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. o~~rJf;'~8 u~1~,}':J('l . PART V. HISTORIC FLOWS OF THE SAN JUAN RIVER . San Juan River near CillTacas Monthly streamflow records of the San Juan River at the Carracas gage are available for the period of October 1961 through 1980. Missing data from the 1951 through 1980 study period were synthesized by using historic streamflow records for the San Juan River at Rosa and the Fiedra River near Arboles. Comparisons were made of the flows at the Carracas gage with the net flows resulting from the Rosa gage minus the Arboles gage for the concurrent period of record, and a best-fit relation was determined for each month. Missing flow data for the Carracas gage were estimated through use of the best-fit relations. . . As a cross-check of the estimated flows at Carra cas for the 1951 through 1961 period of missing data, the Carracas estimated historic flows were compared with the sum of gaged flows of the three major tributaries to the San Juan River above Navajo Reservoir. These flows are recorded by the San Juan River at Pagosa Springs, the Navajo River at Edith, and the Rio Blanco below Blanco Diversion Dam stream gages. . . Flows at the "Rio Blanco Below the Blanco Diversion Dam" gage, were estimated for the 1951 through 1970 period from the "Rio Blanco near Fagosa Springs" gage, located 1.5 miles upstream. . Adjustments were made in the estimated flows at Carra cas as necessary to improve the accuracy of the synthesized data. The historic and estimated historic flows of the San Juan River at the Carracas gage have averaged about 440,000 acre-feet per year. Monthly summaries of these flows for the 1951 through 1980 study period are presented in Appendix B. . . Tributary Inflow The difference between the Carracas gage and the sum of the three upper San Juan River gages is equal to the tributary inflow contributed by the lower 691 square miles of the San Juan and Navajo River drainages. The relationship -12- . ,,t\, '-/';'