Proposed Update to Definition of Waters of the United States

On November 20, 2025, the U.S. Environmental Protection Agency (U.S. EPA) and the U.S. Army Corps of Engineers (USACE) published a proposed rule to update the definition of Waters of the United States (WOTUS). WOTUS is a key definition because it establishes whether or not a waterbody or wetland is under Federal jurisdiction and thus protected under the Clean Water Act (CWA). The CWA gives U.S. EPA and USACE authority to define WOTUS in regulation rather than giving a prescribed definition in statute; therefore, the definition of WOTUS has changed significantly over time.

Why is the Rule Being Updated?

As directed by U.S. EPA Administrator Lee Zeldin, the definition is being revised to align with the U.S. Supreme Court’s 2023 decision in Sackett v. Environmental Protection Agency. In this decision, the Court ruled that the CWA covers only those wetlands with a continuous surface connection to bodies that are “Waters of the United States” in their own right, meaning they are “indistinguishable” from those waters. The ruling limited U.S. EPA’s authority to regulate wetlands that do not meet this criteria.

What are the Key Changes Being Proposed?

Several changes to key definitions are proposed in the update:

• Add the definition of relatively permanent waters: Defined as bodies of water (i.e., tributaries, lakes, and ponds) that are standing or continuously flowing year-round or at least during the wet season. The agencies intend to use the Web-based Water-Budget Interactive Modeling Program (WebWIMP) as a primary source for identifying the wet season at a particular location.
• Reestablish definition of tributary: Only “relatively permanent” tributaries that meet specified criteria are jurisdictional. Features such as channelized non-jurisdictional surface waters, subterranean rivers, culverts, dams, tunnels, or similar artificial features are not included in the definition of tributary.
• Add the definition of continuous surface connection: Jurisdiction under the CWA requires that wetlands abut a jurisdictional water and have a surface water present at least during the wet season. Note that the agencies are not proposing to revise the definition of “adjacent” which means “having a continuous surface connection”.
• Delete Intrastate: Removed as a standalone category; crossing state lines alone no longer confers jurisdiction.
• Reestablish the definition of waste treatment systems: Clarifies the exclusion for waste treatment systems. In general, waste treatment lagoons are excluded while cooling ponds and stormwater treatment features are not.
• Reestablish the definition of prior converted cropland: Clarifies that an exclusion is maintained unless the land is abandoned (i.e., not used for or in support of agricultural purposes in more than five years) and reverts to wetlands. Note that the U.S. Department of Agriculture (USDA) is responsible for making determinations as to whether land is prior converted cropland and the agencies will recognize a USDA determination when making their own determination for purposes of the CWA.
• Reestablish the definition of ditch: Clarifies that ditches constructed or excavated entirely in dry land are excluded. Note that the agencies have proposed the definition of ditch to mean “a constructed or excavated channel used to convey water”.
• Clarify exclusion for groundwater: Groundwater is explicitly excluded from WOTUS. The agencies propose to include an exclusion for groundwater drained through subsurface drainage systems. Note that under the proposed rule, the exclusion would not apply to surface expressions of groundwater, such as where groundwater emerges on the surface and becomes baseflow in relatively permanent streams.

How Does This Impact Me?

Waterbodies under Federal jurisdiction may be subject to certain CWA programs such as the Section 402 National Pollutant Discharge Elimination System (NPDES) permitting program, the Section 404 permitting program for discharges of dredged or fill material, the Section 311 oil spill prevention, preparedness and response program, the Section 303 water quality standards and total maximum daily load (TMDL) programs, and the Section 401 State water quality process.

Although the proposed WOTUS update potentially impacts multiple CWA programs, it is not expected to have much impact on currently permitted dischargers. However, it may reduce the number of total permits issued – for example, the update is estimated to result in an 81% decrease in total wetland acreage subject to federal wetlands protections, which will lead to a decrease in permits and required mitigation under the 404 program. Another interesting consideration is how much flexibility states with differing hydrology will have in using “wet season” data to define what is a “relatively permanent water”.

How Can I submit comments?

A 45-day public comment period opened on November 20, 2025. All comments must be submitted by January 5, 2026. The preferred method of submission is via the Federal eRulemaking Portal or by email to OW-Docket@epa.gov. Both methods should identify Docket ID No. EPA–HQ–OW–2025–0322.

If you need support with CWA compliance in Kentucky and surrounding states, please reach out to William Shane at wshane@all4inc.com or 859-233-0123.