Mapping of the Vulnerability to Pollution of El Oued Shallow Aquifer in the Algerian Sahara

Abstract

The mapping of the intrinsic vulnerability of the shallow aquifer of El Oued, carried out following the DRASTIC method, shows a medium to high vulnerability to pollution. Up to 78.7% of the aquifer’s surface area is highly vulnerable, while 21.3% has a medium vulnerability. The comparison of the DRASTIC maps with land-use map shows that the urban and areas irrigated by wells of the deep aquifers (CT and CI) are the most vulnerable areas to pollution. Depth to water parameter inflicted the largest impact on the vulnerability index followed by the recharge. The superposition of the DRASTIC map with nitrates map shows permitted the validation of the DRASTIC vulnerability map of the shallow aquifer of El Oued is valid. The coincidence rate between the medium concentration of nitrates and the moderate vulnerability class is 92%, and the coincidence rate between the high concentration of nitrates and high vulnerability class is 71%.