Basin structure and water quality of the Oligocene aquifer in the Sebkhet El Behira basin (central Tunisia)

ABSTRACT

The Sebkhet El Behira–Garaat El Majdoul multilayer aquifer system is composed of Mio-Plio-Quaternary and Oligocene groundwater exploited in Sidi Bouzid and Kairouan governorates. Annual withdrawal volumes from El Behira Oligocene groundwater were about 0.37 hm³ in 2005 and 0.36 hm³ in 2008. The present study of the Oligocene reservoir in the Sebkhet El Behira–Garaat El Majdoul basin is based on various data including 2D seismic sections, petroleum wells, field geological cross-sections and geochemical analysis. The gathered data allowed us to establish the tectonic framework and to define its influence on the structure of the aquifers seated in the deep Oligocene sandstone reservoirs. Three Oligocene sub-basin aquifers are defined showing different depth, thickness and petrophysical characteristics: lower salinity (<1.5 g/L) and higher porosity (30%). Two field sections in the northern and in the southern parts of Cherahil anticline exhibit the presence of four to five sandstone levels. The anticlines limit the Sebkhet El Behira–Garaat El Majdoul basin. In addition, the morphostructural configuration controls the piezometry of underground flows in the Oligocene and Mio-Plio-Quaternary unconfined aquifers.

Editor D. Koutsoyiannis; Associate editor M. Besbes

KEYWORDS:

• hydrogeology
• Sebkhet El Behira aquifer
• Oligocene aquifer
• water quality
• central Tunisia
• basin structure

Acknowledgements

We would like to express our gratitude and thanks to the technicians and engineering staff of Kairouan and Sidi Bouzid water resources regional departments, and also to the researchers and staff members of the georesources and waste water treatment laboratories, for their help and assistance during the field survey and laboratory analysis. Thanks also to the reviewers and co-editor of HSJ for their criticism and fruitful suggestions that highly improved this manuscript. We are grateful to Dr Amina Mabrouk of the Department of Geology, Faculty of Sciences, El Manar Tunis University for her great effort to revise the English text and figure legends of this manuscript.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This work is part of the results of the research project (2002–2014) “Deep Aquifers in Eastern Tunisia Sahel Regions” of the Georesource Laboratory, Centre of Water Research and Technology, Borj Cédia Technopark (Tunisia) in collaboration with the Direction Générale des Ressources en Eaux of the Agriculture Ministry and financed by the Ministry of Higher Education and Scientific Research of Tunisia.