The Trump administration is rolling back protections for streams and wetlands, adopting a new rule that will drop federal clean-water safeguards for many creeks and washes across Arizona and the Southwest.

The nationwide change scraps a regulation that was adopted during the Obama administration and replaces it with a weaker rule that could help fast-track development and mining projects and could leave some streams and washes vulnerable to being filled in or polluted.

Environmental groups said the revised rule, released Thursday, would gut protections under the Clean Water Act and vowed to challenge the new rule in court.

The change will especially affect regulation of ephemeral streams and washes, which flow intermittently when it rains but otherwise sit dry much of the year.

In Arizona, that may mean that the vast majority of “waters” that were previously regulated by the federal government — from arroyos to wetlands to desert washes — no longer fall under Clean Water Act protections.

“It basically means that if you have a wetland or a wash or a stream in Arizona, you can do what you want to it,” said Brett Hartl, government affairs director for the Tucson-based Center for Biological Diversity. “Every water body is now very vulnerable and could be either polluted or filled or destroyed without having to worry about Clean Water Act compliance.”

The Obama administration expanded the federal government’s authority to regulate wetlands and washes in 2015 when it adopted the regulation, called the Waters of the United States rule, or WOTUS.

That measure was criticized by Republicans and business groups including builders, farmers and golf course managers, who called it an overreach by the federal government.

'Bringing clarity once and for all'

The Environmental Protection Agency said Thursday it has finalized the new rule for protection of “navigable waters.”

EPA Regional Administrator Mike Stoker pointed out that there have been various different interpretations of the definition of “waters of the United States” since the Clean Water Act was adopted in 1972, and that those disagreements have spurred litigation.

The Obama-era rule had greatly expanded Washington’s reach into private lands, he said, and the new rule “is putting an end to this overreach.”

“We are bringing clarity once and for all to American farmers, landowners and businesses,” Stoker said at a news conference in Phoenix, accompanied by Republican U.S. Rep. Paul Gosar of Arizona.

“What I think we've tried to do with this rule is basically enact a rule that's what Congress intended — nothing more and nothing less,” Stoker said. He cited the role of states’ rights in the Constitution, and said “if a state has lost any anything in this final rule when it's adopted, they have the right to backfill it.”

Gosar said the Obama administration’s measure had a “detrimental impact” for businesses in Arizona. He said protecting private property rights is an important aspect of the new rule and it will “provide a much more workable definition of navigable waterways.”

Streams become more vulnerable

Under the Trump administration’s measure, federally regulated “waters of the United States” include constantly flowing rivers and “intermittent tributaries,” as well as adjacent wetlands. No longer federally regulated are “features that only contain water in direct response to rainfall,” as well as groundwater, ditches and cropland, among other things.

In arid Western states, that means many seasonal streams will no longer make the list for federal regulation. These washes and creeks often roil after rains but soon dry up. The water retreats and mostly flows on underground.

In places where some water remains in these on-off streams, it sustains animals such as frogs, salamanders and rare desert fish.

In Arizona, Hartl said nearly all of the state’s wetlands and tributaries — with the exception of wetlands along the Colorado River — won’t qualify and will no longer get protection under the Clean Water Act.

“Everything now becomes vulnerable to being destroyed, to being polluted, without any backstop or safeguard,” Hartl said.

“It’s basically a free-for-all for building. The same is true for mining,” he added. “For them, obviously, it makes it cheaper. But for everybody else, we’re going to bear that cost.”

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The Center for Biological Diversity says Arizona and New Mexico could lose protections for more than 95% of their water bodies under the new rule. It says the loss of protections puts more than 75 endangered species at risk, including Chiricahua leopard frogs and yellow-billed cuckoos.

Hartl said the center will be among the groups challenging the rule in court.

Gina McCarthy, who led the EPA under Obama and now heads the Natural Resources Defense Council, also condemned a change that she said will end up polluting drinking water supplies.

“This effort neglects established science and poses substantial new risks to people’s health and the environment,” McCarthy said in a statement. “We will do all we can to fight this attack on clean water. We will not let it stand.”

Waterways are 'like the capillaries'

The group Trout Unlimited said in Arizona, 74 percent of the steam miles mapped by the U.S. Geological Survey are classified as ephemeral and that the change jeopardizes these vital portions of the watersheds.

“Headwaters and wetlands are some of the most important components to our network of streams and rivers,” said Chris Wood, president and CEO of Trout Unlimited. “They’re like the capillaries in our bodies. If they’re unhealthy, so is everything else.”

Business groups supported the Trump administration’s effort. The American Farm Bureau Federation said in a statement that the new water rule “provides clarity and certainty, allowing farmers to understand water regulations without having to hire teams of consultants and lawyers.”

The Fertilizer Institute, which represents the fertilizer industry, said the rule “provides a sustainable national water policy that both protects the environment and facilitates smart economic development.”

Other Arizona Republicans in Congress, including Sen. Martha McSally and Rep. Andy Biggs, also voiced support. Biggs said in a statement that farmers and ranchers shouldn’t have to deal with “unnecessary bureaucratic nonsense” and that the new rule “will keep Washington’s heavy hand" away from Western lands.

Officials in Gov. Doug Ducey’s administration also support the Trump administration’s stance. In an April letter to EPA chief Andrew Wheeler and Assistant Secretary R.D. James of the Army Corps of Engineers, Arizona officials said they support the rule’s “overall approach to providing clarity.”

State will consider 'Waters of Arizona' rules

Erin Jordan, a spokesperson for the Arizona Department of Environmental Quality, said the agency’s officials acknowledge “that the narrower definition creates a gap in protection for many Arizona waterways.”

ADEQ plans to start holding meetings to discuss ideas for a new "Waters of Arizona" program, which the agency says will involve developing a “local control” approach to protecting the state’s water resources.

It’s unclear to what extent state regulation might eventually help take the place of diminished federal protections.

But one nonpartisan think tank warns that states probably won’t do nearly enough.

Bethany Davis Noll, litigation director of the Institute for Policy Integrity at New York University’s law school, said in a statement that “despite the Trump administration’s assertions, most states are unlikely to fill the void with their own safeguards.”

Sandy Bahr, director of the Sierra Club’s Grand Canyon Chapter in Arizona, said the Trump administration has put in place a “ridiculous, very narrow-sighted rule.”

“We should be looking at the Clean Water Act as providing the floor of protection and then build upon that to do more, not as something that is only very narrowly focused on perennial rivers,” Bahr said. “People who think it’s a good thing for Arizona really don’t understand how important those waters are, those waters that don’t flow year-round.”

The latest fight over the federal government’s role in protecting streams and wetlands follows an earlier dispute that went before the Supreme Court. That 2006 case, Rapanos v. United States, focused on a Michigan landowner’s effort to develop property that was classified as a wetland.

The court was bitterly divided and the decision left unresolved questions, said Robert Glennon, a water expert and law professor at the University of Arizona.

“The decision of the Trump administration doesn’t bring clarity to anything. All it does is to repeal a rule that attempted to give clarity. And the problem is, the underlying law remains confused,” Glennon said. “So, we’re going to see now yet another round of litigation.”

Reach reporter Ian James at ian.james@arizonarepublic.com or 602-444-8246. Follow him on Twitter: @ByIanJames.

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Environmental coverage on azcentral.com and in The Arizona Republic is supported by a grant from the Nina Mason Pulliam Charitable Trust. Follow The Republic environmental reporting team at environment.azcentral.com and @azcenvironment on Facebook, Twitter and Instagram.