Use of Ultrasonic Waves for the Evaluation of the Unsaturated Zone Hydrodynamic Parameters: An Example from Merguellil Basin Downstream of El Haouareb Dam (Central Tunisia)

Groundwater recharge estimation, which is usually required for good water resources management, is usually based on predicting the unsaturated zone hydrodynamic properties. This study uses the ultrasonic method to assess the soil hydrodynamic properties of the unsaturated zone in Merguellil Basin downstream of El Houareb Dam (central Tunisia). This method is considered a fast indirect tool to determine soil physical parameters and spatial variability. These data are required to estimate infiltration rates in the unsaturated zone and its evolution over time and space. Several measurement points were chosen on the subsurface downstream of El Houareb Dam. Models were produced using artificial neural networks, correlating the selected physical parameters (ultrasonic velocity, density, and lithology) with the soil hydrodynamic properties (effective porosity and water content (Wc)). For this purpose, 16 soil samples were taken from 4 stations of the basin downstream. The obtained results illustrated the behavior of the ultrasonic waves controlling soil physical properties of the subsurface, which shall be subsequently valorized in simulating infiltration and groundwater recharge.