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o t&.) t..) C,JI BASIC STUDIES An attempt was made in this study to measure the effect of irriga- tion in the Florida area on the quality of water in the Animas River below its confluence with the Florida River. It was found that the difference in concentration, however, is scarcely discernible and is within the limits of error of measurement of both flow and quality. Florida Project, Colorado Pickup Loss Ac.-ft. Differ- (tons/ (tons/ Year or tons Inflow Outflow ence acre) acre) 195e A.F. 99,eoo 90,360 9,440 Tons 14,315 15,470 +1,155 0.08 1959 A.F. 28,260 14,300 13,960 Tons 4,900 4,365 525 0.04 1960 A.F. 73,130 60,600 12, 530 Tons 10,600 11,730 +1,130 0.08 1961 A.F. 58,490 41,430 17,060 Tons 9,100 8,970 130 0.01 1962 A.F. 67,070 48,470 18,600 Tons 10,220 10,220 0 0 "'. From the above tabulation it is apparent that there has been a very small amount of pickup measured in the river downstream from the project. The concentration of total dissolved solids in the inflowing water ranges from 0.14 to 0.17 ton per acre-foot, and that of the out flowing water ranges from 0.17 to 0.30. About 13,720 acres were irrigated prior to construction of the project facilities. The full irrigable acreage (13,720) was used in computing the pickup in tons per acre, even though some land was irrigated only once a year; therefore, the apparent losses of salt and the extremely low pickup may be due to lack of sufficient water to insure leaching. Irrigation has been practiced for many years in the Florida area without adverse effects because of the extremely good water and the good drainage conditions. The Florida project soils and the adjoining Pine River project soils are naturally low in salinity and alkalinity, and the amount of dissolved solids removed from these projects is about equal to the amount deposited. Very little increase in dissolved solids pickup is expected when the ex- panded project goes into full operation. The studies described above afford some support for the assumptions set forth earlier in the report that a pickup range of from 0 to 2 tons per acre is indicated for irrigated acreages after the initial leaching. The pickup on the Florida project is negligible and that on the Eden proj- ect will probably stabilize a little above 2 tons per acre. 26