Monitoring water color anomaly of lakes based on an integrated method using Landsat-8 OLI images

Abstract

Water color is a crucial optical indicator of water quality, polluted water bodies often show water color anomalies. To comprehensively understand the occurrence of water color anomalies in inland lakes, an integrated method was designed using the hue angle based on the Forel-Ule Index (FUI) model, and other remote sensing indices, including the Turbid Water Index (TWI), Floating Algae Index (FAI), and Cyanobacteria and Macrophytes Index (CMI). Based on all available Landsat-8 OLI images from 2013 to 2020, continuous monitoring was conducted in three different lakes in the middle of the Yangtze River, China. The results demonstrated that: (1) The proposed method can accurately identify algal blooms, high sediment loads, and eutrophication from the abnormal water color areas; (2) The calculated hue angles of sediment-dominated water were significantly higher than those of algal blooms and aquatic vegetation, providing a noticeable visual discoloration of water; (3) These water color anomalies exhibited significant correlations with the water quality and environmental conditions. This study serves as an example for accurate and spatially continuous assessment of water color anomaly and supports practical information to facilitate local water environment conservation.

Keywords

• water color anomaly
• hue angle
• spatio-temporal variation
• inland lakes
• landsat-8 oli