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I I I I I I I I I I I I I I I I I I I JOHNSON RESERVOIR ALTERNATIVE The Johnson Reservoir alternative is potentially the best plan available to provide water to Durango West and the surrounding area, including the RV Park and Rafter J. The plan involves utilization of an existing 1,000 acre-foot reservoir about one mile east of Durango West. See Figure IV-2. The two major issues concerning the plan are availability of water to yield the required supply, and the price the reservoir owner would charge to recover his costs in the facility. The Johnson Reservoir is located on a small, 0.75 square mile, drainage at an excellent location for a reservoir, because there is a large reservoir formed with a small dam. The dam was constructed in about 1980 and is presently full most of the time. The drainage area will only provide about 140 acre-feet of water per year on the average, which is adequate for evaporation and seepage but not to supply Durango West. The reservoir can also be filled with Pine Ridge Ditch water that is diverted from the La Plata River under a medium priority water right. The owner of the reservoir has 3 CFS of the 14 CFS of the medium priority water in the ditch and 14 CFS of a lower priority water. Durango West also can utilize about 10%, 1.4 CFS, of the water in the Pine Ridge ditch. An evaluation of the potential inflow to the reservoir was made based upon possible diversions from the La Plata River under the existing administrative restrictions. The general procedure was to compare the Hesperus and Stateline gages and estimate when there was water available for diversion and when there was not. When there was water available, it was assumed that 3 CFS would be diverted to the reservoir, which is a conservative assumption. It was assumed that diversions could be made from April to October. Table IV-F is a reservoir operation study of Johnson Reservoir. Column 1 is the year and month for the period simulated. Columns 2 is the inflow from the drainage. Column 3 is the inflow to the reservoir from the LaPlata River through the Pine Ridge Ditch. Column 4 is the water demand and Column 5 is other losses such as evaporation and seepage. Column 6 is the end-of-month content of the reservoir. Column 7 is the spill from the reservoir. The per iod 1975 to 1980 was used because it represents a severe shortage period. The results showed that there was adequate water to serve Durango West and the RV Park, if included, without shortages. (1 ) Pine The water supply it does not include Ridge Ditch that is believed to be conservative because: runoff collected from the area above the is not a diversion from the La Plata - 24 -