The Remnants – Lake Powell water levels continue to drop, and a new report released by the Bureau of Reclamation projects the possibility America’s second-biggest dam could be too low to produce electricity by July 2022.
Glen Canyon Dam can generate 5 billion kilowatt-hours per year at full capacity, enough to run about 470,000 average American homes. But if it sinks below 3,490 feet, that generation goes away.
The projections show a 25 to 35 % chance that will happen, but the reservoir has a 90 % chance of sinking below the threshold the Bureau likes to maintain to be safe. They mark that at 3,525 feet.
Lake Powell was at 3,546 feet above sea level on September 23. In July, the Bureau started releasing water from large reservoirs upstream, including Flaming Gorge and Navajo, in order to slow the losses in Powell.
The new long-term projections don’t show the lake sinking below the level known as “Dead Storage Pool,” or simply “Dead Pool,” which is 3,370 feet. At that point, the mechanisms allowing for the control of streamflow are no longer operative, meaning the reservoir ceases to serve its purpose for water storage and distribution.
As North America approaches the end of the 2021 water year, the two largest reservoirs in the United States stand at their lowest levels since they were first filled.
Lake Powell water level drops
After two years of intense drought and two decades of long-term drought in the American Southwest, government water managers have been forced to reconsider how supplies will be portioned out in the 2022 water year.
Straddling the border of southeastern Utah and northeastern Arizona, Lake Powell is the second largest reservoir by capacity in the United States. In July 2021, water levels on the lake fell to the lowest point since 1969 and have continued dropping.
As of September 20, 2021, the water elevation at Glen Canyon Dam was 3,546.93 feet, more than 153 feet below “full pool” (elevation 3,700 feet). The lake held just 30 percent of its capacity.
To compensate, federal managers started releasing water from upstream reservoirs to help keep Lake Powell from dropping below a threshold that threatens hydropower equipment at the dam.
Lake Powell projections by US Bureau of Reclamation
At Lake Powell, the projections indicate the potential of falling below minimum power pool as early as July 2022 should extremely dry hydrology continue into next year. Beyond 2022, the chance Lake Powell could fall below minimum power pool ranges from about 25% to 35%.
Elevation 3,525 feet, the target elevation in Lake Powell, has an almost 90% chance of being reached next year. That target elevation provides a 35 vertical-foot buffer designed to minimize the risk of dropping below the minimum power pool elevation of 3,490 feet and balances the need to protect the infrastructure at Glen Canyon Dam and meet current operational obligations to the Lower Basin States of Arizona, California and Nevada.
“The latest outlook for Lake Powell is troubling,” said Reclamation’s Upper Colorado Basin Regional Director Wayne Pullan. “This highlights the importance of continuing to work collaboratively with the Basin States, Tribes and other partners toward solutions.”
After consultation with – and acknowledgement from – all seven Basin States and other partners, under the emergency provisions of the 2019 Drought Response Operations Agreement (DROA), Reclamation started supplemental water deliveries in July 2021 to Lake Powell from the upper reservoirs of Flaming Gorge, Blue Mesa and Navajo. Those supplemental deliveries will provide up to an additional 181 thousand acre-feet of water to Lake Powell by the end of the 2021.
As the Upper Basin States continue to work towards the development of a Drought Operations plan that will govern potential future supplemental deliveries, previous modeling assumptions regarding any additional or continued DROA releases have been removed to provide a clearer representation of future risk. The removal of these assumptions was the main contributor in the increase in risk between the last set of projections released in June of this year.
Lake Mead water level sinks
Downstream in the Colorado River water management system, Lake Mead is filled to just 35 percent of capacity. More than 94 percent of the land area across nine western states is now affected by some level of drought, according to the September 23 report from the U.S. Drought Monitor.
In an announcement on September 22, the U.S. Bureau of Reclamation (USBR) explained that updated hydrological models for the next five years “show continued elevated risk of Lake Powell and Lake Mead reaching critically-low elevations as a result of the historic drought and low-runoff conditions in the Colorado River Basin. At Lake Powell, the projections indicate the potential of falling below minimum power pool as early as July 2022 should extremely dry hydrology continue into next year.”
Minimum power pool refers to an elevation—3,490 feet—that water levels must remain above to keep the dam’s hydropower turbines working properly.
With the entire Lower Colorado River water storage system at 39 percent of capacity, the Bureau of Reclamation recently announced that water allocations in the U.S. Southwest would be cut over the next year.
“Given ongoing historic drought and low runoff conditions in the Colorado River Basin, downstream releases from Glen Canyon Dam and Hoover Dam will be reduced in 2022 due to declining reservoir levels,” the USBR statement said. “In the Lower Basin the reductions represent the first “shortage” declaration—demonstrating the severity of the drought and low reservoir conditions.”
Lake Powell projections by US Bureau of Reclamation
At Lake Mead, today’s projections indicate the chance of Lake Mead declining to elevation 1,025 feet (the third shortage trigger) is as high as 66% in 2025, and that there is a 22% chance of the reservoir elevation dropping to 1,000 feet the same year.
Reclamation continues to work with all seven Colorado River Basin States to address current conditions in the Colorado River Basin.
“This five-year probability table underscores the need for additional actions beyond the 2007 Guidelines and the 2019 Drought Contingency Plan 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.
Most of the flow of the Colorado River originates in the Rocky Mountains. The Upper Basin experienced an exceptionally dry spring in 2021, with April to July runoff into Lake Powell totaling just 26% of average, despite near-average snowfall last winter. Total Colorado River system storage today is 39% of capacity, down from 49% at this time last year.
Today’s release also includes updated presentations that utilize additional forecast information to improve public understanding of Reclamation’s future hydrologic projections. In keeping with its commitment to better inform all water users and the public regarding the hydrologic tools available, Reclamation has added in-depth information on its website about modeling and projections in the Colorado River system. A new interactive tool also allows users to explore projected reservoir conditions under a range of inflow forecasts.
“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 Reclamation’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.”
Colorado River Basin management
The Colorado River basin is managed to provide water to millions of people—most notably the cities of San Diego, Las Vegas, Phoenix, and Los Angeles—and 4 to 5 million acres of farmland in the U.S. and Mexico.
Water is allotted through laws like the 1922 Colorado River Compact and by a recent drought contingency plan announced in 2019.
In a report and op-ed released on September 22, members of a NOAA Drought Task Force offered some context for the low water levels across the region.
“Successive dry winter seasons in 2019-2020 and 2020-2021, together with a failed 2020 summer southwestern monsoon, led precipitation totals since January 2020 to be the lowest on record since at least 1895 over the entirety of the Southwest.
“At the same time, temperatures across the six states considered in the report (Arizona, California, Colorado, Nevada, New Mexico and Utah) were at their third highest on record. Together, the exceptionally low precipitation and warm temperatures reduced snowpack and increased evaporation of soil moisture, leading to a persistent and widespread drought over most of the American West.“