Determining the sensitivity of Sentinel-2 bands to optically and non-optically active water quality parameters under high- and low-flow conditions in the cradle of Humankind World Heritage Site, South Africa

Abstract

Access to clean water is a global challenge, particularly in the Global South, where scarcity and pollution threaten human and ecosystem health. Traditional water quality monitoring is limited in spatial and temporal coverage, while satellite remote sensing provides an alternative for assessing optically and non-optically active water quality parameters (WQPs). This study evaluated the sensitivity of Sentinel-2 MSI bands to WQPs in the Cradle of the Humankind World Heritage Site, South Africa, an area impacted by acid mine drainage. In situ measurements of DO, EC, pH, temperature, chlorophyll-a, and suspended solids were collected from 40 sites under high- and low-flow conditions. The Sentinel-2 images were atmospherically corrected, resampled to 10 m, and the values were extracted to the sampling points. Using multiple linear regression, random forest, and partial dependence plots methods, results showed that DO strongly influenced most bands, while suspended solids dominated the optically active band responses.