Subsurface Water Distribution in Surface Irrigation

Abstract

Experimental data on subsurface water distribution show that the uniformity of water distribution is greatly dependant on the manner in which the infiltration rate changes with time after the initial wetting. The other factor of major importance in the uniformity of water distribution along runs is the time required for the wetting front to traverse the run. Equations are developed describing the subsurface water distribution in terms of three dimensionless ratios, one each for time quantities, distances along runs, and water application quantities. The subsurface water distribution uniformity is greater for soils in which the infiltration rate decreases rapidly with time than for soils in which the infiltration rate remains relatively constant, provided the other conditions during the irrigation are similar.