The Pearl River Water Commission under the Ministry of Water Resources will initiate a co-ordinated water diversion programme in the upper reaches of the Xijiang, to minimize the impact of possible salt tides in the delta later this year and early next year.
"From the meteorological and ecological analysis, and the regular rainfall pattern in the Pearl River Delta region during low water periods over the past few years, we consider it very likely that salt tides will hit the delta region again later this winter and early next spring," said Wang Qiusheng, deputy director of the Pearl River Water Commission.
"We have recently gained permission from the State for a water diversion programme in the upper reaches of the Xijiang River, a tributary of the Pearl River.
"We plan to sluice the reservoir water in the upper reaches three or four times to make up for the low water in the lower reaches of the Xijiang River in December, ensuring water supplies for Zhuhai and Macao," he said.
The Pearl River Delta has suffered from salt tides during low water periods over the past few years, with Zhuhai and Macao bearing the brunt of the shortages.
Wang said the commission will adjust the water diversion program next January, in accordance with rainfall in the region.
"The water diversion program is a systematic one," he said. "We can not neglect the water needed for navigation, power generation and other purposes in the lower reaches as we store water in the upper reaches."
Wang said water storage work had begun at the end of September at the Longtan Hydropower Plant, China's second largest hydropower project, located in South China's Guangxi Zhuang Autonomous Region. He said the commission was pleased with the work so far.
But Liu Jinluan, deputy director of the Guangzhou Climate and Agricultural Meteorology Centre, said the water diversion program was only a makeshift measure.
"Comprehensive measures including water saving and recycling, as well as planting forests along the upper reaches of the Xijiang River should be taken to curb future salt tides," said Liu.
Meanwhile in Shanghai, a second wave of salt tides that have plagued water supplies in the city's northern part, threatening the drinking water of more than 4.4 million people, is hoped to end this morning, thanks to a low tide.
No water use restrictions have been in place as the impact of the salt tide was not out of control, the government said.
According to data collected from various monitoring sites, the content of chlorine hydronium the main salt element in salt water is decreasing in the water collected from the mouth of the Yangtze, which accounts for roughly 30 percent of Shanghai's water supply.
"The content of chlorine chemicals in the water has fallen from more than 1,000 milligrams per litre days ago to 400 to 500," a senior official with the Shanghai Municipal Water Supply Dispatching and Monitoring Centre said yesterday.
The trend indicates the salt content will keep falling, said the official, as the falling tide will drop to one of its two monthly lows today.
Residents dwelling in the Baoshan, Zhabei and Pudong New Area districts have had insufficient tap water during certain hours over the past few days, and the water has tasted salty since the tide started on October 9.
The other 70 per cent of Shanghai's water supplies come from the upper reaches of the Huangpu River, a major tributary on the lower part of the Yangtze River which is usually not threatened by salt tides.
To help eradicate the problem, "the municipal government has speeded up the construction of two major reservoirs," the official said.
The projects are expected to be completed in 2010.
(China Daily October 17, 2006)