关键词: 蓝藻水华;水动力条件;营养盐;水华预警;汉江中下游;2022年长江流域干旱;

Abstract: With the rapid economic and social development along the Hanjiang River and the operation of cascade water conservancy projects, the water environment quality and hydrodynamic conditions of the Hanjiang River have undergone great changes.The water bloom in the middle and lower reaches of the Hanjiang River breaks out frequently, severely challenging regional water security.In the summer of 2022,cyanobacterial blooms were discovered for the first time in the middle and lower reaches of the Hanjiang River under the extreme hydrological conditions of "unusual drought during the flood season" in the Yangtze River Basin.Based on the existing monitoring station network of the Changjiang River Basin Water Quality Monitoring Center, emergency monitoring of water blooms was carried out in a timely manner, and comprehensive analysis on monitoring data was conducted.The results indicate that:(1) High nutrient levels in the watershed water bodies were still the prerequisite for the occurrence of water blooms in summer of 2022,with high temperature, strong radiation, and high pH values as inducing factors, and a small amount of river streamflow as an external driving factor.(2) The spatiotemporal distribution and impact range of water blooms in the Hanjiang River are expanding, and the degree of eutrophication in the water body is detertiatating.Strengthening the joint use of water engineering, improving hydrodynamic conditions, and regulating environmental capacity are the most direct ways to alleviate the water blooms in the middle and lower reaches of the Hanjiang River.(3) Suggestions are proposed including optimizing the layout of the comprehensive station network, strengthening dynamic monitoring of all factors, improving basic research on water blooms, and establishing a collaborative mechanism for water bloom prevention and control.

Key words: cyanobacterial bloom; hydrodynamic conditions; nutrient salts; water bloom warning; middle and lower reaches of Hanjiang River; Chanjiang River basin drought in 2022;