Hydrograph Shape and Border Irrigation Efficiency

Abstract

Sloping borders with free outflow were studied to determine the effect of inflow hydrograph shape on maximum application efficiency. A zero-inertia model describing the movement of water along the border run with infiltration was used to predict the maximum application efficiency for five inflow hydrograph shapes. The irrigation parameters considered were four infiltration families, three slopes, three roughness coefficients, two field lengths, and three volumes. The maximum application efficiencies averaged over all combinations of the irrigation parameters for the five hydrographs were as follows: constant, 68%; cutback, 77%; cablegation, 59%; modified cutback, 80%; and modified cablegation, 78%. Efficiencies for each hydrograph shape ranged from zero to 92%, with the low values occurring for high infiltration rates and roughness, small slopes, long fields, and low volumes of application. The infiltration family and its cross products with the other irrigation parameters were the most important variables affecting the maximum application efficiency for the five inflow hydrograph shapes.