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evaporation values depending on their locations. The net evaporation values (inches) used in the <br />model is shown in Table 7 (note a negative value indicates more precipitation than evaporation: <br />Table 7 <br />Net Monthly Evaporation Values <br />Used in the Rio Grande SurFace Water Model (inches) <br />Oct Nov Dec Jan Feb Mar Apr May Jun Jul Aug Sep Total <br />SAN LUIS VALLEY FLOOR 4.14 -0.34 -0.21 -0.22 -0.17 -0.30 7.08 7.31 8.37 7.42 6.48 6.08 45.63 <br />MOUNTAIN AREAS 2.88 -1.03 -0.61 -0.44 -0.39 -0.59 -0.76 5.49 7.61 6.12 3.74 4.34 26.35 <br />End of Month Contents <br />Historical end of month (EOM) contents were extracted from HydroBase using the DMI tstool. <br />Because EOM data are commonly missing for portions of the study period, data filling is <br />necessary. Tstool allows data filling using a two step search and fill algorithm. In the first step, a <br />search is done five days in either direction from the end of the month. The second step is to use <br />linear interpolation on the monthly values. In instances when little or no data are found for long <br />periods, average monthly EOM values over the entire study period are used. <br />Reservoir Targets <br />Reservoir targets reflect specific operational criteria to meet objectives such as flood control or <br />recreational levels. In most cases, reservoir targets are simply the decreed capacity. In others, <br />target levels may be less than decreed capacities for certain portions of the year. For all but two of <br />the explicitly modeled reservoirs (San Luis Lake and Platoro Reservoir), monthly storage targets <br />are set to decreed reservoir capacities. <br />Water levels in San Luis Lake are controlled by the U.S. Bureau of Reclamation (BuRec) as part <br />of its operations of the Closed Basin Project. The Lake provides flexibility in managing Compact <br />delivery amounts and water quality, as well as recreational opportunities to residents in the San <br />Luis Valley (Colorado Division of Wildlife manages recreational aspects of the Lake). The BuRec <br />attempts to maintain a surface water elevation of 7,519.3 feet in the Lake, corresponding to a Lake <br />surface area of 890 acres, or contents of approximately 7,000 af. <br />Flood control operations at Platoro Reservoir are managed by the U.S. Army Corps of Engineers. <br />The COE utilizes a series of reservoir flood curves that consider forecasted inflows when <br />establishing specific yearly drawdown levels necessary to accommodate spring runoff. Because <br />runoff volumes differ from year to year, drawdown requirements will also differ. As a <br />simplification in the Rio Grande surface water model, Platoro Reservoir targets are set to average <br />drawdown requirements during the runoff period. <br />Command Files <br />Command files were developed to operate all DMI's and extract data from HydroBase to develop <br />the surface water model reservoir input files. The StateMod reservoir files are provided as <br />Attachments 1, 2, 3, 4 and 5. The header portion of these input files comprises the watright <br />command file. <br />C:Acdss\Task6-8.doc Prepare Reservoir Files September 7, 1999 -Page 6 of 7 <br />