Lake Powell, the second largest human-made reservoir in the US, has lost nearly 7% of its potential storage capacity since 1963 when Glen Canyon Dam was built, according to a new report.
Between 1963 and 2018 Lake Powell faced an average annual loss of 33,270 acre-feet or 11 billion gallons of water due to an intense multiyear drought, according to the US Geological Survey and the Bureau of Reclamation.
That is enough water to fill the Reflecting Pool on the National Mall about 1,600 times.
The report says the reservoir's capacity is shrinking because of sediments flowing in from the Colorado and San Juan rivers. The sediments settle at the bottom of the reservoir and decrease the amount of water the reservoir can hold.
As of Monday, Lake Powell was almost 25% full, according to data from the Bureau of Reclamation.
It is bad news for a region already facing water shortages and extreme wildfires due to the drought. National Oceanic and Atmospheric Administration drought experts said last week that these conditions are expected to continue, if not worsen in the coming months.
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, 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.
Lake Powell fell below the critical threshold of 3,525 feet above sea level last week, 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 with the US Department of Interior, said in a statement that it is important that we 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 faced with multiple challenges, including the effects of a 22 year-long drought and the increased impacts of climate change.