Chapter 13: Water Resources

Transcription

1 Aqueducts in California Grand Coolee Dam Desalinization Chapter 13: Water Resources

2 Fresh Water on Earth Only a small fraction of Earth's water is fresh water & available for human use.

3 Discuss with your table partner: Predict what percentage of available fresh water is used for domestic and municipal purposes. What is the majority of fresh water used for?

4 Use of Fresh Water o o o

5 Hydrology Terms Watershed: region from which water drains into a water body Groundwater: water that is stored in voids between soil particles Aquifers: porous, water saturated layers of soil or rock through which groundwater flows Recharge area: any area of land through which water passes into an aquifer

6 Video: Ogallala Aquifer

7 Confined Recharge Area Precipitation Runoff Unconfined Aquifer Recharge Area Evaporation and transpiration Evaporation Flowing artesian well Infiltration Water table Well requiring a pump Infiltration Stream Lake Less permeable material such as clay

8 Washington Oregon Idaho Montana Wyoming North Dakota South Dakota Nevada Utah Colorado Nebraska Kansas California Arizona New Mexico Oklahoma Texas Highly likely conflict potential Substantial conflict potential Moderate conflict potential Unmet rural water needs

9 Estimated Stress on World s Major River Basins Based on comparison of the amount of water available with the amount used by humans. Europe Asia North America Africa South America Australia Stress High None

10 Supplying More Water Pumping Groundwater Dams and Reservoirs Water Transfers Desalinization of seawater

11 Consequences: Aquifer - land sinks when water is withdrawn Groundwater Groundwater in the U.S. is being withdrawn at about times its replacement rate

12 Groundwater Depletion in the US Ogallala Aquifer

13 Saudi Arabia: Groundwater Depletion Irrigation from pumping of groundwater from an ancient and nonrenewable aquifer in a vast desert region. Hydrologists estimate that because of aquifer depletion, most irrigated agriculture in Saudi Arabia may disappear within years

14 TRADE-OFFS Withdrawing Groundwater Advantages Useful for drinking and irrigation Available year-round 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 Aquifers polluted 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

15 SOLUTIONS Groundwater Depletion Prevention Waste less water Control Raise price of water to discourage waste Subsidize water conservation Limit number of wells Do not grow waterintensive crops in dry areas Tax water pumped from wells near surface waters Set and enforce minimum stream flow levels Divert surface water in wet years to recharge aquifers

16 Glen Canyon Dam built in 1963 and the Lake Powell Reservoir Dams and Reservoirs Second largest reservoir in the US

17 Dams & Reservoirs the Colorado River Dams & canals provides electricity & cheap water for agriculture, industry, & cities Limited water supply must be divided between farmers, ranchers, cities, Native Americans, Mexico, & wildlife Population growth in the lower basin is increasing demand beyond the allocated supply

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19 35 30 Hoover Dam completed (1935) Glen Canyon Dam completed (1963) Year

20 Colorado River Delta Now just a small salty stream when it reaches the Sea of Cortez (Gulf of California). The coastal wetlands are gone

21 Sacramento River North Bay Aqueduct San Francisco South Bay Aqueduct San Luis Dam and Reservoir California Aqueduct CALIFORNIA Shasta Lake Oroville Dam and Reservoir Santa Barbara Feather River Sacramento Los Angeles Lake Tahoe Fresno San Diego NEVADA Hoover Dam and Reservoir (Lake Mead) Los Angeles Aqueduct Colorado River Aqueduct UTAH Water Transfer: California Water Project Salton Sea Phoenix ARIZONA Colorado River Central Arizona Project Tucson MEXICO Fig , p. 330

22 Desalinization of Sea Water: Reverse Osmosis uses to move water through a selectively permeable membrane going the concentration gradient. The selectively permeable membrane allows flow of water molecules but not salt compounds. Distillation- Separates salt from water based on differing.

23 Discuss with your table partner: What are some negative impacts of either of these two processes to produce freshwater? Consider the inputs and outputs of the process. Requires

24 Desalinization of Sea Water The Jubail desalination plant in Saudi Arabia is the largest in the world. The plant produces 800 million gallons per day.

25 Using Water Efficiently Increase efficiency of irrigation drip irrigation, central pivot, computer monitoring Use recycled water treat gray water from Fix leaky pipes Water saving toilets, faucets, & shower heads Xeriscaping

26 Water Loss Calculator

27 Gravity flow (efficiency 60% and 80% with surge valves) Water usually comes from an aqueduct system or a nearby river. Drip irrigation (efficiency 90 95%) Above- or below-ground pipes or tubes deliver water to individual plant roots. 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.

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30 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 Get agreements among regions and countries sharing surface water resources Raise water prices Slow population growth Fig , p. 337

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32 Discuss with your table partner: What human activities can exacerbate the risk of flooding? Explain why. What kind of paving materials can reduce the risk of flooding? Explain all the benefits of this type of materials.

33 Human activities that exacerbate flooding: Flooding Removing - Destruction of Building on flood plains with

34 Oxygen released by vegetation Diverse ecological habitat Tree roots stabilize soil Evapotranspiration Trees reduce soil erosion from heavy rain and wind Agricultural land Tree plantation Gullies and landslides Roads destabilize hillsides Heavy rain erodes topsoil Evapotranspiration decreases Overgrazing accelerates soil erosion by water and wind Winds remove fragile topsoil Agricultural land is flooded and silted up Vegetation releases water slowly and reduces flooding Silt from erosion fills rivers and reservoirs Rapid runoff causes flooding Forested Hillside After Deforestation

35 SOLUTIONS Reducing Flood Damage Prevention Preserve forests on watersheds Control Straighten and deepen streams (channelization) Preserve and restore wetlands in floodplains Tax development on floodplains Use floodplains primarily for recharging aquifers, sustainable agriculture and forestry Build levees or floodwalls along streams Build dams

36 pavement: o o