中文 | English

水同位素网站片头.jpg

您当前的位置:首页 > 中文 > 新闻

Science: Water Shortages Loom as Northern China's Aquifers Are Sucked Dry

时间:2011-05-03 21:42:37  来源:Science  作者:Li Jiao

BEIJING—When Luo Yiqi visited the Inner Mongolia region of northern China 3 years ago, he was in for a surprise. In recent years, overgrazed grasslands had withered and turned to desert. Luo had been expecting that. But what stunned the ecologist from the University of Oklahoma, Norman, were the rice fields along a desiccated riverbed. Farmers were pumping water from deep aquifers to cultivate one of the thirstiest crops on the planet. “Apparently, farmers did not get enough scientific guidance,” says Luo.

Of all China's environmental woes, the biggest threat to livelihoods and food security may be looming water shortages. China's freshwater resources amount to 2220 cubic meters per person, just a quarter of the world average. For years, the central government focused on declining river flows and rising pollution, largely ignoring what has now become an acute problem: vanishing groundwater. “It was a question of ‘out of sight, out of mind,’” says environmental scientist Chen Jining, vice president of Tsinghua University here.

The outlook is especially dire on the North China Plain (NCP), an area encompassing six provinces and the Beijing and Tianjin metropolitan areas. Over the past 40 years, NCP's water table has fallen steadily as some 120 billion cubic meters more water has been pumped from the land than the amount replaced by rainfall, says Liu Changming, a hydrologist at the Institute of Geographical Science and Natural Resource Research of the Chinese Academy of Sciences (CAS) here. Many wells are expected to run dry in the coming decades; when this happens, warns Lester Brown, president of the Earth Policy Institute in Washington, D.C., “China will lose the ability to feed about 10% of its 1.3 billion people.”

Until recently, the government was banking on a massive engineering solution. The $75 billion South-to-North Water Diversion Project, now under construction, would bring water from the Yangtze basin to the parched north (Science, 25 August 2006, p. 1034). But that remedy is no longer deemed sufficient. “Faced with an escalating crisis, the government is calling for stepped-up monitoring and scientific advice on groundwater management,” says Liu. This year, the Ministry of Science and Technology launched a $4.4 million, 5-year project to better understand China's subterranean water resources. The project “is the latest sign of the government's changing attitude,” says Pang Zhonghe, a hydrogeologist at CAS's Institute of Geology and Geophysics here. An even bigger effort should get under way soon: a $250 million initiative to drill scientific observation wells to monitor groundwater levels and quality.

China has largely brought its water problems on itself. The classic novel Outlaws of the Marsh, written more than 600 years ago, describes the reedy wetlands of the Haihe River Basin, NCP's northern section. The fertile region has been a major target of development; augmenting water drawn from rivers, NCP went from 1800 powered wells in the 1960s to more than 700,000 such wells by 2000, says Liu. The Water Rush paid big dividends, such as turning NCP into the country's wheat and corn belts, says Liang Shunlin, a geographer at the University of Maryland, College Park, and Beijing Normal University.

Across the Haihe Basin, each year about 50% more shallow groundwater is consumed than recharged by rainfall. And the surfeit of wells is exhausting deeper phreatic water in the saturated zone that takes much longer to replenish. As NCP is sucked dry, it is shriveling and fissuring, and subsidence now averages more than 1 meter. A few years ago, Liu's team, using radiocarbon dating, found to its astonishment that phreatic water now being drawn from NCP is as much as 30,000 years old. It would take that long, Liu says, to replenish the deep aquifer.

To save water and maintain food security, researchers have proposed improved water conservation, better water pricing policies, and rational agricultural practices. Growing crops and raising livestock account for nearly 66% of China's total water consumption, Liu says. Water-saving measures in agriculture that could be implemented right away include drip and sprinkler irrigation and no-till farming, which reduces evaporation, says Xiao Xiangming, a landscape ecologist at the University of Oklahoma, Norman. Liang adds that researchers should strive to develop crops that lose less water to evaporation and better resist drought.

The south-north diversion may provide temporary relief when the central and eastern lines are completed in 2014. “We can store some of the transferred water underground and take it when we need it,” says Qian Yi, a professor in the Department of Environmental Science and Engineering at Tsinghua University. But any water from the diversion project should be viewed as a “supplementary” resource, Liu says: “The first step is to use local water efficiently.”

A comprehensive solution may depend on better information. Reliable data on aquifer storage, recharge, and water use are notoriously difficult to obtain, says Li Wenpeng, chief engineer at the China Institute of Geological Environmental Monitoring here. For a half-century, the government has relied heavily on data from nonstandardized farmers' wells. To address this shortcoming, the land and water ministries have devised a project, now in final review and expected to start this year, in which more than 20,000 monitoring wells would be drilled across the country, with a focus on northern regions. Each well would track water level, temperature, and water quality, and more than half would also test for pollutants and other contaminants. Remote sensing could augment this effort, Liang says.

“It is time to take action,” says Yuan Daoxian, a hydrogeologist at the Institute of Karst Geology in Guilin, China. Unless the government acts quickly to rein in groundwater consumption, Liu adds, “the problem will be impossible to solve.”

原文链接

来顶一下
返回首页
返回首页
推荐信息
庞忠和课题组参加第14届国际水岩相互作用大会
庞忠和课题组参加第14
IAEA资深专家访我所赞同位素水文地质进步
IAEA资深专家访我所赞
美国Donald J. DePaolo教授访问我所
美国Donald J. DePaol
我实验室开展同位素水文学野外教学实习活动
我实验室开展同位素水
相关文章
    无相关信息
栏目更新
栏目热门