1/25. When the well is dry, we will know the true worth of water. Benjamin Franklin. Monday, May 16, 16

Transcription

1 1/25 When the well is dry, we will know the true worth of water. Benjamin Franklin 1

2 Chapter 9 Water Resources

3 Usable Water is Rare

4 Continent Asia Percent of world's water resources and population 36% 60.5% Africa 10% 14% Europe 8% 11.3% North and Central 15% America 7.3% South America and Caribbean 6.4% 26% Oceania 5% 0.5% Fig. 14-2, p. 307

5 Groundwater Aquifers- small spaces found within permeable layers of rock and sediment where water is found. Unconfined aquifers- an aquifer that is simply porous rock covered by soil. Confined aquifers- an aquifer surrounded by a layer of impermeable rock or clay.

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7 Groundwater Water table- the uppermost level at which the water in an area fully saturates the rock or soil. Recharge- the input process of water percolating into an aquifer. Springs- water from an aquifer that naturally percolates up to the surface.

8 Groundwater Cone of depression- an area where there is no longer any groundwater.

9 Groundwater Overdrafts: High Moderate Minor or none Fig. 14-8, p. 314

10 Groundwater Saltwater intrusion- when the pumping of fresh water out of a well is faster than the recharge. Near coastal areas this can cause salt water to infiltrate the aquifer.

11 Trade-Offs Withdrawing Groundwater Advantages Useful for drinking and irrigation Available yearround Exists almost everywhere Renewable if not overpumped or contaminated No evaporation losses Cheaper to extract than most surface waters Disadvantages Aquifer depletion from overpumping Sinking of land (subsidence) from overpumping Polluted aquifers for decades or centuries Saltwater intrusion into drinking water supplies near coastal areas Reduced water flows into surface waters Increased cost and contamination from deeper wells Fig. 14-7, p. 313

12 Surface Water

13 Surface Water Productivity in a lake: ú Oligotrophic- low amounts of nutrients such as phosphorous and nitrogen. ú Mesotrophic- a moderate level of productivity ú Eutrophic- high levels of productivity

14 Altering the Availability of Water Levees- an enlarged bank built up on each side of the river. Dikes- similar to a levee but built to prevent ocean waters from flooding adjacent land.

15 Altering the Availability of Water Dams- a barrier that runs across a river or stream to control the flow of water. Reservoir- the area where water is stored behind the dam.

16 1/29 Water is life s mater and matrix, mother and medium. There is no life without water. Albert Szent-Gyorgyi 16

17 Provides water for year-round irrigation of cropland Flooded land destroys forests or cropland and displaces people Provides water for drinking Reservoir is useful for recreation and fishing Can produce cheap electricity (hydropower) Downstream flooding is reduced Large losses of water through evaporation Downstream cropland and estuaries are deprived of nutrient-rich silt Risk of failure and devastating downstream flooding Migration and spawning of some fish are disrupted Fig a, p. 317

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19 Altering the Availability of Water Fish ladders- a set of stairs with water flowing over them that have been added to some dams to help migrating fish such as salmon get upstream.

20 Altering the Availability of Water Aqueducts- canals or ditches used to carry water from one location to another.

21 IDAHO Dam WYOMING Aqueduct or canal Upper Basin Lower Basin NEVADA Salt Lake City UTAH Lake Powell Colorado River Grand Junction UPPER BASIN COLORADO Denver Las Vegas CALIFORNIA Los Angeles San Diego All-American Canal Palm Springs Grand Canyon Boulder City Yuma Mexicali Gulf of California ARIZONA Glen Canyon Dam LOWER BASIN Phoenix Tucson NEW MEXICO Albuquerque mi km MEXICO Fig , p. 318

22 Sacramento River North Bay Aqueduct San Francisco South Bay Aqueduct San Luis Dam and Reservoir California Aqueduct CALIFORNIA Shasta Lake NEVADA Oroville Dam and Reservoir Santa Barbara Feather River Sacramento San Joaquin Valley Los Angeles Lake Tahoe Fresno Hoover Dam and Reservoir (Lake Mead) Los Angeles Aqueduct Colorado River Aqueduct UTAH Colorado River ARIZONA Central Arizona Project San Diego Salton Sea Phoenix Tucson MEXICO Fig , p. 321

23 Altering the Availability of Water Desalinationremoving the salt from salt water to obtain fresh water.

24 Agriculture, Industry and Household Needs Agriculture- the largest user of water around the world.

25 Agriculture, Industry and Household Needs Irrigation techniquesú Furrow irrigation- a trench that is flooded with water. ú Flood irrigation- the entire field is flooded with water. ú Spray irrigation- an apparatus that sprays water across a field. ú Drip irrigation- using a slow dripping hose that is laid on or buried beneath the soil. ú Hydroponic agriculture- crops grown in fertilized water and no soil.

26 Hydroponics 26

27 Aquaponics 27

28 Future Farming? 28

29 Case Study: The Aral Sea Disaster Ø The Aral Sea was once the world s fourth largest freshwater lake. Figure 14-17

30 Agriculture, Industry and Household Needs Industry- the second largest user of water worldwide.

31 Agriculture, Industry and Household Needs Households- the third largest user of water worldwide.

32 The Future of Water Availability Water ownership- people can have rights to water use, but they do not own the water. Water conservation- using techniques such as more efficient water fixtures, faucets and washing machines.

33 Wash. Oregon Idaho Nevada Montana Wyoming N.D. S.D. Neb. Utah Colo. Kansas California Oak. N.M. Texas Highly likely conflict potential Substantial conflict potential Moderate conflict potential Unmet rural water needs Fig. 14-5, p. 310