Dams and Fish

Water fears as salt tide kills river fish

Chen Qian and Ning Bo, Shanghai Daily

October 25, 2006

The third salt tide to hit Shanghai in six weeks killed fish in two of Pudong’s main rivers, district water authorities said yesterday. And water experts warned of possible water shortages this winter.

Pudong water management office said the fish in the Zhangjiabang and Chuanyang rivers died because the salt tide increased chloride levels in the water. The office said higher pollution levels brought on by a decrease in fresh water flow in the city’s rivers were also to blame.

The upper reaches of the Yangtze River suffered a serious drought this summer, dropping water levels to a record low and bringing early salt tides to the city. Salt tides normally arrive in winter or early spring, when the decreased water flow is unable to hold back sea water from the East China Sea.

Chloride levels yesterday afternoon stood at 360 parts per million compared with normal tap water levels of 250ppm. Water suppliers said the latest salt tide had not yet affected supply but added that chlorine levels were expected to rise at the mouth of the Yangtze River – one of the city’s two main water sources – over the next five to six days.

“However, we expect it to be less severe than the second salt tide,” said Sheng Daisun, head of the Yangtze River Fresh Water Plant, which supplies about 1.3 million cubic meters of fresh water to five water plants in northern Shanghai. The second salt tide hit on October 9, lowering water pressure and affecting taste. Yuepu Water Plant in Baoshan District, the nearest plant to the mouth of the Yangtze River, said its tap-water output remained normal yesterday.

“We had a tap-water output of 300,000 cubic meters yesterday, the same as in the past few days,” said a plant technician surnamed Chen. He said the salt tide would not affect the plant’s supplies over the next few days because it had enough water in storage. “But that will change if the salt tide lasts a long time,” Chen said. Some water experts are worried the city will suffer water shortages this winter because of the drought. He Qing, a professor with Shanghai East China Normal University, said researchers from his university had compiled some startling data.

“October is a high water season,” He said.”But our research shows that the amount of water in the Yangtze River is down to the levels of the low season. “If the Yangtze River remains low, Shanghai may face a shortage of usable tap water.” Shanghai Water Authority said domestic water supply would not be cut, and the construction of new water plants would help cushion the effect of salt tides in the future.

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