Comparison and evaluation of different methods for inverse estimation of the infiltration equation parameters in vegetated furrows

The parameters of infiltration equations have a key role to evaluate and design irrigation systems. Therefore, in order to enhance irrigation efficiency, it is necessary that these parameters to be estimated precisely. In this study, four inverse estimation methods to predict the coefficients of infiltration equation including two-point method, multilevel optimization, SIPAR-ID, and IPARM in the vegetated furrows were assessed and compared together using the field data. The field study in order to collect required data was conducted in Karaj in 2014. Seven irrigation events were performed during the growing season of the maize with two inflow discharges of 0.29 and 0.44 l/s. Based on the estimated coefficients of infiltration equation, the IPARM model with average relative errors of 1.24 and 1.52 %; as well as the multilevel optimization method with average relative errors of 1.44 and 1.58 % had the best performance for inflow discharges of 0.29 and 0.44 l/s in estimating infiltrated water volume, respectively. The SIPAR-ID model had a poor and fluctuating performance in estimating the coefficients of infiltration equation in the vegetated furrows. Moreover, the two-point method presented an acceptable performance with average relative error less than 10 percent in estimating infiltrated water volume.