Dual-Diameter Laterals in Center-Pivot Irrigation System

Design strategies to enhance modern irrigation practices, reduce energy consumption, and improve water use efficiency and crop yields are fundamental for sustainability. Concerning Center-Pivot Irrigation Systems, different design procedures aimed at optimizing water use efficiency have been proposed. Recently, following a gradually decreasing sprinkler spacing along the pivot lateral with constant diameter and sprinkler flow rate, a new design method providing a uniform water application rate has been introduced. However, no suggestions were given to design multiple-diameter laterals characterized by different values of the inside pipe diameter. In this paper, first the previous design procedure is briefly summarized. Then, for the dual-diameter center pivot laterals a design procedure is presented, which makes it possible to determine pipe diameters that always provide sprinkler pressure heads within an admitted range. The results showed that for the assigned input parameters, many suitable solutions can be selected. The lateral pressure head distributions were compared to those derived by the common numerical step by step solutions, validating the suggested simplified procedure. An error analysis was performed, showing that the relative error, in pressure heads, RE, was less than 2.3%. If imposing the mean weight diameter, Dm, equal to its minimum value, the optimal pressure head tolerance of the outer lateral, δI, amounting to about 2%, with the RE in pressure heads being less than 0.4%, which makes the suggested procedure very accurate. Several applications were performed, compared, and discussed.