Physicochemical monitoring of Zadepleu waterfall river from Côte d'Ivoire using on-site and satellite measurements

Surface waters are exposed to climate variability and anthropogenic activities. This study focuses on the spatio-temporal monitoring of the physicochemical quality of the Zadepleu waterfall river in Côte d’Ivoire, combining monthly in situ measurements with satellite data. The parameters analysed include turbidity, chlorophyll-a derived from satellite data, nutrients (nitrates, phosphates), and other physicochemical parameters. The water quality index (WQI) was applied to the on-site data. The results reveal that the waters of the river, including the waterfall, are generally not potable (WQI > 100), with marked deterioration downstream of the bathing zone at station S3. The river experiences greater quality degradation during the dry season compared to the wet season, with mean WQI values of 374.50 and 217.24, respectively. Satellite data (Sentinel-2), processed using the R package Waterquality, enabled the assessment of turbidity and chlorophyll-a, showing seasonal variations with higher values during the rainy season. The average in situ turbidity value is 9.32 NTU. The indirect satellite measurements underestimate these turbidity values. The low concentrations of chlorophyll-a suggest that the water in this waterfall remains relatively in good condition in terms of nutrient levels. This study highlights the importance of sustainable management strategies to preserve this aquatic ecosystem.