How the Columbia River Treaty Got Tangled in Trump’s Feud With Canada

Caught up in the tariff spat between the United States and Canada is a little-known treaty that shapes the lives of millions of Americans and Canadians.

The 60-year-old treaty governs the water rushing down the Columbia River, which snakes from British Columbia through Montana, Idaho, Washington and Oregon, and provides the single largest source of hydropower in the United States. But parts of the treaty expired around the U.S. presidential election.

Negotiators were still weeks away from completing the details of an updated version of the treaty when President Joseph R. Biden Jr.’s term ended. Then a decade of talks crashed into President Trump’s hostility toward Canada. He called Canada the “51st state,” slapped tariffs on Canadian exports and fixated on tapping its water as a “very big faucet.”

In a contentious call in February with Canada’s prime minister at the time, Justin Trudeau, Mr. Trump included the treaty among the ways he said Canada had taken advantage of the United States. The implication was clear: The treaty could become a bargaining chip in a broader negotiation to remake the relationship between the two counties.

Prime Minister Mark Carney and Mr. Trump turned down the heat during their meeting at the White House last week. But the Trump administration has made even treaties with benefits for both sides feel like a negotiation on the edge of a knife. Mr. Trump’s erratic trade policies have thrown uncertainty into the future of the Pacific Northwest, creating new worries around everything from electricity to flood control.