It comes as climate change means less snowpack flows into the river and its tributaries. Hotter temperatures dry soil and cause more river water to evaporate as it streams through the drought-plagued American West.
The agency’s models project, Lake Mead, will fall below 1,075 feet (328 meters) for the first time in June 2021. That’s the level that prompts a shortage declaration under agreements negotiated by seven states that rely on Colorado River water: Arizona, California, Colorado, Nevada, New Mexico, Utah, and Wyoming.
The April projections, however, will not have a binding impact. Federal officials regularly issue long-term forecasts but use those released each August to decide how to allocate river water. If projections don’t improve by then, the Bureau of Reclamation will declare a Level 1 shortage condition. The cuts would be implemented in January.
Arizona, Nevada, and Mexico have voluntarily given up water under a drought contingency plan for the river signed in 2019. A shortage declaration would subject the two U.S. states to their first mandatory reductions. Both rely on the Colorado River more than any other water source, and Arizona stands to lose roughly one-third of its supply.