Vulnerability mapping and risk of groundwater of the oasis of Figuig, Morocco: application of DRASTIC and AVI methods

Abstract

Climate change, population growth, and agriculture contribute to a qualitative and quantitative deterioration of groundwater reserves. The protection of natural water resources is crucial, especially in arid areas. The purpose of this paper is to map the vulnerability and risk mapping of a Moroccan aquifer, i.e., the Figuig oasis, using DRASTIC (depth of water (D), net recharge (R), aquifer media (A), soil (S), topography (T), impact of the vadose zone (I), and hydraulic conductivity (C)) and AVI (aquifer vulnerability index) methods. DRASTIC vulnerability maps have been drawn up for 4 years (1995, 2004, 2008, and 2010). Thematic maps were performed by both methods using the geographic information system (GIS). The DRASTIC method was modified in order to take into account the numerous faults. The AVI method allows estimating the transfer of a pollutant from the surface to the water level. Both methods give consistent results, enhancing high, medium, and moderate vulnerability. Risk assessment of groundwater pollution by septic tanks has been achieved by integrating the modified DRASTIC vulnerability map. Three areas with high, moderate, and low risk assessment have been identified and mapped.