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<br /> <br />Il:JD 1'1 <br /> <br />- 2 - <br /> <br />WATER LOSSES <br /> <br />A. Runoff losses - surface irrigation <br /> <br />Research or survey data on specific farms for the area of the <br />Blue River Basin is not available. However, tests on demonstration <br />farms and fields on fine textured upland soils of this area and <br />other areas resulted in the following runoff losses. <br /> <br />Table 1 - Runoff Losses on Demonstration Fields <br /> <br />1960 <br />1961 <br />1965 <br /> <br />22 - 37% <br />28% <br />40% <br /> <br />Soil compaction, soil saturation, soil texture Bnd percent of slope <br />were factors in the variation of runoff. <br /> <br />Irrigation practices used by surface irrigators can be classi- <br />fied into four categories. Table 2 estimates the percent of runoff <br />according to the irrigation management practice used Bnd the percent <br />of irrigators in the Elue River Basin using a particular practice. <br /> <br />Table 2 <br /> <br />Irrigation Management Practice <br /> <br />Estimates <br />% Water Runoff ~ Irrigators <br />UsinF l1ethod <br /> <br />l. Large s tre am size at start wi th <br /> later cuttack stream adjustmen t 10-20 10 <br />2, Maximum ncn-erosi ve stream, no <br /> cutback 30-35 36 <br />3. Small stream; or stream shut off <br /> at end of run, or blocked row ends 5-10 45 <br />4. tlaxi= non-erosive stream using a <br /> recovery or retarn system 0 9 <br /> <br />Practice 1 offers an opportunity to effect a water saving <br />coupled with good soil moisture patterns. Few irrigators havL or <br />will adopt this particular practice because of the extra a~ouot of <br />labor involved in readjusting stream size following the in~tial <br />adjustment. <br /> <br />Practice 2 involves running a full furrow stream of wat~r at <br />the maximum non-erosive level and continuing at that rate of flow <br />for the desired time. Runoff is excessive but water dis~ribution <br />is nearly uniform within the field. Low cost of irrigation water <br />and high labor costs encourages this practice. <br /> <br />Practice 3 usually results in poor distribution of w3ter with- <br />in the field and yields are reduced. Over or under irrjs?tion of <br />crops results in portions of the field in which ~ater le~~~as nutri- <br />ents below plant root depth or limits amount of available soil mois- <br />ture within the root zone. Although widely used, ~his practice re- <br />duces crop yields. Deep percolation can result in additional neees <br />