Présentations Colloques

Session 6.01: Managed Aquifer Recharge
Msaddek (orateur)
Uses of multiscale fracturation study approach to estimate artifcial groundwater recharge in arid regions (exemple of Segui region, South of Tunisia)
In Tunisia, arid regions are characterized by scare water resources, and phreatic aquifers have especially a bad water quality with a very high salinity, due to the abundance of large salt flats like chotts and sebkhat. These salt flats have an important role in the contamination of phreatic aquifer by salinization process. To avoid the problem of water resource availability in porous phreatic aquifer, carbonate rocks aquifer in fractured media are productive and abundant in these regions. **As an illustrative example of the water quality in arid region, Segui aquifer system, situated in the southeast part of Gafsa city, in the south of Tunisia, suffer from the contamination of the water in the phreatic aquifer. The salinity exceeds 11g l in the most of wells and water points. This region is also characterized by tectonic complexity. It is located near the Gafsa accident, which is a segment of the regional tectonic accident of the South Altas in Tunisia.**The multiscalar analysis of the fracture in the outcrops is based on two approach- (1) the study of regional tectonics and main faults at the scale of satellite imagery of LandSat L8 OLI TIRS, and (2) the measurement of metric fractures with the outcrop scale in carbonate formation of upper Cretaceous. The results shows that the groundwater flow system is controlled by fracture network. The major faults network with a N100-N130 direction have an important role in blocking groundwater flow process. It have the role of geological threshold at surface, and hydrogeological threshold at subsurface. The qualitative analysis of the fracture network shows that they promote water circulation and the quantitative analysis shows that the importance of the special distribution of fractures promotes the formation of a fractured carbonate aquifer.**The combination of all these results with topographic data extracted from SRTM (digital elevation model), geological and hydrological data, gives a very hopeful tool for the artificial groundwater recharge in fractured carbonate aquifer.**