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=Fvkzjt3b-dU

• http://www.youtube.com/watch?v=2pXuAw1bSQo

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/view.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

Groundwaterimportant 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: recharge occurring from the side by rivers and streams

• 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

Fig. 11-5, p. 242

California

Unmet rural water needs

Highly likely conflict potential

Moderate conflict potential

Substantial conflict potential

Washington

MontanaNorthDakota

SouthDakota

Nebraska

Kansas

Oklahoma

Texas

NewMexico

Arizona

Colorado

WyomingIdaho

Oregon

Nevada

Utah

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.

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

Fig. 11-6, p. 243

Stress on the world’s major river basins, based on a comparison of the amount of water available with the amount used by humans.

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

Fig. 11-7, p. 244

Trade-Offs

Aquifer depletion fromoverpumping

Sinking of land (subsidence)from overpumping

Aquifers polluted fordecades or centuries

Saltwater intrusion intodrinking water supplies nearcoastal areas

Reduced water flows intosurface waters

Increased cost andcontamination from deeperwells

Cheaper to extract thanmost surface waters

No evaporation losses

Renewable if notoverpumped orcontaminated

Exists almost everywhere

Available year-round

Useful for drinking andirrigation

Advantages Disadvantages

Withdrawing Groundwater

Groundwater Withdrawal

• Most aquifers are renewable

• U.S. groundwater withdrawn 4X faster then it’s replenished

• Ogallala aquifer

• California’s Central Valley and agriculture

Fig. 11-8, p. 244

GroundwaterOverdrafts:

High

Moderate

Minor or none

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).

Fig. 11-9, p. 245

Waste less water Raise price of water todiscourage waste

Tax water pumped fromwells near surface waters

Set and enforce minimumstream flow levels

Divert surface water in wetyears to recharge aquifers

Solutions

Groundwater Depletion

ControlPrevention

Do not grow water-intensivecrops in dry areas

Limit number of wells

Subsidize water conservation

Science Focus: Are Deep Aquifers the Answer?

• Could have enough water to supply billions of people for centuries

• Concerns1. Nonrenewable 2. Geological and ecological impacts of

pumping them is unknown3. No treaties to govern water rights4. Costs unknown and could be high

Reservoir usefulfor recreationand fishing

Providesirrigation waterabove andbelow dam

Provides waterfor drinking

Deprivesdownstreamcropland andestuaries ofnutrient-rich silt

Risk of failureand devastatingdownstreamflooding

Disrpuptsmigration andspawning ofsome fish

Can producecheap electricity(hydropower)

Reducesdownstreamflooding

Flooded landdestroys forestsor cropland anddisplaces people

Large losses ofwater throughevaporation

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

Fig. 11-11, p. 247

Flo

w (

bil

lio

n c

ub

ic m

eter

s)

0

5

10

15

20

25

30

Year

1910 1920 1930 1940 1950 1960 1970 1980 1990 2000

Hoover Damcompleted (1935)

Glen CanyonDam completed(1963)

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

Fig. 11-12, p. 247

Tucson

North BayAqueduct

CALIFORNIANEVADA

UTAH

ARIZONA

MEXICO

South BayAqueduct

California Aqueduct

Sacramento

Fresno

Santa Barbara

Los Angeles

San Diego

Shasta LakeOroville Dam and

Reservoir

FeatherRiver

Lake Tahoe

Hoover Damand Reservoir(Lake Mead)

ColoradoRiver

SacramentoRiver

San Francisco

San Luis Damand Reservoir

San Joaquin V

alley

Salton Sea Phoenix

Los AngelesAqueduct

Colorado RiverAqueduct Central Arizona

Project

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

Stepped Art

Fig. 11-13, p. 248

Satellite photos show the sea in 1976 and in 2006.

1976 2006

Aral Sea

• http://www.youtube.com/watch?v=9HfkZXLRYu8

• http://www.youtube.com/watch?v=Z0Pi61SyVSM&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

Stepped Art

Gravity flow (efficiency 60% and 80% with surge valves)

Water usually comes from an aqueduct system or a nearby river.

Drip irrigation (efficiency 90–95%)

Above- or below-ground pipes or tubes deliver water to individual plant roots.

Center pivot (efficiency 80% with low-pressure sprinkler and 90–95% with LEPA

sprinkler)

Water usually pumped from underground and sprayed from mobile boom with sprinklers.

Fig. 11-14, p. 251

Fig. 11-16, p. 252

Fig. 11-17, p. 253

Solutions

Waste less water and subsidizewater conservation

Do not deplete aquifers

Preserve water quality

Protect forests, wetlands,mountain glaciers, watersheds,and other natural systems thatstore and release water

Get agreements among regionsand countries sharing surfacewater resources

Raise water prices

Slow population growth

Sustainable Water Use

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

Diverse ecological habitat Evapotranspiration

Trees reduce soil erosion from heavy rain and wind

Tree roots stabilize soil

Vegetation releases water slowly and reduces flooding

Forested Hillside

Agricultural land

Fig. 11-19, p. 254

Stepped Art

Tree plantation

Roads destabilize hillsides

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

Silt from erosion fills rivers and reservoirs

Rapid runoff causes flooding

After Deforestation

Evapotranspiration decreases

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

Fig. 11-20, p. 256

Reducing Flood Damage

Straighten and deepenstreams (channelization)

Build levees or floodwallsalong streams

Build dams

Preserve forests onwatersheds

Preserve and restorewetlands in floodplains

Tax development onfloodplains

Use floodplains primarilyfor recharging aquifers,sustainable agriculture andforestry

Solutions

Prevention Control

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

Decomposition

Zone

Biological

oxygen

demand

Pollutant-

tolerant fishes

(carp, gar)

Fish absent,

fungi, sludge

worms,

bacteria

(anaerobic)

8 ppm

8 ppm

Clean Zone

Clean Zone

Recovery

Zone Septic Zone

Types of

organisms

Dissolved

oxygen

(ppm)

Normal clean water

organisms(Trout, perch,

bass,mayfly, stonefly)

Normal clean water organisms

(Trout, perch, bass,

mayfly, stonefly)

Fig. 11-21, p. 258

Pollutant-

tolerant fishes

(carp, gar)

Point source

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)

Fig. 11-22, p. 259

Highly polluted river in China.

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=5smNWchqo6o

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

Cesspool,septic tank

SewerWaste lagoon

Accidentalspills

Pumpingwell

Coal stripmine runoff

Deicingroad salt

Pesticidesand fertilizers

Polluted air

Hazardous waste

injection well

Groundwaterflow

Confinedaquifer

Discharge

Leakagefrom faultycasing

Unconfined freshwater aquifer

Confined freshwater aquifer

Gasoline station

Waterpumping well

Landfill

Buried gasolineand solvent tanks

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

Fig. 11-24, p. 261

Groundwater Pollution

Pump to surface, clean,and return to aquifer(very expensive)

Inject microorganisms toclean up contamination(less expensive but stillcostly)

Pump nanoparticles ofinorganic compounds toremove pollutants (stillbeing developed)

Store harmful liquids inaboveground tanks with leakdetection and collectionsystems

Ban hazardous waste disposalin landfills and injection wells

Require leak detectors onunderground tanks

Install monitoring wells nearlandfills and undergroundtanks

Keep toxic chemicals out ofthe environment

Find substitutes for toxicchemicals

Solutions

Prevention Cleanup

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

Fig. 11-25, p. 263

The Lifestraw, designed by Torben Vestergaard Frandsenhttp://www.youtube.com/watch?feature=fvwp&NR=1&v=fZwe5B8FaoU

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/healthy-eating-recipes/stories/5-reasons-not-to-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

Healthy zoneClear, oxygen-richwaters promote growthof plankton and sea grasses,and support fish.

Oxygen-depleted zoneSedimentation and algaeovergrowth reduce sunlight,kill beneficial sea grasses, useup oxygen, and degrade habitat.

Toxic sedimentsChemicals and toxic metalscontaminate shellfish beds,kill spawning fish, andaccumulate in the tissuesof bottom feeders.

Oxygen-depletedzone

Closedbeach

Closedshellfish beds

Fig. 11-26, p. 263

Red tidesExcess nitrogen causesexplosive growth of toxicmicroscopic algae,poisoning fish andmarine mammals.

FarmsRunoff of pesticides, manure, andfertilizers adds toxins and excessnitrogen and phosphorus.

Construction sitesSediments are washed intowaterways, choking fish and plants,clouding waters, and blocking sunlight.

Urban sprawlBacteria and viruses fromsewers and septic tankscontaminate shellfish bedsand close beaches; runoff offertilizer from lawns addsnitrogen and phosphorus.

CitiesToxic metals andoil from streets andparking lots pollutewaters; sewageadds nitrogen andphosphorus.

IndustryNitrogen oxidesfrom autos andsmokestacks,toxic chemicals,and heavy metals ineffluents flow intobays and estuaries.

Pacific Garbage Patch

• http://www.youtube.com/watch?v=SQh898IcOgM&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

Stepped Art

MississippiRiver Basin

Missouri River

Ohio River

Mississippi River

Depleted oxygen

Fig. 11-A, p. 265

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.

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=8Uax5FRWnvs&feature=related

Oil Cleanup Methods

• Current methods recover no more than 15%

• Prevention is most effective method– Control runoff

– Double-hull tankers

Fig. 11-27, p. 264

Coastal Water Pollution

Improve oil-spill cleanupcapabilities

Use nanoparticles onsewage and oil spills todissolve the oil or sewage(still under development)

Require secondary treatment of coastal sewage

Use wetlands, solar-aquatic,or other methods to treatsewage

Reduce input of toxicpollutants

Separate sewage andstorm lines

Ban dumping of wastesand sewage by ships incoastal waters

Ban ocean dumping ofsludge and hazardousdredged material

Regulate coastaldevelopment, oil drilling,and oil shipping

Require double hulls foroil tankers

Prevention Cleanup

Solutions

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

Disposed of inlandfill or ocean or applied to cropland,pasture, or rangeland

Sludge drying bed

SludgeActivated sludge

Secondary

Raw sewagefrom sewers

Air pump

(kills bacteria)

To river, lake,or ocean

Sludge digester

Chlorinedisinfection tankSettling tankAeration tankSettling tankBar screen Grit chamber

Primary

Fig. 11-28, p. 268

Primary and secondary sewage treatment.

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.