Outgrowing the Earth: The Food Security Challenge in an Age of Falling Water Tables and Rising Temperatures


Lester R. Brown

Chapter 6. Stabilizing Water Tables: Falling Water Tables

Over much of the earth, the demand for water exceeds the sustainable yield of aquifers and rivers. The gap between the continuously growing use of water and the sustainable supply is widening each year, making it more and more difficult to support rapid growth in food production. 3

With river water in key farming regions rather fully exploited, the world has turned to underground water sources in recent decades to keep expanding the irrigated area. As a result, the climbing demand for water has now exceeded the natural recharge of many aquifers. Now water tables are falling in scores of countries that contain more than half the world’s people. (See Table 6–1.) These include China, India, and the United States, which together account for nearly half of the global grain harvest. And as the gap between steadily rising demand and the sustainable yield of aquifers grows, water tables are falling at an accelerating rate. 4

In the United States, water tables are falling under the Great Plains and throughout the southwest. In India, they are falling in most states—including the Punjab, the nation’s breadbasket. This country of more than 1 billion people depends on underground water supplies for well over half of its irrigation water, with the remainder coming from rivers. In China, water tables are falling throughout the northern half of the country, including under the North China Plain, the source of half of the nation’s wheat and a third of its corn. 5

The effects of aquifer depletion vary, depending on whether it is a replenishable or fossil aquifer. If the aquifer is replenishable, as most are, once depletion occurs the water pumped is necessarily reduced to the amount of recharge. If, for example, an aquifer is being pumped at twice the rate of recharge, depletion means the rate of pumping will be cut in half. In a fossil, or nonreplenishable aquifer, however, depletion means the end of pumping. Fossil aquifers include the Ogallala under the U.S. Great Plains, the aquifer the Saudis use to irrigate wheat, and the deeper of the two aquifers under the North China Plain. 6

In some countries, falling water tables and the depletion of aquifers are already reducing the grain harvest. In Saudi Arabia, the wheat harvest peaked in 1992 at 4.1 million tons, and then declined to 1.6 million tons in 2004—a drop of 61 percent. (See Figure 6–1.) Some other smaller countries, such as Yemen, have also experienced grain harvest declines. 7

For the first time, diminishing supplies of irrigation water are helping to shrink the grain harvest in a large grain producer—China. The wheat harvest, which peaked at 123 million tons in 1997, dropped to 90 million tons in 2004—a decline of 27 percent. The production of wheat has dropped much more than that of corn and rice because wheat is grown largely in the semiarid northern half of the country, where water is scarce. 8

Serious though emerging water shortages are in China, the problem may be even more serious in India simply because the margin between actual food consumption and survival is so precarious. In a recent survey of India’s water situation, Fred Pearce in the New Scientist notes that the 21 million wells drilled in this global epicenter of well-drilling are lowering water tables in most of the country. The wells, powered by heavily subsidized electricity, are dropping water tables at an accelerating rate. In North Gujarat, the water table is falling by 6 meters or 20 feet per year. In some states, half of all electricity is now used to pump water. 9

In Tamil Nadu, a state of 62 million people in southern India, falling water tables are drying up wells. Kuppannan Palanisami of Tamil Nadu Agricultural University says that falling water tables have dried up 95 percent of the wells owned by small farmers, reducing the irrigated area in the state by half over the last decade. 10

As water tables fall, well drillers are using modified oil-drilling technology to reach water, drilling as deep as 1,000 meters in some locations. In communities where underground water sources have dried up entirely, all agriculture is rain-fed and drinking water is trucked in. Tushaar Shah, who heads the International Water Management Institute’s groundwater station in Gujarat, says of India, “When the balloon bursts, untold anarchy will be the lot of rural India.” 11

In Mexico, water tables are falling throughout the more arid north. As this happens, the energy required to pump water rises. Indeed, more than 6 percent of Mexico’s electricity is used to pump water. 12

In the United States, the loss of irrigation water is making it more difficult for farmers to respond to the future import needs of other countries. In the southern Great Plains, for example, the irrigated area has shrunk by 24 percent since 1980. Leading agricultural states such as Texas, Oklahoma, and Kansas are among those most affected by falling water tables. 13

In a rational world, falling water tables would trigger alarm, setting in motion a series of government actions to reduce demand and reestablish a stable balance with the sustainable supply. Unfortunately, not a single government appears to have done this. Official responses to falling water tables have been consistently belated and grossly inadequate.

Table 6-1. Underground Water Depletion in Key Countries





In Mexico, where a third of all water used comes from underground, aquifers are being depleted throughout the northern arid and semiarid regions. In a country where irrigated land is more than three times as productive as rain-fed land, the loss of irrigation water from aquifer depletion will be costly.

United States

Overpumping is widespread, and the overpumping of the vast Ogallala or High Plains aquifer—essentially a fossil aquifer that extends from southern South Dakota through Nebraska, Kansas, eastern Colorado, Oklahoma, and Texas—is a matter of national concern. In the Southern Great Plains, irrigated area has shrunk by 24 percent since 1980 as wells have gone dry.

Saudi Arabia

When the Saudis turned to their large fossil aquifer for irrigation, wheat production climbed from 140,000 tons in 1980 to 4.1 million tons in 1992. But with rapid depletion of the aquifer, production dropped to 1.6 million tons in 2004. It is only a matter of time until irrigated wheat production ends.


The overpumping of aquifers is estimated at 5 billion tons per year. When aquifers are depleted, Iran’s grain harvest could drop by 5 million tons, or one third of the current harvest.


This country of 21 million people is unique in that it has both one of the world’s fastest-growing populations and the fastest-falling water tables. The World Bank reports that the water table is falling by 2 meters or more a year in most of Yemen.


Both the coastal aquifer and the mountain aquifer Israel shares with Palestinians are being depleted. With severe water shortages leading to a ban on irrigated wheat, the continuous tightening of water supplies is likely to further raise tensions in this region.


Water tables are falling in most states in India, including the Punjab and Haryana, the leading grain-surplus states. With thousands of irrigation wells going dry each year, India’s farmers are finding it increasingly difficult to feed the 18 million people added each year.


Water tables are falling throughout northern China, including under the North China Plain. China’s harvest of wheat has fallen in recent years as irrigation wells have dried up. From 2002 to 2004, China went from being essentially self-sufficient in wheat to being the world’s largest importer.



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