Vulnerability Study by DRASTIC Method for Eocene and Turonian Aquifers in the Tadla Plain

Abstract

In numerous regions across Morocco, groundwater quality has undergone a significant decline in recent years, primarily due to factors such as agricultural expansion, improper solid waste disposal, and industrialization. This study presents an analysis of the vulnerability of two primary shallow aquifers, namely the Turonian and Eocene. The vulnerability assessment entails the evaluation of the aquifers' susceptibility to various forms of surface pollution, based on the physical characteristics of their surroundings. Within the Moroccan context, the DRASTIC method, integrated with Geographic Information Systems (GIS), emerges as the most suitable approach. This method involves the processing and analysis of seven factors pertaining to the three soil compartments, encompassing land cover, the unsaturated zone, and the saturated zone. Each chosen parameter is assigned a weight, reflecting its significance concerning groundwater protection. Notably, the water table's depth and the nature of the vadose zone exert the most substantial influence, followed by factors like recharge. Conversely, topography exhibits minimal impact, with soil type following suit. Lastly, the nature of the aquifer medium and its conductivity carry a moderate degree of influence. Each parameter is further categorized into classes, each defined by a specific rating. To derive an all-encompassing measure of vulnerability, the weights and scores of these various factors are synthesized through an additive model, yielding the comprehensive "DRASTIC Index." Subsequently, this index is employed to assess the intrinsic vulnerability level of the Turonian and Eocene aquifers by superimposing the seven index maps.