Sensitivity of a furrow irrigation model to input parameters

A furrow irrigation model called SIRMOD was evaluated for its sensitivity to the input parameters under two different field conditions, viz., long furrows on cracking clay soil and short furrows on sandy soil. The input parameters included inflow rate, longitudinal slope, roughness coefficient, infiltration parameters and furrow geometry parameters. The parameters were varied between -50% and +50% of the values in the control simulation. The output parameters considered in the sensitivity analysis were advance times, recession times and runoff. The study shows that the model sensitivity varied considerably with the input parameters. For a given input parameter, the sensitivity also varied with the output parameters (i.e., advance times, recession times or runoff) considered in the analysis and with factors such as soil type, furrow length and slope. The sensitivity was low or negligible for the furrow geometry parameters and was moderate to high for the flow rate, infiltration characteristics, roughness coefficient and slope. In general, the model input parameters that must be measured with the highest possible accuracy include the flow rate, infiltration characteristics, the roughness coefficient and slope.