Studying and Evaluating of Developed Methods for Estimation of Infiltration Parameters in Conventional and Fixed Alternate Furrow Irrigation

Parameters of infiltration equation have fundamental role in evaluation and design of irrigation systems. In fact, it’s essential that these parameters be carefully estimated in order to increase irrigation efficiency. In this research the Elliott and Walker two-point method, Ebrahimian et al. two-point method, Shepard et al. one-point method, Multilevel optimization method and Benami and Ofen advance method were compared with measured data. The accuracy of each one of them in estimation of advance phase in conventional and fixed alternate furrow irrigation was evaluated in a clay soil. For this purpose, furrows with a length of 70 m, width of 0.75 m, and approximate slope of 0.0075 m/m were prepared. These furrows had 0.9 L/s inflow rate in the first irrigation and 1.1 L/s inflow rate in the second and third irrigations. Infiltration in the furrows was measured in the field using the input-output method. According to the estimation infiltration parameters in estimating of the amount infiltrated, The results showed that the Multilevel optimization method and Elliott and Walker two-point method have the least relative error in conventional furrow irrigation (14.9-17.87%) and in fixed alternate furrow irrigation (12.1- 25.92%), respectively. And the Shepard one-point method have the maximum relative error in estimating of the amount infiltrated in conventional furrow irrigation (40.53%) and in fixed alternate furrow irrigation (33.37%). The Multilevel optimization method provided the least (RMSE) in the estimation of the total volume of infiltrated in the conventional and fixed alternate furrow irrigation. In the prediction of advance phase, the Shepard one-point method and Elliott and Walker two-point method had have the lowest standard error (18.71 and 28.91%) for conventional furrow irrigation and (17.51 and 34.4%) for fixed alternate furrow irrigation, respectively. Comparing the results of the Multilevel optimization method and Elliott and Walker twopoint method showed that the percentage difference between this two methods for estimating the volume of infiltration in conventional furrow irrigation is low and just about three percents (3%). Therefore, it can be a Multilevel optimization method for accurately estimating the volume of infiltration in furrow the soil conditions are similar.