“I terminated one of the most ridiculous regulations of all: the last administration’s disastrous Waters of the United States rule,” he told the American Farm Bureau Federation’s annual convention in Texas on Sunday, to rousing applause.

“That was a rule that basically took your property away from you,” added Mr. Trump, whose real estate holdings include more than a dozen golf courses. (Golf course developers were among the key opponents of the Obama rule and key backers of the new one.)

His administration had completed the first step of its demise in September with the rule’s repeal.

Mr. Trump’s replacement, called the “Navigable Waters Protection Rule,” finishes the process. It not only rolls back key portions of the 2015 rule that had guaranteed protections under the 1972 Clean Water Act to certain wetlands and streams that run intermittently or run temporarily underground, but also relieves landowners of the need to seek permits that the Environmental Protection Agency had considered on a case-by-case basis before the Obama rule.

It also gives President Trump a major policy achievement to bring to his political base while his impeachment trial continues.

“Farmers coalesced against the E.P.A. being able to come onto their land, and he’s delivering,” said Jessica Flanagain, a Republican strategist in Lincoln, Neb. “This is bigger news for agricultural producers than whatever is happening with the sideshow in D.C.,” she added.