Groundwater vulnerability and risk assessment coupled with hydrogeochemical analysis in the Taza aquifer (Morocco)

Abstract

This study assesses the vulnerability of aquifers to increased contamination, influenced by rapid peri-urbanization and deficient sanitary infrastructure. The research focuses on the Taza aquifer in northeastern Morocco, where we applied the DRASTIC and GOD models. We further enhanced the DRASTIC method by the addition of a Fracture Index (F) ‘’DRASTICF‘’ to incorporate the effects of tectonics and geological discontinuities on groundwater behavior. The vulnerability mapping was performed for two distinct dry and wet periods of 2016 and 2021 respectively. Moreover, the use of hydrogeochemical analysis of 22 groundwater samples helped to identify potential sources of pollution and to understand the hydrogeological process. The results indicate a dynamic in vulnerability between these two periods due to changes in the recharge parameter and groundwater depth. The comparison between obtained vulnerability maps and nitrate concentrations reveals vulnerable zones that closely resemble regions affected by nitrate pollution. This area is predominantly classified as of high vulnerability at 27 %, associated with an estimated pollution level of 36%. The findings underscore also the importance of integrating the fracture index into the assessment of aquifer vulnerability alongside the different models. This integration offers an enriched perspective for effectively managing risks associated with groundwater contamination. The risk maps of groundwater contamination were also established by overlapping the vulnerability map with the land use layer. The main hydrogeochemical facies determined in the Piper Diagram allowed classifying the waters as Ca–Mg–HCO3 type. The significant correlations indicated that groundwater mineralization in the study area originates from the dissolution of limestone and evaporated formations. The water quality within the study area shows substantial variability, ranging from excellent to unsuitable, primarily due to the leaching of fertilizers and wastewater.The different results can be very helpful to the farmers, and local authorities for better groundwater sustainable management.