From oasis to mirage: the aquifers that won't replenish.

• Author: Gardner, Gary
• Position: Depletion of fossil aquifers

LIKE THE PROVERBIAL CASTLES BUILT ON SAND, THE ECONOMIES OF TWO COUNTRIES - AND PART OF A THIRD - ARE BASED ON THE EXTRAVAGANT USE OF NON-RENEWABLE FOSSIL WATER. BUT POLITICAL LEADERS DON'T SEEM PARTICULARLY CONCERNED ABOUT WHAT WILL HAPPEN WHEN THE WATER IS GONE.

On August 29, 1991, Libyan leader Moammar Qaddafi secured his place in history. Standing in northern Libya beside a concrete pipe four meters in diameter - large enough to drive an 18-wheel truck through, with room to spare - he opened a valve that brought water gushing on a nine-day, 7 50 kilometer cross-country journey from the southern desert. With ceremonial flourish, he inaugurated the first phase of his Great Man-made River Project, a $25 billion plan to move massive quantities of water from southern aquifers to the populated north. The intent was to bring relief to industries and cities squeezed by water scarcity, and to make the Libyan desert bloom. Historians, Qaddafi must have reflected, would undoubtedly remember him as the leader who brought water - and prosperity - to Libya.

But Qaddafi's place in history will not likely be the one he imagined. Future generations will judge that hot August day as the moment when the Libyan economy lurched sharply in the direction of unsustainability. The world's largest civil engineering project could cost the country ten percent of its oil revenues and prompt the import of millions of farm laborers into a desert country already living beyond its natural means.

More significantly, the pipeline will chain Libya's economic future to a natural resource that is destined to disappear. The Great Man-made River is sucking from a depletable font known as a fossil aquifer - a body of water deep under the desert that is not replenished by rainfall. Formed 10,000 years ago before North Africa became a desert, the aquifer is massive, but nonrenewable. As a source of insurance water, and used sparingly, the aquifer has immense value to a desert-bound people, allowing them time to explore options for long-term survival in an arid environment. But when set as a cornerstone of the economy, the resource creates a dangerous illusion of plenty, with tragic consequences as it is depleted or becomes too contaminated for use.

Pursuit of short-term prosperity at the expense of groundwater sustainability is not unique to Libya. In Saudi Arabia and the United States, large fossil aquifers, along with renewable aquifers that are pumped beyond their rates of replenishment, have become the sinking foundations of whole regional economies. In each of these three cases, the disappearing water is being aggressively tapped for agricultural irrigation, turning arid land magically green. The story of these three fossil aquifers constitutes a kind of fable, not just about foolish behavior, but about the universal temptation to seek short-term solutions at the expense of long-term health.

GOLDEN GRAIN: THE SAUDI CASE

Like its oil, Saudi Arabia's water wealth is hidden. The country has no perennial rivers or lakes, and little rainfall. In a nation whose capital receives one-tenth the precipitation of Caracas, Chicago, or Istanbul, and where summer daytime temperatures average over 37 degrees C (100 degrees F) in the shade, it is no surprise that surviving stocks of water are found chiefly underground.

What may be surprising is the sheer volume of groundwater in this desert kingdom. Nearly 2,000 billion cubic meters of water - more than three times the volume of Lake Erie - are held in the aquifers beneath Saudi Arabia. They provide some 88 percent of the country's water - including about 80 percent of its agricultural irrigation and 50 percent of its urban supply. In villages, towns, and even small cities, virtually all the water comes from wells.

Some of these underground supplies, known as alluvial aquifers, are renewed appreciably by rainfall. But they constitute less than ten percent of the country's groundwater capacity, and their rates of replenishment are far below current levels of water use in Saudi Arabia. Renewable aquifer water, along with desalinated water and re-used wastewater, currently meet only about a third of Saudi water needs.

So the shortfall is met with "fossil" groundwater - stocks trapped during the last Ice Age, 15,000 to 30,000 years ago, in pebble-filled cavities so deep that little of today's rainfall can reach them. These enormous subterranean vessels, containing three-fourths of its total water supply, are nonrenewable.

Dependence on nonrenewable water leads, of course, to a declining water balance. With the country's water use expected to jump by more than 50 percent in the next 15 years, aquifer mining will...