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<br />4 <br /> <br />to millimhos per em) and the EC of lesser saline soils which is <br />EC x 10 to the minus 3 which is micromhos per em. <br /> <br />Water quality records with both EC and TDS provide a specific <br />relationship. TDS can be approximated by multiplying EC by a <br />factor of 640 for lesser saline samples and 800 for hypersaline <br />samples. In the Uintah Basin some samples approached 1000. <br /> <br />The adverse impacts from salinity depends on the use of the water <br />or soil. An irrigation water of EC < 1.0 mmhos/cm poses little <br />threat to most crops, while an EC > 3.0 mmhos/cm restricts the <br />growth of most crops. A soil with an EC > 4.0 mmhos/cm in the <br />soil saturation extract is characterized as a saline soil. <br /> <br />Water supplies from snow melt areas of the Colorado River Basin <br />usually have salinity concentrations less than 200 mg/l. <br />Drainage return flows from irrigation vary from 100 mg/l in upper <br />mountain meadows to over 4,000 mg/l in the lower Colorado <br />valleys. Each area is unique. The salinity concentrations of <br />the oceans' is about 35,000 mg/l or 3.5 percent salt. <br /> <br />Salinity concentration can be expressed in tons per acre foot. <br /> <br />1 Ton <br /> <br />2000 I <br /> <br />1,000,000 <br /> <br />----------- = ----------------------------- = 735.8 ppm or mg/l <br /> <br />acre foot <br /> <br />43,560 cu. ft. X 62.4 I/cu. ft. <br />1 ton/ac ft = 736 mg/l <br /> <br />A water supply with 200 mg/l salinity has < 0.27 ton salt per <br />acre foot. Drainage water with 4,000 mg/l salinity concentration <br />has 5.45 tons of salt per acre foot of return. Therefore, the <br />salt pickup by deep percolating and seepage in this example is <br />5.18 tons/ac ft. <br /> <br />This can be defined better by considering surface runoff, deep <br />percolation, consumptive use ( T), and drain return. <br />r > <br />Supply 10 ac ft 2.5 ac ft - ET 6 ac ft - Surface runoff <br />200 mg/l 200 mg/l (1.6 tns/ac) <br />(2.7 tns/ac) <br /> <br /> <br />~ <br /> <br />Drain Return <br />1.5 ac ft - <br />4,000 mg/l <br />(8.2 tns/ac) <br /> <br />1.5 ac it - Deep <br />(1.1 tns/ac) Percolation <br /> <br />--------------------------------------------------------------- <br /> <br />Inflow = outflow (surface + deep perc.) <br />Salt balance: <br />2.7 tns/ac = 1.6 tns/ac + 1.1 tns/ac <br /> <br />With Salt pickup: <br />2.7 tns/ac = (8.2 + 1.6) <br />Salt pickup = (8.2 + 1.6) -2.7 = 7.1 tns/ac <br />