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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.
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 do you think 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, 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 he 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 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?
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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. c. They cause the water table to rise.
b. They affect the supply of groundwater. 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 ______
______
______
Surface Water
Fresh water on Earth may be moving, as in streams and rivers, or still, as in pond and lakes.
All fresh water, however, comes from precipitation. The many small streams that come together at the source of a river are called its headwaters. Streams and smaller rivers that feed into a main river are called tributaries. Tributaries flow downward toward the main river, pulled by the force of gravity. A river and all of its tributaries together make up a river system. The land area that supplies water to a river system is called a watershed. Another name for a watershed is a drainage basin. One watershed is separated from another by a ridge, or continuous line of high land, called a divide. Streams on each side of the divide flow in different directions.
Ponds and lakes are bodies of fresh water. Unlike the moving water of streams and rivers, ponds and lakes contain still, or standing water. Ponds and lakes form when water collects in hollows and low-lying areas of land. People can also create a lake by building a dam across a river. The lake may be used for supplying drinking water, for irrigating fields, or for recreation. A lake that stores water for human use is called a reservoir.
Ponds contain many different habitats for the organisms that live there from its muddy bottom to the tall grasses that grow along its edges. The main producer in a pond is algae which also produces oxygen for the organisms that live in the water. Because the water is shallow enough for sunlight to reach the bottom, plants grow throughout the pond. Lakes, on the other hand can be so deep in the center that no light can reach there and no plant life can grow. Lakes, like ponds, provide homes for many kinds of fish, insects, and other wildlife.
Lakes experience changes. When the temperature drops during the change of seasons, the more dense cold layer on the surface sinks to the bottom causing waters to mix. This mixing, also called turnover, causes materials to rise from the lake bottom. Turnover occurs twice each year as the seasons change. Lake turnover refreshes the supply of nutrients throughout the lake. Nutrients are substances such as nitrogen and phosphorus that enable plants and algae to grow. This is common in cool, northern areas of North America.
The second type of change that may occur in a lake happens over a period of time caused by eutrophication sometimes leading to the death of a pond or a lake. Eutrophication is the process by which a body of water acquires a high concentration of nutrients, especially phosphates and nitrates. This can cause an algal bloom (over growth of algae). As the algae die and are decomposed by bacteria, dissolved oxygen in the water is depleted, causing the death of other organisms, such as fish. Sediment from the decaying matter builds up. As the water becomes shallower aided by evaporation, the lake becomes a soggy marsh and eventually a filled in meadow. Eutrophication is a natural, slow-aging process for a water body, but human activity greatly speeds up the process. Many times these excess nutrients are a result of human activities, particularly, when fertilizers from farms or lawns are washed into the lakes by runoff or when phosphates from laundry detergents are allowed in wastewater.
Name______Date: ______
Surface Water
1. Into what two categories can fresh water be divided? ______and ______
Match the term with its definition.
_____ 2. tributarya. A river and all its tributaries together
_____ 3. river systemb. The land area that supplies water to a river system
_____ 4. watershedc. A smaller steam or river that feeds into a main river
_____ 5. divided. The ridge that separates one watershed from another
6. What is another name for a watershed? ______
7. The many small streams that come together at the source of a river are ______.
8. Label the diagram comparing lakes and ponds.
______
9. When do ponds and lakes form? ______
10.True or False? The main food producer in ponds is algae.
11. Explain why plants grow throughout a pond and not always throughout a lake.
______
______
12. A lake that stores water for human use is called a(n) ______
13. True or False? Compared with the center of a pond, the center of a lake has more organisms.
14. What occurs during lake turnover? ______
______
15. True or False? Lake turnover occurs only once a year.
16. True or False? Lake turnover happens because the density of layers of the water in it changes.
17. What is eutrophication? ______
18. What is an overgrowth of algae called? ______
19. Why can eutrophication lead to the death of a pond or lake? ______
______
20. What nutrients increase the growth of plant life in a lake that may cause eutrophication?
______and ______
21. What human activities contribute to eutrophication? ______
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