Effect of Wind Speed and Hydraulic Characteristics on Water Distribution Uniformity under Sprinkler Irrigation Systems

In this study, the water distribution uniformity of different sprinkler used in solid set systems were determined at different operating pressures, sprinkler spacing and under varying wind speed conditions The experiment was conducted in the Agricultural Experimental Station of Seed and Plant Improvement Institute (SPII) in Karaj, near the meteorological station during 2008-2009. The experimental design was randomized complete blocks design (RCBD) in factorial layout with different replications. The experimental treatments were combinations of 8 sprinklers (Farm-RC180, Jaleh 5, Komet 162, Luxor, VYR 155, Nelson24F80 with one nozzle, Rain Bird 80EHD and Nelson F80,18with two nozzle), 3 operation pressures (3, 4 and 5 Kg/cm2), 4 wind speed range (0-5, >5-10, >10-15, >15-20 Km/hr) and 7 sprinkler spacing (22.5*22.5, 22. *25, 22.5*27.5, 25*20, 25*25, 25*27.5 and 25*30 meter). The outdoor single sprinkler test method was used to determine the water distribution pattern distorted by wind action uniformity. In order to determine the water distribution uniformity under varying wind speed conditions, a set of catch-cans was set around the individual sprinkler in 2.5*2.5 arrays. The volume of water in the catch-cans was measured after 1 hour operation for each treatment. The overlapping of sprinklers was simulated and water distribution uniformity for seven sprinkler layout was calculated and the Christiansen’s coefficient of uniformity (CU) and distribution uniformity (DU) values for each treatments were determined Results showed that the sprinkler type, sprinkler spacing, operating pressures and wind speed treatments had significant effect on water distribution uniformity (P 0.01). Sprinklers type were classified in five group from A to E. Sprinklers type of Komet 162 and Nelson F80 with two nozzle had high water distribution uniformity and classified in group A. Nelson F80 with one nozzle and VYR 155 types classified in second group. Based on the results, with increasing the operation pressures, water distribution uniformity was increased non-linearly. Also, water distribution uniformity was decreased when wind speed increased more than 5 Km/hr. According to the results, the sprinkler type that classified in group A and B with the operation pressures of 4 to 5 kg/cm2 and 20*25 meters spacing was recommended for overall agricultural conditions.