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<br />and 5,130 acres poorly drained. Crop losses due to
<br />salinity and irrigation method, projected on the basis
<br />of 40,000 irrigated acres, are shown in Table 9.
<br />
<br />ImperIU V.uey IrrIgation DIstrIct. The Imperial
<br />Valley Irrigation District is comprised of about
<br />470,000 acres of irrigated crop land which was divided
<br />into 59,500 acres of well drained, 87,500 acres of
<br />moderately drained, 222,000 acres of poorly drained,
<br />and 101,000 acres of very poorly drained soils
<br />(Appendix 2). Yield losses to be expected for tbe 13
<br />major crops are projected on the basis of salinity level
<br />and irrigation method and summarized over soil
<br />drainage classes in Table 10.
<br />
<br />Cnaehella V.uey County IrrIgation District. Tbe
<br />44,000 major crop irrigated acres of tbe Coachella
<br />Valley were partitioned into 38,030 acres of well
<br />drained, 2,460 acres of moderately drained, 3,270
<br />acres of poorly drained, and 250 acres of very poorly
<br />drained soils. The expected yield decrements due to
<br />increasing salinity in the irrigation water are
<br />summarized over soil drainage classes in Table 11.
<br />
<br />Plio Verde IrrIgation DIstrIct. The Palo Verde
<br />Valley has about 95,700 acres of 10 major crops
<br />divided into 28,100 acres of well drained, 26,700 acres
<br />of moderately drained, 22,500 acres of poorly drained,
<br />and 18,400 acres of very poorly drained soils. Tbe
<br />impact of increasing salinity on eacb crop is
<br />summarized in Table 12.
<br />
<br />PaeIfIc C_ Areas. Colorado River water used in
<br />the coastal areas is pumped through the Colorado
<br />aqueduct of the Metropolitan Water District of
<br />
<br />Southern California. The study of yield effects of
<br />increased salinity narrows to the region served by the
<br />first San Diego aqueduct because of substantial water
<br />blending in otber areas. The areas. expected to be
<br />impacted by Colorado River salinity comprise 34,821
<br />irrigated acres of whicb 9,054 acres of well drained
<br />soils, 17,739 acres of moderately drained soils, and
<br />8,028 acres of poorly drained soils. Salinity impacts on
<br />the 10 major crops are summarized over soil drainage
<br />classes in Table 13.
<br />
<br />VALUE OF DAMAGES IN AGRICULTURE
<br />
<br />The waters of the Colorado River are progres-
<br />sively increasing in salinity. Some principal dissolved
<br />constituents in the Colorado River waters are calcium,
<br />magnesium, sodium, sulfate, chloride, and bicarbon-
<br />ate. These and small amounts of other dissolved
<br />constituents, are commonly referred to as salinity.
<br />
<br />At the headwaters, tbe average salinity in the
<br />river is less than 50 milligrams per liter (mg/I) and
<br />progressively increases downstream until, at Imperial
<br />Dam, the present condition is about 865mg/1.
<br />Projections of future salinity suggest values between
<br />1200 and 1400 mg/I at Imperial Dam by 2000. Should
<br />such salinity increases be realized, severe economic
<br />impacts would affect all users in the Lower Basin.
<br />
<br />The objective of the portion of the research
<br />reported here is to project changes in cropping
<br />patterns, physical output for each crop, changes in
<br />farm management, and dollar impacts in terms of net
<br />profit (Appendix 3). The damage estimates may be
<br />
<br />Table 9. Summaf'/l of yield losses an the Indwn part of the San Carlos Irrigation Project due to increasing
<br /> saUnit'll of CAP water delivered directl'll into the San Carlos irrigation system aiul. method of irrigation,
<br /> as compared with present water quaUty and best irrigation practice, projected an the basis of 80,000
<br /> irrigated acres in the entire project.
<br /> T.D.S. of 150.000 ac. ft. of CAP. Water, mgJl
<br /> Irrigations T.D.S. of 775 900 1000 1100 1200 1300 1400
<br />Crop Per Year San Carlos
<br /> Water T.D.S. of 390,000 ac. ft. ofC.A.P.. San Carlos Blend, mg/l
<br /> 910
<br /> 858 906 945 983 1022 1060 1098
<br />Alfalfa Hay 16 321 278 321 447 505 623 748 873
<br />(Tons) 22 243 199 243 269 295 321 365 423
<br />2,760 Ac. 29 199 165 199 226 252 278 321 347
<br /> 35 156 104 156 182 191 217 243 269
<br /> Sprinkler 34 69 104 156 182
<br />Wheat (Tons) 16 5 11 16 23
<br />2,195 Ac. 22
<br />Maize (fons) 16 5 1 5 9 11 14 17 21
<br />1,810Ac. 22 2 5 9 11
<br /> 29 5 7
<br />Watermelon 16 103 90 103 139 155 182 221 252
<br />(Tons) 22 77 64 77 85 92 103 113 136
<br />425 Ac. 29 64 51 64 72 80 90 103 110
<br /> 35 46 33 46 54 59 67 77 85
<br /> Sprinkler 18 26 33 46 54
<br />
<br />9
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