February 14, 2003
Record-low water levels in the Yangtze caused an oil tanker to run aground and disrupted shipping in large sections of the river this week. The severe drought, along with worsening pollution in a major Yangtze tributary, raise serious concerns about the scheme launched late last year to transfer water from the region to China’s parched north.
Water levels in the Yichang, Shashi, Zhicheng and Chongqing sections of the Yangtze have fallen to their lowest since records began 100 years ago, China Daily reported yesterday [Feb. 13].
Officials who have been struggling to keep the river open for navigation were forced to suspend shipping in the Zhijiang section in Hubei province after a tanker carrying 900 tonnes of gasoline ran aground in the early hours of Feb. 11. The ship leaked more than 30 tonnes of gasoline after rocks on the riverbed tore a gash in its hull. The part of the river near Zhijiang city, 150 km downstream of the Three Gorges dam, was closed to shipping for several hours after the accident because of the danger of fire.
The water levels have been dropping since the beginning of the year “due to sparse winter rainfall and the setting aside of water for the electricity generation by the newly built Ertan hydroelectric power plant,” Xinhua news agency reported on Feb. 12. Ertan, located on the Yalong River, a Yangtze tributary, is currently China’s biggest dam and the major supplier of electricity to Sichuan province.
With the water levels expected to remain low for some time, maritime authorities are taking urgent steps to try and keep the river open, the news agency said. Officials have resorted to emergency dredging in some places, and issued a call to channel management agencies along the river to do everything possible to keep the Yangtze navigable – including blasting to deepen the channel, if necessary.
The mighty, turbulent river appeared slower and gentler than usual during the recent lunar new year holiday, the Sanxia Evening News (Sanxia wanbao) reported Feb. 9. The water level in the river channel below the Gezhouba dam, 40 kilometres downstream of the Three Gorges project, was 37.8 metres above sea level, 1.2 metres lower than required there for navigation. Many freighters had to unload cargo to make it through that section, the newspaper said.
With a smaller runoff this year than usual, the water level in the river is likely to drop even further, according to an official in charge of shipping in the Three Gorges region. In a normal year, the runoff (rain and melted snow that drains into the river rather than being absorbed by soil) is 18,000 cubic metres per second, while this year’s rate has fallen drastically to less than 3,000 cubic metres per second.
Under the south-north water transfer project, which is designed to benefit Beijing and other cities on the drought-stricken north China plain, water is to be drawn from the Yangtze and its tributaries and sent to the north along three routes. The eastern and western channels will each convey 15 billion cubic metres of water, while the middle route will draw 14.5 billion cubic metres of water from the Danjiangkou reservoir on the Han River.
However, a serious pollution problem in the Han River, one of the biggest Yangtze tributaries, could become even worse once water begins to be siphoned off, water-quality experts warn. With less water in the river, pollutants would become more concentrated and more dangerous.
An algal bloom has occurred in the river for the fourth time since 1998, the Chutian Urban Daily (Chutian dushi bao) reported Feb. 9. Water experts see this as a sign that pollution in the river is becoming worse. About 600 million tonnes of wastewater are discharged into the Han River every year, according to official statistics.
The director of the Wuhan water-quality monitoring centre told the newspaper that scientists around the world have wrestled with the problem of algal blooms and that pollution prevention is the only good solution. Keeping sewage and wastewater out of a river will help reduce the organic compounds that give rise to algal blooms, which can seriously degrade water quality and unbalance an aquatic ecosystem. The outbreaks are likely to become even more frequent, however, once the water-transfer scheme starts up and there is less water to dilute the pollutants in an already dirty river.
Meanwhile, a contributor to the Shanghai Water Affairs Journal raises another concern surrounding the south-north water-transfer project. In an article dated Jan. 24, Shen Shuwen writes that saltwater intrusion is likely to worsen in the Yangtze estuary near Shanghai as a result of the water-transfer scheme.
Drawing water from the Yangtze would reduce its flow into the East China Sea, allowing saltwater to intrude into the estuary and tributaries, and seep into the ground-water table. Salt contamination can render a water supply unfit for most purposes, including drinking and irrigation.
The problem, Mr. Shen says, is not the amount of water that will be drawn from the Yangtze and its tributaries and sent to north China, but the diversion of water during the November-April dry season. In a normal year, the Yangtze pours 960 billion cubic metres of water into the ocean, so preventing 44.5 billion cubic metres of that (about 5 per cent of the total) from entering the sea will not in itself cause much harm to the estuary, he argues.
Statistics collected at Datong in Anhui province show that 70 per cent of the Yangtze’s annual flow occurs in the May-October period, while only 30 per cent occurs in the other half of the year. It is during that dry season, with its much smaller runoff, that saltwater intrusion can become a major problem.
One of the most disastrous years was 1979, when a strong current of saltwater reached as far as the city of Nantong in Jiangsu province, 150 km from the river’s mouth. The Shanghai water supply was contaminated and agricultural production in the estuary area seriously damaged.
Mr. Shen suggests several ways to mitigate the problem of increased saltwater intrusion after the south-north water transfer begins. It might be reasonable, for instance, only to divert water during the flood season, and to draw less water – or even none at all – during the dry months, he says. And if a situation as serious as 1979 should recur, the Changjiang Water Resources Commission should have the authority to limit the amount of water drawn from the river so that flow volumes do not fall below 10,000 cubic metres per second.