24-Month Study Projections

Overview

The 24-Month Study projects future Colorado River system conditions using single-trace hydrologic scenarios simulated with the Colorado River Mid-term Modeling System (CRMMS) in 24-Month Study Mode. Three Studies, the Most, Minimum, and Maximum Probable 24-Month Studies, are released monthly, typically by the 15th day of the month.

  • Initial Conditions: The 24-Month Study is initialized with previous end-of-month reservoir elevations.
  • Hydrology: In the Upper Basin, the first year of the Most Probable inflow trace is based on the 50th percentile of Colorado Basin River Forecast Center (CBRFC) forecasts and the second year is based on the 50th percentile of historical flows. To represent dry and wet future conditions, the Minimum Probable and Maximum Probable traces use the 10th and 90th forecast percentiles in the first year and the 25th and 75th percentiles of historical flows in the second year, respectively. The Lower Basin inflows are based only on historical intervening flows that align with the Upper Basin percentiles.
  • Water Demand: Upper Basin demands are estimated and incorporated in the unregulated inflow forecasts provided by the CBRFC; Lower Basin demands are developed in coordination with the Lower Basin States and Mexico.
  • Policy: Reservoir operations are input manually in the 24-Month Study by reservoir operators and align with Colorado River policies.
  • Drought Response Actions: CRMMS projections contain actions undertaken with the 2022 Drought Response Operations Plan and 2022 Glen Canyon Dam operational adjustment.
    • The 2022 Drought Response Operations Plan includes an additional release of 500 kaf from Flaming Gorge from May 2022 through April 2023.
    • The Glen Canyon Dam operational adjustment reduces the releases from Lake Powell from 7.48 maf to 7.00 maf in water year 2022 will result in a reduced release volume of 0.48 maf that normally would have been released from Glen Canyon Dam to Lake Mead as part of the 7.48 maf annual release volume, consistent with routine operations under the 2007 Interim Guidelines. The reduction of releases from Glen Canyon Dam in water year 2022 (resulting in increased storage in Lake Powell) will not affect future operating determinations and will be accounted for “as if” this volume of water had been delivered to Lake Mead. Should the August 2022 24-Month Study determine that Glen Canyon Dam will operate in a balancing condition in water year 2023, Reclamation operations will be implemented in a manner that preserves the benefits to Glen Canyon Dam facilities and operations in 2023.

For more detailed information about the approach to the 24-Month Study modeling, see the CRMMS 24-Month Study Mode page. All modeling assumptions and projections are subject to varying degrees of uncertainty. Please refer to this discussion of uncertainty for more information.

Projections

The latest 24-Month Study reports for each study can be found at the links below:

Archived 24-Month Study results are also available. Descriptions of the 24-Month Study hydrologic scenarios are also documented in Monthly Summary Reports. Lake Powell and Lake Mead end-of-month elevation charts are shown below.

Projected Lake Powell end-of-month physical elevations from the latest 24-Month Study inflow scenarios. Note: The April 2022 Probable Maximum 24-Month Study projection does not reflect the action taken in May to reduce the water year 2022 release from Glen Canyon dam by 480 kaf. The probable maximum scenario will be adjusted for this action the next time it is run.

Projected Lake Mead end-of-month physical elevations from the latest 24-Month Study inflow scenarios. Note: The April 2022 Probable Maximum 24-Month Study projection does not reflect the action taken in May to reduce the water year 2022 release from Glen Canyon dam by 480 kaf. The probable maximum scenario will be adjusted for this action the next time it is run.


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Last updated: 2022-05-27