Groundwater is the main source of all renewable water resources for drinking and irrigation water in most arid and semi-arid areas. However, groundwater abstraction by pumping has increased in most areas significantly, leading to a lowering of the groundwater level. Managed aquifer recharge is a measure to prevent or counteract these temporary and permanent groundwater declines and their negative effects. The work described here deals with the numerical simulation of treated wastewater infiltration for improving the local groundwater balance in the catchment area of Sarden village, Syria. The semi-arid region is characterized by shallow silty clay soils, limestone cliffs and karst aquifers. Different model setups were built up by means of the software PCSiWaPro simulating the effects of different boundary conditions on the saturation conditions in the vadose zone. This should enable an initial assessment of whether and under what conditions the installation of an infiltration system is possible. Results of the research are showing that the hydraulic conditions in the unsaturated soil zone at the site are influenced most by the groundwater level and the number of trenches used for infiltration, whereas precipitation events are playing a subordinate role. In case of elevated groundwater level and too low number of infiltration trenches, the water can rise up to or in the infiltration trenches.