C153808 Feasibility Study - Laserfiche WebLink

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I I I I I I I I I I I I I I I I I I I interest in the Lock Ditch has irrigated approximately 632 acres of alfalfa and grass hay in Sections 16, 17,21, and 22 of Township 16 South, Range 65 West. Table VI-2 summarizes the Lock Ditch diversions from 1922 through 1989. The average annual diversion was 1,769 acre-feet per year (excluding 1957 when no diversion records were noted). Diversions ranged from a low of 318 acre-feet in 1955 to a maximum of 3,809 acre-feet in 1930. A three-quarter interest in the ditch would yield an average annual headgate diversion of 1,327 acre-feet. John Venezia, in Case No. 85CW38, changed the fixed point of diversion of the Lock Ditch to allow an alternate point of diversion at the Chilcott Ditch, however no change in the use or location of use of the water right was made. The findings in 85CW38 also noted that the historic average annual diversion for the three-quarters interest in the Lock Ditch was 1,948 acre-feet (study period 1974 through 1983) with a single year maximum of 2,919 acre-feet. Historic average annual consumptive use under the Venezia Lock Ditch water rights wa~ found to be 1,180 acre-feet, which represents a system efficiency of 61 percent (1,180 acre-feet/l ,948 acre-feet). Using a total system efficiency of 61 percent and the long-term (1922 through 1989) average diversions of 1,327 acre-feet, the long-term average annual Lock Ditch consumptive use credie is estimated to be 809 acre-feet. The average annual consumptive use estimate of 809 acre-feet, based on the long-term diversion records is probably more representative of the credit one would get in a change of use proceeding, and is the consumptive use credit value adopted for this study. The average replacement credits available during the irrigation season are estimated to be 1,070 acre-feet. Replacement credits exceed consumptive use because of lagged return flows. The difference between the two values, 261 acre-feet, is the estimated winter return flow obligation. Purchase of a three-quarter interest in the Lock Ditch would require AGUA to change the water right from irrigation to augmentation use, and require AGUA to build an augmentation station. There also would be annual O&M costs associated with running water through the augmentation station back to Fountain Creek. Also associated with a change of use of Lock Ditch water, would be a requirement that historic winter return flows be replaced to Fountain Creek. The average replacement credits of 1,070 acre-feet during the irrigation season (April through October) would on average be more than adequate to replace the estimated future well depletions on Fountain Creek between April and October of 579 acre-feet. Excess Lock Ditch replacement credits not utilized on Fountain Creek would be used on the Arkansas River main stem between Pueblo Reservoir and John Martin Reservoir to offset well depletions in this reach. -21-