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Results of baseflow model runs for the Rio Grande model indicate calculated negative flow <br />conditions at 10 of the 53 gages represented. For the most part, the calculated negative flow <br />values are relatively small and infrequent (less than 5 percent of the time and less than 20 cfs). <br />However, calculated negative flows are more frequent and more substantial at two of the modeled <br />gages (08249000 - Conejos River Near LaSauces, and 08243500 - Trinchera Creek Below <br />Smith Reservoir). Discussions with Division 3 staff confirm that these gages periodically suffer <br />from backwater conditions and/or channel profile shift that can reduce accuracy of measurements. <br />Results -Check Mode <br />Results of operating the surface water model in check mode include a listing of 1) calculated <br />baseflows at all points in the model; 2) all diversions; 3) all instream flows; 4) all water rights <br />(sorted by priority); and 5) a summary of all structures, water rights and operating rules. This last <br />listing (rg.xtb), is very useful for reviewing how the StateMod code has interpreted user supplied <br />input and was heavily relied on during initial model creation and debugging. <br />Execution of StateMod in check mode also creates an initial output request file (rg.xou). This file <br />may be hand edited to request only select data be extracted and available for reporting. During <br />Phase la efforts, all output were requested and reviewed during model calibration. <br />Results -Historical Simulation <br />The Phase la model includes model execution in simulation mode using historical diversions as <br />demands. In addition, historical end of month (EOM) contents at modeled reservoirs are used as <br />EOM targets. Model representation of the Rio Grande Compact, which is administered by <br />Division 3 through a complex routing involving forecasted inflows, has been simplified by for <br />Phase 1 analysis by representing the Compact as a diversion demand with zero consumption at <br />the lowest point on the Rio Grande: the demand for this "diversion point" is simply the historical <br />flows at the CO - NM state line; the water right is the most senior in the basin; and the returns <br />from this diversion are modeled as occurring immediately. <br />As described above, calibration efforts during the historical simulation runs focused on three <br />areas: comparison of historical observations to modeled 1) diversions; 2) reservoir EOM <br />contents; and 3) streamflows at gage locations. Each of these comparisons are discussed below. <br />The referenced Attachments illustrate these comparisons graphically. <br />Modeled Stream Flows <br />Attachment 1 illustrates comparisons of modeled stream flows to historical observations at <br />several key stream gages. As shown, these comparisons are very favorable and demonstrate less <br />than 1% deviation in the model results from historical gaged flows. Comparisons at individual <br />gages represented in the model are shown in Table 3. <br />C:Acdss\Task6-14.doc Phase la Model (Flistoric Monthly) February 22, 2000 -Page 6 of 10 <br />