Effect of Optimum Arrangement and Spacing of Sprinklers on Uniformity Coefficient of Fixed Sprinkler Irrigation System

Reduction of water losses due to increase in the applicationuniformity in sprinkler irrigation systems needs appropriate selection of the sprinklers spacing and arrangement. In the present study, to evaluate the impact of spacing and arrangement of sprinklers on uniformity coefficient (UC) of the irrigation system and to investigatethequalitative and quantitative changes of UC due to changes in the parameters of the area covered by the sprinkler and wind speed, the test of distribution pattern of a single sprinkler was performed. The test was conducted according to ISO 8026, ASAE S398.1and ISO 7749, 2 standards on three VYR 35, IRILINE 30, and RAINBIRD 40B sprinklers. In this study, the square shaped arrangement had the highest UC and lowest sensitivity to decreasing coefficient of uniformity with an average of 5.3% and 5.5 percent for the average increasing of 59.4% and 98.3 percent in the covered area and wind speed, respectively. The least sensitivity of the UC were obtained for the IRILINE sprinkler with the mean reduction values of 3.4% and 5.48 percent for the average increasing of 37% and 117.8 percent in the covered area and wind speed, respectively. Results showed that to achieve the desired coefficient of uniformity, the maximum sprinkler spacing should be considered as 40 percent of the nominal application diameter of the sprinkler with a square arrangement when wind speed exceeds 4 meters per second.