C H A P T E R 1 1 , S E C T I O N 2 : WAT E R U S E & M A N AG E M E N T

S TA N DA R D S : S C S H 2 A-B , 3 C , 4 A , 5 A , 6 A , D , 9 D

WATER

HOW DO PEOPLE USE WATER?

• Agricultural Use• Industrial Use• Residential/

Domestic Use

0

10

20

30

40

50

60

70

Irrigation

Industry

Domestic

HOW IS WATER USED IN RESIDENTIAL AREAS?

• 14% of world water use• Varies by country• Average person needs 1.3

gallons to survive• U.S. resident uses 80

gallons per day• India resident uses 10

gallons per day

• In U.S. we use it for• Inside sources: drinking,

cooking, washing, toilet flushing, etc.

• Outside sources: watering lawns, washing cars, etc.

0

50

100

150

200

250

UnitedStates

Netherlands

Gambia

HOW IS WATER TREATED TO MAKE IT POTABLE (DRINKABLE) IN RESIDENTIAL AREAS?

• Need to remove mercury, lead, arsenic, pathogens (disease causing organisms), etc.

• Steps to treat water…• First Filtration• Large materials/trash removed

• Coagulation/Sedimentation• Alum is added to clump up large dirt particles into globs called floc. This settles to the

bottom of the tank and creates sludge. Sludge can be removed, disinfected & used as fertilizer.

• Second Filtration• Water passed through filter of sand, gravel, charcoal to remove impurities

• Chlorination• Chlorine is added to prevent bacteria from growing in water.

• Aeration• Air is forced thru water to release unwanted gases which reduces odor & improves

taste.

• Additional Treatment• Fluoride is added to prevent tooth decay• Sodium compounds or lime may be added to soften hard water (hard water will not

lather when soap is added)

• Storage• Sent to water tower before pumped to homes/businesses

HOW IS WATER USED IN INDUSTRY?

• 19% of world water use.• Mostly used to cool power

plants• Pump out river water, water

boiled, produces steam, turns turbines, water re-condensed and cooled in cooling towers, either reused or returned to river.

• Manufacture goods• 1,000L used to produce 1kg

of aluminum for cans• 500,000L used to produce a

car

• Dispose of waste

HOW IS WATER USED IN AGRICULTURE?

• 67% of world water use• Irrigation• Providing plants with

water from sources other than direct rainfall.

• Traditional• Flood furrows

• Lose a lot to evaporation

• Modern• Overhead sprinklers

• Some evaporates

• Drip irrigation• Most efficient but most

expensive (replace hoses)

WHAT ARE WATER MANAGEMENT PROJECTS?

• Creation of dams, canals, aqueducts, & reservoirs to meet the needs of people.• Ex:• Mono Lake in

California• Three Gorges Dam

in China

MONO LAKE, CA

• In 1941, L.A. started diverting Mono Basin streams to add to L.A. Aqueduct.

• Mono Lake’s volume halved while salinity doubled. The simple ecosystem began to fail and threatened migrating birds and nesting gulls.

• The state and courts now mandate raising the level of the lake 17 feet. It will take about 20 years.

• Should make more habitable for birds & fish

PROS & CONS OF DAMS

• Pros:• Creates reservoir- artificial

lake behind dam• Collect and store water

from rain and snow• Produce electricity• Irrigate farm land• Control flooding • Provide drinking water to

cities, towns and rural areas

• Provide recreational activities such as swimming, boating, fishing

• Cons:• Enormous loss of water due

to evaporation• Flooded land destroys forests

or cropland and displaces people

• Danger of Dam collapse• Downstream areas deprived

of nutrient-rich soil, which will eventually clog the reservoir

• Migration and spawning of fish disrupted

• Causes water wars between states & countries

• Expensive to build

WHAT ARE SOME WAYS TO CONSERVE WATER?

• As water becomes depleted, water becomes more expensive.• Dig deeper wells• Send water through

pipes a greater distance• Clean polluted water

• Conservation is best method of solving water shortage problems.

WHAT ARE SOME WAYS TO CONSERVE WATER?

• Agriculture• Most problems with evaporation,

seepage, and runoff• Drip irrigation systems deliver

water directly to roots via perforated tubing- less evaporation

• Industry• Recycle cooling water

• Residential• Low flow toilets/shower heads• Turn off water while brushing

teeth.• Xeriscaping- using drought

tolerant plants in landscaping so you don’t have to water them too much.

• Water lawn at night

WHAT ARE SOME SOLUTIONS TO THE WATER DEPLETION PROBLEM?

• Desalination• Removing salt from

ocean water• Two methods:• Distillation- heat &

evaporate fresh water, leaving salts behind

• Reverse osmosis- pass water through membranes that trap salt

• Expensive • Ex: Middle East,

coastal communities

WHAT ARE SOME SOLUTIONS TO THE WATER DEPLETION PROBLEM?

• Transporting Fresh Water• Melt water at

source, bag it and transport it to areas in need.• Towing icebergs-

efficient technology not developed yet.

YOU SHOULD BE ABLE TO…

• Describe the patterns of global water use for each continent shown in the bar graph in Figure 5.• Describe the drinking water treatment process in

your own words.• Describe the benefits and costs of dams and

water diversion projects.• List at least three things you would do to help

conserve the world’s water supply.