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<br />C)' <br />M <br />Q <br />~ even though many of the soil and water conservation practices applied do <br />c~ result in an improvement in water quality. <br />;~-::-, <br /> <br />Possible Solutions Through Lateral and On-Farm System Improvements <br /> <br />Improved water management is needed throughout the conveyance, distribution, <br />application, and return systems. Total system emphasis should be placed on <br />diverting only the amount of water needed for crop consumptive use plus <br />those amounts needed for good system management, soil leaching, cultural <br />practices and unavoidable seepage and spillage losses. Because the source <br />of salt pick up in the underlying shale formation and alluvial aquifer, <br />overall system emphasis should be placed on reducing deep percolation and <br />maintaining positive control over return flows to eliminate mixing with the <br />more saline groundwater. <br /> <br />Within this overall system approach the improvement of laterals, on-farm <br />irrigation systems, drainage and cultural practices can playa significant <br />role. An estimated 55 percent of the salt pick up from the irrigated area <br />is attributed to seepage and runoff from farm application of irrigation <br />water. Another 20 percent is attributed to seepage from lateral canals. <br /> <br />It may be possible to get a higher degree of control over seepage losses <br />from off-farm conveyance and return flow systems than from on-farm systems. <br />Lined canals and drainage ditches can be utilized throughout the off-farm <br />systems. Whereas on-farm, the water has to be applied to the land, thereby <br />~Rrovidinq opportunity for some deep percolation and salt pick up even under <br />high management practices. The prinCiples that must be applied in securing <br />a high farm irrigation efficiency involve (1) installing lined ditches or <br />pipelines, (2) installing and using proper control structures and measuring <br />devices, (3) using,the irrigation system best adapted to the soils and crops <br />grown, (4) utilizing soils information in design and layout of irrigation <br />and drainage systems, and (5) applying the proper amount of water at the <br />proper time to meet crop consumptive use plus cultural practice requirements. <br />The practices and program outlined below are developed accordingly. <br /> <br />Lateral System: There is a need to reduce seepage by realigning and con- <br />solidating laterals and installing water control structures. This will <br />reduce salt pick up and improve water delivery, control and measurement. <br />Of the estimated 786 miles of laterals, 53 miles are presently lined or <br />piped. Seepage loss is estimated to be 0.04 cfs per mile per day, 4 cfs <br />average fora 200 day season or 64 acre-feet loss per mile per season. <br />This amounts to about 50,000 acre-feet per year. <br /> <br />The key to improving the 786 mile lateral system is (1) consolidation and <br />realignment which would e1minate an estimated 60 miles of laterals, (2) <br />lining or piping 650 miles, and (3) installation of 2,600 water control <br />structures. <br /> <br />- 9 - <br />