Chongqing's Wushan clears 20,000 tons of river debris in the Yangtze annually

"The debris-clearing boats operate from around 7 am to dusk," Yu said. "The primary floating debris are straw, dead branches and weeds".

This debris is mainly washed down from the mountains along the river by heavy rain, so during the flood season, typically from May to October, the debris increases. Sometimes, all 36 boats need to be dispatched to conduct debris-cleaning operations, he said.