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

Chapter 6. Stabilizing Water Tables: Raising Water Productivity

To avoid a water crunch that leads to a food crunch requires a worldwide effort to raise water productivity. The tightening water situation today is similar to what the world faced with land a half-century ago. After World War II, as governments assessed the food prospect for the remainder of the century, they saw both enormous projected growth in world population and little new land to bring under the plow. In response, they joined with international development institutions in a worldwide effort to raise land productivity that was replete with commodity price supports, heavy investment in agricultural research, extension services, and farm credit agencies. The result was a rise in world grainland productivity from 1.1 tons per hectare in 1950 to 2.9 tons in 2004. 31

Today the world needs to launch a similar effort to raise water productivity. Land productivity is measured in tons of grain per hectare or bushels per acre, but there are no universally used indicators to measure and discuss water productivity. The indicator likely to emerge for irrigation water is kilograms of grain produced per ton of water. Worldwide that average is now roughly 1 kilogram of grain per ton of water used. 32

The first challenge is to raise the efficiency of irrigation water, since this accounts for 70 percent of world water use. Some data have been compiled on water irrigation efficiency at the international level for surface water projects—that is, dams that deliver water to farmers through a network of canals. Water policy analysts Sandra Postel and Amy Vickers write about a 2000 review that found that “surface water irrigation efficiency ranges between 25 and 40 percent in India, Mexico, Pakistan, the Philippines, and Thailand; between 40 and 45 percent in Malaysia and Morocco; and between 50 and 60 percent in Israel, Japan, and Taiwan.” Irrigation water efficiency is affected not only by the mode and condition of irrigation systems but also by soil type, temperature, and humidity. In arid regions with high temperatures, the evaporation of irrigation water is far higher than in humid regions with lower temperatures. 33

In a May 2004 meeting, China’s Minister of Water Resources Wang Shucheng outlined for me in some detail plans to raise China’s irrigation efficiency from 43 percent in 2000 to 51 percent in 2010 and then to 55 percent in 2030. The steps he described to boost irrigation water efficiency included raising the price of water, providing incentives for adopting more irrigation-efficient technologies, and developing the local institutions to manage this process. Reaching these goals, he said, would assure China’s future food security. 34

Crop usage of irrigation water never reaches 100 percent simply because some irrigation water evaporates from the land surface, some percolates downward, and some runs off. When attempting to raise the water efficiency of irrigation, the trend is to shift from the less efficient flood-or-furrow system to overhead sprinkler irrigation or to drip irrigation, the gold standard of irrigation water efficiency. Low-pressure sprinkler systems reduce water use by an estimated 30 percent over flood or furrow irrigation, while switching from flood or furrow to drip irrigation typically cuts water use in half. 35

As an alternative to furrow irrigation, a drip system also raises yields because it provides a steady supply of water with minimal losses to evaporation. Since drip systems are both labor-intensive and water-efficient, they are well suited to countries with underemployment and water shortages. They allow farmers to raise their water productivity by using labor, which is often in surplus in rural communities. 36

Recent data indicate that a few small countries—Cyprus, Israel, and Jordan—rely heavily on drip irrigation to water their crops. (See Table 6–3.) Among the big three agricultural producers—China, India, and the United States—the share of irrigated land using these more-efficient technologies ranges from less than 1 percent in India and China to 4 percent in the United States. 37

Low water productivity is often the result of low water prices. Current water prices are often irrationally low, belonging to an era when water was an abundant resource. As water becomes scarce, it needs to be priced accordingly. In Beijing, public hearings were held in mid-2004 on a proposal to raise water prices. At the end of July, officials announced rate hikes for urban and industrial users of some 26 percent, effective August 1. The price went from 4.01 yuan (48¢) to 5.04 yuan (61¢) per cubic meter. Other local governments in northern China, mostly at the provincial level, have been raising water prices in small increments to discourage waste. The advantage of higher prices is that it affects the decisions of all water users. Higher prices encourage investment in more water-efficient irrigation technologies, industrial processes, and household appliances. 38

In many cities in water-short parts of the world, it may be time to rethink the typical urban water use model, one where water flows into the city, is used once, and then leaves the city—usually becoming polluted in the process. This flush-and-forget model that so dominates urban water systems will not be viable over the longer term in water-scarce regions. One alternative sewage system is the use of so-called dry toilets, which do not use water and which convert human waste into a rich humus, a highly valued fertilizer.

Another variation on the existing urban water use models is one that comprehensively recycles urban water supplies. Water can be used indefinitely in cities and by industry if it is recycled. Some cities are beginning to do this. Singapore, for example, which buys its water from Malaysia, is starting to recycle its water in order to reduce this vulnerable dependence. 39

Some countries can realize large water savings by restructuring the energy sector, shifting from fossil-fuel-powered thermal plants, which require large amounts of water for cooling, to renewable energy sources, such as wind and solar. In the United States, for instance, the 48 percent of total water withdrawals that is used for thermal cooling exceeds the 34 percent withdrawn for irrigation. Most of the water used for thermal cooling is river water that returns to its source once it is used, albeit much warmer than when it was withdrawn. Although the actual water losses from evaporation in the power plant cooling towers typically amount to only 7 percent of the water that goes through the plants, the return of the hot water to the river is often ecologically damaging. 40

What is needed now is a new mindset, a new way of thinking about water use. In addition to more-efficient irrigation technologies, for example, shifting to more water-efficient crops wherever possible also boosts water productivity. Rice production is being phased out in the region around Beijing because it is so water-intensive. Similarly, Egypt restricts rice production in favor of wheat. 41

Anything that raises the productivity of irrigated land typically raises the productivity of irrigation water. Anything that increases the efficiency with which grain is converted into animal protein increases water productivity.

For people consuming excessive amounts of livestock products, moving down the food chain means not only a healthier diet and reduced health care costs, but also a reduction in water use. In the United States, where the consumption of grain as food and feed averages some 800 kilograms (four fifths of a ton) per person, a modest reduction in eating livestock products could easily cut grain use per person by 100 kilograms. Given that there are 297 million Americans, such a reduction would cut grain use by 30 million tons and the use of water to produce grain by 30 billion tons. At average world grain consumption levels of roughly 300 kilograms per person a year, 30 million tons of grain would feed 100 million people—more than enough to cover world population growth for one year. 42

Reducing water use to a level that can be sustained by aquifers and rivers worldwide involves a wide range of measures not only in agriculture but also throughout the economy. Among some of the more obvious steps are shifting to more water-efficient irrigation practices and technologies, planting more water-efficient crops, adopting more water-efficient industrial processes, and using more water-efficient household appliances. One of the less conventional steps is to shift from outdated coal-fired power plants, which require vast amounts of water for thermal cooling, to wind power—something long overdue in any case for reasons of pollution and climate disruption. Recycling urban water supplies is another obvious step to consider in countries facing acute water shortages.

The need to stabilize water tables is urgent, thanks to the sheer geographic scale of overpumping, the simultaneity of falling water tables among countries, and the accelerating drop in water level. Although falling water tables are historically a recent phenomenon, they now threaten the security of water supplies and, hence, of food supplies in countries containing 3.2 billion people. Beyond this, the shortfall—the gap between the use of water and the sustainable yield of aquifers—grows larger each year, which means the water level drop is greater than the year before. Underlying the urgency of dealing with the fast-tightening water situation is the sobering realization that not a single country has succeeded in stopping the fall in its water tables and stabilizing water levels. The fast-unfolding water crunch has not yet translated into food shortages, but if unaddressed, it may soon do so. 43

Table 6–3. Use of Drip and Micro-irrigation, Selected Countries, Circa 2000



Area Irrigated by Drip and Other Micro-irrigation Methods*

Share of Total Irrigated Area Under Drip and Micro-irrigation


(thousand hectares)












South Africa









United States



















*Micro-irrigation typically includes drip (both surface and subsurface) methods and micro-sprinklers; year of reporting varies by country.
SOURCE: See endnote 36.

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31. Grainland productivity from USDA, Production, Supply, and Distribution, op. cit. note 4; Worldwatch Institute, Signposts 2002, CD-Rom (Washington, DC: 2002).

32. Calculation based on 1,000 tons of water for 1 ton of grain from FAO, op. cit. note 1.

33. Sandra Postel and Amy Vickers, “Boosting Water Productivity,” in Worldwatch Institute, State of the World 2004 (New York: W.W. Norton & Company, 2004), pp. 51–52; Gleick, op. cit. note 2.

34. Wang Shucheng, private meeting with author, Beijing, May 2004.

35. FAO, Crops and Drops (Rome: 2002), p. 17; Alain Vidal, Aline Comeau, and Hervé Plusquellec, Case Studies on Water Conservation in the Mediterranean Region (Rome: FAO, 2001), p. vii.

36. FAO, op. cit. note 35; Vidal, Comeau, and Plusquellec, op. cit. note 35.

37. Table 6–3 from Postel and Vickers, op. cit. note 33, p. 53.

38. Peter Wonacott, “To Save Water, China Lifts Price,” Wall Street Journal, 14 June 2004.

39. Greg Leslie, “Solving Water Problem Could Come Down To Using City’s Kidneys,” Sydney Morning Herald, 19 April 2004.

40. USGS, “Estimated Water Use in the United States,” news briefing (Reston, VA: March 2004).

41. USDA, Production, Supply, and Distribution, op. cit. note 4.

42. Population from United Nations, op. cit. note 4; grain consumption from USDA, Production, Supply, and Distribution, op. cit. note 4; water calculation based on 1,000 tons of water for 1 ton of grain from FAO, op. cit. note 1.

43. United Nations, op. cit. note 4; for countries overpumping aquifers see note 4, this chapter, and Lester R. Brown, Plan B: Rescuing a Planet under Stress and a Civilization in Trouble (New York: W.W. Norton & Company, 2003), p. 26.


Copyright © 2004 Earth Policy Institute