Integrated hydrogeological study of a tectonically controlled aquifer system: The Rohia–Sbiba graben, Central Tunisia

The Rohia–Sbiba graben in Central Tunisia exhibits interesting hydrogeological characteristics with complex aquifer systems encompassing several Cretaceous to Quaternary hydrogeological units. To define the geometrical development of the aquifer units and to give new insights on recharge, mineralization and hydrodynamic processes, an integrated hydrogeological study was conducted. Gravity, electrical data and groundwater physicochemical parameters together with statistical analysis provided detailed information on the aquifer’s geometry and their hydrodynamics and mineralization processes. The tectonic control of the graben sedimentary fill gave thick permeable deposits ensuring high storage capacity. These deposits exhibit complex geometry and record variable conditions of stream-flow, deposition and erosion related to the migration of surface drainage channels. The recharge of this aquifer system is ensured by direct infiltration of meteoric water from surface flows and artificial recharge structures. The groundwater samples exhibit sulfated and calci-magnesian chloride facies. The chemical elements result mainly from the dissolution of evaporitic rocks and tend to accumulate within the detrital aquifer downstream; the shallow carbonated aquifers are disposed to transfer groundwater laterally to the subsided detrital units. The combination of geophysical, hydrochemical and statistical approaches in studying the hydrogeology of these tectonically controlled aquifers provided a comprehensive understanding for developing long-term management of groundwater. Research highlights Geophysical data and groundwater physicochemical parameters together with statistical analysis were used to decipher the aquifer’s geometry, hydrodynamic and mineralization processes. The tectonic control of the aquifer system is highlighted and discussed. The BMLP and major oxides (CaO and MgO wt%) along the growth laminae may be associated with CaCO 3 deposition, reflecting surface precipitation and disequilibrium conditions. Preserved biogenic remains associated with primary features may depict biogenic activity.