Oral Presentation Australasian Groundwater Conference 2017

Accurate groundwater flow modelling closely linked to constrained 3D geology: a case study from Tunisia (#211)

Imen Hassen 1 , Helen J Gibson 2 , Fadoua Hamzaoui-Azaza 3 , François Negro 4 , Khanfir Rachid 5 , Rachida Bouhlila 1
  1. Laboratory of Modeling in Hydraulics and Environment (LMHE), National Engineering School of Tunis, University of Tunis, El Manar, Belvedere, Tunisia
  2. Intrepid Geophysics, BRIGHTON, VIC, Australia
  3. Research Unit of Geochemistry and Environmental Geology, Research Unit of Geochemistry and Environmental Geology: Faculty of Mathematical, Physical and Natural Sciences, University of Tunisia, El Manar, Tunis, Tunisia
  4. CHYN (Centre of Hydrogeology and Geothermics), Neuchâtel University, Neuchâtel, Switzerland
  5. General Directorate of Water Resources, Tunis, Tunisia

In north African nations such as Tunisia, geological exploration under cover remains the most difficult challenge to success in finding continuing water resources, geothermal energy, oil and gas, and minerals. Securing these resources means long term commercial self-sufficiency. Achieving such goals requires understanding the 3D geometries of subsurface geology and structures.

Creation of a realistic 3D geological and structural model of the Kasserine Aquifer System (KAS) in central Tunisia and north-east Algeria, was the main workflow of this project. This was achieved using an implicit 3D method, which honours prior geological data for both formation boundaries and faults. The model built in GeoModeller software provides defendable predictions for the spatial distribution of geology and water resources in aquifers throughout the regional-scale model-domain.

Aquifer connectivity and the hydraulic significance of the major faults was assessed using the 3D model. This was carried out by evaluating the influence of faults on known groundwater flow directions, and the locations of springs, within and between four compartments of the multilayered, KAS hydrogeological system. Possible dual nature of faults in the KAS was identified because some faults appear to be acting both as barriers to horizontal groundwater flow, and simultaneously as conduits for vertical flow. Also explored, was the possibility that two flow directions occur within the KAS, in the region of a small syncline near Feriana.

Beginning as a conceptual study on regional scale, the model was next used to estimate volumetric groundwater resources, and then to perform numerical flow modelling on a finite element mesh coupled with geological information derived from the model, using FEFLOW software. This integrated 3D approach, linked to a model of realistic geology and faults has world-wide applicability for critical understanding of groundwater systems as resources.

 

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