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Text-only version for easy printing Water, water, nowhere? In the 21st century, clean water will set the limits on growth and prosperity By David Appell Foaming water pours out of the Durham mill pond over the Oyster River dam in a roaring torrent. Released from confinement in the placid, weed-choked pond, the water leaps and gurgles as it rushes to the sea. UNH scientist Charles Vörösmarty '83G, '91G dips his hand in the brown water at the dam's edge, measuring the tug of the spring current, at its strongest now after the snowmelt. "Two hundred years ago, water entering this river at its source would have taken one half of a day to reach the estuary," Vörösmarty says, shaking shimmering droplets off his fingers. "Today, Oyster River water takes twice that time to reach the estuary. Water everywhere is taking longer to get to the sea because of dams like this one, pollution, elevated sediment transport and destruction of flood plains." In fact, some of the river's water is delayed in its journey for much more than a day. About 800,000 gallons gets sidetracked every day into the water system serving the town of Durham and the university. Normally, the river and an artesian well in Lee can meet the community's demand. But in a dry summer like 1999, the town must restrict water use and turn to the Lamprey River for some of the water it needs. Currently, during dry times, the town pipes water from the Lamprey to the headwaters of the Oyster River, in essence recharging that river. But this fall or next spring, the town plans to build a direct pipeline from the Lamprey to the water treatment plant. Durham is far from the only New Hampshire town concerned about future water supplies, especially in the state's fast-growing southern tier. Newmarket, which has drawn its water from two artesian wells since the 1970s, will probably need to augment its supply from the Lamprey River in the near future--possibly as soon as this summer--according to town water and sewer superintendent George Laney. Low water pressure in Exeter and a significant drop in Portsmouth's Bellamy reservoir during the summer of 1999 have those towns looking for alternative sources. Hampton imposes water-conservation restrictions on residents each summer, banning lawn watering and car washing. And there is anecdotal evidence from well drillers that overuse of groundwater in the Bedford area means that wells need to be drilled deeper and deeper, Vörösmarty says. More precious than oil There is a message in the fact that prosperous towns in water-rich New Hampshire, where the average rainfall is 3.5 inches a month, are concerned about their water supplies. It gives us just the slightest glimpse of a looming problem of global proportions. In fact, an insufficient supply of clean water will probably be the single biggest problem facing most of the nations of the world throughout this century. Water shortages will affect more people more quickly and more dramatically than global warming or dwindling supplies of energy. And a recent UNH study reveals that the problem is much more serious than anyone had thought. "The number of people experiencing water shortages right now is at least a billion more than any study had previously estimated," says Vörösmarty, an associate professor in UNH's Department of Earth Sciences and the Institute for the Study of Earth, Oceans and Space. "When we look at projections for the year 2025, the undercount is even greater." Vörösmarty, 46, is part of the Water Systems Analysis Group at UNH. He has been studying and reporting on water shortages around the world for the past several years. He and his research team have developed a computer model that analyzes the problem on a much finer scale than any previous study. His research, which began as a yearlong project in a graduate course that he taught, shows how the availability of water is likely to be affected by population growth, economic development and climate change. For many parts of the world, the picture looks bleak indeed. Each day, each person on Earth withdraws, directly and indirectly, an average of 450 gallons of water (see sidebar, page 35). Two-thirds of this amount goes to irrigate the crops they eat (or crops used to feed the animals they eat), and the remainder is used for domestic or industrial purposes. Societies begin to experience moderate levels of "water stress" when they use 20 percent of the water supply available to them. Those needing 40 percent or more are at serious risk, with health repercussions and severe restrictions on economic activity. Vörösmarty points out that those figures represent percentages of mean annual flow in the water supply. There are large variations in flow from season to season, and many parts of the world don't have reservoirs to store water for dry times of the year. "Whenever water use is 20 percent or greater, there is an increasing preoccupation with getting water," he notes. A 1997 study by the United Nations tried to gauge the amount of water stress around the world by examining countries one at a time, comparing the amount of water available to each country with its overall domestic, industrial and agricultural needs. The results indicated that more than two billion people live under conditions of moderate water stress, and almost half a billion are already experiencing extreme stress. Dividing the world picture into 208 countries is a good start, but it's bound to overlook water problems in areas that are smaller than an entire country. The United States, for example, has an adequate water supply overall, but the outlook in Tucson is quite different from that in Seattle or Durham. Vörösmarty's group divided the globe into a grid of 60,000 cells (at the equator each cell is a square, about 30 miles on a side). They then built a computer model that combined a wealth of information: population distributions, industrial consumption statistics, climate-change models and "digital rivers"--detailed models of rivers and their water supplies compiled with data from more than 600 stream gauges and thousands of rainfall monitoring sites around the world. The researchers used the computer model to calculate water-stress levels for each of the 60,000 cells. They found that the United Nations study had vastly underestimated the number of people who are living with water shortages, and the number experiencing extreme shortages is about four times as high as the U.N. estimate. "By our reckoning, it's probably about a billion more people," Vörösmarty says. What's life like for these people? Difficult, says Vörösmarty. Since there is inadequate water for irrigation, it is hard to grow sufficient food, and food imports are often necessary. There may be restrictions on water use, as the domestic, industrial and agricultural sectors compete for what water is available. Human health is affected by pollution problems, because there isn't enough unused water to dilute waste. Signs of stress While few areas in the United States are currently experiencing this degree of difficulty caused by extreme water shortages, some signs of stress can be seen. Cities and rural areas are increasingly in conflict over water in Southern California. Los Angeles has built pipelines to rivers and lakes hundreds of miles away, diverting water that used to irrigate cropland and orchards. Some years ago there was even talk of building a pipeline to Alaska. The Colorado River offers a dramatic example of what happens when demand exceeds water supplies. The once-mighty river is literally sucked dry as it winds through the Southwest. Every drop of its flow--150,000 gallons a second--is gradually drawn off, primarily for irrigation, until the river slows to a trickle and finally stops miles short of the Gulf of Mexico. In the Midwest, the Ogallala Aquifer--one of the world's largest stores of groundwater--is being depleted at an alarming rate. The aquifer lies beneath eight U.S. states, an area just slightly smaller than Texas. In the 1940s, farmers began to notice that they were having to drill deeper to reach water for their irrigation pumps. From then until the early '90s, the water level in the aquifer dropped at an average rate of less than half a foot each year. But by 1995, well measurements showed that the level was dropping three feet a year, causing the land above the aquifer to subside dramatically in places. Since then, irrigation has been cut back, and Texas, Oklahoma, Kansas and Colorado have all been losing irrigated land over the last two decades. Fortunately, the United States has the natural and the economic resources to compensate for these changes. A country that is both dry and poor faces much greater difficulties. A 1997 trip to drought-stricken Kenya gave Vörösmarty a first-hand view of just such a situation. "We saw people with buckets on their heads traveling several kilometers to go to a single drain pipe that could give them clean water, because all their surface water supplies had dried up," he says. "People were spending large parts of their day getting their buckets of water. It's a different set of challenges if you're in the developing world, where you don't have the economic infrastructure to buffer you against these difficulties." Many other nations also see a water crisis impending if not already present. For example:
The amount of water available for the future is only part of the equation. The quality of that water must also be carefully considered, as it affects human health. As many as 1.2 billion people lack access to clean drinking water, according to Peter Gleick, director of the Pacific Institute for Studies in Development, Environment and Security. Nearly half the world's population lives without sanitation--no sewers, toilets or latrines--and preventable water-related diseases kill an estimated 10,000 to 20,000 people every day. "Human waste has an enormous impact on water quality," says Vörösmarty. Even where there are sewers, they often just move the problem to the nearest river. "There's a delicate balance between human health and the health of ecosystems, and if you begin to err on the side of human health, that means that the ecosystems may be placed in jeopardy." The wild card The wild card in the world's water supply is global warming, which most scientists now accept is occurring, according to Vörösmarty. "I think there is a fairly strong signature of climate change. The big question is, what impact will it have on water supplies?" In January, the United Nations' Intergovernmental Panel on Climate Change (IPCC) issued its latest report on global warming, stating that the Earth's average temperature is likely to rise by between 2.5 and 10.4 degrees Fahrenheit in this century. (By comparison, the Earth's temperature has risen about 9 degrees since the last ice age.) Sea levels could rise by as much as 35 inches. Higher average temperatures have a multitude of effects on the hydrologic cycle: increased evaporation rates, higher rainfall amounts and decreased snowfall. However, because more of the precipitation may come in the form of intense storms, floods will be more likely, and less of the rainwater will be available for use. Increased evaporation could create more droughts. Hydrologic records--on which modern irrigation, dam construction and water releases are based--will become more difficult to interpret. "At a time when water scarcity calls for intensified planning," wrote Jacques Leslie in last July's Harper's Magazine, "planning itself may be stymied." Vörösmarty and his group wanted to assess the importance of climate change on the world's water supply. They incorporated currently-accepted climate-change scenarios into their computer model to predict the water supply in 2025. What they found disputes much of the current thinking on global warming and water scarcity. Climate change will account for only about 20 percent of the impending global crisis in water scarcity, the study found, while population changes and economic development account for the remaining 80 percent. "What global warming does is make the world only about 5 percent drier on average, and on a regional scale you have big winners and losers," says Vörösmarty. With population growth, economic development and climate change all in its model, the UNH group was able to obtain a wide-ranging, geographically detailed view of the world's water future. Most of the globe will have a more difficult time meeting its water needs, especially already dry Africa and the Asian subcontinent. Some areas will actually gain freshwater resources. Parts of central and northern Asia, especially, will become relatively wetter, as will regions of the western U.S. and Canada. Vörösmarty's research underlines the difficulty of predicting regional effects. Take China, for example. The scenarios show that climate change is likely to mitigate many of the effects of an increased population and water demands on the Yellow River. By contrast, only 500 miles to the south, the conjunction of climate change and economic development means that demands on the Chang Jiang (Yangtze) River will more than quadruple. (It is in the middle course of the Chang Jiang that the controversial Three Gorges Dam project is being constructed.) As that example demonstrates, the water situation is extremely complicated, and relatively small regions differ significantly in their response to a host of factors. "It's the interaction between climate, population growth and economic development together that gives you the relative water demand signature," Vörösmarty says. The current focus on climate change masks the strain an increasing population will place on the Earth's freshwater resources. "It could be a real problem for us, as a society, to cope with this, because we're going to have all these hot spots popping up. I think in the United States the issue will be more a matter of economic concern than a question of survival, because we can pay our way out of problems. People who live in developing countries are already quietly suffering." ~ David Appell is a physicist and free-lance writer who lives in Gilford, N.H. He specializes in stories about scientific topics. For more information, see the Water Systems Analysis Group Web site at http://www.watsys.sr.unh.edu. |