geos109 lect10 water
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Water and Water Pollution
Case Study: Water Conflicts
Water shortages in the Middle East
Nile River
Jordan Basin
Tigris and Euphrates Rivers
Three Major River Basinsin the Middle East
Will We Have Enough Water?
We are using available freshwater unsustainably• wasting it • polluting it • charging too little for this irreplaceable natural
resource.
One of every six people do not have sufficient access to clean water, and this situation will almost certainly get worse.
Importance and Availability of Water
Why is water so important?
Earth as a watery world – 71%
Freshwater availability – 0.024%
Poorly managed resource
Hydrologic cycle
Water pollution
Confining impermeable rock layer
Less permeable material such as clay
Stream
Wellrequiringa pump Lake
Unconfined aquifer
Flowingartesian well
Runoff
ConfinedRechargeArea
Watertable
Confined aquifer
Infiltration
EvaporationEvaporation and transpiration
Infiltration
Unconfined Aquifer Recharge Area
Recharge Unconfined Aquifer
Precipitation
Groundwater
Zone of saturation
Water table
Aquifers
Natural recharge
Surface Water
Surface runoff
Watershed (drainage) basin
Reliable runoff – 1/3 of total
Runoff use• Domestic – 10%• Agriculture – 70%• Industrial use – 20%
Case Study: Freshwater Resources in the United States
Uneven distribution
Contamination
Eastern U.S.
Western U.S.
Groundwater withdrawal – 50%
Stepped Art
Average annual precipitation (centimeters)
Less than 41
41-81
81-122
More than 122
Acute shortage
Shortage
Adequate supply
Metropolitan regions with population greater than 1 million
Water Hot Spots in Western States
Freshwater Shortages
Causes of water scarcity• Dry climate• Too many people
1 of 6 people – no regular access to clean water• Over one billion have no access to improved
drinking water • According to the U.N. children's agency UNICEF,
polluted water and lack of basic sanitation claim the lives of over 1.5 million children every year, mostly from water-borne diseases.
While most people living in Western Europe can access safe water, only 50% of people living in Central Africa can do this. The largest population without access to safe tap water is in China (25%)
waterwiki.net/index.php/Unsafe_Water
Stress on World’s River Basins
How Can We Increase Water Supplies?
Groundwater used to supply cities and grow food is being pumped from aquifers in some areas faster than it is renewed by precipitation.
Using dams, reservoirs, and transport systems to transfer water to arid regions has increased water supplies in those areas, but has disrupted ecosystems and displaced people.
How Can We Increase Water Supplies?
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.
Increasing Freshwater Supplies
Withdrawing groundwater
Dams and reservoirs
Transporting surface water
Desalination
Water conservation
Better use of natural hydrologic cycle
Aquifer Depletion from Groundwater Overdraft in the United States
Saltwater Intrusion intoCoastal Water Wells
Trade-offs of Large Dams and Reservoirs
California Water Project and Central Arizona Project
Aral Sea Disaster
Large-scale water transfers in dry central Asia
Salinity
Wetland destruction and wildlife
Fish extinctions and fishing
Aral Sea Disaster
Wind-blown salt
Water pollution
Climatic changes
Restoration efforts
Shrinking Aral Sea
Removing Salt from Seawater
Desalination
Distillation
Reverse osmosis
15,000 plants in 125 countries
Major Problems with Desalination
High cost Death of marine organisms Large quantity of brine wastes Future economics
Ashkelon Plant supplies 15%of Israel’s Householdswater needs-Largest plant in 2005
How Can We Use Water More Sustainably?
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 (1)
Benefits of water conservation
Worldwide – 65-70% loss • Evaporation, leaks
Water prices, government subsides, waste
Reducing Water Waste (2)
Improve irrigation efficiency
Improve collection efficiency
Use less in homes and businesses
Major Irrigation Systems
Reducing Irrigation Water Waste
Reducing Water Waste
Sustainable Water Use
What Can You Do?
How Can We Reduce the Threat of Flooding?
We can improve flood control by protecting more wetlands and natural vegetation in watersheds and by not building in areas subject to frequent flooding.
Benefits of Floodplains (1)
Highly productive wetlands
Provide natural flood and erosion control
Maintain high water quality
Recharge groundwater
Benefits of Floodplains (2)
Fertile soils
Nearby rivers for 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
Before and During a Flood inSt. Louis, Missouri
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 wetlands
Hillside Before and After Deforestation
Reducing Flood Damage
How Can We Best Deal with Water Pollution? (1)
Streams can cleanse themselves of many pollutants if we do not overload them.
Preventing water pollution usually works better and costs less than trying to clean it up.
How Can We Best Deal with Water Pollution? (2)
Reducing water pollution requires preventing it, working with nature in treating sewage, cutting resource use and waste, reducing poverty, and slowing population growth.
Water Pollution Sources
Water pollution
Point sources• Discharge at specific locations• Easier to identify, monitor, regulate
Nonpoint sources• Runoff of chemicals and sediment• Agriculture• Control is difficult and expensive
Major Water Pollutants and Their Sources
Pollution in Streams
Lake Pollution (1)
Dilution less effective than with streams• Stratification• Low flow
Lakes are more vulnerable than streams
Eutrophication – natural aging process• Oligotrophic
Oligotrophic and Eutrophic Lakes
Groundwater Pollution (1)
Sources
Slow flow, dilution, dispersion
Low dissolved oxygen
Fewer bacteria
Cooler temperatures
Groundwater Pollution (2)
Longtime scale for natural cleansing• Degradable wastes – organic matter• Slowly degradable wastes – DDT• Nondegradable wastes – lead, arsenic, fluoride
Sources of Groundwater Pollution
Extent of Groundwater Pollution
Global scale – not much known
Monitoring is very expensive
Underground fuel tank leakage• MTBE
Arsenic
Protecting groundwater – prevention is best!
Preventing and Cleaning Up Groundwater Pollution
Ocean Pollution
Coastal areas – highly productive ecosystems• Occupied by 40% of population• Twice that population by 2050• About 80% marine pollution originates on land
Deep ocean waters• Some capacity to dilute, disperse, degrade
pollutants• Ocean dumping controversies• Assimilative capacity?
Coastal Water Pollution
Science Focus: Oxygen Depletion in the Northern Gulf of Mexico
Oil Pollution in Oceans
Crude and refined petroleum
Tanker accidents – Exxon Valdez
Urban and industrial runoff
Effects of Oil Pollution on Ocean Ecosystems
Volatile organic hydrocarbons• Kill larvae• Destroys natural insulation and buoyancy
Heavy oil• Sinks and kills bottom organisms• Coral reefs die
Oil Cleanup Methods
Current methods recover no more than 15%
Prevention is most effective method• Control runoff• Double haul tankers
Preventing and Cleaning Up Pollution in Coastal Waters
Preventing Nonpoint Source Pollution (1)
Mostly agricultural waste
Use vegetation to reduce soil erosion
Reduce fertilizer use
Preventing Nonpoint Source Pollution (2)
Use plant buffer zones around fields and animal feedlots
Keep feedlots away from slopes, surface water and flood zones
Integrated pest management
Laws for Reducing Point Source Pollution
Clean Water Act
Water Quality Act
Discharge trading controversies
Sewage Treatment Systems
Rural and suburban areas – septic tank
Urban areas – wastewater treatment plants• Primary treatment – physical process• Secondary treatment – biological process• Chlorination – bleaching and disinfection
Primary and Secondary Sewage Treatment
Improving Sewage Treatment
Systems that exclude hazardous waste
Nonhazardous waste substitutes
Composting toilet systems
Reducing Water Pollution from Point Sources in the U.S.
Impressive achievements
Bad news – 2006 survey• 45% of lakes and 40% of streams too polluted for
fishing and swimming• Runoff polluting 7 of 10 rivers• Fish caught in 1/4 of waterways unsafe to eat
Should the Clean Water Act be Strengthened?
Yes – environmentalists
No – farmers and developers
State and local officials want more discretion
Drinking Water Quality
Purification of urban drinking water
Developed versus developing countries
Is Bottled Water the Answer?
120 to 7,500 times the cost of tap water
About 1/4 is ordinary tap water
About 40% of bottled water contaminated
Water testing
Water purifiers
Methods for Preventing and Reducing Water Pollution
What Can We Do?