A worker removes residual contents from a sewage purification pond at a wastewater treatment plant in the Caohai National Nature Reserve in the Yi, Hui and Miao Autonomous County of Weining, southwest China's Guizhou Province, July 21, 2020. There was a time when the Caohai National Nature Reserve was threatened by water body recession and pollution, but in recent years its ecological system has greatly improved after a series of control measures were implemented here. (Photo by He Huan/Xinhua)
