Page 90) Irrigation Water: Trillions of  Gallons Wasted


American farmers irrigate about 56 million acres of land, or 88,000 square miles. Some 23 million of those acres - an area the size of Indiana - are devoted to crops destined to feed livestock.


The most frequently irrigated crops are corn (some is also used to produce ethanol fuel) and hay, with another 4 to 5 million acres each being planted in soybeans; sorghum, barley, and wheat; and cotton (cottonseed meal is used as livestock feed). In stark contrast, vegetables, vineyards, and fruits and nut tree orchards together occupy only 7 million acres of irrigated land.


The amount of water devoted to irrigating alfalfa and other hay - 7 trillion gallons annually - exceeds the irrigation needs of all vegetables, berries, and fruit orchards combined.


Of the roughly 28 trillion gallons of water used for irrigation each year, about 14 trillion gallons are applied to the grains, oilseeds, pasture, and hay that are fed to livestock in the United States, and an additional 3 trillion gallons are used to produce grains for food export or export.


Irrigation Methods Are Often Inefficient


Efficient irrigation methods could help preserve scarce water supplies, but about half of the irrigated acres in the United States use wasteful systems. The least efficient ones either run water down furrows (trenches) or simply flood fields. Roughly 45 percent of irrigated acres rely on more efficient systems, such as center - pivot sprinkler irrigation (creating those large circles that can be seen when flying over Nebraska and other Great Plains states).


But only 4 percent use highly efficient low - flow systems, such as drip irrigation. Though more expensive than flooding systems, drip irrigation can reduce water use by 30 to 70 percent and increase crop yields by 20 to 90 percent. Adopting better conservation practices and more efficient technologies, which many farmers are now doing, could save tremendous amounts of water.


The timing, as well as the method, of irrigation can waste water and result in "waterlogging, increased sol salinity, erosion, and surface and groundwater quality problems associated with nutrients, pesticides, and pathogens," according to the US. Department of Agriculture (USDA).


In 2003, only 8 percent of farmers who irrigated their crops measured the moisture content of their plants or soil before irrigating. University of California at Berkeley researchers found that the use of computer models enabled farmers to use 13 percent less water and increase crop yields by 8 percent.


Page 91) Irrigation may Be a Bad Investment


Irrigated crops account for about half of all crop sales in the United States, even though they are harvested from only one - sixth of all cropland. Using irrigation to increase yields means that less land is required to meet the same production goals. (it may also contribute to over - production).


In the case of feed crops, the USDA estimates that 100 gallons of irrigation water generates only a few cents in increased farm revenue - hardly a great bargain. The same water could be used for more lucrative purposes. For example, an irrigated acre of corn yields about 163 bushels, which in 2002 was worth about $383. In contrast, 1 irrigated acre could produce about $2,400 worth of potatoes or $4,100 worth of apples. The non - profit Natural Resources Defense Council estimated that "a 60 - acre alfalfa farm using 240 acre - feet of water would generate approximately $60,000 in sales. In contrast, a semiconductor plant using the same amount of water would generate 5,000 as much, or $300 million."


Page 93) Livestock's Consumption of  Water is Huge - and Growing


Farm animals directly consume about 2.3 billion gallons of water per day, or over 800 billion gallons per year. Another 200 billion gallons are used to cool the animals and wash down their facilities, bringing the total to about 1 trillion gallons. That is  twice as much as is used by the 9 million people in the New York City area.


Although water used for livestock accounts for a tiny share of national water consumption - about 0.5 percent - it is the fastest - growing portion, both in terms of water to drink and the "virtual" water used to grow grains, oilseeds, hay, and pasture. From 1990 to 1995, most categories of water (surface and ground) consumption fell, but water for public use grew by 4 percent and water used for livestock (including fish farming) grew by 13 percent. Combined with the growing number of livestock over the past 20 years, the increasing number of large cattle feedlots and industrial hog farms may contribute to rising demand for water.


Hog farms use large volumes of water to prepare manure for storage in huge lagoons, and feedlots employ misting systems to cool cattle. On traditional farms, in contrast, livestock might find shade or other natural ways to cool off.
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