Dams in Developing Nations

• Introduction
  
  • Definition: structure built across a stream, river, or estuary to retain water (or debris)
    
  • History
    
    • Dams have been around for ~5,000 years
      
      • Domestic and agricultural usage
        
      • Advances in technology coincides with population increas
        
    • 19th & 20th Centuries
      
      • Increased electricity demand = larger dams
        
      • Increased population = need for flood protection
        
      • Dams now serve various purposes
        
  • Current uses of Dams
    
    • Hydroelectric power
      
    • Flood control
      
    • Water Storage
      
    • Tailings / Mining Dams
  • Types of Dams
    
  • Arch Dams
    
    • Curved - dependent upon arch action for its strength.
      
    • Thinner and therefore require less material
      
    • Good for sites that are narrow and have strong abutments.
      
  • Buttress Dams
    
    • Face (front) is held up by a series of supports.
      
    • Have many forms - the face may be flat or curved.
      
  • Gravity Dams
    
    • Resist the horizontal thrust of the water entirely by their own weight.
      
    • Typically used to block streams through narrow gorges.
      
    • Use a large amounts of concrete. This can be expensive.
      
    • Many prefer its solid strength to arch or buttress dams.
      
  • Embankment Dams
    
    • Massive dams made of earth or rock.
      
    • Rely on their weight to resist the flow of water
      
  • Tailings Dams
    
    • Tailings are waste material from the mining industry
      
      • Must separate ore from rock
        
      • “Floatation” method often used
        
      • Waste is stored in tailings dams
        
    • Three types of embankments
      
      • downstream,
        
      • upstream
        
      • and centerline structures
        
    • Type used is dependant upon many factors, including
      
      • Volume
        
      • Seismicity,
        
      • Etc.
        
    • Upstream Design Tailings Dam
      
      • Common
        
      • Inexpensive
        
      • Prone to failures
        
    • Centerline Design Tailings Dam
      
      • Mix of up and downstream design
        
      • Cannot be used for water retention
        
    • Downstream Design Tailings Dam
      
      • Can hold more water
        
      • More stable design
        
      • Costs increase exponentially with height
        
  • Other parts of a dam may include
    
    • spillways, gates, or valves
      
    • an intake structure conducting water to a power station or to pipelines
      
    • provision for evacuating silt carried into the reservoir
      
    • means for permitting ships or fish to pass the dam.
      
  • Forces that Act on a Dam
    
    • Main forces
      
      • force of the reservoir water (W)
        
      • weight of concrete (C)
        
      • both forces together
        
      • The main force on an embankment dam is water (W).
        
      • The weight of the dam is also a force,
        
    • Other forces
      
      • internal water pressure
        
      • temperature variations in the concrete
        
      • earthquake loads
        
      • settlement of the foundation or abutments
        
        
• Case Studies: Brazil - Tucuruí Dam
  
  • Climate:
    
    • mostly tropical, but temperate in south
      
  • Terrain:
    
    • mostly flat to rolling lowlands in north; some plains, hills, mountains, and narrow coastal belt
      
  • Background
    
    • 93% of Brazils’ energy comes from hydroelectric
      
    • More than one million people have been displaced by the construction of Brazil’s dams
      
    • 34,000 km2 have been inundated by reservoirs
      
    • Little effort has been made for alternative energy
      
  • The Tucuruí Dam
    
    • Part of a World Commission on Dams study on the subject of the development effectiveness of large dams.
      
    • Phase I – 1975 to 1984
      
    • Phase II – began in 1988; first turbine scheduled to be operational by December 2002
      
    • Structural Type: Gravity dam
      
    • Reservoir: 2,875 km2
      
    • Length: 1,321 m
      
    • Height: 77 m
      
    • Function / usage: Hydroelectric dam
      
    • Power: 8,000 mW
      
  • Environment - current issues:
    
    • deforestation in Amazon Basin destroys the habitat and endangers a multitude of plant and animal species indigenous to the area
      
    • lucrative illegal wildlife trade
      
    • land degradation and water pollution caused by improper mining activities
      
    • wetland degradation
      
    • The Tocantins River
      
      • located completely within the province of Eastern Amazonia
        
      • Flows into the Amazon river estuary
        
      • Annual volume of 334km3
        
      • Catchment area of 758,000 km2 (7.5% of the land mass of Brazil)
        
      • Contributes to a well-defined and stable climatic regime across this region
        
  • Socio-Economic Impact
    
    • Severity of the impacts was far greater than initially foreseen
      
    • Population doubled in 10 years
      
    • Mandatory relocation programs and economic migrations
      
    • Massive layoffs after Phase I completion
      
    • Compensation packages did not take into account cultural and historical values
      
    • Parakanã
      
      • Group split up and relocated numerous times
        
      • August 1986, threatened to block the Transamazon Highway and employ terror tactics
        
      • Parakanã Programme / Parakanã Indigenous Reserve.
        
      • Assimilate the group into mainstream culture
        
      • Establishment of villages and maintaining their traditional hunting and gathering activities
        
    • Asurini
      
      • Territory below the dam
        
      • Affected by migrant workers and displaced people
        
      • 1970’s – road built through 9 km of Asurini land
        
      • 1997 – new power line contemplated
        
      • Asurini resorted to the destruction of public infrastructure
        
      • Road built, no power line, and no Asurini compensation
        
    • Increase in:
      
      • Malaria, schistosomiasis, etc,
        
      • Industrial accidents,
        
      • Alcoholism
        
      • Sexually transmitted diseases and AIDS
        
      • Infant mortality in the 1980’s rates 6x that of Pará State and 5x that of all of Brazil
        
  • Effects on Ecosystems
    
    • Initially, concern was towards the effect of the ecosystems on the construction project
      
    • Water Quality
      
      • Low dissolved oxygen levels downstream
        
      • Reduced flooding downstream = fertilization processes
        
      • Increase in mosquitoes = increase in malaria
        
    • Fisheries
      
      • Initially anticipated a high mortality rate during & after dam construction
        
      • Actual rates much higher due to low D.O. & nutrient levels
        
    • Terrestrial Impacts
      
      • Submersion of 2,850 km2 of land including large areas of rainforest
        
      • Wildlife reserves with permanent a wildlife study group established (Operação Curupira)
        
        • Bans on hunting and poaching
          
        • Capture and release of some 280,000 animals.
          
        • Total cost = US $30 million
          
          
• Case Studies: Three Gorges Dam - China
  
  • Background
    
    • Location: Sandouping, Yichang, Hubei province
      
    • Structural Type: Gravity
      
      • Height: 181 m
        
      • Length: 2,150 meters
        
      • Reservoir Capacity: 1.39 trillion cubic feet
        
    • Function / usage: Hydroelectric dam
      
      • 18.2 million kilowatts
        
  • Comparison between the Three Gorges Dam and the world’s largest dams (reservoir capacity, in cubic feet)
  • Yangtze River, China
    
    • Background
      
      • Construction phase: 1994 – 2009
        
      • Functions: Flood control, power generation, improved navigation
        
    • Yangtze River, China
      
      • Background
        
        • About 20,000 people are working nearly round the clock to complete the structure by 2009.
          
        • The lake that will form behind Three Gorges Dam will stretch for about 350 miles -- the distance from San Francisco to Los Angeles.
          
        • Three Gorges Dam reservoir will actually be visible from the moon! Source: http://www.pbs.org/wgbh/buildingbig
          
      • Socio-Economic Impact
        
        • 600,000+ people have had to be resettled
          
        • 13 cities, 140 towns, more than 1,600 villages, and 300 factories will be submerged
          
        • Est. 1.3 – 1.9 million will eventually have to leave
          
        • Supposedly there are no contractual agreements with the resettlement authorities
          
        • Loss of culture, way of life, etc.
          
      • Archeological Impact
        
        • 1,300 known cultural heritage sites affected
          
        • Budget for excavations severely reduced
          
        • Looting common
          
      • Problems
        
        • Over budget
          
        • Coercion and violence have been used against communities affected by dams
          
        • Critics arrested or forced into exile
          
        • No Dam Inundation plan
          
        • Increased silt build-up
          
        • Decreased nutrient levels downstream
          
          
• Case Studies: San Marcelino Dam - Philippines
  
  • Climate: tropical marine
    
    • northeast monsoon (November to April);
      
    • southwest monsoon (May to October)
      
  • Terrain:
    
    • mostly mountains with narrow to extensive coastal lowlands
      
  • Natural hazards:
    
    • usually affected by 15 and struck by five to six cyclonic storms per year;
      
    • landslides;
      
    • active volcanoes;
      
    • destructive earthquakes;
      
    • tsunamis
      
  • Natural resources:
    
    • timber, petroleum, nickel, cobalt, silver, gold, salt, copper
      
  • The San Marcelino tailings dam spill
    
    • Dizon Copper-Silver Mines, Incorporated (DCSMI)
      
    • Operations ceased in 1997
      
    • Two mine tailings dams
      
      • Bayarong
        
        • Size: 122-hectare
          
        • 47 million cubic meters of mine tailings
          
        • Supposed to be able to withstand a 9.5 EQ
          
      • Camalca – silt & debris
        
    • Catch Basin
      
    • Mapanuepe Lake
      
    • San Marcelino Dam - Philippines
      
    • History
      
      • 1991
        
        • Mt. Pinatubo erupted, creates Lake Mapanuepe (spillway weakened)
          
      • 1998
        
        • spillway damaged by the effects of a typhoon
          
      • 1999
        
        • Mines and Geosciences Bureau noticed “some seepages at and partial erosion of the tailings dam’s spillway”
          
        • Recommended the following:
          
          • installation of siphons and electrical pumps
            
          • strengthening/preserving the remaining concrete portion of the spillway approach
            
          • opening of the previously constructed drain tunnel
            
        • Recommendations heeded
          
          • 10 days of rain from Typhoons Chedeng and Dodong proved recommendations not enough.
            
          • New, more aggressive measures proposed
            
      • 2002
        
        • August 27 – inspection reveals damage to dams & spillways, leakage into Lake Mapanuepe
          
        • September 5 – the Department of Environment and Natural Resources called the sudden burst of the dams "unlikely"
          
        • September 11 – spillway collapses, flooding low-lying villages with mine wastes and other chemicals
          
        • September 12 – 1000 people evacuated
          
      • 2003
        
        • DENR Order:
          
          • short term emergency measures to prevent the overtopping of the dam,
            
          • do the necessary repairs in order to rehabilitate the partially collapsed spillway,
            and pay the appropriate mine wastes and tailings fee and penalty for the unauthorized discharge of mine wastes/tailings.
            

LINKS

• Cracking Dams (http://simscience.org/cracks/)
• Tailings.info (http://www.tailings.info)
• PBS's Building Big: Dam Basics (http://www.pbs.org/wgbh/buildingbig/dam/index.html)
• The World Commission on Dams (http://www.dams.org/)
• Stucturae: Tucuruí Dam, Phase 1 (http://www.structurae.net/en/structures/data/s0003612/index.cfm)
• Republic of the Philippines - Mines and Geosciences Bureau / Department of Environment and Natural Resource: UPDATE ON THE CONCERNS AT THE BAYARONG TAILINGS POND (http://www.mgb.gov.ph/mining%20issues_dizon_070903.htm)
  

Introduction | Brazil - Tucuruí Dam | China -Three Gorges Dam | Philippines - San Marcelino Dam | Links | top