© 2010 Pearson Education Canada

11Freshwater Systems

and Water Resources

PowerPoint® Slides prepared by Thomas Pliske, Heidi Marcum, and Nicole Lantz

This lecture will help you understand:

• Water and the hydrologic cycle

• Water’s distribution on Earth

• Freshwater ecosystems

• Use and alteration of freshwater systems

• Problems of water supply and solutions

• Problems of water quality and solutions

• How wastewater is treated

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HOUSEKEEPING ITEMS I will hand back the quizzes today for Section 1, and on

Wednesday for Section2. If you have any questions, you can ask me afterwards.

Did anyone go see End of the Line? A current controversy for media analysis: whether to tap

natural gas in shale deposits in north-eastern BC. There are three items I want to mention. Tomorrow at

1:00 in the Building 370, Room 217, there are will be a forum on graduate school and what to expect. Geography profs and a couple of VIU alumni will be sharing their experiences. Second, later in the afternoon, I will be giving a talk on the social implications of climate change in Building 355, Room 203 at 4. Finally, on Thursday, since I have to miss Section 1's class, I have a guest speaker (Chris Foote) coming, who is one of BC's leading experts on salmon. If you are in that section, please make him welcome. If you are in Monday and Wednesday's section, please check him out if you are so inclined. It starts at 2:30 in Building 355, Room 203.

Turning the tap: the prospect of Canadian bulk water exports

“The wars of the twenty-first century will be fought over water.”

– World Water Commission Chairman Ismail Serageldin

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Freshwater systems• Water may seem abundant, but drinkable water is rare

• Freshwater = relatively pure, with few dissolved salts

- Only 2.5% of Earth’s water is fresh, and most of that is tied up in glaciers and ice caps

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FIGURE 11.1

Rivers and streams wind through landscapes• Water from rain, snowmelt, or springs forms streams,

creeks, or brooks

• These merge into rivers, and eventually reaches the ocean

- Tributary = a smaller river slowing into a larger one

- Watershed = the area of land drained by a river and its tributaries

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Rivers shape the landscape

• If there is a large bend in the river, the force of the water cuts through the land

- Oxbow = an extreme bend in a river

- Oxbow lake = the bend is cut off and remains as an isolated, U-shaped body of water

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FIGURE 11.2

A river may shift course

• Floodplain = areas nearest to the river’s course that are flooded periodically

- Frequent deposition of silt makes floodplain soils fertile

• Riparian = riverside areas that are productive and species-rich

• Water of rivers and streams hosts diverse ecological communities

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Wetlands include marshes, swamps, and bogs• Wetlands = systems that combine

elements of freshwater and dry land

• Freshwater marshes = shallow water allows plants to grow above the water’s surface

• Swamps = shallow water that occurs in forested areas

- Can be created by beavers

• Bogs = ponds covered in thick floating mats of vegetation

- A stage in aquatic succession

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FIGURE 11.3

Wetlands are valuable• Wetlands are extremely valuable for wildlife (they serve

as very rich habitats)

• They slow runoff

- Reduce flooding

- Recharge aquifers

- Filter pollutants

• People have drained wetlands, mostly for agriculture

- Southeastern Canada has lost more than half of their wetlands

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Lakes and ponds are ecologically diverse

• Lakes and ponds are bodies of open, standing water

• Littoral zone = region ringing the edge of a water body

• Benthic zone = extends along the entire bottom of the water body

- Home to many invertebrates

• Limnetic zone = open portions of the lake or pond where the sunlight penetrates the shallow waters

• Profundal zone = water that sunlight does not reach

- Supports fewer animals because there is less oxygen

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A typical lake

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FIGURE 11.4

Lakes vary in their nutrients and oxygen

• Oligotrophic lakes and ponds = have low nutrient and high oxygen conditions

• Eutrophic lakes and ponds = have high nutrient and low oxygen conditions

• Eventually, water bodies fill completely in through the process of succession

• Inland seas = large lakes that hold so much water, their biota is adapted to open water

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Groundwater plays key roles in the hydrologic cycle

• Groundwater = precipitation that does not evaporate, flow into waterways, or get taken up by organisms

• Aquifers = Porous sponge-like formations of rock, sand, or gravel that hold groundwater

• Zone of aeration = spaces are partially filled with water

• Zone of saturation = spaces are completely filled with water

• Water table = boundary between the two zones

• Aquifer recharge zone = any area where water infiltrates Earth’s surface and reaches aquifers

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A typical aquifer

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FIGURE 11.5

There are two categories of aquifers

• Confined or artesian = water-bearing, porous rocks are trapped between layers of less permeable substrate (i.e., clay)

- Is under a lot of pressure

• Unconfined aquifer = no upper layer to confine it

- Readily recharged by surface water

• Groundwater becomes surface water through springs or human-drilled wells

• Groundwater may be ancient: the average age is 1,400 years

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Water is unequally distributed across Earth’s surface

• Many areas with high population density are water- poor and face serious water shortages

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FIGURE 11.7

Climate change will cause water problems and shortages• Climate change will affect the hydrologic cycle:

- Shift northward in mid-latitude rain belt

- Earlier snowmelt and spring runoff

- More evapotranspiration

- Drier summers in the interior continental region

• Additional impacts:

- Warmer rivers (impacting fish)

- Lower water levels in Great Lakes

- Higher ocean water levels11-18

How we use water

• We have achieved impressive engineering accomplishments to harness freshwater sources

- 60 % of the world’s largest 227 rivers have been strongly or moderately affected

- Dams, canals, and diversions

• Consumption of water in most of the world is unsustainable

- We are depleting many sources of surface water and groundwater

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Water supplies houses, agriculture, and industry

• Arid countries use water for agriculture

• Developed countries use water for industry

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FIGURE 11.8

Different types of water use

• Consumptive use = water is removed from an aquifer or surface water body, and is not returned

• Non-consumptive use = does not remove, or only temporarily removes, water from an aquifer or surface water

- Electricity generation at hydroelectric dams

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We have erected thousands of dams

• Dam = any obstruction placed in a river or stream to block the flow of water so that water can be stored in a reservoir

- To prevent floods, provide drinking water, allow irrigation, and generate electricity

- 45,000 large dams have been erected in more than 140 nations

• Only a few major rivers remain undammed

- In remote regions of Canada, Alaska, and Russia

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A typical dam

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FIGURE 11.9

Is the Three Gorges Dam worth it?

Do you think the projected benefits from China’s great Three Gorges Dam (energy and water for industry and municipalities) will be worth the risk to the environment, and the social disruption of displacing more than a million people?

weighing

the issues

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Benefits and drawbacks of dams

• Benefits:

- Power generation

- Emission reduction

- Crop irrigation

- Drinking water

- Flood control

- Shipping

- New recreational opportunities

• Drawbacks:

- Habitat alteration

- Fisheries declines

- Population displacement

- Sediment capture

- Disruption of flooding

- Risk of failure

- Lost recreational opportunities

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Some dams are now being removed

• Some people feel that the cost of dams outweighs their benefits

• Rivers with dismantled dams

- Have restored riparian ecosystems

- Re-established fisheries

- Revived river recreation

• In Canada only a few dams have been decommissioned but 500 dams have been removed in the U.S.

- Property owners who opposed the removal change their minds once they see the healthy river

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Dikes and levees are meant to control floods• Flooding is a normal, natural process

- Floodwaters spread nutrient-rich sediments over large areas

• Floods also do tremendous damage to property• Dikes and levees (long, raised mounds of earth) along the

banks of rivers hold rising waters in channels• Levees can make floods worse by forcing water to stay in

channels and overflow

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We divert – and deplete – surface water to suit our needs (example of Colorado River)

• Diversion has drastically altered the river’s ecology• What water is left after all the diversions comprises

just a trickle into the Gulf of California

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FIGURE 11.12

Flood protection at what cost?

The Red River Floodway protected the City of Winnipeg during the massive flood of 1997. However, this diversion of flood waters from the city’s core put other villages at risk of flooding that would not normally have been in the path of the flood.

• Do you believe it is worthwhile to protect the costly resources, as well as the people of the City of Winnipeg, even if it means sacrificing some other areas to the flood?

• What would you do to protect or compensate people in those other areas?

weighing

the issues

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The Aral Sea• Once the fourth-largest lake on

Earth

- lost over 80% of its volume in 45 years from diversion

• Consequences

- Lost 60,000 fishing jobs

- Pesticide-laden dust from the lake bed is blown into the air

- The cotton cannot bring back the region’s economy

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FIGURE 11.13

Can the Aral Sea be saved?

People may have begun saving the northern part of the Aral Sea

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FIGURE 11.13

Inefficient irrigation wastes water

• Today, 70% more water is withdrawn for irrigation than in 1960

- The amount of irrigated land has doubled

- Crop yields can double

11-32FIGURE 11.14

Most irrigation is highly inefficient

• Only 45% of water is absorbed by crops via “flood and furrow” irrigation

• Overirrigation leads to waterlogging, salinization, and lost farming income

• Most national governments subsidize irrigation

• Water mining = withdrawing water faster than it can be replenished

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Areas where water use exceeds supply

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FIGURE 11.15

Wetlands have been drained for a variety of reasons

• Promote settlement and farming

• Seen as useless “swamps”

• Ramsar Convention

- Global concern for wetland loss and degradation

- Promotes local, regional, and national actions and international cooperation

• 90% of original wetlands in southern Canada have been lost

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We are depleting groundwater

• Groundwater is easily depleted

- Aquifers recharge slowly

- 1/3 of world population relies on groundwater

• As aquifers become depleted

- Water tables drop

- Salt water intrudes in coastal areas

- Sinkholes = areas where ground gives way unexpectedly

- Some cities (Venice, Mexico City) are slowly sinking

- Wetlands dry up

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The price of a litre

• Do you drink bottled water? Why?

• What do you pay for a litre of bottled water? What do you pay for a litre of gas at the pump?

• What do you think should be reflected in these prices?

• What price do you think was paid for the water by the company that bottled it?

• What about the source of the water you consume— is it groundwater and, if so, is its source adequately protected?

• And what about the plastic waste that is generated?

weighing

the issues

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Will we see a future of water wars?

• Freshwater depletion leads to shortages, which can lead to conflict

- 261 major rivers cross national borders

- Water is a key element in hostilities among Israel, Palestinians, and neighbouring countries

• Many nations have cooperated with neighbors to resolve disputes

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Solutions can address supply or demand

• We can either increase supply or reduce demand

• Lowering demand

- Politically difficult in the short term

- Offers better economic returns

- Causes less ecological and social damage

• Increasing supply

- Water can be transported through pipes and aqueducts

- It can be forcibly appropriated from weak communities

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Desalinization “makes” more water

• Desalinization = the removal of salt from seawater or other water of marginal quality

- Distilling = hastens evaporation and condenses the vapor

- Reverse osmosis = forces water through membranes to filter out salts

• Desalinization facilities operate mostly in the arid Middle East

• It is expensive, requires fossil fuels, and produces concentrated salty water

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Agricultural demand can be reduced

• Look first for ways to decrease agricultural demand

- Lining irrigation canals

- Low-pressure spray irrigation that spray water downward

- Drip irrigation systems that target individual plants

- Match crops to land and climate

- Selective breeding and genetic modification to raise crops that require less water

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We can lessen residential water use in many ways

• Eat less meat

• Install low-flow faucets, showerheads, washing machines, and toilets

• Use automatic dishwashers instead of washing dishes by hand

• Water lawns at night, when evaporation is minimal, or replace lawn with native plants

• Xeriscaping = landscaping using plants adapted to a dry environment

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• Shift to processes that use less water

- Wastewater recycling

- Excess surface water runoff used for recharging aquifers

- Patching leaky pipes

- Auditing industries

- Promoting conservation/education

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We can lessen industrial water use in many ways

Economic approaches to water conservation

• End government subsidies of inefficient practices

- Let the price of water reflect its true cost of extraction

• Industrial uses are more profitable than agricultural

• Privatization of water supplies

- May improve efficiency

- Firms have little incentive to provide access to the poor

• Decentralization of water control may conserve water

- Shift control to the local level

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Freshwater pollution and its control

• Water for human consumption and other organisms needs to be…

- Disease-free

- Non-toxic

• Half of the world’s major rivers are seriously depleted and polluted

- They poison surrounding ecosystems

- Threaten the health and livelihood of people

• The invisible pollution of groundwater has been called a “covert crisis”

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Water pollution takes many forms

• Pollution = the release of matter or energy into the environment that causes undesirable impacts on the health and well-being of humans or other organisms

- Nutrient pollution

- Pathogens and waterborne diseases

- Toxic chemicals

- Sediment

- Thermal pollution

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Nutrient pollution

• Nutrient pollution from fertilizers, farms, sewage, lawns, golf courses

- Leads to eutrophication

• Solutions

- Phosphate-free detergents

- Planting vegetation to increase nutrient uptake

- Treat wastewater

- Reduce fertilizer application

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Eutrophication is a natural process, but…

• Human activities dramatically increase the rate at which it occurs

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FIGURE 11.20

Pathogens and waterborne diseases

• Enters water supply via inadequately treated human waste and animal waste via feedlots

• Causes more human health problems than any other type of water pollution

• Fecal coliform bacteria indicate fecal contamination of water

- The water can hold other pathogens, such as giardiais, typhoid, hepatitis A

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Pathogens cause massive human health problems• 1.1 billion people are without safe drinking water

• 2.4 billion have no sewer or sanitary facilities

• An estimated 5 million people die per year

• Solutions:

- Treat sewage

- Disinfect drinking water

- Public education to encourage personal hygiene

- Government enforcement of regulations

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Toxic chemicals

• From natural and synthetic sources

• Effects:

- Poisoning animals and plants

- Altering aquatic ecosystems

- Poor human health

• Solutions:

- Legislating and enforcing more stringent regulations of industry

- Modify industrial processes

- Modify our purchasing decisions

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Sediment pollution

• Sediment can impair aquatic ecosystems

- Clear-cutting, mining, poor cultivation practices

• Effects:

- Dramatically changes aquatic habitats

- Fish may not survive

• Solutions:

- better management of farms and forests

- avoid large-scale disturbance of vegetation

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Thermal pollution

• Warmer water holds less oxygen

- Dissolved oxygen decreases as temperature increases

- Industrial cooling heats water

- Removing streamside cover also raises water temperature

• Water that is too cold causes problems

- Water at the bottom of reservoirs is colder

- When water is released, downstream water temperatures drop suddenly and may kill aquatic organisms

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Water pollution comes from point and non-point sources• Point source water pollution = discrete locations of

pollution

- Factory or sewer pipes

• Nonpoint source water pollution = pollution from multiple cumulative inputs over a large area

- Farms, cities, streets, neighborhoods

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Freshwater pollution sources

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FIGURE 11.21

Scientists use several indicators of water quality

• Scientists measure properties of water to characterize its quality

- Biological indicators: presence of fecal coliform bacteria and other disease-causing organisms

- Chemical indicators: pH, nutrient concentration, taste, odor, hardness, dissolved oxygen

- Physical indicators: turbidity, color, temperature

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Groundwater pollution is a serious problem• Groundwater is increasingly contaminated, but is hidden

from view

- Difficult to monitor

- Out of sight, out of mind

- Retains contaminants for decades and longer

- Takes longer for contaminants to breakdown in groundwater because of the lower dissolved oxygen levels

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Sources of groundwater pollution

• Some toxic chemicals occur naturally

- Aluminum, fluoride, sulfates

• Pollution from human causes

- Wastes leach through soils

- Pathogens enter through improperly designed wells

- Hazardous wastes are pumped into the ground

- Underground storage septic tanks may leak

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FIGURE 11.23

Agriculture and industries pollute groundwater

• Agricultural pollution

- Nitrates from fertilizers

- Pesticides were detected in more than half of the shallow aquifers tested

• Manufacturing industries and military sites have been heavy polluters

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Legislative and regulatory efforts have helped reduce pollution

• Pollution legislation is enacted and enforced at the provincial level

• Federal government sets guidelines:

- Canadian Environmental Protection Act (transfers of hazardous materials)

- Fisheries Act (illegal to damage water that serves as a habitat for fish)

• The Great Lakes are one success story

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We treat our drinking water

• Technology has improved our pollution control

• Health Canada publishes standards for drinking water contaminants

- Local governments and water suppliers must meet

• Federal-Provincial-Territorial Committee on Drinking Water

• Before water reaches the user

- It is chemically treated, filtered, and disinfected

- There are different ways of doing it – chlorination, ozonation, treatment with UV rays

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It is better to prevent pollution than to mitigate the impacts after it occurs

• Other options are not as good:

- Filtering groundwater expensive

- Pumping, treating, and re-injecting aquifers takes too long

- Restricting pollutants above aquifers shifts pollution elsewhere

• Consumers choice drives environmentally friendly products and decisions

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Wastewater and its treatment• Wastewater = water that has been used by people in

some way

- Sewage, showers, sinks, manufacturing, storm water runoff

• Septic systems = the most popular method of wastewater disposal in rural areas

- Underground septic tanks separate solids and oils from wastewater, then microbes decompose the water

- Solid waste needs to be periodically pumped and landfilled

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Municipal sewer systems

• In populated areas, sewer systems carry wastewater

- Physical, chemical, and biological water treatment

• Primary treatment = the physical removal of contaminants in settling tanks (clarifiers)

• Secondary treatment = water is stirred and aerated so aerobic bacteria degrade organic pollutants

- Water treated with chlorine is piped into rivers or the ocean

- Some reclaimed water is used for irrigation, lawns, or industry

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A typical wastewater treatment facility

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FIGURE 11.24

Artificial wetlands can aid treatment

• Natural and artificial wetlands can cleanse wastewater

- After primary treatment at a conventional facility, water is pumped into the wetland

- Microbes decompose the remaining pollutants

- Cleansed water is released

• Nova Scotia government and Nova Scotia Agricultural College have three test sites

• Constructed wetlands serve as havens for wildlife and areas for human recreation

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Conclusion

• Obtaining future supplies of freshwater will be an environmental challenge

• With expanding population and increasing water usage, we are approaching conditions of widespread scarcity

• Water pollution is already harming freshwater around the world

• New approaches can help this situation

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QUESTION: ReviewThe area of a lake that contains open water that does not receive sunlight is called the _______zone.

a) Littoral

b) Benthic

c) Limnetic

d) Profundal

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QUESTION: ReviewA confined aquifer is defined as…?

a) An aquifer that traps porous rocks between layers

of less permeable substrateb) An aquifer that traps porous rocks under one

layer of less permeable substratec) An aquifer with porous rocks resting on bedrockd) An aquifer with no upper layer

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QUESTION: ReviewArid countries tend to use their water mostly for…?

a) Developing industriesb) Agriculturec) Householdsd) Export to rich countries

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QUESTION: ReviewWhich of the following statements is not a benefit of

dams?

a) Habitat alterationb) Power generationc) Crop irrigationd) Shipping

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QUESTION: ReviewPollution is defined as “the release of matter or energy

into the environment that causes ______”?

a) Undesirable impacts on human healthb) Undesirable impacts on other organismsc) Undesirable impacts on human well-beingd) All of the above are included in the definition

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QUESTION: ReviewWhich of the following is a nonpoint source of water

pollution?

a) A factoryb) Sewer pipesc) Agricultural fieldsd) All are nonpoint sources

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QUESTION: Review

Primary treatment of wastewater includes…?

a) Treating water with chemicalsb) Stirring and aerating waterc) Degradation of wastes by bacteriad) Physical removal of contaminants

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QUESTION: Interpreting Graphs and DataWhat is the relationship between water consumption and the amount of land that is irrigated?

a) Irrigation has grown more slowly than demand

b) Irrigation and demand have both increased

c) Growth of demand and irrigation will slow

d) Canada does not follow this graph

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FIGURE 11.14

QUESTION: Interpreting Graphs and Data

Which conclusion can you draw from this graph?

a) It is more water efficient to produce vegetables

b) It is more water efficient to produce meat

c) Vegetable and meat production are relatively alike in water consumption

d) There is little correlation between water consumption and our diet

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