Will There Be Enough Water in the Next Century? Population growth and pollution place enormous stress on the world’s supply of usable water. The world’s population continues to increase, but the water supply remains constant and is unevenly distributed. By the end of the 21st century, enough usable water may not exist for everyone. In this February 2000 article from Encarta Yearbook, freelance writer Steve Turner surveys a range of expert opinion on the need to protect water supplies and use them more efficiently. Will There Be Enough Water in the Next Century? By Steve Turner Water shortages on planet Earth? It seems impossible. Images of our planet from outer space show vast oceans, lakes as big as small countries, and wide rivers flowing with incredible volume. How can there not be enough water? Earth has enormous water resources, approximately 1.35 billion cu km (about 326 million cu mi) of it, enough to submerge the United States (including Alaska and Hawaii) under 147 km (92 mi) of water. But more than 97 percent of it is salt water, lethal to crops and unfit for human consumption. Earth’s freshwater resources are much smaller, about 38 million cu km (about 9 million cu mi), and in some regions they are coming under stress. For example, the Colorado River waters so many towns and fields in the United States that often it does not reach the sea. Many other rivers also run dry for parts of the year, including the Yellow River in China, the Indus River in Pakistan, and India’s sacred Ganges River. So much water has been diverted from the rivers feeding the Aral Sea, which straddles the border between Kazakhstan and Uzbekistan, that the sea has shrunk to half the size it was in 1960. The world is facing the prospect of water shortages caused by population growth, uneven supplies of water, pollution, and other factors. The United Nations (UN) predicts that water shortages could retard the economic growth of some countries and lead to food shortages and, possibly, to international conflicts. Where Is the Water? Very little water has been created or lost over the past billion years. Instead, the same water has traveled countless times through the water cycle. The water cycle begins when ocean water is evaporated, nearly salt free, into the atmosphere by the sun’s heat. At any one time, less than 0.1 percent of Earth’s fresh water is stored in the atmosphere. The water then falls back to earth as rain, snow, fog, dew, or another form of precipitation. In permanently cold climates, such as those of Antarctica or Greenland, the snow that falls becomes part of the great ice caps and glaciers, where 77.7 percent of the world’s fresh water is stored. In warmer areas some of the water soaks into the ground and is called groundwater. A small amount adheres to the soil and becomes soil moisture. Groundwater makes up 22.2 percent of the Earth’s fresh water. Much of this water is stored below the surface in aquifers (layers of permeable rock, sand, or gravel). Soil moisture accounts for 0.2 percent of the Earth’s freshwater supplies. The water that does not soak into the ground joins streams, rivers, and lakes and is called runoff. The rivers of the world contain less than 0.1 percent of Earth’s fresh water, while freshwater lakes contain 0.3 percent. Eventually, most of the water that fell as precipitation makes its way back to the ocean, where the cycle begins anew. Groundwater and water from lakes and rivers constitute the main sources of water that humans use. These sources can be further divided into water sources that are renewable and water sources that are nonrenewable. Renewable sources include lakes, rivers, and aquifers that are regularly recharged (refilled). According to the World Resources Institute, an environmentally oriented research group located in Washington, D.C., the world’s annual renewable freshwater resources total about 0.1 percent of Earth’s total fresh water resources. Nonrenewable sources include passive aquifers (aquifers filled millions of years ago that receive no predictable recharge). This type of water is also called fossil water. Humans and Water Since the earliest days of human history, people have collected rainfall and its runoff, dug wells to access groundwater, and built dams or aqueducts to capture and reroute water. At the same time, they developed laws to guide the use of this precious resource. The Code of Hammurabi, a set of laws attributed to an ancient Babylonian king, contains several passages concerning water used for irrigation. Humans use water for three basic purposes: agriculture, industry, and domestic and municipal use (water for drinking, cooking, cleaning, and so forth). In the mid-1990s humans withdrew (removed from rivers, lakes, and aquifers) 3,750 cu km (900 cu mi) of water each year for these purposes, according to the United Nations (UN). About 2,270 cu km (540 cu mi) of that water was consumed (no longer available for immediate use). Examples of ways in which water can be consumed include water that evaporates from irrigated fields, becomes part of finished industrial goods, or is absorbed by a plant or animal. Of all the uses humans have for water, agriculture has always required the most. Even today, to produce 1 metric ton (1.1 tons) of grain takes some 1,000 metric tons (1,100 tons) of water—enough to fill up three average-sized houses. According to the UN, about 70 percent of all water withdrawals in the 1990s were used for agricultural purposes. Agriculture also consumes more water than any other use. UN figures indicate that more than 90 percent of water used for agriculture is consumed, much of it through evaporation. Industry, by comparison, uses far less water. For example, less than 2 metric tons (2.2 tons) of water are needed to manufacture 1 metric ton (1.1 tons) of aluminum. According to the UN, about 20 percent of water withdrawals in the 1990s were used for industrial purposes—as a coolant, a solvent, or as part of finished goods, such as soft drinks. On average, less than 4 percent of the water used by industry was consumed, with the remainder returned to rivers and lakes as discharge. This discharged water is a major source of water pollution around the world. Municipal and household uses drew the smallest amount, less than 10 percent of total withdrawals, less than 3 percent of which is consumed, the UN reported. If left untreated, municipal wastewater can be a significant source of water pollution. These basic divisions of water use vary widely among nations. Industrialized nations, such as the United States and many European countries, withdraw less for agriculture and more for industry. In countries where agriculture is the primary industry and in countries with hot climates, water withdrawals for agriculture can be higher than the global average. Municipal and domestic usage also varies. According to the UN, a person living in Europe or North America uses between 500 and 1,000 liters (130 to 260 gallons) of water per day. The typical person living in the developing countries of Asia, Latin America, and Africa uses between 50 and 100 liters (13 to 26 gallons) per day. In areas where water is scarce, the figure is even lower. Is there enough water for everyone? According to the UN Commission on Sustainable Development, humans currently use about half of the 12,500 cu km (3,000 cu mi) of water that is readily available from groundwater, rivers, and lakes. So by a simple measure of liters and gallons, there is enough water to quench the thirst of every creature and plant, every field, and every industry now existing, plus more to come. But water remains a fixed resource. “Given an expected population increase of about 50 percent in the next 50 years, coupled with expected increases in demand as a result of economic growth and life-style changes, this does not leave [much] room for increased consumption,” the UN commission said. A certain amount of water must be set aside to support the environment. Humans cannot drain the world’s lakes, rivers, and aquifers without causing catastrophic environmental damage. Population Pressures The world’s population grew enormously in the 20th century. According to UN estimates, 1.65 billion people lived on Earth in 1900. By 1999 the world’s population had passed 6 billion people, and the UN estimates that it will reach 9 billion people by 2050. But the annual supply of renewable fresh water will remain constant. As the UN Commission on Sustainable Development noted, the amount of water available to each person decreases as the population grows, raising the possibility of water shortages. According to the UN, one consequence of increasing water scarcity will be competition for resources. In some places this competition may result in higher prices for water as various consumers bid for available supplies. In many cases industries and municipalities will be able to outbid small farmers, driving those farmers out of business. Large-scale agricultural operations will likely be able to pay higher prices, but the rising price of water may be passed on to consumers in the form of higher food prices. This could cause problems if people in poor countries are unable to afford the food they need. Uneven Supply and Water Stress Water shortages will not come all at once in every part of the world. Just as the world’s population is unevenly distributed by region, so is the annual supply of renewable water. Rainfall and snowfall are determined by uneven weather patterns and landscape, and as a result, some areas of the world get more precipitation than others. For example, Canada is one of the largest countries in the world, with a total land area of about 10 million sq km (4 million sq mi). In the late 1990s Canada’s population was about 29 million people. In India, by contrast, about 984 million people live in a total land area of 3 million sq km (1 million sq mi). Clearly India has a higher demand for water than Canada. But Canada has more water. According to the World Resources Institute, Canada’s annually renewable water resources total 2,901 cu km per year (696 cu mi per year), compared with India’s 2,085 cu km per year (500 cu mi per year). The same holds true elsewhere in the world. Brazil has more renewable water than central and southern Africa. And the combined renewable water resources of Israel, Jordan, Lebanon, Syria, and Egypt are less than that of Nicaragua alone. This uneven distribution of water resources means that supplies in some parts of the world are already stretched thin. According to the UN, about one-third of the world’s population lived in countries with moderate to high water stress in the late 1990s. Moderate water stress means that the country is currently using 20 percent or more of its annual renewable resources. Countries in this category included Germany, India, South Africa, Spain, and the United States. High water stress means the country is using 40 percent or more. Countries in this category included Egypt, Iran, and Saudi Arabia. By 2025 the UN expects that two-thirds of the world’s population will live in countries with moderate to high water stress. Dams and Wells Natural water scarcity has prompted many nations to try to augment their water supplies by building dams to catch water that otherwise would escape to the sea, or by sinking more and deeper wells. But these efforts can have negative side effects that can contribute to water scarcity. By impounding reservoirs of water, dams help ensure a constant supply of water. But these massive reservoirs also play a wasteful role. For instance, Egypt’s Lake Nasser, a reservoir of Nile River water impounded by the Aswan High Dam, loses up to 10 cu km (2.4 cu mi) per year to the hot sun. That is enough water to submerge 1.2 million hectares (3 million acres) of cropland under 60 cm (24 in) of water. Reservoirs lose additional water that seeps into the soil, a problem that is compounded if the canals that carry the water from the reservoir are unpaved. The Imperial Irrigation District in California, for example, estimated it could save enough water to irrigate 4,000 hectares (10,000 acres) simply by lining a delivery canal with concrete. Most experts believe that big dams indirectly encourage people to use water inefficiently. Built by governments, dams typically deliver water for agriculture at a low, subsidized price. Because the water is so inexpensive, farmers sometimes overwater their crops, which can lead to water loss through evaporation. The water also dissolves salts that occur naturally in the soil. When the water evaporates, these salts build up in the soil, a process known as salinization. Eventually, salinization makes growing crops difficult or impossible. It can also affect the groundwater below. According to water analyst Sandra Postel, director of the Global Water Policy Project in Amherst, Massachusetts, one out of every five acres of irrigated land worldwide has been damaged by salinization. This raises the possibility that, in addition to water shortages, the world will also face shortages of arable land and food. Instead of building dams, some countries choose to increase their access to groundwater. But this practice increases the risk of overpumping aquifers. “It’s a huge problem,” says John Briscoe, senior water adviser at the World Bank, a specialized agency of the UN. The four nations with the most irrigated cropland—China, India, Pakistan, and the United States —are all using groundwater faster than it can be replenished. And according to other UN reports, overpumping has caused the land over some aquifers in China, Japan, Mexico, Thailand, and the United States to sink by as much as 10 m (30 ft). Pollution Pollution also affects the water supply, reducing the available water by making it toxic or otherwise unfit for human use. Nitrates from farm fertilizers as well as industrial chemicals can sink into groundwater or flow into streams, where they pose risks to both health and the environment. Nitrates used in fertilizers have been linked to some health problems, including methemoglobinemia (a type of anemia also known as blue baby syndrome) in infants. High levels of nitrates can also damage the environment by stimulating algae growth. The algae reduce the amount of oxygen in the water (a process known as eutrophication), killing other organisms. Pesticides and herbicides (chemicals used to kill unwanted insects and plants) enter the water supply in the same way. Humans and animals that ingest the water also ingest these chemicals, which have been shown to cause cancer, reproductive problems, and death. According to the U.S. Environmental Protection Agency (EPA), about 10 percent of wells in the United States contain pesticides. Animal and human wastes represent another source of water pollution. This type of water pollution is an issue throughout the world, but is worst in the less industrialized nations of Africa, Asia, and Central America. According to the UN, more than 90 percent of wastewater in developing countries goes untreated, and 50 percent of the world’s population does not have adequate sanitation. At least 20 percent of the world’s population has no access to drinking water that is free from pollutants or disease-causing microbes. This means that, at any one time, approximately half of the people in the developing world suffer from conditions such as diarrhea (the causes of which are often transmitted through water). Climate Change Climate changes caused by global warming could also affect water resources. Global warming is caused by burning fossil fuels, such as oil and coal, and by some agricultural and industrial processes. These activities contribute to rising amounts of greenhouse gases (gases that trap the sun’s heat) in the atmosphere. Scientists disagree over the extent to which global warming might alter the Earth’s climate and how quickly it might do so. Nevertheless, most experts agree that elevated global temperatures could change the world’s rainfall patterns. This change could create or worsen water stress in some regions while perhaps alleviating it in others. Fighting over Water Water shortages could also lead to international conflict as countries compete for limited water resources. In 1995 Ismail Serageldin, a top official at the World Bank, declared, “the wars of the next century will be over water.” Political tensions over water often result when different nations lay claim to the same river, lake, or aquifer. According to the UN, more than 300 river basins and aquifers worldwide cross national boundaries, creating the potential for conflict. Conflicts over water, for example, have sprung up in the volatile Middle East. The Jordan River forms part of the border between Israel and Jordan, and both countries depend heavily on its water. Each nation has a growing population, an agricultural industry largely dependent on irrigation, and few groundwater supplies. The historic 1994 peace treaty between Israel and Jordan included a provision that required Israel to share more of the Jordan River’s water with Jordan. Israel’s slow progress in meeting this commitment forced a return to negotiations in 1997, which resulted in an agreement to pump water from the Sea of Galilee (a freshwater lake) to Jordan. The UN has taken some steps to offset the likelihood of warfare over water. In May 1997 the UN agreed to the Convention on the Law of the Non-Navigational Uses of International Watercourses, an international treaty that sought to promote cooperation among countries on water issues. But as of February 2000 this treaty had not yet entered into force. What Can Be Done? Improving international cooperation on water issues is a step in the right direction, but the fact remains that the world’s water resources will never increase. As a result, many water analysts agree that the world must use the water it has more efficiently. Postel, among others, asserts that the world must double the benefit from every unit of fresh water in order to meet its growing needs. Conservation According to Postel and other experts, conservation is one way to accomplish this goal. Steps as simple as installing low-flush toilets and low-flow showerheads could have considerable impact if applied worldwide. Another way is to reuse household wastewater. Water treatment experts say that technology has advanced to the point that this wastewater can be cleaned into water fit for irrigating crops and for laundry, and safe for drinking (if consumers are willing to accept it). Treated water also can be injected into aquifers to offset the amount being pumped out. Communities in Texas, California, and Virginia have already begun pumping treated wastewater into aquifers for reuse. The amount of water used in households pales in comparison to the amount used to irrigate crops. Steps to conserve water used for irrigation can result in great savings. For example, drip irrigation systems deliver water through plastic tubes directly to plant roots, cutting down on water lost to evaporation. Reducing evaporation also reduces salinization. Numerous studies have shown that drip irrigation, pioneered in Israel in the 1960s, also increases crop yields. Briscoe of the World Bank says that another possible conservation measure is to develop strains of crops that use less water. Clean It Up Most experts agree that both humans and the environment benefit when steps are taken to combat water pollution. Many steps can be taken in this area, from laws that regulate polluters and set standards for clean water to education programs that teach people how to avoid polluting local rivers, lakes, and aquifers. In 1972 the Congress of the United States passed the Clean Water Act. This act set national standards for water quality and encouraged the construction of sewage treatment plants, resulting in significant reductions in point pollution (pollution from a single concentrated source, such as a factory). Water quality in the United States has improved greatly as a result, with many rivers and lakes recovering from years of pollution damage. Nonpoint pollution is pollution from diffuse sources such as farms and automobiles. According to the EPA, nonpoint pollution is the biggest challenge facing water supplies in the United States. In 1987 Congress amended the Clean Water Act to establish the Nonpoint Source Management Program. This program provides federal funding for local efforts to control nonpoint pollution. The EPA has also worked to educate citizens about methods for controlling nonpoint pollution, such as cutting back on pesticides and fertilizers where possible and disposing of used motor oil and other household wastes through approved hazardous waste programs. Many other countries have taken similar steps to control water pollution within their borders. International efforts to control water pollution face many challenges. Countries do not always agree on what needs to be done or who should pay for it. Nevertheless, the world has agreed on some basic principles. In 1992 representatives from more than 150 countries met in Rio de Janeiro, Brazil, for the UN Conference on Environment and Development. One of the documents to emerge from this conference was Agenda 21, a sweeping blueprint designed to guide international environmental efforts. Among the many topics addressed by Agenda 21 are protecting water quality and cutting water pollution. Cost remains a major issue for many developing countries. Sewage treatment plants, for example, can cost millions of dollars. Nevertheless, the UN argues that the benefits—a healthier environment and population—are worth the price. Is Desalination the Answer to Water Shortages? If the world needs large quantities of water, one obvious place to get it is from the oceans. It seems so reasonable: When Earth’s growing population runs short of fresh water, water will have to be taken from the sea and desalinated (have the salt taken out). Several different methods can be used to desalinate seawater. Flash evaporation turns the water to steam, leaving the salt behind. The steam is then condensed into fresh water. This is the most widely used method of desalination. Electrodialysis uses an electric current to remove the salt. Reverse osmosis forces the water through a filter that removes the salt. Direct-freeze evaporation takes advantage of the fact that fresh water freezes at a higher temperature than salt water. Once the fresh water freezes, the fresh water ice crystals are separated from the remaining ingredients. Some of these methods are already used to supply water to areas in the Caribbean, Saudi Arabia, and Texas. The main drawback to desalinated water is that it uses large amounts of costly energy. Desalinated water typically costs $1 per 3,800 liters (1,000 gallons). Water taken from lakes, rivers, and aquifers costs about half as much to domestic users and as little as 5 cents per 3,800 liters for agricultural users. Thus, the added cost of desalination makes this method of supplying fresh water impractical for agricultural needs and for developing nations. Some advocates believe that research into improved desalination techniques will intensify as water supplies become scarcer. One of these advocates is former U.S. senator Paul Simon, now director of the Public Policy Institute at Southern Illinois University in Carbondale. Simon believes that this research may result in new technologies that will eventually lower the cost of desalinating water. But others, such as Peter Gleick, president of the Pacific Institute for Studies in Development, Environment, and Security in Oakland, California, are not so optimistic. “I believe desalination is going to be more important in the future than it is today. We’re going to use it more, it’s going to be cheaper. It’s going to meet high-valued industrial uses. It’s going to be useful in coastal areas [and] for urban supply in some places. It’s just that four-fifths of the water the world uses goes to agriculture, and I do not see desalination providing any of that water,” says Gleick. Briscoe agrees, although he expresses hope that efforts to make desalination cheaper will benefit coastal cities, where about 60 percent of the world’s population live. Nevertheless, current technology is economical for desalinating brackish well water, water that is salty, but less so than seawater. Many small desalination plants have already begun to process brackish water in locations around the world. But ocean water is desalinated only in wealthy places that have no practical alternative water source. Saudi Arabia is a good example. Home to about half of the world’s desalination capacity, Saudi Arabia uses the wealth generated by its vast petroleum reserves to pay the high cost of preparing seawater for human use. Looking Forward Despite the fact that the ways people use water have caused shortages and water stress in many regions of the world, “[humans] have not yet crossed the line of no return,” according to the UN Commission on Sustainable Development. “There are many practical, cost effective measures that can reduce the strain of water resources.” Improved irrigation techniques can reduce water losses and improve crop yields. Investments in sanitation can give more people access to safe water. Water pollution can be reduced. Countries can find new ways to cooperate on water issues. Looking toward 2050, Postel says, “We could balance supply and demand. The question is whether basic human needs will be met, and the environment will be healthy. The conservation technologies are there. It’s a matter of whether we decide to mobilize and get the job done.” About the author: Steve Turner is a freelance writer. Further reading: Clarke, Robin. Water: The International Crisis. Massachusetts Institute of Technology Press, 1993. Donahue, John M., and Barbara Rose Johnston, eds. Water, Culture, & Power, Local Struggles in a Global Context. Island Press, 1998. Gleick, Peter H. The World’s Water: The Biennial Report on Freshwater Resources. Island Press, 1998. Landry, Clay. Saving Our Streams Through Water Markets. Political Economic Research Center, 1999. Postel, Sandra. Last Oasis: Facing Water Scarcity. W. W. Norton, 1997. Postel, Sandra. Pillar of Sand: Can the Irrigation Miracle Last? W. W. Norton, 1999. Reisner, Marc. Cadillac Desert: The American West and Its Disappearing Water. Viking Penguin, 1993. Simon, Paul. Tapped Out: The Coming World Crisis in Water and What We Can Do About It. Welcome Rain Publishers, 1998. Source: Encarta Yearbook, February 2000. Microsoft ® Encarta ® 2007. © 1993-2006 Microsoft Corporation. All rights reserved.
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