Water front advance in irrigation borders

Abstract

The time-distance relationship in water front advance is an important factor to be determined in designing an efficient border irrigation system. Water front advance in a border strip is a case of spatially varied unsteady flow with decreasing discharge. General solutions of the water front advance problem in borders have been developed by earlier workers. Extensive field studies during pre-sowing and post-emergence irrigations revealed that the functional relationship between accumulated infiltration y and elapsed time t could be represented best by the equation y = a tα+b, in which a, α and b are characteristic constants. Particular solutions of the equations obtained by previous workers were developed to meet the above infiltration equation. Two different equations were necessary to fully describe the water front advance-time relationship, one when the value of t is small and another when t is large. The limiting conditions for using the 2 equations were established. Field studies under vegetated and non-vegetated border strips revealed that a close relationship existed between computed and measured values of the advance distance as a function of the elapsed time. Equations to express empirically the functional relationship between advance distance and elapsed time, and advance distance and accumulated infiltration were developed and their limitations defined.