Coupling WetSpass and MODFLOW for groundwater recharge assessment: case study of the Takelsa multilayer aquifer, northeastern Tunisia

Abstract

The water scarcity and its socio-economic significance with respect to water demand for agriculture, industry and tourism, in the northeastern Tunisia (Cap-Bon), are at the origin for prospecting new groundwater resources and for developing groundwater models that can be used to their control and management. The Takelsa multilayer aquifer is one of the important aquifers of the northeast in Tunisia. It is among the aquifers which are still slightly known in spite of its exploitation since the 80s. This paper is aimed to quantify the groundwater recharge of the Takelsa multilayer aquifer. The groundwater recharge is assessed using WetSpass which is a physically based model integrated in GIS ArcView as a raster model. The simulated results are given seasonally and yearly at the grid level. These results are subsequently incorporated in the groundwater flow simulation model MODFLOW in order to simulate the hydraulic head distribution. The steady state groundwater flow calibration was obtained by comparing the observed and the simulated hydraulic heads. The mean annual evapotranspiration, surface runoff and groundwater recharge simulated by WetSpass, are 461, 92 and 22 mm, respectively. The groundwater recharge represented 4.3% of the precipitation while 17.8% and 89% are respectively lost by surface runoff and evapotranspiration.