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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

Unconfined Aquifer Recharge Area Precipitation Confined Recharge Area Runoff Evaporation and transpiration Evaporation Flowing artesian well Infiltration Water table Well requiring a pump Stream Infiltration Less permeable material such as clay Lake Fig. 13-3, p. 316

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

Average annual precipitation (centimeters) Less than 41 41 –81 81 –122 More than 122 Fig. 13-4a, p. 317

Fig. 13-4b, p. 317

Acute shortage Shortage Adequate supply Metropolitan regions with population greater than 1 million Fig. 13-4b, p. 317

Water Hotspots in 17 Western U.S. States

Washington Oregon Idaho Montana Wyoming North Dakota 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 Fig. 13-5, p. 318

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

Europe Asia North America South America Africa Stress High None Australia Fig. 13-6, p. 319

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

TRADE-OFFS Withdrawing Groundwater Advantages Useful for drinking and irrigation Disadvantages Aquifer depletion from overpumping Available year-round Exists almost everywhere Sinking of land (subsidence) from overpumping 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 Fig. 13-7, p. 321

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.

Groundwater Overdrafts: High Moderate Minor or none Fig. 13-9, p. 322

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

WYOMING SOUTH DAKOTA COLORADO NEBRASKA KANSAS Saturated thickness of Ogallala Aquifer OKLAHOMA NEW MEXICO TEXAS 0 Miles 100 0 160 Kilometers 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) Fig. 13-10, p. 323

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

SOLUTIONS Groundwater Depletion Prevention Waste less water Subsidize water conservation Limit number of wells Do not grow water intensive crops in dry areas Control Raise price of water to discourage waste Tax water pumped from wells near surface waters Set and enforce minimum stream flow levels Divert surface water in wet years to recharge aquifers Fig. 13-11, p. 324

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

35 30 25 20 15 10 5 Hoover Dam completed (1935) Glen Canyon Dam completed (1963) 0 1910 1920 1930 1940 1950 Year 1960 1970 1980 1990 2000 Fig. 13-16, p. 328

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 CH 4 • Worse than CO 2 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

Sacramento River North Bay Aqueduct CALIFORNIA

Shasta Lake Oroville Dam and Reservoir

NEVADA

Feather River Lake Tahoe

Sacramento San Francisco South Bay Aqueduct

San Luis Dam and Reservoir

Fresno

Hoover Dam and Reservoir (Lake Mead)

California Aqueduct Santa Barbara Los Angeles Aqueduct Colorado River Aqueduct Los Angeles UTAH

Colorado River

ARIZONA Central Arizona Phoenix Project San Diego

Salton Sea

Tucson MEXICO Fig. 13-17, p. 330

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

1976 2006 Stepped Art Fig. 13-18a, p. 331

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

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%) (efficiency 80% with low-pressure sprinkler and 90 –95% with LEPA sprinkler) Above- or below-ground pipes or tubes deliver water to individual plant roots.

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

Fig. 13-20, p. 335

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%) (efficiency 80% with low-pressure sprinkler and 90 –95% with LEPA sprinkler) Above- or below-ground pipes or tubes deliver water to individual plant roots.

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

Stepped Art Fig. 13-20, p. 335

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

SOLUTIONS Sustainable Water Use Waste less water and subsidize water conservation Do not deplete aquifers 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 Slow population growth Fig. 13-23, p. 337

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

Oxygen released by vegetation Diverse ecological habitat Evapotranspiration Trees reduce soil erosion from heavy rain and wind Agricultural land Tree roots stabilize soil Forested Hillside Vegetation releases water slowly and reduces flooding Fig. 13-25a, p. 339

Tree plantation Roads destabilize hillsides Gullies and landslides Heavy rain erodes topsoil Silt from erosion fills rivers and reservoirs After Deforestation Evapotranspiration decreases Overgrazing accelerates soil erosion by water and wind Winds remove fragile topsoil Agricultural land is flooded and silted up Rapid runoff causes flooding Fig. 13-25b, p. 339

Oxygen released by vegetation Tree plantation Diverse ecological habitat Tree roots stabilize soil Evapotranspiration Trees reduce soil erosion from heavy rain and wind Vegetation releases water slowly and reduces flooding Agricultural land 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 Forested Hillside After Deforestation Stepped Art Fig. 13-25a, p. 339

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

SOLUTIONS Reducing Flood Damage Prevention Preserve forests on watersheds Preserve and restore wetlands in floodplains Tax development on floodplains Use floodplains primarily for recharging aquifers, sustainable agriculture and forestry Control Straighten and deepen streams (channelization) Build levees or floodwalls along streams Build dams Fig. 13-26, p. 340

Active Figure: Effects of deforestation

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