Proposed ‘Waters of the United States’ Rule Seeks to Clarify and Limit Clean Water Act Jurisdiction

The recently proposed rule aims to align the definition of WOTUS with the US Supreme Court’s seminal decision in Sackett v. EPA in a manner that limits waters subject to federal regulation.

On November 20, 2025, the Environmental Protection Agency (EPA) and the Army Corps of Engineers (Corps) published a Proposed Rule that once again revises the regulatory definition of “Waters of the United States” (WOTUS) under the Clean Water Act (CWA or Act). The Proposed Rule, which would revise the “Conforming Rule” the Biden administration adopted after the US Supreme Court’s 2023 decision in Sackett v. EPA, seeks to (1) define key phrases articulated by the Court in its seminal Sackett decision, (2) further define certain regulatory exemptions to the waters covered by the Act, and (3) implement additional conforming changes.

It does so to “fully implement the direction provided by [the Court in Sackett],” to provide clarity to the regulated community, and to shift further responsibility to states and tribes to manage local water resources. However, like every effort to define the scope of WOTUS, it leaves some questions unanswered and will undoubtedly be the subject of litigation.

BACKGROUND

The CWA covers all “navigable waters,” which it defines only as “the waters of the United States, including the territorial seas.” This ambiguous definition of those waters covered by the CWA has long fueled an ever-shifting litigation and regulatory landscape as to the extent of the federal government’s reach in regulating the nation’s waters, resulting in four separate Supreme Court opinions and numerous sets of regulations from EPA and the Corps, grappling with the question of what non-traditional navigable waters constitute “waters of the United States.”

In 2023, the Supreme Court sought to resolve this question, holding that “waters of the United States” include only those relatively permanent, standing, or continuously flowing bodies of water forming geographic[al] features that are described in ordinary parlance as “streams, oceans, rivers, and lakes” and “those wetlands with a continuous surface connection to bodies that are ‘waters of the United States’ in their own right.” 598 U.S. ___, Slip Op. at 14, 27 (2023).

Following the Sackett decision, the Biden EPA promulgated a new Conforming Rule without notice-and-comment that it stated was intended to implement the Sackett decision. Many in the regulated community criticized the Conforming Rule as failing to fully implement the Sackett decision. The Proposed Rule seeks to do so and proposes additional revisions to clarify and limit those waters covered by the CWA.

KEY DEFINITIONAL CHANGES

The Proposed Rule defines two key phrases from the Supreme Court’s decision in Sackett—“continuous surface connection” and “relatively permanent”—and further defines “tributaries” to clarify that the requirement of relatively permanent flow extends to tributaries as well as wetlands, which were the focus of the Supreme Court’s decision in Sackett.

• Relatively Permanent: Under the Proposed Rule, “relatively permanent” means “standing or continuously flowing bodies of surface water that are standing or continuously flowing year-round or at least during the wet season.” This definition applies to tributaries, adjacent wetlands, as well as lakes and ponds. The “wet season” language, which imposes a temporal requirement to the jurisdictional test, is variably defined according to region and ecotype and proposes the use of existing agency tools and to define the wet season based on rates of precipitation versus evaporation in a water body. To be considered “relatively permanent,” water must flow or stand throughout the wet season. Intermittent flow during the wet season, even with consistent flow outside of the wet season, forecloses a water body from the “relatively permanent” definition.
• Continuous surface connection: Under the Proposed Rule, a continuous surface connection exists if there is “surface water at least during the wet season and abutting (i.e., touching) a jurisdictional water.” This language calls for a two-pronged test: abutment of a jurisdictional water and presence of surface water during the wet season. According to the EPA, this limits the scope of jurisdictional wetlands to only those portions that have surface water that abuts or touches a jurisdictional water during the wet season.
• Tributaries: The Proposed Rule also redefines tributaries as “bod[ies] of water with relatively permanent flow, and a bed and bank, that connects to a downstream traditional navigable water or the territorial seas, either directly or through one or more waters or features that convey relatively permanent flow.” The tributary must be connected to a downstream jurisdictional water by a feature that conveys relatively permanent flow, but such connection can be non-jurisdictional, and may include man-made streams, ditches, canals, and other man-made or man-altered connections.

CHANGES TO EXEMPTIONS

Under current regulations, there are eight exemptions to the definition of WOTUS: (1) waste treatment systems, including those designed to meet CWA requirements, (2) prior converted cropland, (3) ditches excavated wholly in and draining only dry land with no relatively permanent flow, (4) artificially irrigated areas, (5) artificial lakes or ponds created by excavating or diking dry land to collect and retain water, (6) artificial reflecting pools or swimming pools or other small ornamental, (7) waterfilled depressions created in dry land incidental to construction activity, and (8) swales and erosional features with low volume or intermittent flow.

The Proposed Rule further defines three exemptions for waste treatment systems, prior converted cropland, and ditches, and provides an additional exclusion related to groundwater:

• Waste water systems: Under the Proposed Rule, the definition of “waste treatment systems” is expanded to include “all components of a waste treatment system,” including “lagoons and treatment ponds (such as settling or cooling ponds), designed to either convey or retain, concentrate, settle, reduce, or remove pollutants, either actively or passively, from wastewater prior to discharge (or eliminating any such discharge).”
• Prior Converted Cropland: The Proposed Rule specifies that the prior converted cropland exclusion does not apply to abandoned cropland or cropland that is not used for agricultural purposes at least once in the five years immediately preceding the determination. Agricultural uses can include various conservation uses, and federal field staff may consult private or public sources if the proposed list of agricultural uses is ambiguous. If the abandoned cropland is converted back to wetlands, it can only be considered jurisdictional if the resulting wetland satisfies the jurisdictional test.
• Ditches: The Proposed Rule clarifies that non-navigable ditches constructed or excavated “entirely in dry land” and not carrying a relatively permanent flow are not jurisdictional waters. However, ditches that connect to or relocate jurisdictional tributaries maintain their status if the tributary also continues to meet the regulatory definition of a jurisdictional tributary.
• New Groundwater Exception: The Proposed Rule states that groundwater, which is by nature not navigable, does not qualify as jurisdictional waters. However, subsurface groundwater that emerges and becomes baseflow in a relatively permanent stream continues to be subject to federal jurisdiction if it otherwise meets the requirements of a WOTUS.

OTHER REVISIONS

Interstate Waters

The Proposed Rule removes “interstate waters” from the list of jurisdictional waters to clarify that a water body that crosses state boundaries but otherwise does not qualify as a WOTUS is not covered by the CWA simply because it crosses a state line.

Mosaic and Permafrost Wetlands

Currently, broad wetlands possessing various hydrologically connected wetland segments constitute a single wetland. Under the Proposed Rule, mosaic wetlands are restricted to the individual segments. The EPA and the Army Corps are also mulling the adoption of a definition of a wetland that excludes certain permafrost wetlands.

IMPLICATIONS

The Proposed Rule is intended to provide further clarity and ease certain regulatory and compliance burdens for projects impacting jurisdictional waters, including projects requiring Section 404 permits and 401 water quality certifications under the Clean Water Act. At the same time, its impact is likely to be incremental when compared to the significant regulatory changes that were already necessitated by the Supreme Court’s Sackett decision.

And, as with all attempts to define Waters of the United States, areas of uncertainty remain due to the inherent difficulty of providing a single regulatory definition that is applicable to infinitely varied and ever-changing bodies of water across the country. As just one example, the proposed rule specifies that a continuous surface connection must be present “at least during the wet season,” and it in turn provides a definition of “wet season.” But precisely how one determines the beginning and ending of the “wet season” is a complex question in practice that will vary in different locations and could even change over time. Further, like other WOTUS rules, the Proposed Rule is almost certain to be subject to legal challenges when it is finalized. Interested stakeholders who are likely to challenge a final rule include environmental groups, other public interest non-governmental organizations, and state attorneys general.

The Proposed Rule is open to comments until January 5, 2026. Morgan Lewis partner Duke McCall provides additional insights on the Proposed Rule in the Law360 article Trump Admin May Be Overpromising WOTUS Clarity.

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