Aerial photo shows workers clearing away the duckweed in Yangxiagang river in Dongsheng Village of Huzhou City, east China's Zhejiang Province, Aug. 11, 2018. (Xinhua/Xu Yu)

Aerial photo shows workers clearing away the duckweed in Yangxiagang river in Dongsheng Village of Huzhou City, east China's Zhejiang Province, Aug. 11, 2018. (Xinhua/Xu Yu)

Workers clear away the duckweed in Yangxiagang river in Dongsheng Village of Huzhou City, east China's Zhejiang Province, Aug. 11, 2018. (Xinhua/Xu Yu)

Aerial photo shows workers clearing away the duckweed in Yangxiagang river in Dongsheng Village of Huzhou City, east China's Zhejiang Province, Aug. 11, 2018. (Xinhua/Xu Yu)