WASHINGTON (AP) — U.S. officials are expected to declare the first-ever water shortage from a river that serves 40 million people in the West.

The anticipated forecast Monday will mean some Arizona farmers get less water from the Colorado River next year, forcing them to make adjustments.

A prolonged drought made worse by climate change has led to record low water levels at Lake Mead, one of the river's reservoirs.

The situation highlights the challenges for a region that's also growing in population.

The Colorado River provides drinking water, irrigation for farms and hydropower to seven Western states and parts of Mexico.