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<br />-'6""..., <br />li i; <br /> <br />Other problems associated with establishing recharge sites in areas <br />close to the river lie in attempting to locate the sites as far from <br />the river as possible and still be over the alluvial aquifer. Near <br />the alluvial boundaries, transmissivities are lowest and depth to <br />bedrock is shallowest. Furthermore, drain-out losses to the river <br />during the irrigation season are highest in areas close to the river, <br />The sites that appear to be best suited for recharge are essentially <br />the lands in test areas I, II, and III, It is also in these areas <br />that water levels are declining due to pumpage (Hurr, et al., 1975). <br /> <br />It is estimated that about 55,700 acres would probably be affected <br />to some degree by the problems described above. This amounts to about <br />46 percent of the 120,300 acres whi ch are to be benefited by the <br />recharge scheme. The plan that is presented in this study, therefore, <br />is an optimistic one and closer investigation may require that a <br />percentage of the acreage would have to be dropped from the recharge <br />plan. <br /> <br />'Operation and Maintenance <br /> <br />In order to maintain high infiltration rates in the recharge ponds and <br />new canals, alternate periods of wetting and drying, as well as scarifi- <br />cation wi 11 be neces sary. S i ncethe seepage rates of the recharge <br />ponds and the unlined canals would be adversely affected by any <br />accumulation of sediment, it is important that sediment be removed <br />from the system ,effectively. An estimate was made of the average <br />amount of sediment which would be diverted by a ground-water recharge <br />system based on the sediment load carried in divertible flows, The <br />amount,of sediment diverted by canals in the reach between Weldona <br />and julesburg for ground-water recharge is estimated to average <br />84 acre-feet per year. <br /> <br />Maintenance of existing conveyance facilities presently occurs throughout <br />the irrigation season, whenever the ditches are dry. Therefore, the <br />required maintenance for the recharge facilities using existing canals <br />and ditches could interfere with the normal operatio~ and maintenance. <br /> <br />During periods of high flows, a substantial quantity of debris is <br />carried by the river. Since these flows are going to be diverted for <br />recharge, trashracks will be required and must be kept free of trash. <br />The existing diversion structures tend to wash out during flood flows, <br />Frequent replacement or substantial structural modifications may be <br />required. River diversions may have to be curtailed during such times, <br /> <br />47 <br />