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Aquifer Depletion 1. Depletion is primarily caused by excessive groundwater pumping. 2. Water is pumped out of the ground faster than it is replenished 3. As a result of excessive pumping- The volume of stored groundwater is decreasing in many areas of the United States AQUIFER DEPLETION Negative impacts of groundwater depletion: 1. drying up of wells 2. reduction of water in streams and lakes 3. decrease in water quality 4. increased costs of pumping 5. land subsidence Land Subsidence Solutions Groundwater Depletion Prevention Control 1. Waste less water 1.Raise price of water to discourage waste 2. Subsidize water conservation 2. Tax water pumped from wells near surface waters 3. Limit number of wells 3. Set and enforce minimum stream flow levels 4. Do not grow water-intensive crops in dry areas 4.Divert surface water in wet years to recharge aquifers Fig. 11-9, p. 245 Trade-Offs Withdrawing Groundwater Advantages Disadvantages Useful for drinking and irrigation Aquifer depletion from overpumping Available year-round Sinking 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from deeper wells Fig. 11-7, p. 244 Groundwater Withdrawal • Most aquifers are renewable • U.S. groundwater is withdrawn 4 times faster then it’s replenished Areas of greatest aquifer depletion from groundwater overdraft in the continental United States. Aquifer depletion in also high in Hawaii and Puerto Rico (not shown). Groundwater Overdrafts: High Moderate Minor or none Fig. 11-8, p. 244 Removing Salt from Seawater • • • • Desalination Distillation Reverse osmosis 13,000 plants in 125 countries Major Problems with Desalination • High cost • Death of marine organisms • Large 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, 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 – Can be reduced to 15% • Increase the cost of water use – End subsidies for wasteful water use – Provide subsidies for efficient water use Reducing Water Waste (2) • Improve irrigation efficiency – Center pivot – Low-pressure sprinkler – Precision sprinklers – Drip irrigation • Use less in homes and businesses Fig. 11-16, p. 252 Solutions Sustainable Water Use Waste less water and subsidize water conservation Do not deplete aquifers Preserve water quality Protect forests, wetlands, mountain glaciers, watersheds, and other natural systems that store and release water Get agreements among regions and countries sharing surface water resources Raise water prices Slow population growth Fig. 11-17, p. 253 Fig. 11-18, p. 253 11-4 How Can We Reduce the Threat of Flooding? • Concept 11-4 We can lessen the threat of flooding by protecting more wetlands and natural vegetation in watersheds and by not building in areas subject to frequent flooding. Benefits of Floodplains • Highly productive wetlands • Provide natural flood and erosion control • Maintain high water quality • Recharge groundwater • Fertile soils • Nearby rivers for use and recreation • Flatlands for urbanization and farming Floods • • • • • • Deposit rich soils on floodplains Deadly and destructive Human activities worsen floods Failing dams and water diversion Hurricane Katrina and the Gulf Coast Climate change will increase coastal flooding Tree plantation Diverse ecological habitat Evapotranspiration Trees reduce soil erosion from heavy rain and wind Agricultural land Tree roots stabilize soil 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 Vegetation releases water slowly and reduces flooding Forested Hillside Silt from erosion fills rivers and reservoirs Rapid runoff causes flooding After Deforestation Stepped Art Fig. 11-19, p. 254 Case Study: Floodplains of Bangladesh • Dense population on coastal floodplain • Moderate floods maintain fertile soil • Increased frequency of large floods • Development in the Himalayan foothills • Destruction of coastal wetlands Solutions Reducing Flood Damage Prevention Control Preserve forests on watersheds Straighten and deepen streams (channelization) Preserve and restore wetlands in floodplains Tax development on floodplains Use floodplains primarily for recharging aquifers, sustainable agriculture and forestry Build levees or floodwalls along streams Build dams Fig. 11-20, p. 256 11-5 How Can We Deal with Water Pollution? • Concept 11-5A Streams can cleanse themselves of many pollutants if we do not overload them or reduce their flows. • Concept 11-5B 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 • Point sources – Discharge at specific locations – Easier to identify, monitor, regulate • Nonpoint sources – Broad, diffuse areas – Runoff of chemicals and sediment – Agriculture – Control is difficult and expensive Table 11-1, p. 257 Stream Pollution • • • • Natural recovery processes Oxygen sag curve Effective regulations in the U.S. Problems in developing countries Dilution and decay of degradable, oxygen-demanding wastes (or heated water) in a stream, showing the oxygen sag curve (blue) and the curve of oxygen demand (red) Point source Fig. 11-21, p. 258 Highly polluted river in China. Fig. 11-22, p. 259 Individuals Matter: John Beal p. 258 • Restored Hamm Creek in Washington State • Persuaded companies to stop polluting the creek, hauled out many truckloads of trash, began 15 yr project of planting thousands of trees along streams banks, also restored natural waterfalls and salmon spawning beds • Outstanding example of Stewardship based on the idea that “All sustainability is local” • http://www.youtube.com/watch?v=5smNWchqo6 o Lake Pollution • Dilution less effective than with streams – Stratification – Low flow • Lakes are more vulnerable than streams • Eutrophication – natural aging process • Oligotrophic Cultural Eutrophication • Nitrate- and phosphate-containing effluents • Dense colonies of plants, algae, cyanobacteria • Can lead to die-off of fish and other animals • Prevent by limiting phosphate and nitrate use • Lakes can be cleaned, and can recover Groundwater Pollution (1) • • • • • Pollution sources Slow flow, dilution, dispersion Low dissolved oxygen Fewer bacteria Cooler temperatures Groundwater Pollution (2) • Long time scale for natural cleansing – Degradable wastes – organic matter – Slowly degradable wastes – DDT – Nondegradable wastes – lead, arsenic Polluted air Hazardous waste injection well Pesticides and fertilizers Coal strip mine runoff Deicing road salt Pumping well Waste lagoon Gasoline station Water pumping well Buried gasoline and solvent tanks Cesspool, septic tank Sewer Landfill Leakage from faulty casing Accidental spills Discharge Confined aquifer Groundwater flow Fig. 11-23, p. 260 Extent of Groundwater Pollution • • • • • Global scale – not much known Monitoring is very expensive Underground fuel tank leakage Arsenic Protecting groundwater – prevention is best and least expensive Solutions Groundwater Pollution Prevention Cleanup Find substitutes for toxic chemicals Pump to surface, clean, and return to aquifer (very expensive) Keep toxic chemicals out of the environment Install monitoring wells near landfills and underground tanks Require leak detectors on underground tanks Inject microorganisms to clean up contamination (less expensive but still costly) Ban hazardous waste disposal in landfills and injection wells Store harmful liquids in aboveground tanks with leak detection and collection systems Pump nanoparticles of inorganic compounds to remove pollutants (still being developed) Fig. 11-24, p. 261 Purifying Drinking Water • Developed countries – Reservoir storage – Purification plant • Developing countries without purification plants – Clear plastic bottle in sun, with black side – http://www.grilink.org/sunwater.htm – LifeStraw The Lifestraw, designed by Torben Vestergaard Frandsen http://www.youtube.com/watch?feature=fvwp&NR=1&v=fZwe5B8FaoU Fig. 11-25, p. 263 Science Focus: Is Bottled Water the Answer? • 500-1000 times the cost of tap water – Americans spent $15 billion in 2007 • About 1/4 is ordinary tap water • About 40% of bottled water contaminated • Water testing standards lower than for tap water • Environment: energy use, pollution Bottled Water • http://www.mnn.com/food/healthyeating-recipes/stories/5-reasons-notto-drink-bottled-water# Ocean Pollution • Coastal areas – highly productive ecosystems – Occupied by 40% of population – Coastal populations will double by 2050 – About 80% marine pollution originates on land • Ocean dumping controversies • Algal blooms • Oxygen-depleted zones Industry Nitrogen oxides from autos and smokestacks, toxic chemicals, and heavy metals in effluents flow into bays and estuaries. Cities Toxic metals and oil from streets and parking lots pollute waters; sewage adds nitrogen and phosphorus. Urban sprawl Bacteria and viruses from sewers and septic tanks contaminate shellfish beds and close beaches; runoff of fertilizer from lawns adds nitrogen and phosphorus. Construction sites Sediments are washed into waterways, choking fish and plants, clouding waters, and blocking sunlight. Farms Runoff of pesticides, manure, and fertilizers adds toxins and excess nitrogen and phosphorus. Closed shellfish beds Closed beach Red tides Excess nitrogen causes explosive growth of toxic microscopic algae, poisoning fish and marine mammals. Oxygen-depleted zone Toxic sediments Chemicals and toxic metals contaminate shellfish beds, kill spawning fish, and accumulate in the tissues of bottom feeders. Oxygen-depleted zone Sedimentation and algae overgrowth reduce sunlight, kill beneficial sea grasses, use up oxygen, and degrade habitat. Healthy zone Clear, oxygen-rich waters promote growth of plankton and sea grasses,and support fish. Fig. 11-26, p. 263 Pacific Garbage Patch • http://www.youtube.com/watch?v=SQ h898IcOgM&feature=related Science Focus: Oxygen Depletion in the Northern Gulf of Mexico • Mouth of Mississippi River in spring and summer • Suffocates fish, crab, shrimp • Cultural eutrophication • Caused by fertilizer use in Mississippi watershed • Need less and more intelligent use of fertilizers • Need better flood control A large zone of oxygen-depleted water forms each year during the spring and summer in the Gulf of Mexico as a result of oxygen-depleting algal blooms. Evidence indicates that it is created mostly by huge inputs of nitrate plant nutrients from farms, cities, factories, and sewage treatment plants in the vast Mississippi River basin. Missouri River Mississippi River Basin Ohio River Mississippi River Depleted oxygen Stepped Art Fig. 11-A, p. 265 Case Study: Ocean Pollution from Oil • Crude and refined petroleum • Tanker accidents – Exxon Valdez • Urban and industrial runoff is largest source Effects of Oil Pollution on Ocean Ecosystems • Volatile organic hydrocarbons – Kill larvae – Destroy natural insulation and buoyancy of birds and mammals • Heavy oil – Sinks and kills bottom organisms – Coral reefs die Gulf of Mexico Oil Spill • http://www.youtube.com/watch?v=8U ax5FRWnvs&feature=related Oil Cleanup Methods • Current methods recover no more than 15% • Prevention is most effective method – Control runoff – Double-hull tankers Solutions Coastal Water Pollution Prevention Cleanup Reduce input of toxic pollutants Improve oil-spill cleanup capabilities Separate sewage and storm lines Ban dumping of wastes and sewage by ships in coastal waters Ban ocean dumping of sludge and hazardous dredged material Regulate coastal development, oil drilling, and oil shipping Require double hulls for oil tankers Use nanoparticles on sewage and oil spills to dissolve the oil or sewage (still under development) Require secondary treatment of coastal sewage Use wetlands, solar-aquatic, or other methods to treat sewage Fig. 11-27, p. 264 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 • Organic farming methods Laws for Reducing Point Source Pollution • Clean Water Act • Water Quality Act • Discharge trading controversies – Cap-and-trade of pollutants Case Study: Reducing Water Pollution from Point Sources in the U.S. • Impressive achievements since 1972 law • 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 • Gasoline storage tanks: tens of thousands leaking Sewage Treatment Systems • Rural and suburban areas – septic tanks • Urban areas – wastewater treatment plants – Primary sewage treatment – physical process – Secondary sewage treatment – biological process – Chlorination – bleaching and disinfection Primary and secondary sewage treatment. Primary Bar screen Grit chamber Secondary Settling tank Aeration tank Settling tank Sludge Raw sewage from sewers Activated sludge Chlorine disinfection tank To river, lake, or ocean (kills bacteria) Air pump Sludge digester Disposed of in landfill or ocean or applied to cropland, pasture, or rangeland Sludge drying bed Fig. 11-28, p. 268 Improving Sewage Treatment • Systems that exclude hazardous and toxic chemicals • Require businesses to remove harmful chemicals before sewage sent to treatment plant • Reduce or eliminate use of toxic chemicals • Composting toilet systems • Wetland-based sewage treatment Science Focus: Treating Sewage by Working with Nature • Living machines • Tanks with increasingly complex organisms • Artificially created wetlands • Scientific principles of sustainability Fig. 11-29, p. 269 Fig. 11-30, p. 269 Three Big Ideas from This Chapter - #1 One of the world’s major environmental problems is the growing shortages of freshwater in parts of the world. Three Big Ideas from This Chapter - #2 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. Three Big Ideas from This Chapter - #3 Reducing water pollution requires preventing it, working with nature in treating sewage, cutting resource use and waste, reducing poverty, and slowing population growth.