Management Contours for Border Irrigation

Abstract

A present capability exists for analysis of a border irrigation by the use of mathematical models of the process or by the use of curves representing generalized dimensionless results thereof. The corresponding synthesis, design of appropriate inflow rates and cutoff times for a given border, currently not so well‐established, is treated herein. A management‐design chart is proposed for free‐flowing (open‐ended) borders. This is a plot of average low‐quarter infiltration depth resulting from any combination of inflow rate and cutoff time in a border with given infiltration characteristics and of given length, slope, and roughness. To minimize deep percolation losses while ensuring that the field receives sufficient water everywhere, only those irrigations in which the requirement just equals the average low‐quarter depth are considered in the design. The chart is thus a plot of requirement contours on axes of inflow rate and cutoff time. Superimposed on the plots are values of water‐application efficiency to assist in determining the optimum combination of required depth, inflow rate, and cutoff time.