Aerial photo taken on Aug. 10, 2019 shows a tributary of Erhai Lake in Dali, southwest China's Yunnan province. Water quality of Erhai Lake has improved with active treatment since the beginning of this year. [Photo/Xinhua]

Villagers eliminate water plants in Erhai Lake in Dali, southwest China's Yunnan province, Aug. 10, 2019. Water quality of Erhai Lake has improved with active treatment since the beginning of this year. [Photo/Xinhua]

Tourists visit Erhai Lake in Dali, southwest China's Yunnan province, Aug. 10, 2019. Water quality of Erhai Lake has improved with active treatment since the beginning of this year. [Photo/Xinhua]

Villagers eliminate water plants in Erhai Lake in Dali, southwest China's Yunnan province, Aug. 10, 2019. Water quality of Erhai Lake has improved with active treatment since the beginning of this year. [Photo/Xinhua]

Photo taken on Aug. 10, 2019 shows the view of Erhai Lake in Dali, southwest China's Yunnan province Water quality of Erhai Lake has improved with active treatment since the beginning of this year. [Photo/Xinhua]