Hydroelectric power

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Hydroelectric powerits impacts
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Outline

• The global hydroelectric appetite.
• Dams in the 20th century.
• Benefits of dams.
• Environmental impacts of big dams.

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1. The global hydroelectric appetite

• Worldwide represents _____ of the total energy
  generated (1999).
• _____ of worlds total commercial energy
• Supplies 99 of electricity energy requirements
  in

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World hydroelectric generating capacity -
1950-1991
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Hydroelectric power

• There are various renewable ways of generating
  electric power using water
• tidal power - bays estuaries.
• open ocean waves.
• water temperature gradients.
• saline solar ponds.
• freshwater solar ponds.
• run-of-the-river turbines.
• The main method is through the use of large dams.

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Hydropower - Canada

• 1995 - the UN ranked Canada as the worlds
  largest hydroelectric producer (_____ of global
  output).
• Generated 340.3 billion kilowatt-hours (1999).
• This constituted _____ of our electric power.
• _____ of total commercial energy.
• Canada ranks in the worlds top 10 dam builders
  _____ large dams (those higher than 10m).

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Major hydroelectric dams and transmission lines
in Canada
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Hydropower - USA

• The United States is second only to Canada in the
  amount of hydroelectric power produced.
• Generated 305.6 billion kilowatt-hours in 1999.
• This was only 8 of the electric power used in
  the USA.

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Potential and installed hydroelectric generating
capacity

• Constraints on development
• political.
• economic.
• environmental

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2. Dams in the 20th century

• Construction of dams to manage water resources
  dates back approx. 5000 years.
•  
• Modern era of big dams (gt15m in height) started
  in 1930s.
•  
• Latter part of 20th century - global escalation
  in the rate and scale of construction of big
  dams. This was due to advances in
• concrete technology.
• earth-moving machinery.

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Purpose of dams

• Initially big dams were solely for generating
  electricity but subsequent (and current) uses
  include

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Dams on a global scale

• Global stats
• most active phase of dam construction was
  1950-1980s an average of 885 dams completed per
  year.
• 1961 7408 large dams registered worldwide.
• by 1986 _____ large dams.

Source International Commission on Large Dams
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Construction of dams by decade (1900-2000)
Note excludes dams in China.
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Dams constructed by region(1900-2000)
Note Information excludes the time-trend of dams
in China.
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Dams on a global scale

• Of the large dams in place by 1986
• _____ were in Asia.
• _____ of world total were located in China.
• _____ of dams are lt30m in height.
• _____ exceed 60m in height.
• by early 1990s reservoirs controlled ____ of
  all land surface runoff.

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Regional distribution of large dams at the end of
the 20th century
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Dams currently under construction
- depending on source of information
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3. Benefits of dams

• The benefits of big dams include
• hydroelectricity is a renewable energy source
  cheap after the initial high costs of
  construction.
• saves on money (and environmental effects)
  required for purchase of fossil fuels.
• allows management of river flow regimes erasing
  high flood and low flow periods replacing them
  with a more constant annual flow.

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Benefits of dams

• More benefits
• stability of river levels benefits navigation
  recreation and tourism.
• reservoir provides irrigation water for
  croplands.
• often seen as symbols of economic advantage and
  national prestige for developing countries.
• Lifespan is 2 10x greater than coal or nuclear
  plants.
• Emit no air pollution or GHGs.

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4. Environmental impacts ofbig dams

• Despite the success of big dams in achieving
  their economic aims the construction of dams and
  their related reservoirs create significant
  environmental problems through

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Areas affected by hydro projects

• catchment area contributing to the reservoir.
• river area below the dam to the estuary coastal
  zone and offshore.
• ancillary aspects such as power transmission
  corridors pipelines canals tunnels relocation
  and access roads borrow pits material disposal
  areas construction camps.

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Areas affected by hydro projects

• Contd
• unplanned developments stimulated by the dam
  project i.e. logging shifting agriculture
  hunting.
• off-site areas required for re-settlement.
• regional airshed surrounding the reservoir.
• migratory routes of humans wildlife fish.

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Columbia River

• Example of intensively managed river.
• Is the worlds largest generator of
  hydroelectricity with 19 major dams and 60
  smaller dams.

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Temporal aspects

• While the creation of the reservoir represents
  an immediate environmental change many changes
  will require a long time period for the
  environment to adjust if it can adjust.

• Itaipu Dam Brazil
• 196m high.
• 7.8 km long.
• Reservoir
• 170 km long.
• 1350 km2.

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Range of impacts

• The range of environmental and human impacts
  related to dam construction can be considered at
  three levels
• dam reservoir.
• upstream area.
• downstream area.

Almendra Dam Spain
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The dam reservoir

• Creation of a
• reservoir results in
• a loss of resources
• in the inundated
• land area.

Kenya
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Aswan High Dam - Egypt
Close-up of dam site
Lake Nasser
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Trees vegetation

• Trees can be removed prior to inundation (for
  timber fuelwood). If the trees are not removed
• aerobic decomposition of woody material produces
  hydrogen sulphide which is toxic to fish.
• organic matter decomposition produces mercury
  (through methylation) which bioaccumulates in
  fish and renders them unsafe for consumption.
• dangers to boating and recreation (submerged
  trees floating to the surface)

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Water quality

• There are significant variations in water quality
  in the first decade of a reservoirs life
• initial impoundment biological productivity is
  high due to initial flush of organic nutrients
  from flooded vegetation and soils.
• fish populations are high in the first few years.
• organic nutrient levels decline after a few
  years followed by declines in aquatic organisms.

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Historical sites

• Reservoirs inundate areas with archeological
  sites.
• Tucurui Dam in Brazil flooded 24 sites dating
  from 70-1000 AD

• Temple of Isis moved to Philae Island when Lake
  Nasser was formed (Egypt).

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Population displacement

• Land areas to be inundated are not always devoid
  of people.
• Sanmen Gorge project on the Huang Ho River
  required the resettlement of 300000 people.
• Three Gorges Dam on the Yangtze River will
  require moving over 1.9 million people from 19
  main cities by 2008.

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Population displacement

• Human displacement results in

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Longterm effects of reservoirs

• There are various longterm effects of reservoirs
  due to
• their size many reservoirs are very large more
  so than natural regional waterbodies
• their composition large bodies of water in
  anthropogenic settings.

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Longterm effects - diseases

• Increases in diseases due to alterations in the
  natural hydrological cycle.
• Schistosomiasis debilitating disease spread by
  parasitic larvae in some aquatic snail species.

• Malaria usually increases since mosquitoes
  breed in standing water.

Anopheles mosquito
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Longterm effects - invasive species

• Spread of aquatic weed species generally through
  eutrophication.

• Lake Brokopondo reservoir (Suriname) water
  hyacinth covered 50 of the water surface within
  two years of the reservoirs completion.

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Lake Brokopondo

• Effects of the Water Hyacinth
• decline in aquatic diversity and populations due
  to the toxicity of the weed.
• absorbed much of the lakes available nutrients.

• blocked the suns rays from penetrating to the
  depths of the lake.
• turbines clogged by the weeds necessitating
  periodic shut-downs.

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Longterm effects - local climate

• Reservoirs alter the local climates in a variety
  of ways
• huge quantities of water are lost through
  evaporation. This increases humidity and the
  incidence of fog.
• local winds increase (fetch over the water
  surface).
• temperature regime changes as the water body
  retains heat. Eg. the frost-free period in the
  region surrounding the Rybinsk reservoir (near
  Moscow) has been extended by 5-15 days.

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Longterm effects - global climate

• Hydroelectric projects lessen the reliance on
  fossil fuels and help decrease the emissions from
  the burning of coal/oil.
• However
• decaying vegetation in reservoirs emit large
  quantities of CO2 and methane.
• Some research has suggested that GHGs emitted
  via new hydro projects in Brazil will exceed the
  emissions that would be released by generating
  electricity through fossil-fuel burning.

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Longterm effects waterlogged soils

• Standing water seepage into surface soils impedes
  normal water drainage especially in time of
  rainy seasons (increased surface erosion).
• Kuban Reservoir (southern Russia) reservoir
  filled to over-capacity to aid navigation and
  rice cultivation resulted in water damage to 130
  communities 27000 homes 150 km of roads the
  Krasnodar airport and ruined 100000 ha of crops.

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Longterm effects waterlogged soils

• Raised water tables lead to slope instability
  along the shore of the reservoir.
• Vaiont Dam (Italy)
• completed in 1961 was 262m high (6th highest in
  the world at the time).
• 1963 large land(exacerbated by dam
  project) into the reservoir displaced water which
  flowed over the dam.

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Vaiont Dam

• Resulting downstream wave was 260m high.

• Several villages were swept away 2600 people
  died.

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Longterm effects siltation

• Build-up of sediments in reservoir
• decreases the water storage capacity.
• shortens the life expectancy of the
  hydro-electric equipment.
• requires big to rectify.

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Sedimentation rates of Chinese reservoirs
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Upstream effects

• Hydro project infrastructure leads to better
  access to good quality timber.
• Deforestation increases surface erosion which
  results in higher siltation rates into the
  reservoirs.
• Ambukloo Project (Philippines) deforestation
  above the reservoir has resulted in high
  sedimentation rates such that the useful life of
  the reservoir has decreased from 60 to 32 years.

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Downstream effects

• The hydrological regime of the river is modified
• discharge
• velocity
• thermal characteristics

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Downstream effects - siltation

• Siltation loads decrease due to trapping of
  sediment in the reservoir. This results in
• altered ecosystems.
• coastal erosion (coastal currents remove material
  along deltas).
• decline in some fish species due to lack of
  nutrient flush.

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Downstream effects flow regime

• Decreased river flows allows saltwater intrusion
  into delta ecosystems.
• Farakka Barrage (Ganges River) built in 1975
  decreased dry-season discharge allowing area in
  Bangladesh affected by salinity problems to
  increase from 350K ha to 890K ha.

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Downstream effects wildlife

• Dams are barriers to fish migration unable to
  move from lakes/oceans upstream to spawning
  grounds.

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Three Gorges Dam (China)
cherished dream of Chinese leaders for several
decades.
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The Three Gorges Dam project

• Purpose
• to produce energy for burgeoning Chinese
  population.
• end disastrous floods along the Yangtze .
• 1998 Yangtze flood 4000 dead 14 million left
  homeless and 24 billion in economic losses.

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The Three Gorges Dam project

• Advantages
• improved navigability on the river.
• larger ships could sail as far as 2000 km
  upstream from the the sea in the service of
  Chinas burgeoning domestic and export trade.

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The Three Gorges Dam project

• The project will
• create a reservoir _____ km long and 1.3 km wide
  (on average).
• submerge _____cities _____ towns and over _____
  villages.
• require the resettlement of 1.9 million people.
• submerge _____ factories and mines.
• cost approx 24 billion (US) by 2009 (completion
  date).

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The Three Gorges Dam project

• It will inundate gt1000 important archaeological
  sites.

About 74000 ha of good agricultural land will be
flooded.
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