Presenter: Dr. Ting Zhou, Anhui Agricultural University
Co-author(s): Dr. Bo Jiang, Changjiang Water Resources Protection Institute, China
Sub-theme
4. Supporting Aquatic Ecosystem Health and Functions
Topic
4-8. Water quality improvement
Body
Chaohu Lake (117° 16'54"-117°51'46"E,31° 43'28"-31° 25'28 " N) is the fifth largest shallow inland lake and a typical eutrophic lake in China. The meteorological factors and socioeconomic conditions create suitable conditions for HABs outbreak in Chaohu Lake, leading to an increasing growth of harmful algal blooms (HABs) since 1990s. However, this deteriorating situation has been greatly reversed in the past three years, attracting much attention and provides valuable significance for environmental management. In order to explore the reason for HABs improvement during the last three years, we tracked long-term dynamics of HABs in Chaohu lake using high frequency MODIS remote sensing daily observations, from 2000 to 2022. The Floating Algae Index (FAI) was applied to detect the area and severity of HABs. Results show that the HABs evolution course of Chaohu Lake can be divided into four stages: light (2000-2006) , fast-growing (2007-2017), deteriorating (2018-2019) and sharp improvement (2020-2022). Driving forces of HABs for Chaohu lake include meterological factors and socioeconomic factors. Meterological driving forces include precipitation, temperature, wind force, etc.; socioeconomic driving forces include GDP, population and government management measures and policies. Quantitative attribution analysis showed that the sharp improvement is attributed to government management and policies: 1. the government carried out the “promote Chaohu Lake as the best name card of Hefei city” Act to systematically curb both the water and basin environment of Chaohu Lake; 2. ten wetlands around Chaohu Lake with a total area of 100 km2 were established to purify inflow water quality; 3. the operation of “water transfer project from the Yangtze River to Huaihe River” significantly improved water exchange rate and improved water quality of Chaohu lake. These countermeasures created huge improvement for the HABs during the past three years, even though unfavorable meterological conditions such as long-lasting high tempreture, flooding occurred in HABs season. These practices provide significance for managing eutrophic algae-prone lakes, but also provide references for rivers and lakes facing the risk of ecological and environmental deterioration.