Impacts of Global Changes on Groundwater Resources in North-East Tunisia: The Case of the Grombalia Phreatic Aquifer

Abstract

Due to the growing water demand, especially for the agricultural development, the water management in the Grombalia region (NE Tunisia) exploits multiple sources of water. Rainfall is marked by a strong seasonal and interannual variability in time and over space. The regional aquifer has been intensively used for irrigation. Artificial groundwater recharge has been initiated in 1975, in order to reduce the piezometric depletion. It is fed by an important surface water transfer from the North-West of Tunisian since 1984 and by 3 local dams. As a consequence, the Grombalia aquifer system has undergone multiple hydrodynamic and hydrochemical changes, affecting it deeply during the last decades. This study investigates their consequences on the groundwater quantity and quality. In this context, a multi-tracer approach was carried out in the Grombalia basin, based on 4 field visits between March 2013 and April 2015. The recent piezometric decline varying between 0 and −18 m in the upstream part of the aquifer is due to the intense groundwater pumping. Conversely, a water level rise in the central and downstream parts is explained by the excess irrigation return flow: since 1992, the groundwater has risen of up to 2 m. The waterlogging creates many agricultural, environmental and economic problems because of the suffocation of plants. An increase in groundwater salinity is the consequence of agriculture intensification in the Grombalia basin.