Mapping the impact of quarrying on karst groundwater resources in a semi-arid region using GIS and remote sensing: A case study of the agourai aquifer, Middle atlas, Morocco

Abstract

The karst aquifer of Agourai serves as a vital water source for nearby populations, providing both drinking water and irrigation for agriculture. Over the past two decades, it has been subjected to extensive limestone quarrying, leading to the formation of hydrogeological discontinuities that disrupt subsurface water flow. When quarrying activities ceased, the site was converted into an uncontrolled landfill, continuously receiving construction waste. Under the influence of rainfall or groundwater infiltration in the case of very deep quarries this waste degrades into liquid contaminants, posing a significant threat to groundwater resources.

In this study, the objective is to identify vulnerable exploitation areas and assess the effects of anthropogenic activities on local hydrogeology and spring emergence. We adopt a comprehensive approach that integrates geological, structural, and hydrogeological analyses, along with the spatiotemporal history of three typical quarries for each impact. The methodology integrates remote sensing to acquire comprehensive data on surface characteristics and their spatial variations. This data is processed and analyzed using Geographic Information Systems (GIS) to assess spatial relationships and impacts. Direct hydrogeological measurements provide ground-truth data on subsurface water conditions, which validate and enhance the findings from remote sensing and GIS analyses.

The research findings reveal widespread quarrying activities, including 17 quarries across a total area of 227 ha. The extraction of Liassic aggregates negatively affects subsurface drainage, cave systems, and spring discharge. The impact is particularly severe in the main drainage areas, where the extent of the disturbances is broader. However, these conclusions remain constrained by the necessity to incorporate data specific to karst peculiarities, such as tracer tests and hydrogeological modeling, this gap is addressed by the COP approach, one of the most effective methods for assessing the vulnerability of karst groundwater. It was used to determine the specific vulnerability of quarries as well as that of aquifers in general, providing a large-scale overview.