24-Month Study Projections


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.

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


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 elevations from the latest 24-Month Study inflow scenarios.

Projected Lake Mead end-of-month elevations from the latest 24-Month Study inflow scenarios.

For additional information or questions, please contact us via email at: .

Last updated: 2021-10-18