Every Saturday Zhang Junfeng hikes along the rivers, ravines and reservoirs of Beijing.

He leads a particular kind of nature tour - pointing out signs of pollution.

"People typically learn about pollution by reading and by watching TV, and very few people bother to see what the pollution is really like by themselves," said Zhang, one of the founders of the non-government organization Happy Water Journeys.

Over the past five years, the 49-year-old has led more than 20,000 people for the environmental group's routine Saturday hiking trips.

"We go to the sewage drains exiting into rivers, to water heads and dried riverbeds. People can talk to each other and see the garbage in the rivers and know how some rivers stink."

Zhang's interest in Beijing's rivers can be traced to the early 1990s when he worked as a satellite engineer with poverty alleviation programs in Sichuan province, helping build roads in mountainous areas.

After he returned to Beijing, Zhang started to tour the rivers in Beijing with his son on the weekends. He also went to study rivers and ecology for a master's degree at China Agricultural University.

By the time he started Happy Water Journeys in 2007 at the invitation of many environmentalists, Zhang had already gained expertise in rivers and reservoirs through numerous driving trips between 2003 and 2007.

"He sticks to the routine of hiking along rivers every Saturday, even though nobody joins him on cold winter days or on Chinese New Year," said Wang Weiguo, 49.

Zhang Junfeng, a 49-year-old Beijing resident, has been hiking along the rivers, ravines and reservoirs in the capital every Saturday since 2007 to monitor the water quality. Xu Wei / China Daily