Groundwater
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ENVIRONMENTAL SCIENCE 13e CHAPTER 11: Water Resources and Water Pollution Water video questions • • • • How 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? • http://www.youtube.com/watch?v=Fvk zjt3b-dU • http://www.youtube.com/watch?v=2p XuAw1bSQo Core Case Study: The Colorado River Story • • • • 1400 miles through 7 states 14 dams and reservoirs Electricity for 30 million people Water for 15% of U.S. crops and livestock • Water for desert cities • Very little water reaches the Gulf of California 5 major problems • Colorado river basin includes some of driest lands in US and Mexico • For its size river has only modest flows • Legal 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 drought • Major Pollution • Reference p. 242 Fig. 11-1, p. 238 Fig. 11-2, p. 238 • http://earthobservatory.nasa.gov/IOTD/vie w.php?id=1288 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 earth’s surface • Water is one of our most poorly managed resources • Water access is a global health issue – 3900 children under 5 die every day from waterborne disease • Water 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 resources • Environmental 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% – Groundwater – Lakes – Rivers – Streams Fig. 11-3, p. 240 Groundwater important terms to know • Groundwater: water that sinks into the soil and is stored in slowly flowing and slowly renewed underground reservoirs called aquifers • Zone of saturation: area where all available pores in soil and rock are filled by water • Water table: upper surface of the zone of saturation • Aquifers: 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 rock • Lateral recharge: and streams recharge occurring from the side by rivers • http://www.eoearth.org/article/Aquifer Surface Water • • • • Surface runoff Watershed (drainage) basin Reliable runoff – 1/3 of total Runoff use (worldwide) – Domestic – 10% – Agriculture – 70% – Industrial – 20% Case Study: Freshwater Resources in the United States (1) • Uneven distribution • Contamination by agriculture and industry • Eastern U.S. • Western U.S. • Groundwater withdrawal: ~50% of total use • Drought: 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 crops – Water hot spots – Southwest: “permanent drying” by 2050 • Water 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 Water 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. Washington Montana Oregon Idaho Wyoming North Dakota South Dakota Nebraska Nevada Utah Colorado California Kansas Oklahoma Arizona New Mexico Texas Highly likely conflict potential Substantial conflict potential Moderate conflict potential Unmet rural water needs Fig. 11-5, p. 242 Freshwater Shortages • Causes of water scarcity – Dry climate – Drought – Too many people – Wasting water • 2050: 60 countries will face water stress • 1 of 7 people – no regular access to clean water • Potential international conflicts over water Stress on the world’s major river basins, based on a comparison of the amount of water available with the amount used by humans. Fig. 11-6, p. 243 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 Supplies • • • • • Withdrawing groundwater Dams and reservoirs Transporting surface water Desalination Water conservation 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 withdrawn 4X faster then it’s replenished • Ogallala aquifer • California’s Central Valley and agriculture 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 Solutions Groundwater Depletion Prevention Control Waste less water Raise price of water to discourage waste Subsidize water conservation Tax water pumped from wells near surface waters Limit number of wells Set and enforce minimum stream flow levels Do not grow water-intensive crops in dry areas Divert surface water in wet years to recharge aquifers Fig. 11-9, p. 245 Science Focus: Are Deep Aquifers the Answer? • • Could have enough water to supply billions of people for centuries Concerns 1. Nonrenewable 2. Geological and ecological impacts of pumping them is unknown 3. No treaties to govern water rights 4. Costs unknown and could be high Provides irrigation water above and below dam Flooded land destroys forests or cropland and displaces peopl Large losses o water through evaporation Provides water for drinking Reservoir useful for recreation and fishing Can produce cheap electricity (hydropower) Reduces downstream flooding Deprives downstream cropland and estuaries of nutrient-rich si Risk of failure and devastatin downstream flooding Disrpupts migration and spawning of some fish Fig. 11-10, p. 246 Overtapped Colorado River Basin • Only small amount reaches Gulf of California – Threatened species • Climate change will likely decrease flows • Less water in Southwest – Political and legal battles • Silt behind dams not reaching delta and will eventually fill up reservoirs Flow (billion cubic meters) 30 Hoover Dam completed (1935) 25 20 15 Glen Canyon Dam completed (1963) 10 5 0 1910 1920 1930 1940 1950 1960 1970 1980 1990 2000 Year Fig. 11-11, p. 247 California Water Project • Dams, pumps, aqueducts • Southern California would otherwise be desert • Climate change will reduce water availability in California • People in southern California may have to move • Groundwater already being depleted Sacramento River CALIFORNIA NEVADA Shasta Lake Oroville Dam and Reservoir UTAH Feather Lake Tahoe River North Bay Aqueduct San Francisco Sacramento South Bay Aqueduct San Luis Dam and Reservoir Hoover Dam and Reservoir (Lake Mead) Fresno Colorado River Los Angeles Aqueduct California Aqueduct Santa Barbara Colorado River Aqueduct Los Angeles San Diego Salton Sea ARIZONA Central Arizona Project Phoenix Tucson MEXICO Fig. 11-12, p. 247 Aral Sea Disaster (1) • Large-scale water transfers in dry central Asia • Water loss and salinity increase • Wetland destruction and wildlife • Fish extinctions hurt fishing industry Aral Sea Disaster (2) • • • • Wind-blown salt Water pollution Climatic changes Restoration efforts 1976 2006 Satellite photos show the sea in 1976 and in 2006. Stepped Art Fig. 11-13, p. 248 Aral Sea • http://www.youtube.com/watch?v=9HfkZX LRYu8 • http://www.youtube.com/watch?v=Z0Pi61 SyVSM&feature=fvwrel 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 Center pivot Drip irrigation (efficiency 90–95%) (efficiency 80% with low-pressure sprinkler and 90–95% with LEPA sprinkler) Above- or below-ground (efficiency 60% and 80% with surge valves) pipes or tubes deliver water to individual plant roots. Water usually comes from an aqueduct system or a nearby river. Gravity flow Water usually pumped from underground and sprayed from mobile boom with sprinklers. Stepped Art Fig. 11-14, p. 251 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.
