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<br />~}~;} <br /> <br />" <br />"'.:-; <br /> <br />,~ <br />.t":.:.~ <br />~ <br />IL <br />(,p.1 <br /> <br />In contrast, the differences between sites 16 and 37 can be attributed <br />to differences in soil type and management practices" The irrigation <br />system and crops are s imi I ar but there is a vast difference in deep <br />percolation between the two sites, 5.9 inches at site 16 and 36.4 <br />inches at site 37. The data to date indicate that Hanksville soil is <br />harder to manage because of uneven water distribution due ,to shaley <br />so i I ; <br /> <br />Nine of the monitored sites had deep percolation losses greater than <br />the average for 1991, 15.9 inches per acre. Sprinkler sites, 33 and <br />36 had some deep percolation but was less than in .1990. A field test <br />of sprinkler application rates at these sites indicated that the <br />inflow meters were underestimating the amount of flow to the <br />sprinkle'rs. Adjustment of data showed water appl ica.tion to be higher <br />than previously estimated and this resul~ed i~ showing larger deep <br />percolation than before. <br /> <br />The actual deep percolation seems to be considerably higher than the <br />15% of ETa targeted. A target of 15% deep percolation is used as <br />being practical and achievable. However, until several .years of data <br />are collected, it will be difficult to determine the amount of deep <br />percolation required in the Grand Valley to leach salts below the root <br />Z9ne. <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 />'i rr i gat ion, the app I i,cat i on eff i c i ,ency wi I I be very high .and may not <br />necessar i I y be an i nd i cat i on of good i rr i gab on. The seasona I <br />application for all sites (surface and sprinkler) is provided in Table <br />2. The tab I e shows app I i cat ion eff i c i ency to be 43% :for surface <br />irrigation sites (23 sites) and 67% for sprinklers (3 sites). When <br />annual and perenn i al crops are taken into account, the eff i c i ency is <br />35' and 50% respectively. Appl ication efficiency for individual <br />irrigation events are sho~n und8~ site summaries in Appendix B. <br /> <br />The overall seasonal irrigation application efficiency in 1991 was <br />45%, I esS than 1988 and 1989 <Tab I e 4), Th i s is cons i derab I y bette,r <br />than 1985, which had an efficiency of 30%. A comparison of irrigation <br />monitoring data from 1985 to 1989 shows that during this period <br />irrigation efficiency increased progressively from year to year which <br />resu I ted in I ess water app I i cat i on, reduced runoff and deep <br />percolation (Table 4). <br /> <br />Of the 23 surface irrigated sites monitored In 1991, only six had <br />irrigation efficiency 50% or more, considerably less than 1989 and <br />1988 where half the sites had more than 50% efficiency. Eight <br />producers increased the i r eff; c i ency in 1991 but an equa I number <br /> <br />17 <br />