Beijing is to invest more heavily in the improvement of underground pipelines to match the rapid pace of construction in the capital.

Drainage networks will be expanded and some decade-old pipes will be renovated, said Guo Weidong, a civic official in charge of urban infrastructure management.

It will help alleviate problems that blighted the city during recent rainfall - such as the accumulation of water at the Yuquanying Overpass in the southwest and Honglingjin Overpass in the east.

Water rose 1-metre deep at the Yuquanying Overpass, submerging bicycles so that only their handlebars were visible.

These overpasses are mostly built along the Second and Third Ring roads, which circle the major parts of the city.

Some drivers even had to reach beneath the water surface for their number plates, which were washed off by the floods.

As a result, more efforts will be devoted to the city's road construction and management to prevent urban flooding during the rainy season, said Guo.

"Incidents of accumulated water at overpasses and pedestrian routes have signaled that more efforts must be made in the city's road construction and management," said Guo.

Civic construction chiefs said less than half of the city has adequate drainage. They did not explain which parts.

Drains with outdated designs have a smaller diameter (only 200 millimeters) and thus have a reduced ability to discharge water, contributing to the accumulation of water in the city.

More than 6 million meters of underground pipelines are in use in the city but are unable to meet demand.

Buildings are being built faster than pipelines are being laid, officials said.

Cao Xiuqin, a professor with the Urban Construction Engineering Department of Beijing Institute of Civil Engineering and Architecture, called for the clearing of drains before the onset of the rainy season.

"The slope of the pipes should also be taken into account when they are laid underground so the smooth flow of water is guaranteed," Cao said.

The accumulation of water is less severe in the east and north of the city because of good afforestation in those areas, said Wang Qian of the afforestation office under the Beijing Youth Foundation.

(China Daily July 3, 2002)