Water Resources – PART 2

1. Water Resources – PART 2 Chapter 13

2. 13-4 Is Transferring Water from One Place to Another the Answer? • Concept 13-4 Transferring water from one place to another has greatly increased water supplies in some areas, but it has also disrupted ecosystems.

3. CA, U.S., Transfers Water from Water-Rich Areas to Water-Poor Areas • Water transferred by • Tunnels • Aqueducts • Underground pipes • May cause environmental problems • California Water Project

4. CALIFORNIA NEVADA Shasta Lake UTAH Sacramento River Oroville Dam and Reservoir Feather River Lake Tahoe North Bay Aqueduct Sacramento San Francisco Hoover Dam and Reservoir (Lake Mead) South Bay Aqueduct Fresno San Joaquin Valley San Luis Dam and Reservoir Colorado River Los Angeles Aqueduct California Aqueduct ARIZONA Colorado River Aqueduct Santa Barbara Central Arizona Project Los Angeles Phoenix Salton Sea San Diego Tucson MEXICO Fig. 13-17, p. 330

5. Case Study: The Aral Sea Disaster (1) • Large-scale water transfers in dry central Asia • Salinity • Wetland destruction and wildlife • Fish extinctions and fishing

6. Case Study: The Aral Sea Disaster (2) • Wind-blown salt • Water pollution • Climatic changes • Restoration efforts

7. 1976 2006 Stepped Art Fig. 13-18a, p. 331

8. Ship Stranded in Desert Formed by Shrinkage of the Aral Sea

9. China Plans a Massive Transfer of Water • South-North Water Transfer Project • Water from three rivers to supply 0.5 billion people • Completion in about 2050 • Impact • Economic • Health • Environmental

10. 13-5 Is Converting Salty Seawater to Freshwater the Answer? • Concept 13-5 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.

11. Removing Salt from Seawater Seems Promising but Is Costly (1) • Desalination • Distillation • Reverse osmosis, microfiltration • 15,000 plants in 125 countries • Saudi Arabia: highest number

12. Removing Salt from Seawater Seems Promising but Is Costly (2) • Problems • High cost and energy footprint • Keeps down algal growth and kills many marine organisms • Large quantity of brine wastes • Future economics

13. Science Focus: The Search for Improved Desalination Technology • Desalination on offshore ships • Solar or wind energy • Better membranes • Better disposal options for the brine waste • Reduce water needs, conserve water

14. 13-6 How Can We Use Water More Sustainably? • Concept 13-6 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.

15. Reducing Water Waste Has Many Benefits (1) • Water conservation • Improves irrigation efficiency • Improves collection efficiency • Uses less in homes and businesses

16. Reducing Water Waste Has Many Benefits (2) • Worldwide: 65–70% loss • Evaporation, leaks, etc. • Water prices: low cost to user • Government subsidies: more needed?

17. We Can Cut Water Waste in Irrigation • Flood irrigation • Wasteful • Center pivot, low pressure sprinkler • Low-energy, precision application sprinklers • Drip or trickle irrigation, microirrigation • Costly; less water waste

18. Center pivot (efficiency 80% with low-pressure sprinkler and 90–95% with LEPA sprinkler) Drip irrigation (efficiency 90–95%) Water usually pumped from underground and sprayed from mobile boom with sprinklers. Gravity flow (efficiency 60% and 80% with surge valves) Above- or below-ground pipes or tubes deliver water to individual plant roots. Water usually comes from an aqueduct system or a nearby river. Fig. 13-20, p. 335

19. Solutions: Reducing Irrigation Water Waste

20. Developing Countries Use Low-Tech Methods for Irrigation • Human-powered treadle pumps • Harvest and store rainwater • Create a canopy over crops: reduces evaporation • Fog-catcher nets

21. We Can Cut Water Waste in Industry and Homes • Recycle water in industry • Fix leaks in the plumbing systems • Use water-thrifty landscaping: xeriscaping • Use gray water • Pay-as-you-go water use

22. Solutions: Reducing Water Waste

23. We Can Use Less Water to Remove Wastes • Can we mimic how nature deals with waste? • Waterless composting toilets

24. We Need to Use Water More Sustainably • “The frog does not drink up the pond in which it lives” • Blue revolution

25. Solutions: Sustainable Water Use

26. 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. 13-23, p. 337

27. What Can You Do? Water Use and Waste

28. 13-7 How Can We Reduce the Threat of Flooding? • Concept 13-7 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.

29. Some Areas Get Too Much Water from Flooding (1) • Flood plains • Highly productive wetlands • Provide natural flood and erosion control • Maintain high water quality • Recharge groundwater • Benefits of floodplains • Fertile soils • Nearby rivers for use and recreation • Flatlands for urbanization and farming

30. Some Areas Get Too Much Water from Flooding (2) • Dangers of floodplains and floods • Deadly and destructive • Human activities worsen floods • Failing dams and water diversion • Hurricane Katrina and the Gulf Coast • Removal of coastal wetlands

31. Natural Capital Degradation: Hillside Before and After Deforestation

32. Oxygen released by vegetation Diverse ecological habitat Evapotranspiration Trees reduce soil erosion from heavy rain and wind Agricultural land Tree roots stabilize soil Vegetation releases water slowly and reduces flooding Forested Hillside Fig. 13-25a, p. 339

33. Tree plantation Evapotranspiration decreases Roads destabilize hillsides 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 Silt from erosion fills rivers and reservoirs Rapid runoff causes flooding After Deforestation Fig. 13-25b, p. 339

34. Oxygen released by vegetation Tree plantation Diverse ecological habitat Evapotranspiration decreases Evapotranspiration Roads destabilize hillsides Trees reduce soil erosion from heavy rain and wind Overgrazing accelerates soil erosion by water and wind Winds remove fragile topsoil Agricultural land Agricultural land is flooded and silted up Gullies and landslides Tree roots stabilize soil Heavy rain erodes topsoil Vegetation releases water slowly and reduces flooding Silt from erosion fills rivers and reservoirs Rapid runoff causes flooding Forested Hillside After Deforestation Stepped Art Fig. 13-25a, p. 339

35. Case Study: Living Dangerously on Floodplains in Bangladesh • Dense population • Located on coastal floodplain • Moderate floods maintain fertile soil • Increased frequency of large floods • Effects of development in the Himalayan foothills • Destruction of coastal wetlands

36. We Can Reduce Flood Risks • Rely more on nature’s systems • Wetlands • Natural vegetation in watersheds • Rely less on engineering devices • Dams • Levees

37. SOLUTIONS Reducing Flood Damage Prevention Control Preserve forests on watersheds Straighten and deepen streams (channelization) Preserve and restore wetlands in floodplains Build levees or floodwalls along streams Tax development on floodplains Use floodplains primarily for recharging aquifers, sustainable agriculture and forestry Build dams Fig. 13-26, p. 340

38. Active Figure: Effects of deforestation