Abstract: Infiltration trenches can help to accelerate infiltration of water into the deep vadose zone and groundwater table. A two dimensional model was developed to characterize the performance of arbitrarily shaped infiltration trenches. This model employs a mixed form of Richards’ equation, which was solved using the coordinate transformation technique, and the reservoir equation to describe the effects of water ponding and evaporation through the soil–air interface. The model was validated using numerical and experimental test cases in the literature, and in all cases, acceptable results were obtained. Subsequently, the shape of an infiltration trench was optimized with respect to the amount of inflow water using the Taguchi technique. Running 25 combinations which were representative of 125 different trench shapes and volume of inflow water showed that a rectangular trench with a capacity of about 36% of the volume of inflow water is the best cross section of a trench. The predicted normalized recharge obtained by the Taguchi method and that of numerical modeling showed perfect agreement (about 0.01% error) for the combination that resulted in the most normalized recharge value.

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