2025年夏季汉江中下游遭遇极枯水与高温双重胁迫，干流暴发蓝藻水华，严重威胁沿江城市饮用水水源地供水安全。为探究极端水文气象条件下蓝藻水华的影响机制及对水源地供水的影响，于2025年夏季8月25日至29日开展了汉江中下游干流水源地水质与水生态指标监测，并对主要城市供水水厂开展专项调查，重点评估制水工艺、藻类与嗅味物质处理能力、水华影响程度及应对措施。结果表明：汉江中下游干流出现大范围蓝藻水华，主要分布于宜城市至武汉宗关水厂江段，以轻度水华为主，钟祥、仙桃、汉川城南等水源地出现中度水华，总藻密度在2.12×10⁷~7.10×10⁷ cells/L之间，优势种均为蓝藻门假鱼腥藻属，未检出藻毒素，但检出嗅味物质2-甲基异莰醇和土臭素，浓度分别为34.2 ng/L和21.5 ng/L；极枯高温导致水体流动性减弱、营养盐浓缩，是水华暴发的主要诱因。受此影响，多数水厂供水成本明显增加，常规处理工艺对藻类及嗅味物质的去除能力存在局限，供水安全保障压力较大。基于调查与监测结果，本文从水资源调度、水厂应急处理能力提升、水华监测预警防控等方面提出治理路径，以期为极端水文气象条件下汉江中下游流域供水安全保障及水华防控提供科学依据与实践参考。

【Objectives】 The mainstream of the middle and lower Hanjiang River serves as a vital drinking water source for cities along its banks. During the summer of 2025, the middle and lower reaches of the Hanjiang River were suffered from the dual stress of extreme low water and high tempertures, coupled with cyanobacterial blooms broke out in the mainstream, which severely threatening the drinking water supply safety of water sources for cities along the river. This study is designed to investigate the mechanisms by which cyanobacterial blooms are affected under extreme hydro-meteorological conditions and their impacts on water supply from drinking water source areas.【Methods】 In the summer of 2025, specifically from August 25 to 29, the project team conducted monitoring of water quality and aquatic ecological indicators at drinking water sources in the main stream of the middle and lower reaches of the Han River. It also carried out a dedicated survey of water supply plants in major cities, focusing on assessing water treatment processes, the capacity to treat algae and taste-and-odor compounds, the extent of cyanobacterial bloom impacts, and relevant response measures.【Results】The results indicate that a large-scale cyanobacterial bloom occurred in the main stream of the middle and lower reaches of the Han River. It was mainly distributed in the river section from Yicheng City to the Zongguan Water Plant in Wuhan, with mild blooms predominating. Moderate cyanobacterial blooms were observed in water source areas including those in Zhongxiang, Xiantao, and Chengnan in Hanchuan, among other sites. The total algal density ranged from 2.12 × 10⁷ to 7.10 × 10⁷ cells/L. The dominant species all belonged to the cyanobacterial genus Pseudanabaena. Cyanotoxin concentrations were below the limit of detection (LOD), but the taste-and-odor compounds 2-methylisoborneol (2-MIB) and geosmin were detected at concentrations of 34.2 ng/L and 21.5 ng/L, respectively.Extreme low-water and high-temperature conditions reduced water flow and concentrated nutrients, which were the main triggers of the cyanobacterial bloom. As a result, water supply costs increased significantly for most water treatment plants. Conventional treatment processes have limited capacity to remove algae and taste-and-odor compounds, placing considerable pressure on ensuring the safety of drinking water supply.【Conclusions】Based on the water treatment plant survey, water quality and aquatic ecological monitoring results, this paper proposes management strategies in terms of water resource dispatch, enhancement of emergency treatment capacity at water treatment plants, and simultaneous monitoring of hydrological, water quality, and aquatic ecological parameters, early warning of cyanobacterial blooms, and prevention and control of cyanobacterial blooms. The above work is expected to provide a scientific basis and practical reference for ensuring water supply safety and preventing and controlling cyanobacterial blooms in the middle and lower reaches of the Han River Basin under extreme hydro-meteorological conditions.