The Colorado River Basin – the area drained by the Colorado River and its tributaries – covers approximately 647,500 square kilometers (250,000 square miles) in seven states across western United States, supplying water to about 40 million people while supporting agriculture and natural ecosystems. According to a new study conducted by the University of California, Los Angeles (UCLA), from 2000 to 2021, climate change caused the loss of over 40 trillion liters (10 trillion gallons) of water in this basin.