Environmental volunteer Lei Yueqin can recall what the Nanming River, which flows through Guiyang, Guizhou province, was like in the early 1950s. It was so pristine, she said, that people would use its water directly for drinking, cooking and washing.

"Kids would swim and catch fish in the river," the 81-year-old said.

But the waterway - a tributary of the Yangtze River - was quickly polluted by the increase in manufacturing emissions and household sewage that came after reform and opening-up brought economic growth.

"The river was dirty and dark by the end of the last century," Lei said. "The fish couldn't survive. And it stank."

Lei has worked as a volunteer to patrol the Nanming since she retired in 1984. "I used to be able to walk about 15 kilometers a day," she said. "But I'm older now. I can only do 3 or 4 km at a time."

The retiree has drawn six maps by hand over the years, recording the water's color and odor, and pollution sources at various locations. She said eight factories, including a paper mill, coal-fired generators and a tannery, once operated along the river, pointing to a map she drew in 1994.

"The factories were relocated. But the pollution remained in the coming decade," she said.

The water began to drastically improve when the city's government launched a full-scale recovery program in 2012. Authorities have since spent 3.8 billion yuan ($546.5 million) to clean up the river.

The first phase, from 2012 to 2013, created a decontamination system, constructed silt-processing facilities, and renovated shutter dams, while the second phase, between 2014 and 2016, focused on building wastewater treatment plants.

The third phase, from 2016 to 2025, will develop regulations to separate rainwater and wastewater. It will also curb agricultural runoff, authorities said.

About 70 percent of the Nanming's water is classified as Grade III, clean enough for swimming or aquaculture, or Grade IV, meaning it is OK for industrial use or other purposes that do not bring it into direct contact with humans.

Improving the river's water is part of three major environmental protection projects that the government is undertaking with an investment of more than 40 billion yuan.

Guiyang has been working to expand its forest coverage. The plan calls for increasing coverage from 49 to 60 percent by 2020.

In 2004, Guiyang was recognized as China's first national-level forest city by the State Forestry Bureau, which has since become the National Forestry and Grassland Administration. The city is surrounded by 162,000 hectares of forest.

"Ecological revitalization encourages shared benefits," Gao Xiaowen, deputy director of the Guiyang Ecological Civilization Construction Committee, said in an earlier interview. "Soon, local people will see how they can share in the city's reconstruction plan."

Li Hanyi and Che Weiwei contributed to this story.

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