DIHYDROGEN OXIDE!!!!

1. DIHYDROGEN OXIDE!!!! Read your info sheet

2. Sustainability • Make a list of things you want to see last beyond your lifetime.

3. These are the things you want to SUSTAIN throughout time.

4. Can you make some categories? • Environment • Social equity • Economic

5. Can you make a definition of sustainability?

6. Water! Miller Chapter 14

7. Water Resources • Water is a “renewable” but finite resource • Clean water is essential to human/animal health – humans can only live about 3 days without water

8. THIRST

9. “Water Planet” • About 70% of Earth’s surface is water • 97.5% of that is ocean water • 2.5% is fresh water • 1.5% is frozen in ice caps & glaciers • 0.5% is inaccessible/brackish • Only about 0.02% of the Earth’s water supply is available as liquid freshwater

10. “Water Planet”

11. Who is using Earth’s water resources? What 2 conclusions can you draw from this data?

12. Hydrological Cycle

13. Hydrological Cycle • Transpiration – from plants • Evaporation – from rivers, lakes, ponds, oceans • Precipitation – rain • Runoff – to rivers, lakes, etc • Infiltration/Seepage – to aquifers, groundwater, to rivers & oceans, to plants

14. Surface Water • Surface water is water that is above ground in lakes, rivers, ponds, and streams • A watershed is the entire area of land that is drained by a river

15. Unconfined Aquifer Recharge Area Evaporation and transpiration Evaporation Precipitation Confined Recharge Area Runoff Flowing artesian well Recharge Unconfined Aquifer Stream Well requiring a pump Water table Infiltration Lake Infiltration Unconfined aquifer Less permeable material such as clay Confined aquifer Confining impermeable rock layer Fig. 14-3, p. 308

16. Groundwater and Aquifers • Groundwater – water that seeps down into the soil and is stored underground • Aquifers – large amounts of water in underground rock formations • Ex. Edward’s Aquifer (TX)

17. Aquifers • Aquifers are running low – people are pumping too much out! • It can take millions of years to form • Recharge zone: area of land from which groundwater originates

18. Surface Water Uses • We currently use more than half of the world’s reliable runoff of surface water and could be using 70-90% by 2025. • About 70% of the water we withdraw from rivers, lakes, and aquifers is not returned to these sources. • Irrigation is the biggest user of water (70%), followed by industries (20%) and cities and residences (10%).

19. Stress on the World’s River Basins • Comparison of the amount of water available with the amount used by humans. Figure 14-6

20. Why is there a shortage?

22. Total Water Use

23. Freshwater Resources in the United States • 17 western states by 2025 could face intense conflict over scarce water needed for urban growth, irrigation, recreation and wildlife. Figure 14-5

24. Too little freshwater • About 41% of the world’s population lives in river basins that do not have enough freshwater. • Many parts of the world are experiencing: • Rivers running dry. • Lakes and seas shrinking. • Falling water tables from overpumped aquifers.

25. Too little freshwater • Cities are outbidding farmers for water supplies from rivers and aquifers. • Countries are importing grain as a way to reduce their water use. • More crops are being used to produce biofuels. • Our water options are: • Get more water from aquifers and rivers, desalinate ocean water, waste less water.

26. Withdrawing groundwater to increase supplies • Most aquifers are renewable resources unless water is removed faster than it is replenished or if they are contaminated. • Groundwater depletion is a growing problem mostly from irrigation. • At least one-fourth of the farms in India are being irrigated from overpumped aquifers.

27. Trade-Offs Withdrawing Groundwater Advantages Disadvantages Useful for drinking and irrigation Aquifer depletion from overpumping Sinking of land (subsidence) from overpumping Available year-round Exists almost everywhere Polluted aquifers for decades or centuries Renewable if not overpumped or contaminated Saltwater intrusion into drinking water supplies near coastal areas Reduced water flows into surface waters No evaporation losses Increased cost and contamination from deeper wells Cheaper to extract than most surface waters Fig. 14-7, p. 313

28. Groundwater Depletion: A Growing Problem • Areas of greatest aquifer depletion from groundwater overdraft in the continental U.S. Figure 14-8

29. Other Effects of Groundwater Overpumping • Groundwater overpumping can cause land to sink, and contaminate freshwater aquifers near coastal areas with saltwater.

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

31. Solutions Groundwater Depletion Prevention Control Raise price of water to discourage waste Waste less water Subsidize water conservation Ban new wells in aquifers near surface waters Tax water pumped from wells near surface waters Buy and retire groundwater withdrawal rights in critical areas Set and enforce minimum stream flow levels Do not grow water-intensive crops in dry areas Fig. 14-12, p. 316

32. Dams • Dams collect water and forms a reservoir (artificial lake) • Reservoir water is used for drinking, manufacturing, irrigation

33. Dams, Continued • Used for power and electricity • Dams also cause environmental problems: when built, dry land behind dam is now flooded (destroys existing ecosystem); ecosystems downstream are disrupted due to lack of water

34. 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

35. Powerlines Reservoir Dam Powerhouse Intake Turbine Fig. 14-13b, p. 317

36. The Colorado Basin – an Overtapped Resource • The Colorado River has so many dams and withdrawals that it often does not reach the ocean. • 14 major dams and reservoirs, and canals. • Water is mostly used in desert area of the U.S. • Provides electricity from hydroelectric plants for 30 million people (1/10th of the U.S. population).

37. The Colorado Basin – an Overtapped Resource • Lake Powell, is the second largest reservoir in the U.S. • It hosts one of the hydroelectric plants located on the Colorado River. Figure 14-15

38. The Colorado River Basin • The area drained by this basin is equal to more than one-twelfth of the land area of the lower 48 states. Figure 14-14

39. How Would You Vote? • Do the advantages of large dams outweigh their disadvantages? • a. No. Large dams inflict extensive environmental damage and humans must learn to meet their needs without them. • b. Yes. Dams are critical in providing water and electricity for people, especially in developing countries.

40. Case Study: 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. • 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.

41. 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.

42. Transferring water from one place to another • Transferring water can make unproductive areas more productive but can cause environmental harm. • Promotes investment, jobs and strong economy. • It encourages unsustainable use of water in areas water is not naturally supplied.

43. The Aral Sea Disaster • The Aral Sea was once the world’s fourth largest freshwater lake. Figure 14-17

44. The Aral Sea Disaster • Diverting water from the Aral Sea and its two feeder rivers mostly for irrigation has created a major ecological, economic, and health disaster. • About 85% of the wetlands have been eliminated and roughly 50% of the local bird and mammal species have disappeared. • Since 1961, the sea’s salinity has tripled and the water has dropped by 22 meters most likely causing 20 of the 24 native fish species to go extinct.

45. Solutions to water shortages • Removing salt from seawater by current methods is expensive and produces large amounts of salty wastewater that must be disposed of safely. • 2 Options to “desalt” the sea: • Distillation • Reverse osmosis

46. Distillation • Heating saltwater until it evaporates, leaves behind water in solid form. • Desert biomes use this method

47. Reverse Osmosis • uses high pressure to force saltwater through a membrane filter • salt cannot pass through

48. Other options • “Towing Water” - Transportation of icebergs • Problem: they melt too quickly; can’t get ashore

49. Other options • Seeding clouds with tiny particles of chemicals to increase rainfall • Huge bags filled with freshwater to dry coastal areas • All are unlikely to provide significant amounts of freshwater.

50. Increasing water supplies by wasting less water • We waste about two-thirds of the water we use, but we could cut this waste to 15%. • 65-70% of the water people use throughout the world is lost through evaporation, leaks, and other losses. • Water is underpriced through government subsidies. • The lack of government subsidies for improving the efficiency of water use contributes to water waste.