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ch10_Freshwater - Chapter 10 Freshwater Resources and Water...

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Unformatted text preview: Chapter 10 Freshwater Resources and Water Pollution Water The Importance of Water The All living things need water You are about 70% water by weight What do we use water for? Water on Earth Water About 97% Earth’s water is salty Fresh water is distributed unevenly 2025: 1/3 human population will live in areas lacking fresh water What can be done about this? Water is continuously cycling through the environment Ocean Hydrologic Cycle Hydrologic Atmosphere Land Ocean Hydrologic Cycle Precipitation Evaporation Surface Water Surface Streams, rivers, lakes, ponds, reservoirs, wetlands Runoff replenishes surface water Watershed Area of land drained by a single river Drainage basin Groundwater Groundwater Supply of fresh water found under Earth’s surface Stored in underground aquifers Discharged into rivers, springs, etc… Usually considered nonrenewable Properties of Water Properties Molecules of water 2 Hydrogens, 1 Oxygen H O 2 Polar One end slightly positive One end slightly negative Appears “bent” Properties of Water Hydrogen bonds Result of water’s polarity Basis for many of water’s properties High heat capacity Moderates climate Universal solvent Water Resource Problems Water Too much water Too little water Poor­quality water Flooding Flooding River’s discharge can’t be contained Floods more disastrous today: why? What can be done? Too Little Water Too Arid & semiarid lands Irrigation Needed to produce food Greatest use of water (71%) Aquifer Depletion Aquifer Removing groundwater faster than it is replenished Lowers water table Land subsidence Saltwater intrusion Salt water seeps into fresh water Coastal areas Ogallala Aquifer Ogallala World’s largest groundwater deposit Used for irrigation Being depleted 40 times faster than replacement Will become unusable: why? Overdrawing Surface Waters Overdrawing Damaging to ecosystems Wetlands dry up Estuaries become too salty Why are we removing so much water? Availability of surface waters may be a serious regional problem The Colorado River The Provides water to 25 million people Used for irrigation 49 dams Mexico has rights as well Lower Colorado becoming salty Some limits in effect today Salinization Salinization Salt accumulates in soil Result of irrigation: why? Can hurt productivity May render soils unfit for production How can problem be solved/helped? Global Water Issues Global Problems becoming more serious Many people lack safe drinking water and sewage systems Mexico City facing serious shortages Less water will be available in the future: why? Sharing Water Resources Sharing 1950s: Soviet Union diverts water for irrigation Aral Sea shrinks 1991: Soviet Union breaks up 5 countries working to help Aral Sea Sharing Water Resources Sharing Rhine River basin 5 different countries Was being polluted Collective efforts have improved the water Water Management Water Goal: sustainable supply of high quality water How do we supply water? Building dams Diversion Desalination Conservation Columbia River Columbia Fourth largest in N. America More than 100 dams Water used for Electrical generation Irrigation Industry & households Columbia River Dams Benefits Generate electricity Flood control Provide water Problem Bad for salmon What should be done? Water Conservation: Agriculture Water Single largest user of water worldwide Much lost to evaporation or seepage Solution: microirrigation Perforated pipes distribute water Goes straight to plants Reduces water use 40­60% Problem? Water Conservation: Industry Water Five industries consume 90% industrial water Strict pollution control laws have helped Many industries capture, purify and reuse water U. S. Steel recycles ~ 2/3 of its water Water Conservation: Municipal Water Avg. person in U.S. uses how much water per day? Use gray water Education Water­saving fixtures Repair leaks Other ideas? Water Conservation: Municipal Water Water Pollution Water Physical or chemical change in water that adversely affects the health of humans or other organisms Global problem Eight different categories Types of Water Pollution Pollution Sewage Sewage Wastewater from drains & sewers Wastes, soaps, detergents, etc… May cause disease Biochemical oxygen demand (BOD) Oxygen needed for microorganisms to decompose waste Lots of sewage = high BOD = less oxygen available Effect of Sewage on BOD Effect Eutrophication Enrichment of a body of water Eutrophic lake Increase of nutrients Cloudy water Oligotrophic lake Fewer nutrients Clear water Artificial eutrophication: causes? Eutrophic & Oligotrophic Lakes Eutrophic Sources of Water Pollution Sources Natural sources Human­generated Point source: specific source Nonpoint source Polluted runoff Enters over a large area Nonpoint Source Pollution Nonpoint Agriculture 72% of water pollution Fertilizers, pesticides, manure Soil erosion Urban runoff Variety of contaminants Groundwater Pollution Groundwater Groundwater provides ~ 1/2 of U.S. drinking water Most U.S. groundwater is safe Sources of pollution? Cleanup is costly! Groundwater Pollution Sources Groundwater Improving Water Quality Improving Contaminants are removed Drinking water purification Treat with chemical coagulant Suspended particles settle out Filter water through sand Disinfect Purifying Drinking Water Purifying Improving Water Quality Improving Municipal sewage treatment Primary treatment: remove suspended & floating particles Secondary treatment: decompose suspended organics Tertiary treatment: dissolved substances Sludge must be managed Municipal Sewage Treatment Municipal Municipal Sewage Treatment Arcata, California Constructed wetlands that aid in treatment Marshes absorb contaminants Provides wildlife habitat Controlling Water Pollution Controlling Safe Drinking Water Act Passed: 1974 Uniform standards for drinking water Maximum contaminant levels Suppliers must tell consumers what is in their water Controlling Water Pollution Clean Water Act Affects rivers, lakes, aquifers, estuaries, and costal waters 1972: Water Pollution Control Act 1977: amended and renamed Two goals Eliminate discharge of pollutants Safe water for humans and wildlife Has it been successful? U.S. Water Quality Today U.S. Clean Water Act has helped: point source pollution 2002 National Water Quality Inventory Some pollution has increased Many places too polluted for swimming, fishing or drinking Preventing Water Pollution At Home Pollution Water Pollution In Developing Countries Developing 1.4 billion people lack safe drinking water 2.9 billion people lack adequate sanitation Water for drinking polluted by human wastes, chemicals, human remains Case Study: The Great Lakes Case Provide drinking water for 38 million people Were highly polluted Toxic chemicals Eutrophication Fish kills common Case Study: The Great Lakes Case Canada & U.S. cooperate today $20 billion spent on cleanup since 1972 Many improvements DDT in breast milk declined PCBs in trout declined Some animal species rebounding Case Study: The Great Lakes Today’s problems Many invasive species Too much shoreline development Some persistent toxins remain Fish may contain high levels of toxins bioacumulation ...
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