Dong Yonghong, a marathon runner, is a secondary school geography teacher in Ordos, Inner Mongolia autonomous region. Many years ago, when he was running a marathon along the Ulan Mulun River, the local "mother river", he noticed that people were discarding rubbish along the riverbank. That's when he got the idea to have his students participate in the protection of the river.

"The Ulan Mulun River is a first-class tributary of the Yellow River, and the entire length of the Kangbashi section is more than 40 kilometers, which is pretty much the distance of a full marathon," Dong said. He picked up the trash whenever he noticed it and reported the damaged to the riverbank online or to environmental protection departments. Over time, patrolling the river became part of his life.