KINEMATIC WAVE MODEL FOR FURROW IRRIGATION AND IDENTIFICATION OF MODEL PARAMETERS

Abstract

Hydraulics of furrow irrigation is essential for proper management of furrow irrigation system. A better understanding of the flow that advances in a furrow reduces the irrigation costs and maximizes the crop yield. A study of hydraulics of furrow irrigation can be made by combining the equations governing overland flow in the furrow with the equation governing infiltration into the soil beneath the furrow. Numerical simulation of furrow irrigation is very difficult because of the non-linearity in the governing equations and the spatial variability of the soil parameters. In the present study a Kinematic wave model of advance of water in furrow irrigation under continuous flow has been developed and verified. Numerical solution of the differential continuity equation is accomplished with a Eulerian first order integration coupled with the assumption that the flow rate and flow area are uniquely related by the Manning's uniform flow equation, Newton-Raphson method is used in solving the differential equation. Field data from the seven Colorado sites have been used to verify the model's ability in simulation of advance under continuous flow. The sites represented a variety of soil types, field slopes and lengths, and duration of the irrigation event. It is observed that the model predicts the furrow advance quite well in the initial stags of its total length, whereas the model predictions deviate from the observed values at later stages. One of the reasons for these deviations may be the empirical nature of the infiltration equation used in the analysis. The infiltration rate depends on the soil properties such as hydraulic conductivity, porosity, soil water retention characteristics and the relative wetness of the soil and it affects the furrow advance considerably.