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
Water and Water Pollution
Case Study: Water Conflicts Water shortages in the Middle East Nile River Jordan Basin Tigris and Euphrates Rivers
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
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
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
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
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
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
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?
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