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Fresh Water Supply and Demand
Is water a renewable resource? To answer this you must first understand what a renewable resource is. A
renewable resource is one that can be replaced in nature about the same rate it is used. Because water is
recycled in the water cycle it is considered a renewable resource. However, because the demands of human
needs have increased, water is not being returned to the cycle at the same rate. Sometimes water is used faster
than it can be replaced by precipitation. A water shortage occurs when there is too little water or too great a
demand on an area-or both. A water shortage may also occur because of natural processes, such as a drought
when it has not rained for a long time. When this happens both groundwater and surface water are affected..
So, is water a renewable resource?
People use water for household purposes, industry,
agriculture, transportation, and recreation. Think of
all the ways water is used in the home. Cooking,
washing, and flushing are some of the ways water is
used.
Industries use a lot of water. For example, power
plants and steel mills need huge volumes of water to
cool hot machinery. Many times it is an ingredient in
a product or used to separate different substances.
Water has also been used to transport people and
goods since ancient times We enjoy water for the
recreation it provides with swimming, sailing, fishing,
and water skiing, to name a few.
Water is also needed for agriculture. However, some areas don't receive enough regular rainfall for agriculture.
In such places, farmland must be irrigated. Irrigation is the process of supplying water to areas of land to make
them suitable for growing crops. In the US, more water is used for irrigation than for any other single purpose.
During a water shortage, people often try to avoid wasting water. Conservation is the practice of using less of a
resource so that it will not be used up. Reducing water use, recycling water, and reusing water are three
ways to conserve water. Water that is reused is called grey water. Using dishwater to water plants is an
example of reusing water, Why it is called grey water?
At home, we need to be aware of how we use
our water which is so readily available. For
every minute you shower, you use 18 liters of
water. How long do you shower? How much
could you save if you cut your shower by 2
minutes? What if everyone in your class did the
same? In industry, companies conserve water by
cooling the water they use and recycling it and
by using less .Farmers have found new ways to
use less water in irrigation.(pC67) such as drip,
spray and flood irrigation.
As the use of water in the world increases, so
does the need for water. An obvious place to find
a new source for water is the ocean. For
thousands of years, people have tried to make
fresh water from salt water.
When salt is removed from saltwater it is called
desalination. One way to desalinate saltwater is
distillation which involves boiling water so that it
evaporates, leaving the salt behind. The water vapor is
captured in a tube and then condensed to produce pure
liquid fresh water. Another method is freezing since only
the fresh water will freeze, leaving behind the salt.
However, desalination has its drawbacks. For one, it
takes money to build a plant and money to pay for the
fuel that is required to either burn or freeze. This heavy
use of energy poses a problem for the environment,
such as, global warming. Second, not all the water
Desalination plant that uses distillation
brought in to distill gets desalinated. It is returned to the
ocean but now has a higher concentration of salt water which
is not suitable to the life there. Third, many times the salty water that remains is not cooled and returned
to the ocean raising the temperature of the ocean, This can cause thermal pollution, which is when the
temperature of the water is not what it normally should be and could kill the organisms in it. Anything that
upsets the ecosystem of the ocean will show up as more problems later for the environment. What could
be some ways to deal with these problems of distilling the saltwater of the ocean?
Distillation is similar to what happens in the
water cycle.
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1. Water is heated and only pure H2O
evaporates. Any salt or other substances
are left behind.
2. Water vapor is cooled and condenses to form drops.
3. Drops fall and are collected as pure H2O.
Name_______________________________
Freshwater Supply and Demand
1. What is a renewable source? _________________________________________________________
____________________________________________________________________________________
2. Is water is a renewable resource? Why or why not? _______________________________________________
___________________________________________________________________________________________.
3. When does a water shortage occur? ____________________________________________________________
_____________________________________________________________________________________________
4. The condition of scarce rainfall for a few years is known as a(n) _______________________.
5. Circle the letter of each sentence that is true about droughts.
a. They affect the supply of surface water.
b. They affect the supply of groundwater.
c. They cause the water table to rise.
d. They may cause wells to run dry.
6. How can an aquifer be recharged naturally after a drought? (THINK)
_____________________________________________________________________________________________
7. Describe how industries use water. _______________________________________________________________
_____________________________________________________________________________________________
8. For what purpose does the US use the most freshwater?________________________________________________
9. Using a resource wisely so that it will not be used up is called ________________________________.
10. What are the 3 R’s of conservation? ______________________________________________________
______________________________________________________________________________________
11. What is reused water called? _____________________________ Give an example.________________
______________________________________________________________________________________
12. Circle the letter of each choice that helps conserve water in the home. (THINK)
a Taking shorter showers
b. Watering the lawn around noon instead of early or late in the day
c. Keeping a pitcher of drinking water in the refrigerator
d. Running the washing machine only when you have small loads
13. The process of obtaining fresh water from salt water is called ___________________________
14. Circle the letter of the choice that gives the correct sequence of steps in distillation.
a. Evaporation, boiling, condensation
c. Boiling, evaporation, condensation
b. Boiling, condensation, evaporation
d. Condensation, boiling, evaporation
MORE ON BACK
15. ___________________________________________ is when water is heated and returned to a river, lake, or
the ocean before it is cooled
16. What environmental problems are created when ocean water is desalinated?
_________________________________________________________________________________________
_______________________________________________________________________________________________
_______________________________________________________________________________________________
17. Compare the process of distillation and the water cycle. Start with in the water cycle the sun evaporates
the water. This is similar to distillation when ____________________________________________________
_________________________________________________________________________________________
_________________________________________________________________________________________
________________________________________________________________________________________
Be sure to include a because……for your answers.