Coupling Hydrus-1D code with geoelectrical measurements to investigate the infiltration process in the soil passage in the western part of Damascus, Syria

The daily climate data of two climate stations in the western part of Damascus were used to calculate the local potential evapotranspiration. The calculated evapotranspiration together with the precipitation and the saturated hydraulic conductivity of the soil was processed in Hydrus-1D to simulate the infiltration process through the soil passage. The simulation shows that the bottom flux has a maximum value of 2E − 2 cm/day, while the soil water storage has a value of 30 cm. Furthermore, four geoelectrical profiles were measured in 2011 to estimate the water content in the soil profile and to investigate the subsurface. The measurements revealed the existence of two distinguishable layers: the overlying agricultural soil of up to 3–4 m and an underlying clay horizon of up to more than 25 m thickness. A comparison with lithological profiles from boreholes confirms the results of the geoelectrical measurements. The water content of the first layer was estimated, and the results show a saturation degree of 40%, which represents retained water mainly originating from irrigation. The existence of the clay layer is proof for confining conditions in the aquifer in this part of the area and that recharge does not take place through infiltration from surface.