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<br />DRAINAGE WATER REUSE STRATEGY
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<br />river. This relatively small volume of water is assumed to be disposed of by
<br />some other means (such as evaporation, desalting, deep-aquifer injection, etc.).
<br />The detailed results of these three different drainage water management
<br />strategies (I, II, III) are given in Tables 1,2 and 3, respectively. A summary of
<br />these results is given in Table 4 and in Figs. 2-6 to facilitate the comparison.
<br />The percentage losses in crop yield expected under the three strategies are 22,
<br />. 49 and 0 for strategies I, II and III respectively, These results show that the
<br />normal loss of crop yield that results when drainage water is returned to the
<br />good-quality water-supply and the "blend" (the river in this case) is subse-
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<br /><:
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<br />TABLE 2
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<br />Results of simulation under conditions of Strategy II; drainage from bean, alfalfa and wheat crops
<br />used to irrigate cotton; drainage water from cotton discharged back to the river"
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<br />Crop V., L ECiw V;w EC, vdw ECdw
<br />Firstproject (volume of river=500; Ec=0.50 dSjm)
<br />Beans 25 0.2 0.50 31.25 0.64 6.25 2.50
<br />Alfalfa 40 0.1 0.50 44.44 0.94 4.44 5.00
<br />Wheat 25 0.2 0.50 31.25 0.64 6.25 2.50
<br />Cotton 14.4 0.15 3.15b (16.94 )' 4.76 (2.54) 21.0
<br />Second project (volume of river= 395.6; EC = 0.632 dSjm)
<br />Beans 25 0.2 0.63 31.25 0.81 6.25 3.15
<br />Alfalfa 40 0.1 0.63 44.44 1.18 4.44 6.30
<br />Wheat 25 0.2 0.63 31.25 0.81 6.25 3.15
<br />Cotton 14.4 0.15 3.98b (16.94 )' 5.99 (2.54) 26.5
<br />Third project (volume of river"; 291.2; EC = 0.858 dS j m)
<br />Beans 25 0.2 0.86 31.25 1.11 6.25 4.30
<br />Alfalfa 40 0.1 0.86 4.44 1.62 4.44 8.60
<br />Wheat 25 0.2 0.86 31.25 1.11 6.25 4.30
<br />Cotton 14.4 0.15 5.43b (16.94)' 8.19 (2.54) 36.2
<br />Fourth project (volume of river = 186.8; EC = 1.338 dSjm)
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<br />Loss
<br />in yield (%)
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<br />Beans 25 0.2 1.34 31.25 1.73 6.25 6.70 15
<br />Alfalfa 40 0.1 1.34 4.44 2.52 4.44 13.40 5
<br />Wheat 25 0.2 1.34 31.25 1.73 6.25 6.70 0
<br />Cotton 14.4 0.15 8.46b (16.94 )' 12.76 (2.54) 56.4 25
<br />Remaining volume of river =82.4; EC = 3.03 dSjm)
<br />
<br />.Volume diverted from river for irrigation in each project = 106.94 units; volume of drainage re.
<br />turned to river from each project=2.54 units.
<br />btJ'he weighted average EC of the drainage waters from the bean, alfalfa and wheat crops.
<br />cThe cumulative volume of the drainage waters from the bean; alfalfa and wheat crops.
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