chapter 12 water, weather, and · 2020-02-02 · 318 chapter 12 • water, weather, and climate nel...

weather

climate

heat capacity

heat sink

convection

global warming

fl ood plain

12CHAPTER

314 Chapter 12 • Water, Weather, and Climate NEL

Water, Weather, and Climate

KEY QUESTION: How do water systems, weather, and climate affect each other?

Looking Ahead

The climate of a region, and the weather on any particular day, are affected by large bodies of surface water.

Climate affects water’s temperature and changes of state on Earth.

Research skills can be used to assess issues related to local and global water supply.

Global warming is affecting water systems around the world.

The long-term sustainability of water systems depends on how well we manage and care for water.

The skills of scientifi c inquiry can be used to compare water use around the world.

VOCABULARY

Sci8_UnitD_Chap12.indd 314Sci8_UnitD_Chap12.indd 314 12/22/08 9:31:20 AM12/22/08 9:31:20 AM

315NEL

Reading Science and Technology

And Here is a Severe Weather Warning...

Text Genres: The Comic Strip To understand this comic strip, you need to read in a non-linear manner, scanning both the pictures and text to follow the story. You may also need to make connections between pictures, text, and your background knowledge. Sometimes, a message is hidden and you must make an inference to fi gure out the meaning. Read the comic strip, then work with a partner to discuss the following:1 Some of the text is spoken by characters, while

some of the text represents what they are hearing. What helps you to distinguish between the two?

2 What inference can you make about why the Rideau River area fl ooded?

3 Describe the characters’ feelings in the last frame. Why are they feeling this way? How do you know?

L I N K I N G T O L I T E R A C Y

1 2

3 4

5

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12.1 Surface Water and ClimateSummers in Ontario can be rainy and wet. When this happens, the media oft en show images of swollen rivers and fl ooded farm fi elds (Figure 1). In other years, unusually dry summers result in drought. It seems that every year, some weather record is broken: “Hottest day in June” or “Most snow in one day for a century.” Many other countries are also experiencing record-breaking weather.

Weather and ClimateWhat is the diff erence between weather and climate? Weather is a set of environmental conditions that changes from day to day. A description of a day’s weather might include the temperature, whether it is sunny or cloudy, and what kind of precipitation is falling. Th e weather in an area changes during a day. Climate, on the other hand, is a set of environmental conditions averaged over 30 years or more. It does not describe any particular event at any particular time.

Consider Timmins in northern Ontario. We can describe its February climate as cold. Th e average daytime high temperature is –7.5 °C, and the average overnight low is −21.3 °C. Th e average snowfall for the month is 40.6 cm. Th e weather on February 20, next winter, however, might be a little diff erent. Th ere could be a daytime high of 5 °C and an overnight low of –5 °C, and no snow. You can use climate data to make a prediction about the conditions at a certain location and at a certain time of year. Th e actual day-by-day weather that occurs, however, might be quite diff erent.

weather: the day-to-day environmental conditions in a given place at a given time; includes temperature, cloud cover, wind speed, and precipitation

climate: an average of weather conditions in an area over 30 years

Figure 1 Extreme weather, such as intense rainfall, can cause property damage.

Making ConnectionsWhen you read, you can make connections with the text. There are three types of connections that you can make: 1. Text-to-text: Read the fi rst

paragraph on this page. How does it relate to the comic strip on the previous page?

2. Text-to-self: What extreme weather have you experienced? Have you been in a tornado, fl ood, or other type of dangerous weather? How does your experience relate to information on this page?

3. Text-to-world: How does the text on this page relate to places, people, or events in the world? Perhaps you have seen something about this topic on the news, on the Internet, or in a newspaper.



Sun

energy radiatedfrom Earth(day and night)

energy radiatedfrom the Sun

31 °C 23 °C

gravel water

12.1 Surface Water and Climate 317NEL

Causes of Temperature DifferencesEnergy from the Sun (solar energy) drives the evaporation of water in the water cycle and also heats Earth’s surface. What happens to Earth’s surface at night, when the Sun disappears below the horizon? Earth cools down as it radiates more energy than it absorbs (Figure 2). Th e change from daytime heating to nighttime cooling is so dramatic on most planets that they cannot support life.

Heat CapacityWhy does Earth support life better than other known planets? Part of the answer lies in the substances that make up Earth’s surface: water, soil, and rock. An important property of these substances is their heat capacity. Heat capacity is a measure of how much thermal energy (heat) a substance requires to increase its temperature by a certain amount. Th e higher the heat capacity of a substance, the more thermal energy it can store. Soil and rock have lower heat capacities than water. Th is means that soil and rock require less thermal energy than water to increase in temperature (Figure 3).

Heat capacity also includes the amount of thermal energy that a substance releases. If the light source is removed from the gravel and water in Figure 3, they would begin to release their stored thermal energy to the surrounding air. Th e gravel, however, would release its energy more quickly. Gravel has a lower heat capacity than water. Because of this, the gravel would cool down faster and heat the surrounding air faster. However, once the gravel has cooled, it would no longer be able to heat the air, and the air would begin to cool. Th e water would heat the air more slowly, but for longer. Water can store energy for a long time, even if the air above it cools at night, or if the seasons change.

Earth’s atmosphere is another important part of what makes Earth so diff erent from most planets. Th e atmosphere traps some of the energy radiated from Earth. Th is helps keep Earth warmer than it would be otherwise.

heat capacity: a measure of the amount of thermal energy needed to raise the temperature of a substance by a certain temperature interval; a measure of how much thermal energy a particular object can store

Figure 2 Earth radiates energy at all times. As it rotates, the side of Earth facing the Sun absorbs solar energy and Earth warms. The side of Earth turned away from the Sun does not receive solar energy.

Figure 3 If equal amounts of water and gravel start off at the same temperature and are exposed to the same amount of thermal energy, the gravel will heat up to a higher temperature than the water because gravel has a lower heat capacity.


cool air sinks

warm airpushed upward

land

sea


Heat Sinks and ClimateAnything that absorbs thermal energy without becoming much warmer is called a heat sink. Substances with high heat capacities, such as water, are good heat sinks. Oceans can absorb a lot of energy from the Sun without evaporating. In fact, the temperature of oceans remains fairly constant.

Water absorbs energy when sunlight hits the surface of the water. Water is continually moving and mixing. Th is moves deep, cooler water to the surface, where it absorbs more energy. In this way, energy is transferred throughout the entire body of water. Th is is what prevents ocean water from heating up.

Th e temperature of land increases more on a sunny day than does the temperature of nearby water. Both land and water can warm the air above them, but the lower heat capacity of rock and soil means that the air above the warmed land heats up faster than the air above the water. When air becomes warm, it becomes less dense. As cooler, heavier air sinks, it pushes the warmer, lighter air upward (Figure 4). Th is diff erence in density causes air movements called convection currents, which we feel as wind.

Land gives up stored thermal energy much more rapidly than water. When the Sun goes down—or when the days get shorter in the winter—land cools more rapidly than does the water.

Consider how a body of surface water stores energy and releases it slowly as the surrounding temperature falls. Table 1 compares the temperatures of two coastal cities and two inland cities (averaged over many years).

heat sink: matter that absorbs thermal energy but does not change state or signifi cantly increase in temperature

convection: the transfer of thermal energy from one part of a gas or liquid to another by a circulating current of faster-moving and slower-moving particles

Figure 4 When the land is warmer than the water, the air over the land is less dense than the cooler air over the water. The denser air above the water fl ows down and toward the land, causing a sea breeze.

Table 1 Climate Data for Four Canadian Cities

Victoria Winnipeg Timmins St. John’s

average January minimum temperature (°C)

2 −22 −24 −7

average July maximum temperature (°C)

20 27 24 21


NORTHWESTTERRITORIES NUNAVUT

YUKON

BRITISH COLUMBIA

ALBERTA

SASK

ATCH

EWAN

MANITOBA

ONTARIO

NOVA SCOTIA

PRINCE EDWARDISLAND

NEWFOUNDLANDAND

LABRADOR

NEWBRUNSWICK

Victoria

TimminsWinnipeg

St. John’sQUEBEC

12.1 Surface Water and Climate 319NEL

You would expect each of the cities in Table 1 to receive the same amount of energy from the Sun throughout the year (Figure 5). However, you can see that the inland cities, Winnipeg and Timmins, are colder in the winter and hotter in the summer than the coastal cities.

Scientists have taken temperature measurements of soil and water over many years. Th ese measurements indicate that only land near the surface experiences heating and cooling; farther underground, the temperature remains constant. Temperature changes occur in water to a much greater depth than on land because the water’s surface is stirred up by wind, waves, and ocean currents. Th ese factors help to mix warm surface water with cooler deep water.

Land near water has a milder climate than land far from water because bodies of water act as heat sinks. Coastal cities are generally warmer in the winter and cooler in the summer than inland cities. Southwestern Ontario has a more moderate climate than neighbouring regions to the west and east of the Great Lakes because the Great Lakes act as heat sinks. Th ey absorb thermal energy during the summer and gradually release it during the winter.

Figure 5 Victoria, Winnipeg, Timmins, and St. John’s are all approximately the same distance from the equator. However, the four cities have very different climates.

CHECK YOUR LEARNING

1. What is the difference between weather and climate?

2. Explain in your own words how the heat capacity of water makes any body of water a good heat sink.

3. Describe how warm water at the surface of a lake or ocean mixes with deeper, cooler water.

4. Why do areas close to large bodies of water have milder climates than inland areas?

C

Making InferencesSometimes a text has an inferred meaning. “Inferred” means that a text says something, but also means something more. The text here does not tell you about the temperature of cities like Toronto or Halifax. Think about what you know about these cities. One is on the shore of the Great Lakes and the other is on the East Coast. What have you read in the text to infer that Toronto and Halifax enjoy milder climates than many Canadian cities?

What other Canadian cities are you familiar with? What can you infer about their temperatures based on their coastal or inland locations?




Glaciers, Polar Ice, and Global Warming You learned in Section 11.1 that most of the fresh water on Earth is ice. Ice is found on many mountaintops and covers the polar regions all year long (Figure 1).

Solid Water in the Water CyclePrecipitation falls as snow when temperatures drop below 0 °C. Any precipitation that falls at the North and South Poles falls as snow. Th e number of months in which snow falls decreases as you move further from the poles. If the temperature remains below 0 °C, snow accumulates. Snow melts if temperatures rise above 0 °C in the spring (Figure 2).

Snow that does not melt in the spring accumulates year aft er year. Th e top layers of snow press down on the older snow underneath. Th is pressure gradually changes the lower layers to ice. Over time, the ice builds up to form glaciers, icecaps, and polar ice sheets.

12.2

Figure 1 The solid water in glaciers and polar icecaps is inaccessible as a source of fresh water.

Figure 2 In many parts of the world, snow falls and accumulates in the winter and melts each spring.


Sea Ice Concentration (percent)September 16, 2007

1979-2000 median minimum

2005 minimum

500 km

2007 minimum

12.2 Glaciers, Polar Ice, and Global Warming 321NEL

The Effects of Climate ChangeGlaciers, icecaps, and polar ice sheets are sensitive indicators of changes in climate. When the climate is cold for centuries—as it is during an ice age—the ice in glaciers builds up. Less ice melts in the summer during these periods. Th e area of land covered by ice increases. Th e ice cover in the northern hemisphere advances southward; the ice cover in the southern hemisphere advances northward.

If there is less precipitation than usual for several years, or if more ice melts than usual, then the ice cover starts to shrink. Glaciers retreat higher up the mountainsides, and polar ice sheets cover smaller areas. Climate scientists are seeing this happen today (Figure 3). Th ey believe that the shrinking ice is a sign that the temperature of Earth’s surface is gradually rising. Th is trend of increasing average global temperature is called global warming.

Scientists understand the interactions that occur among oceans, the air above them, and climate. Water temperatures increase when the oceans absorb more energy from the Sun. Warm water is less dense than cool water. Th is warm water takes up more space as ocean temperature rises and makes the sea levels rise. Warmer ocean water also warms the air above it. Th is warm air circulates around the globe, warming polar regions and speeding up the melting of polar ice. As more polar ice melts, water fl ows into the oceans, again raising sea levels. Rising sea levels are evidence of global warming. Climate Effects in CanadaClimate scientists have noticed that global warming has the opposite eff ect on water levels in the Great Lakes. Rather than raising the water level, as is happening in the oceans, global warming is lowering the water levels in the Great Lakes (Figure 4). Th is is partly because warmer water evaporates faster than cooler water.

Water is now evaporating more quickly from the Great Lakes than it is being replaced by precipitation. Th e volume of water leaving the system is greater than the volume of water entering the system. Symptoms like this remind us that we need to sustain the Great Lakes as a freshwater source.

global warming: an increase in Earth’s average atmospheric temperature

Figure 3 Arctic sea ice has shrunk considerably in the last 30 years.

Figure 4 The water level in Lake Huron and the other Great Lakes is becoming alarmingly low.

Go to Nelson ScienceGo to Nelson Science

To learn more about how climate change can affect sea levels,



El NiñoEvery few years, Canada’s climate is aff ected by a large current of warm water that forms in the Pacifi c Ocean, off the west coast of South America. Th is current of warm water is called El Niño. Th e warm current moves northward, warming the air above it. As the warm air moves inland, it sometimes leads to warmer-than-usual winter temperatures. Snowfall becomes less frequent, which results in less water accumulation in watersheds. El Niño has caused drought conditions in the Canadian prairies over the past several years. Storms and HurricanesA rise in the temperature of the Atlantic Ocean produces warm air above the ocean surface. Near the equator, the speed of prevailing winds drops during the summer months. Once storms form, they remain in place or only move slowly, allowing for more moist air to be drawn into them from the ocean. With this additional warm air, storms develop into hurricanes (Figure 5). When a hurricane reaches shore, the accompanying winds push a large volume of ocean water, called a storm surge, inland.

Global warming melts glaciers and icecaps and warms ocean currents and air currents. Bodies of water, like the Great Lakes, do not lose as much of their stored summer thermal energy as they would if the air were cooler. Th e lakes stay warmer and keep nearby regions warm. We are seeing a changing pattern of milder winters and hotter summers in Canada, which suggests that the climate is getting warmer.

Figure 5 Wind damage from hurricanes may result in loss of life and signifi cant property damage.

CHECK YOUR LEARNING

1. The Athabasca Glacier in western Canada continues to shrink every year. What does this suggest about the climate in that region? Explain your answer.

2. In your own words, explain how rising sea levels are an

indication of global warming.

3. Explain what is happening to water levels in the Great Lakes.

4. (a) What is El Niño? (b) Describe the effect of El Niño on Canadian weather.

5. Explain how a hurricane forms.

C

Chart Your LearningAfter you read this section, create a three-column chart in your notebook to record what you have learned. At the top of each column, write one of the following headings: Climate Effects in Canada; El Niño; Storms and Hurricanes. Below each heading, write one or two sentences to summarize what you have learned. Check to make sure that your notes sum up the main idea for each topic.



To learn more about El Niño, storms, and hurricanes,


EXPLORE AN ISSUE CRITICALLY

12.3 Explore an Issue Critically 323NEL

Defi ning the Issue Researching Identifying Alternatives Analyzing the Issue Defending a Decision Communicating Evaluating

SKILLS MENU

12.3Water Exports Th e United Nations predicts that by the year 2025, two-thirds of the world’s population will live in regions where fresh water will be scarce. Many of these regions are currently “water rich.” Others are areas that have been aff ected by droughts for decades.

A multinational company has had a permit to extract water from a groundwater source near Guelph, Ontario, for the past few years (Figure 1). Th ey take 3.6 million litres of water a day to sell as bottled spring water (Figure 2). Recently, the company applied to renew its water permit for another fi ve years. Local citizens joined an organization called Wellington Water Watchers (WWW) to fi ght the renewal request. Th e Grand River Conservation Authority and the City of Guelph joined WWW to commission a study of the local geology. Th e three organizations were concerned about the eff ects of withdrawing too much water from one aquifer. Th ey worried about the impact it would have on the water table. Guelph and surrounding communities rely on this groundwater for their own needs.

In 2008, the Ministry of the Environment rejected the fi ve-year renewal request, but granted a two-year renewal. Th ey said they could not altogether ban the water removal for commercial sale because there are currently no laws in place to protect freshwater sources.

Figure 2 Most bottled water is taken from the same freshwater sources that supply our tap water.

Figure 1 Guelph is a small city in the Grand River watershed.



The Issue Water can be legally bought and sold across our borders. What are the implications of this practice? Will Canadians be short of fresh water in the future? Find out how much water Canadians export to other countries and the eff ects this has on our own supply of fresh water. You will summarize your fi ndings in a letter to a local politician.

GoalTo write a letter to your local Member of Parliament. Your letter should clearly outline your position on treating water as a product that can be sold throughout the world. Your position must be based on facts. Outline a new law that, if passed, would defend your position.

Gather InformationWork in small groups to identify regions in Canada or other countries where freshwater sources are threatened. Find out whether water is being removed from any of these regions to be sold.

Be sure to search diff erent media sources for perspectives on this issue. Be aware of the target audience of each source. Do you think that any of these sources are biased in one way or another?


Identify SolutionsConsider countries that are currently facing a critical shortage of safe drinking water. How should these countries get drinking water? Should Canada supply them with water? What are the alternatives?

Make a DecisionFollow these steps as you write a letter to your Member of Parliament:

Summarize the current availability of fresh water in Canada. Refer 1. to the sustainability of water resources.Identify an area that is critically short of safe drinking water and 2. that may consider importing Canadian water.Decide whether Canada has suffi cient freshwater resources to 3. allow companies to sell our fresh water, or whether Canada should deny any requests to export water. Whichever position you take, recommend a law that should be passed to ensure that our water supply is managed sustainably.

CommunicateShare your letter with another student who has taken a diff erent position. Discuss the rationale behind your respective choices.

Writing a Persuasive Text: VoiceIn your letter, you will need to convince your audience of your position. How do authors persuade their readers of their position? By writing in such a way as to transmit their voice through their writing.

To write so that your voice can be heard• Write from a position that

you truly believe in. If you (the writer) are not convinced of your position, then the reader will not be convinced either.

• Thoroughly research your topic so that you can provide evidence to support your beliefs.

• Use words like “concern,” “safety,” “life-threatening,” and “critical” to touch your readers’ emotions.


8.A.2.8.A.2.SKILLS HANDBOOK

3.I., 7.C.3.I., 7.C.SKILLS HANDBOOK


12.4 Floods and Droughts 325NEL

12.4Floods and Droughts Floods usually result from heavy rainfall or rapid snowmelt. Droughts are caused by dry weather conditions where water evaporates faster than it is replenished. Th e media oft en report these events because of the loss of life and property damage that are associated with them (Figure 1). Floods are important to the natural environment because they add moisture to dry land, top up aquifers, and provide nutrients to the soil. Droughts oft en result in forest fi res that clear out old dead trees and smaller plants, making room for new life. Some tree seeds only sprout and grow aft er being heated by a forest fi re.

FloodsFloods are the most costly natural disasters in Canada in terms of property damage. Th ere are diff erent kinds of fl oods. Each is caused by a variety of factors.

Rapid snowmelt and many days of heavy rain cause regional fl oods. Th ese fl oods are especially bad if the ground is frozen or already saturated with water. Th e water that causes a regional fl ood tends to move slowly and covers a wide area. Flooding is an annual event in many regions, such as the Red River in Manitoba and the Nile River in Egypt.

Flash fl oods are the most deadly and damaging kind of fl ood. Th ey develop quickly and oft en without warning. Huge volumes of fast-moving water rush along river valleys, or even along streets. Flash fl oods are generally produced by a sudden storm that stalls over one location.

Storm surges are fl oods that occur along coastlines when hurricanes come ashore. Th ey are particularly dangerous if the coastal land is below—or only slightly above—sea level. Th e storm surge that accompanied Hurricane Katrina left a path of death and destruction when it came ashore near New Orleans in 2006.

Figure 1 Both fl oods and droughts can be devastating to people living and farming in an area.



Ice-jam fl oods usually occur in the spring along Ontario’s rivers. Th ese fl oods are caused by river ice breaking up and becoming jammed in a narrow part of the river or behind a bridge (Figure 2). Th e water backs up and begins to fl ow around the ice, fl ooding over the banks. Suddenly, the ice breaks, releasing a surge of cold water that extends beyond the banks of the river. Preventing FloodsTh ere are things that people can do to protect themselves and their property from fl oods. A fl ood plain is a low area of land alongside a river.

New homes should not be built on, or too close to, fl ood plains.Federal and provincial governments, oft en working with

Conservation Authorities, dam rivers to retain water. Dams control the release of water during potential fl ood conditions. Holding back the natural fl ow of a river alters the local water system by forming a reservoir or lake above the dam. Water that is stored in a reservoir is oft en diverted to other areas. Some areas may now receive less water, or no water at all.

DroughtsTh ere are also diff erent types of droughts. An area with a permanent drought (less than 2.5 cm of precipitation annually) is called a desert. A period of six months or more with no rain or snow is referred to as seasonal drought. Drought can also occur when expected rains do not fall for a long period of time. People who get their water from wells are particularly aff ected by droughts. Wells can dry up, leaving households and farmers with no access to fresh water. Unlike fl oods, not much can be done to prevent droughts. Human ActivitiesWater shortages are oft en caused by human activities. Th ese are not natural droughts, but they have similar eff ects on local populations. Nearly all of the world’s river systems are now altered by human activities. People altered water systems by building dams. Large populations of people withdraw water from river systems for drinking water and for irrigation. Companies extract and bottle water to sell. Together, these activities reduce the supply of surface water and groundwater.

Trees and other vegetation naturally absorb and store water during wet periods. Th ey then clean the water and release it slowly during dry periods. Th e loss of trees in a watershed and the destruction of wetlands remove this “sponge” eff ect (Figure 3). Turning natural areas into farms and cities oft en reduces water quality.

fl ood plain: an area of fl at land that is fl ooded when a river overfl ows its banks

Figure 2 The ice jam under this bridge is blocking the fl ow of water, which may lead to fl ooding of the surrounding area.

Figure 3 Trees help to hold water in an area. When the trees are removed, the water leaves, often taking some of the soil with it.


To learn more about fl oods and droughts,


tiny piece of rock

air space

layer of water

tiny piece of rock

air space

layer of water

12.4 Floods and Droughts 327NEL

Figure 4 When soil is loosely packed and has large air spaces, water can pass through easily.

SoilSoil is made up of tiny pieces of rock and organic material. Th ese components generally pack together loosely, leaving open spaces that fi ll with water and air (Figure 4). If soil does not receive rain and decaying vegetation regularly, it can lose its ability to support life. Th e soil suff ers when humans manage the land poorly. Poor land-use practices include clear-cutting of forests, overgrazing by farm animals, and poor construction methods. Th e soil’s nutrients are used up, and the soil becomes less productive and cannot support life.

Soil CompactionSome soils, such as clay, have very small air spaces. Soil scientists call these “compacted soils” (Figure 5). Water will oft en collect in pools on the surface of compacted soils, or run off to lower areas. What will happen to an area with loosely packed soil if people start to walk on it regularly? If one of the areas that you tested in the Try Th is activity was an area where people frequently walk, you may have already observed the eff ects on the soil.

TRY THIS: Water Absorption by Soil

Does water sink into soil in some areas better than in other areas? This activity will help you to fi nd out.

Equipment and Materials: 3 open-ended containers; ruler; marker; beaker (600 mL); timing device; masking tape; water

1. Mark the outside of each container 3 cm from one end with a piece of masking tape.

2. Identify three spots in your schoolyard, one for each container. At each spot, use your foot to press the container into the soil until the soil level reaches the 3 cm mark.

3. Using the beaker, pour 500 mL of water into each container. Record the time it takes for all the water in each container to sink into the soil.

A. Which spot absorbed the water fastest? Slowest?

B. Compare the soil in the areas around the three containers. Are they different in any way?

C. Explain the different rates at which the water was absorbed.

SKILLS MENU: performing, observing, analyzing

Figure 5 Compacted soil

1. How are fl oods and droughts sometimes good for the natural environment?

2. Briefl y describe two strategies that would reduce the chances of homes being damaged by fl oods.

3. Does damming a river make the water source more sustainable? Explain your answer.

4. What human activities worsen the effects of drought?

5. How does soil compaction affect the water system?

CHECK YOUR LEARNING

Does your water issue for the Unit Task relate to fl oods and droughts? If so, how?Unit Task

2.B.7.2.B.7.SKILLS HANDBOOK


0 1500 3000 km

0–1000

Freshwater resourcesm3/capita/year

No data

1000–17001700–50005000–15 00015 000–50 00050 000–605 000


12.5 PERFORM AN ACTIVITY

Global Access to Safe Drinking WaterA large proportion of the world’s population lives in countries experiencing “water stress.” Water stress occurs when a population’s demand for water exceeds the amount of water available (Figure 1). Global population is increasing rapidly. Th e predicted population in 2025 will be almost 8 billion. More than 80 % of people will be living in developing countries. If renewable water resources remain unchanged, the number of countries that experience water stress will rise from 31 countries (today) to 48 in 2025. Will these countries be able to provide safe drinking water for their growing populations? Th at depends on how well they manage their water resources and educate their people about sustaining current water sources.

Questioning Hypothesizing Predicting Planning Controlling Variables

Performing Observing Analyzing Evaluating Communicating

SKILLS MENU

Figure 1 Global freshwater resources: quantity and distribution by region

PurposeTo represent the diffi culties in obtaining safe drinking water experienced by people in various countries.

Equipment and Materials 20 L of water in a large wide-mouth container • several diff erent-sized containers • plastic bucket•

20 L of water in a large wide-mouth container

several different-sized containers

plastic bucket

Critical LiteracyHow can you compare the attitudes and beliefs of people in different situations? Try looking at a situation from someone else’s point of view. Work with a partner to compare how people in Canada and people in Ethiopia might feel about• selling water versus giving it

away• the amount of water

available daily• how people in each country

use and conserve water



12.5 Perform an Activity 329NEL

Procedure1. You will be placed into “continent” teams by

your teacher. In your notebook, record the number of classmates assigned to each team.

2. In your notebook, sketch the area where you are performing the activity. On your sketch, mark the location of each team and the location of the two 20 L containers of water. Th ese are the “water sources” in this activity.

3. Your teacher will give your team one of the plastic containers and a bucket. Your teacher will also identify your water source.

4. Place your bucket in your team’s area. Choose the order in which your team members will “race” to your water source to fi ll your empty container with water. Th e fi rst person holds the container.

5. When your teacher gives the signal, have the fi rst member of your team “race” to your water source, fi ll the empty container (without spilling), return to your team, and pour the collected water into your bucket (Figure 2).

6. Pass the empty container to the next member of your team, who then repeats the process.

7. Stop when your teacher signals an end to the activity.

8. Observe and record the volume of water in each team’s bucket.

Analyze and Evaluate(a) Compare the volume of water obtained by

each team. (b) How did you feel as you participated in this

race? Explain your answer.(c) Do you think the relay race was fair?

Explain your answer.(d) How does this race refl ect the eff orts of

people in diff erent countries to obtain enough water for their needs?

Apply and Extend(e) How could you change the rules of the race

to make it fair for each participating team? Justify each change that you recommend.

(f) Discuss each change that you recommended in (e) with another student. Th ink about whether any of your proposed changes in the model could be implemented in a real-world situation (Figure 3).

Never run in the science classroom.

Figure 2 The aim is to be the fi rst team to fi ll your “continent’s” bucket with fresh water.

Figure 3 Are there changes that can be made to make water supplies “fair” worldwide?

2.B.8.2.B.8.SKILLS HANDBOOK



12.6 Water Is Life Th e availability of clean water is a matter of life and death (Figure 1). Water also determines how people live their lives. Over 1 billion people on Earth (one-sixth of the world population) do not have access to safe drinking water. Other people waste it daily. Water can be obtained for free or at a very high cost.

Th e world’s fi rst “Water Day” was March 22, 2005. Th is day marked the start of the “Water for Life” decade. Th e focus for this 10-year period is to make people around the world aware of the fresh water shortage threatening some communities and countries. Th e United Nations (UN) announced a target for water and sanitation:

To reduce by half the number of people that do not have access to safe drinking water and basic sanitation by the year 2015.

Th e UN is encouraging the international community to meet this target. Do you think this is an achievable goal?

Is Water a Basic Human Right?Th e UN Committee on Economic, Social, and Cultural Rights made a statement on water in its Millennium Declaration of 2000. Th e committee proposed that access to suffi cient clean water is a fundamental human right. Access to clean water is crucial to everyone for health, food production, and economic development. Every country in the world is a member of the UN. Th ey all agree with this declaration. Why, then, are the “have water” nations and their corporations treating clean water as a product that can be bought and sold? Selling water for profi t makes water available only to those who can aff ord it, rather than making water available for everyone.

Figure 1 (a) We all need water to survive. (b) Poor quality water can cause many health problems in a community, including the sores on this Canadian child’s hands.

1. Describe, in your own words, the United Nations Millennium Declaration on water rights.

2. Explain how buying and selling water confl icts with the idea that access to clean water is a basic human right.

CHECK YOUR LEARNING

(b)(a)


SCIENCE

331NEL

Using Solar Power for Cleaner Water

Each year, 4 billion people in the world suffer from diarrhea. Over half of these people die—many of them children. The reason for this vast problem is that many people do not have access to clean drinking water. Instead, they get their water from ditches, rivers, and ponds that may contain feces and disease-causing bacteria (Figure 1).

Much of this suffering could be avoided by using a simple, inexpensive way to clean water: the Sun! Leaving water in bright sunlight can destroy bacteria in the water. Just as too much UV light from the Sun can damage our skin cells and cause cancer, UV light damages and kills bacterial cells. Thermal energy from the Sun also helps to kill bacteria by heating up the water. Leaving a clear bottle of water in the sunlight can turn dangerous water into safe water.

Scientists have developed a simple system for using the Sun to clean water. They call this system SODIS, which stands for SOlar DISinfection. First, water is poured into clear plastic bottles. Then, the bottles are laid out on tables in the sunlight (Figure 2). If it is a sunny day, the water will be safe to drink before the Sun goes down in the evening. If it is a cloudy day, the water will be safe to drink in two days because it takes twice as long for enough UV rays to penetrate the water in the bottles.

SODIS only works within 35° latitude of the equator, where the Sun’s rays are direct enough to provide the UV energy needed. However, if families in tropical countries use it widely, SODIS will save millions of lives.

Figure 1 Many people in developing countries do not have access to clean drinking water.

Figure 2 A woman arranges bottles of water on the family SODIS table.


To learn more about the “clean water revolution” and how to get involved,


0 1500 3000 km

600–800

Water Footprint(m3/capita/year)

1800–2100

800–10001000–12001200–13001300–15001500–1800

No data2100–2500


PERFORM AN ACTIVITY12.7Water FootprintsYou might have heard the term “ecological footprint.” Your ecological footprint is a measure of how much land and water you require to produce the things you consume and to remove the wastes you produce.

Th e ecological footprint of a country is composed of the footprints of its people, considering all the land and water resources they use. Th is activity will focus on the “water footprints” of the world’s nations. Look at Figure 1 carefully. Is there a connection between the regions of the world that have a large water footprint and regions that have access to unlimited freshwater resources?

Questioning Hypothesizing Predicting Planning Controlling Variables

Performing Observing Analyzing Evaluating Communicating

SKILLS MENU

Figure 1 Average national water footprint per capita (m3/capita/yr, or cubic metres used by each person in a year). Green means that the nation’s water footprint is equal to, or smaller than, the global average. Countries coloured brown have a water footprint greater than the global average.


12.7 Perform an Activity 333NEL

PurposeTo compare the water footprints of “water-rich” countries with those of “water-poor” countries.

Equipment and Materialscomputer with Internet access•

Procedure 1. What determines the size of a water

footprint? Search several websites for information about factors that aff ect a water footprint’s size.


2. Search for information that compares the size of Canada’s (or North America’s) water footprint to that of another region. Record all of the data that you collect and the sources you use.

Analyze and Evaluate(a) Describe the size of the water footprint for

Canada. Compare Canada’s water footprint to that of another region.

(b) Identify three factors that, according to your data, contribute to the size of Canada’s water footprint.

Apply and Extend(c) Work in small groups to discuss the

three factors identifi ed in (b). Make recommendations on how to reduce each of them. How would each recommendation reduce the size of Canada’s water footprint (Figure 2)?

(d) Would your recommendations for water footprint reduction make water sources more sustainable? Explain your answer.

(e) How might the national average of water use in Canada compare to the water use by individual populations in Canada? Suggest how communities that are poor, land-locked, inner-city, or on reserves might use water diff erently from communities that have unlimited access to clean water.

computer with Internet access

Figure 2 Is there anything that you could do around your home to reduce your water footprint?

Not everyone in the world has equal access to drinking water. How do water footprints relate to the issue you are considering for the Unit Task?

Unit Task

7.C.7.C.SKILLS HANDBOOK

3.I.3.I.SKILLS HANDBOOK


cool air sinks

warm airpushed upward

land

sea

BIG Ideas

Water is crucial to life on Earth.

Water systems infl uence climate and weather patterns.

Water is an important resource that needs to be managed sustainably.


Looking Back

CHAPTER

SUMMARY

✓

✓

✓

Water, Weather, and Climate

The climate of a region, and the weather on any particular day, are affected by large bodies of surface water.

Water • has a high heat capacity. It can absorb or release a lot of thermal energy without changing its temperature signifi cantly. Water is a heat sink.Lakes and oceans act as heat sinks, making the climate milder in • coastal and lakeside areas than in inland areas.Th e diff erence in temperature between air over water and air over • land causes convection currents in the air (wind).Floods occur when there is too much rain and meltwater; streams • and rivers overfl ow their banks. Droughts occur when there is not enough rain; streams, rivers, and lakes dry up.

Climate affects water’s temperature and changes of state on Earth.

Near the cold North and South Poles, precipitation is in the form • of snow. Th e snow builds up over centuries, forming glaciers, ice sheets, and icecaps.Near the hot equator, precipitation is in the form of rain.• Between the equator and the poles, precipitation may be in the • form of snow for some of the year, but this snow melts each spring. Th e warmer the climate, the more easily surface water evaporates, • which may lead to droughts.

Research skills can be used to assess issues related to local and global water supply.

Diff erent media sources can be used to research issues related to • exporting water.Media sources • present diff ering opinions on water issues.

12


Sea Ice Concentration (percent)September 16, 2007

1979-2000 median minimum

2005 minimum

500 km

2007 minimum

VOCABULARY

weather, p. 316

climate, p. 316

heat capacity, p. 317

heat sink, p. 318

convection, p. 318

global warming, p. 321

fl ood plain, p. 326

Chapter 12 Summary 335NEL

Global warming is affecting water systems around the world.

Global warming is causing glaciers• , ice sheets, and icecaps to melt. Th is results in more water fl owing into the oceans.Global warming • is increasing the temperature of Earth’s surface water.Sea levels are rising as the global temperature increases because • warmer water has a greater volume than cooler water.

The long-term sustainability of water systems depends on how well we manage and care for water.

Water use must be carefully planned and managed to ensure that • there will be enough clean water to meet the needs of people around the world.Human activity aff ects the fl ow of water and the quality of water • in a local water system. Withdrawing water for drinking, irrigation, and export reduces our water supply. Turning natural areas into farms and cities oft en reduces water quality.Reducing the size of Canada’s water footprint can help achieve • sustainability.

The skills of scientifi c inquiry can be used to compare water use around the world.

Water footprints can be used to compare water use among • countries.Water footprints can be used to identify areas in which we can • reduce water use.


Lake Huron

UNITEDSTATES

CANADA

Toronto

Lake Ontario

Lake Erie

0 50 100 km

W E

N

S

GrandBend

Cambridge


CHAPTER

REVIEW K/U Knowledge/Understanding T/I Thinking/InvestigationC Communication A Application

The following icons indicate the Achievement Chart categories:

What Do You Remember?1. (a) Defi ne the term “heat capacity.”

(b) How does the heat capacity of water compare to the heat capacity of rock?

(c) Explain how the heat capacity of water makes water a good “heat sink.” K/U

2. (a) How are glaciers, ice sheets, and polar icecaps formed?

(b) Explain why glaciers form in some regions but not in others. K/U

3. What causes glaciers to move? K/U

4. (a) Describe three diff erent kinds of fl ood and how they occur.

(b) What is a fl ood plain? K/U

5. Describe two circumstances that might result in a drought. K/U

What Do You Understand?6. Explain how weather and climate are similar

and how they are diff erent. K/U

7. Describe two characteristics of water that make it an eff ective heat sink. K/U

8. Why is there oft en a breeze on the shore of a large lake or an ocean? K/U

9. Explain how each of the following factors can aff ect the climate of a region:(a) distance from a large body of surface

water(b) distance from the equator(c) human activity (Name and describe

one activity.) K/U

10. (a) Describe one positive eff ect that a fl ood might have on a watershed.

(b) Describe one way to reduce the chance of a fl ood damaging homes.

(c) Describe one positive eff ect of a drought. K/U

11. Draw two diagrams showing the arrangement of tiny pieces of rock and organic matter in soil. Your fi rst diagram should represent the soil in an area where surface runoff aft er rainfall is severe. Your second diagram should represent the soil where the same rainfall produces no runoff at all. K/U C A

12. Global warming can lead to higher sea levels. Describe two separate processes that result in higher sea levels. K/U

13. Why is it diffi cult for regions to prevent the export of water from their watershed? K/U A

14. (a) October and November temperatures are 8 to 10 °C higher in Grand Bend and in Toronto than they are in Cambridge (Figure 1). Explain this diff erence in temperature.

(b) How would you expect the temperatures to compare in April? Explain T/I A

Solve a Problem!15. Imagine that you live in a developing country

where the nearest freshwater source is 10 km away from your home. (a) How would this aff ect your water use?(b) Design a technology that would make

water more accessible, and explain how it would change your water use. T/I A

12

Figure 1


Chapter 12 Review 337NEL

To do a self-quiz Go to Nelson Science

Create and Evaluate!16. “Boil Water Advisories” are issued to

communities when the quality of their tap water is in doubt. (a) Research an incident in Ontario in which

a “Boil Water Advisory” was issued. (b) Find out the reasons for the advisory,

what was done to correct the problem, and how long the advisory was in place.

(c) As you collect the information, consider the sources. What is the perspective of each writer? Are the reports objective and unbiased? Evaluate each source.

(d) Summarize your fi ndings, including your evaluation of the sources, in a presentation style of your choice. T/I C A


17. Th ere are dams across most of the world’s rivers (Figure 2). (a) Compare the pros and cons of damming

a river.(b) Under what circumstances would the pros

outweigh the cons?(c) Under what circumstances would the cons

outweigh the pros? T/I A

18. (a) What does “water stress” mean?(b) Create a poster to educate Canadians

about this situation. Include in your poster at least one action that people (either in a “stressed” area or elsewhere) could take to improve the situation. T/I C

19. (a) How does the UN Millennium Declaration on water rights apply to First Nations people in Canada?

(b) Rewrite in your own words the part of the UN Millennium Declaration that relates to water rights. Design and create a pamphlet to increase awareness of this declaration within your school and community. T/I C A

20. As part of an action plan to reduce the size of Canada’s water footprint, one of your classmates suggests that all gasoline service stations should provide free automated car washes. Your classmate argues that this would save water because automated car washes use less water per vehicle than washing a car at home. Do you think this idea could work? Why or why not? Plan a grassroots marketing strategy to increase awareness of the plan. To whom would this strategy be directed? T/I A

Refl ect on Your Learning21. (a) How has this chapter changed your

thinking about water?(b) Which single fact in this chapter surprised

you the most? Why?(c) Do you plan to make any changes to

your lifestyle as a result of what you have learned in this chapter? Explain.

22. Th ink back to the Key Question on the fi rst page of this chapter.(a) In a brief paragraph, answer the Key

Question. You may use diagrams.(b) Write one or two more questions about

the topic of this unit that you would like to explore.

Figure 2


UNIT DUnit Task

338 Unit D • Water Systems NEL

ScenarioIndividuals, groups, and governments around the world are concerned about the availability of safe freshwater sources (Figure 1). Corporations are also starting to express an interest in the issue.

An international corporation produces a wide range of beverages. Many of these drinks are aimed at the youth market. To improve its image, the corporation has announced an award for a solution to an existing or potential water system issue. Possible issues include

an inadequate supply of safe drinking water in • a communitypoor water quality in a watershed• unnecessary use of water• Any individual or group can submit a detailed

proposal for solving one of these issues, or any other relevant water issue, in Canada or elsewhere.

To qualify for the award, you must do the following:

1. Choose an issue related to the limited availability of safe, clean freshwater sources.

2. Prepare and test an action plan to solve the issue. ORDesign and build a prototype of a device that will improve water quality. Th e device should remove at least two signifi cant contaminants from a freshwater source.

3. Write a report in the form of a media release. Your report should describe your attempt and include data (collected in any trials) that will determine the success of your attempt.

Design BriefIn your design brief, include a step-by-step outline of how you intend to accomplish your task.

Equipment and MaterialsMake a list of the equipment and materials you will use to complete each part of the task. Use as many found materials as possible. Avoid using pieces from store-bought kits unless you are using them in new ways. You will be able to use limited amounts of school equipment.

Research and ConsiderIf you have chosen to prepare and test an action plan, discuss your ideas with peers, your teacher, a parent, or a mentor in the community. Research policies, protocols, or legislation that apply to your issue. If laws or policies exist, are they being monitored or enforced?

Solving a Water Issue

Figure 1 A reliable supply of clean water is a worldwide concern.


Unit D Task 339NEL

If you have chosen to build a device, investigate current devices that are used to improve water quality. If you fi nd ideas that you would like to use, change them in some way to make them your own. Brainstorm ideas with thumbnail sketches, then choose one that you would like to develop. Consider the availability of equipment and materials.


Plan and Construct Provide a detailed description of the steps you will follow to implement your action plan. OR Build a device to improve water quality using your design. Before building, you should do the following:

Complete a scale drawing of your device.• Create a step-by-step plan for building the • device.Produce a list of job responsibilities for each • group member.Ask your teacher to approve the list of • equipment and materials and the building plan before you begin.

Test and ModifyAllow enough time to collect data or test your device, and to make changes to your plan or device. Keep accurate notes on any changes that you make, and any additional data that you collect aft er the change is made.

EvaluateDid your action plan achieve the intended result? Did your prototype eff ectively remove contaminants from the water? Have you met all of the criteria? Use the Assessment box to help you.

CommunicateYour media release/report should include the following elements:

the existing or potential water issue that you • are hoping to solvea brief description of your plan or device• how and why your plan or device will work • to solve your chosen issue data to support your claim• a brief summary outlining why you should • win the award

• state the issue or design problem

• identify several possible solutions

• develop a plan or device for solving the issue

• carry out your plan or build your device

• collect data to determine the effectiveness of your plan or device

• make or identify modifi cations that could be made to improve the effectiveness of your plan or device

• evaluate your plan or device

• use the concepts and terminology of the unit to communicate the effectiveness of your plan or design to the media in your press release

• communicate your ideas to your audience in your media release/report

AssessmentYou will be assessed on how well you

4.B.2., 4.C.4.B.2., 4.C.SKILLS HANDBOOK


UNIT DUnit Review


The following icons indicate the K/U Knowledge/Understanding T/I Thinking/InvestigationAchievement Chart categories: C Communication A Application

5. (a) Sketch or describe the continental divides in North America.

(b) What term is used to describe the regions between the continental divides? K/U C

6. Name two factors that aff ect the size of glaciers, ice sheets, and polar icecaps. K/U

7. (a) What is “turbidity”?(b) List two possible causes of turbidity in

water. K/U

What Do You Understand?8. In winter, is an inland city likely to be warmer

or colder than a coastal city? Why? K/U

9. Create a concept map to illustrate the fl ow of water through the water cycle. K/U C

10. Explain how precipitation aff ects the supply of groundwater. K/U

11. Describe the role of micro-organisms in the sewage treatment process. K/U C

Unit D Review Questions

What Do You Remember?1. In your notebook, complete Table 1. K/U

Table 1

Characteristic Salt water Fresh water

Where do you fi nd it?

What is in it?

How do you remove contaminants so that you can drink it?

2. Name and describe three changes of state in the water cycle. K/U

3. List one advantage and one disadvantage of spreading salt on roads when they are snow-covered or icy. K/U

4. Draw and label a diagram to show the location of surface water, groundwater, an aquifer, and the water table. K/U C

Make a SummaryIn Unit A, you learned that any system has “inputs” and “outputs.” Human-made systems are designed to accomplish specifi c tasks.

Work in small groups. Each group will need a marker and a piece of chart paper. On the chart paper, write the title “Water Systems.” Below this title, draw a table with fi ve columns. Write headings for the columns as shown in Figure 1.

List as many “inputs” as you can, completing the “output”, “eff ect”, “pro,” and “con” columns for each input. Discuss each suggestion, and brainstorm how to fi ll in the columns.

When you have completed your table, prepare to present it to the rest of the class.

Water Systems

Input Output Effect Pro Conmelting of replaces surface damages property;snow in the and groundwater adds turbidity tospring runoff flooding supplies water

Water Systems

Figure 1


Unit D Review 341NEL

12. Use an atlas to draw a map of North America. (a) Research how much of the continent was

covered in ice during the last ice age. On your map, sketch the southern boundary of the polar icecap at this time.

(b) Research how much of the continent is covered in ice today. Indicate this boundary on your map.

(c) What conclusion can you make about climate change in North America since the last ice age? K/U C


13. (a) How do herbicides and pesticides enter local water systems? (Figure 2)

(b) How can we stop these chemicals from entering the water system? Explain. K/U A

14. Fertilizer that enters the water system can cause an algal bloom. Research to fi nd out how fi sh are aff ected when this happens. K/U A


15. If an ocean current along the East Coast of Canada were to suddenly change from warm to cold, what climate changes might you notice along the coast? Why? K/U A

16. Two Canadian cities are approximately the same distance from the equator. Both are close to bodies of water. Examine the data in Table 2. Which city do you think has the larger body of water next to it? Explain. K/U

Table 2 Average Monthly Temperatures for Two Canadian Cities

Month

Average monthly temperature of

City 1 (°C)

Average monthly temperature of

City 2 (°C)

January −7 −6

February −6 −6

March −1 −2

April 6 4

May 12 9

June 17 15

July 21 18

August 20 18

September 15 14

October 9 9

November 3 3

December −3 −3

17. A landowner discovers that her well has run dry during a summer in which very little rain has fallen. She arranges for a tanker truck of drinking water to be delivered and pumped into the dry well. She then measures the depth of water in the well. A few days later, having used very little water, she fi nds that the water level in the well has dropped several metres. Explain where the water might have gone. T/I A

Figure 2



18. Wetlands are drained to increase the area of farmland or to allow for urban growth. How does draining a wetland aff ect other parts of a watershed? Research this question and present your fi ndings. T/I C


19. Illustrate the path followed by toilet water from when the toilet is fl ushed until this water is returned to a freshwater source. Add notes to your illustration. Th e notes should explain what contaminants are present and what happens to the water at each stage. K/U C

Solve a Problem!20. Choose one contaminant that was discussed

in this unit. (a) Describe where and how your pollutant

can enter the water cycle.(b) Describe how you would test for the

presence of that pollutant. (c) Describe a method of removing your

pollutant from the water supply. K/U T/I

21. A farmer wants to compare the rate at which soil from two diff erent parts of the farm will absorb water. Th e farmer has two empty cans from the recycling box, and he uses a nail to punch fi ve holes in the bottom of each can. Design a fair test to compare the absorption rate of two soil samples using these two cans.

T/I A C

22. (a) Research to fi nd information about a recent fl ooding disaster. Th e fl ood could be local, somewhere else in Canada, or in another country (Figure 3).

(b) From your research, describe any human activity that may have worsened the fl ood.

(c) What could be done to lessen the eff ect of another similar fl ood? K/U T/I


23. Design an investigation that would answer the question: “Do ocean water and fresh water evaporate at the same rate?” T/I C

24. E. coli bacteria infected the drinking water of Walkerton in 2000. Research the short-term and long-term eff ects of E. coli infection on human health. Present your fi ndings in a poster. T/I C


Figure 3


Unit D Review 343NEL

Create and Evaluate!25. (a) Do you think that you use more, less, or

about the same volume of water as most Canadians? Explain your answer.

(b) Evaluate your personal water consumption. Do you think that the volume you use is reasonable? Explain your answer. T/I

26. Th e United Nations has declared that access to suffi cient clean water is a fundamental human right. Canada has the Charter of Rights and Freedoms, but it does not deal with the right to access clean water. Working in a small group, propose a Charter of Water Rights for Canada. Include three to fi ve water rights to which you think every Canadian is entitled. T/I C

27. Bioremediation can quickly and thoroughly remove contamination from water in the environment. It is also fairly inexpensive. It cannot, however, remove all contaminants. Choose a specifi c bioremediation technology and research how it works and how eff ective it is. Consider its risks and benefi ts, and assess its impact on the local water system. Should it be used in your neighbourhood? Present your position in a letter to a local newspaper or a local politician. T/I C


28. Desalination is becoming more cost-eff ective. Research a technology used for desalination. What are the risks and benefi ts of this technology? Under what circumstances is it a good choice? Present your fi ndings in an information brochure as if you run a desalination company. T/I C


29. Stormwater runoff in some cities is piped into the sewer system. It mixes with household wastewater and is treated at a wastewater treatment facility. In other urban areas, stormwater runoff is directed into pipes with holes in them, so the water drains into the soil. (a) Research the costs and benefi ts of each

approach. Decide which approach you think is best.

(b) Find out what happens to roof runoff in your area. Create a public service announcement or poster supporting your point of view and (if necessary) urging people to change how their roof runoff is handled. T/I C


Refl ect on Your Learning30. Recall the actions that you took to reduce

your personal water footprint.(a) Do you plan to continue with these

actions? Why or why not?(b) Do you think it will be easy or diffi cult

for you to reduce your footprint?(c) What would help you to continue with

your water-reduction actions?


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