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<br /> <br />llU,l c, '18 <br /> <br />- 4 - <br /> <br />high. Maintaining good farm incomes will be the largest factor in <br />increasing the use of this water evaporation saving method. <br /> <br />Irrigation evaporation losses under highly controlled research <br />conditions at the North Platte Experir.ent Station can be deduced fro~ <br />their efficiency studies of 1961. These studies showed an irriga- <br />tion efficiency of 82.5% for sprinklers and 74.L.<:: for the surface <br />method. The difference in efficienc~ between methods was attributed <br />to surface runoff, leaving evaporation at approximately 17%. There <br />was no measurable deep percolation. <br /> <br />One water conserving practice ~n the field is to limit the time <br />of exposure of the water to the atmosphere. Exposure time can be <br />limited by knowledge of the moisture conditions and irrigating at <br />the correct time. This cen be accomplished by use of soil moisture <br />sensing devices to schedule irri~ation. A field trial using such <br />instruMents showed that 4 inches of water per irrigation was suffi- <br />cient where previously the irrigator had been using 12 inches per <br />irrigation. It is estimated that only 2% of the irrigators use such <br />equipment. <br /> <br />Gross evaporation from free water surfaces is shown to range <br />from h4tl to 52" wi th a net loss of 15" to 25'1 annually in the Blue <br />River Basin. Water impoun~ments for irrigation purposes whether <br />for collection of rainfall or irri~ation r~noff and subsequent reuse <br />should be made as deep as practical with as little surface area as <br />possible to minimize evaporation potentials. No field application <br />of hexadecanol or similar fatty alcohols has bee~ made to suppress <br />evaporation. The cost of suppressants in relation to the availaLi- <br />Ii ty of other sources of ..:ater is the most probable limiting causes. <br /> <br />Evaporation from soil sur~aces can also be partially arrested <br />by tillage methods. The minimum ti~laGe method of crop production <br />can res'.llt in a soil moisture saving by exposing less moist so:!.l to <br />the atMosphere than is common ~~th conventional tillage method~. No <br />data is available on losses. I:"reediate research should be accl'r~';?lisb <br />ed to test this theory. <br /> <br />Tillage practices designed to keep residue on the surface Ano <br />to reduce compaction will increase infiltration rates and retard <br />evaporation of water fro~ the soil surface. <br /> <br />D. ~eep percolation losses <br /> <br />Deep percolation 01' water in soils is not a water loss to the <br />River Basin. Excess percolation is an econo~ic loss to the indivi- <br />dual irrigator. The losses are econo~ic as reluted to the potential <br />application of the original volume of water to 8 larger area. Water <br />wasted in deep percolation coulj be used to irrigate a large acre- <br />age. The original cost of water delivery per acre is also increas~d. <br /> <br />An additional loss i~ plant nutrients that are moved below <br />plant root zo~es. An additional hazard exits when perched water <br />tables may rise because of deep percolation and C8~se w~ter loggi- <br />of plant root zones. <br /> <br />Soil additives May also COnstitute a potential hazard in groll':'L <br />water pollution. There is a need for additional research on the <br />