Status of the Korba groundwater resources (Tunisia): observations and three-dimensional modelling of seawater intrusion

Abstract

The Korba aquifer is located in the east of the Cape Bon peninsula in Tunisia. A large groundwater depression has been created in the central part of the aquifer since the 1980s, due to intense groundwater pumping for irrigation. The data collected show that the situation continues to deteriorate. Consequently, seawater is continuing to invade a large part of the aquifer. To better understand the situation and try to forecast its evolution, a three-dimensional (3D) transient density-dependent groundwater model has been developed. The model building process was difficult because of data required on groundwater discharge from thousands of unmonitored private wells. To circumvent that difficulty, indirect exhaustive information including remote sensing data and the physical parameters of the aquifer have been used in a multi-linear regression framework. The resulting 3D model shows that the aquifer is over-exploited. It also shows that after 50 years of exploitation, the time needed to turn back to the natural situation would be about 150 years if the authorities would ban all exploitation now. Such an asymmetry in the time scales required to contaminate or remediate an aquifer is an important characteristic of coastal aquifers that must be taken into account in their management.

Modeling the spatial and temporal distribution of coastal groundwater discharge for different water use scenarios under epistemic uncertainty: case study in South Portugal

“…Sophocleous 2002;Eamus and Froend 2006). Research on the interactions between groundwater and the sea until recently has been mainly focused on seawater intrusion (e.g., Zhang et al 2004;Kerrou et al 2010;Watson et al 2010;Lu et al 2011;Koussis et al 2012;Gaaloul 2012;Ghassemi et al 2012), despite recognition that submarine groundwater discharge (SGD) can have a significant impact on marine ecology (Taniguchi et al 2002;Burnett et al 2006). …”

On the interpretation of coastal aquifer water level trends and water balances: A precautionary note

“…The latter volumetric change is significant relative to freshwater discharge to the sea, which was approximately 6.9 Mm 3 /yr in 2003. For the Korba aquifer in north-eastern Tunisia, Kerrou et al (2010) used numerical modelling to show that the change in seawater volume in 2004 was 8.9 Mm 3 /yr. This seawater volume change was also a significant proportion of the water balance given estimates of total inflows and total outflows of 46 Mm 3 /yr and 67 Mm 3 /yr, respectively.…”

“…Combinations of typical values of K (5 m/d, 20 m/d, 200 m/d), z 0 (25 m, 50 m, 100 m) and W net (1 mm/yr, 10 mm/yr, 50 mm/yr, 100 mm/yr) were used, consistent with the collective range of parameters reported byMoe et al (2001), Wer- ner andGallagher (2006),Zulfic et al (2007),Kacimov et al (2009), Kerrou et al (2010 andWatson et al (2010).…”

Grid-enabled Monte Carlo analysis of the impacts of uncertain discharge rates on seawater intrusion in the Korba aquifer (Tunisia)

“…None of these wells is equipped with a flow meter and no survey has ever been made to estimate exhaustively their exploitation rates. Kerrou et al (2010) built a multi-linear regression model to estimate the pumping rates in the Korba aquifer by combining a series of explanatory exhaustive variables describing the state of the aquifer, its properties, as well as data from remote sensing analysis. The pumping rate estimates were then used to calibrate a three-dimensional (3-D) density-dependent flow and miscible solute transport model, but without accounting for the uncertainty in the estimated pumping rates, in particular their spatial distribution.…”