The groundwater in the catchment draining the town of Manga and the surrounding area, which is characteristic of crystalline basement aquifers, undergoes mineral exchange during its residence in the rocks. In addition, factors such as deforestation, human activities and their spatial distribution can influence the chemical composition of groundwater. To date, no geochemical characterisation study by spatial distribution has been carried out in the catchment area of the town of Manga. The main objective of this study was to determine the quality of groundwater and the spatial variations in its physico-chemical parameters. To achieve this, 94 water samples were collected from existing boreholes, stored in bottles, and sent to the laboratory for physicochemical analysis. The analysis results were processed and examined using univariate statistical methods for water quality, whereas kriging and inverse distance weighting (IDW) were employed to assess spatial distribution. The results indicate that the majority of samples exhibit excellent water quality, whereas some areas show elevated concentrations of specific ions, suggesting that the overall groundwater quality in the region remains largely intact. Spatial variations in pH, electrical conductivity, total dissolved solid and ionic strength were observed, with lower values in recharge areas and higher values in discharge zones of the aquifers. NO3 -concentrations in excess of WHO standards were not found in boreholes. The highest values were mainly concentrated in the north and north-western part of the study area which are the recharge zone. Spatial analysis revealed areas with moderate spatial dependence, often associated with anthropogenic contamination sources or natural factors such as geogenic mineralization. This study provides a robust framework for understanding the spatial distribution of groundwater quality in the Manga watershed. The results obtained open a promising perspective by suggesting the use of isotopes to accurately map recharge areas and deepen the understanding of infiltration flows in regions with elevated nitrate concentrations.

Hydrogeochemical, groundwater quality, spatial assessment, Kriging, Inverse Distance Weighting, Manga