2025年第二三季度水质指数和去年同期相比基本稳定，但受汛期影响，环比有所下降。

和上年同期相比， 2025年第一季度蔚蓝城市水环境指数等级为优良的城市占比从74.5%增加到82.4%，等级为一般的城市从19.9%减少到13.4%，较差的城市为2.2%，和上年同期持平，差的城市从3.3%减少到2.0%。

At around 8:00 p.m. on March 16, 2025, thallium (Tl) concentration at the Dahetan cross-city water monitoring section on the Leishui River (between Chenzhou and Leiyang) was detected at 0.13 μg/L—exceeding the national surface water quality standard limit of 0.1 μg/L for centralized drinking water sources. This posed a potential threat to downstream drinking water safety. Following the incident, both Chenzhou and Leiyang cities launched emergency environmental responses. Comprehensive actions were taken, including full-basin water sampling, source tracing, pollution interception, thallium removal measures, enhanced flow regulation, and real-time water quality monitoring along the river to safeguard public drinking water. According to public reports, thallium concentrations at downstream water plants remained below the national drinking water limit of 0.1 μg/L, and water supply safety was not compromised. Notably, the automated monitoring system played a key role by issuing an early warning when thallium exceeded limits at the Dahetan section, buying time for emergency response and supporting rapid environmental monitoring. This incident highlights the critical importance of robust water quality monitoring and pollution source management systems. In regions with high thallium pollution risks, further improvements to these systems remain essential.

From 2015 to 2025, from the "Ten Point Clean Water Action Plan" to the "Battle to Keep the Water Clear”, China has marked a decade of progress in water pollution control. Over this period, the implementation of the new Environmental Protection Law, nationwide central environmental inspections, the revision of the Water Pollution Prevention and Control Law, and the continuous refinement of the pollution permitting system have established a strong institutional framework for protecting water resources. As Chinese environmental organizations dedicated to water pollution prevention and public participation, the Institute of Public & Environmental Affairs (IPE) and Green Jiangnan (PECC) formed a joint research group to summarize the historic improvements in water quality, assess the effectiveness of public participation and innovative mechanisms, and analyze the role of multi-stakeholder engagement in advancing water pollution prevention.

This report reviews surface water quality data for 361 cities across China in the third and fourth quarters of 2024, along with changes in water quality trends since the fourth quarter of 2022. Overall, urban water environments in China continued to improve during the second half of 2024.

Compared to the same period last year, water quality improved in the second quarter of 2024. The proportion of cities with "excellent" or "good" water quality increased from 62.6% to 68.1%, while those with "fair" water quality decreased from 28.0% to 24.7%. Cities with "poor" water quality rose slightly from 6.1% to 5.0%, and those with "very poor" water quality decreased from 3.3% to 2.2%.

In the first quarter of 2024, among the 361 cities (Including counties directly governed by provinces), there were 288 cities with excellent CWEI grades, accounting for 79.8%, 56 cities with average grades, accounting for 15.5%, and 16 cities with poor and very poor grades, accounting for 4.7%.