GIS-based assessment of aquifer vulnerability using DRASTIC model and stable isotope: a case study on Essaouira basin

Abstract

Groundwater in the present study is defined as a sensitive contamination of fresh water to various pollutants that are made by human or natural elements. The research sought to measure the vulnerability of groundwater in the semi-arid regions and to identify sites where protection is likely needed by way of examining the resources relative to the sources of pollutants in the Meskala–Krimat sub-basin by using the DRASTIC model in the Geographic Information System (GIS) environment. The DRASTIC index resulting from the groundwater modeling that ranges between 114 and 191 were classified into three categories: low vulnerability which signifies 1.7% confidence level, moderate vulnerability which signifies 14.7% confidence level, and high vulnerability which signifies 83.7% confidence level. Analyzing this approach disclosed the electrical conductivity from the upstream part increased compared with the downstream part of the study area due to susceptibility to the high mineralization and leaching of Tidzi Diapir. In addition, the groundwater flow remained in the same direction from northeast to northwest and from northeast to southwest during the four campaigns 2007, 2018, 2019, and 2020. Stable isotope (2H and 18O) measurements indicate that the Atlantic rainfall is continuously recharging the watershed recharge areas. And so, the low values of tritium (3H) in the groundwater signify that the fresh water in the Cenemano-Turonien aquifer is old. The present study proved that DRASTIC modeling using GIS is an effective technique in managing and protecting the vulnerable groundwater.