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. . I') ') r, ,": ...tJ WI ..... TABLE 4.1.3A Stream Flow Comparison A verage (acre-feet/year) 1975-1991 Base Historic # 1D Name Streamflow Streamflow 44 09171100 DOLORES RIVER NEAR BEDROCK, CO, 494038 333840 45 09171200 SAN MIGUEL RIVER NEAR TELLURIDE, CO, 51208 51208 46 09172000 FALL CREEK NEAR FALL CREEK, CO, 19550 18642 47 09172100 LEOPARD CREEK AT NOEL, CO, 4105 1928 48 09172500 SAN MIGUEL RIVER NEAR PLACERVILLE. CO. 187494 182519 49 09173000 BEAVER CREEK NEAR NORWOOD, CO. 28503 9550 50 09175500 SAN MIGUEL RIVER AT NATURITA, CO, 260127 213403 51 09177000 SAN MIGUEL RIVER AT URA V AN, CO. 315175 290940 52 09179500 DOLORES RIVER AT GA TEW A Y, CO. 830453 645305 53 09364500 ANIMAS RIVER AT FARMINGTON, NM 733902 660536 4,1.4 Historic Streamflow File - sanjuan.rih The sanjuan.rih file contains historic streamflow records that are used for baseflow generation and model calibration, Table 4.1.3a summarizes the gages used and their average annual flow. Approximately 98 USGS streamflow gages were identified for inclusion in the San Juan Model. Not all gaging stations were in operation during the entire study period, and of the 98 gaging stations identified, 53 were used based on their period of record and location. Table 4.1.3a presents the historic flows for the water years 1975-1991 and the average estimated natural flows at each of the 53 USGS gages used in the baseflow development and model calibration. The difference between modeled and historic streamflows represents the depletion estimated with historic diversions and reservoirs incorporated in the model. Appendix C, Section 6 also describes the technique used to fill data gaps, along with the data filling results. The locations of streamflow gages modeled are shown in Figure 4.1.1a, For a more detailed discussion on the historic streamflow file, see the StateMod Users' Manual. 4.1.5 Baseflow File - sanjuan.rib The baseflow file contains proration factors that allow baseflows estimated at gaged locations to be distributed to ungaged areas of interest. Proration factors used in this modeling effort were developed to provide baseflow estimates at selected points throughout the river basin using the following guidelines: . The most upstream diversion structure in each tributary · Critical points of interest, such as river confluence points . All reservoir locations ~.;,..;..:.., The sanjuan,rib input file contains the proration factors used by StateMod to distribute gaged flows throughout the river basin, Proration factors were defined as the fraction of the reach gain that was estimated to be tributary to a baseflow point. These factors were determined by normalizing the local volumetric runoff (local area multiplied by local average precipitation) by the corresponding incremental reach volumetric runoff. River System o3201wrpdoc.s/SiJlljutJll!4-G-I.doc 9n5/96 4-5