President Joe Biden’s administration on Friday finalized regulations that protect hundreds of thousands of small streams, wetlands and other waterways, repealing a Trump-era rule that federal courts had thrown out and that environmentalists said left waterways vulnerable to pollution.

The rule defines which “waters of the United States” are protected by the Clean Water Act. For decades, the term has been a flashpoint between environmental groups that want to broaden limits on pollution entering the nation’s waters and farmers, builders and industry groups that say extending regulations too far is onerous for business.

The Environmental Protection Agency and the Department of the Army said the reworked rule is based on definitions that were in place prior to 2015. Federal officials said they wrote a “durable definition” of waterways to reduce uncertainty.

In recent years, however, there has been a lot of uncertainty. After the Obama administration sought to expand federal protections, the Trump administration rolled them back as part of its unwinding of hundreds of environmental and public health regulations. A federal judge rejected that effort. And a separate case is currently being considered by the Supreme Court that could yet upend the finalized rule.

“We have put forward a rule that’s clear, it’s durable, and it balances that protecting of our water resources with the needs of all water users, whether it’s farmers, ranchers, industry, watershed organizations,” EPA Assistant Administrator for Water Radhika Fox told The Associated Press.

The new rule is built on a pre-2015 definition, but is more streamlined and includes updates to reflect court opinions, scientific understanding and decades of experience, Fox said. The final rule will modestly increase protections for some streams, wetlands, lakes and ponds, she said.

The Trump-era rule, finalized in 2020, was long sought by builders, oil and gas developers, farmers and others who complained about federal overreach that they said stretched into gullies, creeks and ravines on farmland and other private property.

Environmental groups and public health advocates countered that the Trump rule allowed businesses to dump pollutants into unprotected waterways and fill in some wetlands, threatening public water supplies downstream and harming wildlife and habitat.