Shifts, Trends, and Drivers of Lake Color Across China Since the 1980s

Lakes are sentinels of global changes and integrators of processes in watersheds. Changes of lake water quality can be observed in shifts in lake color, however, the prevalence of shifts and trends in color and relevant factors remain elusive. Here, a comprehensive examination of color in 2,550 Chinese lakes from 1984 to 2021 revealed that color in 68% of the lakes shifted toward shorter visual wavelengths. Lakes in the Tibetan Plateau had larger declines in wavelength than lakes in other areas. The factors associated with reduced visual wavelengths varied in different ecoregions. A warmer and wetter climate in deep lakes in western China is associated with shifts toward blue. Increased vegetation in watershed and decreased wind are associated with green‐yellow shifting to green‐cyan color in shallow lakes of eastern China. Our study highlights the heterogeneous controls of climate and humans on changing patterns of lake colors. Plain Language Summary Lakes are affected by climate and human activity, and water quality can be reflected in lake color. Several studies have mapped the variations in lake colors, but the changing patterns in lake color and relevant reasons over the past decades remain unclear. We used satellite images to track annual trends of lake color since the 1980s in China. We found that the lake color for 68% of the lakes is trending toward blue color. The blue lakes in western China became bluer, and the green‐yellow lakes in eastern China shifted to greener colors. For lakes in western China (e.g., Tibetan Plateau), higher temperature and rainfall correlated with bluer lakes. For the shallow lake in eastern China (e.g., Yangtze River plain), more forest and grassland around the lake and weaker wind reduced the substances in lakes and are related to the shift in color. This research highlights the function of satellite images in tracking historical variations in lake color. Our results can help in understanding of the changes in lake color and its responses to climate change and human activity. Key Points Widespread declines in visually dominant wavelengths are revealed in 68% of Chinese lakes over the past 40 years using Landsat images A warming and wetter climate is the main factor associated with deep and clear lakes becoming more blue More vegetation cover on land is associated with reducing green‐yellow color in shallow and turbid lakes