The Bureau of Reclamation (BOR) released updated projections showing an elevated risk for Lake Powell and Lake Mead reaching critically low elevations.
The announcement comes after BOR implemented its first-ever water cutbacks for Arizona, Nevada and Mexico due to drought and low runoff conditions in the Colorado River Basin. Both lakes have dropped to historic low water levels, with a combined capacity of 39 percent, down from 49 percent at this time last year, the BOR said.
The agency projects Lake Powell could fall below the minimum power pool as early as July 2022, should drought conditions continue. The minimum power pool is the level needed for the Glen Canyon Dam to be able to produce hydropower, which is not possible if the lake’s elevation drops below 3,490 feet above sea level. The BOR provides a 35 vertical-foot buffer, designed to minimize the risk of dropping below the minimum power pool elevation of 3,525 feet, and projects a 90 percent chance it will be reached. Beyond 2022, the chance Lake Powell could fall below the minimum power pool ranges from about 25-35 percent.
As of Sept. 20, the water elevation at Glen Canyon Dam was 3,546 feet, more than 153 feet below the “full pool” of 3,700 feet.
Glen Canyon normally produces 1,320 megawatts of hydropower, or enough for 5.8 million customers in the inland West, but is currently producing 870 megawatts, according to Rob Manning, BOR chief of public affairs. Every foot of lake level decline means about 3 megawatts of lost capacity.
“The latest outlook for Lake Powell is troubling,” said BOR’s Upper Colorado Basin Regional Director Wayne Pullan in a statement. “This highlights the importance of continuing to work collaboratively with the Basin states, Tribes and other partners toward solutions.”
As part of the 2019 Colorado River Drought Contingency Plan, BOR started water deliveries to Lake Powell from the upper reservoirs of Blue Mesa in Gunnison County, CO; Flaming Gorge in Wyoming; and the Navajo, which straddles the Colorado/New Mexico border, for a total of 181,000 acre-feet between the three reservoirs. However, BOR did not factor the releases into the five-year projections, BOR stated.
For Lake Mead, BOR projects there is as high as a 66 percent chance that in 2025, the lake’s level could drop to 1,025 feet. Currently, the lake is in Tier 1 shortage condition for the first time, resulting in reduced water deliveries to Arizona, Nevada and Mexico.
A drop to 1,025 feet would result in Tier 3 conditions, which would mean a reduction of 480,000 acre-feet in Arizona alone and would impact the Central Arizona Project. The Central Arizona Project brings Colorado River water to the cities of Phoenix and Tucson.
Manning said the drop in the lake level has resulted in a reduction of hydropower by 25 percent from its usual capacity of 2,074 megawatts to 1,567 megawatts. The Hoover Dam needs a power pool minimum of 950 feet to produce power, and Lake Mead’s elevation was 1,067 feet as of Aug. 31. BOR stated there is a 22 percent chance of the reservoir elevation dropping to 1,000 feet in 2025.
BOR stated if levels drop below 895 feet in Lake Mead, water will become inaccessible to states downstream.
According to the BOR, an exceptionally dry spring in 2021 in the Upper Basin of the Colorado River has led to Lake Powell receiving just 26 percent of normal April to July runoff, despite near-average snowfall last winter.
“We’re providing detailed information on our modeling and projections to further generate productive discussions about the future of Lake Powell and Lake Mead based on the best data available,” said BOR’s Lower Colorado Basin Regional Director Jacklynn Gould. “Being prepared to adopt further actions to protect the elevations at these reservoirs remains a Reclamation priority and focus.”
The National Oceanic and Atmospheric Administration (NOAA) Drought Task Force released a report stating that from January 2020 to August 2021, the six states in the Southwest “have been exceptional in the observational climate record since 1895” with the lowest precipitation and near-record temperature levels.
The NOAA said despite monsoon rains in August, it would take several seasons (or years) of above-average rain and high elevation snow to refill rivers, soils and reservoirs across the region. “This suggests that for much of the U.S. Southwest, the present drought will last at least into 2022, potentially longer,” NOAA said. — Charles Wallace, WLJ editor
