Seasonal Evolution of Surface Water Quality in the Tropical Sub-basin of the Tilé River, Guinea

Abstract

This study assesses the physicochemical and microbiological quality of the Tilé River in N’Zérékoré (Republic of Guinea) according to seasonal variability. The study, conducted at five sampling sites, reveals that during the rainy season, the waters exhibit moderate temperatures (15.71-21.28 °C), a neutral to slightly acidic pH (6.93-7.27), high conductivity (up to 932.67 µS/cm), and high concentrations of suspended solids (up to 786.67 mg/L) and turbidity (130.67-184.33 NTU). Nitrate levels reach 60.3 mg/L, and fecal contamination is significant, with fecal coliform counts reaching up to 603.67 CFU/100 mL. During the dry season, the temperature increases (21.45-25.78 °C) and the pH become slightly alkaline (7.08–7.41), while conductivity, turbidity, and suspended solids decrease significantly. Nitrate concentrations remain low (4.60-8.96 mg/L) and fecal contamination is reduced (≤ 80 CFU/100 mL). Principal Component Analysis (PCA) highlights three key factors influencing seasonal variability: (i) suspended solids loading and turbidity, (ii) nutrients (NO₃⁻, PO₄³⁻), and (iii) microbiological indicators. The results indicate that the rainy season is characterized by a strong positive correlation between these parameters, reflecting the effect of runoff and anthropogenic inputs, while the dry season reflects generally better water quality, although locally affected by domestic and commercial discharges. This study contributes empirical data from West Africa, helping to fill major gaps in global water quality knowledge from tropical basins. The findings support improved prediction of pollution dynamics and ecological responses across wet and dry seasons in Tilé river. Moreover, the findings of the research may be helpful for decision-makers of the region for doing the needful to monitor water quality in Tilé river and for the sustainable preservation of the Tilé River. The study's findings offer valuable scientific data that could inform the development of local policies for integrated water resource management in Guinea, a country often referred to as the 'water tower of West Africa' but facing increasing threats to its water resources. By highlighting the degradation of water quality, particularly during the rainy season due to anthropogenic inputs, the research underscores a global problem and provides a crucial reference for similar urban basins in West Africa and beyond, contributing to the broader understanding of environmental vulnerability in developing regions.