Differential Evolution (DE) Algorithm to Estimate the Uniformity of Water Distribution Coefficient in ZB Sprinkler Irrigation System

Limited water resources, especially in Iran, require most effective method of water use to avoid losses. One of the important parameters in irrigation is water distribution uniformity coefficient (CU) in sprinkler irrigation. CU in every irrigation depends on pressure heads (P), riser height (RH), distance between sprinklers on lateral pipes (Sl), and the distance between lateral pipes (Sm). The best combination of the above parameters for maximum CU is still unknown for users. In this research, CU values of zb model sprinkler (made in Iran) were measured at Hashemabad Cotton Research Station of Gorgan under 3 different pressure heads (2.5, 3, and 3.5 atm), 2 riser elevation (60 and 100 cm) and 7 sprinkler arrangements (S_l×S_m including 9×12, 9×15, 12×12, 15×12, 12×18, 15×15, 15×18m). By using differential evolution algorithm (DE), CU equation was optimized and the best optimized coefficient was obtained. In this algorithm, the coefficients F and CR were equal to 2 and 0.5, respectively, with a population of 100 members and 1000 number of generations (iterations), providing the best results. Absolute error between the results of this algorithm with the measured results was 2.2%. Also, ​​Wilmot (d) and the root-mean square error (RMSE) values were equal to 0.919 and 2.126, respectively. The results showed that this algorithm had high accuracy to estimate water distribution uniformity coefficient.