Lecture Outlines
Chapter 15
Freshwater Systems
and Resources
Withgott/Laposata
Fifth Edition
© 2014 Pearson Education, Inc.
This lecture will help you understand:
 Water’s distribution and types of freshwater
ecosystems
 Use and alteration of freshwater systems
 Problems of water supply and solutions
 Classes of water pollution and solutions
 How drinking water and wastewater are treated
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© 2014 Pearson Education, Inc.
Central Case Study: Starving the Louisiana
Coast of Sediment
 Louisiana loses 65 km2 (25 mi2) of coastal wetlands
each year
 These ecosystems support a diversity of animals
 Protect coastal cities from damaging storms
 Created by sediments deposited at the end of the
Mississippi River
 The river accumulates material from water flowing off
of its 3.2 million km2 (1.2 million mi2) watershed
 The wetlands naturally compact, sink, and would
vanish
 New sediment is naturally added to maintain them
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© 2014 Pearson Education, Inc.
Case Study: Starving the Louisiana Coast of
Sediment
 The Mississippi River has been extensively modified
 River’s basin contains nearly 2000 dams
 The dams slow the water, and the sediment drops out
 Levees confine the river, making it deeper and faster
 Sediments shoot out rather then settle in the wetlands
 Oil and gas extraction has increased the rate of soil
compaction
 Solution: allow water from the Mississippi into the
coastal wetlands rather than shooting it into the Gulf
 This approach is rebuilding the Atchafalaya delta
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Freshwater Systems
 Water may seem abundant, but drinkable water is
rare
 Fresh water = water that is relatively pure, with few
dissolved salts—only 2.5% of total water
 Most is tied up in glaciers, ice caps, and aquifers
 One part in 10,000 is easily available for our use
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Freshwater Systems
 Water is renewed and recycled as it moves through
the water cycle
 Precipitation sinks into the ground or runs off into
rivers to form lakes or enter oceans
 Rivers interact with ponds, wetlands, and coasts
 Groundwater exchanges with rivers and ponds
 Water moves organisms, sediments, and chemicals
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© 2014 Pearson Education, Inc.
© 2014 Pearson Education, Inc.
Groundwater plays key roles in the hydrologic
cycles
 Surface water = water located atop Earth’s surface
 Groundwater = water beneath the surface held in pores
in soil or rock
 20% of the Earth’s freshwater supply
 Aquifers = porous, spongelike formations of rock, sand,
or gravel that hold water
 Zone of aeration = pore spaces partly filled with water
 Zone of saturation = spaces are filled with water
 Water table = boundary between the two zones
 Recharge zone = any area where water infiltrates Earth’s
surface and reaches aquifers
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© 2014 Pearson Education, Inc.
Groundwater plays key roles in the hydrologic
cycles
 Confined (artesian) aquifer = water-bearing,
porous rocks are trapped between less permeable
substrate (clay) layers
 Water here is under great pressure
 Unconfined aquifer = no upper layer to confine it
 Readily recharged by surface water
 Groundwater’s average age is 1400 years
 It may be tens of thousands of years old
 The Ogallala Aquifer is the world’s largest known
aquifer
 Current water use for irrigation is not sustainable
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© 2014 Pearson Education, Inc.
Surface water converges in river and stream
ecosystems
 Surface water accounts for just 1% of fresh water
 Vital for us and Earth’s ecological systems
 Runoff = water that flows over land
 Water merges in rivers and ends up in a lake or
ocean
 Tributary = a smaller river slowing into a larger one
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Surface water converges in river and stream
ecosystems
 Watershed (drainage basin) = the area of land
drained by a river system (river and its tributaries)
 Surface water becomes groundwater through
infiltration
 Groundwater becomes surface water through
springs or human-drilled wells
 1.9 trillion L (492 billion gal) each day in the United
States
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Hydrologic Cycle—Major Aspects
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Hydrologic Cycle—Crossword Puzzle
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Surface water converges in river and stream
ecosystems
 Rivers shape the landscape
 Braided river = an interconnected series of
watercourses that run through steep slopes
 Meandering river = river in flatter areas
 Water rounding a bend erodes soil from the outer bank
 Sediment is deposited on the inside of the bend
 Rivers form oxbows, areas where river bends become
exaggerated
 Oxbow lake = water body formed when erosion cuts
off and isolates the oxbow into a U-shape
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© 2014 Pearson Education, Inc.
Surface water converges in river and stream
ecosystems
 Floodplain = areas nearest to a river’s course that
are flooded periodically
 Frequent deposition of silt makes floodplain soils
fertile
 Good areas for agriculture
 Riparian = describing riverside areas that are
productive and species-rich
 Damming prevents large floods and river meanders
 Rivers and streams host diverse ecological
communities
 Algae, insects, fish, amphibians, birds, etc.
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Lakes and ponds are ecologically diverse
systems
 Lakes and ponds are bodies of open, standing water
 Littoral zone = region ringing the edge of a water body
 Rooted aquatic plants grow in this shallow part
 Benthic zone = the entire bottom of the water body
 Home to many invertebrates
 Limnetic zone = open portion of the lake or pond where
sunlight allows photosynthesis that produces oxygen
 Supports phytoplankton and zooplankton
 Profundal zone = water that sunlight does not reach
 Supports fewer animals because there is less oxygen
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© 2014 Pearson Education, Inc.
Lakes and ponds are ecologically diverse
systems
 Ponds and lakes may change over time
 Oligotrophic lakes and ponds have low-nutrient and
high-oxygen conditions
 Eutrophic lakes and ponds have high-nutrient and
low-oxygen conditions
 Eutrophication may result from human pollution
 Eventually, water bodies may fill completely in
through the process of succession
 The largest lakes are known as inland seas
 Great Lakes, the Caspian Sea, Lake Baikal
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Freshwater wetlands include marshes,
swamps, bogs, and vernal pools
 Wetlands = systems in which the soil is saturated
with shallow standing water with vegetation
 Freshwater marshes = shallow water with plants that
grow above the surface
 Swamps = shallow water in forested areas
 Can be made by beavers
 Bogs = ponds covered in thick floating mats of
vegetation
 A stage in aquatic succession
 Vernal pools = pools that form in spring then dry up
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© 2014 Pearson Education, Inc.
Freshwater wetlands include marshes,
swamps, bogs, and vernal pools
 Wetlands are extremely valuable for wildlife
 Louisiana’s coastal wetlands host 1.8 million
migratory birds each year
 They provide valuable ecosystem services
 They slow runoff, reduce flooding, recharge aquifers,
and filter pollutants
 People have drained wetlands, mostly for agriculture
 Southern Canada and the United States have lost
over half of their wetlands
 Wetlands are affected when we withdraw water,
build dams and levees, and introduce pollution
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Human Activities Affect Waterways
 Water is crucial for human health as well as farms
and factories
 Water is a limited but renewable resource
 Withdrawal of water in most of the world is
unsustainable
 We are depleting many sources of surface water and
groundwater
 One-third of the world’s people are affected by water
shortages
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Human Activities Affect Waterways
 We have achieved impressive engineering
accomplishments to harness fresh water
 60% of the world’s largest 227 rivers have been
strongly or moderately affected by dams, dikes, and
diversions
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Fresh water and human populations are
unevenly distributed across Earth
 Different areas possess different amounts of water
 People are not distributed in accordance with water
availability
 Asia has the most water of any continent but the least
water available per person
 Densely populated nations like Pakistan, Iran, India,
and Egypt face serious water shortages
 Fresh water is also unevenly distributed in time
 Seasonal rains lead to differences in water availability
 India can receive half of its rain in a single monsoon
 Dams are used to store water for dry times
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© 2014 Pearson Education, Inc.
Fresh water and human populations are
unevenly distributed across Earth
 Climate change will worsen conditions in many
region
 Altered precipitation patterns
 Melting glaciers causing early season runoff
 Intensified droughts and flooding
 One-third of the world’s major rivers experienced
reduced flow from 1948 to 2004
 Attributed largely to climate change
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Water supplies households, industry, and
especially agriculture
 Globally, 70% of water is used for agriculture, 20%
for industry, and 10% for residential and municipal
use
 Arid countries use more water for agriculture
 Developed countries use more water for industry
 Consumptive use = when water is removed from
an aquifer or surface water body and is not returned
 Irrigation = is the water applied to crops
 Nonconsumptive use = does not remove, or only
temporarily removes, water
 Electricity generation at hydroelectric dams
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Water supplies households, industry, and
especially agriculture
 Rapid population growth requires more food and clothes
 We use 70% more irrigation water than 50 years ago
 Irrigation can more than double crop yields
 18% of land is irrigated but produces 40% of our crops
 Irrigation is highly inefficient
 Water evaporates in “flood and furrow” irrigation
 Overirrigation leads to waterlogging and salinization
 Reducing world farm income by $11 billion
 Water use for agriculture is subsidized by governments
 Farmers have little incentive to conserve
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Excessive water withdrawals can drain rivers
and lakes
 In many places, we are withdrawing water at
unsustainable rates
 Many of the world’s major rivers regularly run dry
before reaching the sea
 The Colorado River often does not reach the Gulf of
California, threatening the future of cities and farms
that rely on its water
 Reduced flow drastically changes the river’s ecology
and plant community and destroys fish and
invertebrates
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Excessive water withdrawals can drain rivers
and lakes
 The Aral Sea in in present day Uzbekistan and
Kazakhstan was once the fourth-largest lake on
Earth
 It lost 80% of its volume in 45 years
 The two rivers leading into the Aral Sea were diverted
to irrigate cotton fields
 60,000 fishing jobs are gone
 Pesticide-laden dust is blown into the air
 Little cotton can grow on the salty soil
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Excessive water withdrawals can drain rivers
and lakes
 Worldwide, 15%–35% of water withdrawals for
agriculture are unsustainable
 Water mining = withdrawing water faster than it is
replenished
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© 2014 Pearson Education, Inc.
© 2014 Pearson Education, Inc.
Groundwater can also be depleted
 Groundwater is more easily depleted than surface
water
 Aquifers recharge slowly
 Used by one-third of all people
 As aquifers are mined, water tables drop
 In many areas, water tables are falling 1–3 m/year
 Salt water intrudes in coastal areas, making water
undrinkable
 Land above the aquifers subsides
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Groundwater can also be depleted
 Sinkholes = areas where ground gives way
suddenly
 Once the soil is compacted, aquifers can’t recharge
 Wetlands that get their water from groundwater
dry up
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© 2014 Pearson Education, Inc.
Groundwater supplies our bottled water
 Groundwater is being withdrawn for use as bottled water
 An average American drinks 29 gallons/year
 Sales topped $15 billion in the United States in 2012
 People drink bottled water for portability, convenience
 They think it tastes better or is healthier
 Bottled water is no better than tap water
 It is heavily packaged and travels long distances using
fossil fuels
 Energy costs of bottled water are 1000–2000 times
greater than those of tap water
 Only 25% of bottles are recycled in the United States
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People build dikes and levees to control floods
 Flooding = a normal, natural process where water spills
over a river’s banks
 Spreading nutrient-rich sediments over large areas
 In the short term, floods damage property
 Levees (or dikes) are the long, raised mounds of earth
along the banks of rivers that hold water in channels
 Stop flooding from most rains
 May make floods worse by forcing water to stay in
channels, build energy, and then overflow
 Dams prevent flooding and change a river’s nature
 Releasing water periodically simulates flooding
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© 2014 Pearson Education, Inc.
We divert surface water to suit our needs
 People divert water to farm fields, homes, and cities
 Water from the Colorado River is diverted to Denver, Las
Vegas, Los Angeles, and elsewhere
 In China, $62 billion is being spent to move water from the
Yangtze to the Yellow River
 Politically strong, water-poor areas forcibly take water
from weaker communities
 Los Angeles commandeered water from rural areas,
turning the environment into desert, creating dustbowls,
and destroying the economy
 In 1941, it diverted streams that fed Mono Lake
 Lake levels fell; salt concentrations doubled
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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
 They create reservoirs = artificial lakes
 Dams are built to prevent floods, provide drinking
water, allow irrigation, and generate electricity
 45,000 large dams have been erected in more than
140 nations
 Tens of thousands of smaller dams have been built
 Only a few major rivers remain undammed in remote
regions of Canada, Alaska, and Russia
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We have erected thousands of dams
 Dams produce a mix of benefits and costs
 The dam on the Yangtze River is the largest in the
world
 Its reservoir stretches for 616 km (385 mi)
 It provides flood control, passage for boats, and huge
amounts of electricity
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We have erected thousands of dams
 However, it cost $39 billion to build
 Flooded 22 cities and the homes of 1.24 million
people
 Submerged 10,000-year-old archaeological sites
 Drowned farmland and wildlife habitat
 The tidal marshes at the Yangtze’s mouth are eroding
 Pollutants may be trapped, making the water
undrinkable
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© 2014 Pearson Education, Inc.
Some dams are being removed
 Some people feel that the costs of dams outweigh their
benefits and are pushing to dismantle dams
 Removing dams will restore riparian ecosystems,
reestablish fisheries, and revive river recreation
 The Federal Energy Regulatory Commission (FERC)
renews licenses for dams
 If dam costs exceed benefits, the license may not be
renewed
 400 dams have been removed in the United States
 Some property owners who opposed the removal changed
their minds once they saw the healthy river
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© 2014 Pearson Education, Inc.
Wetlands are affected by human manipulations
of waterways
 Wetlands are being lost as we divert and withdraw
water, channelize rivers, build dams, etc.
 Wetlands have also been widely drained for
agriculture
 As wetlands disappear, we lose ecosystem services
 Filtering pollutants, wildlife habitat, flood control, etc.
 Many are trying to protect and restore them
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Wetlands are affected by human manipulations
of waterways
 The Ramsar Convention on Wetlands of
International Importance (1971) seeks the
conservation and wise use of wetlands in the context
of sustainable development
 1900 sites covering 185 million ha are protected
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Solutions to Depletion of Fresh Water
 Our use of fresh water has doubled over the last 50
years
 We can either increase supply or reduce demand
 Increasing supply through intensive extraction is
only a temporary fix
 Diversions increase supply in one area but decrease
it elsewhere
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Solutions to Depletion of Fresh Water
 Reducing demand is harder politically in the short
term
 International aid agencies are funding demand-based
solutions over supply-based solutions
 Offers better economic returns
 Causes less ecological and social damage
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Desalinization “makes” more fresh water
 Desalination (desalinization) = the removal of salt
from seawater or other water of marginal quality
 Distilling = evaporates and condenses ocean water
 Reverse osmosis = forces water through membranes
to filter out salts
 Over 2000 desalinization facilities operate around
the world, but there are problems with it
 Is expensive
 Requires large energy inputs (usually fossil fuels)
 Kills aquatic life at the water intakes
 Generates a concentrated salty waste
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https://sos.noaa.gov/Datasets/viewmovie.html?video=worlds_water_400
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Agricultural demand can be reduced
 Agriculture uses the largest amount of water of any use,
but a number of measures can be taken to reduce waste
 Line irrigation canals to prevent leaks
 Level fields to reduce runoff
 Use efficient irrigation methods
 Low-pressure spray irrigation sprays water downward
 Drip irrigation systems target individual plants
 Match crops to land and climate
 Eliminate water subsidies
 Use selective breeding and genetic modification to
produce crops that require less water
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We can lower residential and industrial water
use
 Residential water use can be cut in a number of ways
 Install low-flow faucets, toilets, etc.
 Rainwater harvesting = capturing rain from roofs
 Gray water = wastewater from showers and sinks that can
be used to water lawns
 Xeriscaping = using plants adapted to arid conditions
 Industries and municipalities can save water
 Shift to processes that use less water
 Recycle wastewater
 Use surface water runoff to recharge aquifers
 Find and patch leaky pipes
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Market-based approaches to water
conservation are being debated
 End government subsidies of inefficient practices
 Let the price of water reflect its true cost of extraction
 But since industrial uses are more profitable than
agricultural uses, poorer, less developed countries suffer
 Privatize water supplies: construction, maintenance,
management, and ownership
 May improve efficiency
 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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Nations often cooperate to resolve water
disputes
 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 neighboring countries
 Conflicts also exist between states in the United States
 Many nations have cooperated with neighbors to resolve
disputes
 India has agreements to co-manage rivers with Pakistan,
Bangladesh, Bhutan, and Nepal
 European nations on the Rhine and Danube signed treaties
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© 2014 Pearson Education, Inc.
Freshwater Pollution and Its Control
 People affect aquatic ecosystems and human health
when we introduce toxic substances and diseases
 Half of the world’s major rivers are seriously depleted
and polluted
 They degrade and poison surrounding ecosystems,
threatening the health and livelihood of people
 55% of U.S. streams and rivers are in poor condition
 The invisible pollution of groundwater has been called a
“covert crisis”
 Preventing pollution is easier and more effective than
mitigating it later
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Water pollution comes from point and nonpoint sources
 Pollution = the release of matter or energy that causes
undesirable impacts on the health and well-being of
humans or other organisms
 Water pollution comes in many forms and causes diverse
impacts
 Point sources = discrete locations of water pollution
 Factories, sewer pipes
 Addressed by the U.S. Clean Water Act
 Non-point sources = sources of pollution arising from
multiple inputs over larger areas (farms, city streets,
neighborhoods)
 The major source of U.S. water pollution
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© 2014 Pearson Education, Inc.
Water pollution takes many forms
 Toxic chemicals: waterways have become polluted
with toxic organic chemicals of our own making
 Pesticides, petroleum products, synthetic chemicals;
arsenic, lead, mercury, acid rain, acid
 Effects include poisoned animals and plants, altered
aquatic ecosystems, and decreased human health
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Water pollution takes many forms
 Scientists measure a range of water characteristics
to assess water quality (color, pH, temperature, etc.)
 Solutions:
 Issue and enforce more stringent regulations
 Modify industrial processes and our purchasing
decisions to rely less on these substances
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Pathogens and waterborne diseases
 Viruses, protists, and bacteria enter water supplies
through inadequately treated human waste and
animal waste from feedlots
 Fecal coliform bacteria indicate fecal contamination
 Usually are not pathogenic organisms
 Indicate that the water may hold other diseasecausing pathogens (e.g., giardiasis, typhoid,
hepatitis A)
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Pathogens and waterborne diseases
 Bacterial pollution causes more human health
problems than any other type of water pollution
 Conditions are improving, but 800 million people lack
reliable access to safe water
 Treating wastewater and personal hygiene reduce
risks
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Nutrient pollution
 Nutrient pollution from fertilizers, farms, sewage,
lawns, golf courses leads to eutrophication
 Fertilizers add phosphorus to water, which boosts
algal and aquatic plant growth
 Spreading algae cover the surface, decreasing
sunlight
 Bacteria eat dead algae, reducing dissolved oxygen
 Fish and shellfish die
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Nutrient pollution
 Areas of low oxygen can become “dead zones”
 Solutions include treating wastewater
 Reducing fertilizer application
 Using phosphate-free detergents
 Planting vegetation to increase nutrient uptake
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© 2014 Pearson Education, Inc.
Biodegradable Wastes and Sediment
 Introducing large amounts of biodegradable waste
into water decreases dissolved oxygen
 Wastewater = water affected by human activities; can
be a source of biodegradable wastes
 Sediment is the eroded material carried by rivers
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Biodegradable wastes and Sediment
 Clear-cutting, mining, clearing land for housing, and
cultivating farm fields expose soil to erosion
 It 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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© 2014 Pearson Education, Inc.
Thermal pollution
 Water that is too warm causes problems
 Warmer water holds less oxygen
 Dissolved oxygen decreases as temperature increases
 Industrial cooling heats water
 Removing streamside cover raises water temperature
 Water that is too cold also causes problems
 Water at the bottom of reservoirs behind dams is colder
 When water is released, downstream water temperatures
drop suddenly, favoring cold-loving invasive fish
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Groundwater pollution is a difficult problem
 Most pollution control efforts focus on surface water
 Groundwater is increasingly contaminated but is
hidden from view and difficult to monitor
 “Out of sight, out of mind”
 Groundwater pollution is harder to address than
surface water pollution
 Rivers flush pollutants out, but groundwater retains
contaminants for decades and longer
 It takes longer for contaminants to break down
because of lower sunlight, microbes, and dissolved
oxygen
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There are many sources of groundwater
pollution
 Some toxic chemicals occur naturally
 Aluminum, fluoride, sulfates
 Pollution from human causes is widespread
 Industrial wastes can leach through soil
 Pathogens enter through improperly designed wells
 Leaking underground storage tanks are a source of
carcinogenic pollutants from solvents and gasoline
 EPA has confirmed leaks from 510,000 tanks and
cleaned up 430,000 of them over the last 15 years
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There are many sources of groundwater
pollution
 Leaking radioactive waste also pollutes groundwater
 In 2013, officials revealed that five underground
storage tanks at the Hanford Nuclear Reservation in
Washington were leaking radioactive waste
 Billions of dollars have been spent on remediation
 Agricultural pollution comes from several sources
 Pesticides are in most of the shallow aquifers tested
 Nitrates from fertilizers have caused cancer,
miscarriages, and “blue-baby” syndrome
 Pathogens such as Escherichia coli (E. coli) can
cause illness
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© 2014 Pearson Education, Inc.
Legislative and regulatory efforts have helped
to reduce pollution
 Water pollution was worse decades ago
 Citizen activism and government response resulted in
legislation during the 1960s and 1970s
 Rivers and lakes are cleaner now
 The Federal Water Pollution Control Act (1972)
 Renamed as the Clean Water Act in 1977
 Made it illegal to discharge pollution without a permit
 Set standards for industrial wastewater
 Funded sewage treatment plants
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Legislative and regulatory efforts have helped
to reduce pollution
 Underfunded and understaffed state and federal
regulatory agencies succumbed to pressure by
industries and politicians who received money from them
 Violations of the Clean Water Act have risen to over
100,000 documented violations/year
 10% of Americans are unknowingly exposed to unsafe
drinking water
 Government action was taken to help the Great Lakes
 The water quality of the lakes has dramatically improved
 Recent Supreme Court decisions removed enforcement
powers of the EPA over many waterways
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We treat our wastewater
 Wastewater includes water that carries sewage and that
from households, manufacturing, stormwater runoff, etc.
 It is treated before being released into the environment
 Septic systems = the most popular method of
wastewater disposal in rural areas
 Underground septic tanks separate solids and oils from
wastewater
 The water drains into a drain field, where microbes
decompose the pollutants
 Solid waste is periodically pumped out and landfilled
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We treat our wastewater
 In populated areas, sewer systems carry wastewater to
treatment locations
 Primary treatment = physically removes contaminants
in settling tanks (clarifiers)
 Secondary treatment = water is stirred and aerated
 Aerobic bacteria degrade organic pollutants
 Water is treated with chlorine (and/or ultraviolet light) to
kill pathogens
 This water, called effluent, is piped into rivers or oceans
 Reclaimed water is used for lawns, irrigation, or industry
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© 2014 Pearson Education, Inc.
We treat our wastewater
 Sludge = solid material resulting from treatment of
wastewater
 Is decomposed microbially in digesters
 Resulting “biosolids” are dried then landfilled,
incinerated, or used as fertilizer on cropland
 Methane-rich gas created by decomposition can be
burned to generate electricity
 Six million dry tons of sludge are generated in the
United States each year
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Constructed wetlands can aid treatment
 Natural wetlands have long filtered and purified
water
 Human-constructed wetlands can do the same thing
 After primary treatment at a conventional facility
water is pumped into the wetland
 Microbes decompose the remaining pollutants
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Constructed wetlands can aid treatment
 Cleansed water is released into waterways or
percolates underground
 They are havens for wildlife and for human
recreation
 The United States has over 500 artificially constructed
or restored wetlands
 Released effluent has helped rebuild coastal wetlands
along the Gulf Coast
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© 2014 Pearson Education, Inc.
QUESTION: Review
The picture shows a(n)
a) braided river.
b) meandering river.
c) oxbow.
d) river delta.
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QUESTION: Review
The area of a lake that rings the edge and contains
rooted plants is called the _______ zone.
a) littoral
b) benthic
c) limnetic
d) profundal
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QUESTION: Review
An unconfined aquifer is defined as
a) an aquifer that traps porous rocks between layers of
less permeable substrate.
b) an aquifer that traps porous rocks under one layer of
less permeable substrate.
c) an aquifer with porous rocks resting on bedrock.
d) an aquifer with no upper layer.
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QUESTION: Review
Why do governments subsidize irrigation?
a) It promotes food self-sufficiency.
b) Governments have to or food could not be grown.
c) Governments want to lower water tables.
d) Governments do not subsidize irrigation.
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QUESTION: Review
Which of the following statements
about dams is NOT true?
a) They change habitat.
b) They generate electrical power.
c) They have created more farmland upstream.
d) Pollutants are trapped in reservoirs.
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QUESTION: Review
Which of the following is a point source of water
pollution?
a) A factory
b) Roads
c) Agricultural fields
d) All are point sources.
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QUESTION: Review
Which of the following types of water pollution causes
the most severe human health problems?
a) Nutrient pollution
b) Pathogens
c) Toxic chemicals
d) Sediment pollution
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QUESTION: Review
Which statement regarding using artificial wetlands to
treat wastewater is NOT correct?
a) Water first undergoes primary treatment.
b) Microbes decompose pollutants.
c) Cleansed water cannot be released into waterways.
d) They are good areas for wildlife.
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QUESTION: Viewpoints
During times of drought, conflicts erupt between
farmers (who need water for irrigation) and ecologists
(who want water left in rivers to protect wildlife). Who
should have the highest priority?
a) Farmers; they need the water for their crops.
b) Wildlife; animals will die without water.
c) Farmers should be paid subsidies to withdraw water
from other places.
d) Farmers should be paid to plant different crops that
do not require so much water.
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QUESTION: Weighing the Issues
Should cities in dry areas, such as Las Vegas, be
allowed to increase their populations, so that they will
require more water?
a) Yes; it’s un-American to limit what cities can do.
b) Yes, but make the people pay the true cost of water.
c) Yes, but only if the people are required to use
drastic conservation measures.
d) No; enough is enough, and cities in arid
environments simply cannot continue growing.
© 2014 Pearson Education, Inc.
QUESTION: Interpreting Graphs and Data
Which nation has the largest desalination capacity?
a) Japan
b) Russia
c) Saudi Arabia
d) United States
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