A risk assessment method for remote sensing of cyanobacterial blooms in inland waters.

Abstract Cyanobacterial blooms (CABs) of inland waters is a typical and severe challenge for water resources management and environment protection. An accurate and spatial continuous risk assessment of CABs is critical for prediction and preparedness in advance. In this study, a multivariate integrated risk assessment (MIRA) method of CABs in inland waters was proposed. MIRA was simplified with the trophic levels, cyanobacterial and other aquatic plant condition using remote sensing indexes, including the Trophic State Index (TSI), Floating Algae Index (FAI) and Cyanobacteria and Macrophytes Index (CMI). First, dates of risk assessment were carefully selected based on TSI. Then, we obtained the trophic levels, cyanobacterial and other aquatic plant condition of water using TSI, CMI and FAI on the selected date, and further scored them pixel by pixel to quantify the risk value. Finally, the CABs risk of CABs in water was accurately assessed based on the pixel risk value. Based on Landsat 8 OLI dataset, MIRA were executed in three different lakes of Wuhan urban agglomeration (WUA) with different trophic state, and validated with water quality data and the results of relating studies. The results demonstrated that the risk of CABs in Lake LongGan was overall higher than that in Lake LiangZi and Lake FuTou. And the risk of CABs in east part of Lake Longgan is high than the other parts. Seasonally, the risk level ranking in Lake LiangZi was the highest in summer, while lowest in winter. However, the seasonal risk ranking was spring, summer, autumn, and winter in Lake LongGan. Based on the comparisons with monthly water quality classification results and results of existing study, including trophic level, ecology risk and algal extent, It showed that MIRA method is valuable for spatial continues and accurately identifying the risk of CABs in inland waters with potential eutrophication trends.