Comparative assessment of the microbiological quality of groundwater and surface water in Copargo, northwestern Benin

Abstract

Microbiological contamination of water resources is a major public health issue in West Africa. This study characterizes the microbiological quality of water resources in the Pendjari and Ouémé basins (Copargo, Benin) and compares their vulnerability. Forty-two water points (boreholes, wells, rivers, and dams) were sampled during the high- and low-water seasons in 2023, yielding 84 samples. Analyses targeted total coliforms, Escherichia coli, fecal streptococci, and sulfite-reducing anaerobes following standard AFNOR methods. Results reveal widespread contamination of river and dam water, with exceedance rates (ER) and Non-Compliance Indices (NCI) of 100% for all indicators in high water and 95% in low water for fecal streptococci. Wells and boreholes show seasonal vulnerability (high water) with exceedance rates of 100 and 59%, respectively, but remain broadly compliant for sulfite-reducing anaerobes (ER = 0%). Contamination tends to be higher in Pendjari than in Ouémé, though not significantly (Mann-Whitney U test, p > 0.05). Vulnerability follows the gradient: rivers > dams > wells > boreholes. Strengthening monitoring during the rainy season and promoting protective structures are essential to reduce the health risk associated with consuming untreated water.