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Rt is the sum of the return flows in the basin above the site, computed as an irrigation efficiency (r~) <br />times the diversion at time period t, and then lagged by a function for each diversion; <br />OSt is the sum of the change in reservoir storage above the site. <br />It is the sum of imports to the basin above the gage; <br />Et is the sum of exports from the basin above the gage; and <br />rlc is the irrigation efficiency of each diversion as defined by Equation 2: <br />CUIRt (2) <br />~1 c - D <br />t <br />Where CUIRt is the theoretical consumptive use irrigation requirement based upon temperature and <br />precipitation data. <br />In the simulation mode, after natural flows have been calculated, StateMod will simulate a potential <br />diversion, Dt, using Equation 3: <br />Dt =min( CUIRt ~ Water Right priority, Capacity, Physical Availability) (3) <br />~7r <br />Evaluation of Historical Streamflow and Climate Data Extension <br />The Colorado River Decision Support System (CROSS) Database consists of 667 historical Streamflow <br />gages, with 183 of those gages used in calibration of the Water Resources Planning Model (StateMod). <br />All of the gage data may be found by accessing the CROSS Database Web Interface page on the <br />Internet. Exhibit 1 lists the five river basins used in the Water Resources Planning Model and the <br />respective gages used in each basin. It lists each gage's period of record by water year, the number of <br />years within the record, the number of years of data that were actually measured or observed, and the <br />percent completeness for each gage's period of record (the years of measured or observed data divided <br />by the total years of data within the record). The gages used in each river basin were found by accessing <br />the CROSS on-line documentation for each water resources planning model. <br />The CROSS Database contains 106 historical temperature, and 132 historical precipitation gages. Of <br />these, 51 temperature gages and 57 precipitation gages were used to calibrate the Consumptive Use <br />(CU) Model. Likewise, all of the gage data is available on the CROSS Database Web Interface page. <br />Exhibit 2 lists the five river basins used in the Consumptive Use Model and the respective temperature <br />and precipitation gages used in each basin. It lists the same type of gage information for each gage as in <br />Exhibit 1. The only difference is that the periods of record are by calendar year, not water year. <br />Determining the climatological stations used in each river basin proved to be more difficult than <br />establishing the Streamflow information. The on-line documentation for the Consumptive Use Model <br />does not contain the climatological station information used in each river basin. Therefore, it was <br />necessary to establish a computer link to the state's UNIX machine at the Division of Water Resources. <br />After accessing the CROSS data directory, a file was located containing the climatological stations used <br />in the CU model. The file contains a listing of information in the following order. First, it lists all of the <br />climatological stations in the five river basins (54 total). Next, it lists all of the county and hydrological <br />unit code (I-IUC) combinations that exist on the western slope, categorized first by temperature and then <br />by rainfall. Each category contains 91 county/HUC combinations. Each combination lists the station(s) <br />used, each station's numerical identifier, and the weighting of the station(s). For example, the Gunnison <br />Appendix E E-15 <br />