UNIFORMITY OF WATER DISTRIBUTION BY CENTRAL PIVOTS

Abstract

Among the existing irrigation systems, central pivots occupy extensive areas and consumes large amount of water. Thus, there is a constant search for more efficient use of such equipment requiring improvement of existing evaluation methods. This study proposes a new method to evaluate the uniformity of water distribution by central pivots. Areas of 40, 60, 80, 100 and 120 ha irrigated with central pivots, totaling 50 systems were evaluated. The treatments were: pluviometers with the Christiansen Uniformity Coefficient (CUC) calculated according to Christiansen (1942) as modified by Heermann and Hein (1968) (Method 1), rain gauges installed to represent a sampling area of 0.5 ha with CUC calculated according to Christiansen (1942) (Method 2), the methods 3, 4, 5, 6 and 7, were same as Method 2, but with collectors installed to represent sample area of 1 , 2, 3, 4 or 5 ha, respectively. The area being adequately irrigated (ABAI) was calculated to obtain regression coefficient. The uniformity determined by method 2, most closely correlated with the concept of ABAI, followed by the methods 1 and 3. The pivots in 40, 60, 80, 100 and 120 ha size are recommended for testing uniformity with collectors representing sampling areas up to 1.0, 1.1, 1.3, 1.4 and 1.6 ha, respectively.