Groundwater

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ENVIRONMENTAL SCIENCE 13e
CHAPTER 11:
Water Resources and
Water Pollution
Water video questions
•
•
•
•
How much fresh water on earth?
How much in rivers, lakes, and streams?
How much is used for growing food?
How much water needed to produced a pound of beef?
– A cup of coffee?
• In US how much water is used for flushing toilet?
• How much water does the average American use per
day?
• How many people today lack access to clean, safe
water supply?
• http://www.youtube.com/watch?v=Fvk
zjt3b-dU
• http://www.youtube.com/watch?v=2p
XuAw1bSQo
Core Case Study: The Colorado
River Story
•
•
•
•
1400 miles through 7 states
14 dams and reservoirs
Electricity for 30 million people
Water for 15% of U.S. crops and
livestock
• Water for desert cities
• Very little water reaches the Gulf of
California
5 major problems
• Colorado river basin includes some of driest lands in US
and Mexico
• For its size river has only modest flows
• Legal pacts signed in 1922 and 1944 allocated more
water for human use in US and Mexico than the river can
supply (even when no drought) and allocated no water
for environmental purposes)
• Since 1960 river has rarely flowed fully to Gulf of
California because of reduced water flow (dams),
increased water withdrawals, and prolonged drought
• Major Pollution
• Reference p. 242
Fig. 11-1, p. 238
Fig. 11-2, p. 238
• http://earthobservatory.nasa.gov/IOTD/vie
w.php?id=1288
11-1 Will We Have Enough
Usable Water?
• Concept 11-1A We are using available
freshwater unsustainably by wasting it,
polluting it, and charging too little for this
irreplaceable natural resource.
• Concept 11-1B One of every six people
does not have sufficient access to clean
water, and this situation will almost
certainly get worse.
Importance and Availability of
Water (1)
• Earth as a watery world – saltwater covers about
71% of the earth’s surface
• Water is one of our most poorly managed
resources
• Water access is a global health issue
– 3900 children under 5 die every day from
waterborne disease
• Water is an economic issue because it is vital for
reducing poverty and producing food and energy
Importance and Availability of
Water (2)
• National and global security issue because of
increasing tensions within and between nations
over access to limited water resources
• Environmental issue because excessive
withdrawal of water from rivers and aquifers
results in dropping water tables, lower river
flows, shrinking lakes, and losses of wetlands
• Freshwater availability – 0.024%
– Groundwater
– Lakes
– Rivers
– Streams
Fig. 11-3, p. 240
Groundwater
important terms to know
• Groundwater:
water that sinks into the soil and is stored
in slowly flowing and slowly renewed underground reservoirs
called aquifers
• Zone of saturation: area where all available pores in
soil and rock are filled by water
• Water table: upper surface of the zone of saturation
• Aquifers: porous, water saturated layers of sand, gravel, or
bedrock that can yield an economically significant amount of
water
• Natural recharge:
natural replenishment of an aquifer by
precipitation that percolates downward through soil and rock
• Lateral recharge:
and streams
recharge occurring from the side by rivers
• http://www.eoearth.org/article/Aquifer
Surface Water
•
•
•
•
Surface runoff
Watershed (drainage) basin
Reliable runoff – 1/3 of total
Runoff use (worldwide)
– Domestic – 10%
– Agriculture – 70%
– Industrial – 20%
Case Study: Freshwater Resources
in the United States (1)
• Uneven distribution
• Contamination by agriculture and
industry
• Eastern U.S.
• Western U.S.
• Groundwater withdrawal: ~50% of
total use
• Drought: prolonged period in which precipitation is at
least 70% lower and evaporation is higher than normal in an
area that is normally not dry
Case Study: Freshwater Resources
in the United States (2)
• Arid and semiarid West:
– 85% of water to irrigate thirsty crops
– Water hot spots
– Southwest: “permanent drying” by 2050
• Water tables dropping
• 36 states to face water shortages by
2013 (drought, rising temps, pop growth, urban sprawl, and
excessive use and waste of water)
Fig. 11-4, p. 241
Water hotspots in 17 Western states that, by 2025, could face intense conflicts over
scarce water needed for urban growth, irrigation, recreation, and wildlife. Some analysts
suggest that this is a map of places not to live in the forseeable future.
Washington
Montana
Oregon
Idaho
Wyoming
North
Dakota
South
Dakota
Nebraska
Nevada
Utah
Colorado
California
Kansas
Oklahoma
Arizona
New
Mexico
Texas
Highly likely conflict potential
Substantial conflict potential
Moderate conflict potential
Unmet rural water needs
Fig. 11-5, p. 242
Freshwater Shortages
• Causes of water scarcity
– Dry climate
– Drought
– Too many people
– Wasting water
• 2050: 60 countries will face water stress
• 1 of 7 people – no regular access to clean
water
• Potential international conflicts over water
Stress on the world’s major river basins, based on a comparison of the amount of water
available with the amount used by humans.
Fig. 11-6, p. 243
11-2 How Can We Increase
Water Supplies?
• Concept 11-2A Groundwater used to
supply cities and grow food is being
pumped from aquifers in some areas
faster than it is renewed by precipitation.
• Concept 11-2B Using dams, reservoirs,
and transport systems to provide water to
arid regions has increased water supplies
in some areas, but has disrupted
ecosystems and displaced people.
11-2 How Can We Increase
Water Supplies?
• Concept 11-2C We can convert salty
ocean water to freshwater, but the
cost is high, and the resulting salty
brine must be disposed of without
harming aquatic or terrestrial
ecosystems.
Increasing Freshwater Supplies
•
•
•
•
•
Withdrawing groundwater
Dams and reservoirs
Transporting surface water
Desalination
Water conservation
Trade-Offs
Withdrawing Groundwater
Advantages
Disadvantages
Useful for drinking and
irrigation
Aquifer depletion from
overpumping
Available year-round
Sinking of land (subsidence)
from overpumping
Exists almost everywhere
Aquifers polluted for
decades or centuries
Renewable if not
overpumped or
contaminated
Saltwater intrusion into
drinking water supplies near
coastal areas
No evaporation losses
Reduced water flows into
surface waters
Cheaper to extract than
most surface waters
Increased cost and
contamination from deeper
wells
Fig. 11-7, p. 244
Groundwater Withdrawal
• Most aquifers are renewable
• U.S. groundwater withdrawn 4X faster
then it’s replenished
• Ogallala aquifer
• California’s Central Valley and
agriculture
Areas of greatest aquifer depletion from groundwater overdraft in the continental
United States. Aquifer depletion in also high in Hawaii and Puerto Rico (not shown).
Groundwater
Overdrafts:
High
Moderate
Minor or none
Fig. 11-8, p. 244
Solutions
Groundwater Depletion
Prevention
Control
Waste less water
Raise price of water to
discourage waste
Subsidize water conservation
Tax water pumped from
wells near surface waters
Limit number of wells
Set and enforce minimum
stream flow levels
Do not grow water-intensive
crops in dry areas
Divert surface water in wet
years to recharge aquifers
Fig. 11-9, p. 245
Science Focus: Are Deep
Aquifers the Answer?
•
•
Could have enough water to supply
billions of people for centuries
Concerns
1. Nonrenewable
2. Geological and ecological impacts of
pumping them is unknown
3. No treaties to govern water rights
4. Costs unknown and could be high
Provides
irrigation water
above and
below dam
Flooded land
destroys forests
or cropland and
displaces peopl
Large losses o
water through
evaporation
Provides water
for drinking
Reservoir useful
for recreation
and fishing
Can produce
cheap electricity
(hydropower)
Reduces
downstream
flooding
Deprives
downstream
cropland and
estuaries of
nutrient-rich si
Risk of failure
and devastatin
downstream
flooding
Disrpupts
migration and
spawning of
some fish
Fig. 11-10, p. 246
Overtapped Colorado River Basin
• Only small amount reaches Gulf of
California
– Threatened species
• Climate change will likely decrease flows
• Less water in Southwest
– Political and legal battles
• Silt behind dams not reaching delta and will
eventually fill up reservoirs
Flow (billion cubic meters)
30
Hoover Dam
completed (1935)
25
20
15
Glen Canyon
Dam completed
(1963)
10
5
0
1910
1920
1930
1940 1950
1960
1970 1980
1990 2000
Year
Fig. 11-11, p. 247
California Water Project
• Dams, pumps, aqueducts
• Southern California would otherwise
be desert
• Climate change will reduce water
availability in California
• People in southern California may
have to move
• Groundwater already being depleted
Sacramento
River
CALIFORNIA
NEVADA
Shasta Lake
Oroville Dam and
Reservoir
UTAH
Feather
Lake Tahoe
River
North Bay
Aqueduct
San Francisco
Sacramento
South Bay
Aqueduct
San Luis Dam
and Reservoir
Hoover Dam
and Reservoir
(Lake Mead)
Fresno
Colorado
River
Los Angeles
Aqueduct
California Aqueduct
Santa Barbara
Colorado River
Aqueduct
Los Angeles
San Diego
Salton Sea
ARIZONA
Central Arizona
Project
Phoenix
Tucson
MEXICO
Fig. 11-12, p. 247
Aral Sea Disaster (1)
• Large-scale water transfers in dry
central Asia
• Water loss and salinity increase
• Wetland destruction and wildlife
• Fish extinctions hurt fishing industry
Aral Sea Disaster (2)
•
•
•
•
Wind-blown salt
Water pollution
Climatic changes
Restoration efforts
1976
2006
Satellite photos show the sea in 1976 and in 2006.
Stepped Art
Fig. 11-13, p. 248
Aral Sea
• http://www.youtube.com/watch?v=9HfkZX
LRYu8
• http://www.youtube.com/watch?v=Z0Pi61
SyVSM&feature=fvwrel
Removing Salt from Seawater
•
•
•
•
Desalination
Distillation
Reverse osmosis
13,000 plants in 125 countries
Major Problems with
Desalination
• High cost
• Death of marine organisms
• Large quantity of brine wastes
11-3 How Can We Use Water
More Sustainably?
• Concept 11-3 We can use water
more sustainably by cutting water
waste, raising water prices, slowing
population growth, and protecting
aquifers, forests, and other
ecosystems that store and
release water.
Reducing Water Waste (1)
• Benefits of water conservation
• Worldwide – 65-70% loss
– Evaporation, leaks
– Can be reduced to 15%
• Increase the cost of water use
– End subsidies for wasteful water use
– Provide subsidies for efficient water use
Reducing Water Waste (2)
• Improve irrigation efficiency
– Center pivot
– Low-pressure sprinkler
– Precision sprinklers
– Drip irrigation
• Use less in homes and businesses
Center pivot
Drip irrigation
(efficiency 90–95%)
(efficiency 80% with low-pressure
sprinkler and 90–95% with LEPA
sprinkler)
Above- or below-ground
(efficiency 60% and 80% with surge valves) pipes or tubes deliver water
to individual plant roots.
Water usually comes from an
aqueduct system or a nearby river.
Gravity flow
Water usually pumped from
underground and sprayed
from mobile boom with
sprinklers.
Stepped Art
Fig. 11-14, p. 251
Fig. 11-16, p. 252
Solutions
Sustainable Water Use
Waste less water and subsidize
water conservation
Do not deplete aquifers
Preserve water quality
Protect forests, wetlands,
mountain glaciers, watersheds,
and other natural systems that
store and release water
Get agreements among regions
and countries sharing surface
water resources
Raise water prices
Slow population growth
Fig. 11-17, p. 253
Fig. 11-18, p. 253
11-4 How Can We Reduce the
Threat of Flooding?
• Concept 11-4 We can lessen the
threat of flooding by protecting more
wetlands and natural vegetation in
watersheds and by not building in
areas subject to frequent flooding.
Benefits of Floodplains
• Highly productive wetlands
• Provide natural flood and erosion
control
• Maintain high water quality
• Recharge groundwater
• Fertile soils
• Nearby rivers for use and recreation
• Flatlands for urbanization and farming
Floods
•
•
•
•
•
•
Deposit rich soils on floodplains
Deadly and destructive
Human activities worsen floods
Failing dams and water diversion
Hurricane Katrina and the Gulf Coast
Climate change will increase coastal
flooding
Tree plantation
Diverse
ecological
habitat
Evapotranspiration
Trees reduce soil
erosion from heavy
rain and wind
Agricultural
land
Tree roots
stabilize soil
Roads
destabilize
hillsides
Evapotranspiration decreases
Overgrazing accelerates soil
erosion by water and wind
Winds remove
fragile topsoil
Agricultural
land is flooded
and silted up
Gullies and
landslides
Heavy rain erodes topsoil
Vegetation releases water
slowly and reduces flooding
Forested Hillside
Silt from erosion fills
rivers and reservoirs
Rapid runoff
causes flooding
After Deforestation
Stepped Art
Fig. 11-19, p. 254
Case Study: Floodplains of
Bangladesh
• Dense population on coastal
floodplain
• Moderate floods maintain fertile soil
• Increased frequency of large floods
• Development in the Himalayan
foothills
• Destruction of coastal wetlands
Solutions
Reducing Flood Damage
Prevention
Control
Preserve forests on
watersheds
Straighten and deepen
streams (channelization)
Preserve and restore
wetlands in floodplains
Tax development on
floodplains
Use floodplains primarily
for recharging aquifers,
sustainable agriculture and
forestry
Build levees or floodwalls
along streams
Build dams
Fig. 11-20, p. 256
11-5 How Can We Deal with
Water Pollution?
• Concept 11-5A Streams can cleanse
themselves of many pollutants if we do not
overload them or reduce their flows.
• Concept 11-5B Reducing water pollution
requires preventing it, working with nature
in treating sewage, cutting resource use
and waste, reducing poverty, and slowing
population growth.
Water Pollution Sources
• Point sources
– Discharge at specific locations
– Easier to identify, monitor, regulate
• Nonpoint sources
– Broad, diffuse areas
– Runoff of chemicals and sediment
– Agriculture
– Control is difficult and expensive
Table 11-1, p. 257
Stream Pollution
•
•
•
•
Natural recovery processes
Oxygen sag curve
Effective regulations in the U.S.
Problems in developing countries
Dilution and decay of degradable, oxygen-demanding wastes (or heated water) in a stream, showing the oxygen
sag curve (blue) and the curve of oxygen demand (red)
Point source
Fig. 11-21, p. 258
Highly polluted river in China.
Fig. 11-22, p. 259
Individuals Matter: John Beal p. 258
• Restored Hamm Creek in Washington State
• Persuaded companies to stop polluting the
creek, hauled out many truckloads of trash,
began 15 yr project of planting thousands of
trees along streams banks, also restored natural
waterfalls and salmon spawning beds
• Outstanding example of Stewardship based on
the idea that “All sustainability is local”
• http://www.youtube.com/watch?v=5smNWchqo6
o
Lake Pollution
• Dilution less effective than with streams
– Stratification
– Low flow
• Lakes are more vulnerable than
streams
• Eutrophication – natural aging process
• Oligotrophic
Cultural Eutrophication
• Nitrate- and phosphate-containing effluents
• Dense colonies of plants, algae,
cyanobacteria
• Can lead to die-off of fish and other
animals
• Prevent by limiting phosphate and nitrate
use
• Lakes can be cleaned, and can recover
Groundwater Pollution (1)
•
•
•
•
•
Pollution sources
Slow flow, dilution, dispersion
Low dissolved oxygen
Fewer bacteria
Cooler temperatures
Groundwater Pollution (2)
• Long time scale for natural cleansing
– Degradable wastes – organic matter
– Slowly degradable wastes – DDT
– Nondegradable wastes – lead, arsenic
Polluted air
Hazardous
waste
injection
well
Pesticides
and fertilizers
Coal strip
mine runoff
Deicing
road salt
Pumping
well
Waste lagoon
Gasoline
station
Water
pumping well
Buried gasoline
and solvent
tanks
Cesspool,
septic tank
Sewer
Landfill
Leakage
from faulty
casing
Accidental
spills
Discharge
Confined
aquifer
Groundwater
flow
Fig. 11-23, p. 260
Extent of Groundwater Pollution
•
•
•
•
•
Global scale – not much known
Monitoring is very expensive
Underground fuel tank leakage
Arsenic
Protecting groundwater – prevention
is best and least expensive
Solutions
Groundwater Pollution
Prevention
Cleanup
Find substitutes for toxic
chemicals
Pump to surface, clean,
and return to aquifer
(very expensive)
Keep toxic chemicals out of
the environment
Install monitoring wells near
landfills and underground
tanks
Require leak detectors on
underground tanks
Inject microorganisms to
clean up contamination
(less expensive but still
costly)
Ban hazardous waste disposal
in landfills and injection wells
Store harmful liquids in
aboveground tanks with leak
detection and collection
systems
Pump nanoparticles of
inorganic compounds to
remove pollutants (still
being developed)
Fig. 11-24, p. 261
Purifying Drinking Water
• Developed countries
– Reservoir storage
– Purification plant
• Developing countries without purification plants
– Clear plastic bottle in sun, with black side
– http://www.grilink.org/sunwater.htm
– LifeStraw
The Lifestraw, designed by Torben Vestergaard Frandsen
http://www.youtube.com/watch?feature=fvwp&NR=1&v=fZwe5B8FaoU
Fig. 11-25, p. 263
Science Focus: Is Bottled Water
the Answer?
• 500-1000 times the cost of tap water
– Americans spent $15 billion in 2007
• About 1/4 is ordinary tap water
• About 40% of bottled water
contaminated
• Water testing standards lower than
for tap water
• Environment: energy use, pollution
Bottled Water
• http://www.mnn.com/food/healthyeating-recipes/stories/5-reasons-notto-drink-bottled-water#
Ocean Pollution
• Coastal areas – highly productive
ecosystems
– Occupied by 40% of population
– Coastal populations will double by 2050
– About 80% marine pollution originates on land
• Ocean dumping controversies
• Algal blooms
• Oxygen-depleted zones
Industry
Nitrogen oxides
from autos and
smokestacks,
toxic chemicals,
and heavy metals in
effluents flow into
bays and estuaries.
Cities
Toxic metals and
oil from streets and
parking lots pollute
waters; sewage
adds nitrogen and
phosphorus.
Urban sprawl
Bacteria and viruses from
sewers and septic tanks
contaminate shellfish beds
and close beaches; runoff of
fertilizer from lawns adds
nitrogen and phosphorus.
Construction sites
Sediments are washed into
waterways, choking fish and plants,
clouding waters, and blocking sunlight.
Farms
Runoff of pesticides, manure, and
fertilizers adds toxins and excess
nitrogen and phosphorus.
Closed
shellfish beds
Closed
beach
Red tides
Excess nitrogen causes
explosive growth of toxic
microscopic algae,
poisoning fish and
marine mammals.
Oxygen-depleted
zone
Toxic sediments
Chemicals and toxic metals
contaminate shellfish beds,
kill spawning fish, and
accumulate in the tissues
of bottom feeders.
Oxygen-depleted zone
Sedimentation and algae
overgrowth reduce sunlight,
kill beneficial sea grasses, use
up oxygen, and degrade habitat.
Healthy zone
Clear, oxygen-rich
waters promote growth
of plankton and sea
grasses,and support fish.
Fig. 11-26, p. 263
Pacific Garbage Patch
• http://www.youtube.com/watch?v=SQ
h898IcOgM&feature=related
Science Focus: Oxygen Depletion
in the Northern Gulf of Mexico
• Mouth of Mississippi River in spring
and summer
• Suffocates fish, crab, shrimp
• Cultural eutrophication
• Caused by fertilizer use in Mississippi
watershed
• Need less and more intelligent use of
fertilizers
• Need better flood control
A large zone of oxygen-depleted water forms each year during the spring and summer in the Gulf of
Mexico as a result of oxygen-depleting algal blooms. Evidence indicates that it is created mostly by
huge inputs of nitrate plant nutrients from farms, cities, factories, and sewage treatment plants in the
vast Mississippi River basin.
Missouri River
Mississippi
River Basin
Ohio River
Mississippi River
Depleted oxygen
Stepped Art
Fig. 11-A, p. 265
Case Study: Ocean Pollution
from Oil
• Crude and refined petroleum
• Tanker accidents – Exxon Valdez
• Urban and industrial runoff is largest
source
Effects of Oil Pollution on
Ocean Ecosystems
• Volatile organic hydrocarbons
– Kill larvae
– Destroy natural insulation and buoyancy
of birds and mammals
• Heavy oil
– Sinks and kills bottom organisms
– Coral reefs die
Gulf of Mexico Oil Spill
• http://www.youtube.com/watch?v=8U
ax5FRWnvs&feature=related
Oil Cleanup Methods
• Current methods recover no more
than 15%
• Prevention is most effective method
– Control runoff
– Double-hull tankers
Solutions
Coastal Water Pollution
Prevention
Cleanup
Reduce input of toxic
pollutants
Improve oil-spill cleanup
capabilities
Separate sewage and
storm lines
Ban dumping of wastes
and sewage by ships in
coastal waters
Ban ocean dumping of
sludge and hazardous
dredged material
Regulate coastal
development, oil drilling,
and oil shipping
Require double hulls for
oil tankers
Use nanoparticles on
sewage and oil spills to
dissolve the oil or sewage
(still under development)
Require secondary
treatment of coastal
sewage
Use wetlands, solar-aquatic,
or other methods to treat
sewage
Fig. 11-27, p. 264
Preventing Nonpoint Source
Pollution (1)
• Mostly agricultural waste
• Use vegetation to reduce soil erosion
• Reduce fertilizer use
Preventing Nonpoint Source
Pollution (2)
• Use plant buffer zones around fields
and animal feedlots
• Keep feedlots away from slopes,
surface water, and flood zones
• Integrated pest management
• Organic farming methods
Laws for Reducing Point Source
Pollution
• Clean Water Act
• Water Quality Act
• Discharge trading controversies
– Cap-and-trade of pollutants
Case Study: Reducing Water Pollution
from Point Sources in the U.S.
• Impressive achievements since 1972 law
• Bad news – 2006 survey
– 45% of lakes and 40% of streams too polluted
for fishing and swimming
– Runoff polluting 7 of 10 rivers
– Fish caught in 1/4 of waterways unsafe to eat
• Gasoline storage tanks: tens of thousands
leaking
Sewage Treatment Systems
• Rural and suburban areas – septic
tanks
• Urban areas – wastewater treatment
plants
– Primary sewage treatment – physical
process
– Secondary sewage treatment –
biological process
– Chlorination – bleaching and disinfection
Primary and secondary sewage treatment.
Primary
Bar screen Grit chamber
Secondary
Settling tank
Aeration tank
Settling tank
Sludge
Raw sewage
from sewers
Activated sludge
Chlorine
disinfection tank
To river,
lake,
or ocean
(kills bacteria)
Air pump
Sludge digester
Disposed of in
landfill or ocean or
applied to cropland,
pasture, or rangeland
Sludge drying bed
Fig. 11-28, p. 268
Improving Sewage Treatment
• Systems that exclude hazardous and
toxic chemicals
• Require businesses to remove
harmful chemicals before sewage
sent to treatment plant
• Reduce or eliminate use of toxic
chemicals
• Composting toilet systems
• Wetland-based sewage treatment
Science Focus: Treating
Sewage by Working with Nature
• Living machines
• Tanks with increasingly complex
organisms
• Artificially created wetlands
• Scientific principles of sustainability
Fig. 11-29, p. 269
Fig. 11-30, p. 269
Three Big Ideas from This
Chapter - #1
One of the world’s major environmental
problems is the growing shortages of
freshwater in parts of the world.
Three Big Ideas from This
Chapter - #2
We can use water more sustainably by
cutting water waste, raising water
prices, slowing population growth,
and protecting aquifers, forests, and
other ecosystems that store and
release water.
Three Big Ideas from This
Chapter - #3
Reducing water pollution requires
preventing it, working with nature in
treating sewage, cutting resource use
and waste, reducing poverty, and
slowing population growth.
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