WASHINGTON — 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 rollback of the 2015 measure, known as the Waters of the United States rule, adds to a lengthy list of environmental rules that the administration has worked to weaken or undo over the past two and a half years. Those efforts have focused heavily on eliminating restrictions on fossil fuel pollution, including coal-fired power plants, automobile tailpipes, and oil and gas leaks, but have also touched on asbestos and pesticides.

The repeal of the water rule, which is expected to take effect in a matter of weeks, 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.

Patrick Parenteau, a professor of environmental law at the Vermont Law School, said that, for conservative states and leaders who hold the view that the Clean Water Act has been burdensome for farmers and industry, “this is an opportunity to really drive a stake through the heart of federal water protection.”

Weakening the rule had been a central campaign pledge for President 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. Mr. 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,” Andrew Wheeler, the administrator of the E.P.A., said Thursday in a news conference to announce the repeal.

Mr. 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.”

Agricultural groups, an important political constituency for Mr. Trump, praised the repeal. Zippy Duvall, president of the American Farm Bureau Federation, said the water rule had sparked outrage from thousands of farmers and ranchers across the country and led to the largest effort to kill a regulation in his organization’s history.

“When you take private property rights from a man who’s worked all his life,” Mr. Duvall said, “that is very intrusive to him and it’s something he just can’t stand for.”

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 percent 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 E.P.A. 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.

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The Environmental Protection Agency and the Army Corps of Engineers, which had worked together to write the original Obama rule, are expected to issue a new, looser replacement rule by the end of this year. It is expected that the new rule, still being developed, will retain federal protections for larger bodies of water, the rivers that drain into them and wetlands that are directly adjacent to those bodies of water.

But it will quite likely strip away protections of so-called ephemeral streams, in which water runs only during or after rainfalls, and of wetlands that are not adjacent to major bodies of water or connected to such bodies of water by a surface channel of water. Those changes would represent a victory for farmers and rural landowners who lobbied the Trump administration aggressively to make them.

Lawyers said the interim period between the completion of the legal repeal of the Obama rule and the implementation of the new Trump rule this year could be one of regulatory chaos for farmers and landowners, however.

“The Obama clean water rule had very clear lines defining which waters are protected by the Clean Water Act, versus which waters are not, while repealing the rule means replacing those lines with case-by-case calls,” said Blan Holman, an expert on water regulations with the Southern Environmental Law Center.

“This will be very unpredictable,” Mr. Holman said. “They are imposing a chaotic case-by-case program to replace clear, bright-line rules.”

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