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21.2 Groundwater Problems

21.2 Groundwater Problems. These include pollution, salt, and draining too much. 21.2 Other Effects of Groundwater Overpumping. Sinkholes form when the roof of an underground cavern collapses after being drained of groundwater. Figure 14-10. 21.2 Groundwater Depletion: A Growing Problem.

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21.2 Groundwater Problems

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  1. 21.2 Groundwater Problems • These include pollution, salt, and draining too much.

  2. 21.2 Other Effects of Groundwater Overpumping • Sinkholes form when the roof of an underground cavern collapses after being drained of groundwater. Figure 14-10

  3. 21.2 Groundwater Depletion: A Growing Problem • Areas of greatest aquifer depletion from groundwater overdraft in the continental U.S. • The Ogallala, the world’s largest aquifer, is most of the red area in the center (Midwest). Figure 14-8

  4. 21.2 Ogallala Aquifer • This is the world’s largest known aquifer, and fuels agricultural regions in the U.S. It extends from South Dakota to Texas. It’s essentially a non-renewable aquifer from the last ice age with an extremely slow recharge rate. In some cases, water is pumped out 8 to 10 times faster than it is renewed. Northern states will still have ample supplies, but for the south it’s getting thinner. It is estimated that ¼ of the aquifer will be depleted by 2020.

  5. 21.1 Water Usage • Irrigation – watering crops • Industry – coolant (power plant) • Domestic and Municipal – drinking, sewage, bathwater, dishwater & laundry

  6. 21.1 Water Usage • Amount of water for which all people, animals and plants compete is < 1% • Industrial production increases water use • Mass of water used 1000x total production of minerals

  7. 21.1 Water Usage • Comparison of population sizes and shares of the world’s freshwater among the continents.

  8. 21.2 Water Supply: A US Example • Water supply at any point on the land surface depends on several factors in the hydrologic cycle, • including the rates of precipitation, evaporation, transpiration • stream flow • subsurface flow • Water budget • A model that balances the inputs, outputs, and storage of water in a system. • Precipitation - evaporation = runoff

  9. 21.2 Water Supply: A US Example • Amount of water vapor passing over the US every day ~ 152,000 million m3 • 10% falls as precipitation (66% of which is evaporated or transpired) • Only 34% enters surface or groundwater

  10. 21.2 Groundwater Use and Problems • ½ the people in the US use groundwater as a primary source of drinking water • 20% of water used • In many parts of the country withdrawal from wells exceeds natural inflow • Overdraft • Nonrenewable resource • Problems include damage to river basins and land subsidence

  11. Global Water Problems

  12. 21.10 Global Water Shortage Linked to Food Supply • Both surface water and groundwater are being stressed and depleted: • Groundwater in the United States, China, India, Pakistan, Mexico, and many other countries is being mined • used faster than it is being renewed • Large bodies of water—for example, the Aral Sea—are drying up. • Large rivers, including the Colorado in the US and the Yellow in China, do not deliver any water to the ocean in some seasons or years.

  13. 21.10 Global Water Shortage Linked to Food Supply • As human population grows there is growing concern that there won’t be sufficient water to grow the food to feed 8-9 billion people. • Food shortage linked to water resources a real possibility. • Water also linked to energy (fuel to pump) as energy cost goes up so does cost of food.

  14. 21.10 Global Water Shortage Linked to Food Supply • Solution • Control human population growth • Conserve and sustain water resources • Need to be proactive now before significant food shortages develop.

  15. 21.10 Impacts of Human Activities on Freshwater Systems • Dams, cities, farmlands, and filled-in wetlands alter and degrade freshwater habitats. • Dams, diversions and canals have fragmented about 40% of the world’s 237 large rivers. • Flood control levees and dikes alter and destroy aquatic habitats. • Cities and farmlands add pollutants and excess plant nutrients to streams and rivers. • Many inland wetlands have been drained or filled for agriculture or (sub)urban development.

  16. 21.10 Drinking Water Problems

  17. 21.10 Coliform Bacteria • The W.H.O. recommends there be zero colonies of bacteria per 100ml of drinking water and 200 colonies per 100ml of swimming water. The average human excretes 2 billion organisms per day (see how easily untreated sewage can contaminate water?).

  18. 21.10 Oxygen Demanding Wastes • These are organic wastes that can be decomposed by aerobic bacteria (causes lack of oxygen). Fish die as a result of a lack of oxygen.

  19. 21.10 Water-Soluble Inorganic Chemicals • These include acids, salts, mercury, and lead. They make water unfit to drink.

  20. 21.10 Organic Material • These include oil, gas, plastics, pesticides, and detergents.

  21. 21.10 Population Growth • Problems include over-drawing fresh water, pollution, and over-building so that water can’t seep into the ground.

  22. 21.10 Sharing Water Resources • There are water wars out west. California bought the water from the Colorado River, but Arizona wants it. Who owns it? The same thing is happening in Texas. More water rights are sold than the actual amount of water. How do you share water? This is a problem all over the world.

  23. 21.5 Water Management

  24. 21.5 Water Management • Management of water resources is a complex issue that will become more difficult as demand for water increases in the coming years. • Especially in areas like the Southwestern US and other semi arid regions

  25. 21.5 Dams and Reservoirs • Description: A dammed stream that can capture & store water from rain & melted snow. • Benefits: Hydroelectric power; provides water to towns; recreation; controls floods downstream • Problems: Reduces downstream flow; prevents water from reaching the sea (Colorado River) devastates fish life; reduces biodiversity.

  26. Provides water for year-round irrigation of cropland Flooded land destroys forests or cropland and displaces people Large losses of water through evaporation Provides water for drinking Downstream cropland and estuaries are deprived of nutrient-rich silt Reservoir is useful for recreation and fishing Risk of failure and devastating downstream flooding Can produce cheap electricity (hydropower) Downstream flooding is reduced Migration and spawning of some fish are disrupted Fig. 14-13a, p. 317

  27. Powerlines Reservoir Dam Powerhouse Intake Turbine

  28. 21.7 China’s Three Gorges Dam • There is a debate over whether the advantages of the world’s largest dam and reservoir will outweigh its disadvantages. (Opened June 2012) • The dam will be 2 kilometers long. • The electric output will be that of 18 large coal-burning or nuclear power plants. • It will facilitate ship travel reducing transportation costs. • Dam will displace 1.2 million people. • Dam is built over seismatic fault and already has small cracks.

  29. 21.7 Dam Removal • Some dams are being removed for ecological reasons and because they have outlived their usefulness. • In 1998 the U.S. Army Corps of Engineers announced that it would no longer build large dams and diversion projects in the U.S. • The Federal Energy Regulatory Commission has approved the removal of nearly 500 dams. • Removing dams can reestablish ecosystems, but can also re-release toxicants into the environment.

  30. 21.7 Removal of Dams • Trapped sediment behind dams must be dealt with in dam removal. • If released quickly it could damage downstream ecosystem and fill pools. • Slower release minimizes damage. • Matilija Dam in Ventura County cost $300,000 to build but 10 times that to remove. • Removing dams is simple in concept but involves complex problems relating to sediment and water.

  31. 21.2 Desalinization • Description: Removing salt from salt water • Benefits: Freshwater • Problems: Uses lots of energy; costs 3-5 times more money; what do we do with the salt?

  32. 21.5 Cloud Seeding

  33. 21.5 Harvesting Icebergs • Description: Towing massive icebergs to arid coastal areas (S. California; Saudi Arabia) • Benefits: freshwater • Problems: Technology not available; costs too high; raise temperatures around the earth.

  34. 21.5 Wasting Less Water in Agriculture • Sixty percent of the world’s irrigation water is currently wasted, but improved irrigation techniques could cut this waste to 5-20%. • Center-pivot, low pressure sprinklers sprays water directly onto crop. • It allows 80% of water to reach crop. • Has reduced depletion of Ogallala aquifer in Texas High Plains by 30%.

  35. 21.4 Agricultural Use • Suggestions for conservation: • Price agricultural water to encourage conservation • Use lined or covered canals that reduce seepage and evaporation. • Use computer monitoring and schedule release of water for maximum efficiency. • Integrate the use of surface water and groundwater to more effectively use the total resource.

  36. 21.4 Agricultural Use • Irrigate at times when evaporation is minimal, such as at night or in the early morning. • Use improved irrigation systems, such as sprinklers or drip irrigation, that more effectively apply water to crops. • Improve the soil to increase infiltration and minimize runoff. • Encourage the development of crops that require less water or are more salt tolerant.

  37. Drip irrigation (efficiency 90–95%) Gravity flow (efficiency 60% and 80% with surge valves) Center pivot (efficiency 80%–95%) Water usually pumped from underground and sprayed from mobile boom with sprinklers. Above- or below-ground pipes or tubes deliver water to individual plant roots. Water usually comes from an aqueduct system or a nearby river.

  38. 21.4 Water Conservation • The careful use and protection of water resources • Involves the quantity of water used and the quality • Important component of sustainable water use • Expected that a number innovations will reduce the total withdrawals

  39. 21.4 Conservation • Description: Saving the water we have • Methods: recycling; conserving at home; xeriscaping; fix leaks • Benefits: Saves money; Saves Wildlife • Problems: bothersome to people; lack of caring; laziness

  40. 21.4 Industry and Manufacturing Use • Water conservation measures that can be taken by industry: • Using cooling towers that use little or no water • In-plant water treatment and recycling

  41. 21.4 Perception and Water Use • Perception of water is based partly on its price and availability. • If water is abundant and inexpensive, we don’t think much about it. • If water is scarce or expensive, it is another matter. • E.g. people in Tucson pay about 100% more for water than people in Phoenix. • Tucson residence use less water per person per day

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