Water has always been and continues to be one of the major challenges of civilization. It could be the biggest problem of the 21st century. This statement, which opens Robert Kandels 2003 book Water From Heaven, intrigued me. Most of us know little about the current and impending global water crises. How much potable water exists, where does it occur, how is it used, abused and wasted, and what must humankind do to solve the water problem? Knowing the answers to these questions is essential to addressing the challenges ahead.
As Ive learned, a small amount of terrestrial water comes in fresh liquid form. Almost all (97.2 percent by volume) is saltwater. For thirsty coastal nations, desalinization might help, but the two leading techniques have drawbacks. Multistage flash distillation is expensive and uses lots of energy. Reverse osmosis using semi-permeable membranes produces freshwater at five times the cost of normal water processing.
The 2.8 percent of terrestrial water that is fresh occurs mostly as ice and snow, primarily in Greenland and Antarctica, making it unavailable to the drinking supply. Towing blocks of polar ice to parched countries in the Middle East is costly and impractical.
That leaves less than one-tenth of a percent of Earths water that is fresh. Fifty to sixty times as much surface water lies in lakes as in rivers and streams, and one-fifth of all surface water fills the Great Lakes basin (see story, this issue). Conflict over lake water is growing, as communities far from the shorelines of the Great Lakes face shortages, according to an Aug. 12 article in The New York Times.
Most freshwater lies underground, where ninety times as much freshwater occurs as on the surface, much at depths of a kilometer or more. Difficult and expensive to tap, it will be increasingly necessary to do so.
The best-known and largest American groundwater reservoir, the High Plains (Ogallala) aquifer, contains a volume of water about equal to that of the Great Lakes basin. In the last half-century, however, it has lost about 6 percent of its stored water (see Geotimes, May 2004) twice what the Missouri-Mississippi system delivers to the Gulf each year.
In looking at how much water we have, it is also important to look at how we use it. I incorrectly believed that the purposes for which water is used in the United States have changed radically in recent years thinking that now the biggest use is for drinking and sanitation, meaning that the water is lost after its used. Wrong!
According to a U.S. Geological Survey 2004 report (see Geotimes online, Web Extra, March 19, 2004), water usage has been constant for decades: Public supply (water withdrawn publically or privately) delivered to users for various purposes (drinking, washing, industrial or thermoelectric) is only 11 percent. Almost half of the water withdrawn is to produce electricity via hydropower, coal-fired steam turbines and nuclear reactors, and this is almost entirely recoverable. But agriculture (irrigation) accounts for 34 percent of water use, and much of this water is not directly recoverable.
One-fifth of U.S. agricultural water is used just in California. Together with four other states (Idaho, Colorado, Nebraska and Texas), the total is 56 percent of the nations use. This agricultural allocation may be unsustainable, given the low cost of use of the water. These five states feed us and our livestock, but can we continue to allocate more than half the water used solely to agriculture?
Globally, even more water (70 percent) is used for agriculture. Irrigation water outside Europe and North America is typically polluted, with up to half lost to runoff, percolation and evaporation. Universal adaptation of downward-facing drip irrigation techniques can halve this loss.
In the end, it is unclean water, not insufficient amounts of water, that is the deadliest threat. Most recently, Hurricane Katrina made us aware of the health problems caused by unclean water and inadequate sanitation. But water pollution and substandard sanitation is the norm in much of the world.
About one-fifth of the worlds population drinks unclean water. Two-fifths lack proper toilets and sewage systems, leading to diseases and deaths, especially among the poor and young. The World Health Organization conservatively estimates that 1.8 million people die annually of water-related diarrheal diseases including cholera. Other estimates double or triple this figure. In 2002, 1.1 billion people (two-thirds of whom live in Asia) lacked access to improved water sources; 2.6 billion people (half living in China and India) lacked access to improved sanitation. The world continues to neglect this disgraceful situation.
Water problems are serious, global and solvable. We must take better care of this delicate resource and use it more intelligently by applying better technology. Our thirst can be quenched with unselfish international efforts.
The highest priority should be given to improving sanitation and access to clean water in Africa, Asia and India. As many as 125 million additional deaths could occur by 2020 unless steps are taken, according to the Pacific Institute in Oakland, Calif. Readily available water-conservation and recycling programs can make water available for drinking, sanitation, and industry. But such efforts, including low-volume plumbing and drip-free faucets, have limited impact. More importantly, policy should change such that water distribution dictates agricultural development, not vice versa.
Without understanding these basic underlying facts, we have no hope of meeting our future water needs. Educating ourselves about the issue is key, and dedicated issues of Geotimes like this contribute to that effort. I drink to that!
Schwab is a professor of geology at Washington and Lee University in Lexington, Va. E-mail: firstname.lastname@example.org.
"Rejuvenating Restoration of the Great Lakes," Geotimes, May 2006 Print Exclusive
"Western Aquifers Under Stress," Geotimes, May 2004
"Steady water use," Geotimes online, Web Extra, March 19, 2004
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