Reliability of Optimized Furrow‐Infiltration Parameters

Abstract

The reliability of furrow‐infiltration parameters computed from advance measurements was analyzed. Lumped parameters were obtained using the least‐squares approach. The objective function was formulated using advance time and velocity observations as a function of distance. Predicted values were calculated with a finite difference hydrodynamic model with wetted perimeter‐dependent infiltration. The Extended Kostiakov equation was used to describe infiltration‐rate variation with time. Reliability was examined by comparing recorded total intake and runoff with values predicted with the single average parameters. Results showed that reliability of coefficients depends on the relationship between infiltration variability, furrow length, and inflow rate. In particular, relatively short irrigation times hampered the identification of the steady infiltration rate. Spatial trends in infiltration rates affected the reliability of parameters as well. The magnitude and nature of the resulting prediction errors was found to be dependent on the direction of the trend relative to the flow direction. In general, velocities appeared to provide better estimates of average infiltration characteristics than advance times but weighted least squares may be required to compute the parameters from field data.