Geos109 lect10 water
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  • Figure 11.2: Natural capital: groundwater system. An unconfined aquifer is an aquifer with a permeable water table. A confined aquifer is bounded above and below by less permeable beds of rock where the water is confined under pressure. Some aquifers are replenished by precipitation; others are not.
  • Figure 11.3: Average annual precipitation and major rivers (top) and water-deficit regions in the continental United States and their proximity to metropolitan areas having populations greater than 1 million (bottom). Question: If you live in the United States, do you live in a water-short area? (Data from U.S. Water Resources Council and U.S. Geological Survey)

Geos109 lect10 water Geos109 lect10 water Presentation Transcript

  • 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 naturalresource. One of every six people do not have sufficientaccess to clean water, and this situation willalmost 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 layerLesspermeable materialsuch as clayStreamWellrequiringa pump LakeUnconfined aquiferFlowingartesian wellRunoffConfinedRechargeAreaWatertableConfined aquiferInfiltrationEvaporationEvaporation and transpirationInfiltrationUnconfined Aquifer Recharge AreaRechargeUnconfined AquiferPrecipitation
  • 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 theUnited States Uneven distribution Contamination Eastern U.S. Western U.S. Groundwater withdrawal – 50%
  • Stepped ArtAverage annual precipitation (centimeters)Less than 4141-8181-122More than 122Acute shortageShortageAdequate supplyMetropolitan 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 improveddrinking water• According to the U.N. childrens agency UNICEF,polluted water and lack of basic sanitation claimthe lives of over 1.5 million children every year,mostly from water-borne diseases.
  • While most people living inWestern Europe can accesssafe water, only 50% ofpeople living in Central Africacan do this. The largestpopulation without access tosafe 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 growfood is being pumped from aquifers in someareas faster than it is renewed by precipitation. Using dams, reservoirs, and transport systemsto transfer water to arid regions has increasedwater supplies in those areas, but has disruptedecosystems 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 brinemust be disposed of without harming aquatic orterrestrial ecosystems.
  • Increasing Freshwater Supplies Withdrawing groundwater Dams and reservoirs Transporting surface water Desalination Water conservation Better use of natural hydrologic cycle
  • Aquifer Depletion from GroundwaterOverdraft in the United States
  • Saltwater Intrusion intoCoastal Water Wells
  • Trade-offs of Large Dams and Reservoirs
  • California Water Project and CentralArizona 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 MoreSustainably? We can use water more sustainably by cuttingwater waste, raising water prices, slowingpopulation growth, and protecting aquifers,forests, and other ecosystems that store andrelease 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 ofFlooding? We can improve flood control by protecting morewetlands and natural vegetation in watershedsand by not building in areas subject to frequentflooding.
  • 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 WaterPollution? (1) Streams can cleanse themselves of manypollutants if we do not overload them. Preventing water pollution usually works betterand costs less than trying to clean it up.
  • How Can We Best Deal with WaterPollution? (2) Reducing water pollution requires preventing it,working with nature in treating sewage, cuttingresource use and waste, reducing poverty, andslowing 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 TheirSources
  • 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 UpGroundwater 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, degradepollutants• Ocean dumping controversies• Assimilative capacity?
  • Coastal Water Pollution
  • Science Focus: Oxygen Depletion in theNorthern Gulf of Mexico
  • Oil Pollution in Oceans Crude and refined petroleum Tanker accidents – Exxon Valdez Urban and industrial runoff
  • Effects of Oil Pollution on OceanEcosystems 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 inCoastal 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 animalfeedlots Keep feedlots away from slopes, surface waterand flood zones Integrated pest management
  • Laws for Reducing Point SourcePollution 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 SewageTreatment
  • Improving Sewage Treatment Systems that exclude hazardous waste Nonhazardous waste substitutes Composting toilet systems
  • Reducing Water Pollution from PointSources in the U.S. Impressive achievements Bad news – 2006 survey• 45% of lakes and 40% of streams too polluted forfishing and swimming• Runoff polluting 7 of 10 rivers• Fish caught in 1/4 of waterways unsafe to eat
  • Should the Clean Water Act beStrengthened? 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 ReducingWater Pollution
  • What Can We Do?