A synthetic approach integrating surface and subsurface data for prospecting deep aquifers: the Southeast Tunisia

Abstract

The Southeast Tunisia has remarkable thermal springs that have been used for bathing since many years. Currently, studies are being carried out to investigate the possible use of the hot water for heating buildings and for greenhouses. Springs with discharge temperatures between 26.8 and 58°C exist in the area. The flow rates range between 7 and 66 l/s with total dissolved solids (TDS) varying between 2,020 and 4,030 mg/l. Both geological–hydrogeological setting and the similarity in chemical characteristics between the Zarat spring and nearby water wells suggest that the hot water from this spring may be related to the Senonian aquifer. However, the hydrogeothermal approach shows that the depth of the reservoir that supplies the Zarat spring is greater than that of the Senonian aquifer. In fact, geothermometry approach indicates that fluids emerging from the Lower Cretaceous sandstones reach temperatures of approximately 78°C at depth, while the fluid temperature from the nearby water wells is 32°C. Through the integration of various types of data we found that the thermal water of Southeast Tunisia is of meteoric origin. This water infiltrates deeply into the Lower Cretaceous sandstones and reaches a high temperature before rising upwards to supply the hot springs and well discharge zones. It appears that the upward movement of hot water from the deep aquifers to shallow ones is probably due to the abundant fractures in the area.