Groundwater woes

Posted: 1 March 2001

Toxic chemicals are contaminating groundwater on every inhabited continent, endangering the world's most valuable supplies of freshwater, reports a new study from the Washington-based Worldwatch Institute.

This first global survey of groundwater pollution shows that a toxic brew of pesticides, nitrogen fertilizers, industrial chemicals, and heavy metals is fouling groundwater everywhere, and that the damage is often worst in the very places where people most need water.

"Groundwater contamination is an irreversible act that will deprive future generations of one of life's basic resources," said Payal Sampat, author of Deep Trouble: The Hidden Threat of Groundwater Pollution. "In the next 50 years, an additional 3 billion people are expected to inhabit the Earth, creating even more demand for water for drinking, irrigation, and industry. But we're polluting our cheapest and most easily accessible supply of water. Most groundwater is still pristine, but unless we take immediate action, clean groundwater will not be there when we need it."

Drinking water

Some 97 per cent of the planet's liquid freshwater is stored in underground aquifers. Nearly one-third of all humanity relies almost exclusively on groundwater for drinking, including the residents of some of the largest cities in the developing world, such as Jakarta, Dhaka, Lima, and Mexico City. Almost 99 per cent of the rural US population, and 80 per cent of India's villagers, depend on groundwater for drinking.

Groundwater irrigates some of the world's most productive cropland. More than half of irrigated farmland in India, and 43 per cent in the United States, are watered by groundwater. Irrigation already accounts for about two-thirds of water use worldwide. As rivers and lakes are dammed, dried up, or polluted, and as food demand grows in the next 50 years, farmers will become increasingly dependent on groundwater for irrigation.

Groundwater contamination is already widespread from high levels of pesticides in wells in California's San Joaquin Valley to excessive nitrates in groundwater in 4 northern Chinese provinces.

"One of the most disturbing aspects of the problem is that groundwater pollution is essentially permanent," said Sampat. Water recycles extremely slowly underground, too slowly to flush out or dilute toxic chemicals. Water that enters an aquifer remains there for an average of 1,400 years, compared to only 16 days for rivers. Thus Londoners, for example, may be drinking water that fell as rain as long ago as the last Ice Age.

Polluting industries

The report calls for a reduction of the polluting processes from the manufacturing and agricultural sectors to prevent groundwater pollution and cites a number of possible examples:

  • Since 1998, all the farmers in China's Yunnan Province have eliminated their use of fungicides, while doubling rice yields, by planting more diverse varieties of the grain.
  • Several water utilities in Germany now pay farmers to switch to organic operations because it costs less than removing farm chemicals from water supplies.
  • Companies are building "industrial symbiosis" parks in which the unusable wastes from one firm become the input for another. Such waste exchanges help an industrial park in Kalundborg, Denmark, to keep more than 1.3 million tons of effluent out of landfills and septic systems each year.
  • Manufacturers can also switch to less toxic alternatives. In Sweden, where chlorinated solvents are being entirely phased out by the end of 2000, some firms already report economic savings from switching to water-based solvents derived from biochemical sources such as citrus fruits, corn, soybeans, and lactic acid.
Sampat calls on governments to encourage reductions or replacement of toxic chemicals. Pollution taxes in the Netherlands, for example, have helped the country slash discharges of heavy metals such as mercury and arsenic into waterways by up to 99 per cent between 1976 and the mid-1990s.

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