Under the Clean Water Act (CWA), the U.S. federal government is responsible for regulating the discharge of pollutants into the “navigable waters of the United States” and has discretionary power to formulate the regulatory details and geographical scope of federal jurisdiction over those “navigable waters.” 

The manner in which the government should define these “navigable waters” has been long discussed and, in recent years, intensively litigated. The U.S. Supreme Court last interpreted the meaning of “navigable waters” in Rapanos v. United States, 547 U.S. 715 (2006), where the Court considered the question of whether “navigable waters” under the CWA include “wetlands that do not contain and are adjacent to waters that are navigable in fact.” The Court was unable to reach a majority opinion, which created ambiguity as to how to determine CWA jurisdiction and left interpretive discretion to the lower courts. This lack of a clear majority rule also prompted each recent presidential administration to alter the definition.  

In January 2021, President Joe Biden issued Executive Order 13990, directing the U.S. Environmental Protection Agency (EPA) and the U.S. Army Corps of Engineers (the Corps) to review the latest definition of “waters of the United States” (WOTUS), published in April 2020 under the Trump administration. In June 2021, EPA and the Corps announced their intention to conduct a two-part rulemaking: one rule to restore the pre-2015 WOTUS framework—also known as the 1986 regulations—with updates consistent with U.S. Supreme Court decisions, and a second rule to improve on the WOTUS definition.

On December 30, 2022, EPA and the Corps released a pre-published version of a new final rule revising the controversial WOTUS definition, later published in the Federal Register on January 18, 2023. As the first step of the rulemaking, the new rule reverted to the pre-2015 WOTUS definition. According to EPA, the past decade-plus of regulatory and judicial interpretations of WOTUS have resulted in great ambiguity among the agricultural community and landowners, which justified a new rule.

The New Definition of “Waters of the United States” 

The rule implements the 1986 regulatory WOTUS definition, relying on “the relevant provisions of the Clean Water Act and the statute as a whole, the scientific record, relevant Supreme Court decisions, and the agencies’ experience and technical expertise after more than 45 years of implementing the longstanding pre-2015 regulations defining ‘waters of the United States.’”

Under the new rule, the agencies define WOTUS as including:

  • “Traditional navigable waters, the territorial seas, and interstate waters;” 
  • “Impoundments of ‘waters of the United States’;”
  • “Tributaries to traditional navigable waters, the territorial seas, interstate waters, or . . . [WOTUS] impoundments when the tributaries meet either the ‘relatively permanent standard’ or the ‘significant nexus standard’;” 
  • “Wetlands adjacent to [traditional waters, the territorial seas, and interstate waters];” 
  • “Wetlands adjacent to and with a continuous surface connection to relatively permanent [WOTUS] impoundments;” 
  • “Wetlands adjacent and with a continuous surface connection . . . to jurisdictional tributaries when the jurisdictional tributaries meet the ‘relatively permanent standard’;” 
  • “Wetlands adjacent to [WOTUS] impoundments or jurisdictional tributaries when the wetlands meet the ‘significant nexus standard’;” 
  • “Intrastate lakes and ponds, streams or wetlands not identified in [one of the above categories] and that meet either the ‘relatively permanent standard’ or the ‘significant nexus standard’.” 

The “Relatively Permanent “ or “Significant Nexus” Standards 

Under the new rule, the agencies may assert their jurisdiction over waters using either the “relatively permanent” or “significant nexus” standards set forth in Rapanos, giving the agencies expanded—and as such, controversial—legal authority. In the rule, the agencies stated that it would be unreasonable to exclude some waters from the WOTUS definition just because they do not meet the “relatively permanent standard.”

Under the “relatively permanent standard,” waters fall under the CWA if they are “relatively permanent, standing or continuously flowing” [and] “connected to [traditional navigable waters, the territorial seas, and interstate waters].” CWA jurisdiction also includes “waters with a continuous surface connection to such relatively permanent waters or to [traditional navigable waters, the territorial seas, and interstate waters].” The rule does not specifically define “relatively permanent,” which could potentially invite different interpretations. 

On the other hand, waters meet the “significant nexus standard” if they “either alone or in combination with similarly situated waters in the region, significantly affect the chemical, physical, or biological integrity of traditional navigable waters, the territorial seas and interstate waters.” The rule defines “significantly affect” as “a material influence on the chemical, physical, or biological integrity of traditionally navigable waters.”

In measuring “material influence”, the agencies will consider the functions of a water—whether a water influences the movement of jurisdictional waters, supports the quality of aquatic ecosystems, and protects jurisdictional waters from sediment and nutrient pollution—and a number of factors to determine the “material influence” of a water function on the integrity of jurisdictional waters These factors include hydrologic constituents, such as the “frequency, duration, magnitude, timing, and rate of hydrologic connections,” water density and size, landscape position and geomorphology of waters, and climate variables.


Under the rule, the agencies define “adjacency” to mean “bordering, continuous, or neighboring,” and clarify that wetlands do not necessarily need to share a physical connection with jurisdictional waters to be considered adjacent. Indeed, wetlands are adjacent as long as they have a “close proximity” with jurisdictional waters, which exist when the wetland can alter both water quantity and water quality in the jurisdictional water and vice versa

Additionally, the rule states that wetlands are adjacent even if they are separated by natural and artificial features In the event of an artificial barrier, the agencies must consider whether there is a “subsurface hydrologic connection” between the wetland and jurisdictional water; however, no such connection is required for natural barriers. 

Statutory Exemptions and Regulatory Exclusions 

 Section 404 of the Clean Water Act provides permitting exemptions for agricultural activities, such as “normal farming, silviculture, and ranching activities,” “construction of farm or stock ponds, or irrigation ditches,” and “construction or maintenance of farm roads,” among other things. As such, these activities are not affected under the new final rule.  

In addition to the pre-2015 regulatory exclusions, the new final rule adds six new exclusions for “features that were generally not considered non-jurisdictional under the pre-2015 regulatory regime:”

  1. “Ditches (including roadside ditches) excavated wholly in and draining only dry land and that do not carry a relatively permanent flow of water; 
  2. Artificially irrigated areas that would revert to dry land if the irrigation ceased;
  3. Artificial lakes or ponds created by excavating or diking dry land to collect and retain water and which are used exclusively for such purposes as stock watering, irrigation, settling basins, or rice growing;  
  4. Artificial reflecting or swimming pools or other small ornamental bodies of water created by excavating or diking dry land to retain water for primarily aesthetic reasons;  
  5. Waterfilled depressions created in dry land incidental to construction activity and pits excavated in dry land for the purpose of obtaining fill, sand, or gravel unless and until the construction or excavation operation is abandoned and the resulting body of water meets the definition of waters of the United States; and   
  6. Swales and erosional features (e.g., gullies, small washes characterized by low volume infrequent, or short duration flow.”

EPA and the Corps codified these six new exclusions, in addition to “longstanding” exclusions for prior converted cropland and waste treatment systems. Consistent with the U.S. Department of Agriculture’s (USDA) definition, prior converted croplands do not fall under the WOTUS definition so long as the area remains “available for the production of agricultural commodities.” EPA and the Corps interpret the terms “available for the production of agricultural commodities” as including “uses such as crop production, haying, grazing, agroforestry, or idling land for conservation uses.

 What’s Next 

 On October 3, 2022, the U.S. Supreme Court heard oral arguments in Sackett v. EPA, a pivotal case involving a longstanding dispute of whether the federal government can regulate certain wetlands under the Clean Water Act. The case questions whether the “relatively permanent standard” or the “significant nexus standard” determines CWA jurisdiction over wetlands. While the Court has not yet ruled on this matter, the Court’s decision could potentially alter the legal foundation of the new rule.  

In the meantime, the new final rule is set to become effective on March 20, 2023, and EPA is expected to release a proposed second rule further clarifying the WOTUS definition in November 2023.


Chloe Marie, Research Specialist


Executive Order on Protecting Public Health and the Environment and Restoring Science to Tackle the Climate Crisis, 86 FR 7037 (January 25, 2021)

EPA Press Release, EPA, Army Announce Intent to Revise Definition of WOTUS (June 9, 2021)

EPA Press Release, EPA and Army Finalize Rule Establishing Definition of WOTUS and Restoring Fundamental Water Protections (Dec. 30, 2022)

Revised Definition of “Waters of the United States,” 88 FR 3004 (January 18, 2023)

Final Rule: Revised Definition of “Waters of the United States,” Fact Sheet for the Agricultural Community (December 2022)

Sackett v. EPA, U.S. Supreme Court, No. 21-454 (certiorari granted January 24, 2021)

Fall 2022 Unified Agenda of Regulatory and Deregulatory Actions