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PA.'_ '\ ~ Table A-7 Third Terrace Pumping Plant Maximum flow (cfs) Acres served Peak electrical capacity (kilowatt) Average annual energy requirement (kilowatt-hour) (2) Operationa!! 30 1,874 500 973,000 Essentially all flow in the La Plata River would be diverted to Southern Ute Reservoir, although bypass would occur under certain circumstances. Water deliveries under the La Plata River Compact would not be affected by the project, and flows would be bypassed to fulfill prior nonproject rights in New Mexico, usually occurring in May and averaging 200 acre-feet annually. In addition, flows would be bypaased whenever necessary to ensure a streamflow of 1 cfs at the Colorado-New Mexico State line. In addition to natural La Plata River runoff, most of the return flow from project land would be diverted to Southern Ute Reservoir for reuse, as would water turned out from the Dry Side Canal to the La Plata River specifically for storage in Southern Ute Reservoir. Southern Ute Reservoir would be maintained at approx- imately one-half capacity during average runoff years with the total capacity used for storage only during years of high runoff (in 5 years during the 49-year study period). This practice would keep pumping from Ridges Basin Reservoir, and consequently project operating cos ts, to a minimum while maximizing project efficiency. The annual maxilllum level would generally occur in May, and the annual minimum level would usually occur in March, During the 49-year study period, the reservoir was drawn down to the top of the inactive pool only in 1 year, Releases of muni- cipal and industrial water from Southern Ute Reservoir would be made year round at a constant rate of 36.6 cfs. Releases for irrigation for New Mexico project land would be made to meet demands during the irrigation season. Because of the large constant municipal and industrial demand and the low inflow during the winter, the reservoir wate,r level would usually be at its lowest during March and would result in an average drawdown of 9 feet, decreasing the surface area from 1,265 to 1,150 acres. During the 49-year study period, the average annual draw- down of 9 feet was exceeded in 28 years. The following table is a summary of information on drawdown that was developed using the computer simulation of operations, The reservoir's end-of-month content for typical wet, normal, and dry years is presented in Attachment 1. 1/ Operations of project features in the Southern Ute Reservoir system were studied using computer simulation of operations, the same as for the Ridges Basin Reservoir system, based upon hydrologic data for the 49-year period from 1929 through 1977 (Bureau of Reclamation, 1978). A-22 I 'I :'1 ;, ~: ;;-; ;.. ~';., .~ ,t>~', -',', ~;: