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<br />MAY 1982 <br /> <br />TABLE IV-l,SillIMARY OF ANNUAL SALT LUADING AND POTeNTIAL REDUCTIUN <br />ATTRIBUTED TO IRRIGATED AGRICULTURE. <br />McELMO CREEK SALINITY CUNTROL STUDY, COLORADO. <br /> <br />Source of Loading presentl , I. Plan Number <br /> 1 I 2 ') 3 I 4 I 5 I 6 <br /> -- -- --------- -- -- --tons- --- - -- --------- <br />Group Ditches BOOe 900e BOOO e e e U <br />OnFarm Ditche~ 2/3/ 14000 1500e 1500l 14000 30Ue 2000 0 <br />Deep Percolat1on - - 32000 36000 2400e 22000 20000 20000 33000 <br />Totals 5400l 6000e 4700e 36000 23000 2200C 33000 <br />Potential for Reduction <br />Group Di tches --- -1000 l ,8000 800e bOUO 8UOO <br />OnFarm Ditches --- -1000 -lOOe e 11000 12UOO 140UO <br />Deep Percolation --- -4000 8000 10000 1200C 12000 -1000 <br />Sub-Total ::.' --- -600e 7000 1800C 3100C 32000 21000 <br />Potential for Prevention <br />Irrigation <br />Water Management --- --- 600e 600e 6000 6000 0 <br />Total Salt Reduction --- -6000 13000 2400l 3700l 3800C 21000 <br /> <br />l/Plan 2 is the Management Only Plan and will have little effect on reducing <br />salt loading from ditch seepage. The plans are further described in <br />section 5. e <br />2/The present case and Plans 1 and 2 include 5,000 tons/year from Navajo <br />Wash, a separate tributary to the San Juan River. <br />3/ Plans 3, 4 and 5 include about 2,000 tons/year from Navaj 0 Wash. <br />I/Reduced salt load going to the Colorado River. Plans 2 through 5 will hav <br />an additional 6,000 ton prevention benefit due to management of supplemental <br />irrigation water available from the Dolores Project. <br /> <br />SALT LOADING <br /> <br />Salt loading accounts for salt pickup through deep percolation from <br /> <br />field irrigation, and seepage from earthen ditches. Irrigation water <br /> <br />delivered to the farms has an average salt concentration of about 200-300 <br /> <br />milligrams per liter (mg/l). Base flow returning to McElmo Creek has a <br /> <br />concentration of about 2,600 mg/l. Salts are concentrated in soil moisture <br /> <br />through evaporation and as plants extract water and minerals needed for <br /> <br />growth. Excess irrigation water lost through deep percolation, seepage from <br /> <br />earthen delivery ditches and from tailwater runoff increases the total salt <br /> <br />load by passing through the saline soil and shale formation and G~~~J~ <br />IV-5 <br />