Global Water Resources

Unit 4

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

Water shortages may be the biggest problem facing the Middle East

Most freshwater comes from three river basins:• Nile River• Jordan River• Tigris and Euphrates Rivers

Peacefully solving the problems will require shared sacrifice among all the countries in the region.

Three Major River Basins in the Middle East

The Nile

Jordan River

Tigris and Euphrates Rivers

Egypt and the Nile

The Nile provides Egypt with 97% of its water.

The upstream countries of Ethiopia and Sudan plan to divert more water for their own use.

Egypt will be forced to take action by…..

• Importing more food to reduce irrigation

• Cutting its population growth

• Working out water sharing agreements, OR

• Going to war with Ethopia and Sudan.

Will We Have Enough Usable Water?

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

One of every six people in the world does not have sufficient access to clean water, and this situation will almost certainly get worse.

Why is water so important?

Why is water so important? The Earth is a watery world: 71% of the Earth’s

surface is covered by water. But only 0.024% is available to us as liquid

freshwater. With few exceptions, water is a poorly managed

resource worldwide. The United States is the world’s largest user of

water.

Access to water is…

A global health issue: The world’s leading cause of illness is unsafe water

An economic issue: Water is essential for the functioning of modern economies.

A women’s and children’s issue: Women and children are the primary gatherers of water in the developing world

A national and global security issue: Future wars may be fought over water.

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

People divided into• Water haves• Water have-nots

The lack of sufficient water to meet the needs of the people in a country or region is called hydrological poverty

Experts believe that developing water shortages around the world are one of the three primary problems the world faces during this century.

Groundwater

Ground water is the water found underground in aquifers.

Water table is the depth at which groundwater is found. The water table can rise or fall depending on climate and extraction rates.

Aquifers are vast underground deposits of water that supply 50% of the world’s freshwater.

Aquifers are a geologic layer consisting of underground caverns and porous layers of sand gravel and bedrock where groundwater flows.

Surface Water

Surface runoff is the term used for the rain and groundwater that flows into streams and rivers

Watershed (drainage) basin is defined as the total area of land that flows into a particular river.

Only 1/3 of surface runoff is considered reliable runoff that can be used by humans. The other 2/3rds is lost to flooding or can’t be captured.

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

Worldwide Usage of Surface Runoff

Of the 1/3 of surface runoff that is usable. Throughout the world….• Cities and residences use 10%• Agriculture uses 70%, mostly for irrigation.• Industry uses 20%. For example, it takes 120,000

gallons of water to make one automobile!

Water shortages in the United States

By 2012 at least 36 states are likely to face water shortages due to• drought (exacerbated by global warming)• population growth• Urban sprawl (sprawling suburbs use much

more water per capita than dense cities)• Waste of water. Experts believe that low prices

are the leading case of water waste.

Fig. 13-4a, p. 317

Average annual precipitation (centimeters)

41–81 More than 122

Less than 41 81–122

Fig. 13-4b, p. 317

Shortage

Acute shortage

Adequate supply

Metropolitan regions with population greater than 1 million

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 “hot spots” in 17 Western States

Long-Term Severe Drought Is Increasing

Causes• Extended period of below-normal rainfall• Diminished groundwater• Global warming?

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

Who Should Own and Manage Freshwater Resources?

Most water resources are owned by governments

And are managed as publicly owned resources Veolia and Suez: Two French companies.• Actively buy and manage water resources around

the world.• They have achieved successful outcomes in

many areas but controversy follows.

Who Should Own and Manage Freshwater Resources?

Bechtel Corporation. Controversial water management in Bolivia led to riots that drove them from the country.

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

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

India, China, and the United States• Three largest grain producers in the world• All are over pumping aquifers for irrigation of

crops

• The United State is withdrawing groundwater at a rate that is 4-times faster than it can be recharged.

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

Aquifer Depletion in the United States

Ogallala aquifer: World’s largest known aquifer• Irrigates the Great Plains• Water table lowered more than 30 meters in

many places.• 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.

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

Groundwater Overpumping in Coastal Areas can cause Catastrophic Problems

Contamination of the groundwater with saltwater intrusion

Groundwater becomes undrinkable and unusable for irrigation

Growing problem in Florida and the Gulf Coast, including Texas.

Saltwater Intrusion

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

Active Figure: Threats to aquifers

Large Dams and Reservoirs Have Advantages and Disadvantages

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

• Release runoff as needed to control floods.• Generate electricity• Supply irrigation water• Provide recreational opportunities

(reservoirs). All the lakes in Texas are reservoirs except

Caddo Lake

Advantages of Dams

• Increase the reliable runoff available

• Reduce flooding• Grow crops in arid

regions• Reliable carbon-free

supply of electricity

China’s Three Gorges Dam

Large Dams and Reservoirs Have Advantages and Disadvantages (3)

Disadvantages• Displaces people behind the dam• Leads to devastating flooding if there is a failure.• Impaired ecological services of rivers (disrupt

migrations of fish)• Loss of plant and animal species• Fill up with sediment within 50 years• Reduces downstream flow of nutrients and

sediments.

The Ataturk Dam Project in Eastern Turkey

Case Study: The Colorado River Basin— An Overtapped Resource

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

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

What will happen if some of the reservoirs empty out?

Economic and ecological catastrophe. Cities like Las Vegas, Phoenix and Los Angeles

will run out of water Political and legal battles over water will be

intense.

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

The Aral Sea Disaster

Large-scale water transfer project in dry central Asia removed the source of the Aral Sea.

Surface level of the sea dropped by 22 meters Salt and sand from the dry sea bottom have

spread by wind as far as 300 miles. Massive wetlands destruction. Populations of

fish and wildlife have been driven to near extinction.

The Aral Sea Disaster– a Vanishing Freshwater Lake

1976 2006

Ship Stranded in Desert Formed by Shrinkage of the Aral Sea

Removing Salt from Seawater Seems Promising but Is Costly

Two primary methods of Desalination• Distillation turns water to vapor and condenses

the vapor back to liquid (salt is left behind)

• Reverse osmosis uses high pressure to force saltwater through a membrane filter that excludes salt ions.

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

Desalination plant in Saudi Arabia

Problems with desalination

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

organisms Large quantity of brine wastes (what do we do

with all that salt?)

We Can Cut Water Waste in Irrigation

Flood irrigation is the most wasteful form of irrigation.

Center pivot, low pressure sprinkler are better Low-energy, precision application sprinklers

better still. Drip or trickle irrigation offers the greatest

conservation of water.

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

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

Dangers of floodplains and Floods

Floods are deadly and destructive Human activities worsen floods Failing dams and water diversion can be

catastrophic (Johnstown Flood) 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

Solutions: Reducing Flood Damage