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. GOlOB? . tc, irrigation return flows from Dolores River diversions. To the extent that this assumption is invalid, the virgin flows of McElmo Creek are over-estimated herein. The maximum magnitude of this over-estimation of virgin flows at the state line gage location is roughly 3,200 acre-feet per year. . . McElmo Creek Streamflow - Monthly Analysis The virgin streamflow of McElmo Creek includes components of short-term runoff from major precipitation events in the drainage basin, spring snowmelt runoff, and year-round base flow associated with general rainfall and spring discharge. Total virgin streamflow is expressed by the following relationship. . (1) Total Virgin Flow = Short-Term Runoff + Spring Snowmelt Runoff + Base Flow - Stream Losses The relationship can be rearranged as follows: . (2) Spring Snowmelt Runoff + Base Flow = Total Virgin Flow - Short-Term Runoff + Stream Losses . For the purposes of this analysis, stream losses under virgin flow conditions are assumed to be negligible. Total virgin flow and short-term runoff were e:;timated as described on pages 13 and 14 above. Therefore, average annual spring snowmelt runoff and base flow may be calculated as follows: . (A verage values in acre-feet per year) . Total Virgin Short-Term Stream Snowmelt Location Flow Runoff Losses and Base Flow McElmo Creek above 4,400 1,500 0 2,900 Alkali Canyon "McElmo Creek below 7,800 2,700 0 5,300 Cortez" gage site McElmo Creek near 9,100 3,100 0 6,000 State Line . -20- . iJll__,'ij(-_