The US Geological Survey and the Bureau of Reclamation found that Lake Powell had an average loss in storage capacity of 33,270 acre-feet, or 11 billion gallons, per year between 1963 and 2018 due to water loss due to an intense multiyear drought.
That is enough water to fill the Reflecting Pool on the National Mall about 1,600 times.
The reservoir's capacity is shrinking because of sediments from the Colorado and San Juan rivers, according to the report. The sediments that settle at the bottom of the reservoir decrease the amount of water the reservoir can hold.
According to the Bureau of Reclamation, Lake Powell was about 25% full as of Monday.
National Oceanic and Atmospheric Administration drought experts said last week these conditions are expected to continue in the coming months if not worsen. Lake Powell is an important reservoir in the Colorado River Basin. Both Lake Powell and nearby Lake Mead, the nation's largest reservoir, have drained at an alarming rate. In August of this year, the federal government declared a water shortage on the Colorado River for the first time after Lake Mead's water level plunged to unprecedented lows, triggering water consumption cuts for states in the Southwest that began in January. Last week, Lake Powell fell below the critical threshold of 3,525 feet above sea level, sparking further concerns about water supply and hydropower generation millions of people in the West rely on for electricity. The significance of the dwindling water supply along the Colorado can't be overstated. The system provides water for more than 40 million people living in seven western states and Mexico. Lake Powell and Mead provide a critical supply of drinking water and irrigation for many in the region, including rural farms, ranches and native communities. Tanya Trujillo, assistant secretary for water and science at the US Department of Interior, said in a statement that it is important to have the best-available scientific information like this report to provide a clear understanding of water availability in Lake Powell. The Colorado River system is facing multiple challenges, including the effects of a 22 year-long drought and the increased impacts of climate change.