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I I I I I I I I I I I I I I I I I I I . 1. There is an observable correlation between the Navajo gage, and the calculated Turkey Creek flows; particularly prior to 1971. (The Navaj 0 gage has been influenced by transbasin diversions since 1971.) 2. The year 1977 is the lowest year of record. 3. The 1936 to 1980 average flow for the East Fork San Juan is 119 cfs, while the 1960 to 1980 average is 114 cfs. The conclusion from these observations is that the selected period of analysis will provide conservative results. 3.3 VIRGIN FLOW DETERMINATION Virgin flows at the Snowball Ditch diversion point on Turkey Creek were determined by comparing area, elevation, and precipitation data in the Turkey Creek basin with the Middle Fork Piedra River basin. Historic streamflow records for the Middle Fork Piedra River include 1978 to 1983; for the East Fork San Juan River, they include 1936 to 1983. A statistical correlation was made for the common years of record between the Middle Fork Piedra River and the East Fork San Juan River. This correlation was used to extend the record on the Middle Fork Piedra River to include 1960 to 1980. Figure 3.2 shows physical and climatological comparisons between the three basins. From the standpoint of area, geology, and precipitation, the Middle Fork Peidr,a River and the Turkey Creek basins are hydrologically similar. A direct statistical correlation between the flows in Turkey Creek and the Midde For Piedra cannot be established since no discharge measurements have been kept on Turkey Creek. Flows therefore had to be calculated on the basis of area, elevation and precipitation relationships between the two .basins. Column 2 on Table 3.1 lists calculated annual virgin flow in Turkey Creek for the years 1960 to 1980. Details of the calculation procedure, as well as monthly flow amounts are given in Appendix D. 3-2