Water Use and Management

Chapter 11Section 2

Objectives

• Identify patterns of global water use.• Explain how water is treated so that it can be

used for drinking.• Identify how water is used in homes, in industry,

and in agriculture.• Describe how dams and water diversion projects

are used to manage freshwater resources.• Identify at least five ways that water can be

conserved.

Global Water Use

Europe is the only continent that uses more water for industry than for agriculture

Global water use

• Three major uses for water – residential use, agricultural use, and industrial use.

• Most of the water used world is used to irrigate crops. In Asia, agriculture accounts for more than 80% of water use, whereas it accounts for only 38% of water use in Europe. Industry accounts for about 19% of the water used in the world. The highest percentage of industrial water use occurs in Europe and North America. Globally, about 8% of water is used by households for activities such as drinking and washing.

Real life connection

• Where does your tap wter comes from?• Does your community’s water come mainly

from surface water or groundwater?• Have you ever visited your local water

treatment plant?

Residential Water USe

• There are striking differences in residential water use throughout the world. For example, the average person in the United States uses about 300 L of water every day. But in India, the average person uses only 41 L of water every day. In the United States only about half of residential water use is for activities inside the home, such as drinking, cooking, washing, and toilet flushing. The remainder of the water used residentially is used outside the home for activities such as watering lawns and washing cars.

Daily Water Use in the United States (per person)

Daily water use in the United States per person

Use water (L)

Lawn watering and pools 95Toilet flushing 90Bathing 70Brushing with water running 10Cleaning (inside and Outside) 20Cooking and drinking 10Other 5

Make a bar graph of the information shown in the above table.

Activity: World water Resources

• Choose a country and investigate its water resources. What percentage of water is used by households, by industry, and by agriculture?

• What are the country’s water resources?• What are the major threats to the country’s

water supply?• Share your information with your partner.

Drinking Water Treatment

Drinking Water Treatment• First filtration: the source water supply is filtered to remove large organisms

and trash.• Coagulation: alum is rapidly mixed into the water and forms sticky globs

called flocs. Bacteria and other impurities cling to the flocs, which settle to the bottom of the tank.

• Second filtration: layers of sand, gravel, and hard coal filter the remaining impurities.

• Chlorination: chlorine is added to prevent bacteria from growing in the water.

• Aeration: air is forced through the water to release unwanted gases, which reduces odor and improves taste.

• Additional treatment: in some communities, fluoride may be added to prevent tooth decay. Sodium compounds or lime may also be added to soften hard water. Treated water is then pumped from storge tanks to homes and business.

Industrial Water USe

• Industry accounts for 19% of water used in the world. Water is used to manufacture goods, to dispose of waste, and to generate power. Vast amounts of water are required to produce computer chips and semiconductors.

• Most of the water used in industry is used to cool power plants. Power-plant cooling system usually pump water from a surface water source such as a river or lake, carry the water through pipes in a cooling tower, and then pump the water back into the source. The water that is returned is usually is warmer than the source, but it is generally clean and can be used again.

Agricultural Water Use• Agriculture accounts for 67 percent of the water used in the world.

Plants require a lot of water to grow, and as much as 805 of the water used in agriculture evaporates and never reaches plant roots.

• IRRIGATION• Fertile soil is sometimes found in areas of the world that do not

have abundant rainfall. In regions where rainfall is inadequate, extra water can be supplied by irrigation. Irrigation is a method of providing plants with water from sources other than direct precipitation. The earliest form of irrigation involved flooding fields with water from nearby river.

• Many different irrigation techniques are used today. For example, some crops, such as cotton, are irrigated by shallow, water filled ditches.

Agricultural Use

In the United States, high -pressure overhead sprinklers are the most common form of irrigation. This method of irrigation is inefficient because nearly half the water evaporates and never reaches the plant roots.

Irrigation system that use water more efficiently are becoming more common.

Drip Irrigation

Water Management Projects

The Spanish Aqueduct

Nearly two thousand years ago, the Romans built aqueducts, huge canals that brought water from the mountains to the dry areas of France and Spain. One such aqueduct is seen below. Water management projects, such as dams and water diversion canals, are designed to meet the demands of the people who live in areas where the natural distribution of surface water is inadequate.

Goals of Water Management Projects

• Bringing in water to make a dry area habitable.

• Creating a reservoir for recreation or drinking water

• Generating electric power• Irrigation purposes

Water Diversion Projects• To supply dry regions with water, all or part of a river can be diverted

into canals that carry water across great distances.

The above figure shows a canal that diverts the Owens River in California to provide drinking water for Los Angeles.

Diversion Project on Colorado River

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• The Colorado river begins as a glacial stream in the rocky mountains and quickly grows larger as other streams feed into it. As the river flows out, however, it is divided to meet the needs of seven western states. Colorado river’s water is diverted for irrigation, and drinking water in states such as Arizona, Utah, and California and runs dry before it reaches Mexico and flows into gulf of California.

Dams and Reservoir• A dam is a structure built across a river to control the river’s flow. When

a river is dammed an artificial lake or reservoir is formed behind the dam. Water from reservoir can be used for flood control, drinking water, irrigation, recreation, and industry. Dams are also used to generate electrical energy. Hydroelectric dams use the power of flowing water to turn a turbine that generates electrical energy.

CONSEQUENCES OF CONSTRUCTION OF DAMS

• When the land behind a dam is flooded, people are often displaced and entire ecosystem can be destroyed.

• Dams also affect the land below them.• As a river enters a reservoir, it slows down and deposits

some of the sediment it carries. This fertile sediment builds up behind the dam instead of enriching the land farther down the river. As a result, the farmland below a dam may become less productive.

• If the dam bursts, people along the river can be killed.

IN DEVELOPING COUNTRIES LIKE Brazil, India, and China the construction of large dams continues.

Water Conservation at home• Check for leaks , especially faulty washers, and repair them!• Fit water conserving devices .Many commonly used appliances can be

modified to conserve water or bought specifically for their water conserving qualities:

• Spray taps and faucet aerators are an alternative to steady flow taps enabling a smaller volume of water to achieve the same results.

• Low flow shower heads can be fitted to maximise water coverage and minimise water volume.

• In the toilet: By adding a plastic bottle filled with water, and sealed, inside your toilet cistern or by adjusting your ballcock, the amount of water used per flush can be reduced to a minimum. Alternatively a dual flush toilet system can be fitted which discharges a small volume of water for liquid waste and a larger volume for solid waste, efficient flushing depends upon the velocity of the water rather than the volume which tends to be grossly out of proportion with the waste that the water flushes.

2• Think twice : much water conservation in the home is common

sense: • Washing clothes: Use full loads in your washing machine, or if

purchasing look for economy features such as half load capability or reduced water consumption.

• Refrigerate any drinking water in order to prevent running the tap for long periods waiting for cold water.

• Conversely, insulate hot water pipes to prevent running the tap for long periods waiting for hot water!

• Wash dishes by hand, using one bowl for washing and one for rinsing. Bowls are filled with less water than it takes to fill the sink.

• Use showers instead of baths. Have baths as a treat, a sensual experience to be relished once in a while. Have showers instead,

3• Collect rainwater. In most parts of the U.K. the water collected from rain falling

on the roof of an average house could supply the water needs of at least one person provided that the water is stored. This collected water can be used for most applications but care should be taken if you suspect any leaching of particles from your roof surface. If this is the case then the water can still be used for washing your car, or bicycle, and watering ornamental, (non edible) plants.

• Car washing: It is possible to wash a car with only one bucket of water. But does it really need washing?

• Garden watering: To save water and to give your plants the maximum benefit it is best to water out of direct sunlight, i.e., in the evening. This will cut down on water loss due to evaporation. Avoid sprinklers, which use water indiscriminately, and try to target the water precisely where it is most needed. Grow plants in beds, not containers.

• Save your cooking water and use as a stock or a base for soups; it can be kept for several days in a cooler or froze

4• Recycle more : All the water used in the home, apart from flush

water, can be re-used to some degree. Water can be collected from seven main sources in the home:

• Shower • Bath tub • Bathroom sink • (These three together use 75% of non-flush water consumed in

the home and contain less than 10% of particulates) • Washing machine • Utility sink • Dishwasher • Kitchen sink

Water Conservation in Industry

• IN INDUSTRY TODAY the most widely used water conservation practices involves recycling of cooling water and waste water.

• Instead of discharging used water into a nearby river, businesses often recycle water and use it again.

• What can you do to conserve water?• Can you suggest any water conservation plan?

Water Conservation in Agriculture

• Most of the water loss comes from evaporation, seepage, and runoff, so technologies that reduce these problems go a long way towards conserving water. Drip irrigation systems offer a promising step towards conservation. These systems deliver small amounts of water directly to plant roots by using perforated tubing. Water is released to plants as needed and at a controlled rate.

Solutions for the future

• Two solutions to prevent water shortages are desalination and transporting fresh water.

DESALINATION• IT Is the process of removing salt from salt water.

Some countries in drier parts of the world built desalination plants to provide fresh water. desalination plants heat salt water and collect the fresh water that evaporates. Because desalination consumes lot of energy, the process is too expensive for many nations to consider.

Desalinization

Transporting water

• In some areas of the world where freshwater resources are not adequate, water can be transported from other regions. The ships travel regularly from the mainland towing enormous plastic bags full of freshwater. The ships anchor in port and freshwater is then pumped on to the islands. This solution is also being considered in United States to transport water from Alaska to California.

Rain Water Harvesting?. • Rain Water Harvesting RWH- process of collecting, conveying & storing water from rainfall in an area – for beneficial use.

• Storage – in tanks, reservoirs, underground storage- groundwater

• Hydrological Cycle