Césard Millogo^{1, 2,}, Aboubakar Sako^{1, 2}, Blehiman Sagnon³, Samuel Nakolendoussé²

In central southern Burkina Faso, as elsewhere in the country, groundwater resources are the reliable source of drinking water. During its residence time in the rocks, the groundwater interacts with them and its chemical composition is considerably modified. Methods like major ions geochemistry, the assessment of water quality indices, and the application of geostatistical analysis have been utilized to define the hydrogeochemical processes governing groundwater quality. For this study, 249 groundwater samples were taken from manual boreholes. The findings indicated that the groundwaters ranged from circumneutral to alkaline, with predominant concentrations of Ca²⁺, Mg²⁺ and HCO₃^-. According to the calculated groundwater quality indices, water from the majority of the boreholes was suitable for domestic uses. However, a few boreholes had high concentrations of F^- and Fe_T that exceeded the World Health Organization recommended guideline value for drinking water. The elevated F^- concentrations were probably due to the weathering of the granitic rocks, while the Fe_T concentrations appeared to come from the water pumps installed on these boreholes. Bivariate plots indicated that geochemical processes like silicate weathering, mineral dissolution and precipitation, ion exchange, and evapotranspiration were the key factors affecting solute acquisition in groundwater. Furthermore, desorption and ion exchange in alkaline pH conditions could enhance F⁻ enrichment in groundwater. Zones with low ionic strength and electrical conductivity have been identified as groundwater recharge zones, which should be protected and subject to a regular monitoring program. This study results could help professionals in the field to implement appropriate groundwater quality management strategies.

fractured basement aquifers, spatial assessment, groundwater hydrochemical evolution, kriging, Burkina Faso