MODELING OF EVAPORATION REDUCTION IN DRIP IRRIGATION SYSTEM

Surface drip irrigation is an efficient system for delivering water to crops; however, conditions at the soil surface affect evaporation rate and efficiency. A method is proposed, sand tube irrigation (ST I), to increase the efficiency of drip irrigation systems. This method is specific to permanent tree crops where soil is not tilled or turned. The STI method consists of removing a soil core beneath the emitter and filling the void with coarse sand. The SWMS-2D model, implemented in a 3D axisymmetric form, was used to simulate infiltration, water redistribution, evaporation from the soil surface, and rise of water inside the sand tube. Model simulations were compared with laboratory measurements determined from a weighing lysimeter. The simulated values of water height inside the sand tube and temporal position of the wetting front in both lateral and upward directions closely matched the experimental measurements. The advancement of the wetting front in the downward direction and evaporation estimates was predicted with less accuracy. Experiments showed that relative to surface drip irrigation, the ST I method reduced evaporation by approximately 26% over a 4-day period.