Numerical groundwater flow modeling for managing the Gabes Jeffara aquifer system (Tunisia) in relation with oasis ecosystems

• Published in: Hydrogeology journal 2020-05, Vol.28 (3), p.1077-1090
• Main Authors: Vernoux, J. F., Jarraya Horriche, F., Ghoudi, R.
• Format: Article
• Language: English
• Subjects: Aquatic Pollution; Aquifer models; Aquifer systems; Aquifers; Depletion; Earth and Environmental Science; Earth Sciences; Ecosystems; Exploitation; Flow rates; Flow velocity; Geology; Geophysics/Geodesy; Groundwater; Groundwater depletion; Groundwater flow; Groundwater irrigation; Groundwater levels; Groundwater management; Groundwater recharge; Groundwater withdrawal; Hydrodynamics; Hydrogeology; Hydrology; Hydrology/Water Resources; Inflow; Multidisciplinary research; Oases; Piezometers; Rain; Rainfall; Rainfall infiltration; Satellite imagery; Sciences of the Universe; Spaceborne remote sensing; Surveys; Waste Water Technology; Water consumption; Water demand; Water inflow; Water Management; Water Pollution Control; Water Quality/Water Pollution; Water resources; Water resources management; Water springs
• ISSN: 1431-2174; 1435-0157
• DOI: 10.1007/s10040-020-02123-z

The Gabes Jeffara aquifer system, in southeastern Tunisia, is essentially recharged by rainfall infiltration and by groundwater inflow from the Intercalary Continental aquifer in the northwest. The increase in groundwater pumping for irrigation in recent decades has induced a serious decrease in groundwater levels, depletion of springs and degradation of oasis ecosystems. A multidisciplinary study was carried out to better understand the behavior of oasis ecosystems and aquifer systems and to provide tools and recommendations for water resources management. An important part of the study was devoted to developing a hydrodynamic flow model of the Jeffara aquifer system, which can be used as a future groundwater management tool considering different recharge or exploitation scenarios. This model was built with Processing Modflow, gathering data on geology, hydrogeology, hydrology, rainfall, piezometry, withdrawals and spring flow rates. The model was calibrated in steady state with reference to the piezometric levels measured in 1970 and in transient state for the period 1972–2014, using records from more than 200 wells and piezometers. The analysis of current and future water consumption was carried out with existing data, processed satellite images and farmer surveys. This analysis was used to define water demand scenarios combined with scenarios of decreased groundwater withdrawal, reinforced groundwater recharge and use of alternative water resources. The scenarios tested with the model show that the situation will be critical in less than 25 years without radical measures to reduce groundwater withdrawals by at least 60 MCM/year.