Lake Mead
NPS photo
Modeling results assist drought response planning in the Colorado River Basin
September 27, 2021 - COLORADO RIVER BASIN - The Bureau of Reclamation last week released updated modeling projections of major reservoir levels within the Colorado River system over the next five years. These projections are used by Reclamation and water users in the basin for future water management planning. The new projections 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.
Today’s announcement comes as the Administration pursues a whole-of-government approach to drought mitigation via the Interagency Drought Relief Working Group, co-chaired by the Department of the Interior. The Working Group is coordinating with partners across the federal government, providing assistance to impacted communities, and developing long-term solutions to climate change.
Lake Powell Projections
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 Projections
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.”
To view the most recent Colorado River system projections, visit https://www.usbr.gov/lc/region/g4000/riverops/crss-5year-projections.html.
Source: Bureau of Reclamation
