Society

New reservoir to keep Shanghai in fresh water

By He Wei (China Daily)
Updated: 2011-05-26 09:12

SHANGHAI - The city's tap water supply will not be undermined by the lingering drought and the consequent intrusion of saltwater, a local official from the water authority has said.

The government is poised to provide quality drinking water "thanks to the newly established Qingcaosha Reservoir," Meng Mingqun, head of the water provision department of the Shanghai water authority, said at a press briefing on Wednesday.

Water levels fell to a near-record low in May, Meng said, with the average water flow of the Yangtze River's downstream a mere 18,000 cubic meters per second, compared to 32,000 in the same stretch during normal years.

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"We are way behind average totals for rainfall this year, and that causes saltwater intrusion, which is a rare occurrence in May," Meng told China Daily.

Saltwater intrusion is the movement of saline water into freshwater aquifers, Meng noted. It usually occurs in winter and early spring, and is caused by natural disasters such as drought or a storm surge from a hurricane.

The drought has depleted water supplies at Shanghai's Chenhang Reservoir, which is plagued by saltwater intrusion for the seventh time this year.

As a major water source to the northern part of the city, the reservoir is set to provide water to five waterworks in the area, but the current storage can barely meet the weekly demand, according to Shen Yichen, general manager of Shanghai Chengtou Raw Water Co Ltd.

"The saltwater intrusion has dealt a heavy blow to our water reserve in Chenhang. It is essential that Qingcaosha Reservoir take over to combat current water shortages," Shen said.

The Qingcaosha Reservoir, less exposed to the contamination, went into operation last December on a trial basis in a bid to improve the city's water infrastructure as well as diversify its water supply.

By building this 70-sq-km reservoir, the city pledged to source up to 70 percent of its tap water from the Yangtze River by 2012 in an attempt to loosen its dependence on the once-polluted Huangpu River.

With a capacity of 430 million cubic meters, Qingcaosha is designed to provide 68 days of water without refilling from the Yangtze River.

The current water shortage has hastened the pace of Qingcaosha replacing Chenhang as the primary water source, according to Zhao Pingwei, who oversees water quality inspection within the authority.

"The daily supply volume of Chenhang has dropped from 1.8 million cu m to 1.2 million by late April, and all central districts are expected to have access to water from the Qingcaosha Reservoir within two weeks," Zhao said.

The concentration of chloride near the Chenhang Reservoir has fallen to 523 milligrams per liter from its peak of 676 on Monday. The warning level is 250.