Shanghai will remove all potential pollution sources, such as factories and cattle farms, from a preservation area around Shanghai's main tap-water source to prevent accidents from shutting down the water system, as has happened in a few Chinese cities over the past year.

The campaign will begin with a thorough investigation of the area, to see how much sewage is produced and how many factories, cattle and poultry farms are located in the nearly 560-square-kilometer area, according to the Shanghai Environmental Protection Bureau.

Bureau Vice Director Sun Jian said all pollution sources in the 46-square-kilometer first-class water preservation area will be shut down. The area is located on the upper reaches of the Huangpu River, which supplies about 70 percent of the city's tap water.

The city first enacted laws to protect the water source in the 1980s and then expanded the protected area in 1999, banning the discharge of sewage.

Despite the ban, several companies that are potential sources of pollution are still located in the area. Bureau officials said some companies registered as acceptable businesses, and then switched operations without reporting to authorities.

Some large factories, including chemical plants, also exist in the zone, officials said.

A bureau environmental bulletin published last year stated that water quality near the Songpu Bridge area is unsatisfactory.

Pollution from a chemical plant explosion along the Songhua River in northeastern China forced the city of Harbin to shut down its tap-water supply for five days last November.

(Xinhua News Agency April 28, 2006)