ANALYSIS OF FURROW IRRIGATION AND ESTIMATION OF INFILTRATION PARAMETERS

Abstract

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. Furrow infiltration varies with different variables and is a complex process for modeling infiltration over the field. Hydraulic analysis of furrow irrigation system is important for proper water management at an irrigation field level. In the present study Kinematic wave numerical model for predicting 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 equation, Newton-Rapson 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. Furrow irrigation experiments are also conducted to verify the model prediction. Later, the numerical model is coupled with Sequential Unconstrained Minimization Technique (SUMT) to estimate the Kositakov-Lewis infiltration parameters from the furrow advance data. The performance of the optimization algorithm is studied by generating Synthetic data and checking whether the optimization converges to true values or not.