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 non-anomalous events such as low tide or a regularly occurring dry spell. The agencies note that the phrase “a single period” is intended to convey that the interruption of flow can only occur once in any given year, up to 30 consecutive days. In other words, “[w]hen flow is interrupted for more than a single period in any given year, and the interruptions are non-anomalous and ordinary for that water body, the agencies would consider this to be an ephemeral or intermittent feature even if each period of interruption does not amount to 30 consecutive days.”
In turn, the SNPRM defines “perennial” as “having standing or continuously flowing water every day of the year during ordinary conditions.” The agencies are also seeking comment on whether they should define “perennial” consistent with the first Trump Administration’s 2020 Navigable Waters Protection Rule to mean “surface water flowing continuously year-round.”
Definition of “Continuous Surface Connection”
The SNPRM defines “continuous surface connection” as meaning “perennial surface water in a wetland that is continuously connected with the surface water in the jurisdictional water such that it is difficult to determine where the jurisdictional water ends and the wetland begins.” There may be temporary interruptions in the surface water connection if they occur as a result of anomalous events such as drought or a dry spell, or if they last for no more than a single period of up to 30 consecutive days in any given year as a result of non-anomalous events such as low tide or a regularly occurring dry spell. Of note, “[o]nly the portion of the wetland that is indistinguishably part of the jurisdictional water would be itself jurisdictional.” The SNPRM states that the agencies used the term “perennial” in the definition of “continuous surface connection” for the sake of consistency with the supplemental proposed definition of “relatively permanent.”
In sum, the SNPRM aims to provide regulatory certainty for landowners by responding to comments that requested a bright line approach for determining which water bodies constitute WOTUS, in contrast to the previously proposed “wet season” test that was criticized for potential challenges associated with its implementation. In doing so, the SNPRM “narrow[s] the scope of waters that are jurisdictional” under the CWA.
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