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USING AND
LOSING WATER
Summary: Students consider how water is used on
the planet, and how it can be lost from easy and inexpensive
human use.
Classroom Management:
In this class students
write a short essay on one of two suggested topics. It is useful
to enrich their writing with a preliminary discussion on the
uses and losses of water in the household, the country and the
world.
DO YOUR STUDENTS
KNOW: Where
water flows? Where water is stored? Review Page
Activity Steps:
Step 1: Facilitate a discussion:
How do we use and lose ("consume") fresh water?
IN THE HOME
How do we use water in our homes? [Students may mention drinking, washing.
They might not think of watering gardens and lawns, doing the
laundry etc.]
How can water be lost from household use?
[Students might think of leaky faucets, the washing of clothes
or dishes without full load etc. They might not think about toxins
that get poured down sinks and washing machines.This water can
drain into a stream and then into a river and sea. It may not
get back into the "recharge area" of an aquifer. It
may be contaminated with phosphates and other materials and therefore
be a danger to the local environment.]
How does this differ around
the world? [The range of
use of gallons per person extends from hundreds a day (US, Canada,
former Soviet Union, Japan), to 2-4 (some places in Africa and
the Middle East)]
See Domestic
Use of Water
IN THE COUNTRY
How do people use water in a
country?
[Students might mention growing
crops, especially using irrigation; they might not know that
water is used extensively in cooling for electric plants, or
in cooling, cleaning or dissolving and carrying materials in
industry. A great deal of energy is wasted as heat when power
is produced in a power plant. They also might not know that that
countries are increasingly supplying water to their citizens,
instead of citizens getting their water from wells, as more people
live in areas without a reliable water supply.]
See Country
Use of Water
How can water be lost from country use? [Students
might think of pollution from fertilizers, heavy metals or pathogens
from sewarge They might not think of evaporation during irrigation.]
Isn't water safe underground?
How can water be lost from underground
storage? [Students
might think of pollution seeping into aquifers, or the overdrawing
of the underground water supply in an unsustainable way.]
IN THE WORLD
How do people in the world as
a whole use water?
Look
at a graph of world use of fresh water, such as World
population and fresh water use
http://www.cnie.org/pop/pai/image1.html The authors report, "Since 1940,
the amount of fresh water used by humanity has roughly quadrupled as world population has doubled.
Some water experts estimate the practical upper limit of usable
renewable fresh water lies between 9,000 and 14,000 cubic kilometers
yearly. That suggests a second quadrupling of world water use
is unlikely."
What countries are likely to experience
water scarcity? Look at WRI Projected
Water Vulnerability in 2025. http://www.wri.org/wri/trends/water.html and check the countries against a world
map with country names.
Step 2: Write a short essay
Either write about how a life is lived with little
water, and/or with water of questionable quality (If students need some help, you might read
selections
from the Water
Problem in My Village
http://www.worldbank.org/depweb/english/modules/environm/water/case1.htm)
or invent a country that
wastes water in ever possible way. Go on to invent a system of
penalties and rewards that will turn its behavior around.
Collect
essays, reading a few or, it time permits, all to the whole class.
Post
the (best?) essays in the COMMONS database, Lives with Less Water, or Water Wasting Countries.
Homework:
Measure how much water comes out of the tap during the time you brush your teeth. You
will need another person standing next to you collecting the
water while you do this. Then measure how much water you need
to brush and rinse without the tap running all the time.
Extensions:
Calculate the cost of those faucet drips!
http://www.waterwiser.org/frameset.cfm?b=2
Modelling Evaporation
If your students do not understand
evaporation, you might set up small dishes of water in various
spots in the classroom and observe the change over time, as well
as any precipitates from that evaporation.
In order to simulate hotter climates,
you could blow hot dry air ( place near hot air duct or small
space heater) over the bowl of water. Compare evaporation times
with and without the heat.
In order to reproduce the challenges
of irrigating with waters that have salts or minerals, students
can make a solution (until it is clear) of salt and water and
then see the results of evaporation. Are there some plants that
grow well in salt water? Do some growing experiments.
Modelling Pollution
Add a red dye to the water dishes,
and observe the color precipitating out with evaporation, leaving
a colored ring.
(Advanced) Collect some fresh water from
an alternative source of water. Create a model that displays
how your choice works. Choices include:
- rainwater catchment from roofs
and other structures
- rainwater harvesting in fields
- capture of flood and winter runoff
- desalination of seawater and brackish
water
- imports of water by tanker, pipeline,
or medusa bags (big floaters bringing water)
- cloud seeding
(List adapted from David Brooks,
Between
the Great Rivers: Water in the Heart of the Middle East)
http://www.idrc.ca/books/focus/804/chap4.html
Read the World Bank's Access
to Safe Water. Study Chart 1 and 3
http://www.worldbank.org/depweb/english/modules/environm/water/index.htm
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