Last Updated: May 15, 2023
The August 2022 24-Month Study projected the January 1, 2023 Lake Powell elevation to be less than 3,525 feet. Consistent with Section 6.D.1 of the Interim Guidelines, Lake Powell’s operation in WY 2023 is governed by the Lower Elevation Balancing Tier with an initial projected WY release volume of 7.00 million acre-feet (maf). Based on hydrologic conditions as of April 2023, in which the most probable inflow into Lake Powell is projected to be 11.30 maf (177 percent of average) during the 2023 April-July runoff period, Reclamation has determined that conditions are sufficient to release up to 9.50 maf from Lake Powell in WY 2023 consistent with Section 6.D.1 of the Interim Guidelines, but could be as low as 7.00 maf consistent with the Interim Guidelines and to protect Lake Powell from declining below elevation 3,525 feet at the end of December 2023. In addition, Reclamation has removed the operational neutrality of the 0.480 maf that was retained in Lake Powell under the May 2022 action, such that balancing releases are based on physical elevations of Lake Powell and Lake Mead.
Consistent with this operating approach and based on the most probable inflow forecast, the May 2023 24-Month Study projects a balancing release of 9.29 maf from Lake Powell in WY 2023; however, the actual release in WY 2023 will range between 7.00 and 9.50 maf and will depend on actual hydrology and reservoir conditions at Lake Powell and Lake Mead during the remainder of the water year. The projected release from Lake Powell in WY 2023 will be updated each month throughout the remainder of the water year. The modeling approach for 2024 and beyond will be consistent with the Interim Guidelines, based on projected physical elevations at Lake Powell and Lake Mead, and assume the 0.480 maf retained in Lake Powell under the May 2022 action was released as part of the WY 2023 balancing release only if the release volume is 7.48 maf or greater.
Reclamation will continue to carefully monitor hydrologic and operational conditions and assess the need for additional responsive actions and/or changes to operations. Reclamation will continue to consult with the Basin States, Basin Tribes, Mexico, and other partners on Colorado River operations to consider and determine whether additional measures should be taken to further enhance the preservation of these benefits, as well as recovery protocols, including those of future protective measures for both Lakes Powell and Mead.
The unregulated inflow volume to Lake Powell during April was 1,399 thousand acre-feet (kaf) (155 percent of average). The release volume from Glen Canyon Dam in April was 909 kaf. The end of April elevation and storage of Lake Powell were 3,524.99 feet (175 feet from full pool) and 5.54 million acre-feet (maf) (23 percent of live capacity), respectively.
To view the most current reservoir elevation projections, click on: Lake Powell Elevation Projections.
To view the most current monthly release projections, click on: Lake Powell Release Projections.
To view the 2023 progession of snowpack above Lake Powell, click on Lake Powell Snow Chart.
To view the current inflow forecast relative to past inflows, click on Lake Powell Inflow Forecast.
Hourly releases during May 2023 will fluctuate from a low of approximately 14,051 cfs during the early morning hours to a high of 18,909 cfs during the afternoon and evening hours and may follow a steady release pattern around 17,500 cfs, all within the May release volume of 1,088,000 acre-feet. The anticipated monthly release volume for June is anticipated to be 1,064,000 acre-feet and will be confirmed toward the end of May.
In addition to daily scheduled fluctuations for power generation, the instantaneous releases from Glen Canyon Dam may also fluctuate to provide 40 megawatts (MW) of system regulation. These instantaneous release adjustments stabilize the electrical generation and transmission system and translate to a range of about 1,300 cfs above or below the hourly scheduled release rate. Under system normal conditions, fluctuations for regulation are typically short lived and generally balance out over the hour with minimal or no noticeable impacts on downstream river flow conditions.
Releases from Glen Canyon Dam can also fluctuate beyond scheduled releases when called upon to respond to unscheduled power outages or power system emergencies. Depending on the severity of the system emergency, the response from Glen Canyon Dam can be significant, within the full range of the operating capacity of the power plant for as long as is necessary to maintain balance in the transmission system. Glen Canyon Dam currently maintains 30 mw (approximately 800 cfs) of generation capacity in reserve in order to respond to a system emergency even when generation rates are already high. System emergencies occur fairly infrequently and typically require small responses from Glen Canyon Dam. However, these responses can have a noticeable impact on the river downstream of Glen Canyon Dam.
Inflow Forecasts and Model Projections
The forecast for water year 2023 unregulated inflow to Lake Powell, issued on May 4, 2023, by the Colorado Basin River Forecast Center, projects that the most probable (median) unregulated inflow volume in water year 2023 will be 14.17 maf (148 percent of average).
In addition to the May 2023 24-Month Study based on the Most Probable inflow scenario, and in accordance with the Drought Response Operational Agreement (DROA)), Reclamation has conducted model runs in May to determine a possible range of reservoir elevations. The April 2023 24-Month Study probable maximum and May 2023 24-Month Study minimum probable inflow scenarios were used to determine the range of probable outcomes. The probable minimum and probable maximum model runs are conducted simultaneously in January, April, August, and October, or when necessary to incorporate changing conditions. The probable minimum inflow scenario reflects a dry hydrologic condition which statistically would be exceeded 90 percent of the time. The most probable inflow scenario reflects a median hydrologic condition which statistically would be exceeded 50 percent of the time. The probable maximum inflow scenario reflects a wet hydrologic condition which statistically would be exceeded 10 percent of the time. There is approximately an 80 percent probability that a future elevation will fall inside the range of the minimum and maximum inflow scenarios. Additionally, there are possible inflow scenarios that would result in reservoir elevations falling outside the ranges indicated in these reports.
The DROA coordination will continue until either (i) the minimum probable projected elevation remains above 3,525 feet for 24 months or (ii) the process moves to the next step when the most probable projected elevation indicates Powell elevations below 3,525 feet and a Drought Response Operations Plan is developed. This 2022 Plan is described above and available for review here: https://www.usbr.gov/dcp/droa.html.
The May forecast for water year 2023 ranges from a minimum probable of 12.81 maf (133 percent of average) to a forecasted maximum probable of 16.31 maf (170 percent of average) with the most probable forecast for water year 2023 of 14.17 maf (148 percent of average). There is a 10 percent chance that inflows could be higher than the current maximum probable forecast and a 10 percent chance that inflows could be lower than the minimum probable forecast.
Based on the current forecast of 14.17 maf unregulated inflow for water year 2023, the May 24-Month Study projects Lake Powell elevation will end water year 2023 near 3575.77 feet with approximately 8.96 maf in storage (37 percent of capacity). Note that projections of elevation and storage for water year 2023 have significant uncertainty at this point in the season. Projections of end of water year 2023 elevation using the May minimum and April maximum inflow forecast results are 3,570.24 feet and 3,606.71 feet, respectively. The annual release volume from Lake Powell during water year 2023 will be 9.29 maf under the Lower Elevation Balancing Tier and will balance the contents between Powell and Mead with annual release volumes from Glen Canyon Dam between 7.00 maf and 9.50 maf as determined under Section 6.D.1 and 7.D of the Interim Guidelines as determined by the Department of the Interior as described above.