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Federal Clean Water Act jurisdiction may be about to get considerably narrower. On September 4, 2026, the U.S. Environmental Protection Agency (EPA) and the U.S. Army Corps of Engineers (Corps) announced a supplemental notice of proposed rulemaking that would limit federal authority over streams and wetlands to those containing water year-round—a “perennial” standard that would go beyond even what the Supreme Court required in Sackett v. EPA, 598 U.S. 651 (2023). The supplemental notice offers two options for revising the definition of “waters of the United States” (WOTUS) under the Clean Water Act (CWA): One would define “relatively permanent” waters as perennial, and the other would require perennial surface water to establish a wetland’s continuous surface connection to a jurisdictional water. If adopted, either option would substantially reduce the number of streams, wetlands and other water features subject to federal permitting, with the sharpest effects in arid and semi-arid regions where rainfall patterns leave many waterways dry for portions of the year.
If adopted in the final rule, these approaches would replace the wet season standards in the agencies’ November 2025 proposal, which drew criticism from commenters who argued the wet season concept was too vague to apply consistently across the nation’s diverse climates. For now, however, both sets of options remain under consideration, and the agencies have not indicated which approach they will adopt.
The supplemental notice was published in the Federal Register on September 9, 2026, opening a 30-day comment period that closes on October 9, 2026. The notice addresses only the proposed perennial definitions and does not reopen or withdraw the other changes included in the November 2025 proposal, which remain pending.
The Changing Course of WOTUS
Few questions in environmental law have proven as perennial as the reach of the CWA itself. For nearly five decades, the definition of “waters of the United States,” or WOTUS, has followed a winding course through Supreme Court decisions, executive orders, rulemakings and legal challenges, each promising to settle the question and none succeeding for long. The current proposal represents the latest attempt to chart a definitive channel, but the regulatory currents show no sign of slowing.
The CWA generally prohibits the discharge of pollutants to WOTUS. 33 U.S.C. §§ 1311(a), 1362(7). Because the statute does not define WOTUS further, the extent of federal jurisdiction under the CWA has been disputed for decades, producing a series of Supreme Court decisions, agency rules and lower court challenges.
The Supreme Court first upheld jurisdiction over wetlands that directly abutted a navigable waterway in United States v. Riverside Bayview Homes, Inc., 474 U.S. 121 (1985), and later rejected jurisdiction over isolated, intrastate ponds in Solid Waste Agency of Northern Cook County v. U.S. Army Corps of Engineers, 531 U.S. 159 (2001). The Court revisited the issue in Rapanos v. United States, 547 U.S. 715 (2006), but produced no majority opinion. Justice Scalia’s plurality concluded that the CWA covers only “relatively permanent” waters and wetlands with a continuous surface connection to those waters; Justice Kennedy’s concurrence proposed a broader “significant nexus” standard, under which wetlands were jurisdictional if they significantly affected the integrity of a traditionally navigable water.
Because Rapanos produced no majority, EPA and the Corps applied both tests through joint guidance (2007, revised 2008) and later incorporated the significant nexus standard into the 2015 Clean Water Rule, though litigation prevented it from taking full effect. After a 2017 executive order directing reconsideration, the agencies repealed the 2015 rule and replaced it with the 2020 Navigable Waters Protection Rule, which abandoned the significant nexus test. Federal courts vacated the 2020 rule in 2021, and the agencies returned to the earlier framework while preparing the January 2023 Revised Definition, which again allowed jurisdiction under either test and took effect on March 20, 2023.
Approximately two months later, the Supreme Court decided Sackett v. EPA, 598 U.S. 651 (2023). All nine Justices agreed that the wetlands on the Sacketts’ property were not covered by the CWA, and five joined Justice Alito’s opinion rejecting the significant nexus standard in favor of the Rapanos plurality’s framework. Under Sackett, the CWA reaches “relatively permanent, standing, or continuously flowing bodies of water” and wetlands with a “continuous surface connection” that makes them “practically indistinguishable” from those waters. Critically, the Court did not define “relatively permanent” with precision, leaving open the question that this supplemental notice now seeks to answer.
The agencies responded to Sackett in September 2023 by removing the significant nexus standard from their existing rule. In March 2025, they issued guidance interpreting a continuous surface connection to require direct abutment and solicited recommendations through public listening sessions. Those efforts produced the November 2025 proposal, which would define “relatively permanent” waters as those with flow throughout the year or at least during the wet season. The agencies received approximately 220,000 comments, many questioning whether the wet season standard was consistent with Sackett or could be applied uniformly across the country’s varied climates and geographies.
The September 2026 supplemental notice responds to those concerns by offering two new options built on a single, more restrictive concept: perennial water. By equating “relatively permanent” with “perennial,” the proposal would adopt a narrower interpretation of Sackett than the Court itself required, effectively drawing the jurisdictional line at year-round flow rather than leaving room for waters that are seasonal but recurrent.
Two Ways to Define Perennial
Both supplemental options turn on a new definition of “perennial”: standing or continuously flowing water every day of the year during ordinary conditions. The agencies also request comment on an alternative formulation drawn from the 2020 rule, which referred more narrowly to surface water flowing continuously throughout the year.
The first option would use the perennial concept to determine which waters are “relatively permanent.” Tributaries, lakes and ponds generally would qualify for federal jurisdiction only if they contain water year-round. The second option would incorporate the same concept into the wetlands test: A wetland would have a “continuous surface connection” only where perennial surface water in the wetland remains continuously connected to surface water in a jurisdictional water, making it difficult to determine where the water ends and the wetland begins. Even then, only the portion of the wetland that is indistinguishably part of the jurisdictional water would be covered. Both options are designed, in part, to address the geographic variability in rainfall patterns and wet seasons that made the November 2025 proposal difficult to apply across different regions of the country. Notably, by requiring a continuous surface water connection, the supplemental options go further than Sackett, which spoke of a “continuous surface connection” without specifying that the connection must consist of surface water. The agencies cite Rapanos as support for this reading, but the distinction could prove significant for wetlands that maintain a physical connection to jurisdictional waters through saturated soils rather than standing surface water.
Although both options begin with a requirement for water throughout the year, they would allow limited interruptions. An ordinary event, such as low tide or a regularly occurring dry spell, could interrupt standing or flowing water once for up to 30 consecutive days in a given year without ending jurisdiction. Importantly, the agencies acknowledge that the 30-day threshold is not based on a specific, nationally applicable scientific standard; rather, they selected roughly one month as a bright-line measure intended to be predictable, transparent and easier for landowners and regulators to administer. Multiple ordinary interruptions would fall outside the exception, even if each lasted fewer than 30 days. The agencies request comment on whether a different numerical threshold would be more consistent with Sackett and the plurality opinion in Rapanos.
Anomalous conditions, such as drought or an unusual dry spell, would be treated differently. The proposed regulatory text does not impose the same 30-day limit on those events. The preamble contemplates treating only extreme (D3) and exceptional (D4) droughts—as classified on the U.S. Drought Monitor—as anomalous. Drought conditions lasting more than five consecutive years, however, would no longer be treated as anomalous; the agencies would treat such prolonged conditions as the “new normal,” ending jurisdictional coverage. This approach remains under consideration and is not part of the proposed regulatory text.
The agencies separately request comment on removing “adjacent” and “abutting” from the wetlands provisions. Under that approach, jurisdiction would extend only to the portion of a wetland that is indistinguishably part of a traditionally navigable water or territorial sea, a jurisdictional impoundment, or a tributary that satisfies the relatively permanent standard. The analysis would therefore focus directly on whether the wetland’s surface water connection makes it indistinguishable from the jurisdictional water, rather than applying a separate adjacency inquiry. This alternative appears only in the preamble and is not included in the proposed regulatory text at the end of the notice.
Importantly, the supplemental notice does not address the other changes included in the November 2025 proposal, and the agencies have not withdrawn or modified those provisions. This means that the proposed deletion of interstate waters as an independent jurisdictional category, removal of “intrastate” from the category covering certain lakes and ponds, revisions to the exclusions for waste treatment systems, prior converted cropland, and certain ditches, and the addition of a groundwater exclusion all remain on the table and could be adopted in the final rule alongside whichever WOTUS definition the agencies select. The notice likewise makes no further changes to the proposed definitions of “ditch,” “prior converted cropland,” “tributary” or “waste treatment system.”
On the Ground: What a Narrower Definition Would Mean
EPA and the Corps acknowledge that the two supplemental options would narrow federal CWA jurisdiction compared with the regulatory regimes now in effect. There is a practical logic to the approach: Determining which waters qualify as WOTUS has long been complicated by hydrologically nuanced definitions that proved difficult to apply consistently in the field, and a bright-line perennial standard could offer greater predictability for regulators and regulated parties alike. But the scope of what falls outside that line is considerable. The perennial standard is designed to provide a more uniform framework across diverse climates and geographies, but its effect would fall unevenly. Most intermittent streams would not satisfy the standard, with the greatest impact in the arid and semi-arid West, where many water features depend on seasonal rainfall and snowmelt rather than year-round flow. The agencies similarly expect that most wetlands currently covered as adjacent wetlands would not meet the proposed connection test because they do not contain perennial surface water.
The agencies have not estimated how many wetland acres or stream miles would fall outside federal jurisdiction, explaining that available datasets cannot reliably establish the current jurisdictional baseline or model the proposed standards. They nevertheless expect Section 404 to experience the greatest change, with fewer permits required for discharges of dredged or fill material and less compensatory mitigation. According to the agencies, those changes would produce both avoided compliance costs and forgone environmental benefits from avoidance, minimization and compensatory mitigation. For industries operating in or near waterways—including energy, mining, agriculture, transportation and real estate development—the practical implications could be significant, potentially eliminating federal permitting requirements for projects affecting intermittent streams and seasonal wetlands. A narrower WOTUS definition would also affect other CWA programs, including Section 303 water quality standards, Section 401 certifications, Section 402 discharge permits, and Section 311 spill prevention requirements.
A water excluded from WOTUS would no longer be subject to federal CWA jurisdiction on that basis. The agencies note in the preamble that state, Tribal and local requirements could still apply, and coverage would vary by jurisdiction. Some states may respond by expanding their own regulatory programs over intrastate waters. As a practical matter, however, the extent of that regulatory backstop remains uncertain—particularly given that EPA has separately proposed revisions to the Clean Water Act Section 401 certification process that could limit states’ ability to impose conditions on federally permitted projects affecting water quality. If both initiatives move forward, the combined effect would be a narrowing of both federal jurisdiction and certain state permitting authorities.
Navigating the Waters Ahead
For now, regulated parties must continue to navigate two jurisdictional regimes. The split results from preliminary injunctions entered in litigation challenging the January 2023 rule. One federal court barred the agencies from implementing that rule in Texas and Idaho, while another barred implementation in 24 additional states. In those 26 states, EPA and the Corps apply the pre-2015 regulations and guidance as limited by Sackett: They no longer use the significant nexus test and generally treat tributaries as jurisdictional only if they are relatively permanent, and wetlands only if they abut or touch a jurisdictional water. In the remaining 24 states, the District of Columbia, and the U.S. territories, the agencies apply the amended 2023 rule, which incorporates Sackett’s standards for relatively permanent waters and wetlands with a continuous surface connection.
Comments on the supplemental notice are due October 9, 2026. The agencies seek input on the perennial definitions, the proposed 30-day threshold for ordinary interruptions, the treatment of drought and dry spells, the tools and data that could be used to apply these standards in the field, and whether “adjacent” and “abutting” should continue to play a role in wetland jurisdictional determinations. The agencies also request comment on any reliance interests the supplemental options may affect. Comments may be submitted through Regulations.gov under Docket No. EPA-HQ-OW-2025-0322. Comments previously submitted on the November 2025 proposal need not be resubmitted and will remain part of the administrative record.
Pillsbury’s Environmental & Natural Resources team will continue to monitor this rulemaking and its intersection with related regulatory developments. Whether you are evaluating the jurisdictional status of a specific site, assessing how the proposed perennial standard may affect ongoing or planned projects, or preparing comments for the October 9 deadline, our team is ready to assist. We regularly advise clients across sectors on CWA jurisdiction, permitting strategy, and compliance. Please contact the authors to discuss how these proposed changes may affect your operations or comment submissions.
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