Anthropogenic features in the sines (Portugal) and essaouira (Morocco) coastal aquifers: A comparative study of their hydrochemical evolution by a principal component analysis

Abstract

Considering the effects of climatic conditions on groundwater resources salinization and quality, a comparative study was conducted on the coastal aquifers of Sines (Portugal) and Essaouira (Morocco). Under the climatic and environmental conditions these two basins present different vulnerabilities to anthropogenic activities. Both aquifers correspond to sedimentary basins with similar structures and lithologies. From the available physical, chemical and piezometric data, two series of results of each area were selected corresponding to two different years that were analysed by Principal Component Analysis (PCA). Sines basin is characterised by a temperate climate. In the Sines aquifer the water-rock interaction process is the major mechanism responsible for the groundwater evolution, conferring a calcium-bicarbonate facies. Applying the PCA, punctual anthropogenic contamination was identified and linked to agricultural activities. The water resources of the Essaouira basin are characteristic of a semi-arid climate, and are severely impacted by the climate (quantity and quality). PCA allowed the evaluation of the contribution of the Tidzi diapir in the water recharge that confers to the groundwater a sodium-chloride facies. Although this statistical method did not shown a nitrate contamination input in the Essaouira multi-aquifer, this polluent presents locally high values. Also the very high evaporation and scarce precipitation activate the processes of salinization and contamination.