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# Interior Region 7 • Upper Colorado Basin

Encompassing all or parts of Arizona, Colorado, Idaho, Nevada, New Mexico, Texas, Utah and Wyoming

              - Reclamation
              - Upper Colorado Basin
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              - 24-Month Study

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# 24-Month Studies

Monthly 24-Month Study Reports present hydrological  descriptions and projected operations for the Colorado River system reservoirs  for the next two years. The 24-Month Study Report is a combination of a  write up of recent, current and potential future operations and a listing of  the 24-Month Study computer model output. The 24-Month Study computer model projects future reservoir conditions  and potential dam operations for the system reservoirs given existing reservoir  conditions; inflow forecasts and projections; and a variety of operational policies  and guidelines. Monthly reservoir inflow forecasts and projections are produced  by the National Weather Service, Colorado Basin River Forecast Center **.

The 24-Month Study model is updated at the beginning of each  month upon receipt of the monthly inflow forecast from CBRFC. The CBRFC reservoir inflow forecasts extend from  three to seven months based on the time of year. Values used in the model beyond that are based  on historic statistical averages. For  most months, the CBRFC reservoir inflow forecast is only produced for the most  probable (50% probability of exceedance), however for the months of August, October,  January and April minimum probable (90% exceedance) and maximum probable (10%  exceedance) inflow forecasts are produced by CBRFC. For these months, minimum, most and maximum  probable runs of the model are conducted producing a range of potential future reservoir  conditions and operations.

Reclamation has revised the format of the 24-Month Study Report beginning with the May 2021 report. The 24-Month Study report continues to provide coordinated operations for the Upper Colorado and Lower Colorado Basin reservoir operations. It now includes a coordinated introduction providing salient information for the current month.

Upper Colorado Basin hydrology summary language for major reservoirs will continue to be available in the separate basin hydrology summaries below.

**It should be noted  that all future conditions and operations presented in the 24-Month Studies are only projections and are subject to change as the year progresses and actual  hydrology, operations and forecasts diverge from those used to produce specific 24-Month Study projections.**

## 24-Month Study Reports: by Month

              - January **Link is to a PDF file
              - February **Link is to a PDF file
              - March **Link is to a PDF file
              - April **Link is to a PDF file
              - May **Link is to a PDF file
              - June **Link is to a PDF file
              - July **Link is to a PDF file
              - August **Link is to a PDF file
              - September **Link is to a PDF file
              - October **Link is to a PDF file
              - November **Link is to a PDF file
              - December **Link is to a PDF file

## Upper Colorado Basin Hydrology Summaries

              - January **Link is to a PDF file
              - February **Link is to a PDF file
              - March **Link is to a PDF file
              - April **Link is to a PDF file
              - May **Link is to a PDF file
              - June **Link is to a PDF file
              - July **Link is to a PDF file
              - August **Link is to a PDF file
              - September **Link is to a PDF file
              - October **Link is to a PDF file
              - November **Link is to a PDF file
              - December **Link is to a PDF file

## 24-Month Study Reports: Min and Max Probable

              - Current Min Probable Data **Link is to a PDF file
              - Current Max Probable Data **Link is to a PDF file

----

Please contact the Operations Group via e-mail at ** ResourceMgr@usbr.gov for additional questions or information.

*Last Updated:           3/15/24*

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