China's Three Gorges Project, the world's largest hydropower project, has seen water quality either remain stable or improve in the section located in the country's southwestern Chongqing municipality.

The water quality?of Three Gorges Project remain stable or improve in the section located in Chongqing municipality. [Xinhua file photo]

The water quality of the Yangtze River in the Chongqing section of the Three Gorges reservoir tops that of all China's seven major river systems, according to the Chongqing Municipal Environmental Protection Bureau.

The water quality of the Yangtze River's leave-boundary river section in Chongqing has maintained the level-II national water quality standard, which is second-highest ranking in the five-grade standard.

To maintain and improve the area's water environment, Chongqing has worked to clean up its 21 secondary rivers and set up waste and sewage treatment plants in all of its counties and major townships in the past 15 years.

Located on the middle reaches of the Yangtze River, China's longest waterway, the Three Gorges Project consists of a 185-meter-high dam, a five-tier ship lock, a reservoir and 32 hydropower generators.