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<br />APPENDIX F <br /> <br />. <br /> <br />Principles and Practices for Prevention and Elimination <br />of Mosquito Sources Associated with Irrigation <br /> <br />. <br /> <br />A. Project Conveyance and Distribution Systems <br /> <br />l. Lining or other satisfactory seepage control measures should <br />be provided for all sections of canals and laterals located <br />in porous material where excessive leakage would result in <br />waterlogged areas, seeps, and ponds. <br /> <br />2. Drains should be installed to prevent ponding of excess <br />irrigation water and natural runoff along the uWer side <br />of canals and laterals. All drainage cross ing or inlet <br />structures should be placed on grade to avoid pending. <br /> <br />3. Borrow areas should be se If -draining to keep them frOlll <br />retaining ponded water. <br /> <br />4. Where possible, provision should be made to prevent turn- <br />outs and other hydraulic structures from retaining residual <br />water when they are not being used. <br /> <br />5. Effective measures should be provided to prevent ponding of <br />leakage from water control structures. <br /> <br />6. Every effort should be made to establish delivery schedules <br />which 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 />B. Project Drainage Systems <br /> <br />1. Trunk drainage systems should be installed to insure <br />complete removal and proper disposal of excess irrigation <br />water, natural runoff, and seepage from both irrigable <br />and nonirrigable lands affected by the distribution and <br />use of irrigation water on the project. <br /> <br />F-l <br />