Clean Water Act regulatory update: Revised definition of "Waters of the United States"
In response to the U.S. Supreme Court’s Sackett v. EPA decision and subsequent regulatory changes, the U.S. Environmental Protection Agency (EPA) and U.S. Army Corps of Engineers (USACE) published a proposed revision to the definition of “Waters of the United States” (WOTUS) on November 20, 2025. The proposal builds on prior updates by further narrowing federal jurisdiction under the Clean Water Act and introducing new definitions intended to clarify how jurisdictional waters are identified and regulated.
For most of the years between the Rapanos v. United States ruling in 2006 and the Sackett decision in 2023, federal jurisdiction relied on two tests: whether a feature had relatively permanent standing or flowing water, or whether it had a significant nexus to downstream waters of the United States. Meeting either test was sufficient to establish federal jurisdiction. Under the proposed rule, jurisdiction would continue to rely on a single test—the presence of relatively permanent waters—with the significant nexus standard fully removed.
Key proposed updates to the WOTUS definition
The proposed rule introduces a formal definition of relatively permanent waters, describing surface waters that are standing or continuously flowing year-round or at least throughout the wet season. The agencies describe this approach as a “bright line” test intended to distinguish jurisdictional from non‑jurisdictional features more clearly. Waters that flow only in response to precipitation events, commonly referred to as “ephemeral,” are not relatively permanent and would not be considered jurisdictional.
The proposal also further refines what it means for wetlands to be adjacent to jurisdictional waters by defining continuous surface connection, the key requirement for adjacency, as requiring a wetland to be inundated, or surface water above ground level, throughout the wet season and direct abutment to a jurisdictional water. Wetlands must be “adjacent” to waters of the United States to be federally jurisdictional under the Clean Water Act. Unlike prior approaches, this change could result in only portions of a previously delineated wetland being considered waters of the United States, reducing the extent of federal regulation over larger wetland complexes.
Additional proposed changes include updates to the definitions of tributaries and ditches, revisions to the treatment of prior converted cropland, clarification that groundwater is excluded from WOTUS, and removal of interstate waters as a standalone basis for asserting federal jurisdiction. While many of these provisions are consistent with current implementation, together they reinforce a narrower and more geographically variable scope of federal oversight.
What this means for permitting and compliance
Overall, these changes to the definition of WOTUS represent a reduction in federal jurisdiction over aquatic resources. This is especially true in drier portions of the country, where many water features may not support surface flows throughout an entire wet season. As a result, fewer projects may require federal permits for impacts to WOTUS, such as dredge and fill permits under Section 404 of the Clean Water Act, and mitigation obligations could decrease for some sites.
At the same time, the proposed definitions may increase the level of effort required during project planning. Determining whether a feature meets the relatively permanent standard or whether a wetland maintains surface water throughout the wet season may require additional analysis, documentation, or field investigation—particularly for features that fall near jurisdictional thresholds.
Broader regulatory implications
It is important to note that reductions in federal jurisdiction can have implications beyond aquatic resource permitting. Historically, many projects have relied on Section 404 permitting as a federal nexus to access more streamlined consultation processes under other federal laws, including the Endangered Species Act and the National Historic Preservation Act. Where a federal permit is no longer required, project sponsors may need to pursue alternative compliance pathways that can affect project timelines and costs.
States will also play a critical role under the proposed rule. Some states have water resource protection programs that fill part or all of any gap left by reduced federal jurisdiction, while others may revise programs that have traditionally been tied to USACE permitting.
Looking ahead
The public comment period for the proposed rule closed on January 5, 2026. EPA and USACE are now reviewing comments and developing a final rule and implementation guidance. Once finalized, the rule is expected to significantly influence how aquatic resources are assessed and regulated across the country.
Early planning, strong baseline data, and a clear permitting strategy will remain essential tools for project leaders navigating ongoing changes to the definition.
Our environmental experts break down the proposed changes and help you understand what to expect when the rule is finalized in this on-demand webinar.