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TABLE 1 <br />TOTAL DRAINAGE AREAS <br />NodeStation IDTotal Drainage Area (mi2) <br />2009109000254* <br />4009110000477* <br />10Inflow 1254* <br />30Inflow 2310** <br />40Inflow 3477* <br />* Drainage area obtained from USGS remarks file, listed in Exhibit A. <br />** Drainage area determined as fraction of river mile <br />The flow proration factor for Node 10 is given in Equation 2. <br />254 <br />== <br />P 1 <br />Equation 2 <br />10 <br />254 <br />One hundred percent of the base flow calculated at core station 09109000 will be supplied as inflow <br />at Node 10. <br />The flow proration factor for Node 30 is given by Equation 3. <br />?? <br />()() 310254 DADA <br />30 20 <br />= = <br />P 025 . 1 <br />Equation 3 <br />30 ?? <br />()() 477254 DADA <br />4020 <br />Twenty five percent of the calculated reach gain (base flow at 09110000 minus base flow at <br />09109000) will be seen at Node 30 and the remaining 75 percent (1-.25) will be seen at Node 40. <br />Comparison to U.S. Bureau of Reclamation (USBR) Base Flows (February 1988 Report) <br />The Upper Gunnison-Uncompahgre Basin Model Inflow Development Report (February 1988) <br />describes the methodologies used in developing base flows and inflows provided by the USBR to <br />WBLA?s Upper Gunnison-Uncompahgre Basin Model Study. Base flows were developed for <br />selected gaging stations to serve as core stations from which inflows within subbasins were derived. <br />Core stations for which base flows were derived include Taylor River below Taylor Park Reservoir <br />(09109000) and Taylor River at Almont (09110000). Base flows at these two core stations were <br />Note: It was assumed that <br />derived by adjusting historical gaged flows for reservoir storage. <br />reservoir evaporation and depletions from irrigation were negligible. <br />Tables 2 and 3 below compare the base flow developed using STATEMOD to those developed by <br />the USBR. <br />3.0 CONCLUSIONS/RECOMMENDATIONS <br />A comparison of annual flows between the BOR and STATEMOD show differences of less than 1 <br />percent, which are probably caused by the BOR not accounting for reservoir evaporation. Larger <br />monthly differences up to 20 percent can be attributed to the different methodologies employed by <br />each procedure. However, in 1976 at the Almont gage, the BOR and STATEMOD base flow values <br />differ by 38 and 585 percent. This large difference requires further evaluation. <br />3 <br />A275 03.20.95 1.15-28 Ritsch <br />