environmental science 13e chapter 11: water resources and water pollution
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ENVIRONMENTAL SCIENCE13eCHAPTER 11: Water Resources and Water Pollution
Water video questionsHow much fresh water on earth?How much in rivers, lakes, and streams?How much is used for growing food?How much water needed to produced a pound of beef?A cup of coffee?In US how much water is used for flushing toilet?How much water does the average American use per day?How many people today lack access to clean, safe water supply?
Core Case Study: The Colorado River Story1400 miles through 7 states14 dams and reservoirsElectricity for 30 million peopleWater for 15% of U.S. crops and livestockWater for desert citiesVery little water reaches the Gulf of California
5 major problems Colorado river basin includes some of driest lands in US and MexicoFor its size river has only modest flowsLegal pacts signed in 1922 and 1944 allocated more water for human use in US and Mexico than the river can supply (even when no drought) and allocated no water for environmental purposes)Since 1960 river has rarely flowed fully to Gulf of California because of reduced water flow (dams), increased water withdrawals, and prolonged droughtMajor PollutionReference p. 242
Fig. 11-1, p. 238
Fig. 11-2, p. 238
11-1 Will We Have Enough Usable Water?Concept 11-1A We are using available freshwater unsustainably by wasting it, polluting it, and charging too little for this irreplaceable natural resource.Concept 11-1B One of every six people does not have sufficient access to clean water, and this situation will almost certainly get worse.
Importance and Availability of Water (1)Earth as a watery world saltwater covers about 71% of the earths surfaceWater is one of our most poorly managed resourcesWater access is a global health issue3900 children under 5 die every day from waterborne diseaseWater is an economic issue because it is vital for reducing poverty and producing food and energy
Importance and Availability of Water (2)National and global security issue because of increasing tensions within and between nations over access to limited water resourcesEnvironmental issue because excessive withdrawal of water from rivers and aquifers results in dropping water tables, lower river flows, shrinking lakes, and losses of wetlands
Freshwater availability 0.024%GroundwaterLakesRiversStreams
Fig. 11-3, p. 240
Groundwaterimportant terms to knowGroundwater: water that sinks into the soil and is stored in slowly flowing and slowly renewed underground reservoirs called aquifersZone of saturation: area where all available pores in soil and rock are filled by waterWater table: upper surface of the zone of saturationAquifers: porous, water saturated layers of sand, gravel, or bedrock that can yield an economically significant amount of water Natural recharge: natural replenishment of an aquifer by precipitation that percolates downward through soil and rockLateral recharge: recharge occurring from the side by rivers and streams
Surface WaterSurface runoffWatershed (drainage) basinReliable runoff 1/3 of totalRunoff use (worldwide)Domestic 10%Agriculture 70%Industrial 20%
Case Study: Freshwater Resources in the United States (1)Uneven distributionContamination by agriculture and industryEastern U.S.Western U.S.Groundwater withdrawal: ~50% of total useDrought: prolonged period in which precipitation is at least 70% lower and evaporation is higher than normal in an area that is normally not dry
Case Study: Freshwater Resources in the United States (2)Arid and semiarid West:85% of water to irrigate thirsty cropsWater hot spotsSouthwest: permanent drying by 2050Water tables dropping 36 states to face water shortages by 2013 (drought, rising temps, pop growth, urban sprawl, and excessive use and waste of water)
Fig. 11-4, p. 241
Fig. 11-5, p. 242CaliforniaUnmet rural water needsHighly likely conflict potentialModerate conflict potentialSubstantial conflict potentialWashingtonMontanaNorthDakotaSouthDakotaNebraskaKansasOklahomaTexasNewMexicoArizonaColoradoWyomingIdahoOregonNevadaUtahWater hotspots in 17 Western states that, by 2025, could face intense conflicts over scarce water needed for urban growth, irrigation, recreation, and wildlife. Some analysts suggest that this is a map of places not to live in the forseeable future.
Freshwater ShortagesCauses of water scarcityDry climateDroughtToo many peopleWasting water2050: 60 countries will face water stress1 of 7 people no regular access to clean waterPotential international conflicts over water
Fig. 11-6, p. 243Stress on the worlds major river basins, based on a comparison of the amount of water available with the amount used by humans.
11-2 How Can We Increase Water Supplies? Concept 11-2A Groundwater used to supply cities and grow food is being pumped from aquifers in some areas faster than it is renewed by precipitation.Concept 11-2B Using dams, reservoirs, and transport systems to provide water to arid regions has increased water supplies in some areas, but has disrupted ecosystems and displaced people.
11-2 How Can We Increase Water Supplies? Concept 11-2C 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 SuppliesWithdrawing groundwaterDams and reservoirsTransporting surface waterDesalinationWater conservation
Fig. 11-7, p. 244Trade-OffsAquifer depletion fromoverpumpingSinking of land (subsidence)from overpumpingAquifers polluted fordecades or centuriesSaltwater intrusion intodrinking water supplies nearcoastal areasReduced water flows intosurface watersIncreased cost andcontamination from deeperwellsCheaper to extract thanmost surface watersNo evaporation lossesRenewable if notoverpumped orcontaminatedExists almost everywhereAvailable year-roundUseful for drinking andirrigationAdvantagesDisadvantagesWithdrawing Groundwater
Groundwater WithdrawalMost aquifers are renewableU.S. groundwater withdrawn 4X faster then its replenished Ogallala aquiferCalifornias Central Valley and agriculture
Fig. 11-8, p. 244GroundwaterOverdrafts:HighModerateMinor or noneAreas of greatest aquifer depletion from groundwater overdraft in the continental United States. Aquifer depletion in also high in Hawaii and Puerto Rico (not shown).
Fig. 11-9, p. 245Waste less waterRaise price of water todiscourage wasteTax water pumped fromwells near surface watersSet and enforce minimumstream flow levelsDivert surface water in wetyears to recharge aquifersSolutionsGroundwater DepletionControlPreventionDo not grow water-intensivecrops in dry areasLimit number of wellsSubsidize water conservation
Science Focus: Are Deep Aquifers the Answer?Could have enough water to supply billions of people for centuriesConcernsNonrenewable Geological and ecological impacts of pumping them is unknownNo treaties to govern water rightsCosts unknown and could be high
Reservoir usefulfor recreationand fishingProvidesirrigation waterabove andbelow damProvides waterfor drinkingDeprivesdownstreamcropland andestuaries ofnutrient-rich siltRisk of failureand devastatingdownstreamfloodingDisrpuptsmigration andspawning ofsome fishCan producecheap electricity(hydropower)ReducesdownstreamfloodingFlooded landdestroys forestsor cropland anddisplaces peopleLarge losses ofwater throughevaporationFig. 11-10, p. 246
Overtapped Colorado River BasinOnly small amount reaches Gulf of CaliforniaThreatened speciesClimate change will likely decrease flowsLess water in SouthwestPolitical and legal battles Silt behind dams not reaching delta and will eventually fill up reservoirs
Fig. 11-11, p. 247Flow (billion cubic meters)051015202530Year1910192019301940195019601970198019902000Hoover Damcompleted (1935)Glen CanyonDam completed(1963)
California Water ProjectDams, pumps, aqueductsSouthern California would otherwise be desertClimate change will reduce water availability in CaliforniaPeople in southern California may have to moveGroundwater already being depleted
Fig. 11-12, p. 247TucsonNorth BayAqueductCALIFORNIANEVADAUTAHARIZONAMEXICOSouth BayAqueductCalifornia AqueductSacramentoFresnoSanta BarbaraLos AngelesSan DiegoShasta LakeOroville Dam andReservoirFeatherRiverLake TahoeHoover Damand Reservoir(Lake Mead)ColoradoRiverSacramentoRiverSan FranciscoSan Luis Damand ReservoirSan Joaquin ValleySalton SeaPhoenixLos AngelesAqueductColorado RiverAqueductCentral ArizonaProject
Aral Sea Disaster (1)Large-scale water transfers in dry central AsiaWater loss and salinity increaseWetland destruction and wildlifeFish extinctions hurt fishing industry
Aral Sea Disaster (2)Wind-blown saltWater pollutionClimatic changesRestoration efforts
Stepped ArtFig. 11-13, p. 248Satellite photos show the sea in 1976 and in 2006.19762006
Removing Salt from SeawaterDesalinationDistillationReverse osmosis13,000 plants in 125 countries
Major Problems with DesalinationHigh costDeath of marine organismsLarge quantity of brine wastes
11-3 How Can We Use Water More Sustainably?Concept 11-3 We can use water more sustainably by cutting water waste, raising water prices