Southwestern states are bracing for many of their streams to lose federal safeguards under the EPA’s proposal to lift Clean Water Act protections for many wetlands and waterways across the US.

New Mexico, Arizona, California, and other arid states face the brunt of the Environmental Protection Agency’s proposal because it explicitly excludes streams that only run when it rains—one of the most common kinds of waterways in the desert Southwest.

The EPA proposed Monday a reduced scope of federal jurisdiction over waterways and wetlands as waters of the US, or WOTUS. The proposal appeared in the Federal Register pre-publication notices Wednesday and is open for public comment for 45 days.

“The proposed WOTUS definition will shed federal protections for at least 89% of New Mexico’s rivers and streams and up to 70% of our wetlands,” said Drew Goretzka, spokesman for the New Mexico Environment Department. “This is primarily because most of New Mexico’s surface water is ephemeral, including many tributaries to the Rio Grande.”

Goretzka says drinking water costs will rise, and the local economy and ecosystems will suffer because of the rollback.

The proposal leaves waters and wetlands in arid regions without strong state regulations with few protections at all, said Larry Liebesman, a former Justice Department attorney who is a senior adviser for environmental permitting firm Dawson & Associates.

Wet Season Standard

States concerned about the proposed rule’s impact should direct their ire toward the US Supreme Court’s 2023 ruling in Sackett v. EPA, not the agency, Liebesman said.

Sackett requires waters protected under the Clean Water Act to be “indistinguishable” from navigable waters and “relatively permanent,” which the proposed rule says includes waterways that are wet primarily in the “wet season,” but excludes streams that are wet only when it rains.

The EPA’s proposed rule supports that by lifting protections for dry washes, arroyos, and other desert waterways common in the Southwest that are only episodically wet, said Damien Schiff, the Pacific Legal Foundation attorney who successfully argued Sackett before the Supreme Court.

The rule doesn’t clearly define “wet season,” however, and it’s unlikely that it includes the Southwest’s summer monsoons, which drench the region’s deserts episodically but still leave many stream beds running only ephemerally.

“This does mean that a significant number of features that have traditionally been regulable to some extent under the Clean Water Act would not be regulable,” Schiff said.

Lifting More Safeguards

The EPA’s proposal could take an even more drastic turn if it shifts toward an alternative within the draft rule that would leave even more waters outside the reach of the Clean Water Act, Schiff said.

The agency is seeking public comment on an approach championed by Justice Clarence Thomas in a concurring opinion in Sackett suggesting only waters navigable by boats for interstate commerce and their tributaries qualify as WOTUS.

“All other waters would be excluded,” the EPA says in the proposal.

Under that scenario, protected waters would be limited to those that are a “channel of commerce,” Schiff said.

That includes both the primary waterway and its tributaries, while other waters qualify for state regulation, Thomas wrote.

“I think adoption of Justice Thomas’s test will further narrow what the agencies can regulate,” Schiff said.

Onus on States

The proposed rule ultimately puts the onus on the states to regulate ephemeral streams and possibly other waters, Schiff said.

Federal protections provide a more uniform degree of management for many waters and wetlands, and without them, regulations will vary from state to state. Most states, for example, have relied on a federal permitting process for construction and pollution that could affect most of their waterways.

Southwestern states are preparing to rely on their own regulations to protect ephemeral streams.

Most of California’s wetlands in arid parts of the state won’t meet Sackett‘s requirement for federal protection, and the EPA’s proposed rule will reduce those protections even further, said Nick Cahill, spokesman for the California State Water Resources Control Boards.

But state “rules protect California’s waters and the people, fish and wildlife that depend on those waters,” he said, adding that officials there are still reviewing the proposed rule.

Arizona created its own surface water protection program as a response to regularly changing WOTUS definitions and implemented regulations that took effect in 2023.

The Arizona Department of Environmental Quality is still reviewing the proposed rule, spokeswoman Alma Suarez said. She declined to comment further.

New Mexico is seeking permission from the EPA to control its own surface water pollution permitting program in the wake of reduced federal protections, and it’s developing a state dredge-and-fill permitting program to fill the regulatory gaps. Draft state surface water permitting rules were published in August.