The US state of Nevada has sued the administration of President Donald Trump over a federal plan requiring the state and two others to reduce Colorado River water use, marking the first legal challenge to Washington’s effort to prevent the river from reaching a critical point.

In its federal court filing on Monday, Nevada said the Interior Department’s drought management plan could cause “devastating environmental, socioeconomic, and health and human safety impacts to southern Nevada and its citizens.”

The plan was created after the seven Colorado River states failed to agree on how to respond to worsening shortages, according to The Washington Post.

The dispute centers on a river that supplies about 40 million people in the southwestern United States and Mexico. Nevada officials said the proposed reductions could cut as much as 71% of the state’s annual allocation. The river provides roughly 90% of the water used by Las Vegas and surrounding communities.

“This isn’t about political posturing,” Nevada Governor Joe Lombardo said. “This is a matter of survival for a community that represents about two-thirds of our state’s citizens and the lion’s share of its economy.”

Years of overuse and a severe drought worsened by climate change have pushed the river into crisis. Federal data show this year’s flow is about 37% of average, while Lakes Powell and Mead have reached record-low levels.

The federal plan requires the US states of Arizona, California, and Nevada to reduce use by about 20% over the next two years. It also allows for deeper cuts later if shortages persist, while imposing no mandatory reductions on the Upper Basin states.

Nevada’s lawsuit argues the plan violates rules governing the river and fails to adequately account for the economic consequences of reducing urban water supplies.