Last Updated: November 15, 2023
The unregulated inflow volume to Lake Powell during October was 324 thousand acre-feet (kaf) (72 percent of average). The release volume from Glen Canyon Dam in October was 500 kaf. The end of October elevation and storage of Lake Powell were 3,572.71 feet (127 feet from full pool) and 8.72 million acre-feet (maf) (37 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 2024 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.
The August 2023 24-Month study projects the January 1, 2023, Lake Powell elevation to be less than 3,575 feet and at or above 3,525 feet and the Lake Mead elevation to be at or above 1,025 feet. Consistent with Section 6.C.1 of the Interim Guidelines the operational tier for Lake Powell in water year 2024 is the Mid-Elevation Release Tier and the water year release volume from Lake Powell is 7.48 maf.
October release volume will be 480,000 acre-feet and hourly releases will fluctuate from a low of approximately 5,000 cubic feet per second (cfs) during the early morning hours to a high of 9,320 cfs during the afternoon and evening hours. The anticipated monthly release volume for November is anticipated to be 500,000 acre-feet and will be confirmed toward the end of October.
November release volume will be 500,000 acre-feet and hourly releases will fluctuate from a low of approximately 5,280 cubic feet per second (cfs) during the early morning hours to a high of 9,790 cfs during the afternoon and evening hours. The anticipated monthly release volume for December is anticipated to be 600,000 acre-feet and and hourly releases will fluctuate from a low of approximately 6,157 cubic feet per second (cfs) during the early morning hours to a high of 11,558 cfs during the afternoon and evening hours on the weekdays, the Sunday minimum will be 5,022 cfs. This will be confirmed toward the end of November.
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 normal system 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 1,300 cfs) of generation capacity in reserve in order to respond to a system emergency even when generation rates are already high. System emergencies occur 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 2024 unregulated inflow to Lake Powell, issued on November 1, 2023, by the Colorado Basin River Forecast Center, projects that the most probable (median) unregulated inflow volume in water year 2024 will be 8.62 maf (90 percent of average).
In addition to the November 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 November to determine a possible range of reservoir elevations. The November 2023 24-Month Study probable most and minimum and the October 2023 maximum 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 current Plan is described above and available for review here: https://www.usbr.gov/dcp/droa.html.
The November forecast for WY 2024 ranges from a minimum probable of 5.57 maf (58% of average) to a forecasted November 24-Month Study maximum probable of 15.42 maf (163 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 8.62 maf unregulated inflow for water year 2024, the November 24-Month Study projects Lake Powell elevation will end calendar year 2024 near 3579.55 feet with approximately 9.26 maf in storage (40 percent of capacity). Note that projections of elevation and storage for calendar year 2024 have significant uncertainty at this point in the season. Projections of end of calendar year 2024 elevation using the November minimum and October maximum inflow forecast results are 3,543.88 feet and 3,657.44 feet, respectively. The annual release volume from Lake Powell during water year 2024 is 7.48 maf under the Mid-Elevation Release Tier as determined under Section 6.C.1 of the Interim Guidelines as determined by the Department of the Interior as described above.
Upper Colorado River Basin Hydrology
Upper Colorado River Basin regularly experiences significant year to year hydrologic variability. The 30-year average was updated in October 2022 from 1981 through 2010 to 1991 through 2020. Shifting the period of record decreased the average unregulated inflow 1.20 maf. The period 2000-2022 is the lowest 23-year period since the closure of Glen Canyon Dam in 1963, with an average unregulated inflow of 8.29 maf, or 93 percent of the 30-year average (1991-2020). (For comparison, the 1991-2020 total water year average is 9.60 maf.) The unregulated inflow during the 2000-2022 period has ranged from a low of 2.64 maf (28 percent of average) in water year 2002 to a high of 15.97 maf (166 percent of average) in water year 2011. In water year 2021 unregulated inflow volume to Lake Powell was 3.50 maf (36 percent of average), the second driest year on record above 2002. Under the current most probable forecast, the total water year 2023 unregulated inflow to Lake Powell is projected to be 8.62 maf (90 percent of average).
At the beginning of water year 2024, total system storage in the Colorado River Basin was 25.27 maf (43 percent of 58.48 maf total system capacity). This is an increase of 5.72 maf over the total storage at the beginning of water year 2023 when total system storage was 19.55 maf (33 percent of capacity). Since the beginning of water year 2000, total Colorado Basin storage has experienced year to year increases and decreases in response to wet and dry hydrology, ranging from a high of 94 percent of capacity at the beginning of 2000 to the beginning of water year 2023 with 19.55 maf (33 percent of capacity). Based on current inflow forecasts, the current projected end of water year 2024 total Colorado Basin reservoir storage is approximately 25.13 maf (43.0 percent of total system capacity). The actual end of water year 2024 system storage may vary from this projection, primarily due to uncertainty regarding this season’s runoff and reservoir inflow.