On August 29, 20213, the Environmental Protection Agency (“EPA”) released an updated version of its 2023 rule to define the crucial Clean Water Act (“CWA”) term “waters of the United States,” also known as WOTUS. The term is central to implementation of the CWA because only those water bodies that meet the definition of WOTUS are subject to the CWA’s permitting programs which are one of the primary ways that the CWA works to limit water pollution. In the decades since the CWA was passed, defining WOTUS has proven a challenge for both EPA and the courts. The definition of WOTUS has changed multiple times over the years, with roughly four different rule changes since 2015 alone. This has created confusion and inconsistency for landowners and other parties affected by the CWA.

Earlier this year, EPA released its latest WOTUS definition, known as the 2023 Rule. The new definition attempted to incorporate long-standing provisions of the WOTUS definition together with language from the Supreme Court in an attempt to create a more legally robust rule. However, shortly after the 2023 Rule went into effect, the Supreme Court issued its decision in Sackett v. EPA, No. 21-454 (2023), where the Court was asked to revisit the definition of WOTUS. The Court’s ruling in Sackett invalidated much of the 2023 Rule and required EPA to once again revise the WOTUS definition.

Background: Rapanos, Sackett, and the 2023 Rule

The CWA was signed into law in 1972, becoming the nation’s primary federal statute regulating water pollution. The stated purpose of the CWA is to “restore and maintain the chemical, physical, and biological integrity of the Nation’s waters.” 33 U.S.C. § 1251(a). To fulfill that purpose, the CWA makes it illegal for anyone to discharge any pollutant from a discernable, concrete source into “navigable waters” without receiving a permit from EPA. 33 U.S.C. § 1342. While the traditional legal definition of the term “navigable waters” is understood as those waters that can be used to facilitate interstate or foreign commerce, Congress defined “navigable waters” under the CWA as “waters of the United States, including the territorial seas. 33 U.SC. § 1362(7). However, Congress did not provide any further direction on how to define “waters of the United States,” choosing instead to leave that up to EPA.

Defining WOTUS has proven to be a difficult task, and exactly how to define WOTUS has become a source of controversy, particularly in recent years. Some believe that the scope of WOTUS should be limited to the traditional legal understanding of navigable waters, while others favor a broader rule. Since 2015, EPA has adopted roughly four different WOTUS definitions, each of which has been challenged in court. However, prior to 2015, the regulatory definition of WOTUS had remained largely unchanged in 1986. Under the 1986 definition, six categories of waterbodies fell under the definition of WOTUS, including: (1) waters that could be used in interstate or foreign commerce; (2) all waters that cross state boundaries, otherwise known as interstate waters; (3) all other waters that could affect interstate or foreign commerce if the waters were degraded or destroyed the territorial seas; (4) impoundments of any waters described as a WOTUS; (5) tributaries of any waters described as a WOTUS; (6) or wetlands adjacent to any WOTUS, with “adjacent” defined “adjacent” as “bordering, contiguous or neighboring.” More information on the 1986 rule is available here.

In 2006, the Supreme Court issued the landmark ruling Rapanos v. U.S., 547 U.S. 715 (2006). There, the Supreme Court was asked to consider whether the definition of WOTUS should extend to wetlands that did not directly “abut” or share a surface connection with a body of water identified as a WOTUS. However, the Court failed to reach a majority opinion, instead producing a four-justice plurality opinion authored by Justice Scalia, and a single-justice concurring opinion authored by Justice Kennedy. The plurality opinion found that the definition of WOTUS should be limited to include only those waters that are “relatively permanent, standing, or continuously flowing,” such as rivers, lakes, and streams. Then, only those wetlands that shared a continuous surface water connection with such waters should fall under the WOTUS definition. In contrast, Justice Kennedy concluded that a wetland could be a WOTUS if it shared a “significant nexus” with a water already identified as a WOTUS. According to Justice Kennedy. A significant nexus exists when a wetland “significantly affect[s] the chemical, physical, and biological integrity” of a recognized WOTUS.

After the Rapanos decision was issued, EPA did not immediately update the regulatory definition of WOTUS. Instead, it issued guidance documents instructing its employees to interpret WOTUS so that it included waters and wetlands that would meet either the significant nexus test from Justice Kennedy’s concurrence or the relatively permanent test from the plurality’s opinion. EPA did not update the regulations defining WOTUS until 2015. While the 2015 rule was meant to revise the WOTUS definition to better reflect what the Supreme Court had articulated in Rapanos, many felt that the rule was overly broad and went beyond the scope of EPA’s CWA authority. In 2019, EPA repealed the 2015 rule, and adopted a much narrower definition of WOTUS in 2020. That rule was overturned by a federal judge in 2021, sending EPA back to the drawing board.

The most recent WOTUS definition, the 2023 rule, was specifically intended to return the WOTUS definition to where it was in 1986 while incorporating both tests from Rapanos. The 2023 rule identified five categories of waters that would be recognized as WOTUS: (1) traditional navigable waters that can be used to facilitate interstate and foreign commerce, the territorial seas, and interstate waters including interstate wetlands; (2) impoundments of waters otherwise identified as a WOTUS; (3) tributaries of traditional navigable waters or impoundments that meet either the relatively permanent test or the significant nexus test; (4) wetlands adjacent to any waters that fall into the previous three categories; and (5) interstate waters or wetlands that do not fall into any of the above categories but that satisfy either the relatively permanent test or the significant nexus test. Like the 1986 rule, the 2023 rule defined “adjacent” for adjacent wetlands as “bordering, contiguous, or neighboring.” A more in-depth look at the 2023 rule is available here.

On May 25, roughly two months after the 2023 rule went into effect, the Supreme Court handed down its decision in Sackett v. EPA which appeared to invalidate large portions of the 2023 rule. In Sackett, the Court was asked to reconsider its ruling in Rapanos to formally adopt the plurality’s opinion and overturn the significant nexus test. The Court did exactly that, finding that the use of the word “waters” in “waters of the United States” refers only to relatively permanent, open, flowing bodies of water commonly described as streams, oceans, rivers, and lakes. Then, the Court found that only those wetlands that are “indistinguishable” from such relatively permanent bodies of water due to a continuous surface water connection could be considered WOTUS. Finally, the Court expressly overturned the significant nexus test. For a closer look at the Court’s ruling in Sackett, click here.

After Sackett was issued, EPA announced that it would be revisiting and revising the 2023 rule to bring it into line with the Court’s decision.

The Conforming Rule

EPA released the updated version of its 2023 WOTUS definition on August 29. The updated rule, referred to as the Conforming rule, removes all mentions of the significant nexus test and revises the definition of “adjacent” for adjacent wetlands. According to the Conforming Rule, only the following categories of water bodies will be included in the definition of WOTUS:

  • Traditional navigable waters which are currently used or may be used to facilitate interstate or foreign commerce, including all waters which are subject to the ebb and flow of the tide, the territorial seas, and all interstate waters (collectively, “traditional navigable waters”);
  • Impoundments of waters otherwise defined as WOTUS;
  • Tributaries of traditional navigable waters that are themselves relatively permanent, standing, or continuously flowing;
  • Wetlands that are adjacent to traditional navigable waters, or relatively permeant, standing, or continuously flowing tributaries of such waters;
  • Intrastate lakes and ponds that do not fall into any of the above categories, but that are relatively permanent, standing, or continuously flowing bodies of water that share a surface connection with a recognized WOTUS.

These categories are more limited than the categories included in the 2023 rule. The 2023 rule included tributaries to traditional navigable waters that met either the significant nexus test or the relatively permanent standard. Under the Conforming rule, only tributaries that meet the relatively permanent standard will be considered WOTUS. Similarly, the 2023 rule included intrastate waters (aka, waters located entirely within the boundaries of one state) that either met the significant nexus test, or were relatively permanent waters that shared a surface connection with a traditional navigable water. Under the Conforming rules, only intrastate lakes and ponds that satisfy the relatively permanent test and share a surface connection with a traditional navigable water will be considered WOTUS. The 2023 rule included all interstate wetlands, and wetlands that shared a significant nexus with a traditional navigable water. Under the 2023 rule, only those wetlands that are directly adjacent to a traditional navigable water or a relatively permanent tributary will be included in the WOTUS definition.

The Conforming rule also updated the definition of “adjacent.” Under the 2023 rule, “adjacent” was defined as “bordering, contiguous, or neighboring,” and included “wetlands separated from other waters of the United States by man-made dikes or barriers, natural river berms, beach dunes, and the like[.]” In contrast, the Conforming rule defines “adjacent” as “having a continuous surface connection.”

Finally, in the preamble to the Conforming rule where EPA explains the changes it is making and its reasons for doing so, EPA highlighted language from the Rapanos plurality that helps to guide what waters are considered relatively permanent, standing, or continuously flowing. Specifically, EPA noted that in Rapanos, the plurality found that relatively permanent waters did “not necessarily exclude streams, rivers, or lakes that might dry up in extraordinary circumstances, such as drought,” or “seasonal rivers, which contain continuous flow during some months of the year but no flow during dry months.” In other words, EPA has noted that the plurality in Rapanos did not necessarily intend for the relatively permanent standard to include only those waters that flow year-round. Waters with seasonal flow may still be relatively permanent enough to meet the definition of WOTUS.

Going Forward

At the time of this article’s publication, EPA has only released a pre-publication copy of the Conforming rule. It has not yet been published in the Federal Register. Once the Conforming rule is published in the Federal Register, it will go into immediate effect and become the controlling definition of WOTUS.

In the meantime, there are also three on-going lawsuits filed by different states challenging the 2023 rule. All three lawsuits were paused following the Sackett decision to allow EPA time to revise the WOTUS definition. It is currently unclear whether the parties will choose to dismiss the lawsuits or continue to litigate claims to the revised rule.


To read the pre-publication draft of the Conforming rule, click here.

To read the Supreme Court’s decision in Sackett, click here.

For more resources from EPA on the 2023 WOTUS definition, click here.

For more National Agricultural Law Center resources on the CWA, click here.