Water Conservation

Conservation is the philosophy that natural resources should be used cautiously so that they will remain available for future generations of people. In practice, conservation is the act of protecting, managing, and restoring shared earth resources such as soil, air, forests, minerals, petroleum, wildlife, and water—one of humans' most essential resources. Water conservation can be as simple as one person using water sparingly during a drought (prolonged period of dry weather), or as complex as a multi-national committee de veloping a long-term water distribution plan for an entire continent.

The word conservation means different things to different people, and a workable conservation plan for a particular region or resource usually involves a compromise between several interest groups. Consider, for example, a forest. To a logging company, forest conservation means developing a system of cutting and replanting healthy, fast-growing trees that ensures continuing profits. To a forest ecologist (a person who studies relationship between organisms and their environment) it means restoring a forest to a more natural state that supports a healthy community of plants and animals, along with protecting its most fragile areas and species. To a homeowner conservation means preserving the natural beauty of the forest and safeguarding property from forest fires. And to a preservationist it means letting nature manage the forest with little or no human intervention.

Conservation generally involves managing natural resources to serve people, whether by providing materials for essential needs (water, food, shelter, and energy) and consumer products (cars, clothing, computers, furniture), or simply by protecting wild areas where people can enjoy nature and outdoor recreation. While most scientists do not argue with using Earth's natural resources to meet human needs, most scientists also agree with the general idea that shared natural resources should be protected from overuse and pollution, and wisely managed using sound scientific information.

Need for water conservation

Water is Earth's most plentiful natural resource. It covers almost three-quarters of our planet's surface. Astronauts say Earth looks like a "blue marble" from space with its blue oceans and white swirls of water droplets (clouds) in the atmosphere (mass of air surrounding Earth). Water is also a renewable resource. Water moves endlessly within the hydrologic cycle, and is almost never destroyed in the process. When humans draw water from lakes, rivers, oceans, or groundwater reservoirs (aquifers), new water replaces it. Water is even selfcleansing. When it evaporates, it leaves pollution and salts behind and forms clouds that produce fresh rainwater. New water that flows into polluted lakes and rivers acts to dilute (lower the concentration or amount) and disperse (spread out) pollutants.

Why then, if water is so abundant and easily replenished, do people need to conserve it? First, fresh, liquid water that is suitable for human use only makes up a small percentage of Earth's total water supply. Almost all (97%) of Earth's water is undrinkable salt water that resides in the oceans. In addition to being too salty to drink, seawater corrodes (wears away) metals and gums up machinery, making it unsuitable for most other human uses. Much of the remaining 3% is frozen in glaciers (slow moving mass of ice) and ice in the North and South Poles. Second, fresh water is distributed unevenly on Earth's surface. Some regions have abundant freshwater resources and others are arid (dry) deserts where water is scarce. Third, though water is a renewable resource in a general sense, local and even regional water supplies can run dry from overuse. Finally, human activities that add chemical substances to surface water, groundwater and the oceans can pollute water to the extent that it is unsafe for human use and damages the larger ecosystem. For all these reasons, water conservation and management are extremely important, especially in places where a large human population depends on a limited water supply.

Water conservation in history

Humans have shared public water resources since they first settled in permanent villages thousands of years ago. Early peoples however, usually solved water supply or contamination problems by simply moving their villages. When wells ran dry from overuse, or rivers became polluted with human waste, they just relocated to a new, unspoiled location. Ancient civilizations in the arid Middle East, Africa, and China, who needed to supply water to the residents of large cities and to permanent agricultural lands were the first true water conservationists.

Throughout history societies have succeeded, in part, because of water management plans that ensured a steady supply of unpolluted water through periods of drought (prolonged shortage of rain) and flood. The desert empires of Mesopotamia and Egypt flourished by using elaborate irrigation (crop watering) and plumbing systems to distribute water from the rivers Tigris, Euphrates, and Nile to cities and croplands. The Ancient Greeks constructed drainage systems and huge stone sewers at the palace of King Minos at Knossos on the island of Crete almost 5,000 years ago. Water engineering was one of the great hallmarks of the Roman Empire. The Romans built aqueducts, canals, irrigation systems, city sewers, and indoor plumbing throughout their vast empire. (The modern English word plumber comes from the Latin word for lead, plumbus, and the ingenious Roman lead workers, plumberium, who engineered the world's first reliable indoor plumbing.)

Civilizations and empires have also failed because of poor water conservation practices or water management. Populations that have overused their water supplies or have allowed their water to become polluted have suffered serious consequences. Many archeologists attribute the mysterious disappearance of the Anasazi people from the American Southwest to inadequate water supply. Diseases caused by poor sanitation and poisoning from lead pipes were ironically, two factors that contributed to the fall of the Roman Empire. Improper waste management has also played a major role in the spread of diseases such as the bubonic plague that killed millions of Europeans during the Middle Ages. Waterborne diseases such as cholera, typhoid, typhus, and dysentery thrive where sewers bearing waste from infected persons empty into a public water supply. Scientists only began to understand the dangers of microscopic bacteria in sewage-polluted water after an epidemic of cholera killed thousands of people in Europe and the United States in the 1830s.

History of the American conservation movement. The idea of conservation only began to gain popularity in the United States at the end of the 1800s. Until then the North American frontier had provided seemingly inexhaustible natural resources, including abundant fresh water. By the 1890s however, European settlement had reached across the entire continent, and the census of 1890 declared the American frontier closed. Unrestricted sport hunting had slaughtered the bison herds of the Great Plains and killed off the flocks of passenger pigeons that once migrated (traveled periodically) down the Atlantic coast. Logging, grazing, mining, and hydropower (power from water energy) development threatened America's most dramatic national landmarks. Niagara Falls, for example, nearly lost its untamed water flow.

The Gilded Age at the end of the nineteenth century was also a time of unregulated resource exploitation and social inequality that made conservation an appealing idea to the general American public and to government leaders. Powerful businessmen of the mining, timber, railroad, and ranching industries became immensely wealthy as they laid waste to America's pristine forests, prairies, wetlands and waterways. At the same time, most Americans saw their living standards decline. Without government oversight, laborers, owners of small businesses, and independent settlers were at the mercy of the economically and politically powerful industrialists. While the powerful of the gilded age enjoyed luxurious estates and the diversions of high society, average Americans received low wages, worked in poor conditions, and lived in crowded cities and towns.

Gifford Pinchot (1865–1946) founded the conservation movement in the United States in the late 1890s. Pinchot argued that the best use of nature was to improve the life of common citizens. Pinchot's ideas were inspired by his observations of environmental destruction and social inequality that resulted from unregulated wilderness exploitation during the 1800s. He was also influenced by the writings of other nineteenth century explorers and naturalists including George Perkins Marsh and John Wesley Powell. Pinchot had great influence during the presidency of Theodore Roosevelt (1901–9), and he helped to steer conservation policies from the turn of the century until the 1940s. (Roosevelt was an avid hunter and an ardent conservationist in his own right.) Pinchot became the first head of the U.S. National Forest Service when it was established in 1905. Its motto, "The Land of Many Uses" reflects Pinchot's philosophy.

Conservation efforts have continued in the United States since the era of Roosevelt and Pinchot. Government agencies, groups of private citizens, and even business leaders have developed strategies to protect America's natural resources. The U.S. government has set aside millions of acres of public land as national forests and parks, and a large group of agencies now manage the nation's natural resources in a scientifically and economically reasonable manner. Universities and professional schools offer courses in resource management and natural sciences such as biology and geology. The discipline of ecology, the study of communities of plants and animals that live and interact in a specific environment, blossomed as scientists, engineers, and policy makers sought to understand the natural environments they were charged to protect.

Some early conservation strategies may seem strange by modern standards, and have had unintended negative consequences. For example, extreme flood control measures along the Mississippi river system exposed a large human population to catastrophic mega-floods. However early environmental policies were based on the science of the time, and were unquestionably fairer and less destructive than the unchecked industrial development they replaced.

Water conservation programs and projects played a major role in President Franklin D. Roosevelt's (1882–1945) "New Deal" plan to revive the United States economy during and after the Great Depression of the 1930s. Government-sponsored hydroelectric projects such as the Tennessee Valley Authority (TVA), which dammed the Tennessee River for flood control and electricity generation, provided work for thousands of unemployed engineers and laborers. The Bureau of Reclamation, a government agency that manages the surface water west of the Rocky Mountains, constructed more than 600 dams during 1920s and 1930s, including Hoover Dam on the Colorado River, and Grand Coulee Dam on the Columbia River. East of the Rockies, the Army Corps of Engineers helped put the American public back to work by building dams and other water control structures in the Mississippi River system. The Soil Conservation Service was established to advise farmers in maintaining and developing their farmland.

Conservation or preservation? Pinchot and other early conservationists fundamentally disagreed with early preservationists who thought that some wilderness should be protected solely to preserve its beauty or its natural ecosystem. John Muir, an eloquent writer who worked to protect Yosemite Valley in California, led the early preservationist movement. He bitterly opposed Pinchot's vision of the nation's wilderness and waterways as warehouses of useful materials. Because of its more moderate stance, Pinchot's conservation became the more popular position and it has since guided U.S. environmental policy. The preservationists did however, strike a chord with the American public and some of their ideas were incorporated into a mainstream conservation movement. In the 1960s, environmentalists echoed Muir's arguments when they raised objections to conservation's anthropocentric (human-centered) emphasis. Late twentieth century naturalists such as Rachel Carson (1907–1964), Edward Abbey (1927–1989), Aldo Leopold (1913–1983), as well as more radical environmental groups, including Greenpeace and Earth First!, owe much of their legacy to the turn of the century preservationists.

Water conservation in the United States

Water is by far the most carefully managed natural resource in the United States today. The average American uses about 100 gallons (378.5 liters) of water each day for direct purposes such as drinking, cooking, bathing, washing clothes and dishes, watering lawns, and washing cars. Per person water use is even greater when including indirect uses such as irrigation for a person's food and water used to manufacture consumer products. A complex system of local, state, and national water boards and agencies manages the U.S. water supply to ensure that all 280 million Americans have access to a steady supply of fresh water.

It is only a slight exaggeration to say that every drop of river water in the United States encounters a human water control structure or system of some sort before eventually reaching the ocean or evaporating into the atmosphere. All of the nation's

The Hetch-Hetchy debate: What Use Is the Use of Wilderness?

The Hetch-Hetchy valley of the Toulumne River in California's Yosemite National Park was the subject of one of America's first and fiercest environmental debates. James Phelan (1861–1930), the mayor of San Francisco, and Pinchot, at that time head of the U.S. Forest Service, stood on one side of the bargaining table. Muir, founder of the Sierra Club, stood on the other.

In 1901, Mayor Phelan proposed damming the Tuolumne River to create a reservoir in the Hetch-Hetchy valley that would supply San Francisco with much-needed fresh water. To Pinchot and other early conservationists, the project was an example of the wise use of natural resources to improve the lives of common citizens. Most of the common citizens of San Francisco had never heard of Hetch-Hetchy, let alone made the 150-mile (241-kilometer) trip by carriage to enjoy its natural beauty. They were however, very interested in ending the perpetual water shortages and outbreaks of water-borne illness that plagued their booming city.

To Muir, the Hetch-Hetchy dam was heresy. He wrote, in a 1908 Sierra Club bulletin, "Hetch-Hetchy valley, far from being a plain, common, rock-bound meadow ... is a grand landscape garden, one of Nature's rarest and most precious mountain mansions.... Dam Hetch-Hetchy! As well dam for water-tanks the people's cathedrals and churches, for no holier temple has ever been consecrated by the heart of man." Muir campaigned tirelessly against the Hetch-Hetchy project. He wrote passionately in defense of Yosemite's natural beauty and spiritual worth. He took his appeal to lawmakers in Sacramento and Washington, D.C., and enlisted thousands of supporters.

To Mayor Phelan, John Muir was insensitive to the needs of people, and a thorn in the side of reasonable progress. Phelan's Hetch-Hetchy 1901 proposal was turned down, and Muir's campaign stalled the plan again in 1903, 1905, and 1907. Phelan wrote of Muir, "He [John Muir] is a poetical gentleman. I am sure he would sacrifice his own family for the sake of beauty. He considers human life very cheap." Phelan eventually triumphed in the aftermath of the 1906 San Francisco earthquake. The quake ruptured gas lines and fuel tanks and fires raged throughout the city. Residents assumed that city firefighters' inadequate water supply was one of the reasons for the total destruction.

Hetch-Hetchy reservoir was filled in 1913. Muir died, disappointed, a year later. Muir's legacy, however, remained. His book and essays continue to inspire new generations of nature lovers and environmental activists. John Muir was America's first environmentalists.

major rivers and most of its smaller rivers and streams are dammed, constricted by levees, or both to protect humans from floods, provide hydroelectric power, and hold back reservoirs (artificial lakes) that contain local water supplies. Engineers and water managers control river flows in the United States to such an extent that many floods and shortages are today an act of man as well as nature.

Water is one of the most economically valuable resources. In the bone-dry American West and Southwest, booming cities such as Phoenix, Las Vegas, and Los Angeles share scarce water supplies with large-scale agricultural regions such as California's San Joaquin Valley. Central California receives only a few inches (centimeters) of rain each year, but with irrigation water imported from the Sierra Mountains and the Colorado River, it has become "America's salad bowl." Much of the produce (lettuce, tomatoes, avocadoes) stocking the grocery store shelves in the United States comes from irrigated fields in the deserts of California and Texas. The Colorado River is so heavily used by the states along its path (Colorado, Utah, Arizona, Nevada, and California) that it contains only a trickle of water where it crosses the Mexican border and it no longer reaches the ocean. (In fact, because the Colorado River water distribution plan was agreed upon during a relatively wet period, the river actually contains less water than was promised to its various human users.)

Water use is strictly regulated according to local, state, and national laws. With the exception of small lakes and streams on private property, bodies of surface water are public property. In most states private landowners must allow the general public to use water from rivers or lakes on their property. Furthermore, they must abide by the same water quality and withdrawal guidelines as the rest of their water district.

Unlike surface water groundwater usually belongs legally to the owner of the overlying land. Most groundwater laws were written before scientists understood groundwater moves in underground reservoirs, and that single users can overuse or pollute shared groundwater resources. Individuals, industries, and communities that abuse groundwater usually face few legal consequences, especially compared to users who pollute or overuse surface water. If for example, a city's water reservoir runs low during a dry spell the regional water district can legally purchase water from other sources, and can require the whole community to take water-saving measures like restricting summertime lawn irrigation and car washing. If on the other hand, a farm's well goes dry after the farmer's neighbor lowers the water table (level below which rocks and soils are saturated with water) by over pumping, no legal action could be taken against the neighbor and the farmers would likely need to drill a deeper well.

International water conservation

Although water shortages, floods, pollution, and water-related legal conflicts are relatively common in the United States, water conservation policies generally ensure that Americans can trust their water supply. People in other parts of the world are not so fortunate, particularly in the developing nations of Africa, South America, and Asia. In many regions arid climate, rapid population growth, poverty, and political instability are a recipe for water shortages and pollution. Two-thirds of the world's population lives on less than 13 gallons (49 liters) of water per day. (Remember that an average American uses about eight times that much water.) When political tension becomes war or an already dry climate gets drier, people who were surviving with limited freshwater are faced with famine (food shortages leading to starvation) and disease.

In recent decades conservation has become a critical issue for the international community. Organizations such as the United Nations Environment Program (UNEP), the International Union for the Conservation of Nature and Natural Resources (IUCN), and the World Wildlife Fund (WWF) are working to help individual countries plan for the maintenance and protection of their resources. Their strategy, called sustainable development, is based on a philosophy that is very similar to Pinchot's original conservation ideal. Earlier international programs viewed environmental protection and economic development as an "either-or" decision between preserving nature and human prosperity. Sustainable development schemes aim to address humans' most pressing social issues like poverty, famine, and disease by solving environmental problems such as water scarcity and pollution. New strategies for coping with environmental issues also involve providing economic incentives that encourage economically powerful nations and industries to act for the common good.

Laurie Duncan, Ph.D.

For More Information

Books

Bixler, Patricia E. Gifford Pinchot. Historic Pennsylvania Leaflet No. 39. Edited by Harold L. Myers. Harrisburg, PA: Pennsylvania Historical & Museum Commission, 1976. Also available at http://www.dep.state.pa.us/dep/PA_EnvHer/pinchot_bio.htm (accessed on September 3, 2004).

McPhee, John. The Control of Nature. New York: Farrar, Straus and Giroux, 1989.

Muir, John. The Yosemite. New York: The Century Company, 1912.

Pipkin, Bernard, W. and D. D. Trent. "Fresh-water Resources." In Geology and the Environment. Pacific Grove, CA: Brooks/Cole, 2001.

Websites

"Conservation: Fresh Water." National Geographic.com.http://magma.nationalgeographic.com/education/gaw/frwater (accessed on September 3, 2004).

Daughtry, Hill. Theplumber.com.http://www.theplumber.com (accessed on September 3, 2004).

"Hetch Hetchy." The Sierra Club.http://www.sierraclub.org/ca/hetchhetchy/history.asp (accessed on September 3, 2004).

United Nations Environment Programme.http://www.unep.org (accessed on September 3, 2004).

United States Department of Agriculture Forest Service.http://www.fs.fed.us (accessed on September 3, 2004).

United States Geological Survey. "Earth's Water." Water Science for Schools.http://ga.water.usgs.gov/edu/mearth.html (accessed on September 3, 2004).

Water Conservation

Freshwater resources

Water consumption

Efficient water utilization efforts

Economic incentives for water conservation

Resources

Water conservation is the use and management of water for the good of all consumers. It is used in agriculture, industry, and the home. Human requirements for agricultural production, flood control, fish and wildlife management, navigation, industrial production, and many other uses have amended natural hydrologic processes.

The hydrosphere refers to that portion of Earth that is made of water, including all oceans, lakes, rivers, streams, glaciers, and underground water. Less than 3% of the water of Earth is freshwater, an amount that includes polar ice caps, glaciers, groundwater, surface water of rivers and freshwater lakes, and even atmospheric water. However, the amount of freshwater useable by people and other members of the biosphere is less than 0.7% of the total (this is water in rivers and lakes, and in the ground). This relatively small amount of available freshwater is recycled and purified by the action of processes within the hydrologic cycle, including evaporation, condensation, precipitation, and percolation through the ground. All life depends on the availability of freshwater.

Of all the freshwater used directly by humans, agricultural irrigation accounts for about 70% of the total. The remainder is used for industrial and domestic purposes. However, these proportions vary widely due to the climatic and economic conditions of the particular locality. Within this century, one-third of the countries situated in areas of water scarcity may encounter severe water shortages. By 2025, two thirds of the world’s population is likely to live in areas of moderate or severe water shortage. The need for more effective conservation of the limited supplies of water that are available for use by people and required by natural ecosystems will intensify as water stress grows.

Freshwater resources

Available freshwater resources are either ground-water or surface water (rivers and lakes). Water that flows on the surface of the land is surface runoff. The relationship among surface runoff, precipitation, evaporation, and percolation is summarized in the following equation:

Surface runoff = precipitation– (evaporation+ percolation)

When surface runoff resulting from rainfall or snowmelt is confined to a relatively narrow, well-defined channel, it is called a river or stream.

Groundwater is that water that has percolated downward through the soil and is present within porous spaces in soil and bedrock. It has been estimated that the global groundwater resource is equivalent to about 34 times the volume of all surface waters (i.e., rivers and lakes) of the world. This resource is present nearly everywhere and has the additional advantages of typically needing no storage or treatment. Utilization does require the construction of a well, sometimes presenting a problem in the most needy locations.

Water utilization efficiency is measured by the ratio of water withdrawal and its subsequent consumption. Water withdrawal is water pumped from rivers, reservoirs, or groundwater wells, and is then transported for use. Water consumption is water that is withdrawn and actually used for some specific purpose. It is then returned to the environment through evaporation, transpiration, discharge to a river or lake, or in some other way.

Water consumption

Water consumption varies greatly among regions due to differences in economic development. The average municipal use in the United States is about 150 gal (568 l) per person per day, though the rate can be higher than 350 gal (1324 l) in some locations. This includes home use for bathing, waste disposal, and gardening, as well as institutional and commercial usage. Per capita (per person) water usage in Asia is only 22 gal (85 l) per day, and just 12 gal (47 l) in Africa.

According to the World Health Organization (WHO) of the United Nations, people have a minimum water requirement of about 5 gal (20 l) per person per day. This is the minimum amount needed for physiological rehydration, cooking, washing, and other subsistence requirements. However, the WHO estimates that nearly two billion people consume contaminated water. This carries a significant risk of developing such water-borne diseases as cholera, dysentery, polio, or typhoid, which kill about 25 million people per year. Both conservation and sanitation are obvious necessities in meeting the huge demand for freshwater.

Because irrigation accounts for 70% of the water used by humans worldwide, achieving a better efficiency of agricultural use is a logical step in advancing water conservation. This can be accomplished by lining water delivery systems with concrete or other impervious materials to minimize loss by leaking during transport, and by using drip-irrigation systems to minimize losses by evaporation. Drip-irrigation systems have been successfully used on fruit trees, certain row-crops, and horticultural plants. Conservation can also be accomplished by improving the efficiency of utilization of water by crops, including the cultivation of plants that are less demanding of moisture.

Efficient water utilization efforts

Subsurface irrigation is an emerging technology with high water-utilization efficiency. Subsurface irrigation uses a drip-irrigation tubing buried 6 to 8 in (15 to 20 cm) underground, with a spacing of 12 to 24 in (30 to 60 cm) between parallel lines. The tubing contains drip outlets that deliver water and nutrients within the root zone at a desired rate. In addition to water conservation, subsurface irrigation has other advantages that overhead sprinklers do not: minimal over watering, fewer disease and aeration problems, less runoff and erosion, fewer weeds, and better protection from vandalism. However, this system is relatively expensive to install. In California, subsurface irrigation has been used on fruit trees, field crops, and lawns, and has achieved water-use savings of about 50%. However, this methodology can, in arid environments, lead to the buildup of soil salinity levels, damaging plants and reducing crop yields. Balancing the water needs of the plant with maintenance of soil quality is an important component of water conservation measures. Technologically advanced irrigation systems now incorporate climate-based controls. These systems utilize meteorological information to determine the need for irrigation and modify the length and duration of irrigation to match the plant’s requirements. Though these systems are currently used primarily on large-scale applications, development of economical models for the small-scale user is underway.

Xeriscaping, or the cultivation of plants requiring little water, is an especially suitable horticultural practice for conserving water in regions with a dry, hot climate. For example, over much of the southwestern United States, more than 50% of the domestic water consumption may be used to irrigate lawns and other horticultural plants that are intolerant of drought. Xeriscaping uses plants such as cacti, succulents, and shrubs of semi-desert habitat (such as trailing rosemary Rosemarinus officinale and rock rose Cistus cobariensis ), which are well-adapted to a hot, dry climate and need little water.

Water conservation can also be advanced by improving other domestic uses of water. One simple conservation practice is to install ultra-low-flush (ULF) toilets and low-flow showerheads in homes and other buildings. A ULF toilet uses only 1.6 gal (6.1 l) per flush, compared to 5 to 7 gal by a standard toilet. Replacing a standard toilet with an ULF saves about 30 to 40 gal (114 to 151 l) of water per day, equivalent to 10,000 to 16,000 gal (37,850 to 60,560 l) per year. More recently, advanced toilets and urinals requiring no water have been developed and are beginning to be utilized on a limited basis.

Another way to conserve the freshwater supply is to desalinize seawater. Desalinization is the removal of salts and other impurities from seawater by either distillation or reverse osmosis (RO), and this method is being increasingly used to provide high-quality water for drinking, cooking, and other domestic uses. In 2004, the world production of desalinated water was at least 40 billion gallons per day (150 billion liters), most of which was produced in Saudi Arabia and other nations of the Gulf of Arabia, where energy costs are relatively low (the cost of desalinated water is highly sensitive to the cost of energy). The largest desalination plant in the world (Shoaiba Desalination Plant) is located in Saudi Arabia, and it uses reverse osmosis to produce half of its country’s drinking water. Saudi Arabia is the largest producer of desalinated water in the world with desalination providing 70% of the country’s drinking water. Desalinization is also practiced in California and Florida, where the cost is about three dollars per thousand gallons, which is four to five times the cost paid for domestic water by typical urban consumers in the United States, and more than 100 times the cost paid by farmers for water for irrigation. The process is also gaining popularity in Spain, Australia, and China.

Widespread recognition of the importance of reusing water has begun to change traditional water use methods. As the value of water increases, users are willing to employ methods that may increase the initial cost of a project, with the hope of regaining those costs through water savings in the future. One of the first of these reuse applications was the irrigation of golf courses and landscaping. In many areas, treated waste-water is diverted from its normal disposal path to be reused in irrigation. This has gained in popularity and is also utilized in small artificial ponds for decorative purposes. Graywater systems capture water that drains from sinks, tubs, laundry, and dishwashers for reuse in irrigation. Graywater systems do not incorporate toilet wastes because of the potential health threat. Dual plumbing is required for such a system and some treatment is required prior to reuse. Though home construction costs are obviously increased by including a graywater system, many have become dedicated believers in the benefits of water reuse, while others question the economic benefit of small-scale systems.

KEY TERMS

Drip irrigation —A method of irrigation utilizing small, low-flow emitters that are located at or above the plant root zone. Designed to reduce the quantity of water lost to evaporation.

Graywater —Used wash water collected from sinks, laundry, etc. that is reused for irrigation. Graywater does not include toilet wastes.

Per capita usage —The amount used by one person in a given amount of time.

Reverse osmosis —A process for purification of water in which water is forced through a semi-permeable membrane, retaining most ions while transmitting the water.

Tiered pricing —A system of pricing in which unit quantities of a commodity are priced with increasingly higher rates, such that, higher rates of usage result in rapidly increasing costs for the consumer.

The widespread application of graywater systems has, however, been hampered by codes and laws that make such systems illegal in many locations.

Economic incentives for water conservation

As the availability of water becomes more restricted, the costs to both the provider and consumer are increased. In a situation unique to the water supply industry, providers are frequently placed in the position of trying to convince consumers to use less of the commodity that they supply. Most large water providers have departments dedicated to education of the public with regard to conservation. In general, these education efforts have been largely ineffective and conservation of freshwater resources has been best achieved through economic incentives. Water providers frequently provide rebates for those consumers that are willing to change from older technology to newer, such as low-flush toilets and modern washing machines, convert to water efficient landscaping, or otherwise demonstrate lower water usage. Greatest effect has been achieved through tiered pricing. In this pricing structure, users are charged higher rates for each successive unit, or block, of water used. The rate structure penalizes heavy users with greatly increased rates. This technique has been shown to be highly effective in reducing overall usage. In Tucson, Arizona, for example, an increasing tiered price structure resulted in decreased usage of 26% over a three-year period. Additionally, some communities have implemented the use of water conservation monitors and water waste hotlines to penalize those that continue to waste the resource. Many communities currently limit the type and size of landscaping, the time and nature of outdoor water use, and in extreme cases, have completely banned outdoor water use during crisis periods.

Throughout history, the availability of water has been a vital factor in the rise and fall of human cultures. This is largely because water is a limiting factor for the carrying capacity for human activities in any region. It is crucial that humans learn to live within the limits of available natural resources, including the supply of fresh water. Because the supply of usable water is finite, the consumption per person must be reduced in regions that are using this resource excessively.

See also Desalination; Water pollution.

Resources

BOOKS

Black, Maggie. Water, Life Force. Toronto, Canada: Between the Lines, 2004.

Editors of I.B. Tauris. A History of Water. London, UK, and New York: I.B. Tauris, 2004.

Hancock P.L., and Skinner B.J., eds. The Oxford Companion to the Earth. Oxford: Oxford University Press, 2000.

Haygarth, P.M., and S.C. Jarvis. Agriculture, Hydrology, and Water Quality. Wallingford, UK, and New York: CABI Publishing, 2002.

Herschy, Reginald, and Rhodes Fairbridge, eds. Encyclopedia of Hydrology and Water Resources. Boston: Kluwer Academic Publishing, 1998.

Kandel, Robert S. Water from Heaven: The Story of Water from the Big Bang to the Rise of Civilization and Beyond. New York: Columbia University Press, 2003.

Lehr, Jay H., ed. Water Encyclopedia. Hoboken, NJ: John Wiley & Sons, 2005.

Lide, D.R., ed. CRC Handbook of Chemistry and Physics Boca Raton: CRC Press, 2001.

McConnell, Robert, and Daniel Abel. Environmental Issues: Measuring, Analyzing, Evaluating. 2nd ed. Englewood Cliffs, NJ: Prentice Hall, 2002.

Oxtoby, David W., et al. The Principles of Modern Chemistry. 5th ed. Pacific Grove, CA: Brooks/Cole, 2002.

Vickers, Amy. Handbook of Water Use and Conservation. Amherst, MA: Waterplow Press, 2001.

OTHER

California Urban Water Conservation Council. “H₂OUSE: Water Saver Home” 2006. <http://www.h2ouse.org/> (accessed November 7, 2006).

“Greywater: What It Is, Ways To Treat It, Ways To Use It.” 2000. <http://www.greywater.com/> (accessed November 7, 2006).

International Food Policy Research Institute. “Domestic Water Supply, Hygiene, And Sanitation.” October 2001. <http://www.ifpri.cgiar.org/2020/focus/focus09/focus09_03.htm> (accessed November 7, 2006).

National Wildlife Federation. “Population, Water & Wildlife: Finding a Balance.” 2001. <http://www.nwf.org/nwfWebAdmin/binaryVault/PWWReport.pdf> (accessed November 7, 2006).

United States Environmental Protection Agency. “How to Conserve Water and Use It Effectively.” March 8, 2006. <http://www.epa.gov/water/you/chap3.html> (accessed November 7, 2006).

United States Environmental Protection Agency. “How We Use Water In These United States.” November 7, 2006. <http://www.epa.gov/water/you/chap1.html> (accessed November 7, 2006).

United States Geological Survey. “Thirsty? How ‘bout a Cool, Refreshing Cup of Seawater?” August 30, 2005. <http://ga.water.usgs.gov/edu/drinkseawater.html> (accessed November 7, 2006).

David Goings

Water conservation

The hydrosphere refers to that portion of the earth that is made of water , including all oceans, lakes, rivers , streams, glaciers , and underground water. Less than 3% of the water of Earth is freshwater , an amount that includes polar ice caps , glaciers, groundwater , surface water of rivers and freshwater lakes, and even atmospheric water. However, the amount of freshwater useable by people and other members of the biosphere is less than 0.5% of the total (this is water in rivers and lakes, and in the ground). This relatively small amount of available freshwater is recycled and purified by the action of processes within the hydrologic cycle , including evaporation , condensation, precipitation , and percolation through the ground. All life depends on the availability of freshwater.

Of all the freshwater used directly by humans, agricultural irrigation accounts for about 70% of the total. The remainder is used for industrial and domestic purposes. However, these proportions vary widely due to the climatic and economic conditions of the particular locality. Within this century, one third of the countries situated in areas of water scarcity may encounter severe water shortages. By 2025, two thirds of the world's population is likely to live in areas of moderate or severe water shortage. The need for more effective conservation of the limited supplies of water that are available for use by people and required by natural ecosystems will intensify as water stress grows.

Freshwater resources

Available freshwater resources are either groundwater or surface water (rivers and lakes). Water that flows on the surface of the land is surface runoff. The relationship among surface runoff, precipitation, evaporation, and percolation is summarized in the following equation:

Surface runoff = precipitation - (evaporation + percolation)

When surface runoff resulting from rainfall or snowmelt is confined to a relatively narrow, well-defined channel, it is called a river or stream.

Groundwater is that water that has percolated downward through the soil and is present within porous spaces in soil and bedrock . It has been estimated that the global groundwater resource is equivalent to about 34 times the volume of all surface waters (i.e., rivers and lakes) of the world. This resource is present nearly everywhere and has the additional advantages of typically needing no storage or treatment. Utilization does require the construction of a well, sometimes presenting a problem in the most needy locations.

Water utilization efficiency is measured by the ratio of water withdrawal and its subsequent consumption. Water withdrawal is water pumped from rivers, reservoirs, or groundwater wells, and is then transported for use. Water consumption is water that is withdrawn and actually used for some specific purpose. It is then returned to the environment through evaporation, transpiration , discharge to a river or lake , or in some other way.

Water consumption

Water consumption varies greatly among regions due to differences in economic development. The average municipal use in the United States is about 150 gal (568 l) per person per day, though the rate can be higher than 350 gal (1324 l) in some locations. This includes home use for bathing, waste disposal, and gardening, as well as institutional and commercial usage. Per capita (per person) water usage in Asia is only 22 gal (85 l) per day, and just 12 gal (47 l) in Africa .

According to the World Health Organization (WHO) of the United Nations, people have a minimum water requirement of about 5 gal (20 l) per person per day. This is the minimum amount needed for physiological rehydration, cooking, washing, and other subsistence requirements. However, the WHO estimates that nearly two billion people consume contaminated water. This carries a significant risk of developing such water-borne diseases as cholera , dysentery , polio, or typhoid, which kill about 25 million people per year. Both conservation and sanitation are obvious necessities in meeting the huge demand for freshwater.

Because irrigation accounts for 70% of the water used by humans worldwide, achieving a better efficiency of agricultural use is a logical step in advancing water conservation. This can be accomplished by lining water delivery systems with concrete or other impervious materials to minimize loss by leaking during transport, and by using drip-irrigation systems to minimize losses by evaporation. Drip-irrigation systems have been successfully used on fruit trees, certain row-crops, and horticultural plants. Conservation can also be accomplished by improving the efficiency of utilization of water by crops , including the cultivation of plants that are less demanding of moisture.

Efficient water utilization efforts

Subsurface irrigation is an emerging technology with high water-utilization efficiency. Subsurface irrigation uses a drip-irrigation tubing buried 6–8 in (15–20 cm) underground, with a spacing of 12–24 in (30–60 cm) between parallel lines. The tubing contains drip outlets that deliver water and nutrients within the root zone at a desired rate. In addition to water conservation, subsurface irrigation has other advantages that overhead sprinklers do not: minimal over watering, fewer disease and aeration problems, less runoff and erosion , fewer weeds, and better protection from vandalism. However, this system is relatively expensive to install. In California, subsurface irrigation has been used on fruit trees, field crops, and lawns, and has achieved water-use savings of about 50%. However, this methodology can, in arid environments, lead to the buildup of soil salinity levels, damaging plants and reducing crop yields. Balancing the water needs of the plant with maintenance of soil quality is an important component of water conservation measures. Technologically advanced irrigation systems now incorporate climate-based controls. These systems utilize meteorological information to determine the need for irrigation and modify the length and duration of irrigation to match the plant's requirements. Though these systems are currently used primarily on large-scale applications, development of economical models for the small-scale user is underway.

Xeriscaping, or the cultivation of plants requiring little water, is an especially suitable horticultural practice for conserving water in regions with a dry, hot climate. For example, over much of the southwestern United States, more than 50% of the domestic water consumption may be used to irrigate lawns and other horticultural plants that are intolerant of drought . Xeriscaping uses plants such as cacti, succulents, and shrubs of semi-desert habitat (such as trailing rosemary Rosemarinus officinale and rock rose Cistus cobariensis), which are well-adapted to a hot, dry climate and need little water.

Water conservation can also be advanced by improving other domestic uses of water. One simple conservation practice is to install ultra-low-flush (ULF) toilets and low-flow showerheads in homes and other buildings. A ULF toilet uses only 1.6 gal (6.1 l) per flush, compared to 5–7 gal by a standard toilet. Replacing a standard toilet with an ULF saves about 30–40 gal (114–151 l) of water per day, equivalent to 10,000–16,000 gal (37,850–60,560 l) per year. More recently, advanced toilets and urinals requiring no water have been developed and are beginning to be utilized on a limited basis.

Another way to conserve the freshwater supply is to desalinize seawater. Desalinization is the removal of salts and other impurities from seawater by either distillation or reverse osmosis (RO), and this method being increasingly used to provide high-quality water for drinking, cooking, and other domestic uses. In 1993, the world production of desalinated water was about 3.5 billion gallons per day (13 billion liters), most of which was produced in Saudi Arabia and other nations of the Gulf of Arabia, where energy costs are relatively low (the cost of desalinated water is highly sensitive to the cost of energy). Desalinization is also practiced in California and Florida, where the cost is about three dollars per thousand gallons, which is four to five times the cost paid for domestic water by typical urban consumers in the United States, and more than 100 times the cost paid by farmers for water for irrigation.

Widespread recognition of the importance of reusing water has begun to change traditional water use methods. As the value of water increases, users are willing employ methods that may increase the initial cost of a project, with the hope of regaining those costs through water savings in the future. One of the first of these reuse applications was the irrigation of golf courses and landscaping. In many areas, treated wastewater is diverted from its normal disposal path to be reused in irrigation. This has gained in popularity and is also utilized in small artificial ponds for decorative purposes. Greywater systems capture water that drains from sinks, tubs, laundry, and dishwashers for reuse in irrigation. Greywater systems do not incorporate toilet wastes because of the potential health threat. Dual plumbing is required for such a system and some treatment is required prior to reuse. Though home construction costs are obviously increased by including a greywater system, many have become dedicated believers in the benefits of water reuse, while others question the economic benefit of small-scale systems. The widespread application of greywater systems has, however, been hampered by codes and laws that make such systems illegal in many locations.

Economic incentives for water conservation

As the availability of water becomes more restricted, the costs to both the provider and consumer are increased. In a situation unique to the water supply industry, providers are frequently placed in the position of trying to convince consumers to use less of the commodity that they supply. Most large water providers have departments dedicated to education of the public with regard to conservation. In general, these education efforts have been largely ineffective and conservation of freshwater resources has been best achieved through economic incentives. Water providers frequently provide rebates for those consumers that are willing to change from older technology to newer, such as low-flush toilets and modern washing machines, convert to water efficient landscaping, or otherwise demonstrate lower water usage. Greatest effect has been achieved through tiered pricing. In this pricing structure, users are charged higher rates for each successive unit, or block, of water used. The rate structure penalizes heavy users with greatly increased rates. This technique has been shown to be highly effective in reducing overall usage. In Tucson, Arizona, an increasing tiered price structure resulted in decreased usage of 26% over a three-year period. Additionally, some communities have implemented the use of water conservation monitors and water waste hotlines to penalize those that continue to waste the resource. Many communities currently limit the type and size of landscaping, the time and nature of outdoor water use, and in extreme cases, have completely banned outdoor water use during crisis periods.

Throughout history, the availability of water has been a vital factor in the rise and fall of human cultures. This is largely because water is a limiting factor for the carrying capacity for human activities in any region. It is crucial that humans learn to live within the limits of available natural resources, including the supply of fresh water. Because the supply of usable water is finite, the consumption per person must be reduced in regions that are using this resource excessively.

See also Desalination; Water pollution.

Resources

books

Buzzelli, B. How to Get Water Smart: Products and Practices for Saving Water in the Nineties. Santa Barbara, CA: Terra Firma Publishing, 1991.

Clarke, R. Water: The International Crisis. Cambridge: MIT Press, 1993.

Keller, Edward. Environmental Geology. Upper Saddle River, NJ: Prentice-Hall, Inc., 2000.

Morrison, Jason I., Sandra L. Postel, and Peter H. Gleick. The Sustainable Use of Water in the Lower Colorado River Basin. Oakland, CA: Pacific Institute for Studies in Development, Environment, and Security, 1996.

Postel, Sandra L. Last Oasis: Facing Water Scarcity. W.W. Norton and Co., 1997

van der Leeden, Frits, Fred L. Troise, and David K. Todd. The Water Encyclopedia. Chelsea: Lewis Publishers, Inc., 1990.

Vickers, Amy. Handbook of Water Use and Conservation. Amherst, MA: Waterplow Press, 2001.

Yudelman. M., et al. New Vegetative Approaches to Soil and Water Conservation. Washington, DC: World Wildlife Fund, 1990.

periodicals

Graves, William, ed. "Water: The Power, Promise, and Turmoil of North America's Fresh Water." Special Edition National Geographic Special Edition (November 1993): 1–119.

Postel, Sandra L. "Plug the Leak, Save the City." International Wildlife. 23 (January-February 1993): 38–41.

Reisner, Marc. "Unleash the Rivers." Time Magazine Special Edition (April-May 2000): 66–71.

other

California Urban Water Conservation Council. "H2OUSE: Water Saver Home" 2002 [cited October 20, 2002]. <http://www.h2ouse.org/>.

"Greywater: What It Is, Ways To Treat It, Ways To Use It." 2000 [cited October 20, 2002]. <http://www.greywater.com/>.

International Food Policy Research Institute. "Domestic Water Supply, Hygiene, And Sanitation." October 2001 [cited October 20, 2002] <http://www.ifpri.cgiar.org/2020/focus/focus09/focus09_03.htm.

National Wildlife Federation. "Population, Water & Wildlife: Finding a Balance." 2001 [cited October 20, 2002]. <http://www.nwf.org/nwfWebAdmin/binaryVault/PWWR eport.pdf>.

United Nations Department of Economic and Social Affairs,Division for Sustainable Development. "Facts About Water." 2002 [cited October 20, 2002]. <http://www.johannesburgsummit.org/html/media_info/press releases_factsheets/wssd4_water.pdf>.

United States Environmental Protection Agency. "How to Conserve Water and Use It Effectively." June 7, 2002 [cited October 20, 2002]. <http://www.epa.gov/water/you/chap3.html>.

United States Environmental Protection Agency. "How We Use Water In These United States." June 7, 2002 [cited October 20, 2002]. <http://www.epa.gov/water/you/chap1.html>.

United States Geological Survey. "Thirsty? How 'bout a Cool, Refreshing Cup of Seawater?" June 12, 2001 [cited October 20, 2002]. <http://ga.water.usgs.gov/edu/drinkseawater.html>.

David Goings

KEY TERMS

Drip irrigation

—A method of irrigation utilizing small, low-flow emitters that are located at or above the plant root zone. Designed to reduce the quantity of water lost to evaporation.

Grey water

—Used wash water collected from sinks, laundry, etc. that is reused for irrigation. Grey water does not include toilet wastes.

Per capita usage

—The amount used by one person in a given amount of time.

Reverse osmosis

—A process for purification of water in which water is forced through a semipermeable membrane, retaining most ions while transmitting the water.

Tiered pricing

—A system of pricing in which unit quantities of a commodity are priced with increasingly higher rates, such that, higher rates of usage result in rapidly increasing costs for the consumer.

Water conservation

Seventy-one percent of the earth's surface is covered by water—an area called the hydrosphere, which makes up all of the oceans and seas of the world. Only 3% of the earth's entire water is freshwater. This includes Arctic and Antarctic ice, groundwater , and all the rivers and freshwater lakes. The amount of usable freshwater is only about 0.003% of the total. To put this small percentage in perspective, if the total water supply is equal to one gallon, the volume of the usable freshwater supply would be less than one drop. This relatively small amount of freshwater is recycled and purified by the hydrologic cycle , which includes evaporation, condensation, precipitation, runoff , and percolation . Since most of life on earth depends on the availability of freshwater, one can say "water is life."

Worldwide, agricultural irrigation uses about 80% of all freshwater. Cooling water for electrical power plants , domestic consumption, and other industry use the remaining 20%. This figure varies widely from place to place. For example, China uses 87% of its available water for agriculture. The United States uses 40% for agriculture, 40% for electrical cooling, 10% for domestic consumption, and 10% for industrial use.

Water conservation may be accomplished by improving crop water utilization efficiency and by decreasing the use of high-water-demanding crops and industrial products. The table shows the amount of water, in pounds, required to produce one pound of selected crops and industrial products (one gal = 7.8 lb).

Freshwater sources are either surface water (rivers and lakes) or groundwater. Water that flows on the surface of the land is called surface runoff. The relationship between surface runoff, precipitation, evaporation, and percolation is shown in the following equation: Surface runoff = precipitation - (evaporation + percolation): When surface runoff resulting from rainfall or snowmelt is confined to a well-defined channel it is called a river or stream runoff

Groundwater is surface water that has permeated through the soil particles and is trapped among porous soils and rock particles such as sandstone or shale. The upper zone of saturation , where all pores are filled with water, is the water table . It is estimated that the groundwater is equal to 40 times the volume of all earth's freshwater including all the rivers and freshwater lakes of the world.

The movement of groundwater depends on the porosity of the material that holds the water. Most groundwater is held within sedimentary aquifers. Aquifers are underground layers of rock and soil that hold and produce an appreciable amount of water and can be pumped economically.

Water utilization efficiency is measured by water withdrawal and water consumption. Water withdrawal is water that is pumped from rivers, reservoirs, or groundwater wells , and is transported elsewhere for use. Water consumption is water that is withdrawn and returned to its source due to evaporation or transpiration .

Water consumption varies greatly throughout the world. A conservative figure for municipal use in the United States is around 150 gal (568 L) per person per day. This includes home use for bathing, waste disposal, and landscape in addition to commercial and industrial use. The total water demand per person is around 4,500 gal (17,000 L) per person per day when one accounts for the production of food, fiber, and fuel. The consumptive use world wide is considerably less than that for the United States.

According to the United Nations World Health Organization (WHO), 5 gal (18 L) per person per day is considered a minimum water requirement. The majority of the people in the undeveloped world are unable to obtain the five gallon per day minimum requirement. The WHO estimates that nearly two billion people in the world risk consuming contaminated water. Waterborne diseases such as polio, typhoid, dysentery, and cholera kill nearly 25 million people per year. In order to meet this demand for freshwater, conservation is an obvious necessity.

Since irrigation consumes 80% of the world's usable water, improvements in agricultural use is the logical first step in water conservation. This can be accomplished by lining water delivery systems with concrete or other impervious materials to minimize deep percolation or by using drip irrigation systems to minimize evaporation losses. Drip irrigation systems have been successfully used on fruit trees, shrubs, and landscape plants.

Subsurface irrigation is an emerging technology with extremely high water utilization efficiency. Subsurface irrigation uses a special drip irrigation tubing that is buried 6–8 in (15–20 cm) underground with 12–24 in (26–50 cm) between lines. The tubing contains emitters, or drip outlets, that deliver water and dissolved nutrients at the plant's root zone at a desired rate. In addition to water conservation, subsurface irrigation has several advantages that overhead sprinklers do not: no overwatering, no disease or aeration problems, no runoff or erosion , no weeds, and no vandalism. Subsurface irrigation in California has been used on trees, field crops, and lawns with up to 50% water savings.

Xeriscape, the use of low water consuming plants, is a most suitable landscape to conserve water, especially in dry, hot urban regions such as the Southwestern United States, where approximately 50% of the domestic water consumption is used by lawns and non-drought tolerant landscape. Plants such as cacti and succulents, ceanothus, arctostaphylos, which is related to foothill manzanita, trailing rosemary (Rosemarinus officinale ), and white rock rose (Cistus cobariensis ) adapt well to hot, dry climates and help conserve water.

In addition to improving irrigation techniques, water conservation can be accomplished by improving domestic use of water. Such a conservation practice is the installation of the ultra-low-flush (ULF) toilets in homes and commercial buildings. A standard toilet uses 5–7 gal (19–26 L) of water per flush, while the ultra-low-flush toilet uses 1.5 gal (5.7 L). Research in Santa Monica, California, shows that replacing a standard toilet with an ULF saves 30–40 gal (114–151 L) of water per day, which is equivalent to 10,000–16,000 gal (37,850–60,500 L) per year.

Another way to conserve the freshwater supply is to extract freshwater from sea water by desalinization . Desalinization, the removal of soluble salts and other impurities from seawater by distillation or reverse osmosis (RO), is becoming an increasingly acceptable method to provide high quality pure water for drinking, cooking, and other home uses. It is estimated that the 1993 world production of desalinated water is about 3.5 billion gal (13 billion L) per day. Most desalinated water is produced in Saudi Arabia, Persian Gulf Nations, and, more recently, in California. The cost of desalinated water depends upon the cost of energy. In the United States, it is about three dollars per thousand gallons, which is four to five times the cost paid by urban consumers and over 100 times the cost paid by farmers for irrigation water. The idea of using desalinated water for irrigation is, currently, cost prohibitive.

Water has played a vital role in the rise and fall of human cultures throughout history. The availability of usable water has always been a limiting factor for a region's ecological carrying capacity . It is important that humans learn to live within the limit of available natural resources . Conservation of water alone will not extend the natural carrying capacity for an indefinite period of time. Since the supply of available and usable water is finite, the consumption per person must be reduced. A permanent solution to the water shortage problem can be accomplished by living within the ecosystem carrying capacity or by reducing the number of consumers through effective control of population growth .

[Muthena Naseri ]

RESOURCES

BOOKS

Buzzelli, B. How to Get Water Smart: Products and Practices for Saving Water in the Nineties. Santa Barbara: Terra Firma Publishing, 1991.

Clarke, R. Water: The International Crisis. Cambridge: MIT Press, 1993.

Yudelman. M., et al. New Vegetative Approaches to Soil and Water Conservation. Washington, DC: World Wildlife Fund, 1990.

PERIODICALS

Postel, S. "Plug the Leak, Save the City." International Wildlife 23 (January-February 1993): 38–41.

Water Conservation

Introduction

It is easy for some people in developed nations to take their water supply for granted. But water is essential to life and, according to the United Nations, one billion people around the world lack access to safe drinking water and 2.6 billion people lack adequate sanitation. Therefore, there is not enough water in circulation to even meet people’s basic needs. Added to this, agriculture and industry rely upon an adequate water supply for productivity. Therefore, water is a precious resource and its conservation is important.

There are many simple ways in which water can be conserved by the individual. Authorities, such as the U.S. Environmental Protection Agency (EPA), have various schemes to encourage a responsible attitude towards water consumption. Technical advances can aid water conservation, such as the low-volume toilet and new ways of irrigating crops. Water conservation, like energy efficiency, brings big benefits in terms of improving quality of life and protecting the environment.

Historical Background and Scientific Foundations

Forty-five countries around the world suffer from frequent water shortages, and in many other places drought can make water supplies uncertain. Much water is wasted though leaks in pipes, toilets, taps, and irrigation systems. Meanwhile, the growing world population and increasing industrialization increase the demand for freshwater. Without some kind of controlled reduction in this demand through water conservation, pressure on water supplies could have a widespread effect on human health and productivity.

Water conservation relies upon a mixture of behavioral change and technical advances. There are many simple ways in which individuals can save water, from fixing leaks and having shorter showers, to collecting and reusing water for the garden. Water conservation efforts should be driven by an awareness of which activities use the most water. Toilet flushing accounts for about 47% of typical household water use in the United States, followed by 31% for bathing, and 20% for laundry and dishwashing.

Therefore, low-volume toilets can make a difference to domestic water consumption. Prior to 1992, when these were introduced, a typical flush took six gallons of water but now it takes only 1.6 gallons. There are also water-efficient dishwashers and washing machines as well as low-volume shower heads. Wastewater can be reclaimed and recycled, with several cities now using purified sewage effluent. Agriculture is the greatest consumer of water worldwide and some practices are very wasteful. In standard irrigation, much water is lost through evaporation or runoff. But drip irrigation helps conserve water, by releasing controlled amounts of water just above plant roots, so that nearly all of the water is used by the plant.

Awareness of the need for water conservation is being increased by the water footprint concept, which has been developed by researchers at the University of Twente in the Netherlands. The water footprint can be applied to an individual, a business, or a nation, and it refers to the volume of water used in the production of goods and services used. For instance, it takes about 4,227 gallons (16,000 liters) of water to produce 2.2 pounds (1 kilogram) of beef, and 37 gallons (140 liters) of water to produce a cup of coffee.

Impacts and Issues

Wasting water not only makes shortages worse, it also contributes to water pollution. For example, diverting

WORDS TO KNOW

DRIP IRRIGATION: Slow, localized application of water just above the soil surface.

SEWAGE: Waste and wastewater discharged from domestic and commercial premises.

WATER FOOTPRINT: The total volume of water used to produce goods and services consumed by an individual, business or nation.

natural water supplies by building dams traps sediment, which concentrates pollutants and reduces dissolves oxygen. The more water people use, the more dirty wastewater is produced, which flows into natural water supplies, compromising their purity.

Water conservation improves the overall quality of the water supply and the environment in many ways. The sewage system is less liable to failure through overloading. More efficient irrigation means less polluted runoff from agricultural land. Natural pollution filters like wetlands are less likely to be dried up or depleted, while reduced need to build dams and reservoir preserves species’ habitats. Moreover, using less hot water means using less electricity, which benefits both the consumer and the environment.

See Also Drought; Industrial Water Use; Irrigation; Runoff; Water Resources; Water Supply and Demand

BIBLIOGRAPHY

Books

Cunningham, W.P., and A. Cunningham. Environmental Science: A Global Concern. New York: McGraw-Hill International Edition, 2008.

Web Sites

U.S. Environmental Protection Agency (EPA). “WaterSense®.” January 25, 2008. http://www.epa.gov/watersense/water/index.htm (accessed March 23, 3008).

Waterfootprint.org. “Water Footprint.” http://www.waterfootprint.org/?page=files/home (accessed March 23, 2008)