Local people swim in the Erhai Lake in Dali Bai Autonomous Prefecture southwest China's Yunnan Province, Dec. 9, 2015. Thanks to the efforts of local government in controlling pollution in the famous plateau lake and improving the local environment, the water quality of the Erhai Lake has been clearly improved in recent two years. The lake, covering 253 square kilometers and named as the "mother lake" by local people, saw blooms of blue green algae in 1996 and 2003. (Xinhua/Lin Yiguang)