Many cities have begun tackling water pollution, buoyed by government cleanup goals and public support for ridding their communities of black, smelly rivers and ponds. But significant work remains, environmental experts say.

"The gap in water quality of major rivers crossing several provinces, such as the Yangtze and Songhua, and small rivers running through cities is wide," said Wu Shunze, deputy head of the Chinese Academy for Environmental Planning under the Ministry of Environmental Protection, on Monday.

While major rivers have seen improved water quality, thanks to growing attention from the authorities in recent years, public complaints about urban rivers continue, he said.