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ppt on dams

ppt on dams

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  • 1. Dams and Development - Report of the World Commission on Dams P.P.TP.P.T ONON DamsDams
  • 2. Dams and reservoirsDams and reservoirs ReservoirsReservoirs • Site selectionSite selection • Leakage fromLeakage from reservoirsreservoirs • SedimentationSedimentation • Stability: effect ofStability: effect of raised WTraised WT DamsDams • TypesTypes • Forces on a damForces on a dam • Geology and damGeology and dam sitessites • Rock types andRock types and damsdams • Dams on soilsDams on soils • GroundGround improvementimprovement
  • 3. Dams and reservoirs - literatureDams and reservoirs - literature • Bell F.G., Engineering geology andBell F.G., Engineering geology and geotechnicsgeotechnics – Ch 6 (Reservoirs)Ch 6 (Reservoirs) – Ch 7 (Dams)Ch 7 (Dams) • Blyth F.G.H. and de Freitas M.H., A geologyBlyth F.G.H. and de Freitas M.H., A geology for engineersfor engineers – Ch 14 (Reservoirs and dams)Ch 14 (Reservoirs and dams)
  • 4. Reservoirs: purposeReservoirs: purpose • Water storageWater storage • Flood preventionFlood prevention • PowerPower
  • 5. Reservoirs: site selectionReservoirs: site selection • Hydrological considerationsHydrological considerations • Fundamental controlsFundamental controls – topographytopography – climateclimate – geologygeology WaterWater addedadded Net amount of waterNet amount of water available for storageavailable for storage WaterWater subtractedsubtracted++ Rainfall in riverRainfall in river basinbasin InfiltrationInfiltration EvaporationEvaporation TranspirationTranspiration RunoffRunoff
  • 6. Reservoirs: leakageReservoirs: leakage WaterWater addedadded Leakage fromLeakage from reservoirreservoir WaterWater subtractedsubtracted-- Rainfall inRainfall in river basinriver basin InfiltrationInfiltration EvaporationEvaporation TranspirationTranspiration Net amount of waterNet amount of water available for storageavailable for storage RunoffRunoff -- 1. Dam bypass1. Dam bypass 2. Water table effects2. Water table effects
  • 7. Leakage via subsurface bypass due to siphon effectLeakage via subsurface bypass due to siphon effect Devonian strataDevonian strata DevonianstrataDevonianstrata Devonian strataDevonian strata Dol-y-gaer damDol-y-gaer dam Carboniferous strata:Carboniferous strata: Subsurface water flowSubsurface water flow reservoir levelreservoir level fracture and dissolutionfracture and dissolution flow routesflow routes Reservoirs: leakageReservoirs: leakage
  • 8. Leakage buried channels beneath driftLeakage buried channels beneath drift 50 km50 km Modern river/valleyModern river/valley Ancient river/valleyAncient river/valley R Drac R Drac SautetSautet dam anddam and reservoirreservoir Bypass of reservoir in driftBypass of reservoir in drift Reservoirs: leakageReservoirs: leakage
  • 9. land surface land surface water table water table riverriver reservoirreservoir beforebefore afterafter water table dividewater table divide Leakage to next valleyLeakage to next valley Bedrock with a waterBedrock with a water table and finitetable and finite permeabilitypermeability newnew waterwater tabletable Reservoirs: water tableReservoirs: water table leakage-1leakage-1
  • 10. Land surface Land surface riverriver beforebefore Bedrock with lowBedrock with low permeability: aquicludepermeability: aquiclude HighHigh permeabilitypermeability layerlayer Water table in aquiferWater table in aquifer reservoirreservoir afterafter HighHigh permeabilitypermeability layerlayer Modified water table in aquiferModified water table in aquifer Leakage to next valleyLeakage to next valley Reservoirs: water tableReservoirs: water table leakage-2leakage-2
  • 11. Reservoirs:Reservoirs: sedimentationsedimentation • World’s largest dam;World’s largest dam; 180m tall, 2km wide180m tall, 2km wide – 84% sediment in84% sediment in rainy season (june-rainy season (june- sept)sept) – drawdown anddrawdown and sediment sluicingsediment sluicing during this periodduring this period
  • 12. BeforeBefore Water tableWater table riverriver After - 1After - 1 reservoirreservoir Raised water tableRaised water table After - 2After - 2 reservoirreservoir Failure andFailure and slumpingslumping due todue to weakenedweakened rock massrock mass Reservoirs: raised waterReservoirs: raised water tabletable
  • 13. Viaont dam disaster, ItalyViaont dam disaster, Italy
  • 14. Normal stressNormal stress σσnn ShearstressShearstressσσss σσ1,WT1,WTσσ3,3, WTWT UnstableUnstable StableStable σσ11σσ33 σσss == c +c + µµ .. ((σσnn - p)- p) p = pore fluid pressurep = pore fluid pressure σσnn – p = effective stress– p = effective stress Raising water tableRaising water table Reservoirs: raised waterReservoirs: raised water tabletable
  • 15. Dams: typesDams: types • Gravity dam: rigid monolithic structureGravity dam: rigid monolithic structure – Trapezoidal cross sectionTrapezoidal cross section – Minimal differential movement toleratedMinimal differential movement tolerated – Dispersed moderate stress on valley floor andDispersed moderate stress on valley floor and wallswalls • Arch dam: high strength concrete wallArch dam: high strength concrete wall – Convex faces upstreamConvex faces upstream – Thin walled structureThin walled structure – Relatively flexibleRelatively flexible – Huge stresses imposed on valley walls andHuge stresses imposed on valley walls and floorfloor • Earth dams: bank or earth or rock withEarth dams: bank or earth or rock with impermeable coreimpermeable core – Core of clay or concrete, extended belowCore of clay or concrete, extended below groundground – Sand or gravel drains built to cut fluidSand or gravel drains built to cut fluid pressurepressure
  • 16. Types of damTypes of dam ArchArch GravityGravity ButtressButtress EmbankmentEmbankment or Earthor Earth
  • 17. Emosson Dam, SwitzerlandEmosson Dam, Switzerland
  • 18. The Vaiont dam todayThe Vaiont dam today
  • 19. Dams: forces appliedDams: forces applied • Vertical static forcesVertical static forces • Lateral force applied by water bodyLateral force applied by water body • Dynamic forcesDynamic forces – wave actionwave action – overflow of water (controlled by spillwayoverflow of water (controlled by spillway channels)channels) – earthquakes and tremorsearthquakes and tremors – ice/freezingice/freezing
  • 20. Dam failure: earthquakeDam failure: earthquake
  • 21. Dam failure: asteroidsDam failure: asteroids
  • 22. Dam failure: bombsDam failure: bombs
  • 23. Poor geological characterisation of dam foundationPoor geological characterisation of dam foundation responsible for 40% of dam failuresresponsible for 40% of dam failures Need proper site investigationNeed proper site investigation Dam sites: geologyDam sites: geology
  • 24. Poor geological conditions can be improved in 2 waysPoor geological conditions can be improved in 2 ways • improving load bearing propertiesimproving load bearing properties • controlling seepagecontrolling seepage gravelgravel sandsand siltsilt clayclay >10>10 22 0.070.07 0.0020.002 <0.0001 mm grain size<0.0001 mm grain size Rolling, bolting and pre-loadingRolling, bolting and pre-loading gravity drainagegravity drainage well-points with drainagewell-points with drainage electro-osmosiselectro-osmosis vibro flotationvibro flotation explosivesexplosives groutsgrouts chemical treatmentschemical treatments thermal treatmentthermal treatment groundstrengtheninggroundstrengthening Dams: groundDams: ground improvementimprovement
  • 25. Dams: groundDams: ground improvementimprovement • Rock boltsRock bolts • Rolling and preloadingRolling and preloading – compresses ground in prep for structurecompresses ground in prep for structure – improves post dam compactionimproves post dam compaction • Gravity drainage and well points:Gravity drainage and well points: – sand and gravel channels and shallow wells (for pumping) Electro-osmosis: insertsand and gravel channels and shallow wells (for pumping) Electro-osmosis: insert conduction rods into fine grained clay-rich bedrock and have an electric field - de-conduction rods into fine grained clay-rich bedrock and have an electric field - de- waters ground via the flow of electric currentwaters ground via the flow of electric current • VibroflotationVibroflotation – mechanical vibrating plate with load compresses low density gravels and sandsmechanical vibrating plate with load compresses low density gravels and sands • ExplosivesExplosives – useful in water-saturated gravel and scree – increases bulk densityuseful in water-saturated gravel and scree – increases bulk density • GroutsGrouts – material injected into the groundmaterial injected into the ground • Chemical treatmentsChemical treatments – react solutions injected into ground. React with material to alter properties. NaClreact solutions injected into ground. React with material to alter properties. NaCl solution injected into smectite-rich mud, shale etc. to alter expansivity of smectite –solution injected into smectite-rich mud, shale etc. to alter expansivity of smectite – stabilizes ground pre-constructionstabilizes ground pre-construction • Thermal treatmentThermal treatment – FreezingFreezing with injected liquid N2 to consolidate loose ground during excavation.with injected liquid N2 to consolidate loose ground during excavation. HeatingHeating by burning petroleum under pressure in subsurface – causes thermalby burning petroleum under pressure in subsurface – causes thermal metamorphism - hardens ground and cuts porositymetamorphism - hardens ground and cuts porosity
  • 26. InjectedInjected grout curtaingrout curtain Pre-stressedPre-stressed anchorsanchors DrainDrain Apron drains (toApron drains (to individual aquifers)individual aquifers) ExcavationExcavation to rockto rock RegolithRegolith ReservoirReservoir Ripraptokill Ripraptokill waveenergy waveenergy Hard face to damHard face to dam Aquifer layersAquifer layers Aquiclude layersAquiclude layers Core and rear of damCore and rear of dam
  • 27. • In Turkey, 536 large dams have been built andIn Turkey, 536 large dams have been built and being operated. On the other hand, Smallbeing operated. On the other hand, Small Hydraulic Works Department has built 42 smallHydraulic Works Department has built 42 small dams.dams. • Here, 50 storage facilities that are not consideredHere, 50 storage facilities that are not considered as dam due to their low heights (<15m) and lowas dam due to their low heights (<15m) and low storage capatcities (<2 hmstorage capatcities (<2 hm33 ) have not been taken) have not been taken into account.into account. • By now, construction of 100 dams andBy now, construction of 100 dams and hydroelectric powerplants is going on.hydroelectric powerplants is going on.
  • 28. DefinitionDefinition • A dam is a structure which prevents the flowA dam is a structure which prevents the flow of water and accumulates it in a reservoirof water and accumulates it in a reservoir Karakaya Dam/DiyarbakırKarakaya Dam/Diyarbakır Atatürk Dam/ŞanlıurfaAtatürk Dam/Şanlıurfa
  • 29. Needs for Dam ConstructionNeeds for Dam Construction 1.1. Drinking and domestic water supplyDrinking and domestic water supply 2.2. Flood controlFlood control 3.3. IrrigationIrrigation 4.4. Industrial water supplyIndustrial water supply 5.5. Hydroelectric energy productionHydroelectric energy production 6.6. Retention and control of sedimentsRetention and control of sediments and Inland navigation, Improvement of water quality,and Inland navigation, Improvement of water quality, Fish Farming, Recreation facilitiesFish Farming, Recreation facilities
  • 30. BREAKDOWNBREAKDOWN byby PURPOSEPURPOSE ofof DAMSDAMS inin EUROPEEUROPE
  • 31. Dams and Development - Report of the World Commission on Dams CLASSIFICATION OF DAMSCLASSIFICATION OF DAMS
  • 32. ACCORDING to the SIZE of theACCORDING to the SIZE of the DAMDAM 1.1. Large (Big) damLarge (Big) dam 2.2. Small damSmall dam • International Commision on Large Dams, (ICOLD) assumes a damInternational Commision on Large Dams, (ICOLD) assumes a dam as big when its height is bigger than 15m.as big when its height is bigger than 15m. • If the height of the dam is between 10m and 15m and matches theIf the height of the dam is between 10m and 15m and matches the following criteria, then ICOLD accepts the dam as big:following criteria, then ICOLD accepts the dam as big: • If the crest length is bigger than 500mIf the crest length is bigger than 500m • If the reservoir capacity is larger than 1 million mIf the reservoir capacity is larger than 1 million m33 • If the flood discharge is more than 2000 mIf the flood discharge is more than 2000 m33 /s/s • If there are some difficulties in the construction of foundationIf there are some difficulties in the construction of foundation
  • 33. ACCORDING to HEIGHT ofACCORDING to HEIGHT of DAMDAM • High Dam or Large DamHigh Dam or Large Dam • If the height of the dam is bigger than 100mIf the height of the dam is bigger than 100m • Medium DamMedium Dam • If the height of the dam is between 50m andIf the height of the dam is between 50m and 100m100m • Low Dam or Small DamLow Dam or Small Dam • If the height of the dam is lower than 50mIf the height of the dam is lower than 50m
  • 34. ACCORDING to the STATICALACCORDING to the STATICAL DESIGN of DAM BODYDESIGN of DAM BODY • Gravity Dams (Sarıyar, Çubuk I, Kemer, Sır IIGravity Dams (Sarıyar, Çubuk I, Kemer, Sır II Karacaören II)Karacaören II) • Arch Dams (Gökçekaya, Karakaya,Arch Dams (Gökçekaya, Karakaya, Oymapınar, Gezende)Oymapınar, Gezende) • Butress Dams (Elmalı II)Butress Dams (Elmalı II) • Embankment Dams (Atatürk, Seyhan, Aslantaş)Embankment Dams (Atatürk, Seyhan, Aslantaş) • Composite Dams (Keban)Composite Dams (Keban)
  • 35. GRAVITY DAMSGRAVITY DAMS  Gravity DamsGravity Dams use their triangular shape and the sheer weightuse their triangular shape and the sheer weight of their rock and concrete structure to hold back the water inof their rock and concrete structure to hold back the water in the reservoir.the reservoir. Sarıyar Dam – Sakarya River;Sarıyar Dam – Sakarya River; Height= 90 mHeight= 90 m Reservoir Capacity= 1.9 billion mReservoir Capacity= 1.9 billion m33
  • 36. ARCH DAMSARCH DAMS  Arch DamsArch Dams utiliutilizze the strength of an arch to displace the loade the strength of an arch to displace the load of water behind it onto the rock walls that it is built into.of water behind it onto the rock walls that it is built into. Karakaya Dam – Fırat River;Karakaya Dam – Fırat River; Height= 173 mHeight= 173 m Reservoir Capacity= 9,5 billion mReservoir Capacity= 9,5 billion m33
  • 37. BUTRESS DAMSBUTRESS DAMS  Buttress DamsButtress Dams use multiple reinforced columns to support ause multiple reinforced columns to support a dam that has a relatively thin structure. Because of this,dam that has a relatively thin structure. Because of this, these dams often use half as much concrete as gravity damsthese dams often use half as much concrete as gravity dams Elmalı II – Göksu River;Elmalı II – Göksu River; Height= 42.5 mHeight= 42.5 m Reservoir Capacity= 10 million mReservoir Capacity= 10 million m33
  • 38. EMBANKMENT DAMSEMBANKMENT DAMS (Rock Fill or Earth Fill Dams)(Rock Fill or Earth Fill Dams) • They are mostly composed of natural materials suchThey are mostly composed of natural materials such as, clay, sand, gravel etc...as, clay, sand, gravel etc... • Impervious core is placed in the middle of theImpervious core is placed in the middle of the embankment bodyembankment body • Generally riprap is used to control erosionGenerally riprap is used to control erosion Atatürk Dam – Fırat River;Atatürk Dam – Fırat River; Height= 169 m;Height= 169 m; Reservoir Capacity= 48,7 billion mReservoir Capacity= 48,7 billion m33
  • 39. COMPOSITE DAMSCOMPOSITE DAMS • Composite dams are combinations of one or more damComposite dams are combinations of one or more dam types. Most often a large section of a dam will be eithertypes. Most often a large section of a dam will be either an embankment or gravity dam, with the sectionan embankment or gravity dam, with the section responsible for power generation being a buttress orresponsible for power generation being a buttress or arch.arch. Keban Dam – Fırat River;Keban Dam – Fırat River; Height= 163 m;Height= 163 m; Reservoir Capacity= 31 billion mReservoir Capacity= 31 billion m33 Gravity & Rock FillGravity & Rock Fill
  • 40. Dams and Development - Report of the World Commission on Dams ENGINEERING GEOLOGICALENGINEERING GEOLOGICAL STUDIES for DAM CONSTRUCTIONSTUDIES for DAM CONSTRUCTION
  • 41. 1. RECONNAISSANCE STUDY1. RECONNAISSANCE STUDY 1.1. Evaluation of the data having at archives of MTA, DSI, EIE,Evaluation of the data having at archives of MTA, DSI, EIE, Universities,......etcUniversities,......etc 2.2. Field investigation for limited time (Reconnaissance Study)Field investigation for limited time (Reconnaissance Study) 3.3. Some maps in small scale, for example 1/25.000 or 1/50.000Some maps in small scale, for example 1/25.000 or 1/50.000 4.4. Some hydraulic data aboutSome hydraulic data about a.a. BasinBasin b.b. Precipitation areaPrecipitation area c.c. Runoff, maximum discharge {Q=R/t (mRunoff, maximum discharge {Q=R/t (m33 /s)}/s)} d.d. Modulus of Runoff (R/t/mModulus of Runoff (R/t/m22 ~ R/t/km~ R/t/km22 )) 5.5. Some approach to the reservoir area, dam site and type of damSome approach to the reservoir area, dam site and type of dam and height of dam...etcand height of dam...etc 6.6. Photogeological studiesPhotogeological studies 7.7. A preliminary reportA preliminary report
  • 42. 2. PRELIMINARY STUDIES at the2. PRELIMINARY STUDIES at the RESERVOIR AREA and DAM SITERESERVOIR AREA and DAM SITE 1.1. Dam site investigationsDam site investigations 1. Location of dam axis1. Location of dam axis 2. Location of diversion tunnel2. Location of diversion tunnel 3. Location of spillway3. Location of spillway 4. Location of powerhouse...etc4. Location of powerhouse...etc 1.1. Geological studiesGeological studies 2.2. Geophysical surveyingGeophysical surveying 3.3. Underground investigationsUnderground investigations 1. Boreholes1. Boreholes 2. Investigation galleries2. Investigation galleries 3. Pitholes3. Pitholes 1.1. Surveying for materialsSurveying for materials 1. Field surveying1. Field surveying 2. Laboratory tests2. Laboratory tests
  • 43. 6.6. Slope stability investigationsSlope stability investigations 7.7. Earthquake hazard & risk analysisEarthquake hazard & risk analysis 8.8. Environmental studiesEnvironmental studies 9.9. Leakage possibilities from reservoir areaLeakage possibilities from reservoir area 10.10. Leakage possibilities from dam siteLeakage possibilities from dam site 11.11. Erosion, sedimentation & siltationErosion, sedimentation & siltation
  • 44. DETAILED INVESTIGATION atDETAILED INVESTIGATION at DAM SITEDAM SITE 1.1. Topographic surveyingsTopographic surveyings 2.2. Geological mappingsGeological mappings 1/5000 – 1/1000 or 1/5001/5000 – 1/1000 or 1/500 3.3. Underground explorationsUnderground explorations Boreholes, adits....etcBoreholes, adits....etc 4.4. Hydrogeological studiesHydrogeological studies 5.5. Slope stability analysisSlope stability analysis
  • 45. FACTORS AFFECTING to the DAMFACTORS AFFECTING to the DAM TYPE SELECTIONTYPE SELECTION • TopographyTopography • GeologyGeology • Bearing capacity of the underlying soilBearing capacity of the underlying soil • Foundation settlementsFoundation settlements • Permeability of the foundation soilPermeability of the foundation soil • Material availabilityMaterial availability • Spillway positionSpillway position • EarthquakesEarthquakes • SafetySafety • HeightHeight • Aesthetic viewAesthetic view • Qualified labourQualified labour • CostCost
  • 46. FACTORS AFFECTING to theFACTORS AFFECTING to the PLACE of the DAM AXISPLACE of the DAM AXIS • TopographyTopography • GeologyGeology • MaterialsMaterials • Spillway location availabilitySpillway location availability • DerivationDerivation • Sediments in the flowing waterSediments in the flowing water • Water qualityWater quality • Expropriation costsExpropriation costs • Earthquake possibilityEarthquake possibility • Downstream water rightsDownstream water rights
  • 47. RIVER BASINS in TURKEYRIVER BASINS in TURKEY Turkey has been separated into 26 main river basins for theTurkey has been separated into 26 main river basins for the hydrological studies.hydrological studies.
  • 48. Dams and Development - Report of the World Commission on Dams ENVIRONMENTALENVIRONMENTAL IMPACTS OF DAMSIMPACTS OF DAMS
  • 49. ENVIRONMENTAL IMPACTS ofENVIRONMENTAL IMPACTS of CONSTRUCTION PHASE of DAMSCONSTRUCTION PHASE of DAMS • River pollutionRiver pollution • ErosionErosion • Loss of aesthetic viewLoss of aesthetic view • Air pollutionAir pollution • Noise pollutionNoise pollution • DustDust
  • 50. ENVIRONMENTAL IMPACTS ofENVIRONMENTAL IMPACTS of RESERVOIRSRESERVOIRS • Loss of landLoss of land • Habitat Destruction :Habitat Destruction : • The area that is covered by the reservoir is destroyed, killingThe area that is covered by the reservoir is destroyed, killing whatever habitat existed there beforehand.whatever habitat existed there beforehand. • Loss of archeological and histrorical placesLoss of archeological and histrorical places • Loss of mineral depositsLoss of mineral deposits • Loss of special geological formationsLoss of special geological formations • Aesthetic view reductionAesthetic view reduction • SedimentationSedimentation • Change in river flow regime and flood effectsChange in river flow regime and flood effects • Reservoir induced seismicityReservoir induced seismicity • Change in climate and plant speciesChange in climate and plant species
  • 51. EFFECTS of DAMS to WATEREFFECTS of DAMS to WATER QUALITYQUALITY • Change in temperatureChange in temperature • TurbidityTurbidity • Dissolved gases in the waterDissolved gases in the water • Water discharged from the spillway contains 110-120%Water discharged from the spillway contains 110-120% saturated nitrogen. This amount may be destructive forsaturated nitrogen. This amount may be destructive for fish life.fish life. • EutrophicationEutrophication • It means increase in vegetation. If moss and other plantsIt means increase in vegetation. If moss and other plants exist in water, quality of that water gets worse.exist in water, quality of that water gets worse.
  • 52. Dams and Development - Report of the World Commission on Dams SOME DAMS from SPACESOME DAMS from SPACE
  • 53. Dams and Development - Report of the World Commission on Dams Why a World Commission on Dams ?Why a World Commission on Dams ? In response to escalating conflictsIn response to escalating conflicts over the role of dams inover the role of dams in development, all constituentsdevelopment, all constituents came together to establishcame together to establish the Commissionthe Commission
  • 54. Dam projects increasingly questioned …Dam projects increasingly questioned … • affected populationsaffected populations strongly oppose damsstrongly oppose dams • proponents point toproponents point to urgent developmenturgent development demandsdemands • opponents point toopponents point to adverse impactsadverse impacts • uprisings againstuprisings against globalizationglobalization • little space forlittle space for constructive dialogueconstructive dialogue
  • 55. Purposes of large damsPurposes of large dams • Hydropower • Irrigation • Water supply • Flood control • Multipurpose
  • 56. Types of large damsTypes of large dams • Reservoir-type storage – impound water behind the dam for seasonal,annual and, in some cases, multi- annual storage and regulation of the river. • Run-of-river dams – weirs and barrages, and diversion dams create a hydraulic head in the river to divert some portion of the river flows to a canal or power station.
  • 57. Dams and Development - Report of the World Commission on Dams By 1925, falling water generated 40% of electricBy 1925, falling water generated 40% of electric power. Today, large dams (15 m +) generate 19%power. Today, large dams (15 m +) generate 19% of electricity.of electricity. Hydro production capacity has grown 15 x.Hydro production capacity has grown 15 x. Fossil fuel use has risen so rapidly that currently, hydroelectricFossil fuel use has risen so rapidly that currently, hydroelectric only supplies one-quarter of electrical generation.only supplies one-quarter of electrical generation. One-third of world’s countries rely on hydropower forOne-third of world’s countries rely on hydropower for more than half their electricity supply.more than half their electricity supply. HydropowerHydropower
  • 58. Irrigation: The Aral SeaIrrigation: The Aral Sea • Once the 4th largest inland body of water in the world A series of dams was built to irrigate cotton. • Aral Sea reduced to about 25% of its 1960 volume, quadrupled the salinity of the lake and wiped out the fishery. Pollutants became airborne as dust, causing significant local health problems. • The environmental damage caused has been estimated at $1.25 -$2.5 billion a year.
  • 59. Water suppliesWater supplies • freshwater withdrawals doubled in 50 yearsfreshwater withdrawals doubled in 50 years • 1 billion lack freshwater &1 billion lack freshwater & 2 billion lack electricity2 billion lack electricity • competition for water increasingcompetition for water increasing • aquatic ecosystems are decliningaquatic ecosystems are declining & wetlands have been lost& wetlands have been lost
  • 60. Major investments …Major investments … • 45,000 large dams worldwide45,000 large dams worldwide • 2 dams commissioned2 dams commissioned per day in1970sper day in1970s • total investment exceedstotal investment exceeds $2 trillion$2 trillion • $40 billion expenditure$40 billion expenditure per year at peakper year at peak • estimated 40 – 80 million people displacedestimated 40 – 80 million people displaced • flow in 60% of world’s rivers affectedflow in 60% of world’s rivers affected 2 000 0 4 000 6 000 Number Of Dams 1900 1990s
  • 61. Dams and Development - Report of the World Commission on Dams Dam Drawbacks to Human CommunitiesDam Drawbacks to Human Communities Human DisplacementHuman Displacement Flooding of Cultural SitesFlooding of Cultural Sites (Archeological and Modern)(Archeological and Modern) Social disruptionSocial disruption Cost overrunsCost overruns Socio-economic centralizationSocio-economic centralization
  • 62. Dams and Development - Report of the World Commission on Dams Dam Drawbacks to the EnvironmentDam Drawbacks to the Environment Ecosystem DestructionEcosystem Destruction Fish Blockage and Wildlife LossesFish Blockage and Wildlife Losses Large-Scale Flooding Due to Dam FailuresLarge-Scale Flooding Due to Dam Failures Sedimentation and SalinitySedimentation and Salinity Herbicide and Other Toxic ContaminationHerbicide and Other Toxic Contamination Evaporative LossesEvaporative Losses Nutrient Flow RetardationNutrient Flow Retardation Release of greenhouse gassesRelease of greenhouse gasses
  • 63. Dams and Development - Report of the World Commission on Dams Dam AlternativesDam Alternatives Low-Head HydropowerLow-Head Hydropower - Extract energy from small- Extract energy from small headwater dams.headwater dams. Run-of-River FlowRun-of-River Flow - Submerged directly in stream- Submerged directly in stream and usually do not require dam or diversionand usually do not require dam or diversion structure.structure. Micro-Hydro GeneratorsMicro-Hydro Generators - Small versions designed- Small versions designed to supply power to single homes.to supply power to single homes.
  • 64. WCD FindingsWCD Findings • Dams have made a significant contributionDams have made a significant contribution • A considerable number have fallen below targetsA considerable number have fallen below targets • EEconomic and financialconomic and financial under-under-performanceperformance • Significant impacts on riverineSignificant impacts on riverine && downstream ecosystemsdownstream ecosystems • Heavy toll on affected communitiesHeavy toll on affected communities • AAlternativeslternatives oftenoften existexist • Lack ofLack of compliancecompliance
  • 65. Significant contribution…Significant contribution… • 19 percent of electricity19 percent of electricity from hydropowerfrom hydropower –– more than 50% in 63more than 50% in 63 countriescountries • dams support 30-40% of irrigateddams support 30-40% of irrigated areaarea && 12-16% of global food12-16% of global food productionproduction • 12% of all dams have a12% of all dams have a water supply functionwater supply function • 75 countries have dams for75 countries have dams for flood controlflood control Dams andDams and DDevelopmentevelopment -- RReport of theeport of the WWorldorld CCommisommisssion onion on DDamsams
  • 66. • irrigationirrigation – almost half have under-performed– almost half have under-performed ……opportunities for efficiency gainsopportunities for efficiency gains • hydropowerhydropower – on average met expectations but– on average met expectations but considerable variabilityconsiderable variability • flood controlflood control – dams have attenuated floods, but some– dams have attenuated floods, but some increasedincreased vulnerabilityvulnerability • physical sustainabilityphysical sustainability – safety– safety improving,improving, but dams arebut dams are aging and costs risingaging and costs rising ……loss of storage, 0loss of storage, 0.5.5 to 1.0%to 1.0% per yearper year Predicted vs actual generation TWh Kariba Predicted 1960 2000 0 10 6 Considerable number have fallen below targets…Considerable number have fallen below targets… Actual
  • 67. Economic & financial under-performance…Economic & financial under-performance… • average cost overruns ofaverage cost overruns of over 50%over 50% • 50% in survey with one50% in survey with one year or more delayyear or more delay • cost recovery incost recovery in hydropower but nothydropower but not irrigationirrigation • poor economic andpoor economic and financial results fromfinancial results from irrigationirrigation • mixed results formixed results for hydropowerhydropower
  • 68. Significant impacts on riverineSignificant impacts on riverine & downstream ecosystems…& downstream ecosystems… • lloss of riverineoss of riverine && terrestrial biodiversityterrestrial biodiversity • adverseadverse impactsimpacts onon livelihoods in floodplainslivelihoods in floodplains • 67% of ecosystem changes67% of ecosystem changes in survey are negativein survey are negative • ppoor record of ecosystem mitigationoor record of ecosystem mitigation • ssome reservoirs have created habitats forome reservoirs have created habitats for biodiversitybiodiversity • rreservoirs emit green-house gaseseservoirs emit green-house gases
  • 69. Heavy toll on affected communities…Heavy toll on affected communities… • estimated 40-80 million physically displacedestimated 40-80 million physically displaced • significant number of othersignificant number of otherss affectedaffected • failure to adequatelyfailure to adequately recogniserecognise && respond torespond to those affectedthose affected • negative impacts fallnegative impacts fall disproportionately ondisproportionately on disadvantageddisadvantaged • inequityinequity isis notnot addressedaddressed inin ‘balance sheet’‘balance sheet’ approachapproach
  • 70. Alternatives often exist…Alternatives often exist… • reduce demand by increasingreduce demand by increasing end-use efficiencyend-use efficiency • defer new supply by enhancing supplydefer new supply by enhancing supply && conveyance efficiencyconveyance efficiency • extend life and performance through improvedextend life and performance through improved landland && waterwater managementmanagement • promote alternative supply options, includingpromote alternative supply options, including small-scalesmall-scale && locally appropriate approacheslocally appropriate approaches Dams andDams and DDevelopmentevelopment -- RReport of theeport of the WWorldorld CCommisommisssion onion on DDamsams
  • 71. Lack of compliance…Lack of compliance… • wweak regulatory frameworkseak regulatory frameworks && lack of enforcementlack of enforcement • llittle public participationittle public participation && scrutinyscrutiny • ttop down decision-making, often politicallyop down decision-making, often politically motivatedmotivated • ppast conflicts remain unresolved with no legalast conflicts remain unresolved with no legal recourserecourse • vvested interests in favour of large infrastructureested interests in favour of large infrastructure • nno incentives or sanctionso incentives or sanctions
  • 72. Dams and Development - Report of the World Commission on Dams What did the Commission find from theWhat did the Commission find from the knowledge base ?knowledge base ? Dams have delivered considerableDams have delivered considerable benefitsbenefits In too many cases the price paid toIn too many cases the price paid to secure those benefitssecure those benefits hashas been unacceptablebeen unacceptable andand often unnecessaryoften unnecessary
  • 73. Unprecedented response to the controversy …Unprecedented response to the controversy … • WCD created through unanimous agreementWCD created through unanimous agreement • broad based mandate to review development effectiveness &broad based mandate to review development effectiveness & assess alternatives…assess alternatives… …… and develop internationally acceptable criteriaand develop internationally acceptable criteria and guidelinesand guidelines • address global problems through local understandingaddress global problems through local understanding • WCD’s authority and credibility rests on the diversity of theWCD’s authority and credibility rests on the diversity of the Commissioners which was a guiding theme throughout its inclusive,Commissioners which was a guiding theme throughout its inclusive, transparent and participatory work program.transparent and participatory work program.
  • 74. Inclusive, Participatory & Transparent …Inclusive, Participatory & Transparent … • full range of perspectives –full range of perspectives – civil society to governments,civil society to governments, private sector to NGOs, financiers to foundationsprivate sector to NGOs, financiers to foundations • outreach through work program and networksoutreach through work program and networks • extensive review processextensive review process • WCD Forum as a reference pointWCD Forum as a reference point • draft studies on website www.dams.orgdraft studies on website www.dams.org
  • 75. The Way ForwardThe Way Forward • Move beyond the simpleMove beyond the simple “balance –sheet approach”“balance –sheet approach”…… ……to sto shared values, objectiveshared values, objectives andand goalsgoals • InternationalInternationallyly accepted norms are basisaccepted norms are basis for WCD recommendationsfor WCD recommendations • Adopt a rightsAdopt a rights andand risks approachrisks approach • Define whose rightsDefine whose rights andand what riskswhat risks
  • 76. Move beyond the simple “balance-sheet”Move beyond the simple “balance-sheet” approach that…approach that… • trades off lossestrades off losses andand gains between groupsgains between groups • impoverishesimpoverishes somesome peoplepeople • excludes people and limitexcludes people and limitss awarenessawareness • overlooks sustainability aspectsoverlooks sustainability aspects • induces conflictinduces conflict andand higher costshigher costs Dams andDams and DDevelopmentevelopment -- RReport of theeport of the WWorldorld CCommisommisssion onion on DDamsams
  • 77. Towards shared values, objectives & goals…Towards shared values, objectives & goals… • equityequity • efficiencyefficiency • participatory decision-makingparticipatory decision-making • sustainabilitysustainability • AccountabilityAccountability
  • 78. Define whose rights & what risks…Define whose rights & what risks… RRisksisks • Move beyond considering voluntary risk takersMove beyond considering voluntary risk takers to include involuntary risk bearersto include involuntary risk bearers RightsRights • No party’s rights should extinguish another’sNo party’s rights should extinguish another’s • Where rights compete – negotiated agreementsWhere rights compete – negotiated agreements are neededare needed
  • 79. Dams and Development - Report of the World Commission on Dams Turning Conflict Into ConsensusTurning Conflict Into Consensus • Gain public acceptanceGain public acceptance • Assess optionsAssess options • Address existing damsAddress existing dams • Sustain rivers and livelihoodsSustain rivers and livelihoods • Recognize entitlements and share benefitsRecognize entitlements and share benefits • Ensure complianceEnsure compliance • Share rivers across boundariesShare rivers across boundaries Seven Strategic prioritiesSeven Strategic priorities
  • 80. Gaining public acceptanceGaining public acceptance…… • dams affect existing rightsdams affect existing rights && createcreate wide range of riskswide range of risks • opportunities exist for achieving a highopportunities exist for achieving a higherer levellevel ofof equityequity • recognise rights of indigenousrecognise rights of indigenous && tribal peoplestribal peoples • achieve outcomes through binding formal agreementsachieve outcomes through binding formal agreements Dams andDams and DDevelopmentevelopment -- RReport of theeport of the WWorldorld CCommisommisssion onion on DDamsams
  • 81. • failure to adequately definefailure to adequately define needsneeds && assess options led toassess options led to disputedispute • an early and open examinationan early and open examination of optionsof options can avoid poorcan avoid poor projectsprojects • raise the significance of socialraise the significance of social && environmental aspectsenvironmental aspects • increase the effectiveness ofincrease the effectiveness of existingexisting systems as a prioritysystems as a priority Comprehensive optionsComprehensive options assessmentassessment…… Dams andDams and DDevelopmentevelopment -- RReport of theeport of the WWorldorld CCommisommisssion onion on DDamsams
  • 82. Address existing damsAddress existing dams…… • most dams that will operate in themost dams that will operate in the 2121stst century already existcentury already exist • considerable scope exists forconsiderable scope exists for improving benefitsimproving benefits • remedy outstanding social issuesremedy outstanding social issues ……enhance mitigation, restorationenhance mitigation, restoration && enhancement of ecosystemsenhancement of ecosystems • use licenuse licensses to formalizees to formalize operating agreementsoperating agreements
  • 83. Sustain rivers and livelihoodsSustain rivers and livelihoods…… • rivers supportrivers support millions ofmillions of livelihoodslivelihoods • dams cause significant and oftendams cause significant and often irreversible effects on ecosystemsirreversible effects on ecosystems • valuevalue rivers,rivers, ecosystemsecosystems & endangered& endangered speciesspecies • emphasise avoidanceemphasise avoidance of impactsof impacts • maintain ecosystemmaintain ecosystem integrity throughintegrity through environmental flowsenvironmental flows
  • 84. Recognize entitlementsRecognize entitlements && share benefitsshare benefits …… • manymany peoplepeople displaced - manydisplaced - many moremore ununrecognisedrecognised • includingincluding thosethose whowho depend on adepend on a river’s resourcesriver’s resources • recognise rights and assess risksrecognise rights and assess risks as a basis for negotiationsas a basis for negotiations • agree legally enforceableagree legally enforceable entitlementsentitlements • adverselyadversely affected peopleaffected people becomebecome first among beneficiariesfirst among beneficiaries
  • 85. Ensure complianceEnsure compliance …… • many policies and guidelines exist..many policies and guidelines exist.. • but often a failure to fulfill obligationsbut often a failure to fulfill obligations • need a compliance plan covering all commitmentsneed a compliance plan covering all commitments toto people and the environmentpeople and the environment • introduce initiatives to reduce corruptionintroduce initiatives to reduce corruption • develop incentive framework for compliancedevelop incentive framework for compliance
  • 86. Share rivers across boundariesShare rivers across boundaries…… • conflicts over transboundary rivers dueconflicts over transboundary rivers due toto power imbalancepower imbalance • experience suggests disputes can be resolvedexperience suggests disputes can be resolved • endorse the UN Convention principlesendorse the UN Convention principles • go beyond sharing water - to sharing the benefitsgo beyond sharing water - to sharing the benefits • encourageencourage consistent policies for financingconsistent policies for financing agenciesagencies Dams andDams and DDevelopmentevelopment -- RReport of theeport of the WWorldorld CCommisommisssion onion on DDamsams
  • 87. Dams in the pipeline - it’s not too lateDams in the pipeline - it’s not too late FeasibilityFeasibility - assess all options- assess all options - gain public acceptance- gain public acceptance DesignDesign - prepare Compliance Plan- prepare Compliance Plan - contractualize benefit sharing- contractualize benefit sharing - determine environmental flow- determine environmental flow ConstructionConstruction -- fformalize commitmentsormalize commitments Dams andDams and DDevelopmentevelopment -- RReport of theeport of the WWorldorld CCommisommisssion onion on DDamsams
  • 88. Dams and Development - Report of the World Commission on Dams BY :- SAGAR MANDALBY :- SAGAR MANDAL X-AX-A

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