(ZHU XIANG)

Tourists watch water gushing out of the Xiaolangdi Reservoir on the Yellow River during a sand-washing operation in Luoyang, Henan Province, on June 30.

The operation works by discharging water from the reservoir to clear up the sediment in the Yellow River, the country's second longest waterway.

The Yellow River has been plagued by an increasing amount of mud and sand. Each year, the river bed rises as silt deposits build up, slowing currents in its lower reaches.