"Waters of the United States" Once Again in Flux

The ephemeral meaning of what bodies of water qualify as “Waters of the United States” (WOTUS) is once again changing, spurring a renewed focus on state programs. On 17 November 2025, the Environmental Protection Agency (EPA) and the US Army Corps of Engineers (USACE) announced a proposed rule redefining WOTUS under the federal Clean Water Act (CWA) in the newest campaign in the prolonged legal war over the term’s definition.¹

WOTUS is a crucial concept that defines the bodies of water subject to regulation under the CWA. Among other things, it determines when developers or landowners must obtain federal CWA permits for actions that affect wetlands and waters. The inclusion (or not) of an area as WOTUS determines when American industry, farmers, states, and landowners are required to seek CWA permits for activities such as dredging, filling, or discharging that may impact such waters. Changes to WOTUS that may reduce the scope of federal coverage will place greater emphasis on corresponding state regulations, which vary significantly concerning how closely they follow the federal regulations and, in some cases, provide distinct grounds for state water regulation.

The Sackett decision cemented a narrow interpretation of WOTUS, and the final rule must conform with that framework. Still, ambiguities will remain, particularly in the definition and application of “relatively permanent” waters and wetlands with a “continuous surface connection” to such waters. Public comments on the proposed rule close on 5 January 2026.

Proposed Rule Highlights

The proposed rule is the agencies’ latest attempt to align the definition of WOTUS with the US Supreme Court’s 2023 decision in Sackett v. EPA.² The Sackett decision significantly narrowed the scope WOTUS, holding that federal CWA jurisdiction reaches only “relatively permanent waters” (e.g., streams, river, lakes) connected to traditional navigable waters and wetlands with a “continuous surface connection” to such waters.³

A key feature of the proposed rule is a new limiting concept of “wet season,” applicable to the proposed rule’s definitions of “relatively permanent” and “continuous surface connection.”⁴ The proposed rule requires that during the “wet season” surface hydrology must “be continuous,” otherwise the CWA does not apply.⁵ The preamble to the proposed rule describes the agencies’ interpretation of “wet season,” but the proposed rule itself does not define the term. 

The rule also removes “interstate waters” as an independent basis for CWA jurisdiction. Interstate waters must fall within the enumerated list of WOTUS (e.g., “relatively permanent, standing or continuously flowing bodies of water” (such as streams, oceans, rivers, and lakes) and wetlands that are connected and indistinguishable from such water bodies) to be covered under the CWA.

It also defines numerous terms such as “relatively permanent,”⁶ “tributary,”⁷ “continuous surface connection,”⁸ “excluded ditches,”⁹ excluded “prior converted cropland,”¹⁰ and excluded “waste treatment systems.”¹¹

Although the rule attempts to add clarity about what kind of wetlands will be covered, the undefined term “wet season” will likely lead to more questions, challenges, and disparity in application between states. Ultimately, as federal coverage ebbs and flows, it will likely fall to the states to determine the level of protection granted to their waters. 

Some States Fill the Gap, Others Roll Back Regulations

Many states rely on the CWA and its regulations as their only form of wetland protection for state waters. Others, such as California, Pennsylvania, Washington, and Virginia already have comprehensive regulatory programs. States have also responded to Sackett and the instability of the WOTUS rule by changing their laws: New Mexico and Colorado have responded by expanding protections and programs, while states such as Tennessee have rolled back their laws.

Source: K&L Gates LLP

States Already Protecting Waters Beyond the Scope of CWA Jurisdiction

Many states already have comprehensive water protection and permitting schemes that apply to all waters within the state, including and beyond those covered by federal definitions.¹² For instance, Pennsylvania’s “Clean Streams Law” extends protections to all “waters of the Commonwealth,”¹³ and its Dam Safety and Encroachments Act¹⁴ continues current wetland protection standards and permitting requirements without regard to whether wetlands qualify as WOTUS.

In Virginia, the State Water Control Law has implemented requirements beyond the CWA since 2000 with the goal of protecting and restoring the quality of Virginia’s waters. The law requires permits for actions affecting state waters and covers pollution control, water conservation, and management, with penalties for violations.¹⁵ Virginia defines “state waters” as “all water, on the surface and under the ground, wholly or partially within or bordering the Commonwealth or within its jurisdiction, including wetlands.”¹⁶ Where wetlands are defined as “those areas that are inundated or saturated by surface or groundwater at a frequency and duration sufficient to support, and that under normal circumstances do support, a prevalence of vegetation typically adapted for life in saturated soil conditions.”¹⁷

Similarly, in California, “waters of the state” are defined broadly as “any surface water or groundwater, including saline waters, within the boundaries of the state.”¹⁸ Both waters of the state and wetlands are protected and regulated under the Porter-Cologne Water Quality Control Act by the State Water Resources Control Board and Regional Water Quality Control Boards, responsible for water quality protection and permitting activities that can affect water quality. The California Department of Fish and Wildlife is responsible for permitting streambed alterations of state waters. 

States Expanding Protections

Southwestern states were some of the most severely affected by Sackett; according to the New Mexico Legislature, approximately 90–95% of “waters” in the state lost protections, prompting the legislature to pass Senate Bills 21 and 22.¹⁹ The bills expand the New Mexico Water Quality Act to protect surface waters no longer covered by federal law. They also give New Mexico authority to seek the EPA’s approval to become the 48th state to gain authorization for surface water permitting,²⁰ and address polluted groundwater that falls outside federal Superfund program jurisdiction.

Similarly affected, Colorado is also expanding state regulations to address gaps left by Sackett. The state legislature directed the Water Quality Control Commission to establish dredge-and-fill permitting and mitigation rules by 31 December 2025 to protect state waters not otherwise protected by federal law. The outcome will be Regulation No. 87, which is expected to be finalized by 31 December 2025.

The California Legislature is also considering additional regulations to further protect California state waters to address a perceived rollback in protections due to the Sackett decision and Trump administration policies.²¹ The proposed regulations would explicitly extend protections to state waters no longer covered under federal law.

States Rolling Back Protections 

Tennessee has a robust state program but changed its wetlands protections during its 2025 legislative session in response to Sackett.²² These amendments to the Tennessee Water Quality Control Act establish new categories of wetlands with varying regulatory triggers for each. The thresholds for needing a state permit for altering isolated wetlands have been changed so that some isolated wetlands can be altered with no regulatory oversight as long as there is no water quality impact, and the trigger for needing a state permit for altering isolated wetlands has been limited.

conclusion

Comments on the proposed WOTUS rule are being accepted until 5 January 2026. The Final Rule will take effect 60 days after it is published in the Federal Register. The EPA and USACE will also hold two hybrid public meetings during the comment period. Information on the public meetings can be found here.