Effect of hydraulic head and slope on water distribution uniformity of the IDE drip irrigation system

Assessment of the effect of topography and operating heads on the emission uniformity distribution in drip irrigation systems is important in water management and could serve as the basis for optimizing water-use efficiency and crop productivity. This study was carried out to evaluate the effect of slope and hydraulic head on the water distribution uniformity of a low-cost drip irrigation system developed by International Development Enterprises (IDE). The drip system was tested for water distribution uniformity under varying system heads and slope conditions. The experiments were conducted at the hydraulic laboratory facilities of the College of Engineering and Agro-industrial Technology, University of the Philippines-Los Baños. A drum reservoir served as water supply for the IDE drip system. A sub-main of 10 m and lateral-sub holder of 20 m with adjustable slope was fabricated to enable slope variations during laboratory experiments. The drip system was operated at pre-specified operating heads of 1 m, 2 m, and 3 m from the reservoir outlet for slopes of 0 percent, 10 percent, 20 percent, 30 percent, 40 percent, and 50 percent for the sub-main; and 0 percent slope for the laterals. The discharges in selected emitters were monitored under each chosen slope through direct volumetric measurements. The uniformity coefficient was then estimated using Christiansen's method. Mathematical relationships were then developed to characterize the effect of slope and heads on uniformity coefficient. On the basis of the results, appropriate recommendations were formulated to minimize non-uniformity of water distribution under field conditions in sloping drip-irrigated lands.