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<br />FINAL MEMORANDUM <br />TO: Ray Alvarado March 10,003 <br />FROM: Meg Frantz, Boyle Engineering Corporation <br />SUBJECT: CDSS Daily Yampa Model -Task 3 Selecting a Daily or <br />Monthly Model <br />Introduction <br />StateMod and the CDSS DMI's have been enhanced to allow the user to develop daily dataets either <br />directly from daily observations and estimates, or by disaggregating some types of input frq an <br />existing monthly model; nearly automatically. These features were developed with these pe~Spectives in <br />mind: <br />• Generally, preparing a monthly model before preparing a daily model helps the user'~nderstand <br />the system, without burdening him with gathering and handling the volume of info ation <br />required for a daily model. Specifically, the CDSS project completed monthly mode s in the Rio <br />Grande and five Colorado sub basins before it developed daily versions of any of th se models. <br />During the monthly model development, operating criteria and baseflow hydrology derwent <br />several refinement iterations. <br />• Some types of data are typically unavailable or error-prone (e.g., reservoir contents) n a daily <br />basis, but can be adequately estimated by disaggregating monthly values for the pareter. <br />• Some types of input, such as consumptive use-based demand estimates, are products) pf a <br />monthly model, for which there is no daily analog. <br />• Developing daily data sets nearly automatically from monthly data sets is extremely',efficient and <br />pragmatic. This is true with respect to both the amount of time required to create the~tnodel, and <br />the volume of data that must be stored and handled. <br />The CDSS system now includes daily time step models of the Rio Grande and several sub- asins of the <br />Colorado River, which the State through its consultants has developed and calibrated. Theo jective of <br />this memo is to help the user decide which type of model to use, whether or not a CDSS dai y model <br />exists. The memo is divided into the following six major sections: <br />1. Deciding to use a daily time step model <br />2. The routing issue <br />3. The computer resources issue <br />4. Using a monthly model to develop a daily model <br />5. Summary <br />6. Comments and concerns <br />CS-B99-19D-DOB /TASKMEM03FINAL.DOC I304'~LE <br />