As the West endures another year of unrelenting drought worsened by climate change, the Colorado River’s reservoirs have declined so low that major water cuts will be necessary next year to reduce risks of supplies reaching perilously low levels, a top federal water official said Tuesday.

Bureau of Reclamation Commissioner Camille Calimlim Touton said during a Senate hearing in Washington that federal officials now believe protecting “critical levels” at the country’s largest reservoirs — Lake Mead and Lake Powell — will require much larger reductions in water deliveries.

“A warmer, drier West is what we are seeing today,” Touton told the Senate Energy and Natural Resources Committee. “And the challenges we are seeing today are unlike anything we have seen in our history.”

The needed cuts, she said, amount to between 2 million and 4 million acre-feet next year.

For comparison, California is entitled to 4.4 million acre-feet of Colorado River […]