EPA And Army Corps Announce Supplemental WOTUS Proposal: Key Updates

On September 9, 2026, EPA and the Army Corps (the agencies) published a supplemental notice of proposed rulemaking (SNPRM) to revise the definition of “waters of the United States” (WOTUS). 91 Fed. Reg. 57284 (Sept. 9, 2026). With this SNPRM, the agencies are supplementing certain components of the NPRM, published on November 20, 2025, by providing alternative regulatory definitions for the terms “relatively permanent” and “continuous surface connection,” and by adding a new definition for the term “perennial.” The agencies are not proposing to supplement other portions of the November 2025 NPRM. 

Definitions of “Relatively Permanent” and “Perennial”

The SNPRM defines “relatively permanent” as “perennial bodies of water,” where a body of water would not lose its relatively permanent status if it dries up as a result of anomalous events such as drought or a dry spell, or 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