The environmental impact assessment of intensive groundwater abstraction on the groundwater flow and salinity of the Nadhour Saouaf Sisseb El Alem Aquifer System (Central Tunisia)

The Nadhour Saouaf Sisseb El Alem (NSSA) multilayer aquifer system is one of the most intensively used water sources in central Tunisia. Since the 1970fs, the growth in economic productivity linked to intensive agriculture in this semiarid region has been sustained by increasing groundwater abstraction. The use of this aquifer system has augmented rapidly, ultimately causing depletion and salinization; to better understand its behavior and, to predict the groundwater flow and chemical evolution, the finite difference Groundwater Modeling System (GMS) software was applied. Groundwater levels observed in 1970 were used for steady-state calibration; levels from 1971 to 2015 served to calibrate the transient state. The impact of abstraction on the evolution of groundwater flow and salinity was studied through three hypothetical scenarios. The increase in abstraction rate of 30% and 50% in the first and second scenarios examine the tolerable extraction threshold. The results of increase in abstraction show a drawdown in the hydraulic head elevation of .17 m and .23 m; salinity was increased in 2.71 g/l. The center of the NSSA aquifer system is mostly affected. Abstraction was stopped in a third scenario, resulting in increasing groundwater reserves by .7 Mm3/year and a salinity response of 1,47 g/l. NSSA groundwater qualitu and reserves could improved considerably if government abstraction rules were given serious consideration by the users.