After years of severe drought compounded by climate change, the water level in Lake Powell, the second-largest reservoir on the Colorado River, has dropped to just 24 percent of full capacity and is continuing to decline to levels not seen since the reservoir was filled in the 1960s.

In an effort to boost the shrinking reservoir, the federal government announced this week that it plans to hold back water to reduce risks of the lake falling below a point at which Glen Canyon Dam would no longer generate electricity.

“Today’s decision reflects the truly unprecedented challenges facing the Colorado River Basin and will provide operational certainty for the next year,” Tanya Trujillo, Department of Interior assistant secretary of water and science, said in a statement announcing the measures.

It is the first time that the U.S. Bureau of Reclamation has invoked its authority to change its operations at Glen Canyon Dam on the Arizona-Utah border. The agency said the plan protects the dam’s ability to generate hydropower and the facility’s infrastructure and will ensure water supplies continue to be available for the nearby city of Page, Ariz., and a portion of the Navajo Nation.

The federal government’s plan aims to reduce the risks of Lake Powell falling to critically low levels. The measures will involve releasing about 500,000 acre-feet of water from Flaming Gorge Reservoir, which is located upstream, and leaving an additional 480,000 acre-feet in Lake Powell by reducing the volume of water released from Glen Canyon Dam this year.

For comparison, California, Arizona and Nevada used 6.8 million acre-feet of Colorado River water in 2020.

The federal government last month proposed the plan to combat declines in Lake Powell to the states in the Colorado River Basin.

In a letter, Trujillo asked the states for their input on the plan.

“We believe that additional actions are needed to reduce the risk of Lake Powell dropping” below a level of 3,490 feet above sea level, Trujillo said in the letter.

Trujillo warned that below the threshold of 3,490 feet, Glen Canyon Dam’s facilities face “unprecedented operational reliability challenges, water users in the Basin face increased uncertainty, downstream resources could be impacted, the western electrical grid would experience uncertain risk and instability.”

The level of the reservoir on the Arizona-Utah border now stands about 32 feet above that threshold.

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