Federal officials say it may be necessary to reduce water deliveries to Colorado River users to prevent the shutdown of Glen Canyon Dam.
The dam, located on the Arizona-Utah border, supplies hydropower to some 5 million customers across the U.S. West.
Officials had hoped snowmelt would buoy Lake Powell to ensure continued operation of the dam. But snow is already melting, and hotter-than-normal temperatures along with prolonged drought are further shrinking the lake.
The Interior Department has proposed holding back water in the lake to maintain power production.
The agency is asking for feedback from the seven states that rely on the river by April 22.