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<br />a I' <br /> <br />OOO~S3 <br /> <br />. <br /> <br />equation results in a value of over 100 percent efficiency which is obviously <br />in error. <br /> <br />. <br /> <br />Current-meter measurements in the inlet canal were made in October 1971 <br /> <br /> <br />when 508.5 cfs were being diverted. These measurements showed a loss of <br /> <br />85.9 cfs in the first 17 miles (16.9%) and 131.9 cfs (26.0%) in the total <br /> <br /> <br />length (Toren, 1971). This estimate is more consistent with what might <br /> <br /> <br />be expected and is further supported by the fact that over 75 irrigation <br /> <br /> <br />wells below the North Sterling inlet canal derive their supplies from that <br /> <br /> <br />canal's seepage losses. Net evaporation losses from the North Sterling <br /> <br /> <br />Reservoir itself probably average about 5,000 acre-feet per year. It is <br /> <br /> <br />believed that the amount of seepage from the reservoir itself is rather <br /> <br /> <br />small compared to the other losses in the system. Seepage losses from the <br /> <br />outlet canal are estimated to be 25 to 30 percent of that amount released <br /> <br /> <br />from the reservoir. Therefore, the average delivery efficiency to farm <br /> <br /> <br />turnouts and the several laterals of the system is somewhat under 50 percent. <br /> <br /> <br />Tetsel Ditch. The Tetsel Ditch diverts from the river 2.2 miles <br /> <br /> <br />upstream from the Balzac gaging station and serves about 1,000 acres of <br /> <br />irrigated land on the north side of the river. All of the irrigated <br /> <br /> <br />land is close to the river and is immediately below the North <br /> <br /> <br />Sterling inlet canal, During the l5-year study period the Tetsel Ditch <br /> <br /> <br />diverted an average of 5,100 acre-feet per year. The lowest annual diver- <br /> <br /> <br />sion was 2,600 acre-feet in 1947 and the largest was 6,400 acre-feet in <br /> <br /> <br />1956 and 1961, No Tetsel Ditch Company officials were interviewed, but <br /> <br /> <br />based on similar small systems close to the river the efficiency of delivery <br /> <br /> <br />is estimated to be about 75 percent, Most of the loss involved would be to <br /> <br /> <br />seepage. <br /> <br />Johnson and Edwards Ditch. The Johnson and Edwards Ditch diverts from <br /> <br /> <br />the river using the Prewitt Reservoir inlet canal. It serves approximately <br /> <br /> <br />1,700 acres of irrigated land on the south side of the river. The average <br /> <br /> <br />annual diversion by the Johnson and Edwards system during the l5-year study <br /> <br /> <br />period was 3,200 acre-feet. The lowest annual diversion was 2,100 acre-feet <br /> <br /> <br />in 1959 and the highest was 5,200 acre-feet in 1952. The estimated delivery <br /> <br /> <br />efficiency for the Johnson and Edwards Ditch is 75 percent. <br /> <br />. <br /> <br />-36- <br />