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Abstract
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This study used the location of the average advance time (method 1) and the mean infiltration opportunity time (method 2) as the midpoint of the two-point method for determining ‘power advance’ and Kostiakov-Lewis infiltration parameters. Experiments were carried out in three border-irrigated fields, Vahedi, Orooj, and Vadood from Zarrineh Rood irrigation and drainage network in western Iran. In the Vahedi field, three pilot borders were selected. In the Orooj and Vadood fields, a pilot border was selected. In the fields of Vahedi and Vadood, two irrigations were assessed at each border. In the Orooj field, at each border, three irrigations were evaluated. The results showed that calibration of the power advance equation obtained by Elliot and Walker method had high accuracy, with an average relative error of 11.3% in the time to complete the advance phase. The relative errors of the first and second methods were 12.8% and 19%, respectively. the root mean square deviation (dRMS) index used by Elliot and Walker showed that the proposed method 1, with an average dRMS value of 15.7 minutes, has the lowest dRMS, which estimates the advance times with mean dRMS values of 5.1 and 1.8 min compared to the proposed method 2 and the method of Elliot and Walker, respectively. Furthermore, using the proposed methods and the two-point method, the Kostiakov-Lewis infiltration equation parameters for each irrigation were determined. Based on the relative error index, the infiltration depth values of these equations were compared with the average infiltration depth of the field. The minimum, maximum, and average relative errors of Elliot and Walker infiltration equation were 1.2, 25.4, and 6.5%, respectively. Method 1 had the highest accuracy with a minimum relative error of 0%, a maximum relative error of 8.7%, and an average relative error of 3.8%. The minimum, maximum and average relative errors of proposed method 2 were 0.3, 21.6 and 6.7%, respectively. Based on both the dRMS index and the accuracy of the infiltration equation, method 1 had a higher accuracy than the Elliot and Walker method. Therefore, it is suggested to use the location of the average advance time as the midpoint of the two-point method.
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