On January 18, 2023, the U.S. Environmental Protection Agency (EPA) and the Army Corps of Engineers (Corps) published a final rule (2023 Rule) revising the definition of “waters of the United States” (WOTUS) as used in the Clean Water Act (CWA). This 2023 Rule follows years of uncertainty as to the scope of CWA jurisdiction that has included nationwide litigation and multiple Supreme Court decisions. The 2023 Rule returns the WOTUS definition to the one that was used from 1986 to 2015. The 2023 Rule will become effective on March 20, 2023. Schwabe previously discussed the background and significance of the WOTUS definition here.


The CWA regulates the discharge of pollutants to “navigable waters,” which are defined to mean “any waters of the United States, including territorial seas.”1 Waters of the United States are not further defined in the CWA, which leaves significant latitude for agencies to define the CWA’s extent through rulemaking, subject to the bounds of the statutory text and Congress’s power under the Commerce Clause. Uncertainty over the CWA’s reach has affected farmers, ranchers, timberland owners, developers, and others whose activities can result in the discharge of fill or pollutants to water bodies ranging from drainage ditches to wetlands to navigable rivers and lakes.

The EPA and the Corps each issued regulations in the mid-1970s to define WOTUS. The Corps’ rules, which primarily focused on tidally influenced waters and those used for interstate or international commerce, quickly came under judicial criticism for being overly narrow.2 In response, the Corps expanded the definition to include “isolated wetlands and lakes, intermittent streams, prairie potholes, and other waters that are not part of a tributary system to interstate waters or to navigable waters of the United States, the degradation or destruction of which could affect interstate commerce.”3 The Corps re-codified its definition in 1986, which reflected both its and the EPA’s interpretation of the WOTUS definition.4 These re-codified regulations, including amendments made in 1993, are generally called the “1986 Regulations.”

Then in 2006, even though it did not result in a clear majority opinion, the U.S. Supreme Court’s decision in Rapanos v. United States represented a milestone in the history of the CWA’s jurisdictional reach.5 Justice Antonin Scalia’s opinion for four justices would have limited the CWA’s applicability to “relatively permanent, standing, or continuously flowing bodies of water” with connections to navigable water bodies.6 Justice Anthony Kennedy’s concurring opinion would have expanded the CWA’s reach to those waters, plus waterbodies with a “significant nexus” to navigable waters, which would include wetlands that “significantly affect the chemical, physical, and biological integrity of other covered waters more readily understood as ‘navigable.’”7

In the years following Rapanos, the agencies made jurisdictional determinations as to whether waters were WOTUS based on the two standards elucidated in that opinion, meaning that waters would be within the CWA’s jurisdiction if they were either relatively permanent or had a significant nexus to navigable waterways. In 2015, however, the Obama Administration proposed revisions to the definition of WOTUS (2015 Rule) that many viewed as an expansion of CWA jurisdiction. In 2020, the Trump Administration published the Navigable Waters Protection Rule (2020 Rule). We previously summarized the 2020 Rule here. However, the 2020 Rule was vacated by a decision of the U.S. District Court for the District of Arizona on August 30, 2021.8 Since that time, the EPA and the Corps have been interpreting WOTUS consistent with the pre-2015 WOTUS regulations. The 2023 Rule will again revise the definition of WOTUS under the CWA regulations.

2023 Rule

The 2023 Rule reverts to the definition of WOTUS from the 1986 Regulations, which were in effect from 1986 until 2015. The 2023 Rule describes those waters or features that it seeks to cover as WOTUS, describes waters or features that are explicitly excluded as WOTUS, and provides guidance for determining jurisdiction of waters or features that are not explicitly covered or excluded as WOTUS. It is for the third category of waters that the 2023 Rule defines important terms such as “relatively permanent” and “significant nexus” for the first time.

The following are explicitly covered by the definition of WOTUS under the 2023 Rule:

  • Traditional navigable waters, the territorial seas, and interstate waters;
  • Impoundments of waters otherwise identified as WOTUS;
  • Tributaries of navigable waters, the territorial seas, interstate waters, or impoundments if the tributaries meet either the relatively permanent standard or the significant nexus standard (“jurisdictional tributaries”);
  • Jurisdictional adjacent wetlands, which are wetlands adjacent to navigable waters; wetlands adjacent to and with a continuous surface connection to relatively permanent impoundments; wetlands adjacent to tributaries that are “relatively permanent”; or wetlands adjacent to “relatively permanent” impoundments or jurisdictional tributaries when the wetlands meet the significant nexus standard; and
  • Intrastate lakes and ponds, streams, or wetlands not otherwise identified that meet the relatively permanent standard or the significant nexus standard.

This fifth category of WOTUS is newly defined in the 2023 Rule and essentially codifies longstanding agency practice in the wake of Rapanos. The “relatively permanent standard” means “permanent, standing or continuously flowing” waters connected to traditional navigable waters, the territorial seas, and interstate waters, or waters with a “continuous surface connection” to such relatively permanent waters. The 2023 Rule explains that this definition is meant to “encompass[] surface waters that have flowing or standing water year-round or continuously during certain times of the year. Relatively permanent waters do not include surface waters with flowing or standing water for only a short duration in direct response to precipitation.” The 2020 Rule defined relatively permanent tributaries using the familiar terms “perennial” and “intermittent,” but the 2023 Rule does not.

The 2023 Rule does not explicitly exclude isolated and ephemeral water features from the definition of WOTUS, whereas the 2020 Rule explicitly excluded ephemeral streams and features that flow only due to precipitation from the definition of WOTUS. Instead, whether a water is federally regulated will be a case-by-case determination based on whether the streams have “relatively permanent” flows or a “significant nexus” to navigable waters.

As a component of determining whether a water is “relatively permanent,” the 2023 Rule does not consider the flow of water in a “typical year.” Instead, the 2023 Rule acknowledges that factors that affect streamflow are climatically and geographically specific and will vary by region. As such, the 2023 Rule makes clear that Corps jurisdictional determinations will continue to be driven by regional characteristics.

The “significant nexus standard” used to identify the fifth category of WOTUS “means waters that, 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, or interstate waters.” This standard will look familiar as the significant nexus test put forward by Justice Kennedy in his opinion in the Rapanos case in 2006.9

For farmers, ranchers, developers, and others with waters that do not clearly fit into one of the first four categories of WOTUS, but may fall within the fifth category, the WOTUS definition does not create a bright-line distinction to determine whether a water is a WOTUS. Therefore, jurisdictional determinations from the Corps will still be a necessary tool for obtaining regulatory clarity.

The 2023 Rule retains longstanding exclusions from the definition of WOTUS. The 2023 Rule will codify the following eight exclusions from the definition of WOTUS:

  • Prior converted cropland;
  • Waste treatment systems;
  • Ditches (including roadside ditches) excavated wholly in and draining only dry land, and that do not carry a relatively permanent flow of water;
  • Artificially irrigated areas that would revert to dry land if the irrigation ceased;
  • Artificial lakes or ponds, created by excavating or diking dry land, that are used exclusively for such purposes as stock watering, irrigation, settling basins, or rice growing;
  • Artificial reflecting pools or swimming pools, and other small ornamental bodies of water created by excavating or diking dry land;
  • Water-filled 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 operation is abandoned and the resulting body of water meets the definition of “waters of the United States;”
  • Swales and erosional features (e.g., gullies, small washes) that are characterized by low-volume, infrequent, or short-duration flow;

Some of these exclusions were explicit in the pre-2015 rules, while others codify longstanding agency practice. In developing the 2023 Rule, the agencies declined requests from certain commenters to add additional exclusions to the definition of WOTUS for things like stormwater control features, wastewater and drinking water treatment facilities, and water recycling plants, citing a desire to maintain consistency with pre-2015 regulations.

There are some significant changes from the 2020 Rule related to the scope of jurisdiction over “adjacent wetlands.” However, the definition of “adjacent wetlands” is consistent with how the term has been defined previously. “Adjacent” in the 2023 Rule means “bordering, contiguous, or neighboring. Wetlands separated from other waters of the United States by man-made dikes or barriers, natural river berms, beach dunes, and the like are ‘adjacent wetlands.’” The EPA and Corps have three criteria to determine adjacency, and if any one of the criteria is met, the wetland is adjacent. First, if there is a surface or shallow subsurface connection to a jurisdictional water; if a wetland is physically separated from a jurisdictional water by human-made dikes or barriers, or natural landforms; or if the wetland’s proximity to a jurisdictional water is reasonably close such that “adjacent wetlands have significant effects on water quality and the aquatic ecosystem.”10

For comparison to the previous WOTUS rules, the 2015 Rule was criticized for including as jurisdictional any wetlands or other water features that were situated within the 100-year floodplain of a jurisdictional water, regardless of if a surface connection existed or if a delineated boundary was shared. The 2020 Rule removed any floodplain criterion and instead focused on a direct surface connection or shared boundary.

Finally, the 2023 Rule does not explicitly exclude groundwater from the definition of WOTUS because it explains that since it is not a surface water, it does not fall within the possible scope of “navigable waters.” However, as the Supreme Court ruled in 2020 in County of Maui v. Hawaii Wildlife Fund, discussed further here, discharges into groundwater may fall under the jurisdiction of the CWA to the extent that they represent the “functional equivalent” of a discharge directly into navigable waters. Under County of Maui, while groundwater itself is not jurisdictional as a WOTUS, discharges of pollutants to groundwater that reach a jurisdictional surface water require a National Pollutant Discharge Elimination Systempermit where the discharge through groundwater is the “functional equivalent” of a direct discharge from the point source into navigable waters.11

Looking Ahead

The State of Texas and several industry groups have already sued to prevent the 2023 Rule from coming into effect. The challengers argue that the new rule pushes CWA jurisdiction past its statutory text and the extent of Congress’s regulatory authority under the Commerce Clause. Because of the lack of any consensus in Rapanos and the new composition of the Supreme Court, it is quite likely that some challenges to the 2023 Rule will make it to the Supreme Court. In the meantime, it is possible that parties will secure preliminary injunctions to prevent the rule from taking effect while the litigation moves through the courts.

Putting aside the certain litigation ahead, many jurisdictional determinations by the EPA and Corps will remain close, case-by-case calls even under the new 2023 Rule. Property owners and project developers will need to carefully consult the new rules and explanatory materials in order to determine whether their project is likely to be regulated by the CWA.

This article summarizes aspects of the law and does not constitute legal advice. For legal advice for ‎your situation, you should contact an attorney.

[1] 33 U.S.C. § 1362(7).

[2] Natural Resources Defense Council, Inc. v. Callaway, 392 F. Supp. 685, 686 (D.D.C. 1975) (holding that WOTUS “is not limited to the traditional tests of navigability”).

[3] 33 CFR 323.2(a)(5) (1978).

[4] 51 FR 41206, 41216–17 (November 13, 1986).

[5] Rapanos v. U.S., 547 U.S. 715 (2006).

[6] Id. at 739.

[7] Id. at 780.

[8] Pascua Yaqui Tribe v. U.S. Environmental Protection Agency, 557 F. Supp. 3d 949 (D. Ariz. 2021). That case was appealed to the Ninth Circuit, but was voluntarily dismissed by the appellants before it was resolved.

[9] Rapanos v. U.S., 547 U.S. 715 (2006).

[10] See 2023 Rule discussing the well-established criteria to determine adjacency, which stems in part from U.S. v. Riverside Bayview, 474 U.S. 121 (1985).

[11] County of Maui v. Hawaii Wildlife Fund, 140 S. Ct. 1462, 1468 (2020).

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