Harvesting water in a center pivot irrigation system: evaluation of distribution uniformity with varying operating parameters

The main objective of irrigation is to apply the optimum amount of water to the crop root zone that is needed for its growth. Also, when irrigation systems are used to apply fertilizers and pesticides, the irrigation process becomes even more critical in terms of uniformity. Consequently, it is important for center pivot owners and operators to periodically check the uniformity of their systems in order to adjust all the operating parameters involved. To assess the real distribution uniformity of irrigated water, a study was conducted in southern Libya; this paper reports the results of water irrigation in a center pivot system with respect to the effects that the operating pressure (P), the spacing between sprinklers (S), and the height of sprinkler above the ground surface (H) show on the distribution uniformity. Several factors define the uniformity of water distribution; in this work the coefficient of uniformity CU, the low quarter distribution uniformity DUlq , and the coefficient of variation CV are considered. The highest values reached by the uniformity parameters with varying the operating conditions define the best operating practices under which the whole system works efficiently. The final results are given in terms of operating conditions able to save total costs in the studied area and in places characterized by similar geo-hydrological conditions.