The U.S. government released projections Wednesday of an even more troubling outlook for a river that serves 40 million people in the American West.
The forecast, looking ahead five years, shows increased chances of both Lake Mead and Lake Powell dropping to critically low levels compared to forecasts the federal government made four months ago. The increased risk is particularly evident for Lake Powell, which stores water for release to Lake Mead and the rest of the river's Lower Basin.
The new forecasts from the U.S. Bureau of Reclamation come barely a month after the agency declared the first-ever shortage on the river. That shortage will cut Arizona’s share of water for the Central Arizona Project by nearly one-third and will take lesser swipes at Colorado River supplies owned by Nevada and Mexico.
The bureau’s latest five-year forecast says:
Lake Mead, now at around 1,067 feet above sea level, stands a 41% chance of falling below 1,025 feet by Dec. 31, 2025. At that level, under the terms of a two-year-old Drought Contingency Plan, cities and tribes in Arizona will take the worst cuts now planned for the CAP. Tucson’s cut would be much less than those suffered by many Phoenix-area cities and by several tribes.
The odds are much higher -- 66%-- of Mead falling below 1,025 during any particular month of 2025, the bureau's forecast shows, although the cut planned under the drought plan won't take effect unless the lake is below that level at year's end.
Lake Mead has a 22% chance of falling below 1,000 feet in any given month of 2025 and 2026. At 895 feet, Mead would be at “dead pool,” a point where no water could be released to downstream users.
Lake Powell faces a sharply higher chance — ranging from 25% to 34% — than previously forecast of falling below 3,490 feet in any given month from 2023 to 2026. If the lake falls below 3,490 feet, Glen Canyon Dam could no longer generate power. For 2022, there's a 3% chance of that happening.
An almost 90% chance is projected of Lake Powell falling to 3,525 feet during a given month next year. That elevation provides a 35 vertical-foot buffer designed to minimize the risk of dropping below what federal officials call the “minimum power pool” elevation of 3,490 feet. Powell would hit "dead pool" at 3,370 feet.
The bureau’s most recent earlier forecast for the reservoirs, released in June, found a 22% chance of Powell falling below 3,490 in 2026 and a 5 to 17% chance of the lake plunging that low from 2023 to 2025.
It also saw a 58% chance of Mead falling below 1,025 in any given month by 2025 and a 62% chance of that by 2026. When the forecast looked only at the end of those years, the risks of Mead falling below 1,025 was at most 38 percent.
While Lake Mead on the Nevada-Arizona border is key for the three lower Colorado River basin states, including California, Lake Powell on the Arizona-Utah border is the guide for Colorado, New Mexico, Wyoming and Utah in the upper basin. Smaller reservoirs upstream of Lake Powell have been releasing water into the massive lake so it can continue producing hydropower.
But any bump from the releases that started this summer is not factored into the five-year projections, which take effect in 2022, the Bureau of Reclamation said. The forecasts do assume, however, that the 181,000 acre-feet the bureau plans to release from the upstream reservoirs will be in Lake Powell at the start of 2022.
“The latest outlook for Lake Powell is troubling,” Wayne Pullan, the bureau’s director for the upper basin, said in a statement. “This highlights the importance of continuing to work collaboratively with the basin states, tribes and other partners toward solutions.”
Lake Powell and Lake Mead, the largest manmade reservoirs in the U.S., largely rely on melted snow. They have been hard hit by persistent drought amid climate change, characterized by a warming and drying trend in the past 30 years. The river's average annual flow since 2000 is about 19% lower than it was during the 20th century dating back to 1906, when records started being kept.
Both have dipped to historic lows. The lakes had a combined capacity of 39% on Wednesday, down from 49% at this time last year, the Bureau of Reclamation said. Both reservoirs were nearly full in 2000.
This year's spring-summer runoff into Lake Powell was its third-lowest on record, at 26% of average.
The seven states that rely on the Colorado River signed off on a drought plan in 2019 to help prop up the lakes by voluntarily leaving more water in Lake Mead. All agree more needs to be done and are discussing what will replace a set of guidelines for the river and the overlapping drought plan when they both expire in 2026.
The Lower Basin states of Arizona, California and Nevada are also meeting separately to try to come up with shorter-term ways of saving water that could take effect before 2026.
“Climate change and aridification are permanently changing our landscapes, threatening our way of life, jeopardizing our ability to produce hydropower and placing further strain on our communities. This is the reality every Arizonan is facing,” said a conservationist group that calls itself the Water for Arizona Coalition.
“The possibility of severe declines at Lakes Mead and Powell should be a wake-up call to anyone who wants their children or grandchildren to be able to survive and thrive in the West,” the coalition said.
The new federal forecast underscores the need for additional actions beyond the 2019 drought plan and the interim federal guidelines for the river approved in 2007 “to be taken to enhance our efforts to protect Lake Mead, Lake Powell and the Colorado River system overall,” said Tom Buschatzke, director of the Arizona Department of Water Resources.