Water Use and Management
Chapter 11 Section 2
Global Water Use
The three major uses of water
are residential, agricultural,
and industrial
Most fresh water worldwide is
used to irrigate crops
Availability of fresh water,
population size, and
economic conditions affect
how people use water
Residential Water Use
The average person in the
U.S. uses about 300 gallons
of water every day--only half
is used inside, the rest is used
outside for watering, washing
cars, etc.
In India, the average person
uses 41 gallons of water
every day
Water Treatment
Most water must be treated to
make it potable (safe to drink)
Water treatment removes
mercury, arsenic, and lead as
well as pathogens (organisms
that cause illness or disease)
Steps of Water Treatment
First filtration--the source of water supply is filtered to remove
large organisms and trash
Coagulation--alum is mixed in to form sticky globs (flocs).
Bacteria clings to the flocs which settle to the bottom
Second filtration--layers of sand, gravel, and coal filter remaining
impurities
Chlorination--added to prevent bacteria from growing
Aeration--air is forced through to release unwanted gases
reducing odor and improving taste
Additional treatment--some communities add fluoride for teeth,
sodium or lime to soften water. Treated water is then pumped
from storage tanks to homes and industry
Industrial Water Use
Industry accounts for 19% of
water use worldwide
It is used to manufacture goods,
dispose of waste, and generate
power
1,000 L of water is used to
produce 1 kg of aluminum and
500,000 L of water is used to
manufacture 1 automobile
Most is used to cool power plants
Agricultural Use of Water
It can take as much as 300 L
of water or produce one ear of
corn!
Agriculture accounts for 67%
of water used worldwide
80% of water used in
agriculture evaporates and
never reaches the plants roots
Irrigation
Fertile soil is sometimes found
where there isn't much rainfall
Irrigation is a method of
providing plants with water
sources other than
precipitation
Some crops are watered by
shallow, water filled ditches.
The U.S. uses high-pressure
overhead sprinklers (this is
very inefficient)
Water Management Projects
2,000 years ago, Romans built
aqueducts that brought water from
the mountains to dry areas of France
and Spain
People live in areas where the natural
distribution of water is inadequate
Water management projects such as
dams and water diversion canals are
designed to meet people's needs
Goals of such projects can range
from making a dry area habitable to
creating a reservoir for recreation
Water Diversion Projects
To supply dry regions with
water, all or part of a river can
be diverted into canals that
carry water great distances
The Colorado River is diverted
to meet the needs of 7 states
It is used for irrigation and
drinking water in Arizona,
Utah, and California
Many times the river is dry
before reaching the Gulf of
California
Dams and Reservoirs
When a river is dammed, an artificial
lake (reservoir) is formed behind
Water from the reservoir can be used
for flood control, drinking water,
irrigation, recreation, and industry
Dam are also built to generate
electrical power--20% of the world's
power is produced by hydroelectric
dams
When a dam is built, entire
ecosystems can be destroyed
50 million people worldwide have
been displaced from dams being
built
As the river enters the reservoir, it
slows down and deposits
sediment that it carries. This fertile
sediment builds up behind the
dam instead of enriching land
farther down the river
Farmland below the dam becomes
less productive
If the dam bursts, people living
below the dam can be killed
Water Conservation
As water becomes depleted,
water becomes more
expensive because wells must
be drilled deeper, polluted
water must be cleaned before
it can be used, etc.
Water conservation is one way
to ensure everyone will have
enough water at reasonable
prices
Water Conservation in Agriculture
Most water loss in agriculture
comes from evaporation,
seepage, and runoff
Drip irrigation systems offer a
promising step toward
conservation
Drip irrigation systems deliver
small amounts of water
directly to plant roots using
perforated tubing
Water Conservation in Industry
Many industries have
developed water conservation
plans
Most involve the recycling of
cooling water and waste
water
Some cities, like Denver, CO,
pay small businesses to
conserve water
Water Conservation at Home
A few changes in residential
water use will make a
significant contribution to
conservation
Low-flow toilets and showers
Water lawns at night to prevent
as much evaporation
Xeriscaping involves designing
landscaping that requires
minimal watering
Solutions for the Future: Desalination
Some coastal communities
rely on the ocean to provide
fresh water
Desalination is the process of
removing salt from salt water
Most desalination plants heat
salt water and collect the
fresh water that evaporates
Transporting Water
Where fresh water resources are
not adequate, water can be
transported from other regions
This is being done in the Greek
Isles because tourism is taxing
the fresh water supply
It is being considered in the U.S.
where almost half the fresh water
is in Alaska
77% of Earth's fresh water is in
ice caps and icebergs
Copy now, answer later
Write a description of the evaporative method of
desalination using terms from the water cycle.
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 can do to help conserve the
world's water supply.
Describe three ways that communities can increase their
freshwater resources.