As early as 2020, hydrologists forecast that the level of Lake Mead, the largest reservoir on the Colorado River, could drop low enough to trigger the first water shortages in its downstream states of Arizona, Nevada and California.
The three states in the river’s Lower Basin have long feared shortages. But the continued decline of Lake Mead reflects a reality they can no longer ignore: Demand for the river’s water, which supports 40 million people from Wyoming to California, has long outpaced the supply. On top of that, the supply is shrinking, as the spring snowmelt that once filled reservoirs becomes less reliable, and historically high temperatures evaporate the water that remains. Booming populations, drought and climate change will continue to compound the imbalance. The river’s flow has declined by nearly 20 percent in the last 15 years alone, and it could plummet another 55 percent before 2100, according to climate scientist Brad Udall at the Colorado Water Institute.