The bureau also encourages residents to report any illegal pollution discharges by contacting the government's hotline.

Zheng said water quality is closely related to public health, and the government should attach significant importance to the issue and further strengthen supervision of local water pollution.

A bird's-eye view of the polluted Xiaojiang River in March. GUO TIELIU / For China Daily

According to the China Water Pollution Map issued by the Institute of Public and Environmental Affairs, an environmental NGO, the upper Xiaojiang River is scattered with several heavy metal pollution sources.

The map provides information on the country's water quality, discharge of pollutants, pollution sources, businesses that exceed discharge quotas, and sewage treatment plants from about 300 prefecture-level cities nationwide.

Ma Jun, director of the Institute of Public and Environmental Affairs, said water quality is worsening in most Chinese rivers due to over-exploitation and poor supervision.

Wang said that in addition to discharges from enterprises, the harsh natural environment, poor forest cover and occasional debris in the water also contribute to declining water quality in the region.

Excessive levels of the organic compound aniline were found recently in well water in Cangxian county, Hebei province, turning the water red. The county's former head of the environmental protection bureau denied any risk at first, saying "the color does not mean the water is polluted as water, after boiling with red beans, turns the same color."

His response triggered public outrage, and he was dismissed soon afterward.

A team has been set up to study the cause of the pollution but no results have been released to date.

Guo Anfei in Kunming contributed to this story.