lecture outlines€¦ · china’s three gorges dam • the dam, on the yangtze river, is the...

© 2011 Pearson Education, Inc.

Lecture Outlines

Chapter 15

Environment:The Science behind the

Stories

4th Edition

Withgott/Brennan


This lecture will help you understand:

• Water’s importance to people and ecosystems

• Water’s distribution• Use and alteration of

freshwater systems• Problems of water supply

and solutions• Problems of water quality

and solutions• How wastewater is treated


Gambling with water in the Colorado River basin• 7 states share the Colorado river• Droughts and overuse are

threatening supplies• Las Vegas, Nevada, needs more

water than it is allotted• Other states will let Las Vegas

drill for underground water• Drilling threatens the area’s

ecology and people• This issue will end up in Nevada’s

Supreme Court


The Colorado River• The Colorado River originates

in the Rocky Mountains- Draining into the Gulf of

California• Its waters chiseled the Grand

Canyon- But it has been reduced to a

mere trickle• Dams provide flood control,

recreation, and hydroelectric power- 30 million people use the

water


Freshwater systems

• Water may seem abundant, but drinkable water is rare• Freshwater = relatively pure, with few dissolved

salts- Most is tied up in glaciers, ice caps, and aquifers


Water is renewed and recycled

• As water is cycled it redistributes heat, erodes mountains, builds river deltas, maintains ecosystems and organisms- It also shapes civilizations and political conflicts

• Surface water = on Earth’s surface- 1% of freshwater

• 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• Watershed (drainage basin) = the area of land drained

by a river system (river and its tributaries)


Water is renewed and recycled as it moves through the hydrologic cycle


Water Cycle Scramble


Rivers and streams wind through landscapes

• Rivers shape the landscape• Braided river = an interconnected series of watercourses

that run through steep slopes• Meandering river = rivers in flatter areas

- Water rounding a bend erodes soil from the outer bank- Sediment is deposited on the inside of the bend- Rivers become exaggerated oxbows


Rivers shape the landscape

• Oxbows = areas where river bends become exaggerated

• Oxbow lake = erosion cuts off and isolates the oxbow into a U-shaped water body


A river may shift course over time

• Floodplain = areas nearest to the river’s course that are flooded periodically- Frequent deposition of silt makes floodplain soils

fertile- Good areas for agriculture

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

• Rivers and streams hosts diverse ecological communities- Algae, insects, fish, amphibians, birds, etc.


Lakes and ponds are ecologically diverse

• Lakes and ponds = 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 = extends along the bottom of the water

body - Home to many invertebrates

• Limnetic zone = open portion of the lake or pond where sunlight allows photosynthesis

• Profundal zone = water that sunlight does not reach - Supports fewer animals because there is less oxygen


A typical lake


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

• The largest lakes are known as inland seas- Great Lakes, The Caspian Sea


Wetlands include marshes, swamps, bogs, and seasonal pools• Wetlands = the soil is saturated

with shallow standing water• Freshwater marshes = shallow

water- Plants 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

Species in vernal pools are adapted to seasonal drying


Wetlands are valuable

• Wetlands are extremely valuable for wildlife- They slow runoff, reduce flooding, recharge aquifers,

and filter pollutants• People have drained wetlands, mostly for agriculture

- Southern Canada and the U.S. have lost over half of their wetlands

• In 2006 the Supreme Court told the Army Corps of Engineers it must create guidelines to determine when wetlands are valuable enough to protect by law


Groundwater plays a key role• Groundwater = water beneath the surface held in pores

in soil or rock- 20% of the Earth’s freshwater supply

• Aquifers = porous, sponge-like formations of rock, sand, or gravel that hold water - Zone of aeration = pore spaces are 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


A typical aquifer


There are two categories of aquifers

• Confined (artesian) aquifer = water-bearing, porous rocks are trapped between less permeable substrate (clay) layers - Is under great pressure

• Unconfined aquifer = no upper layer to confine it- Readily recharged by surface water

• Groundwater’s average age is 1,400 years- It may be tens of thousands of years old

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


The Ogallala Aquifer

• The world’s largest known aquifer

• Underlies the Great Plains of the U.S.

Its water has allowed farmers to create the most bountiful grain-producing region in the world


Water is unequally distributed across Earth• Water is unevenly distributed in space and time

- Different areas possess different amounts of water- People erect dams to store water

Many densely populated areas are water-poor and face serious water shortages


Climate change may bring shortages

• Climate change will cause - Altered precipitation

patterns- Melting glaciers- Early season runoff- Intensified droughts- Flooding

Lake Mead is already hurting from drought


How we use water

• We have achieved impressive engineering accomplishments to harness fresh water- 60% of the world’s largest 227 rivers have been

strongly or moderately affected - Dams, dikes, and diversions

• Consumption of water in most of the world is unsustainable- We are depleting many sources of surface water and

groundwater


Water supplies houses, agriculture, and industry• Proportions of these three types of use vary dramatically

among nations- Arid countries use water for agriculture- Developed countries use water for industry

• Consumptive use = water is removed from an aquifer or surface water body and is not returned - Irrigation = the provision of water to crops

• Nonconsumptive use = does not remove, or only temporarily removes, water- Electricity generation at hydroelectric dams


Why does agriculture use so much water?

• Rapid population growth requires more food and clothes• The Green Revolution uses irrigation

- We use 70% more irrigation water than 50 years ago• Irrigation can 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


Governments subsidize irrigation

• Irrigation subsidies promote food self-sufficiency- But irrigation uses up huge amounts of groundwater

for little gain• Water in the Colorado River Valley is diverted for

cotton and other crops grown in the desert

Farmers in California’s Imperial Valley pay only 1 penny for 220 gallons of water


We divert surface water for our needs

• People divert water to farm fields, homes, and cities

The once mighty Colorado River has been extensively diverted and used


Water-poor regions take water from others

• 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, L.A. diverted streams that fed Lake Mono

- Lake levels fell, salt concentrations doubled• Las Vegas wants to import water from sparsely

populated eastern Nevada- An ecologically sensitive area


We 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• Dikes and levees (long, raised mounds of earth) along

the banks of rivers hold water in channels- Levees make floods worse by forcing water to stay

in channels and then overflow• Dams prevent flooding and change a river’s nature

- Releasing water periodically simulates flooding


Levees increase flooding

• A major levee along the Mississippi River failed after Hurricane Katrina, allowing parts of New Orleans to be flooded


We have erected thousands of dams

• Dam = any obstruction placed in a river or stream to block the flow of water 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• Dams are great engineering feats

- Many stand hundreds of feet tall


A typical dam


China’s Three Gorges Dam

• The dam, on the Yangtze River, is the largest in the world- 186 m (610 feet) high, 2.3

km (1.4 mi) wide- Its reservoir stretches for

616 km (385 mi)- Provides flood control,

passage for boats, and electricity


Drawbacks of the Three Gorges Dam

• 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• Tidal marshes at the Yangtze’s

mouth are eroding• Pollutants will be trapped

It will cost $5 billion to build sewage treatment plants to treat water


Some dams are being removed

• Some people feel that the costs of dams outweigh their benefits- They are pushing to dismantle dams

• 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 U.S.

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


We are depleting surface water

• In many places, we are withdrawing water at unsustainable rates- Reduced flow drastically changes the river’s ecology,

plant community, and destroys fish and invertebrates

The Colorado River often does not reach the Gulf of California


The Aral Sea• 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 from the lake

bed is blown into the air• Cotton cannot save the region’s

economy


Can the Aral Sea be saved?

People have begun saving the northern part of the Aral Sea


Irrigation wastes water• 15–35% of water withdrawals for irrigation are

unsustainable

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


The world is losing wetlands

• Wetlands are being lost as we divert and withdraw water- Channelize rivers, build dams, etc.

• As wetlands disappear, we lose ecosystem services- Filtering pollutants, wildlife habitat, flood control, etc.

• Many are trying to protect and restore them• The Ramsar Convention on Wetlands of International

Importance (1971)- Seeks the conservation and wise use of wetlands in the

context of sustainable development- 1,900 sites covering 185 million ha are protected


We are depleting groundwater

• Groundwater is easily depleted - Aquifers recharge slowly- Used by one-third of all people

• As aquifers are mined, water tables drop- Salt water intrudes in coastal areas

• Sinkholes = areas where ground gives way unexpectedly- Aquifers can’t recharge

• Wetlands dry up


Can we quench our thirst for bottled water?

• Groundwater is being withdrawn for bottled water- An average American drinks 29 gallons/year

• 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- Bottles are not recycled- Corporations move in, deplete water, and move away


Bottled water is popular but problematic

• Bottled water is popular but it has several problems

Energy costs of bottled water are 1,000–2,000 times greater than those of tap water


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 neighboring countries

• Many nations have cooperated with neighbors to resolve disputes- They sign water-sharing treaties


Solutions can address supply or demand

• We can either increase supply or reduce demand• Increasing supply through intensive extraction

- Diversions increase supply in one area but decrease it elsewhere

• 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


Desalinization “makes” more 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• Desalinization facilities operate mostly in the arid Middle

East- It is expensive, requires fossil fuels, kills aquatic life,

and produces salty waste


The world’s largest reverse osmosis plant

• Near Yuma, Arizona• Intended to remove salt

from irrigation runoff• Too expensive to operate

and closed after 8 months- Engineers are trying to

re-open it in a cost-effective way


Agricultural demand can be reduced

• Line irrigation canals• 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• Selective breeding and genetic modification to produce

crops that require less water• Eat less meat


Residential demand can be reduced

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

• Rainwater harvesting = capturing rain from roofs

• Gray water = wastewater from showers and sinks

• Water lawns at night• We can save hundreds or

thousands of gallons/dayXeriscaping uses plants adapted to arid conditions


Industrial demand can be reduced

• Shift to processes that use less water- Wastewater recycling

• Use excess surface water runoff to recharge aquifers• Patch leaky pipes and retrofit homes with efficient

plumbing• Audit industries• Promote conservation/education


Market-based approaches to conservation

• 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 - There is little incentive to provide access to the poor

• Decentralization of water control may conserve water- Shift control to the local level


Freshwater pollution and its control

• Water for human consumption and other organisms needs to be:- Disease-free- Nontoxic

• Half of the world’s major rivers are seriously depleted and polluted- They poison surrounding ecosystems- Threatening the health and livelihood of people

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


Point and nonpoint sources of pollution

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

• Point sources = discrete locations of water pollution- Factories, sewer pipes- Addressed by the U.S. Clean Water Act

• Nonpoint sources = pollution arises from multiple inputs over larger areas (farms, city streets, neighborhoods)- The major source of U.S. water pollution


Freshwater pollution sources


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

• Solutions include treating wastewater- Reducing fertilizer application- Using phosphate-free detergents- Planting vegetation to increase nutrient uptake


Eutrophication is a natural process, but…

• Human activities dramatically increase the rate at which it occurs


Pathogens and waterborne diseases

• Enter water supplies through inadequately treated human waste and animal waste from feedlots

• Fecal coliform bacteria indicate fecal contamination- They are not pathogenic organisms- But the water may also hold other disease-causing

pathogens (e.g., giardiasis, typhoid, hepatitis A)• Bacterial pollution causes more human health problems

than any other type of water pollution- Conditions are improving- 86% of people now have safe water


Pathogens cause human health problems

• 1 billion are still without safe water• 2.6 billion have inadequate sewer or sanitary facilities

- Mostly rural Asians and Africans• Health impacts kill 5 million people per year• Solutions:

- Disinfect drinking water- Treat sewage- Public education to encourage personal hygiene- Government enforcement of regulations protecting

food


Toxic chemicals

• Pesticides, petroleum products, synthetic chemicals- Arsenic, lead, mercury, acid rain, acid drainage from

mines• Effects include poisoned animals and plants, altered

aquatic ecosystems, and decreased human health• Solutions:

- Issue and enforce more stringent regulations of industry

- Modify industrial processes- Modify our purchasing decisions


Sediment pollution

• Sediment in rivers can impair aquatic ecosystems• 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


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, killing aquatic organisms


Indicators of water quality

• Scientists measure properties of water to characterize its quality- Biological indicators: presence of fecal coliform

bacteria, disease-causing organisms, algae, etc.- Chemical indicators: nutrient concentrations, pH,

taste, odor, hardness, dissolved oxygen- Physical indicators: color, temperature, turbidity


Groundwater pollution is a difficult problem

• Groundwater is increasingly contaminated- But is hidden from view and difficult to monitor- “Out of sight, out of mind”

• Groundwater pollution is hard to address- It retains contaminants for decades and longer- It takes longer for contaminants to break down because

of lower sunlight, microbes, and dissolved oxygen


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

- Leaking underground storage and septic tanks

So far, the EPA has cleaned up 388,000 leaking tanks


Agriculture and industry pollute groundwater• 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 like Escherichia coli (E. coli)

• Manufacturing industries and military sites have been heavy polluters- By-products seep into water from miles around- Radioactive wastes will contaminate water for 750,000

years


It is best to prevent pollution

• It is far better to prevent pollution than use “end-of-pipe” treatment and cleanup

• Other options are not as good:- Removing just one herbicide from water in the U.S.

Midwest costs $400 million/year- Pumping, treating, and re-injecting it takes too long

• Consumers can purchase sustainably made products- Become involved in local “riverwatch” projects- Urge government to pursue policies to fight pollution


Legislative efforts reduce pollution

• Water pollution was worse decades ago- Citizen activism and government response resulted in

legislation during the 1960s and 1970s- The situation is much better now

• The Federal Water Pollution Control Act (1972)- Renamed the Clean Water Act in 1977- It is illegal to discharge pollution without a permit- Sets standards for industrial wastewater- Funded sewage treatment plants


Enforcement of water quality is decreasing

• Underfunded and understaffed state and federal regulatory agencies were pressured by industries and politicians

• 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- The new EPA administrator has promised to improve

• Citizens pushed politicians to improve the Great Lakes- The water quality of the lakes has dramatically

improved


We treat our drinking water

• Technology and government regulation have improved our pollution control- Treated drinking water is widespread and successful in

developed nations• Before water reaches the user, it is chemically treated,

filtered, and disinfected• The EPA sets standards for over 90 drinking water

contaminants- Local governments and private water suppliers must

meet these standards


We treat our wastewater

• Wastewater = water people have used in some way- Household, 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


Municipal sewer systems

• 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 treated with chlorine (and/or ultraviolet light) is

piped into rivers or the ocean• Reclaimed water is used for lawns, irrigation, or industry


A typical wastewater treatment facility

• Sludge = solid material resulting from treatment- Is decomposed

microbially- Then landfilled,

incinerated, or used as fertilizer on cropland

• Methane-rich gas created by decomposition can be burned to generate electricity


Artificial wetlands clean wastewater• After primary treatment at a

conventional facility- Water is pumped into the wetland- Microbes decompose the

remaining pollutants• Cleansed water is released into

waterways - Or percolates underground

• They are havens for wildlife and areas for human recreation

The U.S. has over 500 artificially constructed or restored wetlands


Conclusion

• Obtaining future supplies of freshwater requires citizen action, legislation and regulation, technology, economic incentives, and education

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

• Water pollution is already harming health, economies, and societies of both rich and poor nations

• Better regulation has improved water quality in the U.S. and other developed nations


QUESTION: Review

The picture shows a(n):

a) Braided riverb) Meandering riverc) Oxbowd) River delta


QUESTION: Review

The area of a lake that rings the edge and contains rooted plants is called the _______ zone.

a) Littoralb) Benthicc) Limneticd) Profundal


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 bedrockd) An aquifer with no upper layer


QUESTION: ReviewWhy 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.


QUESTION: ReviewWhich of the following statements is NOT true about dams?

a) They change habitat.b) They generate electrical power.c) They have created more farmland upstream.d) Pollutants are trapped in reservoirs.


QUESTION: ReviewWhich of the following is a point source of water pollution?

a) A factoryb) Roadsc) Agricultural fieldsd) All are point sources


QUESTION: ReviewWhich of the following type of water pollution causes the most severe human health problems?

a) Nutrient pollutionb) Pathogensc) Toxic chemicalsd) Sediment pollution


QUESTION: Review

Which statement is NOT correct regarding using artificial wetlands to treat wastewater?

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.


QUESTION: Interpreting Graphs and DataIn this figure of a wastewater treatment facility, what is the first step in treatment?

a) Physical screening to remove large debris

b) Aeration in basinsc) Secondary

clarificationd) Piping the treated

water into a river


QUESTION: ViewpointsDuring 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.


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.

lecture outlines€¦ · china’s three gorges dam • the dam, on the yangtze river, is the...

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