The second salt tide of this summer ebbed away last night but the third one is predicted to hit Shanghai by next Tuesday, water authorities revealed yesterday.

 

Officials are not sure how long the third salt tide will last, or whether it will affect Shanghai's tap water supply.

 

The Chenhang Reservoir near the Yangtze River estuary will begin storing fresh water today to prepare for the worst.

 

The reservoir has a capacity of 8.3 million tons and can supply fresh water for five days.

 

Meanwhile, Shanghai has launched a 24-hour monitoring system for the upper reaches of the Yangtze River.

 

During the second salt tide period, northern parts of Shanghai, including Baoshan, Zhabei and Putuo districts and part of Pudong reportedly suffered from low water pressure and the tap water had a salty taste.

 

"The water won't affect people's health in the short term," said Zhao Guotong, a member of the Shanghai Association for Environment Protection Industry.

 

"Residents in northern parts of the city can also choose to drink purified water during the salt tide period for better quality," Zhao said.

 

The output of tap water from five water plants was reduced last week due to the salt tide. The Yuepu Water Plant in Baoshan District, the nearest one to the mouth of the Yangtze River, witnessed a daily drop of about 100,000 tons of tap water last week.

 

"Since the chloride level exceeded the national standard, the amount of raw water was reduced, which led to the drop in the tap water output," said a technician with the plant.

 

The national standard is 250 milligrams per liter.

 

Normally, salt tides take place at the mouth of the Yangtze River in winter or early spring, when water flow in the river decreases, causing chloride levels to rise.

 

But Shanghai was stricken by the first summer salt tide on Sep. 11 and the second one on Oct. 9.

 

(Shanghai Daily October 18, 2006)