"The areas in which the groundwater is highly exploited are where the pollution is most serious," Wen says. The most affected areas include northern China, the reaches of the Huaihe River, and the Yangtze and Pearl River deltas, he notes.

    According to Wen, the major culprit of the worsening groundwater pollution is industrial waste. "Some plants discharge waste without proper treatment due to the poor enforcement of environmental protection laws," he says. He adds that an increase in human activities has exacerbated the situation. "For example, gas stations have boomed in recent years, causing serious pollution to nearby soil and groundwater." Wen points to a survey that concludes that oil leakage occurs in 70 percent of gas stations in the United States, mostly from oil tanks stored underground.

    Another major source of groundwater pollution is solid waste. "A large amount of solid waste is not treated properly before it is buried," says Ma Jun, Beijing author of China's Water Crisis and a water protection campaigner.

    The overall deterioration of China's water environment has compelled the Chinese government to tackle the issue. Qiu Baoxing, vice minister of construction, said in August that the government would invest an unprecedented 125 billion U.S. dollars over the next five years to improve water treatment, recycling, and other water management to fight the mounting threat of urban water pollution.

    Wen says only a tiny proportion of the spending will be devoted to groundwater, though he notes that the funding marks the real start of China's investment in groundwater protection. In another landmark effort to tackle the problem, the government launched a large-scale survey earlier this year to investigate groundwater pollution. It is expected to be completed in five years. "The core problem is that no one knows how bad the overall situation is," Wen says. "This survey is the first systematic one on groundwater pollution to provide scientific information for policymakers."

    Legislative measures are also picking up speed. According to Wen, more revisions on groundwater protection are expected to be added to China's Water Pollution Prevention and Control Law, adopted in 1984. Experts are also calling for a real-time monitoring network on groundwater quality in key areas such as large plains, basins, populous cities, and energy bases. "Information on groundwater should be available to the public, since water pollution has been jeopardizing people's health and safety," Wen says.

    Each year, China pumps 100 billion cubic meters of groundwater, about 30 percent of the nation's annual exploitable groundwater. With merely a quarter of the world's average water resources per capita, China reports that 320 million people, about a quarter of its population, have difficulties in obtaining clean water. About 80 percent of diseases in the developing world are caused by contaminated water, according to the United Nations Environment Program.

    China's existing groundwater resources range from some 20,000 years old in the deepest aquifers to as recent as the last rainstorm, Wen says, adding that it is common to find a 1,000-year-old aquifer in Shijiazhuang or Baoding in Hebei Province near Beijing. According to Ma, the long life of an aquifer can be critical to its purity. "If polluted, surface water can soon clean itself," he explains. "But groundwater needs an unimaginable length of time to become clean. Prevention is all we can do."

    Groundwater is a strategic freshwater reserve for humans, says Wen. "In water pollution emergencies, deep groundwater plays a key role in providing drinking water for affected residents, as occurred in the aftermath of the chemical spill in the Songhua River in northeastern China last November."

    "Don't wait until the water in the well dries up to cherish the value of groundwater," Wen says. "It's imperative to prevent pollution from the outset and improve the public's awareness of fighting pollution."