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<br />000383 <br /> <br />'~"i: ,. 1 . <br /> <br />High canal losses due to seepage occur on about 1,720 mi les of <br />irrigation supply canals and distribution laterals. This Is a major <br />problem In the North Platte and Middle Platte River Basins. The instal- <br />lation of canal lining would increase the amount of water avai lable to <br />irrigators of some systems by as much as 50 percent. In addition, It <br />would remove one of the causes of rising water tables. <br /> <br />It should be noted that under the U. S. Supreme Court Decree on <br />division of the North Platte River water, the areas between the Trl-State <br />Diversion Dam and Lake McConaughy are expected to obtain their water <br />supplies from return flows of the canal systems in the North Platte <br />Project. Records for the last ten years show that the average annual <br />discharge of the drains between the state line and Bridgeport averages <br />100,000 acre-feet less than that for the ten year period 1931-40 which <br />was used as a basis for the Supreme Court Decree. Further reduction <br />of the canal losses along this river reach could severely affect the <br />water supply for the Platte River system below Bridgeport. Should this <br />happen, adjustments in upstream diversions may be required to meet the <br />demands of prior downstream rights. <br /> <br />Risinq Water Tables. Reducing seepage by lining canals and laterals <br />would alleviate the problem of rising water tables. In addition on-farm <br />drainage measures are needed on about 196,000 acres to lower and maintain <br />the water level below root zones. It is estimated that 840 mi les of <br />drain channels are needed to provide outlets to farm drainage systems. <br />This Is a major problem in the North Platte and Middle Platte River <br />Basins. Using wells to provide part of the water supply in areas <br />serviced by surface water systems wi II help maintain water levels below <br />root zones. <br /> <br />Other Losses. The reductIon of losses from flooding and degrading <br />channels may require the installation of flood prevention and grade <br />stab! lization measures. These needs are discussed in Chapter 7. Improved <br />maintenance Is needed In many small systems. In the North Platte River <br />Basin there are 28 small systems serving about 75,000 acres annually, <br />an average of 2,700 acres per system. Higher unit costs and lack of <br />proper maintenance on these systems are problems. <br /> <br />Ground Water Systems <br /> <br />Opportunities to reduce excessive use of ground water due to irri- <br />gation pumpage include the fol lowing: <br /> <br />\. Limit withdrawals to the Irrigation water requirements <br />for the crops grown, <br /> <br />2. Regulate annual withdrawals from the ground water reservoir <br />to prevent serious declines in water levels, <br /> <br />3. Locate and divert surface water supplies for direct use <br />and storage to supplement ground water supplies In areas <br />of seriously declining water levels, and <br /> <br />42 <br />