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Implications of the Revised Definition of Waters of the United States

By: Sarah Pyle

Image courtesy of Unsplash

What are the waters of the United States? While this phrase might seem quite simple at first, its legal definition has been an extremely contentious issue in the past few decades. The definition, which has been changed numerous times, is important for determining which specific bodies of water are regulated under the federal Clean Water Act. Although the most recent revision to the definition expands the protections to the nation’s waters, additional state and local regulations are necessary to strengthen those protections in case of future changes to the waters of the United States.

The term “waters of the U.S.” (WOTUS) was first introduced in 1972 with an amendment to the Clean Water Act. The amendment established that “navigable waters”, which are generally considered the “waters of the United States”, are protected under the Clean Water Act. The definition has changed multiple times since its inception as a result of various rules and court cases, with several particularly notable changes. The WOTUS definition was altered with the passage of the 2015 Clean Water Rule, and later changed again in 2020 with the Navigable Waters Protection Rule (NWPR) after the 2015 rule was repealed by the 2019 Repeal Rule. Despite the name, the NWPR actually reduced the number of protected waters due to decreased federal protections for waters such as wetlands, tributaries, groundwater, ditches, converted cropland, artificial lakes, stormwater runoff, and wastewater systems, among various others. Fortunately, the scope of protected waters was increased under the newly revised definition.

In addition to the different legislation that has been passed, WOTUS has also been altered due to court cases. The Supreme Court has previously heard several cases regarding WOTUS including United States v. Riverside Bayview Homes Inc., Solid Waste Agency of Northern Cook County v. U.S. Army Corps of Engineers, and Rapanos v. United States. Rapanos v. United States. They are especially important as they introduced the concept of a “significant nexus” when determining which waters are counted as “navigable waters”. The significant nexus standard means that the body of water has a significant physical, chemical, or biological impact on traditional navigable water. As a method of designating waters as WOTUS that otherwise might not have been considered “navigable waters”, the significant nexus standard expands the jurisdiction of the Clean Water Act and can be used to increase the number of protected waters.

With all of the changes that have occurred, the EPA and Army Corps of Engineers sought to develop a more permanent definition. As a result, the final revision was published on January 18, 2023, and has been in effect since March 20, 2023. Under the most recent version of the definition, WOTUS includes:

  • Traditional navigable waters, interstate waters, and territorial seas

  • WOTUS impoundments

  • Wetlands adjacent to traditional navigable waters, interstate waters, and territorial seas

  • Wetlands adjacent to and with a continuous surface connection to relatively permanent WOTUS impoundments

  • Wetlands adjacent to relatively permanent tributaries

  • Wetlands adjacent to WOTUS impoundments or tributaries that meet the significant nexus standard

  • Tributaries to traditional navigable waters, interstate waters, and territorial seas that meet the significant nexus or relatively permanent standard

  • Other intrastate lakes, ponds, streams, or wetlands that meet the significant nexus or relatively permanent standard.

However, the effectiveness of this rule could be impacted by the outcome of Sackett v. EPA, a current Supreme Court Case regarding whether the significant nexus test can be used to determine whether wetlands are considered WOTUS under the Clean Water Act. Based on the Court’s decision, the protections provided by the Clean Water Act could be severely limited. Without the significant nexus criterion, a large number of wetlands throughout the U.S. would no longer be regulated under the Clean Water Act. In addition to the unique biodiversity that they support, wetlands provide various ecosystem services to humans such as storm surge prevention, water filtration, and flood protection. Nearly half of the wetlands in the U.S. have been lost due to development and land use change, so it is important to preserve the few wetlands that remain.

Although the revised WOTUS definition is a step in the right direction, additional regulations are still necessary to better protect the nation’s waters. The definition determines which waters are covered under federal jurisdiction, but state and local regulations can be implemented to protect the waters that aren’t covered and further protect those that are. Therefore, it is important to ensure there are proper protections in place for all waters, especially ones that have been disputed in the past such as wetlands, stormwater, and wastewater.


Works Cited

Jones Day. (2023, January). EPA and Army Corps Promulgate New Expansive Definition of Waters of the United States. Jones Day.,territorial%20seas%2C%20or%20interstate%20waters.

Sackett v. Environmental Protection Agency. (n.d.). Oyez. Retrieved April 27, 2023, from

Tidgren, K. A. (2020, February 6). Navigable Waters Protection Rule is Finalized. Center for Agricultural Law and Taxation.

US EPA. (2022, December 30). Definition of “Waters of the United States” under the Clean Water Act.,%2C%20including%20the%20territorial%20seas.%E2%80%9D

Wetland. (n.d.). National Geographic.


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