||Hydraulics of Low-Gradient Border Irrigation Systems.
Evan, Norman A. ;
Heerman, Dale F. ;
How, Orlando W. ;
Kincai, Dennis C. ;
||Colorado State Univ., Fort Collins. Natural Resources Center.
||Completion-19; DI-14-01-001-1883; OWRR-B-024-COLO; 01545,; B-024-COLO(1)
( Irrigation ;
Fluid infiltration ;
Soil water ;
Surface irrigation ;
Clay soils ;
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Surface flow data from field experiments on 21 borders were analyzed to determine parameters characterizing infiltration and surface retardance. Infiltration constants for a logarithmic intake function were determined by the use of cylinder infiltrometers and by using the entire border as an infiltrometer. The borders were constructed on a clay loam soil which exhibited cracking when dry. The infiltration analysis showed that for this type of soil, the cylinder infiltrometers underestimate the infiltrated depth by nearly 50 percent. Resistance parameters were calculated by a volume balance procedure after the intake constants were determined. A mathematical model simulating border irrigation was developed by using the theory of unsteady hydrodynamics. The momentum and continuity equations were solved numerically by the method of characteristics. The advance of the wetting front was controlled by the requirement that the sum of the surface storage and infiltrated volumes must equal the total volume applied at all times. Dimensionless curves were derived relating the average surface storage depth to the advance distance. (Author)