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<br />APPENDIX G <br /> <br />. <br /> <br />'Principles and Practices for Prevention and El1mination <br />of Mosquito Sources Associated with Irrigation <br /> <br />A. <br /> <br />~r01ect Conveyance and Distribution Systems <br /> <br />" <br /> <br />l. Lining or other satisfactory seepage control measures <br />should be provided for all sections of canals and laterals <br />located in porous material where excessive leakage would <br />result in water-logged areas, seeps, and ponds. <br /> <br />2. Drains should be installed to prevent ponding of excess <br />irrigation water and natural runoff along the upper side <br />of canals and laterals. All drainage crossing or inlet <br />structures should be placed on grade to avoid ponding. <br /> <br />3. Borrow areas should be self-draining to keep them fraD <br />retaining ponded water. <br /> <br />4. Where possible, provision should be made to prevent <br />turnouts and other hydraulic structures from retaining <br />residual water when they are not being used. <br /> <br />S. Effective measures should be provided to prevent ponding <br />of leakage from water control structures. <br /> <br />6. Every effort should be made to establish'delivery schedules <br />whicb will provide farmers with adequate but not excessive <br />amounts of water at proper intervals to insure efficient <br />irrigation of the crops concerned. <br /> <br />7. Vegetation and debris which would retard normal flows <br />should be periodically removed from conveyance channels, <br />water control structures, and drains. <br /> <br />. <br /> <br />B. Pro1ect Drainage Systems <br /> <br />l. Trunk drainage systems should be installed to insure <br />complete removal and proper disposal of excess irriga- <br />tion water, natural runoff, and seepage from both <br />irrigable and nonirrigable lands affected by the distri- <br />bution and use of irrigation water on the project. <br /> <br />G-l <br />