Determination of Groundwater Vulnerability Using the DRASTIC Method in Ouargla Shallow Aquifer (Algerian Sahara)

Groundwater is the main source for many uses around the city of Ouargla. In this study, the DRASTIC method was used to assess the vulnerability of the groundwater aquifer. Seven hydrogeological parameters of the model (D water depth, R efficient charging, A aquifer type, S soil type, T topography, I unsaturated zone and C hydraulic conductivity) were measured and mapped. The intrinsic vulnerability map of the shallow aquifer, using the DRASTIC method, shows a high to very high vulnerability to pollution; 91.6% of the study area has high vulnerability, 8.4% of it has very high vulnerability. The comparison of the DRASTIC maps with the land use map illustrates that the agglomerations and irrigated areas are the most vulnerable areas to pollution, due to the low depth of the aquifer and the infiltration of significant domestic and irrigation wastewater. The results show that the relationship coefficient between the DRASTIC index and nitrate concentration is R = 0.73. This indicates that the groundwater vulnerability mapping by using the DRASTIC method can be applied for sensible groundwater resources management and land-use planning in the study area.