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110"'85 _ Li.... . Establishing field input conditions, Soil associations were trans- ferred to the computer model grid system from soil survey maps of Sedgwick and Logan counties (USDA, 1969; USDA, 1977). The soil series making up these associations were determined and evaluated as to texture and slope. Each grid point associated with an irrigation area (i.e., ditch) was identified by the appropriate soil association. The number of grid points of each soil association was tabulated for each irrigation area. The Soil Conservation Service intake family (USDA, 1974) was determined for each soil association, based upon its surface texture, using Figure 2. These intake families are the water intake rate of the soil in inches per hour at extended times. The soil series information gave information on land slopes. The average soil association properties for the study reach are summarized in Table 5. Table 5, Soil Association Average Properties Lower Platte River Valley Irrigated Land, Colorado . Plan t Field Soil availa ble Surface Intake irrig. association water Slope texture family eff. (in. ) (%) (in. /hr. -1) (ea. ) 2 L 8,4 1 - 3 loam 0.9 0.45 3 L 11. 6 0 1 si. c. loam 0.6 0.55 4 L 5.3 5 + 1. sand 2.0 0.45 5 L 5,7 5 + 1. sand 2.0 0,45 7 L 5.4 5 + f. s, loam 1.5 0.45 9 L 5.7 3 - 5 loam 0.9 0.45 11 L 10,7 5 + loam 0.9 0.30 14 L 11. 7 5 + loam 0,9 0.30 2 S 11.0 1 - 3 loam 0,9 0.45 3 S 8.4 1 - 3 loam 0.9 0.45 4 S 4.4 5 + f. sand 3.4 0.30 5 S 6,0 5 + gravelly sa loam 2.0 0.45 . Determination of initial values of farm irrigation system efficiencies. As indicated earlier, there is no information on farm irrigation system effi- ciencies which relate this parameter to slope, requirement and intake. How- ever, it is recognized that the parameter is indeed dependent upon these -28-