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OGfl333 . . . The relationship can be rearranged to solve for river gains: (2) River Gains = Historical Flow at Highway 666 + Irrigation Depletions + River Losses - Virgin Flow at Upper Gages - Short-Term Runoff A summary of the historical flow at the Highway 666 gage (published as the Mancos River at Towaoc) is provided in Appendix A. As described in Part IV, irrigation diversions of about 1,400 acre-feet per year bypassed the Highway 666 gage. The total historical flow at Highway 666 is therefore equal to the recorded flow plus the irrigation bypass, for a total that averaged 31,100 acre-feet per year during the 1951 through 1980 study period. Irrigation depletions have averaged about 18,800 acre-feet per year in the area upstream of the Ute Mountain Ute Indian Reservation, as described in Part V. River losses are estimated to average about 4,100 acre-feet per year for the reach between the upper gage location and the gage near Highway 666, as listed in Table 12. Short-term runoff for this reach was estimated to average about 1,700 acre-feet per year, as summarized in Table 16. The virgin flow at the confluence of West, Middle, and East Mancos rivers during the 1951 through 1980 study period was estimated to average 42,000 acre-feet per year, as described in Part IX and summarized in Appendix C. Using the relationship in Equation 2, river gains during the 1951 through 1980 study period have averaged about 10,300 acre-feet per year: (3) River Gains = 31,100 + 18,800 + 4,100 - 42,000 - 1,700 = 10,300 River Gains - Monthly Analysis River gains vary considerably from month to month and year to year because -37- ,Ji.