Explicit relationships for optimal designing rectangular microirrigation units on uniform slopes: The IRRILAB software application

Many attempts have been made to provide easy tools for designing microirrigation units. However, most of these have dealt with numerical solutions, which require many trial-and-error attempts and time-consuming iterations, performed by applying the basic hydraulic equations from the manifold to the end of both the downhill and the uphill sides of the laterals. Recently, analytical procedures to optimally design paired drip laterals on uniform slopes were proposed, providing readily obtainable results and energy saving. Although these analytical solutions can be practically applied, they only make it possible to design a one-lateral unit; to be really interesting for practical application, a design tool must address the design of the entire irrigation unit. In this paper, the one-lateral unit relationships previously obtained were applied to analytically derive explicit design relationships for the optimal design of rectangular microirrigation units (corresponding to 25 layouts), with branching pipe networks with many laterals and one manifold, laid on uniform slopes. It is shown that these explicit relationships allows calculating the design variables, i.e. the emitter's hydraulic characteristics, the required inlet flow rate, the inlet pressure head, the manifold inside diameter, the number of rows, the irrigation unit area, and the water application rate, as well as other important variables such as the Reynolds number for the laterals and the manifold. A software simple to use, named IRRILAB, following the described procedure, is presented and applications were successfully carried out.