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<br />APPENDIX II <br /> <br />o <br />~:- ) <br />~.;) <br />.+:- <br />00 <br />C,Q <br /> <br />USE OF <br />THE COLORADO RIVER SIMULATION SYSTEM (CRSS) <br />TO DETERMINE AVAILABLE STORAGE <br /> <br />Documentation of the CRSS model is found in the following publications, all <br />published by the Bureau of Reclamation: <br /> <br />Colorado River Simulation System - An Executive Summary <br />Colorado River Simulation System - System Overview <br />CRSM User Manual <br /> <br />The model accounts for sedimentation in four reservoirs: Navajo, Flaming <br />Gorge, Lake Powell, and Lake Mead. Sedimentation is assumed to be a <br />constant annual amount that varies seasonally for each reservoir, but the <br />distribution of sediment between active and dead storage pools is a <br />function of the individual reservoir operation. The model continually <br />updates the elevation-capacity relationships for each of the four <br />reservoirs. Sedimentation is important in yield determination since over <br />the 81 year period of record used in modeling. total Upper Basin system <br />storage is decreased by over 5 MAF as a result of sediment. <br /> <br />Shortages are calculated locally in the model at individual demand points <br />and summed for the entire basin. The model output indicates total annual <br />shortages. It is recognized that inaccuracies in shortages are generated <br />by the model. This is due to modeling limitations such as not modeling <br />local storage facilities, as well as not recognizing water right prior- <br />ities. In some instances shortages are generated due to inadequacy of <br />hydrologic information in localized areas. <br /> <br />In current runs of the eRSS model, consideration of bank storage is given <br />to two reservoirs in the Upper Basin. The change in storage of Lake Powell <br />is modified by a bank storage factor of 0.08 and in Flaming Gorge the <br />change in storage is modified by a factor of 0.033. No consideration for <br /> <br />2B <br />