Waterman Bubby Powley, 66, goes crabbing on the Chesapeake Bay near Hooper Island, Md., in June. (Linda Davidson/The Washington Post)

President Trump’s proposed budget would eliminate federal funding for the cleanup of the Chesapeake Bay, the largest program to restore a body of water in U.S. history, just as the effort reaches its halfway point.

The Environmental Protection Agency awards millions in grants each year to the District, nonprofit agencies and six states in the bay watershed — Virginia, Maryland, West Virginia, Pennsylvania, New York and Delaware — to pay for restoration.

The program’s budget has increased to $73 million from its low point at the end of the administration of President George W. Bush. Last year, Virginia and Maryland and its local governments received about $9 million each from the program.

If enacted, Trump’s budget threatens to derail the cleanup efforts, accomplishing a goal opponents of the program could not.

“We’ve been reliant on this money to make sure the bay is restored. Without it, there is no cleanup,” said Chante Coleman, director of the Choose Clean Water Coalition.

Eighteen million people live in the 64,000-square-mile bay watershed. It’s a source of recreation, including boating and fishing, and sustains a large commercial fishing and crabbing industry.

In 2010, the watershed states and the District agreed to take specific cleanup steps by 2025, including upgrades to deteriorating sewer facilities and fences to limit chemical runoff from farms. Numerous studies have shown that water quality in the bay was improving.

The biggest sources of pollution have been nutrients and sediment that flow from cities and farms. There was a time when oysters nearly vanished from the bay because of the pollution, and crabs and fish suffocated by the hundreds.

Farmers, home builders and chemical companies unsuccessfully fought the plan in court, saying a cleanup should be governed by the states, not the EPA.

Scott Pruitt, Trump’s EPA administrator, was attorney general of Oklahoma at the time. He joined opponents who feared the government would use the bay program as a model to regulate the Mississippi River watershed.

Although Pruitt recently said he supported multi-state solutions to improve the health of the bay, Sen. Benjamin L. Cardin (D-Md.) opposed his confirmation, in part because of his stance on the bay.

Last month, 12 Democrats and five Republicans in the House wrote a letter to Trump urging him to maintain the bay cleanup budget.