On March 16, 2003, some 10,000 participants will meet in Japan for the third World Water Forum to discuss the world water prospect. Although they will be officially focusing on water scarcity, they will indirectly be focusing on food scarcity because 70 percent of the water we divert from rivers or pump from underground is used for irrigation.

As world water demand has tripled over the last half-century, it has exceeded the sustainable yield of aquifers in scores of countries, leading to falling water tables. In effect, governments are satisfying the growing demand for food by overpumping groundwater, a measure that virtually assures a drop in food production when the aquifer is depleted. Knowingly or not, governments are creating a "food bubble" economy.

As water use climbs, the world is incurring a vast water deficit, one that is largely invisible, historically recent, and growing fast. Because the impending water crunch typically takes the form of falling water tables, it is not visible. Falling water tables are often discovered only when wells go dry.

Once the growing demand for water rises above the sustainable yield of an aquifer, the gap between the two widens each year. The first year after the line is crossed, the water table falls very little, with the drop often being scarcely perceptible. Each year thereafter, however, the annual drop is larger than the year before.

The diesel-driven or electrically powered pumps that make overpumping possible have become available throughout the entire world at essentially the same time. The near-simultaneous depletion of aquifers means that cutbacks in grain harvests will be occurring in many countries at more or less the same time. And they will be occurring at a time when world population is growing by more than 70 million a year.

Aquifers are being depleted in scores of countries, including China, India, and the United States, which collectively account for half of the world grain harvest. Under the North China Plain, which produces more than half of China's wheat and a third of its corn, the annual drop in the water table has increased from an average of 1.5 meters a decade ago to up to 3 meters today. Overpumping has largely depleted the shallow aquifer, so the amount of water that can be pumped from it each year is restricted to the annual recharge from precipitation. This is forcing well drillers to go down to the region's deep aquifer, which, unfortunately, is not replenishable.

He Quincheng, head of the Geological Environmental Monitoring Institute in Beijing, notes that as the deep aquifer under the North China Plain is depleted, the region is losing its last water reserve—its only safety cushion. His concerns are mirrored in a World Bank report: "Anecdotal evidence suggest that deep wells [drilled] around Beijing now have to reach 1,000 meters [more than half a mile] to tap fresh water, adding dramatically to the cost of supply." In unusually strong language for the Bank, the report forecasts "catastrophic consequences for future generations" unless water use and supply can quickly be brought back into balance.

India, which now has a billion people, is overdrawing aquifers in several states, including the Punjab (the country's breadbasket), Haryana, Gujarat, Rajasthan, Andhra Pradesh, and Tamil Nadu. The latest data indicate that under the Punjab and Haryana, water tables are falling by up to 1 meter per year. David Seckler, former head of the International Water Management Institute, estimates that aquifer depletion could reduce India's grain harvest by one fifth.

In the United States, the underground water table has dropped by more than 30 meters (100 feet) in parts of Texas, Oklahoma, and Kansas—three key grain-producing states. As a result, wells have gone dry on thousands of farms in the southern Great Plains.

Pakistan, a country with 140 million people and still growing by 4 million per year, is also overpumping its aquifers. In the Pakistani part of the fertile Punjab plain, the drop in the water table appears to be similar to that in India. In the province of Baluchistan, a more arid region, the water table around the provincial capital of Quetta is falling by 3.5 meters per year. Richard Garstang, a water expert with the World Wildlife Fund, says that "within 15 years Quetta will run out of water if the current consumption rate continues."

In Yemen, the water table is falling by roughly 2 meters a year. In its search for relief, the Yemeni government has drilled test wells in the Sana'a basin, where the capital is located, that are 2 kilometers (1.2 miles) deep—depths normally associated with the oil industry—yet it has failed to find water. With a population of 19 million growing at 3.3 percent a year, one of the highest rates in the world, and with water tables falling everywhere, Yemen is fast becoming a hydrological basket case. 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 Mexico—home to a population of 104 million that is projected to reach 150 million by 2050—the demand for water is outstripping supply. In the agricultural state of Guanajuato, for example, the water table is falling by 2 meters or more a year. At the national level, 52 percent of all the water extracted from underground is coming from aquifers that are being overpumped.

Water scarcity, once a local issue, is now crossing international boundaries via the international grain trade. Because it takes a thousand tons of water to produce a ton of grain, importing grain is the most efficient way to import water. Countries that are pressing against the limits of their water supply typically satisfy the growing need of cities and industry by diverting irrigation water from agriculture, and then they import grain to offset the loss of productive capacity. As water shortages intensify, so too will the competition for grain in world markets. In a sense, trading in grain futures is the same as trading in water futures.

In China, a combination of aquifer depletion, the diversion of irrigation water to cities, and lower grain support prices are shrinking the grain harvest. After peaking at 392 million tons in 1998, the harvest dropped to 346 million tons in 2002. China's food bubble may be about to burst. It has covered its grain shortfall for three years by drawing down its stocks, but it will soon have to turn to the world market to fill this deficit. When it does, it could destabilize world grain markets.

Although some countries have already made impressive gains in raising irrigation efficiency and recycling urban wastewater, the general response to water scarcity has been to build more dams or drill more wells. But now expanding supply is becoming more difficult. The only other option is to reduce demand by stabilizing population and raising water productivity. With nearly all the 3 billion people to be added by 2050 being born in developing countries where water is already scarce, achieving an acceptable balance between water and people may now depend more on stabilizing population than on any other single action.

The second step in stabilizing the water situation is to raise water productivity, not unlike the way we have raised land productivity. After World War II, with population projected to double by 2000 and with little new land to bring under the plow, the world launched a major effort to raise cropland productivity. As a result, land productivity nearly tripled between 1950 and 2000. Now it is time to see what we can do with water.

Copyright © 2003 Earth Policy Institute