1. Water Resources
Chapter 13

2. 13-1 Will We Have Enough Usable Water?
Concept 13-1A We are using available freshwater unsustainably by wasting it, polluting it, and charging too little for this irreplaceable natural resource.
Concept 13-1B One of every six people does not have sufficient access to clean water, and this situation will almost certainly get worse.

3. WATER’S IMPORTANCE, AVAILABILITY, AND RENEWAL
Water keeps us alive, moderates climate, sculpts the land, removes and dilutes wastes and pollutants, and moves continually through the hydrologic cycle.
Only about 0.02% of the earth’s water supply is available to us as liquid freshwater.

4. Girl Carrying Well Water over Dried Out Earth during a Severe Drought in India

5. WATER’S IMPORTANCE, AVAILABILITY, AND RENEWAL
Comparison of population sizes and shares of the world’s freshwater among the continents.

6. WATER’S IMPORTANCE, AVAILABILITY, AND RENEWAL
Some precipitation infiltrates the ground and is stored in soil and rock (groundwater).
Water that does not sink into the ground or evaporate into the air runs off (surface runoff) into bodies of water.
The land from which the surface water drains into a body of water is called its watershed or drainage basin.

7. Flowing artesian well Well requiring a pump Water table
Unconfined Aquifer Recharge Area
Evaporation and transpiration
Evaporation
Precipitation
Confined Recharge Area
Runoff
Flowing artesian well
Well requiring a pump
Stream
Figure 13.3
Natural capital: groundwater system. An unconfined aquifer is an aquifer with a permeable water table. A confined aquifer is bounded above and below by less permeable beds of rock, and its water is confined under pressure. Some aquifers are replenished by precipitation; others are not.
Water table
Infiltration
Lake
Infiltration
Unconfined aquifer
Less permeable material such as clay
Confined aquifer
Confining impermeable rock layer
Fig. 13-3, p. 316

8. WATER’S IMPORTANCE, AVAILABILITY, AND RENEWAL
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%).

9. Average Annual Precipitation and Major Rivers, Water-Deficit Regions in U.S.
Fig 13-4

10. Water Hot Spots Washington North Dakota Montana Oregon Idaho
South Dakota
Wyoming
Nevada
Nebraska
Utah
Colorado
Kansas
California
Oklahoma
New Mexico
Arizona
Figure 13.5
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 during the next 25 years. Question: If you live in one of these hotspot areas, have you noticed any signs of conflict over water supplies? (Data from U.S. Department of the Interior)
Texas
Highly likely conflict potential
Substantial conflict potential
Moderate conflict potential
Unmet rural water needs
Fig. 13-5, p. 318

11. Asia Europe North America Africa South America Australia Stress High
Figure 13.6
Natural capital degradation: stress on the world’s major river basins, based on a comparison of the amount of water available with the amount used by humans (Concept 13-1B). Questions: If you live in a water-stressed area, what signs of stress have you noticed? In what ways, if any, has it affected your life? (Data from World Commission on Water Use in the 21st Century)
Stress
High
None
Fig. 13-6, p. 319

12. Long-Term Severe Drought Is Increasing
Causes
Extended period of below-normal rainfall
Diminished groundwater
Harmful environmental effects
Dries out soils
Reduces stream flows
Decreases tree growth and biomass
Lowers net primary productivity and crop yields
Shift in biomes

13. Case Study: Who Should Own and Manage Freshwater Resources
There is controversy over whether water supplies should be owned and managed by governments or by private corporations.
European-based water companies aim to control 70% of the U.S. water supply by buying up water companies and entering into agreements with cities to manage water supplies.

14. 13-2 Is Extracting Groundwater the Answer?
Concept Groundwater that is used to supply cities and grow food is being pumped from aquifers in some areas faster than it is renewed by precipitation.

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

16. TRADE-OFFS Withdrawing Groundwater Advantages Disadvantages
Useful for drinking and irrigation
Aquifer depletion from overpumping
Sinking of land (subsidence) from overpumping
Available year-round
Aquifers polluted for decades or centuries
Exists almost everywhere
Saltwater intrusion into drinking water supplies near coastal areas
Renewable if not overpumped or contaminated
Figure 13.7
Advantages and disadvantages of withdrawing groundwater. Question: Which two advantages and which two disadvantages do you think are the most important? Why?
Reduced water flows into surface waters
No evaporation losses
Increased cost and contamination from deeper wells
Cheaper to extract than most surface waters
Fig. 13-7, p. 321

17. Natural Capital Degradation: Irrigation in Saudi Arabia Using an Aquifer

18. Natural Capital Degradation: Areas of Greatest Aquifer Depletion in the U.S.
Fig 13-9

19. 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
Figure 13.11
Ways to prevent or slow groundwater depletion by using water more sustainably. Question: Which two of these solutions do you think are the most important? Why?
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 , p. 324

20. 13-3 Is Building More Dams the Answer?
Concept 13-3 Building dam and reservoir systems has greatly increased water supplies in some areas, but it has disrupted ecosystems and displaced people.

21. Large Dams and Reservoirs Have Advantages and Disadvantages (1)
Main goals of a dam and reservoir system
Capture and store runoff
Release runoff as needed to control:
Floods
Generate electricity
Supply irrigation water
Recreation (reservoirs)

22. Large Dams and Reservoirs Have Advantages and Disadvantages (2)
Increase the reliable runoff available
Reduce flooding
Grow crops in arid regions

23. Large Dams and Reservoirs Have Advantages and Disadvantages (3)
Displaces people
Flooded regions
Impaired ecological services of rivers
Loss of plant and animal species
Fill up with sediment within 50 years

24. Advantages and Disadvantages of Large Dams and Reservoirs
Fig 13-12

25. Matilija Dam Removal Project
Click for report

26. The Colorado River Basin
Fig 13-14

27. Case Study: The Colorado River Basin— An Overtapped Resource (3)
Four Major problems
Colorado River basin has very dry lands
Modest flow of water for its size
Legal pacts allocated more water for human use than it can supply
Amount of water flowing to the mouth of the river has dropped

28. Aerial View of Glen Canyon Dam Across the Colorado River and Lake Powell

29. The Flow of the Colorado River Measured at Its Mouth Has Dropped Sharply

30. Case Study: China’s Three Gorges Dam (1)
World’s largest hydroelectric dam and reservoir
2 km long across the Yangtze River
Benefits
Electricity-producing potential is huge (18 large power plants)
Holds back the Yangtze River floodwaters
Allows cargo-carrying ships

31. Case Study: China’s Three Gorges Dam (2)
Harmful effects
Displaces about 5.4 million people
Built over a seismic fault
Significance?
Rotting plant and animal matter producing CH4
Worse than CO2 emissions
Will the Yangtze River become a sewer?

32. 13-4 Is Transferring Water from One Place to Another the Answer?
Concept Transferring water from one place to another has greatly increased water supplies in some areas, but it has also disrupted ecosystems.

33. Oroville Dam and Reservoir
CALIFORNIA
Shasta Lake
NEVADA
UTAH
Sacramento River
Oroville Dam and Reservoir
Feather River
North Bay Aqueduct
Lake Tahoe
Sacramento
San Francisco
Hoover Dam and Reservoir (Lake Mead)
South Bay Aqueduct
Fresno
San Luis Dam and Reservoir
San Joaquin Valley
Colorado River
Los Angeles Aqueduct
California Aqueduct
ARIZONA
Colorado River Aqueduct
Santa Barbara
Figure 13.17
The California Water Project and the Central Arizona Project. These projects involve large-scale water transfers from one watershed to another. Arrows show the general direction of water flow.
Central Arizona Project
Los Angeles
Phoenix
Salton Sea
San Diego
Tucson
MEXICO
Fig , p. 330

34. Natural Capital Degradation: The Aral Sea, Shrinking Freshwater Lake
1976
2006

35. Oxnard water suppliers
United Water
Calleguas Municipal
City of Oxnard

36. 13-5 Is Converting Salty Seawater to Freshwater the Answer?
Concept 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.

37. 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
Click for link to Desal Response Group

38. 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
Click for Oxnard’s GREAT RO plant info

39. 13-6 How Can We Use Water More Sustainably?
Concept 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.

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

41. (efficiency 60% and 80% with surge valves)
Center pivot
(efficiency 80% with low-pressure sprinkler and 90–95% with LEPA sprinkler)
Water usually pumped from underground and sprayed from mobile boom with sprinklers.
Drip irrigation
(efficiency 90–95%)
Above- or below-ground pipes or tubes deliver water to individual plant roots.
Gravity flow
(efficiency 60% and 80% with surge valves)
Water usually comes from an aqueduct system or a nearby river.
Figure 13.20
Major irrigation systems. Because of high initial costs, center-pivot irrigation and drip irrigation are not widely used. The development of new, low-cost, drip-irrigation systems may change this situation.
Stepped Art
Fig , p. 335

42. Solutions: Reducing Irrigation Water Waste
Fig 13-21

43. Solutions: Reducing Water Waste
Fig 13-22

44. 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
Figure 13.23
Methods for achieving more sustainable use of the earth’s water resources (Concept 13-6). Question: Which two of these solutions do you think are the most important? Why?
Get agreements among regions and countries sharing surface water resources
Raise water prices
Slow population growth
Fig , p. 337

45. How can you save water at home?
Click for Family Water Audit

46. What Can You Do? Water Use and Waste
Fig 13-24

47. 13-7 How Can We Reduce the Threat of Flooding?
Concept 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.

48. 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

49. 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

50. Natural Capital Degradation: Hillside Before and After Deforestation
Fig 13-25

51. 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
Figure 13.26
Methods for reducing the harmful effects of flooding (Concept 13-7). Question: Which two of these solutions do you think are the most important? Why?
Use floodplains primarily for recharging aquifers, sustainable agriculture and forestry
Build dams
Fig , p. 340