On December 30, 2022, the Environmental Protection Agency  (“EPA”) released its long-awaited rule to redefine the definition of “waters of the United States” (“WOTUS”) under the Clean Water Act (“CWA”). The term is central to the implementation of the CWA because only those waterbodies designated as WOTUS receive CWA protection. The new rules marks the third attempt by EPA to redefine WOTUS since 2015. In a press release issued by EPA, the Agency stated that it hoped the new rule would create a “durable definition” of WOTUS that would reduce uncertainty.


Passed by Congress in 1972, the stated objective 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 achieve this goal, the CWA implements a variety of different programs, including two permitting schemes that prevent the unpermitted discharge of pollutants or dredge or fill material into protected waters. Central to the implementation of the CWA is the term “navigable waters” which the Act uses to establish most of its programs, including its permitting provisions. Only those waters that fall under the definition of “navigable waters” will be subject to CWA protection.

The CWA broadly defines “navigable waters” as “the waters of the United States, including the territorial seas.” 33 U.S.C. § 1362(7). Congress did not include additional language to further define “waters of the United States.” Instead, Congress left it up to EPA to pass regulations that would define the term. Ultimately, this has proved challenging for EPA. The Agency has adopted multiple definitions for WOTUS since the CWA was passed, with the definition being particularly in flux since 2015.

Prior to 2015, the definition of WOTUS had been relatively stable since 1986. Under the 1986 definition, there were roughly seven categories of waterbodies that fell under the definition of WOTUS. That included all waters which have been used or could be used in interstate or foreign commerce; all interstate waters; all other waters that could affect interstate or foreign commerce if the water was degraded or destroyed; the territorial seas; impoundments of any waters described in the rule; tributaries of any waters described in the rule; or wetlands adjacent to any waters described in the rule. Under that rule, some waters very clearly satisfied the definition of WOTUS while others, particularly wetlands, required further assessment. For more information on the 1986 definition, click here.

In 2006, the United States Supreme Court issued a ruling in the landmark case Rapanos v. U.S., 547 U.S. 715 (2006). The case concerned the scope of wetlands jurisdiction under the CWA, specifically asking whether CWA jurisdiction extended to non-navigable wetlands that did not share a continuous surface connection with a navigable water. Ultimately, the Court did not reach a majority conclusion. Instead, Rapanos resulted in a four-justice plurality decision authored by Justice Scalia and an opinion by Justice Kennedy writing for himself. The plurality opinion proposed a strict hardline rule for determining wetland jurisdiction under the CWA. According to the plurality, the word “waters” in “waters of the United States” should apply only to “relatively permanent, standing or continuously flowing bodies of water” such as streams, oceans, rivers and lakes. Only those wetlands which shared a “continuous surface connection” with a relatively permanent body of water would satisfy the definition of WOTUS and fall under CWA jurisdiction.

Justice Kennedy offered a different approach. In his opinion, Justice Kennedy suggested that a wetland should fall under CWA jurisdiction if it shared a “significant nexus” with a water that is already recognized as a WOTUS. A significant nexus would exist if a wetland “significantly affect[s] the chemical, physical, and biological integrity” with a recognized WOTUS. If such a significant nexus exists, the wetland would fall under CWA jurisdiction.

In the years following Rapanos, courts and EPA tended to apply Justice Kennedy’s significant nexus test either on its own or in combination with the plurality’s approach when the issue arose. However, EPA did not formally revise the definition of WOTUS in response to Rapanos until 2015. At that time, EPA adopted the Clean Water Rule which expanded the definition of WOTUS and attempted to clarify which waters were protected. The rule was highly controversial, and multiple lawsuits ultimately prevented it from going into effect in over half the states. When President Trump took office in 2017, he issued an executive order directing EPA to draft new regulations that would repeal the Clean Water Rule and redefine WOTUS. In 2020, EPA adopted the Navigable Waters Protection Rule which once again redefined WOTUS, this time limiting it to four discrete categories of waters. That rule was similarly controversial, and was ultimately overturned by a judge in 2021. For more information on the Navigable Waters Protection Rule, click here and here.

When President Biden took office in 2021, he issued another executive order again directing EPA to review and revise the regulations defining WOTUS. After conducting an initial review, EPA announced that it would carry out a two-part rulemaking to create a new WOTUS definition. During the first part of the rulemaking, EPA repealed the Navigable Waters Protection Rule and returned the WOTUS definition to where it was prior to 2015. During the second part, EPA worked to draft a new WOTUS definition that would build on the pre-2015 definition to establish a durable WOTUS rule. The final rule announced on December 30 is the conclusion of that two-step rulemaking.

What’s In the Rule?

The 2022 WOTUS rule is largely based on the pre-2015 regulations from 1986, and for the first time codifies both the significant nexus and relatively permanent standards proposed in Rapanos. The 2022 rule includes definitions for several other important terms such as “adjacent” and “significant affect,” and codifies a variety of longstanding WOTUS exclusions. The text of the rule is divided into three parts: jurisdictional waters, exclusions, and definitions.

In the 2022 WOTUS rule, EPA identifies five categories of waters that will fall under CWA jurisdiction. Those categories are:

  • Traditional navigable waters that currently are, or were used in the past, or could be used in the future for interstate for foreign commerce, including all waters that are subject to the ebb and flow of the tide; the territorial seas; and interstate waters, including interstate wetlands (collectively, “traditional navigable waters”)
  • Impoundments of waters otherwise identified as a WOTUS, except for impoundments of waters identified under the fifth category of WOTUS (collectively, “impoundments”)
  • Tributaries of traditional navigable waters or impoundments that are either: relatively permanent, standing or continuously flowing bodies of water; or that alone or in combination with similarly situated waters in the region significantly affect the chemical, physical, or biological integrity of traditional navigable waters (collectively, “tributaries”)
  • Wetlands adjacent to any of the following: traditional navigable waters; a relatively permanent, standing or continuously flowing impoundment or tributary; an impoundment or tributary if the wetlands either alone or in combination with similarly situated waters in the region significantly affect the chemical, physical, or biological integrity of a traditional navigable water (collectively, “adjacent wetlands”)
  • Interstate lakes and ponds, streams, or wetlands that do not fall into any of the above categories provided the water is either: relatively permanent, standing or continuously flowing and shares a surface connection with a traditional navigable water, impoundment, or tributary; or on its own or in combination with similarly situated waters in the region significantly affects the chemical, physical, or biological integrity of a traditional navigable water (collectively, “jurisdictional interstate waters”)

These categories of WOTUS are similar to the categories identified in the 1986 rules with a few exceptions. For example, the 2022 rule limits the types of impoundments that may satisfy the WOTUS definition only to impoundments of navigable waters, tributaries, and jurisdictional wetlands. Under the 1986 rule, all impoundments of any water described as a WOTUS fell under CWA jurisdiction. Additionally, the 2022 rule incorporates both tests from Rapanos by requiring that tributaries, wetlands, and interstate waters either satisfy the plurality’s test, or share a significant nexus with a traditional navigable water.

The second portion of the 2022 WOTUS rule lays out exceptions to the rule. These are waters that will not meet the WOTUS definition even if they fall into one of the five categories outlined above. Many of these exclusions are longstanding and have been included in previous WOTUS definitions. Importantly, the 2022 WOTUS rule maintains two exclusions relevant to agriculture: prior converted cropland, and waste treatments systems that are otherwise designed to meet CWA requirements. Prior converted cropland is defined as any area that was drained or otherwise manipulated to make production of agriculture possible prior to December 23, 1985. 40 C.F.R. § 120.2(3)(ix). If the area becomes unavailable for the production of agricultural commodities, it loses its prior converted cropland status. Other exceptions found in the 2022 WOTUS rule include ditches that do not carry a relatively permanent flow of water, artificially irrigated areas that would revert to dry land if irrigation stopped, and various artificial ponds and pools.

The final section of the 2022 WOTUS rule provides definitions for key terms within the rule itself. Some of the definitions are consistent with previous regulations while other definitions have been codified for the first time. Importantly, the 2022 rule maintains the same definition for “adjacent” that has been in place for decades. Under the rule, “adjacent” is defined as “bordering, contiguous, or neighboring.” It further explains that “wetlands separated from other waters of the United State by man-made dikes or barrier, natural river berms, beach dunes, and the like are ‘adjacent wetlands.’” This term is critical for helping to determine which wetlands fall under CWA jurisdiction.

The 2022 WOTUS rule also introduces a definition for “significantly affect.” According to the rule, “significantly affect” means “a material influence on the chemical, physical, or biological integrity of” traditional navigable waters. The rule goes on to outline “functions to be assessed” and “factors to be considered” when determining whether a waterbody meets the “significantly affect” standard. The functions to be assessed include: contribution of flow; trapping, transformation, filtering, and transport of materials such as nutrients or sediment; retention and attenuation of floodwaters and runoff; modulation of temperature in traditional navigable waters; and provision of habitat and food resources for aquatic species located in traditional navigable waters. The factors to be considered include: the distance from a traditional navigable water; hydrologic factors such as the frequency, duration, magnitude, timing, and rate of hydrologic connections; the size, density, or number of waters that are similarly situated; landscape and geomorphology; and climate variables such as temperature, rainfall, and snowpack. EPA will consider all of these elements when determining whether a waterbody has a sufficient significant affec” on a traditional navigable water to satisfy the definition of WOTUS.

Finally, the document accompanying the 2022 WOTUS rule outlines how EPA intends to implement the rule. Although this is not part of the rule itself, it provides insight to how EPA expects the rule to function. According to this document, EPA will begin its WOTUS analysis by first considering if a waterbody qualifies as a traditional navigable water. If so, the analysis is complete and the waterbody will be classified as a WOTUS. If the waterbody does not qualify as a traditional navigable water, EPA will next consider whether any of the exclusions to the WOTUS rule apply. If an exclusion applies, the waterbody is not jurisdictional and EPA will end its analysis. If an exclusion does not apply, EPA will determine if the waterbody is either an impoundment, a tributary, or an adjacent wetland. If the waterbody satisfies either of these definitions, then it will be considered a WOTUS. If the waterbody is not found to be an impoundment, a tributary or an adjacent wetland, EPA will move on and assess whether the waterbody could be jurisdictional under the final category of jurisdictional interstate waters. If the waterbody is found to fall under that category, then the water is a WOTUS. If the waterbody does not fall under that category, then the water is not a WOTUS and EPA’s analysis is at an end.

Going Forward

At the time this article was published, the 2022 WOTUS rule has not been introduced to the Federal Register. The rule will not go into legal effect until 60 days after it is entered into the Federal Register. Until that time, the pre-2015 regulations will remain in effect.

While the 2022 WOTUS rule marks the end of EPA’s most recent rulemaking process to redefine WOTUS, it does not mean that the definition is fully settled. In late 2022, the United States Supreme Court heard oral argument in a lawsuit titled Sackett v. EPA, where the Court was asked to revisit its ruling in Rapanos. The Court’s opinion in that lawsuit is expected to issue later this year. Depending on what is in the Court’s final decision it may be necessary for EPA to revisit or revise the definition of WOTUS once again. It is also likely that the 2022 WOTUS rule will face additional lawsuits that could result in further revisions.

The National Agricultural Law Center will continue to provide updates on WOTUS as the new rule goes into effect.


To read the text of the 2022 WOTUS rule, click here.

For more resources from EPA on the 2022 WOTUS rule, click here.

For more information on Sackett v. EPA, click here.

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