1. Chapter 13
Water Resources

2. Will We Have Enough Usable Water?

3. FRESHWATER 71% of Earth’s surface is either liquid or frozen H2O
Water accounts for 60-90% of the total body mass of living organisms
Freshwater is our most important resource & our most poorly managed one (waste & pollution)
Freshwater only accounts for about 3% of all the surface (or slightly subsurface) water on the planet
While most marine animals have body structures to deal with excess salt accumulation, no one is really sure how marine mammals handle this

4. Girl Carrying Well Water Over Dried Out Earth During a Severe Drought in India
ACCESS TO WATER IS:
A global health issue ~3900 children under age 5 die each day from waterborne diseases
An economic/women’s and children’s issue: water is vital for producing food & energy which reduces poverty; lack of available water requires that women and girls spend 4-6 hours a day and walk an average of 4 miles to collect it
A national and global security issue: increasing tensions within and between nations over access to limited water resources they share

5. Most of the Earth’s Freshwater Is Not Available to Us
So, if ALL precipitation is freshwater, why is just 3% of the surface water fresh?
Freshwater availability: 0.024%
Groundwater, lakes, rivers, streams
Hydrologic cycle provides a constant supply of freshwater in the form of precipitation
Movement of water in the seas, land, and air
Driven by solar energy and gravity
People divided into
Water haves: Canada (0.5% of world’s population; 20% of the available freshwater)
Water have-nots: China (19% of the people; 7% of the water) Asia (60% of the people; 30% of the water)

6. Hydrologic Cycle Figure 3.16: Natural capital.
This diagram is a simplified model of the water cycle, or hydrologic cycle, in which water circulates in various physical forms within the biosphere. Major harmful impacts of human activities are shown by the red arrows and boxes. Question: What are three ways in which your lifestyle directly or indirectly affects the hydrologic cycle?
Fig. 3-16, p. 67

7. Groundwater Terminology
Water in the spaces between soil, gravel and rock
Percolation
The movement of water from the surface into the ground
Zone of saturation
Area below ground where substrate is completely filled with water
Water table
Top of zone of saturation (fluctuates with wet and dry seasons)
Aquifers
Geological layers below the zone of saturation; typically caverns & underground lakes that hold water
Enclosed in watertight zones of solid rock or clay that keep the water from moving deeper
Natural recharge-precipitation falls directly over the area above the aquifer, percolates downward & is collected in aquifer
Lateral recharge-water moves sideways into the aquifer from nearby streams, rivers or lakes

8. Surface Water Terminology
Freshwater from precipitation and snow melt that flows across earth’s surface into rivers, lakes, streams, marshes, estuaries, wetlands and, ultimately, the ocean
Our most important freshwater resource
Surface runoff
Precipitation that does not evaporate or percolate
Watershed/Drainage Basin
Area of land from which surface runoff drains into a body of water
Much of this land is often designated as a flood plain
Example: Colorado River Basin

9. Colorado River Basin

10. We Use Much of the World’s Reliable Runoff
2/3 of the surface runoff: lost to larger bodies of water further away from the area where the rain fell due to seasonal floods
1/3 is usable (reliable runoff): collects locally in bodies of water such as lakes, ponds, streams
World-wide freshwater use averages
Domestic: 10%
Agriculture: 70%
Industrial use: 20%

11. Water Footprints and Virtual Water
Volume of water we use directly and indirectly
Average American uses 260 liters per day
Flushing toilets, 27%
Washing clothes, 22%
Taking showers, 17%
Running faucets, 16%
Wasted from leaks, 14%
World’s poorest use 19 liters per day
More water is used indirectly (virtual water)
Hamburger, 2400 liters
Virtual water often exported/imported
Grains and other foods

12. EXAMPLES OF VIRTUAL WATER USE

13. Freshwater Resources in the United States
More than enough renewable freshwater but
it is unevenly distributed and often polluted
Freshwater Resources in the United States
Eastern States have ample precipitation
Most of the freshwater is used for power plant cooling & manufacturing
Most serious water problems are flooding, occasional water shortages from pollution & drought
Western States are arid (having little to no rain) or semi-arid
Irrigation accounts for almost 85% of the water used
Most serious water problems are a shortage of runoff from reduced precipitation, high evaporation and recurring prolonged drought

14. Average Annual Precipitation and Major Rivers, Water-Deficit Regions in U.S.
Figure 13.4: The top map shows the average annual precipitation and major rivers in the continental United States. The bottom map shows water-deficit regions in the continental United States and their proximity to metropolitan areas having populations greater than 1 million (shaded areas). Question: Why do you think some areas with moderate precipitation still suffer from water shortages? (Data from U.S. Water Resources Council and U.S. Geological Survey)
Fig. 13-4, p. 322

15. Water Hotspots in 17 Western U.S. States
Figure 13.5: This map shows water scarcity 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 in the foreseeable future. Question: Which, if any, of these areas are found in the Colorado River basin (Figure 13-1)? (Data from U.S. Department of the Interior)
Fig. 13-5, p. 322

16. Natural Capital Degradation: Stress on the World’s Major River Basins
Figure 13.6: Natural capital degradation.
The world’s major river basins differ in their degree of water scarcity stress, the measurement of which is 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)
Fig. 13-6, p. 323

17. Extracting Groundwater

18. Trade-Offs: Withdrawing Groundwater, Advantages and Disadvantages
Figure 13.7: Withdrawing groundwater from aquifers has advantages and disadvantages. Questions: Which two advantages and which two disadvantages do you think are the most important? Why?
Fig. 13-7, p. 325

19. Aquifer Depletion in the United States
Ogallala aquifer: second largest known aquifer
Irrigates the Great Plains
Very slow recharge
Water table dropping
Government subsidies to continue farming deplete the aquifer further
Biodiversity threatened in some areas
California Central Valley: serious water depletion

20. Natural Capital Degradation: Areas of Greatest Aquifer Depletion in the U.S.
Figure 13.9: Natural capital degradation.
This map shows areas of greatest aquifer depletion from groundwater overdraft in the continental United States. Aquifer depletion is also high in Hawaii and Puerto Rico (not shown on map). See an animation based on this figure at CengageNOW. Questions: Do you depend on any of these overdrawn aquifers for your drinking water? If so, what is the level of severity of overdraft where you live? (Data from U.S. Water Resources Council and U.S. Geological Survey)
Fig. 13-9, p. 326

21. Deep Aquifers: Future Water Supply?
The Ogallala Aquifer is between 50 and 300 feet below the surface.
Deep aquifers are anywhere from miles below the surface (5280 ft = 1mile)
May contain enough water to provide for billions of people for centuries
Major concerns
Nonrenewable
Little is known about the geological and ecological impacts of pumping deep aquifers
Some flow beneath more than one country
Costs of tapping are unknown and likely quite high

22. Building More Dams

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

24. Large Dams and Reservoirs: Advantages and Disadvantages
Increase the reliable runoff available
Reduce flooding
Grow crops in arid regions
Displaces people
Flooded regions
Impaired ecological services of rivers
Loss of plant and animal species
Fill up with sediment
Can cause other streams and lakes to dry up

25. Transferring Water From One Place to Another

26. California Transfers Water from Water-Rich Areas to Water-Poor Areas
Water transferred from north to south by
Tunnels
Aqueducts
Underground pipes
California Water Project: One of the World’s Largest Water Transfer Projects
Inefficient water use
Environmental damage to Sacramento River and San Francisco Bay

27. Southern California Lettuce Grown with Northern California Water
Figure 13.15: This lettuce crop is growing in the Imperial Valley of central California. This and other water-intensive crops are grown in this arid area mostly because of the availability of cheap, government-subsidized irrigation water brought in from northern California, but also because the weather allows for growing crops year round in this valley. Question: Have you ever checked to see where your lettuce and other produce that you eat come from?
Fig , p. 331

28. The California Water Project and the Central Arizona Project
Figure 13.16: The California Water Project and the Central Arizona Project transfer huge volumes of water from one watershed to another. The red arrows show the general direction of water flow. Questions: What effects might this system have on different areas on this map? How might it affect areas from which the water is taken?
Fig , p. 331

29. Converting Seawater to Freshwater

30. Removing Salt from Seawater Is Costly, Kills Organisms & Creates Briny Wastewater
Desalination
Removing dissolved salts
Distillation: evaporate water, leaving salts behind
Reverse osmosis, microfiltration: use high pressure to remove salts
14,450 plants in 125 countries
Saudi Arabia has the highest number of plants including the world’s largest
Problems
High cost and energy footprint
Keeps down algal growth and kills many marine organisms
Large quantity of brine wastes
If dumped into nearby coastal waters it raises the salinity of that water to dangerous levels
Disposing of it on land could contaminate the limited surface and groundwater supplies

31. How Can We Use Water More Sustainably?

32. Reducing Water Waste Has Many Benefits
One-half to two-thirds of water is wasted
Subsidies mask the true cost of water
Water conservation
Improves irrigation efficiency
Improves collection efficiency
Uses less in homes and businesses

33. We Can Cut Water Waste in Irrigation
Most Common Method: Gravity Flow/Flood irrigation
Delivers far more water than can be absorbed before it is lost to evaporation
About 60% of the water used worldwide for irrigation does not reach its intended crop
More Efficient Options:
Center pivot, low pressure sprinkler (80% efficient)
Low-energy, precision application sprinklers (90-95% efficient)
Drip or trickle irrigation (90-95% efficient)

34. Major Irrigation Systems
Figure 13.18: Several different systems are used to irrigate crops. The two most efficient systems are the low-energy, precision application (LEPA) center-pivot system and the drip irrigation system. Because of high initial costs, they are not widely used. The development of new, low-cost, drip-irrigation systems may change this situation.
Fig , p. 335

35. Solutions: Reducing Irrigation Water Waste
Figure 13.19: There are a number of ways to reduce water waste in irrigation. Questions: Which two of these solutions do you think are the best ones? Why?
Fig , p. 336

36. 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 (sinks, showers and washing machines)
Pay-as-you-go water use

37. How Can We Reduce the Threat of Flooding?

38. Floodplains 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

39. We Can Reduce Flood Risks/Damages
Rely more on nature’s systems
Wetlands
Natural vegetation in watersheds
Rely less on engineering devices
Dams
Levees
Channelized streams
Reconsider how we design structures: