The world is incurring a vast water deficit. It is largely invisible, historically recent, and growing fast. Because this impending crisis typically takes the form of aquifer overpumping and falling water tables, it is not visible. Unlike burning forests or invading sand dunes, falling water tables cannot be readily photographed. They are often discovered only when wells go dry.

The world water deficit is recent--a product of the tripling of water demand over the last half-century and the rapid worldwide spread of powerful diesel and electrically driven pumps. The drilling of millions of wells has pushed water withdrawals beyond the recharge of many aquifers. The failure of governments to limit pumping to the sustainable yield of aquifers means that water tables are now falling in scores of countries.

We are consuming water that belongs to future generations. In some countries, the fall of water tables is dramatic. In Yemen, a country of 19 million, the water table under most of the country is falling by roughly 2 meters a year as water use far exceeds the sustainable yield of aquifers. World Bank official Christopher Ward observes that "groundwater is being mined at such a rate that parts of the rural economy could disappear within a generation."

In the basin where the capital, Sana'a, is located and where the water table is falling 6 meters (nearly 20 feet) per year, the aquifer will be depleted by the end of this decade. In the search for water, the Yemeni government has drilled test wells in the basin that are 2 kilometers (1.2 miles) deep, depths normally associated with the oil industry, but they have failed to find water. Yemen must soon decide whether to bring water to Sana'a, possibly from coastal desalting plants, or to relocate the capital.

Iran, a country of 70 million people, is facing an acute shortage of water. Under the agriculturally rich Chenaran Plain in northeastern Iran, the water table was falling by 2.8 meters a year in the late 1990s. But in 2001 the cumulative effect of a three-year drought and the new wells being drilled both for irrigation and to supply the nearby city of Mashad dropped the aquifer by an extraordinary 8 meters. Villages in eastern Iran are being abandoned as wells go dry, generating a swelling flow of water refugees.

Shortages of water in Egypt, which is entirely dependent on the Nile River, are well known. With the Nile now reduced to a trickle as it enters the Mediterranean, the three principal countries of the Nile River Basin--Egypt, Ethiopia, and Sudan--can each increase its take from the river only at the expense of the other two. With the combined population of these countries projected to climb from 167 million today to 264 million in 2025, all three are facing growing grain deficits as a result of water shortages.

In Mexico--home to 104 million people and growing by 2 million per year--the demand for water has outstripped supply in many states. In the agricultural state of Guanajuato, for example, the water table is falling by 1.8-3.3 meters a year. Mexico City's water problems are legendary. How the United States and Mexico share the water of the Rio Grande has become a thorny issue in U.S.-Mexican relations.

A World Bank study of the water balance in the North China Plain calculated an annual deficit of 37 billion tons of water. Using the rule of thumb of 1,000 tons of water to produce 1 ton of grain, this is equal to 37 million tons of grain--enough to feed 111 million Chinese at their current level of consumption. In effect, 111 million Chinese are being fed with grain produced with water that belongs to their children. Scores of other countries are running up regional water deficits, including nearly all of those in Central Asia, the Middle East, and North Africa, plus India, Pakistan, and the United States.

Historically, water shortages were local, but in an increasingly integrated world economy, the shortfalls can cross national boundaries via the international grain trade. Water-scarce countries often satisfy the growing needs of cities and industry by diverting water from irrigation and importing grain to offset the resulting loss of production. Since a ton of grain equals 1,000 tons of water, importing grain is the most efficient way to import water. World grain futures will soon in effect become world water futures.

Although military conflicts over water are always a possibility, future competition for water seems more likely to take place in world grain markets. This can be seen with Iran and Egypt, both of which now import more wheat than Japan, traditionally the world's leading importer. Imports supply 40 percent or more of the total consumption of grain--wheat, rice, and feedgrains--in both countries. Numerous other water-short countries also import much of their grain. Morocco brings in half of its grain. For Algeria and Saudi Arabia, the figure is over 70 percent. Yemen imports nearly 80 percent of its grain, and Israel, more than 90 percent.

Seventy percent of world water use, including all the water diverted from rivers and pumped from underground, is used for irrigation, 20 percent is used by industry, and 10 percent goes to residences. Thus if the world is facing a water shortage, it is also facing a food shortage. Water deficits, which are already spurring heavy grain imports in numerous smaller countries, may soon do the same in larger countries, such as China or India.

Even with the overpumping of its aquifers, China is developing a grain deficit. After rising to an historical peak of 392 million tons in 1998, grain production in the world's largest nation fell below 350 million tons in 2000, 2001, and 2002. The resulting annual deficits of 40 million tons or so have been filled by drawing down the country's extensive grain reserves. But if this situation continues, China soon will be forced to turn to the world grain market.

When this happens, it will almost certainly drive grain prices upward. Remember that when the Soviets decided after a poor harvest in 1972 to import grain rather than tighten their belts, the world wheat price climbed from $1.90 per bushel in 1972 to $4.89 in 1974.

The two keys to stabilizing aquifers are raising water prices and stabilizing population. The first step is to eliminate the pervasive subsidies that create artificially low prices for water in so many countries. The next is to raise water prices to the point where they will reduce pumping to a sustainable level by raising water productivity and reducing water use in all segments of society. Low-income urban consumers can be protected with "lifeline rates" that provide for basic needs at an affordable price. Prices of underground water can be raised by installing meters on pumps and charging for water as Mexico has done or by auctioning permits to operate wells. Either way, water prices rise.

The second key is to quickly stabilize population in water-short countries. Most of the 3 billion people projected to be added worldwide by mid-century will be born in countries already experiencing water shortages. Unless population growth can be slowed quickly by investing heavily in female literacy and family planning services, there may not be a humane solution to the emerging world water shortage.

Copyright © 2002 Earth Policy Institute