2 Essential Question #1Why is water so important, how much fresh water is available to us, and how much of it are we using?
3 Why is Water Important Major part of organisms (60%) Affects Climate Without water, chemical reactions can’t occurAffects ClimateCarves the LandRemoves and dilutes wastes & pollutantsCycles continuouslyDespite it’s importance, water is one of our most poorly managed resources.We waste it, pollute it, & charge too little for making it available
4 Where is Freshwater Available? 97.4% salt water, 2.6% freshwaterOf that 2.6% freshwater:75% is frozen90% of melted freshwater is in lakes, soil & air
5 Readily accessible fresh water Earth’s Water BudgetAll waterFresh waterReadily accessible fresh waterGroundwater0.592%Biota0.0001%Rivers0.0001%Lakes0.007%Fresh water2.6%0.014%Oceans andsaline lakes97.4%Atmosphericwater vapor0.001%Ice capsand glaciers1.984%Soilmoisture0.005%Only about 0.024% of water is available as accessible, liquid freshwater!Fig. 11-2, p. 238
6 Availability of Water Resources Percent of world's water resources and populationContinent36%Asia60.5%10%Africa14%GlobalAvailability of Water Resources8%Europe11.3%15%North and Central America7.3%QUESTION: What two major conclusions can you draw from these data?26%South America and Caribbean6.4%5%Oceania0.5%Fig. 14-2, p. 307
7 Ground WaterWater below the earth’s surface, stored in spaces in soil, gravel, sand & rockWater table – top of ground water layer (zone of saturation)Rises & falls w/ precipitation changesAquifers – deep layers of porous rock holding water1/3 of world pumps water from aquifersWatertight layers of rock or clay below aquifers prevent water from sinking deeper into Earth.
8 Evaporation and transpiration Groundwater SystemsUnconfined Aquifer Recharge AreaEvaporation and transpirationPrecipitationEvaporationConfinedRechargeAreaRunoffFlowingartesian wellRechargeUnconfinedAquiferStreamWell requiring a pumpWatertableInfiltrationLakeInfiltrationUnconfined aquiferLesspermeable materialsuch as clayConfined aquiferConfining impermeable rock layerFig. 11-3, p. 239
10 Aquifers Renewable Aquifers Nonrenewable Aquifers Natural Recharge – precipitation percolates down to refill (slow process)Lateral Recharge – refilled from side by streams/riversNonrenewable AquifersReceive little to no recharge
11 Surface Water Surface Runoff Watershed / Drainage Basin Precipitation that doesn’t evaporate or soak into ground2/3 lost to seasonal floodingWatershed / Drainage BasinThe region where runoff flows into water bodiesReliable RunoffThe amount of runoff we can count on as a stable source of fresh water *(1/3 of surface runoff)2/3 surface runoff lost to floods, 1/3 makes up reliable runoff
12 Water Withdrawal Consumptive Use Nonconsumptive Use Does not return water to original source~70% of withdrawn waterNonconsumptive UseTemporarily removes water from sourceEx: Power plant using water for coolingWithdrawal – total amount of water we remove from a river, lake, aquifer, etc.
13 How much water do we use? 70% = Irrigation 20% = Industrial Use 10% = Cities & Residencies(1lb of beef = 6 months of showers!)
14 How much water do we use?We currently withdraw 34% of reliable runoff.But to meet demands of growing population we may be using 70-90% by 2025.
15 Annual Precipitation determines who has & does not have water resources Precipitation NOT evenly distributed!Fig. 11-4a, p. 240
16 Freshwater Resources in the United States 17 western states by 2025 could face intense conflict over scarce water needed for urban growth, irrigation, recreation and wildlife.Figure 14-5
17 Cooperation?No cooperative agreements exist for 158 of 263 watersheds shared by two or more countriesConflicts likely to increase as population & demand continue to rise
18 Question #2What causes freshwater shortages, and what can be done to increase freshwater supplies?
19 Causes of Freshwater Shortages Dry ClimateDroughtLarge PopulationPovertyDrought – a prolonged period in which precipitation is at least 70% lower and evaporation is higher than normal
20 Stress on the World’s River Basins 1 in 6 don’t have access to adequate & affordable supply of clean water.Buy 2050 this could be 1 in 4.The Middle East is among the most water impoverished areas globally, already experiencing disagreements over water rights. By 2050, ~60 countries will be suffering from water stress.
21 Could you live on 1 gallon of water/day for all your needs? Hydrological PovertyCould you live on 1 gallon of water/day for all your needs?More than 2/3 of the world’s households do not have running water. When water is scarce, not much is used toward sanitation or hygiene.
22 Ways to Increase Freshwater Supplies Dams & ReservoirsWater TransfersUsing GroundwaterDams & Reservoirs- Pro: cheap electricity / reduces flooding / increases freshwater supply- Con: disrupts downstream flow & upsets ecosystems / floods productive landWater Transfers- Pro: provides water to areas w/ little- Con: degrades rivers & disrupts ecosystems / use to grow water needy plants in areas w/ lil natural water- example: Aral Sea – created major ecological, economic & health disasterUsing Groundwater- Pro: Renewable if not overpumped / cheap / available most places unless polluted or contaminated by salt- Con: US 4x replacement rate / causes land to sink / unuseable once
23 Ways to Increase Freshwater Supplies DesalinationDistillation & reverse osmosisImport foodWaste LessDesalination- Con: high cost / no solution for what to do with resulting salt wasteImporting food– reduces water waste used for crops / livestock- takes 1,000 tons of water to produce 1 ton of grainWaste Less- charge more to increase conservation- improve irrigation techniques- provide govt subsidies for improving water conservation in agriculture / industry- fix leaks in homes, businesses, infrastructure- install low-flow toilets, showers, etc
24 What are the advantages and disadvantages of withdrawing groundwater? Essential Question #3What are the advantages and disadvantages of withdrawing groundwater?
25 Withdrawing Groundwater To Increase Supplies Aquifers are Renewable as long as NOT:OverpumpedContaminatedGroundwater depletion for Irrigation is a growing problemAt least one-fourth of the farms in India are being irrigated from overpumped aquifers.Currently provide about ¼ of world’s water
26 Effects of Groundwater Overpumping Contaminates freshwater aquifers near coastal areas with saltwater.Sinkholes form when drained aquifers collapseSinkholes can also occur naturally in areas high in limestone. Aquifer waters can dissolve limestone causing a cave in.
27 Groundwater Contamination Example: Contamination from fracking
28 Withdrawing Groundwater Trade-OffsWithdrawing GroundwaterAdvantagesDisadvantagesUseful for drinking and irrigationAquifer depletion from overpumpingSinking of land (subsidence) from overpumpingAvailable year-roundExists almost everywherePolluted aquifers for decades or centuriesRenewable if not overpumped or contaminatedSaltwater intrusion into drinking water supplies near coastal areasNo evaporation lossesReduced water flows into surface watersCheaper to extract than most surface watersIncreased cost and contamination from deeper wellsFig. 14-7, p. 313
29 Groundwater Depletion: A Growing Problem Areas of greatest aquifer depletion from groundwater overdraft in the continental U.S.Groundwater is being withdrawn 4x faster than it’s being replenishedThe Ogallala, the world’s largest aquifer, is most of the red area in the center (Midwest).Figure 14-8
30 Groundwater Depletion SolutionsGroundwater DepletionPreventionControlWaste less waterSubsidize water conservationRaise price of water to discourage wasteBan new wells in aquifers near surface watersTax water pumped from wells near surface watersBuy and retire groundwater withdrawal rights in critical areasSet and enforce minimum stream flow levelsDo not grow water-intensive crops in dry areasFig , p. 316
31 Essential Question #4What are the advantages and disadvantages of using dams to supply more water?
33 Provides water for year-round irrigation of cropland Flooded land destroys forests or cropland and displaces peopleLarge losses of water through evaporationProvides water for drinkingDownstream cropland and estuaries are deprived of nutrient-rich siltReservoir is useful for recreation and fishingRisk of failure and devastating downstream floodingCan produce cheap electricity (hydropower)Trade-offs: advantages (left) and disadvantages (right) of large dams and reservoirs.The world’s 45,000 large dams (higher than 15 meters or 50 feet) capture and store 14% of the world’s runoff, provide water for almost half of all irrigated cropland, and supply more than half the electricity used by 65 countries. The United States has more than 70,000 large and small dams, capable of capturing and storing half of the country’s entire river flow.Downstream flooding is reducedMigration and spawning of some fish are disruptedFig a, p. 317
34 Powerlines Reservoir Dam Powerhouse Intake Turbine River Fig b, p. 317
35 The Colorado Basin – an Overtapped Resource The Colorado River has so many dams and withdrawals that it often does not reach the ocean.14 major dams and reservoirs, and canals.Water is mostly used in desert area of the U.S.Provides electricity from hydroelectric plants for 30 million people (1/10th of the U.S. population).
36 The Colorado River Basin The area drained by this basin is equal to more than one-twelfth of the land area of the lower 48 states.Figure 14-14
37 Dam RemovalSince 1998, U.S. Army Corps of Engineers no longer building dams / water diversion projects in USMany dams being removed b/c of age or ecological reasonsDifficult & Expensive
38 Essential Question #5What are the advantages and disadvantages of transferring large amounts of water from one place to another?
39 Advantages of Water Transfer Makes unproductive areas more productivePromotes investment / jobs / economy
40 Disadvantages of Water Transfer Encourages unsustainable use in water scarce areasReduces water availability from sourceExamples:Aral Sea DisasterCalifornia Water ProjectSouth-to-North ChinaWater Diversion Project($58 billion)
41 Essential Question #6How can removing salt from water solve our water supply problems? Why or why not?
43 Disadvantages Not Practical High cost / High Energy Disposal of waste salts / minerals / toxinsProjects involving desalination by renewable energy means are underway.
44 Other Ideas: Unlikely Cloud Seeding Towing Icebergs Giant Water Bags Costly, no scientific evidence of success, unintended ecological consequences
45 How can we waste less water? Essential Question #7How can we waste less water?
46 Water Waste65-70% of water used is lost to evaporation, leaks, & other lossesAbout 60% of water used for crop irrigation is lost due to inefficient methods
47 (efficiency 60% and 80% with surge valves) Improving IrrigationGravity flow(efficiency 60% and 80% with surge valves)Figure 14.18Major irrigation systems: because of high initial costs, center-pivot irrigation and drip irrigation are not widely used. The development of new low-cost drip-irrigation systems may change this situation.Center pivotDrip irrigation(efficiency 80%–95%)(efficiency 90–95%)Above- or below-ground pipes or tubes deliver water to individual plant roots.Water usually pumped from underground and sprayed from mobile boom with sprinklers.Water usually comes from an aqueduct system or a nearby river.
48 Reducing Water Waste Charge more to increase conservation Improve irrigation techniques (drip irrigation)Give financial incentives (subsidies) for improving water conservation in agriculture / industryGovernment subsidies keep water prices artificially low to help the agriculture industry. Prices so low, there’s no incentive to invest in water saving technologies.
49 Reducing Water Waste Fix leaks in homes, businesses, infrastructure Install low-flow toilets, showers, etcUsed recycled water (gray water) for watering homePlant drought tolerant plants
51 Solutions Reducing Water Waste • Redesign manufacturing processes • Repair leaking underground pipes• Landscape yards with plants that require little water• Use drip irrigation• Fix water leaks• Use water meters• Raise water prices• Use waterless composting toilets• Require water conservation in water-short citiesFigure 14.21Solutions: methods of reducing water waste in industries, homes, and businesses. QUESTION: Which three of these solutions do you think are the most important?• 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• Don't waste energyFig , p. 327
52 What causes flooding, and what can we do to reduce flood risks? Essential Question #8What causes flooding, and what can we do to reduce flood risks?
53 What is a flood?When water leaves its normal channel and spills into its adjacent floodplainFloodplain – areas in which flood waters spill into; typically contain wetlands that provide natural flood & erosion control
54 What causes flooding? Heavy Rain Rapid Snow Melt Removing Plants Destroying WetlandsImpervious StructuresPavement / BuildingsSince the 1960’s, human activities have contributed to increased flooding:- damming & altering rivers w/ levees increase flood risks b/c can be easily overwhelmed- removing water-absorbing vegetation- draining & removing wetlands that act as natural sponges for flood water
56 Flooding After Deforestation of a Hillside Fig , p. 253
57 How can we reduce flood risks? Straighten & deepen rivers/streamsBuild LeveesBuild DamsThese solutions have ecological problemsCan increase erosionCan be overwhelmed by excess flood water
58 How can we reduce flood risks? Preserve & Restore Wetlands (best solution)Act as a natural sponge for flood watersBetter identify flood plains & think about where we live
59 Preserve forests on watersheds SolutionsReducing Flood DamagePreventionControlPreserve forests on watershedsStrengthen and deepen streams (channelization)Preserve and restore wetlands in floodplainsBuild levees or floodwalls along streamsTax all development on floodplainsFigure 14.24Solutions: methods for reducing the harmful effects of flooding. QUESTION: Which two of these solutions do you think are the most important?Use floodplains primarily for recharging aquifers, sustainable agriculture and forestry, and recreationBuild damsFig , p. 331
60 How can we use the earth’s water more sustainably ? Essential Question #9How can we use the earth’s water more sustainably ?
61 Sustainable Water UseImprove monitoring of water sources to improve managementProtect ecosystems involved in water cycleRegulate withdrawalsChange subsidies to promote water conservationImprove wastewater treatmentSlow population growth & thus demand
62 What Can We Do? What Can You Do? Fig. 11-21, p. 251 Water Use and WasteUse water-saving toilets, showerheads, and faucet aeratorsShower 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.Fig , p. 251