A multidisciplinary study for a better management of water resources in an agricultural region: case study of the Saouef-Jebibina region (North-East Tunisia)

A case study of the use of complementary approaches to enhance the management of groundwater used for irrigation in an arid zone is presented. This study concerned the Saouef-Jebibina agricultural region in northeastern Tunisia, a water-stressed country. It included and analyzed geological, hydrogeological, geophysical, and hydrochemical data to provide detailed knowledge of the Oligo-Miocene aquifer and thus support the managed extraction of its water resources for agriculture. The main characteristics of the aquifer-its geometry, hydrodynamics, and water quality-were defined in detail, given that an understanding of them is crucial to enhancing the management of the aquifer. Its geometry was reconstructed by analyzing and correlating the lithological logs and the corresponding well logs. Gamma-ray logs allowed the precise delimitation of coarse formations within the Oligo-Miocene series and consequently facilitated the elaboration of two- and three-dimensional representations of the arrangement of the reservoirs. Those revealed that in the southwestern part of the study area, coarse deposits are abundant and separated by thin clayey layers. The aquifer hydrodynamics were studied using piezometry and transmissivity data. The transmissivity map presented similar values on the order of 3 x 10(-3) m(2)/s, while the piezometric map showed that the highest water levels were in the western part of the aquifer. To examine the water quality, the electrical conductivity (EC) and sodium adsorption ratio (SAR) were evaluated to assess the salinity and sodicity, respectively. The EC values varied between 1100 and 2700 mu s/cm, indicating that the Saouef-Jebibina aquifer must be used with caution for irrigation. The SAR values, which were less than 10, reflect a low risk of alkalization. Analysis and cross-comparison of the resulting documents relating to the geometry, hydrodynamics, and water quality of the Saouef-Jebibina aquifer allowed accurate differentiation between favorable and unfavorable zones for the use of groundwater resources for agriculture. Hence, this study should contribute to the socioeconomic development of Tunisia and serve as a reference for other arid regions with economies essentially based on agricultural activity.