SIMULATING FURROW IRRIGATION WITH DIFFERENT INFLOW PATTERNS

Simulation of sloping furrows with free outflow was accomplished to assess the effect of inflow pattern on maximum application efficiency. For five inflow hydrograph patterns, the maximum application efficiency was predicted utilizing a zero inertia model, which describes the movement of water in the furrow with infiltration. The irrigation parameters considered were four infiltration families, three slopes, three roughness coefficients, two field lengths, three volumes, and one furrow shape and size. "The maximum application efficiencies averaged over all combinations for the five inflow patterns were constant rate, 58%; cutback, 64%; cablegation, 51%; modified cutback, 64%; and modified cablegation, 62%. Efficiencies ranged from zero for each inflow shape to a magnitude that differs from one to another, with the low values occurring for high infiltration rates and roughness, small slopes, long fields, and low volumes of application. While the constant rate was found to be least sensitive to changes in the input parameters, cutback and modified cutback were most sensitive. Cablegation and modified cablegation were moderately sensitive to changes in the input parameters.