TYLER MILLER SCOTT E. SPOOLMAN

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LIVING IN THE ENVIRONMENT, 18e

G. TYLER MILLER • SCOTT E. SPOOLMAN

13

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2 “When the well is dry, we learn the worth of water.” - Benjamin Franklin

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• The Colorado River

– Flows 2,300 km through seven U.S. states – Includes 14 dams and reservoirs

– Water supplied mostly from snowmelt of the Rocky Mountains

– Supplies water and electricity for about 30 million people • Las Vegas, Los Angeles, San Diego

– Responsible for irrigation of crops that help feed America • Issues

– Very little water is reaching the Gulf of California – The southwest has recently been recent droughts

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The Colorado River Basin

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• We are using available freshwater

unsustainably by wasting it, polluting

it, and underpricing what is an

irreplaceable natural resource

• Freshwater supplies are not evenly

distributed, and one of every six

people on the planet does not have

adequate access to clean water

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• Freshwater availability – 0.024%

– Groundwater, lakes, rivers, and streams • Hydrologic cycle

– Movement of water in the seas, land, and air – Driven by solar energy and gravity

– Distributed unevenly

• Humans can alter the hydrologic cycle

– Withdrawing water, polluting, climate change

Most of the Earth’s Freshwater Is Not

Available to Us

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• Water covers 71% of the earth’s

surface

• Poorly managed resource

–Global health issue

–Economic issue

–National and global security issue

–Environmental issue

Freshwater Is an Irreplaceable Resource

That We Are Managing Poorly

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Case Study: Water Conflicts in the Middle East

•Most of the water in the middle east comes from three shared river basins: the Nile, Jordan, and

Tigris-Euphrates.

•Most likely in the future, these water short countries are going to face

conflicts over access to water resources.

•The water from the Nile River

is used by three countries:

Ethiopia, Sudan, and Egypt. Since Ethiopia’s population is rapidly increasing, they plan to divert more water from the

Nile, along with Sudan.

•The Jordan basin is the most water short region and has competition between Jordan, Syria, Palestine, and Israel.

Syria plans to build dams and withdraw more water from the Jordan River, decreasing the downstream water supply for Jordan and Israel; where Israel threatens to destroy the dam.

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 The majority of Earth’s water is in the oceans,

and too salty for drinking or irrigation.

 _{About 3% is}_freshwater_, water that is relatively free from salts.

 _{The largest accessible}

source of freshwater is

groundwater beneath the surface that resides in pores in soil and

rock.

 _{Only about 1% is}

surface water, such as lakes, rivers, and

ponds.

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What is Groundwater?

 Ground water is one of the most important sources of water on earth it contains more water than any other

source of fresh water. It’s the precipitation that

infiltrates and percolates through the voids in soil and rock.

• _{Zone of aeration-} _{Close to the surface; pores of soil} contain a mixture or air and water

• Zone of saturation- lower layers of soil where spaces between particles are completely filled with water.

• _{Water table}_{- located at the top of the zone of}

saturation; top of zone levels rises in wet weather and falls in dry.

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 Aquifers are sponge like

formations of rock and sand that contain groundwater.

 _{The uppermost border of the} aquifer is called the water table.  _{Water enters aquifers through}

areas of soil called recharge zones.

 Aquifers that are trapped

between impermeable layers of rock or clay are called confined aquifers.

 _{Wells that enter unconfined}

aquifers are called water table or

groundwater wells.

 Wells that enter confined aquifers are called artesian wells.

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_{Streams and rivers are fed by runoff from surrounding}

areas and areas where groundwater flows to the surface.

_{The area of land drained by a river system is that river’s}

watershed.

_{Lakes and ponds} _{are standing bodies of surface water fed}

from rivers, streams, and runoff from precipitation.

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 _Water_withdrawal _{measures the total amount diverted or} withdrawn from a source.

 _{The water may be returned, such as with coolant water in power}

plants.

 _Water_consumption_{measures water permanently removed from a} source.

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• 2/3 of the surface runoff – lost by seasonal floods • Reliable runoff

– Remaining 1/3 on which we can rely • Worldwide averages

– Domestic: 10% – Agriculture: 70% – Industrial use: 20%

• Agriculture counts for 92% of humanity’s water footprint • Virtual water

– Not consumed; used to produce food and other products

We Are Using Increasing Amounts of the

World’s Reliable Runoff

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• More than enough

renewable freshwater, unevenly distributed and polluted

• What are the effects of the following?

– Floods – Pollution – Drought

• U.S. Geological Survey projection, 2007

– Water hotspots

Case Study:

Freshwater Resources

in the United States Washington

Oregon

Montana North _Dakota

Idaho_Wyoming South _Dakota

Nevada Nebraska Utah

Colorado Kansas

California _Oklahoma

Arizona New _Mexico

Texas

Highly likely conflict potential Substantial conflict potential

Moderate conflict potential Unmet rural water needs

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• There are four causes of water scarcity:

1) Drought – prolonged period of low

precip., high evapor. rate

2) Dry climate

3) Desiccation- drying of exposed soil

due to deforestation/overgrazing

4) water stress – increasing #’s of people

relying on limited runoff

• U.N. 2010 study

– By 2025, three billion people will likely lack access to clean water

• Water stress occurs when the demand for water exceeds the supply. This is likely to occur in:

– Naturally arid ecosystems. – Heavily populated countries. – Areas with intensive,

highly-irrigated agriculture.

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• Accurate information about water

shortages

• Approaches:

–Withdrawing groundwater

–Building dams and reservoirs

–Transporting surface water

–Converting saltwater to

freshwater

There Are Ways to Increase Freshwater

Supplies

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• Groundwater used to supply cities and grow food is being pumped from aquifers in some areas faster than it is renewed by precipitation

13-2 Is Groundwater a Sustainable

Resource?

Groundwater is Being Withdrawn Faster Than It Is Replenished in Some Areas

• Most aquifers are renewable

– Unless water is contaminated or removed

• Aquifers provide drinking water for half the world

• Water tables are falling in many parts of the world, primarily from crop irrigation

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Fig. 13-11, p. 326

Trade-Offs

Withdrawing Groundwater

Advantages Disadvantages

Useful for drinking and irrigation

Aquifer depletion from overpumping Exists almost everywhere Sinking of land (subsidence) from overpumping Renewable if not overpumped or contaminated

Pollution of aquifers lasts decades or centuries

Some deeper wells are nonrenewable

Cheaper to extract than most surface waters

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• Ogallala aquifer – largest known aquifer – Irrigates the Great Plains

– Very slow recharge – Water table dropping

• Water pumped 10-40 times faster than recharge

– Government subsidies to continue farming deplete the aquifer further

– Biodiversity threatened in some areas

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• Limits future food

production

• Bigger gap between the rich

and the poor

• Land subsidence – Mexico City

– San Joaquin Valley in California

• Groundwater overdrafts

near coastal regions

– Contamination of

groundwater with saltwater

Overpumping Aquifers Has Several Harmful Effects

Excessive groundwater

consumption can also lead to subsidence, a

compression and sinking of the zone of saturation.

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 _A_{cone of depression}_{is a lowering of the water table around a}

groundwater well due to excessive consumption.

 Saltwater intrusion place when salt water moves into freshwater aquifers due to excessive consumption and a lowering of the water table.

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Fig. 13-16, p. 329

Solutions

Groundwater Depletion

Prevention Control

Use water more efficiently

Raise price of water to discourage waste

Tax water pumped from wells near surface waters Subsidize water

conservation

Build rain gardens in urban areas

Limit number of wells

Stop growing water-intensive crops in dry areas

Use permeable paving material on streets, sidewalks, and

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• May contain enough water to provide for billions of people for centuries

• Major concerns – Nonrenewable

– Little is known about the geological and

ecological impacts of pumping deep aquifers

– Some flow beneath more than one country – Costs of tapping are unknown and could

be high

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• Large dam-and-reservoir systems have greatly

expanded water supplies in some areas, but have also disrupted ecosystems and displaced people

13-3 Can Surface Water Resources Be

Expanded?

Use of Large Dams Provides Benefits and Creates Problems

• Main goal of a dam and reservoir system – Capture and store runoff

– Release runoff as needed to control: • Floods

• Generate electricity

• Supply irrigation water • Recreation (reservoirs)

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Using Dams and Reservoirs to Supply

More Water

Advantages: Disadvantages:  _{Cheap, constant} electricity  _{Reduces downstream} flooding

 Storing water year-round for irrigation and cities.

 Reservoirs can provide recreational activities

 Displaces people

 Disrupts aquatic

ecosystems (i.e. fish migrations/ runoff)

 _{Flooding can destroy}

surrounding forests and croplands

 Large loss of water through evaporation

 Reservoirs behind dams collect increased levels of silt and slow water flow.

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© Cengage Learning 2015 Fig. 13-17a, p. 330 Provides irrigation water above and below dam Flooded land destroys forests or cropland and displaces people Large losses of water through evaporation Provides water for drinking Deprives downstream cropland and estuaries of nutrient-rich silt Reservoir useful

for recreation and fishing Risk of failure and devastating downstream ﬂooding Can produce cheap electricity (hydropower) Reduces down-stream flooding of

cities and farms _{Disrupts migration}

and spawning of some fish

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China’s Three Gorges Dam

Good News:

•Provide electricity of 18 coal

burning plants and reduce China’s dependence on coal

•Larger ships can enter interior = less in transportation costs

•Reduce greenhouse gas emissions

•Improve air quality

Bad News:

• 1.9 M people being relocated

•Build over a seismic fault

•Flooding potential •High costs

the world’s largest dam and reservoir.

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• Only small amount of Colorado River

water reaches Gulf of California

–Threatens aquatic species in river

and species that live in the estuary

• Current rate of river withdrawal is not

sustainable

• Much water used for agriculture that is

inefficient with water use

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• Reservoirs

– Leak water into ground

below

– Lose much water

through evaporation

– Fill up with silt load of

river, depriving delta

– Could eventually lose

ability to store water and create electricity

• States must conserve water, control population, and slow urban development

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• Transferring water from one place to another has greatly increased water supplies in some areas, but has also disrupted ecosystems

13-4 Can Water Transfers Be Used to

Expand Water Supplies?

Water Transfers Can Be Inefficient and Environmentally Harmful

• China

– South-North Water Diversion Project • Divert six trillion gallons of water • California central valley

– Aqueducts

• Water loss through evaporation • Ecosystem degradation

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• Large-scale water transfers in dry central Asia have led to: – Wetland destruction

• Desertification

– Greatly increased salinity

– Fish extinctions and decline of fishing – Wind-blown salt

• Depositing on glaciers in the Himalayas – Altered local climate

• Hot dry summers; cold winters • Restoration efforts

– Cooperation of neighboring countries – More efficient irrigation

– Dike construction to raise lake level

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• 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

13-5 Is Desalination a Useful Way to

Expand Water Supplies?

Removing Salt from Seawater Is Costly and Has Harmful Effects

Desalination is the removal of salt from seawater.

Distillation involves the heating of water, collecting the steam, then disposing of the salt waste.

Reverse osmosis uses pressure to pass water through a physical filter.

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• Problems

–High cost and energy footprint

–Keeps down algal growth and

kills many marine organisms

–Large quantity of brine wastes

Removing Salt from Seawater Is Costly

and Has Harmful Effects (cont’d.)

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Seeding Clouds and Towing Icebergs and Big

Baggies

 Seeding clouds with tiny particles of chemicals to increase rainfall, or towing icebergs or huge bags filled with freshwater to dry coastal areas, probably will not provide significant amounts of fresh water in the future.

 Bad News:

 Cloud seeding does not work very well in very dry areas where rain is needed most, because there are few clouds.

 There is no compelling scientific evidence that it works.

 Introduces large amounts of chemicals to soil and water

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• We can use freshwater more

sustainably by:

–Cutting water waste

–Raising water prices

–Slowing population growth

–Protecting aquifers, forests, and

other ecosystems that store and

release freshwater

13-6 How Can We Use Freshwater More

Sustainably?

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Reducing Water Waste

 _{We waste about two-thirds of the water we use but using}

water more efficiently could reduce wastage to about 15%.

 _{Worldwide – 65-70% freshwater loss}

 _{Evaporation, leaks}

 _{Education of benefits of water conservation}

 _{According to water resource experts the main cause of}

water waste is that we charge too little for

water-Regulating water prices, decrease government subsidies for supply water and increase subsidies for water waste

reduction

 _{Improve irrigation efficiency}  _{Improve collection efficiency}

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 _{Water conservation}_{in homes can be achieved through the use of} low-flow faucets, showerheads, washing machines, and dual-flush toilets.

 _Graywater _{is relatively-clean water from the sink, shower, laundry,} and dishwasher that may be used for non-drinking purposes, such as toilet flushing, car washing, and garden irrigation.

 Xeriscaping is landscaping with plants that require little or no irrigation.

 _{Reduces water use in dry}

regions from people irrigating grass lawns.

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 _{Water conservation focuses on} agriculture, as it is the biggest source of water consumption.  _{Water conservation methods in}

agriculture include:

 _{Lining irrigation canals to}

prevent leaks.

 _{Contour plowing and}

terracing to minimize water runoff.

 _{Switching to high-efficiency}

irrigation methods, like drip irrigation.

 Eliminating water-intensive crops, such as rice and

almonds, from arid regions.

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Almond farmer monitoring a drip irrigation line passing through her orchard. Image from the Almond Board of California.

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• Flood irrigation

–Wasteful

• Center pivot, low pressure sprinkler

• Low-energy; precision application

sprinklers

• Drip or trickle irrigation, microirrigation

–Costly

–Less water waste

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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.

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• Human-powered treadle pumps

• Harvest and store rainwater

• Use tensiometers

–Measure soil moisture

• Use polyculture to create canopy

vegetation

–Reduces evaporation

Poor Farmers Conserve Water Using

Low-Tech Methods

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Solutions: Reducing Water Waste

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• Use human sewage to create nutrient-rich sludge to apply to croplands

• Use waterless composting toilets

We Can Use Less Water to Remove

Wastes

We Can Each Help Out in Using Water More Sustainably

• Protect water supplies

• Apply strategies at local, regional,

national, and international levels

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• We can lessen the threat of

flooding by:

–Protecting more wetlands and

natural vegetation in watersheds

–Not building in areas subject to

frequent flooding

13-7 How Can We Reduce the Threat

of Flooding?

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Benefits of Floodplains

 Highly productive wetlands

 Provide natural flood and erosion control

 Maintain high water quality

 Recharge groundwater

 Fertile soils

 Nearby rivers for transporation use and recreation

 Flatlands for urbanization and farming

Dangers of Floodplains and Floods

 Deadly and destructive

 Human activities worsen floods

 Failing dams and water diversion

 Hurricane Katrina and the Gulf Coast

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• Human activities make floods worse

–Levees can break or be overtopped

–Paving and development increase runoff

–Removal of water-absorbing vegetation

–Draining wetlands and building on them

–Rising sea levels from global warming

means more coastal flooding

Some Areas Get Too Much Water from

Flooding (cont’d.)

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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

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Case Study: Floodplains of Bangladesh

 Dense population

 Located on coastal floodplain

 Moderate floods maintain fertile soil

 Increase frequency of large floods

 Development in the Himalayan foothills

 Destruction of coastal wetlands

In struggle to survive, the poor in Bangladesh have cleared many of the coastal mangrove forests for fuel

woods, farming, and aquaculture

ponds for raising shrimp. This has led to more severe flooding.

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• Rely more on nature’s systems

–Wetlands

–Natural vegetation in watersheds

• Rely less on engineering devices

–Dams

–Levees

–Channelized streams

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Fig. 13-30, p. 344

Solutions

Reducing Flood Damage

Preserve forests on watersheds Straighten and deepen streams (channelization) Prevention Control

Preserve and restore wetlands in floodplains Tax development on floodplains Build levees or floodwalls along streams Increase use of floodplains for sustainable agriculture

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• One of the major global environmental problems is the growing shortage of freshwater in many parts of the

world

• We can expand water supplies in water-short areas

– Most important to reduce overall water use and use water much more efficiently

• We can use water more sustainably – Cut water losses

– Raise water prices

– Protect aquifers, forests, and other ecosystems that store and release water

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• Large dams and diversion projects help with: – Electricity, food, drinking water, and flood

control

• Large dams degrade aquatic natural capital • We need to:

– Rely on solar energy for desalination – Recycle more water