Image courtesy of Alain Audet/Pixabay


On Sept. 8, 2023, the U.S. Environmental Protection Agency (EPA) and U.S. Army Corps of Engineers (ACE) changed the regulatory definition of the term “waters of the United States” (WOTUS). This is the fifth time that this definition – which determines the scope of the Clean Water Act – has been amended within 8 years.

This latest amendment conforms the definition of WOTUS to the U.S. Supreme Court’s decision earlier this year in the case of Sackett v. EPA. In a unanimous 9-0 ruling, the Sackett decision limited the scope of the Clean Water Act by providing that a waterbody qualifies for WOTUS protections only if it

  • is navigable, or supports interstate commerce;
  • flows across or forms part of a state’s boundaries; or
  • maintains a continuous surface connection to navigable waters.

New language included as part of this redefinition — as well as language missing from the updated guidelines — promise to dramatically shift the regulatory landscape for such crucial waterbodies as wetlands and streams.


This post-Sackett redefinition is a departure from criteria promulgated by EPA and ACE in January 2023, which upheld WOTUS status for wetlands and intermittent streams so long as they maintained a “significant nexus” to other waters receiving Clean Water Act protections. This had been the applicable standard in about 50% of U.S. states. In Sackett v. EPA, the Supreme Court rejected the “significant nexus” test outright.

The Sackett rule became effective on the day it was published. No public comments were sought or accepted on any draft of the rule.

Testifying before the U.S. Senate Committee on Environment and Public Works in October, Clemson University (South Carolina) Ecologist Mažeika Patricio Sulliván estimated that approximately 6.6 million ha (16.3 million ac) of wetlands — an area roughly the size of West Virginia — will lose federal protections as a result of the Sept. 8 redefinition. Additionally, Sulliván noted that non-permanent, ephemeral, and intermittent streams, which represent about 59% of all streams in the conterminous U.S., are also now unprotected under the Clean Water Act — amounting to at least 7.7 million km (4.8 million mi) of streams.

Unlike previous WOTUS definitions, the Sept. 8 rule also does not identify exclusions for artificial or nature-based stormwater and flood control features. This lapse means discharging pollutants into artificial or nature-based stormwater and flood control features may require a National Pollutant Discharge Elimination System (NPDES) permit under section 402 of the Act while dredging or filling previously-protected wetlands may no longer require a permit under section 404.


More than 20 U.S. states rely on the federal definition of WOTUS to regulate activities within waters in their borders. Many of these states even prohibit state-level legislators from adopting laws or regulations that exceed federal law.

In May 2023, the U.S. Supreme Court unanimously ruled that wetlands and streams only qualify for federal protections under the Clean Water Act if they maintain a continuous surface connection to navigable or interstate waters. The ruling prompted the U.S. Environmental Protection Agency to redefine “Waters of the United States” in September. Image courtesy of Mark Thomas/Pixabay

In these states, regulation of activities affecting streams and wetlands has shrunk alongside the scope of federal law. Especially in arid and mountainous areas, stormwater managers may need to reconsider whether existing discharge and dredge-and-fill permits are valid or need to be renewed if the system discharges to or affects a streambed with ephemeral or intermittent flows.

The remaining states have laws that protect waters more expansively than federal law. In these states, stormwater managers will likely need to shift their focus from the permitting and enforcement standards of federal law and onto the standards articulated in state laws.

For example, a biology or hydrology study that evaluated the presence of wetlands within a project area using a “significant nexus” test would no longer be consistent with federal law and may need to be updated to consider the standards articulated under state law. A project affecting a wetland that does not have a continuous surface connection to a traditional navigable water, for example, would probably not require a federal Section 404 dredge-and-fill permit for construction and maintenance, or a Section 402 discharge permit for operation. That same project, however, may require state permits for dredging, filling, and discharging activities.


In absence of further guidance from courts or federal agencies, the Sackett decision leaves additional areas of uncertainty for stormwater and flood control programs.

Temporary interruptions. The court in Sackett recognized that temporary interruptions in a surface connection or flow due to drought or low tides, for example, will not remove federal protections from a jurisdictional wetland, stream, lake, or other water body. The court and federal agencies, however, did not define what constitutes a “temporary” interruption to a “relatively permanent” waterbody.

Artificial barriers. The court noted that legally constructed artificial barriers between a water of the United States and a wetland ordinarily remove federal protections from the wetland. If the permit for the artificial barrier is revoked, would federal jurisdiction then extend to the wetland?

Artificial connections. The Sept. 8 redefinition excludes from federal jurisdiction ditches, including roadside ditches, that do not carry a relatively permanent flow of water. This exception, however, may not extend to ditches constructed in and draining dry land that may carry a relatively permanent flow of groundwater or other relatively permanent sources of water flows.

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