Spatiotemporal variability in global lakes turbidity derived from satellite imageries

Turbidity is a key indicator of water quality and has significant impacts on underwater light availability of lakes. But the spatiotemporal variability of turbidity, which is important for understanding comprehensive changes in the water quality and status of aquatic ecosystems, remains unclear on a global scale. In this study, the spatial distribution pattern, seasonal variability, spatiotemporal variability, and influencing factors of turbidity in 774 lakes worldwide have been investigated using the turbidity product of Copernicus Global Land Service (CGLS) derived from Sentinel-3 OLCI. We found that 63.4% of lakes show low turbidity (<= 5 Nephelometric Turbidity Units). The ranking of turbidity by climate zone is as follows: arid climate > tropical climate > temperate climate similar to polar climate > cold climate. Turbidity decreased significantly in 40% of studied lakes, and increased significantly in 32% lakes. The lake with low turbidity has less seasonal variation, and there is a large seasonal variation in lake turbidity in the tropical and polar climate zones of Northern Hemisphere. Positive covariates to turbidity of global lakes include wind speed of lake, slope, surface runoff, and population in the catchment. Conversely, negative covariates include lake area, volume, discharge, inflow of lake, and GDP. Abundant water volume, favorable flow conditions, and more financial investments in lake management can help to reduce turbidity. These findings highlight the spatiotemporal changes of global lake turbidity and underlying mechanisms in controlling the variability, providing valuable insights for future lake water quality management.