INTAKE PARAMETERS FROM ADVANCE AND WETTING PHASES OF SURFACE IRRIGATION

A volume balance approach to determine the parameters of the Kostiakov or modified Kostiakov infiltration equations in border and furrow irr igation is presented. The approach requires measured data from the adv ance phase, the postadvance (wetting) phase, or both, resulting in thr ee different procedures to characterize infiltration. Using the entire field length the procedures provide infiltration parameters that are more representative of an actual irrigation. The volume balance comput ation performed by the end of the wetting phase makes it possible to d etermine the accuracy of each equation that can represent the infiltra tion process for a particular application. Inflow discharge, water fro nt advance, average flow cross-sectional area, and outflow discharge a re the required field data. Several mathematical approximations are su ggested in order to simplify the field work and the amount of computat ion. The use of empirical factors to improve data fitting is discussed . By providing irrigation system performance information during an irr igation, this procedure can be easily adapted to guide decisions durin g realtime operation.