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<br />of Income for many landholders, so the average Irrigated land holding Is only <br /> <br />28 acres. <br /> <br />. <br /> <br />~ Determinino Irriaatlon Parameters. The model assumed the five crops could <br />~ <br />Q be grown with any of ten combinations of water application technologies and <br />00 <br />management techniques. Six Irrigation technologies are considered: earthen <br /> <br />ditch with siphon tubes, concrete lined ditch with siphon tubes, gated pipe, <br /> <br />ported ditch, semi-automated ported ditch, and cab1egatlon.5 <br /> <br />Four water application options are Included. <br /> <br />The first '1s the <br /> <br />conventional irrigation technique for the Grand Valley of 24 hour irrigation <br /> <br />sets for row crops and 48 hour sets for hay and grass. This approach normally <br /> <br />results in very high tallwater losses and excessive deep percolation, <br />especially in the first two Irrigations of the year when so11 permeabfllty Is <br />higher. One technique to raise efficiency Is to shorten the irrigation timing <br />to 12 or 18 hour sets. This can be combined with the initial use of two siphon <br />tubes per furrow, cutting back to one tube after the entire length of the <br /> <br />furrow has been wetted. This technique, called manual cutback, saves water and <br /> <br />Increases efficiency; It Is more easily done by adjusting the rate of flow from <br /> <br /> <br />gated pipes or ported ditches. Finally, semi-automated systems (such as ported <br /> <br /> <br />ditch with timer-operated drop gates) and cab1egatlon can shorten Irrigation <br /> <br /> <br />time and change sets as well. Thus, the ten irrigation options are 1) earthen <br /> <br /> <br />ditch, 2) earthen ditch with short sets, 3) lined ditch, 4) lined ditch with <br /> <br />short sets,S) gated pipe, 6) gated pipe with manual cutback, 7) ported ditch, <br />8) ported ditch with manual cutback, 9) semi-automated ported ditch, and 10) <br />cab1egatlon. <br />An additional management response to salinity control Incentives Is <br /> <br />partial land retirement. This alternative was limited to 8,000 of the 50,000 <br /> <br />7 <br />