Hydrochemistry and its relationship with groundwater flow and geology in Al Madinah Al Munawarah Province, Kingdom of Saudi Arabia

Study region: A detailed study was performed in Al-Madinah Al-Munawarah Province, Kingdom of Saudi Arabia Study focus: Groundwater quality and availability are a serious concern in this aquifer owing to aridity, high-water demand and the absence of alternative water resources. A systematic study was performed to investigate hydrochemistry and its relationship with groundwater flow and geology using geochemical tools, multivariate statistical analysis and Pearson correlation matrix (PCM). New hydrological insights for the region: Hardness and high salinity restrict groundwater (> 50%) suitability for drinking. Restricted groundwater flow caused by the geological formations enhanced the groundwater salinity in the central part of the study site. High F- and NO3- recorded in the shallow GWL wells evident the anthropogenic input. Hierarchical cluster analysis (HCA) classified the groundwater wells into three clusters (C1, C2, C3). Groundwater chemistry is predominantly affected by evaporation (C1, C2, C3) followed by mineral weathering (C1). Principal component analysis also suggests that evaporation/evaporite dissolution, anthropogenic input and silicate and carbonate weathering affected the water chemistry. Geochemical tools and PCM also illustrate that groundwater in C1 wells is influenced by the weathering and cation exchange whereas, in C2 and C3 wells, water chemistry is chiefly regulated by evaporation/ evaporite dissolution, ion exchange and mineral weathering. This study recommended that policymakers and local municipalities should implement a regular monitoring plan to protect this aquifer.