Hydrodynamic and salinity evolution of groundwaters during artificial recharge within semi-arid coastal aquifers: A case study of El Khairat aquifer system in Enfidha (Tunisian Sahel)

In common with most coastal aquifers, the El Khairat aquifer suffers the imbalance between recharge and intense exploitation and the extent of agricultural activity. As it is part of the Tunisian Sahel, the Enfidha region has a semiarid climate with very irregular rainfall which makes the groundwater resources quite fragile. This region has major difficulties in managing its water resources which are in decline, especially since, for the last decades, their renewal by rainwater has no longer been sufficient to re-establish the equilibrium. In such a case, the artificial recharge of aquifers by water from dams is a credible alternative to preserve the water resources against marine intrusion and pronounced fall in the piezometric level. The present investigation, based on available data, is aimed to monitoring the piezometry of the El Khairat aquifer during artificial recharge operations (2002-2005) by water from the dam and to identify the impact of the artificial recharge on groundwater quality. The results of this monitoring have shown that the artificial recharge realized between 2002 and 2005, had for effect an increase of the piezometric level of the phreatic aquifer of +0.4 to +2.63m, especially in the "Ain Garci" zone. The piezometric level of the deep aquifer has also recorded an important increase reaching +3.82m. After artificial recharge of the aquifer, the spatial distribution of the salinity shows quite low salinity values (lower than 2g/l) in the western and north-eastern parts of the aquifer, the zone of artificial recharge, whereas the highest ones are found especially in the coastal zones and at the boundaries of the Sebkha where they exceeded 3g/l. Moreover, we note a slight salinity reduction toward a central zone of the aquifer. Indeed, the zone characterized by salinity lower than 2g/l and situated near the recharge site becomes more extensive.