WASHINGTON – The Bureau of Reclamation today released its April 24-Month Study, which includes an increase to downstream flows from Lake Powell to Lake Mead of up to 9.5 million acre-feet (maf) this water year (Oct. 1, 2022 through Sept. 30, 2023).
Glen Canyon Dam’s annual release volume for water year 2023 was initially set at 7.0 maf, based on the August 2022 24-Month Study, and is now projected to increase to up to 9.5 maf because of high snowpack this winter and projected runoff in the Colorado River Basin this spring. The actual annual release volume from Glen Canyon Dam is adjusted each month throughout the water year and is determined based on the observed inflow to Lake Powell and the storage contents of Lake Powell and Lake Mead.
While this water year’s projections are above average, the Colorado River Basin is experiencing severe drought conditions and system reservoirs remain at historically low levels. In response to this historic drought, Reclamation recently released a draft Supplemental Environmental Impact Statement to potentially revise the current interim operating guidelines for the near-term operation of Glen Canyon and Hoover Dams.
“This winter’s snowpack is promising and provides us the opportunity to help replenish Lakes Mead and Powell in the near-term — but the reality is that drought conditions in the Colorado River Basin have been more than two decades in the making,” said Commissioner Camille Calimlim Touton. “Despite this year’s welcomed snow, the Colorado River system remains at risk from the ongoing impacts of the climate crisis. We will continue to pursue a collaborative, consensus-based approach to conserve water, increase the efficiency of water use, and protect the system’s reservoirs from falling to critically low elevations that would threaten water deliveries and power production.”
Lake Powell is currently operating in the Lower Elevation Balancing Tier, and Reclamation is required to “balance the contents” of Lake Mead and Lake Powell, as outlined in Section 6.D.1 of the Colorado River Interim Guidelines for Lower Basin Shortages and Coordinated Operations for Lake Powell and Lake Mead (2007 Interim Guidelines).
Reclamation utilized the Colorado Basin River Forecast Center’s (CBRFC) April forecasts and other relevant factors such as Colorado River system storage and reservoir elevations to make balancing adjustments to Lake Powell operations.
The CBRFC’s April through July unregulated inflow forecast for Lake Powell is 11.3 maf (177% of average) — an increase of 3.3 maf from March, which was 125% of average. Reclamation’s April 24- Month Study projects Lake Powell’s elevation at 3,576.50 feet at the end of the water year (Sept. 30, 2023). This is approximately 40 feet higher and 2.74 maf of additional storage than projected in the August 2022 Most Probable 24-Month Study, which was used to set the annual operations for Lake Powell and Lake Mead.
For the past several years, Reclamation has had to take drought response operations, including modifying monthly releases from Glen Canyon Dam, to keep water in Lake Powell and help prevent it from dropping to critically low elevations.
The higher annual release volume for the remainder of this water year is inclusive of water previously kept in Lake Powell:
- 480,000 acre-feet of water kept in Lake Powell by reducing the annual release volume in water year 2022 from 7.48 maf to 7.0 maf
- 523,000 acre-feet of water held back this winter to increase Lake Powell elevations during the lowest point in the water year until post-runoff months of May through September
Reclamation has already increased the monthly release volume for April from Glen Canyon Dam from 552,000 acre-feet to 910,000 acre-feet to be better positioned to release up to 9.5 maf by the end of the water year (Sept. 30, 2023). Monthly releases for May through September will also be adjusted as needed.
Reclamation will take advantage of April’s higher water releases and will conduct a 72-hour high-flow release from Glen Canyon Dam later this month. This will involve a release of water from Glen Canyon Dam that is more rapid than normal — up to 39,500 cfs during its peak — to move sediment stored in the river channel and redeposit it onto beaches, which will benefit conditions at Grand Canyon National Park and aid in management of invasive species in the Colorado River. The release will not change the annual release volume of up to 9.5 maf from the dam.
"The steps announced by the Bureau of Reclamation today respond adaptively to the unusual conditions this year with an action grounded in the sound science of the Grand Canyon Monitoring and Research Center scientists,” said National Park Service’s Grand Canyon National Park Superintendent Ed Keable. “This release is critical to rebuild the sandbars and protect the archeological resources and restore the camping beaches in the canyon in compliance with the 1992 Grand Canyon Protection Act.”
Based on the April 24-Month Study, Lake Mead’s elevation is also projected to improve in calendar year 2023, with a projected end of calendar year elevation of 1,068.05 feet — approximately 33 feet higher than the March 24-Month Study. With this improvement in Lake Mead’s elevation, a mid-year review of Lake Mead operations is not expected in 2023.
While improved hydrology and projected forecasts have provided an opportunity to recover upstream reservoir storage and use the higher runoff to take positive action in the Grand Canyon, the Colorado River system remains at risk, with Lake Powell and Lake Mead at a combined storage capacity of just 26%.
Reclamation is committed to protecting and sustaining the system and is undertaking an expedited, supplemental process to revise the current interim operating guidelines for the Glen Canyon and Hoover Dams. This process will provide the alternatives and tools needed to address the likelihood of continued low-runoff conditions and reduced water availability across the basin over the next two years. This draft SEIS is available for public review and comment until May 30, 2023. The document can be found on the project website, www.usbr.gov/ColoradoRiverBasin/SEIS.html, as well as information on how to submit written comments and when virtual public meetings will be held.
Additional information about the planned high-flow release will be posted and updated online at: https://www.usbr.gov/uc/progact/amp/ltemp.html.
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The Bureau of Reclamation is a federal agency under the U.S. Department of the Interior and is the nation's largest wholesale water supplier and second largest producer of hydroelectric power. Our facilities also provide substantial flood control, recreation opportunities, and environmental benefits. Visit our website at https://www.usbr.gov and follow us on Twitter @USBR; Facebook @bureau.of.reclamation and @coloradoriverbasin; LinkedIn @Bureau of Reclamation; Instagram @bureau_of_reclamation; and YouTube @reclamation.
