1. 15
Freshwater Resources: Natural Systems, Human Impact, and Conservation
Part D
PowerPoint® Slides prepared by
Jay Withgott and Kristy Manning
Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings

2. Groundwater pollution
Worse than surface water pollution, because it is longer lasting
(e.g., persistent toxicants get washed out of rivers, but remain in groundwater until they break down.)

3. Groundwater pollution
Sources are both natural and anthropogenic.
NATURAL SOURCES:
Arsenic
Aluminum
Fluoride
Nitrates
Sulfates
HUMAN SOURCES:
Leaky underground storage tanks (oil, gas, industrial chemicals, septic waste)
Nitrates from fertilizers
Pesticides
Pathogens from wells and feedlots
Contamination from underground hazardous waste disposal
Industrial chemical waste
Compounds from military sites

4. Groundwater pollution
Thousands of wells dug by international aid workers for the benefit of Bangladesh’s citizens turned out to be poisoned with natural sources of arsenic.
Mapped arsenic concentrations; red is highest

5. Success stories
Many water pollution problems have decreased since the 1960s and 1970s, due to legislation:
Clean Water Act of 1977 in the U.S.
Similar acts in other nations
The Great Lakes:
Canadian and U.S. governments decreased PCBs, DDE, fertilizers, etc., by 70–90%. Fish and bird populations are now recovering.

6. Pollution prevention
Drinking water is treated before it reaches your tap.
But it is easier and more cost effective to prevent pollution than to mitigate it once it occurs.

7. Wastewater and its treatment
Wastewater = water that has been used by people in some way
Septic systems = most popular method of wastewater disposal.
Wastewater treatment involves:
Primary treatment: physical removal of contaminants in settling tanks
Secondary treatment: water is aerated by being stirred up; aerobic bacteria degrades organic pollutants.

8. Wastewater and its treatment
The wastewater treatment process

9. Natural treatment
Artificial wetlands can aid treatment.

10. Conclusion
Ensuring adequate freshwater involves citizen action, legislation and regulation, new technologies, economic incentives, and public education.
The world is approaching widespread water scarcity.
Water depletion and pollution are affecting developing countries and arid areas of the developed world.
But potential solutions are numerous.

11. QUESTION: Review Which of the following is NOT true about aquifers?
a. They hold surface water.
b. They can be “confined” or “unconfined.”
c. They can become polluted by numerous toxic substances.
d. They generally are very slow to recharge.
Answer: A

12. QUESTION: Review
Which water body would contain many nutrients and low oxygen levels?
a. An oligotrophic lake
b. A eutrophic lake
c. A pristine fast-flowing mountain stream
d. The deep ocean
e. All of the above
Answer: B

13. QUESTION: Review
Which of the following is NOT true about dams and their associated reservoirs?
a. They alter riparian habitat.
b. They can capture sediment.
c. They can provide irrigation, hydropower, flood control, and drinking water.
d. They can never be removed once built.
e. They promote some types of recreation and inhibit others.
Answer: D

14. QUESTION: Review Which is a possible effect of groundwater depletion?
a. Subsidence and sinkholes
b. Sediment capture
c. Saltwater intrusion into aquifers
d. Both (a) and (b)
e. Both (a) and (c)
Answer: E

15. QUESTION: Weighing the Issues
As cities of the arid U.S. southwest grow and water becomes scarce, what should these metropolises do?
a. Pull as much water as they can from the Colorado River
b. Build desalination plants
c. Regulate industry and agriculture more heavily to restrict water waste
d. Promote conservation measures through education and market incentives
Answer: ANY

16. QUESTION: Interpreting Graphs and Data
What proportion of ALL water on Earth do lakes contain?
a. 52% c %
b. 1% d. It cannot be calculated from the information given.
Answer: D

17. QUESTION: Interpreting Graphs and Data
For each of its citizens, North America has…?
a. Less water than Asia c. Less water than Australia
b. Less water than Europe d. 47,000 km3/yr
Answer: C

18. QUESTION: Viewpoints Should we remove dams?
a. Yes; they have more costs than benefits.
b. Sometimes; we should judge them on a case-by-case basis.
c. No; they have more benefits than costs.
d. No; money and resources are best spent on other things.
Answer: ANY