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nD[r339 . Name West Mancos River Crystal Creek Ditch Jackson Gulch Reservoir Inlet Canal Lee & Burke Ditch Field Ditch Town of Mancos Pipe line West Mancos Water Supply System Middle Mancos River Webber Inlet (Crane Ditch) Long Park Ditch Smouse Ditch Davenport Ditch Dunton Ditch East Mancos River Williams Ditch East Mancos Highline Ditch Total Average Annual Diversion 1938-1951 (acre-feet) 453 1,490 930 650 650 100 340 440 90 230 140 119 477 6,109 . See Appendix B for summaries of monthly diversion records. Diversions to Jackson Gulch Reservoir from the Wesst Mancos River began in 1949. Most of the irrigation releases from the reservoir were made through the West Mancos Outlet Canal, which discharges water back to the river upstream of the West Mancos gaging station. Return flows to the river through the outlet canal in 1949 through 1951 were included in the calculations. Approximately 60 percent of the irrigated land under the Williams Ditch is located in an area that naturally drains to the East Mancos River upstream of the gaging station. Assuming an overall 60 percent irrigation efficiency under the Williams Ditch, it is estimated that 24 percent of the ditch diversions returned to the East Mancos River upstream of the gage. Similarly, all of the irrigated lands under the Dunton Ditch are located upstream of the gage, and it is estimated that 40 percent of the ditch diversions return above the gage. The total amount of irrigation return flows above the East and Middle Mancos gages is estimated to average 86 acre-feet per year, which is less than one percent of the total recorded flow. Any errors in this estimate would have . -23- . "I