World Water Day: UN urges sustainable use of Earth's most critical resource

 How Can We Use Water More Sustainably

 CONCEPT 11-3 We can use water more sustainably by cutting water waste, raising water prices, slowing population growth, and protecting aquifers, forests, and other ecosystems that store and release water.

 Reducing Water Waste Has Many Benefits

Mohamed El-Ashry of theWorld Resources Institute estimates that 65-70% of the water people use throughout the world is lost through evaporation, leaks, and other losses, and global warming is expected to increase evaporation in many parts of the world. The United States does slightly better but still loses about half of the water it withdraws.

 El-Ashry believes it is economically and technically feasible to reduce such water losses to 15%, thereby meeting most of the world’s water needs for the foreseeable future.

 This win–win solution would decrease the burden on wastewater plants and reduce the need for expensive dams and water transfer projects that destroy wildlife habitats and displace people. It would also slow depletion of groundwater aquifers and save both energy and money.

 According to water resource experts, the main cause of water waste is that we charge too little for water. Such under pricing is mostly the result of government subsidies that provide irrigation water, electricity, and diesel fuel for farmers to pump water from rivers and aquifers at below-market prices.

 Because these subsidies keep water prices low, users have little or no financial incentive to invest in water saving technologies. According to water resource expert Sandra Postel, “By heavily subsidizing water, governments give out the false message that it is abundant and can afford to be wasted-even as rivers are drying up, aquifers are being depleted, fisheries are collapsing, and species are going extinct.”

 However, farmers, industries, and others benefiting from government water subsidies argue that the subsidies promote settlement and farming of arid, unproductive land, stimulate local economies, and help keep the prices of food, manufactured goods, and electricity low.

 Most water resource experts believe that when water scarcity afflicts many areas in this century, governments will have to make the unpopular decision to raise water prices. China did so in 2002 because it faced water shortages in most of its major cities with rivers running dry and water tables falling in key agricultural areas.

Higher water prices encourage water conservation but make it difficult for low-income farmers and city dwellers to buy enough water to meet their needs.

 When South Africa raised water prices, it established lifeline rates that give each household a set amount of free or low-priced water to meet basic needs. When users exceed this amount, the price rises as water use increases-a user-pays approach.

 The second major cause of water waste is too few government subsidies for improving the efficiency of water use. A basic rule of economics is that you get more of what you reward. Withdrawing subsidies that encourage water waste and providing subsidies for efficient water use would sharply reduce water waste. There should be two goals: greatly improve the efficiency of irrigation that accounts for 70% of the world’s water use and use inexpensive means to collect rainwater and pipe it to where it is needed.

 We Can Greatly Cut Water Waste in Irrigation

About 60% of the irrigation water applied throughout the world does not reach the targeted crops. Most irrigation systems obtain water from a groundwater well or a surface water source. The water then flows by gravity through unlined ditches in crop fields so the crops can absorb it. This flood irrigation method delivers far more water than is needed for crop growth and typically loses 40% of the water through evaporation, seepage, and runoff. This wasteful method is used on 97% of China’s irrigated land.

More efficient and environmentally sound irrigation technologies can greatly reduce water demands and water waste on farms by delivering water more precisely to crops-a more-crop-per-drop strategy. For example, the center-pivot, low-pressure sprinkler uses pumps to spray water on a crop. Typically, it allows 80% of that water to reach crops. Low-energy, precision application (LEPA) sprinklers, another form of center pivot irrigation, put 90–95% of the water where crops need it.

Drip or trickle irrigation, also called micro irrigation, is the most efficient way to deliver small amounts of water precisely to crops. It consists of a network of perforated plastic tubing installed at or below the ground level. Small pinholes in the tubing deliver drops of water at a slow and steady rate, close to the roots of individual plants.

Current drip irrigation systems are costly but they drastically reduce water waste, with 90–95% of the water input reaching the crops, and they increase crop yields by 20–90% over conventional gravity flow systems.

By using less water, they also reduce the amount of salt that irrigation water leaves in the soil. Increased use of an inexpensive drip irrigation system developed by the nonprofit International Development Enterprises (IDE) will raise crop yields in water-short areas and help lift poor families out of poverty.

Drip irrigation is used on just over 1% of the world’s irrigated crop fields and 4% of those in the United States. This percentage rises to 90% in Cyprus, 66% in Israel, and 13% in California. If water were priced closer to the value of the ecological services it provides and if government subsidies that encourage water waste were reduced or eliminated, water experts say that drip irrigation would quickly be used to irrigate most of the world’s crops.

 RESEARCH FRONTIER

Developing more efficient and affordable irrigation systems is other ways to reduce water waste in irrigating crops. Since 1950, Israel has used many of these techniques to slash irrigation water waste by 84% while irrigating 44% more land. Israel now treats and reuses 30% of its municipal sewage water for crop production and plans to increase this to 80% by 2025.

The government also gradually eliminated most water subsidies to raise Israel’s price of irrigation water to one of the highest in the world. Israelis also import most of their wheat and meat and concentrate on growing fruits, vegetables, and flowers that need less water.

Irrigation systems do not have to be complex and expensive. Many of the world’s poor farmers use small-scale and low-cost traditional technologies such as human-powered treadle pumps to pump groundwater close to the earth’s surface through irrigation ditches.

Rainwater harvesting is another simple and inexpensive way to provide water for drinking and growing crops throughout most of the world. It involves using pipes from rooftops and mini-reservoirs to catch rainwater.

In southern Australia, more than 40% of households use rainwater stored in tanks as their main source of drinking water. In Germany, half a million households and buildings harvest rainwater.

Poor farmers can also capture rainfall that would otherwise run off the land and store it in shallow aquifers, ponds, and water tanks for use during dry spells. According to a 2006 report by the U.N. Environment Programme (UNEP), harvesting rainfall in Africa and other parts of the world is an underused and cheap way to provide water compared to the costs of building dams or systems for piping drinking water to homes.

Saving rainwater can also save poor women and children from having to spend hours a day fetching water.

Africa is generally viewed as a dry continent but overall it has more water resources per capita than Europe. The UNEP estimates that Kenya has enough rainfall each year to supply 6 or 7 times its current population of 34 million. Increased rainwater harvesting in Ethiopia, where half of its 77 million people suffer from hunger and malnutrition, could supply 520 million people a year with water.

 We Can Cut Water Waste in Industry and Homes

The chemical, paper and pulp, oil, coal, primary metals, and food processing industries use almost 90% of the water used by industry in the United States. Some of these industries recapture, purify, and recycle water to reduce their water use and water treatment costs.

However, most industrial processes could be redesigned to use much less water. Flushing toilets with water (most of it clean enough to drink) is the single largest use of domestic water. Since 1992, U.S. government standards require new toilets to use no more than 6.1 liters (1.6 gallons) of water per flush. Models that use 4.8 liters (1.28 gallons) are available. William McDonough has designed a toilet with a bowl so smooth that nothing sticks to it, including bacteria. Only a light mist is needed to flush it. Low-flow showerheads can cut shower water flow in half, save about 19,000 liters (5,000 gallons) per person each year, and reduce water bills.

According to U.N. studies, 40–60% of the water supplied in nearly all of the world’s megacities in developing countries is lost mostly through leakage of water mains, pipes, pumps, and valves. Even in advanced industrialized countries such as the United States these losses average 10–30%. Water experts say that fixing these leaks should be a high government priority that would cost less than building dams or importing water.

Many homeowners and businesses in water-short areas are using drip irrigation and are copying nature by replacing green lawns with native vegetation. This win–win approach, called Xeriscaping (pronounced “ZEER-i-scaping”), reduces water use by 30–85% and sharply reduces needs for labor, fertilizer, and fuel. It also reduces water and air pollution and yard wastes.

About 50–75% of the slightly dirtied water from bathtubs, showers, sinks, dishwashers, and clothes washers in a typical house could be stored in a holding purifies water by recycling, and thus follows one of the four scientific principles of sustainability.

A major cause of excessive water use and waste in homes and industries is under pricing (Concept 11-3). Many water utility and irrigation authorities charge a flat fee for water use and some charge less for the largest users of water. About one-fifth of all U.S. public water systems do not have water meters and charge a single low rate for almost unlimited use of high-quality water. Also, many apartment dwellers have little incentive to conserve water because water use charges are included in their rent. When the U.S. city of Boulder, Colorado, introduced water meters, water use per person dropped by 40%. GREEN

 CAREER: Water conservation specialist

Currently, we use large amounts of freshwater good enough to drink to flush away industrial, animal, and household wastes. According to the FAO, if current trends continue, within 40 years we will need the world’s entire reliable flow of river water just to dilute and transport the wastes we produce. We could save much of this water by using systems that mimic the way nature deals with wastes. One way to do this would be to return the nutrient rich sludge produced by conventional waste treatment plants to the soil as a fertilizer, instead of using freshwater to transport it. Banning the discharge of industrial toxic wastes into municipal sewer systems would make this feasible. Another way is to rely more on waterless composting toilets that convert human fecal matter to a small amount of dry and odorless soil-like humus material that can be removed from a composting chamber every year or so and returned to the soil as fertilizerWe

 Need to Use Water More Sustainably

Sustainable water use is based on the commonsense principle stated in an old Inca proverb: “The frog does not drink up the pond in which it lives.” lists ways to implement this principle by using water more sustainably (Concept 11-3).

Each of us can help bring about such a blue revolution by using and wasting less water. As with other problems, the solution starts with thinking globally and acting locally.

 SOLUTIONS

 Reducing Irrigation Water Waste

 Line canals bringing water to irrigation ditches

 Irrigate at night to reduce evaporation

 Monitor soil moisture to add water only when necessary

 Grow several crops on each plot of land (polyculture)

 Encourage organic farming

 Avoid growing water-thirsty crops in dry areas

 Irrigate with treated urban waste water

 Import water-intensive crops and meat

  * Methods for reducing water waste in irrigation.

 Question: Which two of these solutions do you think are the most important? Why?

  SOLUTIONS

 Reducing Water Waste

 Redesign manufacturing processes to use less water

 Recycle water in industry

 Landscape yards with plants that require little water

 Use drip irrigation

 Fix water leaks

 Use water meters

 Raise water prices

 Use waterless composting toilets

 Require water conservation in water-short cities

 Use water-saving toilets, showerheads, and front-loading clothes washers

 Collect and reuse household water to irrigate lawns and nonedible plants

 Purify and reuse water for houses, apartments, and office buildings

 * Methods for reducing water waste in industries, homes, and businesses.

 Question: Which three of these solutions do you think are the most important? Why?

  SOLUTIONS

 Sustainable Water Use

 Waste less water and subsidize water conservation

 Do not deplete aquifers

 Preserve water quality

 Protect forests, wetlands, mountain glaciers, watersheds, and other natural systems that store and release water

 Get agreements among regions and countries sharing surface water resources

 Raise water prices

 Slow population growth

  * Methods for achieving more sustainable use of the earth’s water resources (Concept 11-3). Question: Which two of these solutions do you think are the most important? Why?

  WHAT CAN YOU DO?

 Water Use and Waste

 Use water-saving toilets, showerheads, and faucet aerators.

 Shower instead of taking baths, and take short showers.

 Repair water leaks.

 Turn off sink faucets while brushing teeth, shaving, or washing.

 Wash only full loads of clothes or use the lowest possible water-level setting for smaller loads.

 Use recycled (gray) water for watering lawns and houseplants and for washing cars.

 Wash a car from a bucket of soapy water, and use the hose for rinsing only.

 If you use a commercial car wash, try to find one that recycles its water.

 Replace your lawn with native plants that need little if any watering.

 Water lawns and yards in the early morning or evening.

 Use drip irrigation and mulch for gardens and flowerbeds.

  * Individuals matter: ways in which you can reduce your use and waste of water. Visit www.h2ouse.org  for an array of water-saving tips from the EPA and the California Urban Water Conservation Council that can be used anywhere.

Question: Which four of these actions do you think are the most important? Why?