitute legal advice. For legal advice that applies to ‎your situation, you should contact an attorney.