BEIJING, Nov. 22  -- Beijing will gradually shut down 6,900 urban wells in the next five years to protect groundwater and improve drinking water quality.

The wells provide 240 million cubic meters of water annually, one fourth of the Beijing's urban supply, said Zhang Ping, deputy head of the Beijing water authority.

Aging of facilities and poor management mean that the quality of water from wells cannot be guaranteed in some areas, resulting in a steady stream of complaints from citizens, said Zhang.

The middle route of the gigantic south-to-north water diversion project will soon come on-stream, bringing 1 billion cubic meters to Beijing each year from a reservoir on the Hanjiang River, making possible closure of the wells.

Since 1999, Beijing has used too much groundwater: about 6.5 billion cubic meters too much. Long-term overexploitation has led to environmental problems like subsidence. The water table in parts of Beijing has dropped 12.8 meters since 1998 and more than 1,300 sq km of land has subsided over 50 centimeters.