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<br />application efficiency dropped by 2% due to increase ~r., gross water <br />application and deep percolation. This usually happens during the <br />the first year of site improvement. In 1994, efficiency is <br />expected to increase with better water application/distribution and <br />~ deep percolation reduction. <br />"", <br />~ Evaluation of deep percolation data for the 20 surface sites <br />.~ indicate that some of the largest deep percolation is occurring at. <br />sites.with Hanksville soil. . This is one pf the dominant soils in <br />the west end of the Grand Valley. The Hanksville soil is usually <br />only 15 to 20 inches in depth with.shale layers at 20" to 40" <br />depth. The total water holding capacity is only. 3 to 4 inches and <br />.~ is therefore hard to manage in terms of irrigation scheduling .and <br />water management. In this soil, water takes an extended amount of <br />time to reach the end of the furrow because of uneven water <br />distribution. Water tends to go underneath through surface cracks <br />and-fiows over shale layer and eventually to the Colorado River. <br />Farmers lteepirrigating till all the furrows are wet to the end <br />. . which means that at some sites it takes more than 5 days to <br />irrigate one set. .< <br /> <br />~~;~}; <br /> <br />I <br />. , <br /> <br />I <br /> <br />...1 <br /> <br />Seven of the monitored sites had deep perr~lation <br />than the average for 1993, 11.8 inches per acre. <br />33 and 36 had very little deep percolation. <br /> <br />In 1993, about half the sites monitored had deep percolation losses <br />greater .than the 15% of ETa. This is considerably better than in . <br />the-past where only'one~third of the farmers stayed below the 15% ;Y;i <br />level. A target of 15% deep percolation is used as being practical' <br />and achievable. However, until several more years of data are <br />collected, it will be difficult to determine the exact amount of <br />deep percolation required to leach salts just below the root zone <br />and to prevent excess percolated water from carrying more salts to <br />the Colorado Rive~. Currently, high deep.percolation leaches salt <br />past. . the root zone to the Co lor ado River. . <br /> <br />losses greater <br />Sprinkler sites, <br /> <br />Deep percolation reduction of 4.9 inches per acre in 1993 compared <br />to 1992 could be related to wet spring weather in 1993; Theabove <br />normal precipitation in May made it impossible for many farmers to <br />get to their. fields and resulted in the irrigation season.being <br />delayed for a month. Fields in corn, orchards, and beans were not <br />irrigated until early June; other fields in alfalfa, and small <br />grain; got their first irrigation in May instead of April.' This <br />delay in irrigation could have resulted in reduction of gross water <br />application by 4.5 inches and deep percoiation 4.9 inches compared <br />to 1992. However, run-off increased slightly in 1993 compared to <br />1992. This could be due to compaction of the fields because of the <br />use of heavy equipment on moist fields. ' <br /> <br />Application Efficiency: Application efficiency is calculated as <br />inflow minus outflow minus the deep percolation divided by' inflow, <br />expressed as a percentage. As a result, when there is under- <br /> <br />20 <br />