numerical versus empirical models for estimating wetting patterns in subsurface drip irrigation systems

optimal use of water resources is essential to decrease cost and maximize available water resources. subsurface drip irrigation can increase irrigation and water use efficiency. this irrigation method distributes water into the soil, leaving the surface of the soil dry and decreasing evaporation. in the design of subsurface drip irrigation (sdi) systems, the dimensions of the wetted onion determine the installation depth and spacing of the drippers. several models have been developed to simulate soil moisture patterns and the wetting front using soil hydraulic parameters, emitter discharge rate and volume of water discharged. the present study used the powerful numerical model hydrus-2d and dimensional analysis, which requires fewer parameters to predict the wetted zone using the empirical method. the predicted values for wetting depth (upward, downward) and horizontal dimensions were compared with those obtained by laboratory testing conducted in loamy soil at 40 cm in depth. r2 varied from 0.88 to 0.97 for hydrus-2d and 0.94 to 0.98 for the empirical model. the results showed that the simulated and experimental results were in very good agreement and that the empirical model better predicted the dimensions of the wetted onion.