global water resources unit 4. core case study: water conflicts in the middle east: a preview of the...
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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