Sentinel-2 Observation of Water Color Variations in Inland Water across Guangzhou and Shenzhen after the Establishment of the Guangdong-Hong Kong-Macao Bay Area

Guangzhou and Shenzhen are two core cities in the Guangdong-Hong Kong-Macao Greater Bay Area (GBA). It is increasingly important to regulate water quality urban development. The Forel–Ule Index (FUI) can be obtained by optical data an indicator. Therefore, we used Sentinel-2 calculate FUI of 41 lakes reservoirs from January December 2016–2021, analyzed their spatio-temporal variations, including spatial distributions, seasonal inter-annual variations. We also performed a correlation analysis driving factors. In Guangzhou, was low north west, high south east. Shenzhen, west Moreover, 68% exhibited with summer autumn, levels spring winter. had lowest autumn. Furthermore, 36% increasing whereas stable decreasing Among herein, 10 areas were positively correlated precipitation, while 31 negatively precipitation. Increased precipitation leads increase external pollutants sediment, as well resuspension substances water, resulting more turbid water. FUI, decrease FUI. These findings design suitable management policies maintain control local quality.