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Dams and Development - Report of the World Commission on Dams

P.P.TP.P.TONON

DamsDams

Dams and reservoirsDams and reservoirs

ReservoirsReservoirs• Site selectionSite selection• Leakage from Leakage from

reservoirsreservoirs• SedimentationSedimentation• Stability: effect of Stability: effect of

raised WTraised WT

DamsDams• TypesTypes• Forces on a damForces on a dam• Geology and dam Geology and dam

sitessites• Rock types and damsRock types and dams• Dams on soilsDams on soils• Ground improvementGround improvement

Dams and reservoirs - literatureDams and reservoirs - literature

• Bell F.G., Engineering geology and Bell F.G., Engineering geology and geotechnics geotechnics – Ch 6 (Reservoirs)Ch 6 (Reservoirs)– Ch 7 (Dams)Ch 7 (Dams)

• Blyth F.G.H. and de Freitas M.H., A geology Blyth F.G.H. and de Freitas M.H., A geology for engineersfor engineers– Ch 14 (Reservoirs and dams)Ch 14 (Reservoirs and dams)

Reservoirs: purposeReservoirs: purpose

• Water storageWater storage

• Flood preventionFlood prevention

• Power Power

Reservoirs: site selectionReservoirs: site selection

• Hydrological considerationsHydrological considerations

• Fundamental controlsFundamental controls– topographytopography– climateclimate– geologygeology

Water Water addedadded

Net amount of water Net amount of water available for storageavailable for storage

Water Water subtractedsubtracted++

Rainfall in river Rainfall in river basinbasin

InfiltrationInfiltrationEvaporationEvaporationTranspirationTranspiration

RunoffRunoff

Reservoirs: leakageReservoirs: leakage

Water Water addedadded

Leakage from Leakage from reservoirreservoir

Water Water subtractedsubtracted--

Rainfall in Rainfall in river basinriver basin

InfiltrationInfiltrationEvaporationEvaporationTranspirationTranspiration

Net amount of water Net amount of water available for storageavailable for storage

RunoffRunoff

--

1. Dam bypass1. Dam bypass2. Water table effects2. Water table effects

Leakage via subsurface bypass due to siphon effectLeakage via subsurface bypass due to siphon effect

Devonian strataDevonian strata

Dev

onia

n st

rata

Dev

onia

n st

rata

Devonian strataDevonian strata

Dol-y-gaer damDol-y-gaer dam

Carboniferous strata: Carboniferous strata:

Subsurface water flowSubsurface water flow

reservoir levelreservoir level

fracture and dissolution fracture and dissolution flow routesflow routes


Leakage buried channels beneath driftLeakage buried channels beneath drift

50 km50 km

Modern river/valleyModern river/valley

Ancient river/valleyAncient river/valley

R DracR Drac

Sautet Sautet dam and dam and reservoirreservoir

Bypass of reservoir in driftBypass of reservoir in drift


land surface

land surfacewater table

water table

riverriver

reservoirreservoir

beforebefore

afterafter

water table dividewater table divide

Leakage to next valleyLeakage to next valley

Bedrock with a water Bedrock with a water table and finite table and finite

permeabilitypermeability

new new water water tabletable

Reservoirs: water table Reservoirs: water table leakage-1leakage-1

Land surface

Land surface

riverriver

beforebefore

Bedrock with low Bedrock with low permeability: aquicludepermeability: aquiclude

High High permeabilitypermeability

layerlayer

Water table in aquiferWater table in aquifer

reservoirreservoirafterafter

High High permeabilitypermeability

layerlayer

Modified water table in aquiferModified water table in aquifer

Leakage to next valleyLeakage to next valley

Reservoirs: water table Reservoirs: water table leakage-2leakage-2

Reservoirs: Reservoirs: sedimentationsedimentation

• World’s largest dam; World’s largest dam; 180m tall, 2km wide180m tall, 2km wide– 84% sediment in 84% sediment in

rainy season (june-rainy season (june-sept)sept)

– drawdown and drawdown and sediment sluicing sediment sluicing during this periodduring this period

BeforeBefore

Water tableWater tableriverriver

After - 1After - 1

reservoirreservoirRaised water tableRaised water table

After - 2After - 2

reservoirreservoirFailure and Failure and slumping slumping

due to due to weakened weakened rock massrock mass

Reservoirs: raised water Reservoirs: raised water tabletable

Viaont dam disaster, ItalyViaont dam disaster, Italy

Normal stressNormal stress nn

Sh

ear

stre

ssS

hea

r st

ress

ss

1,WT1,WT3,3, WTWT

UnstableUnstable

StableStable

1133

ss = = c +c + . . ((nn - p)- p)

p = pore fluid pressurep = pore fluid pressurenn – p = effective stress– p = effective stress

Raising water tableRaising water table

Reservoirs: raised water Reservoirs: raised water tabletable

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 and Dispersed 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 and floorHuge stresses imposed on valley walls and floor

• Earth dams: bank or earth or rock with Earth dams: bank or earth or rock with impermeable coreimpermeable core– Core of clay or concrete, extended below groundCore of clay or concrete, extended below ground– Sand or gravel drains built to cut fluid pressureSand or gravel drains built to cut fluid pressure– Low stress applied to valley floor and wallsLow stress applied to valley floor and walls

Types of damTypes of dam

ArchArch

GravityGravity

ButtressButtress

Embankment Embankment or Earthor Earth

Emosson Dam, SwitzerlandEmosson Dam, Switzerland

The Vaiont dam todayThe Vaiont dam today

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 spillway overflow of water (controlled by spillway

channels)channels)– earthquakes and tremors earthquakes and tremors – ice/freezingice/freezing

Dam failure: earthquakeDam failure: earthquake

Dam failure: asteroidsDam failure: asteroids

Dam failure: bombsDam failure: bombs

Poor geological characterisation of dam foundation Poor 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

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 2 2 0.07 0.07 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

groutsgroutschemical treatmentschemical treatments

thermal treatmentthermal treatmentgrou

nd s

tren

gthe

ning

grou

nd s

tren

gthe

ning

Dams: ground improvementDams: ground improvement

Dams: ground improvementDams: ground improvement• 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: insert sand 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 ground material injected into the ground

• Chemical treatmentsChemical treatments– react solutions injected into ground. React with material to alter properties. NaCl react 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 thermal by burning petroleum under pressure in subsurface – causes thermal metamorphism - hardens ground and cuts porositymetamorphism - hardens ground and cuts porosity

Injected Injected grout curtaingrout curtain

Pre-stressed Pre-stressed anchorsanchors

DrainDrain

Apron drains (to Apron drains (to individual aquifers)individual aquifers)

Excavation Excavation to rockto rock

RegolithRegolith

ReservoirReservoir

Rip

rap

to k

ill

Rip

rap

to k

ill

wav

e en

ergy

wav

e en

ergy

Hard face to damHard face to dam

Aquifer layersAquifer layers

Aquiclude layersAquiclude layers

Core and rear of damCore and rear of dam

• In Turkey, 536 large dams have been built and In Turkey, 536 large dams have been built and being operated. On the other hand, Small being operated. On the other hand, Small Hydraulic Works Department has built 42 small Hydraulic Works Department has built 42 small dams. dams.

• Here, 50 storage facilities that are not considered Here, 50 storage facilities that are not considered as dam due to their low heights (<15m) and low as 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 and By now, construction of 100 dams and hydroelectric powerplants is going on.hydroelectric powerplants is going on.

DefinitionDefinition

• A dam is a structure which prevents the flow A 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/Diyarbakır Karakaya Dam/Diyarbakır Atatürk Dam/Şanlıurfa Atatürk Dam/Şanlıurfa

Needs for Dam ConstructionNeeds for Dam Construction

1.1. Drinking and domestic water supplyDrinking and domestic water supply2.2. Flood controlFlood control3.3. IrrigationIrrigation4.4. Industrial water supplyIndustrial water supply5.5. Hydroelectric energy productionHydroelectric energy production6.6. 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

BREAKDOWNBREAKDOWN byby PURPOSE PURPOSE of of DAMSDAMS inin EUROPEEUROPE


CLASSIFICATION OF DAMSCLASSIFICATION OF DAMS

ACCORDING to the SIZE of the ACCORDING to the SIZE of the DAMDAM

1.1. Large (Big) damLarge (Big) dam2.2. Small damSmall dam

• International Commision on Large Dams, (ICOLD) assumes a dam International 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 the If 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

ACCORDING to HEIGHT of DAMACCORDING to HEIGHT of DAM

• 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 and If 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

ACCORDING to the STATICAL ACCORDING to the STATICAL DESIGN of DAM BODY DESIGN of DAM BODY

• Gravity Dams (Sarıyar, Çubuk I, Kemer, Sır II Gravity 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)

GRAVITY DAMSGRAVITY DAMS

Gravity DamsGravity Dams use their triangular shape and the sheer weight use their triangular shape and the sheer weight of their rock and concrete structure to hold back the water in of 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

ARCH DAMSARCH DAMS Arch DamsArch Dams utiliutilizze the strength of an arch to displace the load e 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

BUTRESS DAMSBUTRESS DAMS

Buttress DamsButtress Dams use multiple reinforced columns to support a use 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

EMBANKMENT DAMS EMBANKMENT DAMS (Rock Fill or Earth Fill Dams)(Rock Fill or Earth Fill Dams)

• They are mostly composed of natural materials such They 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 the Impervious 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

COMPOSITE DAMSCOMPOSITE DAMS• Composite dams are combinations of one or more dam Composite dams are combinations of one or more dam

types. Most often a large section of a dam will be either types. Most often a large section of a dam will be either an embankment or gravity dam, with the section an embankment or gravity dam, with the section responsible for power generation being a buttress or responsible 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


ENGINEERING GEOLOGICAL STUDIES ENGINEERING GEOLOGICAL STUDIES for DAM CONSTRUCTIONfor DAM CONSTRUCTION

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 1/50.0004.4. Some hydraulic data aboutSome hydraulic data about

a.a. BasinBasinb.b. Precipitation areaPrecipitation areac.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 dam Some approach to the reservoir area, dam site and type of dam and height of dam...etcand height of dam...etc

6.6. Photogeological studiesPhotogeological studies7.7. A preliminary reportA preliminary report

2. PRELIMINARY STUDIES at the 2. PRELIMINARY STUDIES at the RESERVOIR AREA and DAM SITERESERVOIR AREA and DAM SITE

1.1. Dam site investigationsDam site investigations1. Location of dam axis1. Location of dam axis2. Location of diversion tunnel2. Location of diversion tunnel3. Location of spillway3. Location of spillway4. Location of powerhouse...etc4. Location of powerhouse...etc

2.2. Geological studiesGeological studies3.3. Geophysical surveyingGeophysical surveying4.4. Underground investigationsUnderground investigations

1. Boreholes1. Boreholes2. Investigation galleries2. Investigation galleries3. Pitholes3. Pitholes

5.5. Surveying for materialsSurveying for materials1. Field surveying1. Field surveying2. Laboratory tests2. Laboratory tests

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

DETAILED INVESTIGATION at DAM DETAILED INVESTIGATION at DAM SITESITE

1.1. Topographic surveyingsTopographic surveyings

2.2. Geological mappings Geological mappings 1/5000 – 1/1000 or 1/5001/5000 – 1/1000 or 1/500

3.3. Underground explorations Underground explorations Boreholes, adits....etcBoreholes, adits....etc

4.4. Hydrogeological studiesHydrogeological studies

5.5. Slope stability analysisSlope stability analysis

FACTORS AFFECTING to the DAM FACTORS 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

FACTORS AFFECTING to the PLACE FACTORS AFFECTING to the PLACE of the DAM AXISof the DAM AXIS

• TopographyTopography• GeologyGeology• MaterialsMaterials• Spillway location availabilitySpillway location availability• Derivation Derivation • Sediments in the flowing waterSediments in the flowing water• Water qualityWater quality• Expropriation costsExpropriation costs• Earthquake possibilityEarthquake possibility• Downstream water rightsDownstream water rights

RIVER BASINS in TURKEYRIVER BASINS in TURKEYTurkey has been separated into 26 main river basins for the Turkey has been separated into 26 main river basins for the

hydrological studies.hydrological studies.


ENVIRONMENTAL IMPACTS OF ENVIRONMENTAL IMPACTS OF DAMSDAMS

ENVIRONMENTAL IMPACTS of ENVIRONMENTAL IMPACTS of CONSTRUCTION PHASE of DAMSCONSTRUCTION PHASE of DAMS

• River pollution River pollution

• ErosionErosion

• Loss of aesthetic view Loss of aesthetic view

• Air pollutionAir pollution

• Noise pollutionNoise pollution

• Dust Dust

ENVIRONMENTAL IMPACTS of ENVIRONMENTAL IMPACTS of RESERVOIRSRESERVOIRS

• Loss of landLoss of land• Habitat Destruction :Habitat Destruction :

• The area that is covered by the reservoir is destroyed, killing The 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

EFFECTS of DAMS to WATER EFFECTS 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 for saturated nitrogen. This amount may be destructive for fish life.fish life.

• EutrophicationEutrophication• It means increase in vegetation. If moss and other plants It 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.


SOME DAMS from SPACESOME DAMS from SPACE


Why a World Commission on Dams ?Why a World Commission on Dams ?

In response to escalating conflicts In response to escalating conflicts over the role of dams in over the role of dams in

development, all constituents development, all constituents came together to establish came together to establish

the Commission the Commission

Dam projects increasingly questioned …Dam projects increasingly questioned …

• affected populations affected populations strongly oppose damsstrongly oppose dams

• proponents point to urgent proponents point to urgent development demandsdevelopment demands

• opponents point to opponents point to adverse adverse impactsimpacts

• uprisings against uprisings against globalization globalization

• little space for little space for constructive dialogueconstructive dialogue

Purposes of large damsPurposes of large dams

• Hydropower

• Irrigation

• Water supply

• Flood control

• Multipurpose

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.


By 1925, falling water generated 40% of electric By 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, hydroelectric Fossil 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

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.

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 electricity 2 billion lack electricity

• competition for water increasingcompetition for water increasing

• aquatic ecosystems are declining aquatic ecosystems are declining & wetlands have been lost & wetlands have been lost

Major investments …Major investments …

• 45,000 large dams worldwide45,000 large dams worldwide

• 2 dams commissioned 2 dams commissioned per day in1970s per day in1970s

• total investment exceeds total investment exceeds $2 trillion $2 trillion

• $40 billion expenditure $40 billion expenditure per year at peak per 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 000Number Of Dams

19001990s


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


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


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 diversion and 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.

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 financial conomic and financial under-under-performanceperformance

• Significant impacts on riverine Significant impacts on riverine && downstream downstream ecosystemsecosystems

• Heavy toll on affected communitiesHeavy toll on affected communities

• AAlternatives lternatives oftenoften exist exist

• Lack ofLack of compliance compliance

Significant contribution…Significant contribution…

• 19 percent of electricity 19 percent of electricity from hydropowerfrom hydropower –– more than 50% in 63 countriesmore than 50% in 63 countries

• dams support 30-40% of irrigated dams support 30-40% of irrigated area area & & 12-16% of global food 12-16% 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 control flood control

Dams and Dams and DDevelopmentevelopment - - R Report of the eport of the WWorld orld CCommisommisssion on ion on DDamsams

• irrigationirrigation – almost half have under-performed – almost half have under-performed

… …opportunities for efficiency gains opportunities for efficiency gains

• hydropowerhydropower – on average met expectations but – on average met expectations but considerable variability considerable variability

• flood controlflood control – dams have attenuated floods, but some – dams have attenuated floods, but some increased increased vulnerability vulnerability

• physical sustainabilityphysical sustainability – safety – safety

improving,improving, but dams are but 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 generationTWh

Kariba

Predicted

1960 20000

10

6

Considerable number have fallen below targets…Considerable number have fallen below targets…

Actual

Economic & financial under-performance…Economic & financial under-performance…

• average cost overruns of average cost overruns of over 50% over 50%

• 50% in survey with one 50% in survey with one year or more delayyear or more delay

• cost recovery in cost recovery in hydropower but not hydropower but not irrigationirrigation

• poor economic and poor economic and financial results from financial results from irrigationirrigation

• mixed results for mixed results for hydropowerhydropower

Significant impacts on riverine Significant impacts on riverine & downstream ecosystems… & downstream ecosystems…

• lloss of riverine oss of riverine & & terrestrial biodiversityterrestrial biodiversity

• adverse adverse impactsimpacts on on livelihoods in floodplainslivelihoods in floodplains

• 67% of ecosystem changes 67% of ecosystem changes in survey are negativein survey are negative

• ppoor record of ecosystem mitigationoor record of ecosystem mitigation

• ssome reservoirs have created habitats for biodiversity ome reservoirs have created habitats for biodiversity

• rreservoirs emit green-house gaseseservoirs emit green-house gases

Heavy toll on affected communities…Heavy toll on affected communities…

• estimated 40-80 million physically displaced estimated 40-80 million physically displaced

• significant number of othersignificant number of otherss affected affected

• failure to adequately failure to adequately recognise recognise && respond to respond to those affectedthose affected

• negative impacts fall negative impacts fall disproportionately on disproportionately on disadvantageddisadvantaged

• inequity inequity is is not not addressedaddressed inin ‘balance sheet’ ‘balance sheet’ approachapproach

Alternatives often exist…Alternatives often exist…

• reduce demand by increasingreduce demand by increasing end-use efficiency end-use efficiency

• defer new supply by enhancing supply defer new supply by enhancing supply && conveyance efficiencyconveyance efficiency

• extend life and performance through improved extend life and performance through improved land land && water water managementmanagement

• promote alternative supply options, including promote alternative supply options, including small-scale small-scale && locally appropriate approaches locally appropriate approaches


Lack of compliance…Lack of compliance…

• wweak regulatory frameworks eak regulatory frameworks && lack of enforcement lack of enforcement

• llittle public participation ittle public participation && scrutiny scrutiny

• ttop down decision-making, often politically op down decision-making, often politically motivatedmotivated

• ppast conflicts remain unresolved with no legal ast 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


What did the Commission find from the knowledge What did the Commission find from the knowledge base ?base ?

Dams have delivered considerable Dams have delivered considerable benefits benefits

In too many cases the price paid to In too many cases the price paid to secure those benefitssecure those benefits has has

been unacceptable been unacceptable andand often unnecessary often unnecessary

Unprecedented response to the controversy …Unprecedented response to the controversy …

• WCD created through unanimous agreement WCD 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 criteria and develop internationally acceptable criteria and guidelines and guidelines

• address global problems through local understandingaddress global problems through local understanding

• WCD’s authority and credibility rests on the diversity of the WCD’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.

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

The Way ForwardThe Way Forward

• Move beyond the simple Move beyond the simple “balance –sheet approach”“balance –sheet approach”……

……to sto shared values, objectives hared values, objectives andand goals goals

• InternationalInternationallyly accepted norms are basis accepted norms are basis for WCD recommendationsfor WCD recommendations

• Adopt a rights Adopt a rights andand risks approach risks approach

• Define whose rights Define whose rights andand what risks what risks

Move beyond the simple “balance-sheet” Move beyond the simple “balance-sheet” approach that…approach that…

• trades off losses trades off losses andand gains between groups gains between groups

• impoverishes impoverishes some some people people

• excludes people and limitexcludes people and limitss awareness awareness

• overlooks sustainability aspectsoverlooks sustainability aspects

• induces conflict induces conflict andand higher costs higher costs


Towards shared values, objectives & goals…Towards shared values, objectives & goals…

• equityequity

• efficiencyefficiency

• participatory decision-makingparticipatory decision-making

• sustainabilitysustainability

• AccountabilityAccountability

Define whose rights & what risks…Define whose rights & what risks…

RRisksisks

• Move beyond considering voluntary risk takers Move beyond considering voluntary risk takers to include involuntary risk bearers to include involuntary risk bearers

RightsRights

• No party’s rights should extinguish another’sNo party’s rights should extinguish another’s

• Where rights compete – negotiated agreements Where rights compete – negotiated agreements are needed are needed


Turning Conflict Into ConsensusTurning Conflict Into Consensus

• Gain public acceptance Gain public acceptance

• Assess options Assess options

• Address existing damsAddress existing dams

• Sustain rivers and livelihoods Sustain rivers and livelihoods

• Recognize entitlements and share benefits Recognize entitlements and share benefits

• Ensure complianceEnsure compliance

• Share rivers across boundariesShare rivers across boundaries

Seven Strategic prioritiesSeven Strategic priorities

Gaining public acceptanceGaining public acceptance……

• dams affect existing rights dams affect existing rights && create create wide range of riskswide range of risks

• opportunities exist for achieving a highopportunities exist for achieving a higher er level level of of equityequity

• recognise rights of indigenous recognise rights of indigenous && tribal peoples tribal peoples

• achieve outcomes through binding formal agreementsachieve outcomes through binding formal agreements


• failure to adequately define needs failure to adequately define needs & & assess options led to assess options led to disputedispute

• an early and open examination of optionsan early and open examination of options can avoid poor can avoid poor projectsprojects

• raise the significance of social raise the significance of social & & environmental aspects environmental aspects

• increase the effectiveness of existingincrease the effectiveness of existing systems as a priority systems as a priority

Comprehensive options Comprehensive options assessmentassessment……


Address existing damsAddress existing dams……

• most dams that will operate in the most dams that will operate in the 2121stst century already exist century already exist

• considerable scope exists for considerable scope exists for improving benefits improving benefits

• remedy outstanding social issuesremedy outstanding social issues

……enhance mitigation, restoration enhance mitigation, restoration && enhancement of ecosystems enhancement of ecosystems

• use licenuse licensses to formalize es to formalize operating agreements operating agreements

Sustain rivers and livelihoodsSustain rivers and livelihoods……

• rivers support rivers support millions of millions of livelihoods livelihoods

• dams cause significant and often irreversible effects on dams cause significant and often irreversible effects on ecosystems ecosystems

• value value rivers, rivers, ecosystems ecosystems & endangered species& endangered species

• emphasise avoidance emphasise avoidance of impacts of impacts

• maintain ecosystemmaintain ecosystem integrity through integrity through environmental flows environmental flows

Recognize entitlements Recognize entitlements && share benefits share benefits ……

• many many peoplepeople displaced - many more displaced - many more ununrecognised recognised

• including including those those whowho depend on a river’s resources depend on a river’s resources

• recognise rights and assess risks recognise rights and assess risks as a basis for as a basis for negotiationsnegotiations

• agree legally enforceable entitlementsagree legally enforceable entitlements

• adversely adversely affected people affected people becomebecome first among beneficiaries first among beneficiaries

Ensure compliance Ensure 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 to people and the environment to people and the environment

• introduce initiatives to reduce corruptionintroduce initiatives to reduce corruption

• develop incentive framework for compliancedevelop incentive framework for compliance

Share rivers across boundariesShare rivers across boundaries……

• conflicts over transboundary rivers dueconflicts over transboundary rivers due to to 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

• encourage encourage consistent policies for financing agenciesconsistent policies for financing agencies


Dams in the pipeline - it’s not too late Dams 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



BY :- SAGAR MANDALBY :- SAGAR MANDAL

X-AX-A

sagar725744

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