Water Resources

Chapter 13

Core Case Study: Water Conflicts in the Middle East: A Preview of the Future

Water shortages in the Middle East: hydrological poverty

Nile River

Jordan Basin

Tigris and Euphrates Rivers

Peacefully solving the problems

Three Major River Basins in the Middle East

13-1 Will We Have Enough Usable Water?

Concept 13-1A We are using available freshwater unsustainably by wasting it, polluting it, and charging too little for this irreplaceable natural resource.

Concept 13-1B One of every six people does not have sufficient access to clean water, and this situation will almost certainly get worse.

Freshwater Is an Irreplaceable Resource That We Are Managing Poorly (1)

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 (2)

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

Girl Carrying Well Water over Dried Out Earth during a Severe Drought in India

Most of the Earth’s Freshwater Is Not Available to Us

Hydrologic cycle • Movement of water in the seas, land, and air• Driven by solar energy and gravity

People divided into• Water haves• Water have-nots

We Get Freshwater from Groundwater and Surface Water (1)

Ground water

Zone of saturation

Water table

Aquifers• Natural recharge • Lateral recharge

We Get Freshwater from Groundwater and Surface Water (2)

Surface Water• Surface runoff• Watershed (drainage) basin• Reliable runoff• 1/3 of total

Natural Capital: Groundwater System: Unconfined and Confined Aquifer

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

We Use a Large and Growing Portion of the World’s Reliable Runoff

2/3 of the surface runoff: lost by seasonal floods

1/3 runoff usable • Domestic: 10%• Agriculture: 70%• Industrial use: 20%

Fred Pearce, author of When the Rivers Run Dry

Case Study: Freshwater Resources in the United States

More than enough renewable freshwater, unevenly distributed

Effect of• Floods• Pollution• Drought

2007: U.S. Geological Survey projection • Water hotspots

Average Annual Precipitation and Major Rivers, Water-Deficit Regions in U.S.

Fig. 13-4a, p. 317

Fig. 13-4a, p. 317

Average annual precipitation (centimeters)

41–81 More than 122

Less than 41 81–122

Fig. 13-4b, p. 317

Fig. 13-4b, p. 317

Shortage

Acute shortage

Adequate supply

Metropolitan regions with population greater than 1 million

Water Hotspots in 17 Western U.S. States

Fig. 13-5, p. 318

Substantial conflict potential

Highly likely conflict potential

Unmet rural water needs

Moderate conflict potential

Washington

Oregon

MontanaNorth Dakota

Idaho South DakotaWyoming

Nevada NebraskaUtah

ColoradoKansas

CaliforniaOklahoma

New Mexico

Texas

Arizona

Water Shortages Will Grow (1)

Dry climate

Drought

Too many people using a normal supply of water

Water Shortages Will Grow (2)

Wasteful use of water

China and urbanization

Hydrological poverty

Natural Capital Degradation: Stress on the World’s Major River Basins

Fig. 13-6, p. 319

Europe Asia

North America

Africa

South America Australia

Stress

High None

Long-Term Severe Drought Is Increasing

Causes• Extended period of below-normal rainfall• Diminished groundwater

Harmful environmental effects• Dries out soils• Reduces stream flows• Decreases tree growth and biomass• Lowers net primary productivity and crop yields• Shift in biomes

In Water-Short Areas Farmers and Cities Compete for Water Resources

2007: National Academy of Science study• Increased corn production in the U.S. to make

ethanol as an alternative fuel• Decreasing water supplies• Aquifer depletion• Increase in pollution of streams and aquifers

Who Should Own and Manage Freshwater Resources? (1)

Most water resources• Owned by governments• Managed as publicly owned resources

Veolia and Suez: French companies• Buy and manage water resources • Successful outcomes in many areas

Who Should Own and Manage Freshwater Resources? (2)

Bechtel Corporation• Poor water management in Bolivia

A subsidiary of Bechtel Corporation• Poor water management in Ecuador

Potential problems with full privatization of water resources• Financial incentive to sell water; not conserve it• Poor will still be left out

13-2 Is Extracting Groundwater the Answer?

Concept 13-2 Groundwater that is used to supply cities and grow food is being pumped from aquifers in some areas faster than it is renewed by precipitation.

Water Tables Fall When Groundwater Is Withdrawn Faster Than It Is Replenished

India, China, and the United States• Three largest grain producers• Overpumping aquifers for irrigation of crops

India and China• Small farmers drilling tubewells • Effect on water table

Saudi Arabia• Aquifer depletion and irrigation

Trade-Offs: Withdrawing Groundwater, Advantages and Disadvantages

Fig. 13-7, p. 321

TRADE-OFFS

Withdrawing Groundwater

Advantages DisadvantagesUseful for drinking and irrigation

Aquifer depletion from overpumping

Available year-roundSinking 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

Natural Capital Degradation: Irrigation in Saudi Arabia Using an Aquifer

Case Study: Aquifer Depletion in the United States

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

California Central Valley: serious water depletion

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

Fig. 13-9, p. 322

Groundwater Overdrafts:

Moderate

Minor or none

High

Natural Capital Degradation: The Ogallala is the World’s Largest Known Aquifer

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 Overpumping Has Other Harmful Effects (1)

Limits future food production

Bigger gap between the rich and the poor

Land subsidence• Mexico City

Sinkholes

Groundwater Overpumping Has Other Harmful Effects (2)

Groundwater overdrafts near coastal regions• Contamination of the groundwater with saltwater• Undrinkable and unusable for irrigation

Solutions: Groundwater Depletion, Using Water More Sustainably

Fig. 13-11, p. 324

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

Science Focus: Are Deep Aquifers the Answer?

Locate the deep aquifers; determine if they contain freshwater or saline water

Major concerns• Geological and ecological impact of pumping

water from them• Flow beneath more than one country• Who has rights to it?

Active Figure: Threats to aquifers

13-3 Is Building More Dams the Answer?

Concept 13-3 Building dam and reservoir systems has greatly increased water supplies in some areas, but it has disrupted ecosystems and displaced people.

Large Dams and Reservoirs Have Advantages and Disadvantages (1)

Main goals of a dam and reservoir system• Capture and store runoff

• Release runoff as needed to control:• Floods• Generate electricity• Supply irrigation water• Recreation (reservoirs)

Large Dams and Reservoirs Have Advantages and Disadvantages (2)

Advantages• Increase the reliable runoff available• Reduce flooding• Grow crops in arid regions

Large Dams and Reservoirs Have Advantages and Disadvantages (3)

Disadvantages• Displaces people• Flooded regions• Impaired ecological services of rivers• Loss of plant and animal species• Fill up with sediment within 50 years

Advantages and Disadvantages of Large Dams and Reservoirs

The Ataturk Dam Project in Eastern Turkey

Some Rivers Are Running Dry and Some Lakes Are Shrinking

Dams disrupt the hydrologic cycle Major rivers running dry part of the year• Colorado and Rio Grande, U.S.• Yangtze and Yellow, China• Indus, India• Danube, Europe• Nile River-Lake Victoria, Egypt

Lake Chad Africa: disappearing

Case Study: The Colorado River Basin— An Overtapped Resource (1)

2,300 km through 7 U.S. states

14 Dams and reservoirs

Located in a desert area within the rain shadow of the Rocky Mountains

Water supplied mostly from snowmelt of the Rocky Mountains

Case Study: The Colorado River Basin— An Overtapped Resource (2)

Supplies water and electricity for more than 25 million people

Irrigation of crops

Recreation

Case Study: The Colorado River Basin— An Overtapped Resource (3)

Four Major problems• Colorado River basin has very dry lands• Modest flow of water for its size• Legal pacts allocated more water for human use

than it can supply• Amount of water flowing to the mouth of the river

has dropped

Case Study: The Colorado River Basin— An Overtapped Resource (4)

What will happen if some of the reservoirs empty out?• Economic and ecological catastrophe• Political and legal battles over water

The Colorado River Basin

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

Fig. 13-16, p. 328

35

30 Hoover Dam completed (1935)

25

20

15 Glen Canyon Dam completed (1963)

10

Flo

w (

bil

lio

n c

ub

ic m

eter

s)

5

0

1910 1920 1930 1940 1950 1960 1970 1980 1990 2000

Year

Case Study: China’s Three Gorges Dam (1)

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

Case Study: China’s Three Gorges Dam (2)

Harmful effects• Displaces about 5.4 million people• Built over a seismic fault• Significance?

• Rotting plant and animal matter producing CH4

• Worse than CO2 emissions

• Will the Yangtze River become a sewer?

13-4 Is Transferring Water from One Place to Another the Answer?

Concept 13-4 Transferring water from one place to another has greatly increased water supplies in some areas, but it has also disrupted ecosystems.

CA, U.S., Transfers Water from Water-Rich Areas to Water-Poor Areas

Water transferred by• Tunnels• Aqueducts• Underground pipes

May cause environmental problems

California Water Project

The California Water Project and the Central Arizona Project

Fig. 13-17, p. 330

CALIFORNIAShasta Lake NEVADA

Sacramento River

UTAH

North Bay Aqueduct

Feather River

Lake Tahoe

San FranciscoSacramento

South Bay Aqueduct

Hoover Dam and Reservoir (Lake Mead)

Los Angeles Aqueduct

Colorado River

California AqueductColorado River

Aqueduct Central Arizona Project

ARIZONA

Fresno

Santa Barbara

Los Angeles

San DiegoSalton Sea

Phoenix

Tucson

MEXICO

San Luis Dam and Reservoir

San Joaquin V

alley

Oroville Dam and Reservoir

Case Study: The Aral Sea Disaster (1)

Large-scale water transfers in dry central Asia

Salinity

Wetland destruction and wildlife

Fish extinctions and fishing

Case Study: The Aral Sea Disaster (2)

Wind-blown salt

Water pollution

Climatic changes

Restoration efforts

Natural Capital Degradation: The Aral Sea, Shrinking Freshwater Lake

Fig. 13-18a, p. 331

Stepped Art

1976 2006

Ship Stranded in Desert Formed by Shrinkage of the Aral Sea

China Plans a Massive Transfer of Water

South-North Water Transfer Project Water from three rivers to supply 0.5 billion

people Completion in about 2050 Impact• Economic• Health• Environmental

13-5 Is Converting Salty Seawater to Freshwater the Answer?

Concept 13-5 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.

Removing Salt from Seawater Seems Promising but Is Costly (1)

Desalination• Distillation• Reverse osmosis, microfiltration

15,000 plants in 125 countries• Saudi Arabia: highest number

Removing Salt from Seawater Seems Promising but Is Costly (2)

Problems• High cost and energy footprint• Keeps down algal growth and kills many marine

organisms• Large quantity of brine wastes

Future economics

Science Focus: The Search for Improved Desalination Technology

Desalination on offshore ships• Solar or wind energy

Better membranes

Better disposal options for the brine waste

Reduce water needs, conserve water

13-6 How Can We Use Water More Sustainably?

Concept 13-6 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 Has Many Benefits (1)

Water conservation• Improves irrigation efficiency• Improves collection efficiency• Uses less in homes and businesses

Reducing Water Waste Has Many Benefits (2)

Worldwide: 65–70% loss • Evaporation, leaks, etc.

Water prices: low cost to user

Government subsidies: more needed?

We Can Cut Water Waste in Irrigation

Flood irrigation• Wasteful

Center pivot, low pressure sprinkler

Low-energy, precision application sprinklers

Drip or trickle irrigation, microirrigation• Costly; less water waste

Major Irrigation Systems

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.

Fig. 13-20, p. 335

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.

Solutions: Reducing Irrigation Water Waste

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

Solutions: Reducing Water Waste

We Can Use Less Water to Remove Wastes

Can we mimic how nature deals with waste?

Waterless composting toilets

We Need to Use Water More Sustainably

“The frog does not drink up the pond in which it lives”

Blue revolution

Solutions: Sustainable 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

What Can You Do? Water Use and Waste

13-7 How Can We Reduce the Threat of Flooding?

Concept 13-7 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.

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

Natural Capital Degradation: Hillside Before and After Deforestation

Fig. 13-25a, p. 339

Oxygen released by vegetation

Diverse ecological habitat

Evapotranspiration

Trees reduce soil erosion from heavy rain and wind

Agricultural land

Tree roots stabilize soil

Vegetation releases water slowly and reduces flooding

Forested Hillside

Fig. 13-25b, p. 339

Tree plantation

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

Silt from erosion fills rivers and reservoirs Rapid runoff causes flooding

After Deforestation

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

Case Study: Living Dangerously on Floodplains in Bangladesh

Dense population

Located on coastal floodplain

Moderate floods maintain fertile soil

Increased frequency of large floods

Effects of development in the Himalayan foothills

Destruction of coastal wetlands

We Can Reduce Flood Risks

Rely more on nature’s systems• Wetlands• Natural vegetation in watersheds

Rely less on engineering devices• Dams• Levees

Solutions: Reducing Flood Damage

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

Active Figure: Effects of deforestation