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Water Chapter 15. Water Wars Water shortage Growing population Poor irrigation efficiency Economic competition- importing more grain to reduce need for.

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Presentation on theme: "Water Chapter 15. Water Wars Water shortage Growing population Poor irrigation efficiency Economic competition- importing more grain to reduce need for."— Presentation transcript:

1 Water Chapter 15

2 Water Wars Water shortage Growing population Poor irrigation efficiency Economic competition- importing more grain to reduce need for irrigation water or work out water-sharing agreements with other countries

3 Unique Properties of Water Strong hydrogen bonds Liquid over wide temperature range High heat capacity – changes temperature slowly (moderates climate, used as coolant for car engine & power plants) Large amount of energy needed to evaporate – heat is then released during condensation (helps distribute heat & determine climate zones; evaporation/sweating = cooling process)

4 Dissolves many substances- dissolves nutrients in living tissue, flush waste out of tissues, all-purpose cleanser, helps remove/dilute water-soluble waste Filters out UV radiation that would harm aquatic organisms Bonds – allow capillary action – water can move upward through plants Expands when frozen= ice floats; prevents lakes & streams from freezing solid

5 Available Freshwater Only 0.014% is available for useh

6 Water Cycle Surface runoff- water flowing off the land into bodies of surface water Reliable runoff- amount of run-off that we can generally count on as a stable source of water Watershed (drainage basin)- region from which surface water drains into a river, lake, wetland, or other body of water

7 Groundwater- water stored in spaces in soil & rock Zone of aeration- close to surface; pore space contains mixture of air & water Zone of saturation- lower layers of soil where pore space is filled with water Water table- top of zone of saturation Aquifer- (deep) porous, water-saturated layers of sand, gravel, or bedrock through which groundwater flows

8 Natural recharge- natural replenishment of an aquifer by precipitation, which percolates downward through soil & rock Shortages result from: Removing groundwater faster than it is replenished Some aquifers receive little, if any recharge

9 Water Use Withdrawal- total amount of water removed from lake, river, or aquifer for any purpose Consumptive water use- withdrawn water is not available for reuse in basin due to losses like evaporation, seepage into ground, transportation to another area, or contamination

10 Water Use Population- up 3x Global water withdrawal- up 7x Per capita withdrawal- up 4x Reliable surface runoff used- 34% Used by % (90% if per capita rises too)

11 Irrigation- 70% Industry- 20% Residences & cities- 10%

12 Eastern U.S. Major water use- energy production, cooling, & manufacturing Problems- flooding, occasional urban shortages, pollution

13 Western U.S. Major water use- irrigation Problems- shortage of runoff, low precipitation / high evaporation, recurring prolonged drought

14 Causes of Water Scarcity Dry climate Drought- prolonged period with 70% less precipitation & higher than normal evaporation Dessication- drying of exposed soil due to deforestation or overgrazing Water stress- low per capita availability due to high population relying on limited runoff

15 Increase Freshwater Supply Build dams & reservoirs to store runoff Bring in surface water from another area Desalinization Reduce water waste Import food to reduce water use in crops & cattle Withdraw groundwater

16 Government Ownership - Poor management & efficiency + Strict government oversight + Equal access & fair rates

17 Private Ownership + Funds & management expertise + Improved efficiency, good job - No rate control - Profitable - Sold as a luxary, not basic need

18 Large losses of water through evaporation Flooded land destroys forests or cropland and displaces people Downstream flooding is reduced Downstream cropland and estuaries are deprived of nutrient-rich silt Reservoir is useful for recreation and fishing Can produce cheap electricity (hydropower) Migration and spawning of some fish are disrupted Provides water for year-round irrigation of cropland Figure 15-9 Page 313

19 Colorado River Dams + Provides electricity from numerous hydroelectric plants + Provides water for 7 states + Multibillion dollar recreational industry (whitewater rafting, boating, fishing, camping, hiking) - Arid area - Legal pacts allocating water supply for US & Mexico - River water rarely makes it to Guld of California

20 - Threatens aquatic spawning - Destroys estuaries - Increases saltwater contaminated coastal aquifers

21 Figure Page 315 Trade-Offs Chinas Three Gorges Dam Advantages Disadvantages Will generate about 10% of Chinas electricity Reduces dependence on coal Reduces air pollution Reduces CO 2 emissions Reduces chances of downstream flooding for 15 million people Reduces river sitting below dam by eroded soil Increases irrigation water for cropland below dam Floods large areas of cropland and forests Displaces 1.9 million people Increases water pollution because of reduced water flow Reduces deposits of nutrient- rich sediments below dam Increases saltwater Introduced into drinking water near mouth of river because of decreased water flow Disrupts spawning and migration of some fish below dam High cost

22 Aral Sea Water Transfer Project Shrinking of Aral Sea Regional ecological, economic, health disaster Salinity 3x higher Surface area down 58% 83% water loss Feeder rivers reduced to trickles Eliminates wetlands Birds & mammal species disappeared

23 Extinction of 20 (of 24) native fish species Salt dust settles on wildlife, crops, & other vegetation

24 California Water Transfer Project NORTH Degrade Sacramento River Threatens fisheries Reduces flushing of San Francisco Bay pollutants Water sent South is wasted SOUTH Need more water to grow crops Lakes shrink = reduced populations of ducks, gulls, & wading birds

25 James Bay in Canada dams & dikes that will reverse or alter flow of 19 giant rivers - Will flood boreal forests & tundra - Displace of indigenous Cree & Inuits + Hydroelectric power

26 Figure Page 319 Trade-Offs Withdrawing Groundwater Advantages Disadvantages Good source of water for drinking and irrigation Available year-round Exists almost everywhere Renewable if not over- pumped or contaminated No evaporation losses Cheaper to extract than most surface waters Aquifier depletion from over- pumping Sinking of land (subsidence) when water removed Polluted aquifiers unusable for decades or centuries Saltwater intrusion into drinking water supplies near coastal areas Reduced water flows into streams, lakes, estuaries, and wetlands Increased cost, energy use, and contamination from deeper wells

27 Excessive Withdrawal Unsustainable water mining Limits future food production Increases gap between rich & poor areas Must drill deeper wells, buy larger pumps, & use more electricity Causes sinkholes

28 Saltwater Intrusion Movement of salt water into freshwater aquifers in coastal & inland areas as groundwater is withdrawn faster than it is recharged by precipitation Groundwater becomes unusable

29 Ogallala Aquifer + Transformed vast areas of arid prairie into productive agricultural land - Slows recharge rate - Aquifer is thinner for southern region - Government subsidies increased crop production & increases depletion of aquifer

30 Figure Page 320 Solutions Groundwater Depletion Prevention Control Waste less water Subsidize water conservation Ban new wells in aquifiers near surface waters Buy and retire ground- water withdrawal rights in critical areas Do not grow water- intensive crops in dry areas Reduce birth rates Raise price of water to discourage waste Tax water pumped from Wells near surface water Set and enforce minimum stream flow levels

31 Deep Aquifer Concerns: Little known about geological & ecological impacts of using these aquifers No international water treaties govern the rights to & ownership of water that underlies several countries

32 Desalinization - High cost - Large energy requirements - Large amounts of briny waste water - Dumping of waste increases salinity of ocean water (food resources & aquatic life threatened) + Make ocean water or brackish water usable

33 Seeding Clouds Does not work well in very dry areas No scientific evidence of success Introduces large amounts of chemicals into soil & water systems (harms people, wildlife, & agricultural productivity) Ownership of cloud water

34 Iceberg Towing Unsure methods Cost Probably neither (iceberg towing or cloud seeding) would provide significant amounts of freshwater

35 Wasted Water 65-70% of world water is wasted Could be reduced to 15% Causes: Underpricing- government subsidies for irrigation water, electricity, & diesel fuel for farmers to pump water at below-market price Lack of government subsidies for improving efficiency of water use

36 Irrigation Systems Center pivot- uses pump to spray water on crops 80% efficient Uses 25% less water Drip irrigation- microirrigation- above or below ground pipes or tubes deliver water to individual plant roots 90-95% efficient Gravity flow- water flow into ditches from aqueduct or nearby river 60-80% efficient

37 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. Figure Page 324

38 Figure Page 324 Solutions Reducing Irrigation Water Waste Lining canals bring water to irrigation ditches Leveling fields with lasers Irrigating at night to reduce evaporation Using soil and satellite sensorsand computer systems to monitor soil moisture and add water only when necessary Polyculture Organic Farming Growing water-efficient crops using drought- resistant and salt tolerant crops varieties Irrigating with treated urban waste water Importing water-intensive crops and meat

39 Figure Page 325 Reducing Water Waste Solutions Redesign manufacturing processes Landscape yards with plants that require little water Use drip irrigation Fix water leaks Use water meters and charge for all municipal water use Use waterless composting toilets Require water conservation in water-short cities 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

40 Reducing Water Used to Remove Waste Use pollution prevention & waste reduction to decrease waste production Ban toxic wastes in municipal sewer system Waterless composting toilet Nutrient-rich sludge returned to soil as fertilizer New sewage treatment methods that recycle nutrients in organic waste material

41 Floods + Fertile soils + Ample water for irrigation + Rivers for transportation & recreation + Flat land suitable for crops, buildings, highways, & railroads - Removal of water-absorbing vegetation

42 Increasing Flood Damage Removal of water-absorbing vegetation Draining wetlands Living on floodplains Pavement & buildings

43 Bangladesh Straighten & deep streams Build levees or floodwalls Build dams Preserve existing wetlands & restore degraded wetlands Identify & manage flood-prone areas Think carefully about where we live

44 Figure Page 329 Not depleting aquifers Preserving ecological health of aquatic systems Preserving water quality Integrated watershed management Agreements among regions and countries sharing surface water resources Outside party mediation of water disputes between nations Marketing of water rights Raising water prices Wasting less water Decreasing government subsides for supplying water Increasing government subsides for reducing water waste Slowing population growth Solutions Sustainable Water Use

45 Figure Page 330 Use water-saving toilets, showerheads, and faucet aerators Shower instead of taking baths, and take short showers. Repair water leaks. Turn off sink faucets while brushing teeth, shaving, or washing. Wash only full loads of clothes or use the lowest possible water-level setting for smaller loads. Wash a car from a bucket of soapy water, and use the hose for rinsing only. 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. Water lawns and garden in the early morning or evening. Use drip irrigation and mulch for gardens and flowerbeds. Use recycled (gray) water for watering lawns and houseplants and for washing cars. What Can You Do? Water Use and Waste


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