Quality assessment of groundwater in a crystalline semi-urbanised environment (Lefock watershed, Cameroon)

Abstract

This study provides an assessment of the hydrogeochemical processes influencing shallow groundwater quality in the Lefock watershed (crystalline area, Cameroon). Seventeen groundwater samples were collected in May 2021 during the rainy season. These samples were analysed for their physical characteristics and major ions composition. The result showed values within the WHO safe limits, except for pH which is acidic (below the lower limit of 6.5) for 94% of the samples and Fe²⁺, HCO₃ ⁻ and NO₃₋, whose concentrations are above the WHO (2017) limit for 12%, 88% and 12% of the samples respectively. Conventional hydrogeochemical diagrams, water quality assessment indices, and multivariate statistical analysis showed that the main factors influencing groundwater chemistry in the study area are silicates weathering, leaching of the unsaturated zone of the saprolite, leaching of atmospheric pollutants by rainwater and anthropogenic contamination. The spatial distribution of NO₃ ⁻, Na⁺ and piezometric levels implies that groundwater is spatially influenced by land use, saturated zone of saprolite aquifers and groundwater flowpath directions. These results provide useful information for groundwater management in a semi-urban environment with heterogeneous aquifers and, in particular, the need to consider groundwater flowpath and land use stratification when planning groundwater management strategies.