Last Updated: May 17, 2022The Bureau of Reclamation announced on May 3, 2022, two separate urgent drought response actions that will help prop up Lake Powell by nearly 1 million acre-feet (maf) of water over the next 12 months (May 2022 through April 2023). To protect Lake Powell, more water will flow into the lake from upstream reservoirs and less water will be released downstream:
- Under a Drought Contingency Plan adopted in 2019, approximately 500 thousand acre-feet (kaf) of water will come from Flaming Gorge Reservoir, located approximately 455 river miles upstream of Lake Powell.
- Another 480 kaf will be left in Lake Powell by reducing Glen Canyon Dam’s annual release volume from 7.48 maf to 7.0 maf, as outlined in the 2007 Interim Guidelines that control operations of Glen Canyon Dam and Hoover Dam.
The Department of the Interior is conducting the fifth experimental flow at Glen Canyon Dam since implementing its Long-Term Experimental and Management Plan (LTEMP). The goal is to provide enhanced habitat for the lifecycle of aquatic insects that are the primary food source for fish in the Colorado River.
Experiments under LTEMP consist of four different flow regimes: high flows, macroinvertebrate flows (bug flows), trout management flows, and low summer flows. Collaborative discussions among technical experts resulted in a decision to begin this fourth consecutive year of the bug flow experiment on May 1 and continue through August 31, 2022. It will slightly modify the schedule and flow rates of water releases from Lake Powell through Glen Canyon Dam, Arizona. The normally scheduled monthly and weekly release volumes will not be affected.
Flows during the experiment will include steady weekend water releases with routine hydropower production flows on weekdays that include normal hourly changes in release rates. Those steady weekend flows are expected to provide favorable conditions for aquatic insects to lay and cement their eggs to rocks, vegetation, and other materials near the river’s edge. Steady weekend flows will be relatively low, within two inches of typical weekday low water levels. It is unlikely casual recreational river users will notice the changes in water levels. Hourly releases in May 2022 will fluctuate from a low of approximately 8,600 cfs durign the early morning hours to a high of 13,990 cfs during the afternoon and evening hours. On weekend days in May 2022, releases will be steady near 9,350 cfs. The Glen Canyon Dam Implementation Team will closely monitor the condition of resources during the experiment and may terminate implementation at any time if unanticipated negative impacts are observed or are likely to occur due to ongoing drought and low lake levels.
Insects expected to benefit from this experiment are an important food source for many species of fish, birds, and bats in the canyon. Beyond expected resource benefits, this experiment will also provide scientific information that will be used in future decision making. Although every effort will be made to match the design of the experiment described above, Reclamation will continue to exercise the operational flexibility described in the LTEMP ROD. Additional information can be found on the Glen Canyon Dam Adaptive Management website here: https://www.usbr.gov/uc/progact/amp/ltemp.html
|Month||Release Volume (af)||Maximum Daily Fluctuation (cfs)||Weekday Maximum (cfs)||Weekday Minimum (cfs)||Weekend Release (cfs)|
The unregulated inflow volume to Lake Powell during April was 594 thousand acre-feet (kaf) (66 percent of average). The release volume from Glen Canyon Dam in April was 502 kaf. The end of April elevation and storage of Lake Powell were 3,522.77 feet (177 feet from full pool) and 5.79 million acre-feet (maf) (24 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 2022 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 operating tier for water year 2022 (October 2021 through September 2022) was established in August 2021 as the Mid-Elevation Release Tier consistent with Section 6.C.1 of the Interim Guidelines. The August 2021 24-Month study projected the January 1, 2022, 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. As previously mentioned, in light of the prolonged drought, low runoff conditions, and depleted storage at Lake Powell, the Department of the Interior implemented an action under Sections 6 and 7.D of the 2007 Interim Guidelines specifically reducing the Glen Canyon Dam annual releases to 7.0 maf in water year 2022.
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 1,100 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 2022 unregulated inflow to Lake Powell, issued on May 4, 2022, by the Colorado Basin River Forecast Center, projects that the most probable (median) unregulated inflow volume this year will be 5.98 maf (62 percent of average).
In addition to the May 2022 24-Month Study based on the Most Probable inflow scenario, and in accordance with the Drought Response Operational Agreement (DROA)), Reclamation has conducted a model run in May to determine a possible range of reservoir elevations under probable most and minimum inflow scenarios. The probable maximum inflow scenario results were completed for the April 24-Month Study. The probable minimum and probable maximum model runs are conducted simultaneously in January, April, August, and October. 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 2022 ranges from a minimum probable of 4.93 maf (51 percent of average) to a maximum probable of 7.51 maf (78 percent of average) with the most probable forecast for water year 2022 of 5.98 maf (62 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 5.98 maf unregulated inflow for water year 2022,, the May 24-Month Study projects Lake Powell elevation will end water year 2022 near 3,528.57 feet with approximately 6.15 maf in storage (25 percent of capacity). Note that projections of elevation and storage for water year 2022 have significant uncertainty at this point in the season. Projections of end of water year 2022 elevation using the minimum inflow forecast results from the May 2022 model run is 3,518.37 feet and from the maximum inflow forecast results from April 2022 is 3,551.80 feet, respectively. The annual release volume from Lake Powell during water year 2022 will be 7.0 maf as determined under Section 6.C.1 and 7.D of the Interim Guidelines as determined by the Department of the Interior.
Upper Colorado River Basin Hydrology
Upper Colorado River Basin regularly experiences significant year to year hydrologic variability. During the 22-year period 2000 to 2021, however, the unregulated inflow to Lake Powell, which is a good measure of hydrologic conditions in the Colorado River Basin, was above average in only 5 out of the past 22 years. The period 2000-2021 is the lowest 22-year period since the closure of Glen Canyon Dam in 1963, with an average unregulated inflow of 8.46 maf, or 88 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 2000-2021 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 2022 unregulated inflow to Lake Powell is projected to be 5.98 maf (62 percent of average).
At the beginning of water year 2022, total system storage in the Colorado River Basin was 22.80 maf (38 percent of 59.60 maf total system capacity). This is a decrease of 5.97 maf over the total storage at the beginning of water year 2021 when total system storage was 28.77 maf (48 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 now current level of 38 percent of capacity at the beginning of water year 2022. Based on current inflow forecasts, the current projected end of water year 2022 total Colorado Basin reservoir storage is approximately 20.13 maf (34 percent of total system capacity). The actual end of water year 2022 system storage may vary from this projection, primarily due to uncertainty regarding this season’s runoff and reservoir inflow.