The Obama administration proposed rules Tuesday that would give the federal government authority over millions of acres of wetlands and thousands of miles of streams.

The plan was endorsed by anglers and environmental groups and branded a land grab by a Republican senator.

The Environmental Protection Agency said the proposal will reduce confusion about when bodies of water are under federal jurisdiction and require U.S. permits for actions such as discharges or dredging. The proposal is meant to resolve confusion resulting from contradictory court decisions.

“It’s become too difficult to determine what is and what isn’t protected, and that puts wetlands, streams and other water bodies at risk,” said EPA Administrator Gina McCarthy.

In Minnesota, the proposed rule would have a major impact and was widely praised by local environmental groups.

It is a headwaters state, meaning that all of its rivers, including the major ones like the Mississippi and Minnesota, originate within its borders, and are fed by countless tiny streams and wetlands that have not been protected by the Clean Water Act.

According the national Association of Wetland Managers, more than half of Minnesota’s streams are intermittent and have not been protected in the past by federal law. And nearly a million people in Minnesota get their drinking water from sources that are least partly fed by intermittent and ephemeral streams.

In addition, the prairie potholes of the Dakotas and western Minnesota, which produce half the nation’s ducks, would be protected by federal law.

For decades, government officials and businesses have disputed the meaning of one phrase — the “waters of the United States” — in the federal law. The new proposal seeks to clear up the definition.

Opponents said the EPA plan is an expansion of government powers. “The ‘waters of the U.S.’ rule may be one of the most significant private property grabs in U.S. history,” said Sen. David Vitter, R-La.

Staff writer Josephine Marcotty contributed to this report.