1. Chapter 15
Water Resources

2. Chapter Overview Questions
Why is water so important, how much freshwater is available to us, and how much of it are we using?
What causes freshwater shortages, and what can be done about this problem?
What are the advantages and disadvantages of withdrawing groundwater?
What are the advantages and disadvantages of using dams and reservoirs to supply more water?

3. Chapter Overview Questions (cont’d)
What are the advantages and disadvantages of transferring large amounts of water from one place to another?
Can removing salt from seawater solve our water supply problems?
How can we waste less water?
How can we use the earth’s water more sustainably?
What causes flooding, and what can we do about it?

4. Core Case Study: Water Conflicts in the Middle East - A Preview of the Future
Many countries in the Middle East, which has one of the world’s highest population growth rates, face water shortages.

5. Water Conflicts in the Middle East: A Preview of the Future
Most water in this dry region comes from the Nile, Jordan or Tigris rivers.
Countries are in disagreement as to who has water rights.
Currently, there are no cooperative agreements for use of 158 of the world’s 263 water basins that are shared by two or more countries.

6. 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.

7. Water Supply & Use

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

9. 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.

10. Unconfined Aquifer Recharge Area Evaporation and transpiration
Precipitation
Evaporation and transpiration
Evaporation
Confined Recharge Area
Runoff
Flowing artesian well
Recharge Unconfined Aquifer
Stream Well requiring a pump
Figure 14.3
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 where the water is confined under pressure. Some aquifers are replenished by precipitation; others are not.
Infiltration
Water table
Lake
Infiltration
Unconfined aquifer
Less permeable material such as clay
Confined aquifer
Confining impermeable rock layer

11. 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%).

12. Water in the United States
Average precipitation (top) in relation to water-deficit regions and their proximity to metropolitan areas (bottom).

13. Average annual precipitation (centimeters)
Less than 41
81–122
41–81
More than 122
Figure 14.4
Natural capital: average annual precipitation and major rivers (top) and water-deficit regions in the continental United States and their proximity to metropolitan areas having populations greater than 1 million (bottom). QUESTION: What is the water supply situation where you live or go to school? (Data from U.S. Water Resources Council and U.S. Geological Survey)

14. Metropolitan regions with population greater than 1 million
Figure 14.4
Natural capital: average annual precipitation and major rivers (top) and water-deficit regions in the continental United States and their proximity to metropolitan areas having populations greater than 1 million (bottom). QUESTION: What is the water supply situation where you live or go to school? (Data from U.S. Water Resources Council and U.S. Geological Survey)
Acute shortage
Shortage
Adequate supply
Metropolitan regions with population greater than 1 million

15. Case Study: 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.

16. 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.

17. Stress on the World’s River Basins
Comparison of the amount of water available with the amount used by humans.
LAKE CHAD

18. 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.

19. How Would You Vote?
Should private companies own or manage most of the world's water resources?
a. No. Democratically elected governments, which are accountable to the voters, should own and manage water resources.
b. Qualified yes. Governments should own the water, but expert private companies should manage it.
c. Depends. Each case must be decided independently. The record on private versus public ownership is mixed.
d. Yes. Private companies have more expertise and experience in managing water resources than most government bureaucrats.

20. 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.

21. 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.

22. Withdrawing Groundwater
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
Figure 14.7
Trade-offs: advantages and disadvantages of withdrawing groundwater. QUESTION: Which two advantages and which two disadvantages do you think are the most important?
No evaporation losses
Reduced water flows into surface waters
Increased cost and contamination from deeper wells
Cheaper to extract than most surface waters

23. 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).

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

25. Other Effects of Groundwater Overpumping
Sinkholes form when the roof of an underground cavern collapses after being drained of groundwater.

26. Groundwater Depletion
Solutions
Groundwater Depletion
Prevention
Control
Waste less water
Raise price of water to discourage waste
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
Figure 14.12
Solutions: 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?
Set and enforce minimum stream flow levels
Do not grow water-intensive crops in dry areas

27. USING DAMS AND RESERVOIRS TO SUPPLY MORE WATER
Large dams and reservoirs can produce cheap electricity, reduce downstream flooding, and provide year-round water for irrigating cropland, but they also displace people and disrupt aquatic systems.

28. 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)
Figure 14.13
Trade-offs: advantages (green) and disadvantages (orange) of large dams and reservoirs. The world’s 45,000 large dams (higher than 15 meters or 50 feet) capture and store 14% of the world’s runoff, provide water for almost half of all irrigated cropland, and supply more than half the electricity used by 65 countries. The United States has more than 70,000 large and small dams, capable of capturing and storing half of the country’s entire river flow. QUESTION: Which single advantage and which single disadvantage do you think are the most important?
Downstream flooding is reduced
Migration and spawning of some fish are disrupted

29. Powerlines Reservoir Dam Powerhouse Intake Turbine Figure 14.13
Trade-offs: advantages (green) and disadvantages (orange) of large dams and reservoirs. The world’s 45,000 large dams (higher than 15 meters or 50 feet) capture and store 14% of the world’s runoff, provide water for almost half of all irrigated cropland, and supply more than half the electricity used by 65 countries. The United States has more than 70,000 large and small dams, capable of capturing and storing half of the country’s entire river flow. QUESTION: Which single advantage and which single disadvantage do you think are the most important?

30. Case Study: 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).

31. Case Study: 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.

32. 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.

33. 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.

34. 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.

35. 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.

36. Case Study: The California Experience
A massive transfer of water from water-rich northern California to water-poor southern California is controversial.

37. Case Study: The Aral Sea Disaster
The Aral Sea was once the world’s fourth largest freshwater lake.

38. Case Study: 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.

39. DESALTING SEAWATER, SEEDING CLOUDS, AND TOWING ICEBERGS AND GIANT BAGGIES
Removing salt from seawater by current methods is expensive and produces large amounts of salty wastewater that must be disposed of safely.
Distillation: heating saltwater until it evaporates, leaves behind water in solid form.
Reverse osmosis: uses high pressure to force saltwater through a membrane filter.

40. DESALTING SEAWATER, SEEDING CLOUDS, AND TOWING ICEBERGS AND GIANT BAGGIES
Seeding clouds with tiny particles of chemicals to increase rainfall towing icebergs or huge bags filled with freshwater to dry coastal areas have all been proposed but are unlikely to provide significant amounts of freshwater.

41. 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.

42. How Would You Vote?
Should water prices be raised sharply to help reduce water waste?
a. No. Poor people, farmers, ranchers, and small businesses would suffer from price increases.
b. Yes. People would be more likely to conserve water if it is more expensive.

43. INCREASING WATER SUPPLIES BY WASTING LESS WATER
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%.

44. (efficiency 60% and 80% with surge valves)
Drip irrigation
(efficiency 90–95%)
Gravity flow
(efficiency 60% and 80% with surge valves)
Figure 14.18
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.
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.

45. Reducing Irrigation Water Waste
Solutions
Reducing Irrigation Water Waste
• Line canals bringing water to irrigation ditches
• Level fields with lasers
• Irrigate at night to reduce evaporation
• Monitor soil moisture to add water only when necessary
• Polyculture
• Organic farming
Figure 14.19
Solutions: methods for reducing water waste in irrigation. QUESTION: Which two of these solutions do you think are the most important?
• Don't grow water-thirsty crops in dry areas
• Grow water-efficient crops using drought resistant and salt-tolerant crop varieties
• Irrigate with treated urban waste water
• Import water-intensive crops and meat

46. Solutions: Getting More Water for Irrigation in Developing Countries – The Low-Tech Approach
Many poor farmers in developing countries use low-tech methods to pump groundwater and make more efficient use of rainfall.

47. Solutions Reducing Water Waste • Redesign manufacturing processes
• Repair leaking underground pipes
• Landscape yards with plants that require little water
• Use drip irrigation
• Fix water leaks
• Use water meters
• Raise water prices
• Use waterless composting toilets
• Require water conservation in water-short cities
Figure 14.21
Solutions: methods of reducing water waste in industries, homes, and businesses. QUESTION: Which three of these solutions do you think are the most important?
• Use water-saving toilets, showerheads, and front loading clothes washers
• Collect and reuse household water to irrigate lawns and nonedible plants
• Purify and reuse water for houses, apartments, and office buildings
• Don't waste energy

48. Raising the Price of Water: A Key to Water Conservation
We can reduce water use and waste by raising the price of water while providing low lifeline rates for the poor.
When Boulder, Colorado introduced water meters, water use per person dropped by 40%.
A 10% increase in water prices cuts domestic water use by 3-7%.

49. Solutions: Using Less Water to Remove Industrial and Household Wastes
We can mimic the way nature deals with wastes instead of using large amounts of high-quality water to wash away and dilute industrial and animal wastes.
Use nutrients in wastewater before treatment as soil fertilizer.
Use waterless and odorless composting toilets that convert human fecal matter into a small amount of soil material.

50. SOLUTIONS: USING WATER MORE SUSTAINABLY
We can use water more sustainably by cutting waste, raising water prices, preserving forests and wetlands in water basins, and slowing population growth.

51. What Can You Do? Water Use and Waste
• Use water-saving toilets, showerheads, and faucet aerators.
• Shower instead of taking baths, and take short showers.
• Stop water leaks.
• Turn off sink faucets while brushing teeth, shaving, or washing.
• Flush toilets only when necessary.
• Wash only full loads of clothes or use the lowest water-level for smaller loads.
• Use recycled (gray) water for lawn, gardens, house plants, car washing.
• Wash a car from a bucket of soapy water, and use the hose for rinsing only.
Figure 14.25
Individuals matter: ways you can reduce your use and waste of water. Visit for an array of water-saving tips from the EPA and the California Urban Water Conservation Council that can be used anywhere. QUESTION: Which four of these actions do you think are the most important?
• If you use a commercial car wash, try to find one that recycles its water.
• Replace your lawn with native plants that need little if any watering and decorative gravel or rocks.
• Water lawns and gardens in the early morning or evening.
• Sweep or blow off driveways instead of hosing off with water.
• Use drip irrigation and mulch for gardens and flowerbeds.