The Trump administration on Thursday announced the repeal of a major Obama-era clean water regulation that had placed limits on polluting chemicals that could be used near streams, wetlands and other bodies of water.

The repeal of the rule, known as the Waters of the United States rule, has implications far beyond the pollution that will now be allowed to flow freely into streams and wetlands from farms, mines and factories. With Thursday's announcement, the Environmental Protection Agency is aiming to establish a stricter legal definition of "waters of the United States" under the Clean Water Act, a precedent that could make it difficult for future administrations to take actions to protect waterways.

Weakening the rule had been a central campaign pledge for President Donald Trump, who characterized it as federal overreach that impinged on the rights of farmers, rural landowners and real estate developers to use their properties as they see fit. Trump signed an executive order in the early days of his administration directing federal agencies to begin the work of repealing and replacing it.

"Today's final rule puts an end to an egregious power-grab," EPA Administrator Andrew Wheeler said Thursday at a news conference.

Wheeler said the rollback would mean "farmers, property owners and businesses will spend less time and money determining whether they need a federal permit and more time building infrastructure."

But environmentalists assailed the move. "With many of our cities and towns living with unsafe drinking water, now is not the time to cut back on clean water enforcement," said Laura Rubin, director of the Healing Our Waters-Great Lakes Coalition.

The Obama rule, developed under the authority of the 1972 Clean Water Act, was designed to limit pollution in about 60% of the nation's bodies of water, protecting sources of drinking water for about one-third of the United States. It extended existing federal authority to limit pollution in large bodies of water, like the Chesapeake Bay and Puget Sound, to smaller bodies that drain into them, such as tributaries, streams and wetlands.

Under the rule, farmers using land near streams and wetlands were restricted from doing certain kinds of plowing and from planting certain crops and would have been required to obtain EPA permits in order to use chemical pesticides and fertilizers that could have run off into those bodies of water. Those restrictions will now be lifted.

It's unclear exactly how the changes will affect Minnesota.

The state passed its own wetlands protection rules in 1991, which will still regulate most of the state's smaller waters, said Don Arnosti, a longtime environmental advocate and former director of the Izaak Walton League's Minnesota Division.

"It's less of a concern here than it is in other states because we do have those protections," Arnosti said.

Kevin Paap, president of the Minnesota Farm Bureau, said the rollbacks will clear up confusion created by the Obama-era rules over where and when farmers need to get a permit to drain and farm their land.

"The problem was you didn't have a clue if you needed state permits or federal permits until you hired a lawyer or consultant to come take a look at it," Paap said.

The rule changes will remove a layer of protection for many of the smaller waters in Minnesota. And it remains to be seen if the state can pick up the slack now that federal regulations have been relaxed, not just with farming but with major industrial and housing developments as well, said ecologist Jim Almendinger, director of the field research station of the Science Museum of Minnesota.

Almendigner called the rollback "a step backwards," saying it will create a special burden for a state like Minnesota with its thousands of interconnected lakes and water bodies, all of which improve water quality and provide valuable habitat.

Staff writer Greg Stanley contributed to this report.