Water Resources · 2020. 1. 2. · •Las Vegas, Los Angeles, San Diego –Responsible for...

© Cengage Learning 2015

LIVING IN THE ENVIRONMENT, 18eG. TYLER MILLER • SCOTT E. SPOOLMAN


13Water Resources

2

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


• 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

Case Study: The Colorado River Story

The Colorado River Basin

Fig. 13-1, p. 318


• 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

13-1 Will We Have Enough Usable Water?


• 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


• 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

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.

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 accessiblesource 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.

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.

12

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.

Water used for irrigation that evaporates.


• 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


• 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 StatesWashington

Oregon

MontanaNorth Dakota

IdahoSouth DakotaWyoming

NevadaNebraska

UtahColorado Kansas

California Oklahoma

ArizonaNew Mexico

Texas

Highly likely conflict potential

Substantial conflict potential

Moderate conflict potential

Unmet rural water needs


• 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.

Freshwater Shortages Will Grow


• 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


• 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

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


• 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

Case Study: Overpumping the Ogallala


• 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.

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 driveways


• 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

Deep Aquifers Might Be Tapped


• 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)

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.

© Cengage Learning 2015Fig. 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 siltReservoir 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

© Cengage Learning 2015Fig. 13-17b, p. 330

Powerlines

Reservoir

Dam

IntakePowerhouse

Turbine

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.


• 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

How Dams Can Kill an Estuary


• 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

How Dams Can Kill an Estuary (cont’d.)


• 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

Fig. 13-19a, p. 332


• 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

Case Study: The Aral Sea Disaster

Fig. 13-20, p. 333


• 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.

More than 15,000 plants in 125 countries


• 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.)

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

Legal disputes over ownership of cloud water.


• 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?

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

Use less in homes and businesses

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.


• Flood irrigation

–Wasteful

• Center pivot, low pressure sprinkler

• Low-energy; precision application

sprinklers

• Drip or trickle irrigation, microirrigation

–Costly

–Less water waste

We Can Improve Efficiency in Irrigation

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. 13-22, p. 337

© Cengage Learning 2015Fig. 13-25, p. 338


• 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

Solutions: Reducing Water Waste

Fig. 13-27, p. 340


• 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

• Also apply strategies at a personal level

© Cengage Learning 2015Fig. 13-28, p. 341


• 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?

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

Removal of coastal wetlands


• 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.)

Diverse

ecological

habitatEvapotranspiration

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

hillsidesOvergrazing accelerates soil

erosion by water and wind

Winds remove

fragile topsoil

Agricultural

land is flooded

and silted upGullies and

landslides

Heavy rain erodes topsoil

Silt from erosion fills

rivers and reservoirs

Rapid runoff

causes flooding

After Deforestation

Evapotranspiration decreases

Fig. 13-29, p. 343

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 wetlandsIn 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.


• Rely more on nature’s systems

–Wetlands

–Natural vegetation in watersheds

• Rely less on engineering devices

–Dams

–Levees

–Channelized streams

We Can Reduce Flood Risks

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 and forestry Build dams


• 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

Three Big Ideas


• 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

Tying It All Together: The Colorado River

and Sustainability

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