The U.S. Bureau of Reclamation released 24-month projections this week forecasting that less Colorado River water will cascade down from the Rocky Mountains through Lake Powell and Lake Mead and into the arid deserts of the U.S. Southwest and the Gulf of California. Water levels in the two lakes are expected to plummet low enough for the agency to declare an official shortage for the first time, threatening the supply of Colorado River water that growing cities and farms rely on. It comes as climate change means less snowpack flows into the river and its tributaries. Hotter temperatures parch 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.
Water agency officials say they’re confident their preparation measures, including conservation and seeking out alternative sources, would allow them to withstand cuts if the drought lingers as expected.
“The study, while significant, is not a surprise. It reflects the impacts of the dry and warm conditions across the Colorado River Basin this year, as well as the effects of a prolonged drought that has impacted the Colorado River water supply,” officials from the Arizona Department of Water Resources and Central Arizona Project said in a joint statement.
In Nevada, the agency that supplies water to most states has constructed “straws” to draw water from further down in Lake Mead as its levels fall. It has also created a credit system where it can bank recycled water back into the reservoir without counting toward its allocation.
Colby Pellegrino, director of water resources for the Southern Nevada Water Authority, reassured customers that those preparation measures would insulate them from the effects of cuts. But she warned that more action was needed.
“It is incumbent upon all users of the Colorado River to find ways to conserve,” Pellegrino said in a statement.
The Bureau of Reclamation also projected that Lake Mead will drop to the point they worried could threaten electricity generation at Hoover Dam in the past. Hydropower serves millions of customers in Arizona, California, and Nevada.
To prepare for a future with less water, the bureau has spent 10 years replacing parts of five of the dam’s 17 turbines that rotate to generate power. Len Schilling, a dam manager with the bureau, said the addition of wide-head turbines allows the barrier to operate more efficiently at lower water levels. He said the turbines will generate power almost to a point called “Deadpool,” when there isn’t enough water for the dam to function.