Developing Equations to Estimate Wetted Area Pattern for Surface and Subsurface Drip Irrigation Systems by Dimensional Analysis

One of the most important parameters in designing surface and subsurface drip irrigation systems is considering up and down soil wetting area of emitters. In this study, by means of Buckingham π theorem and using dimensional analysis, some equations were developed in order to estimate up and down soil wetted area of emitters. The experiments were carried out in a transparent plexiglass tank (0.5m.1.22m.3m) using three different soil textures (fine, heavy and medium). The drippers were installed at 4 different soil depths (surface, 15, 30 and 45cm). The emitter outflows were considered 2.4, 4 and 6 Lhr-1 with irrigation duration of 6hr. Then, using the-p theorem of Buckingham and dimensional analysis, equations were developed to estimate the up and down soil wetting area of emitters. The results of the comparisons between the simulated and measured values (evaluated correlation coefficient more than 90%) showed that these equations were very capable of predicting the soil wetting area. The average values of Root Mean Square Error (RMSE) for down wetted area (all depths) for the clay, loam and sandy soil textures were estimated as 0.015, 0.019 and 0.033, respectively which showed the relative superiority of the developed equations in the clay soil texture. Also, the average RMSE values for up wetted area in the same soil textures (0.02, 0.034 and 0.053, respectively) confirmed the equations accuracy. Considering these equations in designing surface and subsurface drip irrigation systems can improve these systems performance.