UNIT 4 Water Resources and Pollution

Chapter 13 and 20

Freshwater Is an Irreplaceable Resource That We Are Managing Poorly

• Why is water so important?

• Earth as a watery world: 71%

• Freshwater availability: 0.024%

• Poorly managed resource

• Hydrologic cycle

• Water pollution

Freshwater Is an Irreplaceable Resource That We Are Managing Poorly

• Access to water is – A global health issue– An economic issue– A women’s and children’s issue– A national and global security issue

Freshwater Resources

• Surface water: rivers, lakes, wetlands, estuaries, ocean. -> recharge from runoff

• Groundwater: -> recharge from precipitation ->lateral

recharge: movement of water from rivers and streams.

Fig. 13-3, p. 316

Unconfined Aquifer Recharge Area

Precipitation Evaporation and transpiration Evaporation

Confined Recharge Area

Runoff

Flowing artesian well

Well requiring a

pump Stream

InfiltrationWater table Lake

InfiltrationUnconfined aquiferLess permeable

material such as clay

Confined aquiferConfining impermeable rock layer

Water Equity, Shortages, and Floods

Global usage of groundwater and surface water: • agriculture – 70%• Industry – 20%• Human consumption – 10%

Developing and Developed counties water usageEx: Canada – uses 20% of the world’s liquid water(0.5% of world population)

Asia- uses 30% (60% of world’s population)Water conflicts in the Middle East

Three Major River

Basins in the Middle East

core case study-pg.313

Natural Capital Degradation: Irrigation in Saudi Arabia Using an Aquifer

Water usage in US

• Western half of US = severe water shortage - arid, semi-arid; less precipitation and high evaporation; droughts-uses water withdrawals for irrigation

• Eastern half of US- high level of precipitation; reduced evaporation rate

Fig. 13-4a, p. 317

Average annual precipitation (centimeters)

41–81 More than 122

Less than 41 81–122

Surface Water and Groundwater Depletion

Groundwater Depletion• Overdraft of groundwater can cause sinkholes

or saltwater intrusion (in coastal areas)

• Ogallala aquifer: largest known aquifer– Irrigates the Great Plains– Water table lowered more than 30m– Cost of high pumping has eliminated some of

the farmers– Government subsidies to continue farming

deplete the aquifer further– Biodiversity threatened in some areas

Natural Capital Degradation: Areas of Greatest Aquifer Depletion in the U.S.

Fig. 13-10, p. 323

WYOMINGSOUTH DAKOTA

NEBRASKA

COLORADOKANSAS

OKLAHOMANEW MEXICO

Miles

0

100TEXAS

Saturated thickness of Ogallala Aquifer

Less than 61 meters (200 ft.)61–183 meters (200–600 ft.)More than 183 meters (600 ft.) (as much as 370 meters or 1,200 ft. in places)

0

160Kilometers

Groundwater Over-pumping Has Harmful Effects

• Limits future food production• Land subsidence• Sinkholes • Groundwater overdrafts near coastal

regions– Contamination of the groundwater with

saltwater• Undrinkable and unusable for irrigation

How to protect groundwater resources

• Reduce number of water-intensive crops grown in arid and semi-arid regions;

• Increase the price of water -> discourage waste;

• Implement water conservation practices in residential homes.

• Subsidize water conservation

Surface Water Usage – dams and water transfer projects

Rivers are dammed to create freshwater reservoirs + hydroelectric power

Advantages Disadvantages

No CO2 emissionProvides irrigation and drinking waterFlood controlCheap electricityReservoirs used for recreation

Displace people living behind the damDecreases nutrient-rich silt downstreamFish harvest below dam decreasesDisrupts migration patterns of some fishLoss of water by evaporationUseless after 50 yearsCH4 emissions

Examples of Major Dams

Examples of Major Dams

1. Colorado River Basin-flows from Colorado to Gulf of California- 7 states--water used for drinking (Los Angeles, San Diego, Las Vegas) and irrigation (15 % of US crops)-14 dams -> volume reduction -> not making his way to the Gulf of California or is too salty->> international disputes-> US constructed desalination plants -2 major dams: Hoover Dam (Lake Mead) and Glen Canyon Dam (Lake Powell)

Aerial View of Glen Canyon Dam Across the Colorado River and Lake Powell

The Flow of the Colorado River Measured at Its Mouth Has Dropped Sharply

Examples of Major Dams

2. Three Gorges Dam, China • World’s largest hydroelectric dam and reservoir

• 2 km long across the Yangtze River

• Benefits– Electricity-producing potential is huge– Holds back the Yangtze River floodwaters– Allows cargo-carrying ships

Three Gorges Dam, China

• Harmful effects– Displaces about 5.4 million people– Built over a seismic fault– Rotting plant and animal matter producing

CH4

• Worse than CO2 emissions

Water Transfer Projects1. The Aral Sea - Asia(Uzbekistan)-irrigation canals for cotton and rice fields-loss of volume since 1960s-increase in salinity 7X-> impacted local wetlands;- altered local climate- summers hotter and drier,

winters are colder;- Negative impact on economy – declining

commercially valuable population and decrease crop production

Fig. 13-18a, p. 331

Stepped Art

1976 2006

Ship Stranded in Desert Formed by Shrinkage of the Aral Sea

Water Transfer Projects

2. California Water transfer project- Moves water from N California to S California;- Transfers Water from Water-Rich Areas to Water-

Poor Areas• Water transferred by

– Tunnels– Aqueducts– Underground pipes

• May cause environmental problems

The California Water Project and the Central Arizona Project

Water Transfer Projects

3. China’s water transfer project• South-North Water Transfer Project• Water from three rivers to supply 0.5 billion

people• Completion in about 2050• Impact

– Economic– Health– Environmental

Water Conservation

1. Improve irrigation practices-flood irrigation=pumping large volume of water into agricultural land; H2O flows by gravity into ditches into soil. -Drip irrigation- increase crop yields from 20% to 90%-Center pivot=metal frames rolling on wheels that extend large water pipes out over the crops.

Fig. 13-20, p. 335

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

sprinkler)Drip irrigation

(efficiency 90–95%)Water usually pumped from underground and sprayed from mobile boom with sprinklers.

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

Above- or below-ground pipes or tubes deliver water to individual plant roots.Water usually comes from an aqueduct

system or a nearby river.

Other methods of irrigation water conservation

• Irrigate crops using threated urban wastewater• Irrigate at night• Don’t grow water thirsty crops in arid and semi-

arid regions;• Increase government subsidies for efficient

irrigation practices• Increase polyculture instead of monoculture;• Use soil monitor to irrigate only when needed.

Developing Countries Use Low-Tech Methods for Irrigation

• Human-powered treadle pumps

• Harvest and store rainwater

• Create a canopy over crops: reduces evaporation

• Fog-catcher nets

We Can Cut Water Waste in Industry and Homes

• Recycle water in industry

• Fix leaks in the plumbing systems

• Use water-thrifty landscaping: xeriscaping

• Use gray water

• Pay-as-you-go water use

Fig. 13-23, p. 337

SOLUTIONS

Sustainable Water Use

Waste less water and subsidize water conservation

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

Do not deplete aquifers

Slow population growth

Increasing freshwater supplies

• Desalination-reverse osmosis (microfiltration)-distillation

Some Areas Get Too Much Water from Flooding (1)

• Flood plains – Highly productive wetlands– Provide natural flood and erosion control– Maintain high water quality– Recharge groundwater

• Benefits of floodplains– Fertile soils– Nearby rivers for use and recreation– Flatlands for urbanization and farming

Some Areas Get Too Much Water from Flooding (2)

• Dangers of floodplains and floods– Deadly and destructive– Human activities worsen floods– Failing dams and water diversion– Hurricane Katrina and the Gulf Coast

• Removal of coastal wetlands

Fig. 13-25a, p. 339

Oxygen released by vegetation

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

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

Fig. 13-26, p. 340

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

Build levees or floodwalls along streams

Use floodplains primarily for recharging aquifers, sustainable agriculture and forestry

Build dams

Water Pollution Sources and Types

1. Point-source pollution – Located at specific places– Easy to identify, monitor, and regulate– ex: industry, sewage treatment plans, oil spills

from tankers;

2. Non-point pollution –Broad, diffuse areas– Difficult to identify and control– Expensive to clean up

Point Source of Polluted Water in Gargas, France

Nonpoint Sediment from Unprotected Farmland Flows into Streams

Leading Sources of Water Pollution

1. Agriculture – water runoff with sediments, excess fertilizer, pesticides; animal waste (feedlots)

2. Industrial – acids, heavy metals, fertilizers, gasoline, food processing waste, PCBs

3. Mining – sediments and chemicals like arsenic, cyanide, mercury.

Pollution in Streams, Rivers and Lakes

• Dilution – in fast moving rivers

• Biodegradation of wastes by bacteria takes time

• Oxygen sag curve

-occurs in rivers

-bacteria breaks down degradable wastes;

-bacteria depletes the dissolved oxygen in the process.

Fig. 20-5, p. 536

Point source

Pollution-tolerant

fishes (carp, gar)Types of

organisms

Normal clean water organisms

(Trout, perch, bass,

mayfly, stonefly)

Fish absent, fungi,

sludge worms,

bacteria (anaerobic)

Pollution-

tolerant fishes

(carp, gar)8 ppm

Normal clean water organisms

(Trout, perch, bass,

mayfly, stonefly)

Dissolved

oxygen (ppm)

8 ppm

Biochemical

oxygen demand Clean Zone

Recovery Zone

Septic Zone

Decomposition

ZoneClean Zone

Pollution in freshwater lakes

• Less effective at diluting pollutants than streams– Stratified layers

• Little vertical mixing

– Little of no water flow

• Eutrophication

• Oligotrophic lake– Low nutrients, clear water

• Cultural eutrophication

Remediation and Prevention of Cultural Eutrophication

• Prevent or reduce cultural eutrophication– Remove nitrates and phosphates– Diversion of lake water

• Clean up lakes– Remove excess weeds– Use herbicides and algaecides; down-side?– Pump in air

Case Study: Pollution in the Great Lakes (1)

• 1960s: Many areas with cultural eutrophication

• 1972: Canada and the United States: Great Lakes pollution control program– What was done?

• Problems still exist– Raw sewage– Nonpoint runoff of pesticides and fertilizers– Biological pollution– Atmospheric deposition of pesticides and Hg

Case Study: Pollution in the Great Lakes (2)

• 2007 State of the Great Lakes report– New pollutants found– Wetland loss and degradation; significance?– Declining of some native species– Native carnivorous fish species declining – What should be done?

Water Quality Testing Techniques

1. Physical tests-Temperature-river/stream flow velocity-turbidity – Secchi disk2. Chemical tests-pH-dissolved oxygen-Nitrates/nitrites and phosphates-hardness

Water Quality Testing Techniques

3. Biological test-biological assessment-benthic macroinvertebrates-fish species

Groundwater Pollution

• 50% of US population relies on groundwater for drinking water.

• Sources of pollution: pesticides, fertilizers, gasoline, oil from buried storage or poured directly.

• Characteristics of groundwater:-slow flow rate- 1 foot/day-> contaminants not diluted-low population of decomposing bacteria;-low concentration of dissolved oxygen• Groundwater pollutants:-arsenic: from rock and soil around the aquifer;Mining, ore processing -> cancer of skin, bladder-Nitrate Ions- from fertilizers ->cancer-MTBE (methyl tertiary butyl ether)- gasoline additive -> cancer

Fig. 20-11, p. 542

Polluted air

Hazardous waste injection wellPesticides and

fertilizers

Deicing road saltCoal strip mine

runoffBuried gasoline and solvent tanks

Pumping wellGasoline station Cesspool, septic

tank

Waste lagoon Sewer

Water pumping well

Landfill

Leakage from faulty casing

Accidental spills

Discharge

Groundwater flowUnconfined freshwater aquifer

Confined freshwater aquiferConfined aquifer

Fig. 20-12, p. 543

Leaking tank

AquiferBedrock

Water table

Groundwater flow

Gasoline leakage plume (liquid phase)

Free gasoline dissolves in groundwater (dissolved phase)

Migrating vapor phase

Contaminant plume moves with the groundwater

Water well

Ocean Pollution

• 2006: State of the Marine Environment– 80% of marine pollution originates on land– Sewage– Coastal areas most affected

• Deeper ocean waters– Dilution– Dispersion– Degradation

Ocean Pollution Is a Growing and Poorly Understood Problem

• Cruise line pollution: what is being dumped?

• U.S. coastal waters– Raw sewage

– Sewage and agricultural runoff: NO3- and PO4

3-

– Harmful algal blooms– Oxygen-depleted zones

Fig. 20-15, p. 548

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.

Red tides Excess nitrogen causes explosive growth of toxic microscopic algae, poisoning fish and marine mammals.

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.

Closed shellfish bedsClosed

beach Oxygen-depleted zone

A Red Tide

Science Focus: Oxygen Depletion in the Northern Gulf Of Mexico

• Severe cultural eutrophication

• Oxygen-depleted zone

• Overfertilized coastal area

• Preventive measures

• Will it reach a tipping point?

Fig. 20-B, p. 550

Missouri River

Mississippi River Basin

Ohio River

Mississippi River

MSLA

TXMississippi

RiverLOUISIANA

Depleted oxygen

Gulf of Mexico Gulf of Mexico

Oil Pollution in Ocean Waters

Sources• Urban and industrial runoff from land=the largest source

of ocean oil pollution;• Leaks/spills of crude oil and refined petroleum (gasoline)Impact-VOCs(volatile organic compounds) in oil immediately kills larval forms of organisms;-oil reduces buoyancy and insulation in marine mammals and birds -> causing death from loss of body heat or drowning;

Fig. 20-17, p. 551

SOLUTIONSCoastal Water Pollution

Prevention CleanupReduce input of toxic pollutants

Improve oil-spill cleanup capabilities

Separate sewage and storm lines

Use nanoparticles on sewage and oil spills to dissolve the oil or sewage (still under development)

Ban dumping of wastes and sewage by ships in coastal waters

Ban ocean dumping of sludge and hazardous dredged material Require secondary

treatment of coastal sewageRegulate coastal

development, oil drilling, and oil shipping Use wetlands, solar-

aquatic, or other methods to treat sewageRequire double hulls for oil

tankers

Preventing and Reducing Water Pollution

• Reduce erosion– Keep cropland covered with vegetation

• Reduce the amount of fertilizers

• Plant buffer zones of vegetation

• Use organic farming techniques

Preventing and Reducing Water Pollution

• Use pesticides prudently/only when needed; use integrated pest management practices

• Control runoff by protecting natural water filtration systems such as wetlands and riparian zones;

• Tougher pollution regulations for livestock operations

• Deal better with animal waste• Increase the use of alternative energy souces to

reduce mercury emissions from coal burning power plants.

Improve Sewage Treatment=reduce water pollution

• Septic tank system

• Wastewater or sewage treatment plants– Primary sewage treatment

• Physical process

– Secondary sewage treatment• Biological process

– Tertiary or advance sewage treatment • Bleaching, chlorination

Fig. 20-18, p. 553

Manhole cover (for cleanout)

Septic tankGas

Distribution boxScum

Wastewater

SludgeDrain field

(gravel or crushed stone)

Vent pipePerforated pipe

Fig. 20-19, p. 554

Sludge

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

Raw sewagefrom sewers

Sludge digester

Sludge drying bed

(kills bacteria)

To river, lake,or ocean

Activated sludge

Air pump

Primary

Grit chamberBar screen Settling tank

Secondary

Chlorinedisinfection tankAeration tank Settling tank

Stepped Art

Further Recommendation for Sewage Treatment

• Separate network of pipes for storm water• Sludge from sewage treatment must be treated

for harmful bacteria, toxic metals, and organic chemicals before used as fertilizers

• Require industries/businesses to remove toxic and hazardous waste before it reaches municipal sewage plants.

• Increase use of natural and artificial wetlands system to treat sewage;

Water Quality Legislation

• Clean Water Act-regulates point-source pollution from municipal sewage facilities, industries and wastewater treatment systems.• Water Quality Act-an amendment to Clean Water Act-encourage separation of storm water and sewer water lines.• U.S. Safe Drinking Water Act-EPA sets standards of maximum containment levels for water pollutants that have a negative health impact for humans.