Hydroelectric power & its impacts

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

1. The global hydroelectric appetite Worldwide: represents _____% of the total energy generated (1999). _____% of world’s total commercial energy Supplies 99% of electricity energy requirements in:

World hydroelectric generating capacity - 1950-1991 Source: Worldwatch Institute, 1996.

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.

Hydropower - Canada 1995 - the UN ranked Canada as the world's 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 world's top 10 dam builders: _____ large dams (those higher than 10m).

Major hydroelectric dams and transmission lines in Canada

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.

Potential and installed hydroelectric generating capacity Constraints on development: political. economic. environmental Source: Worldwatch Institute, 1996.

2. Dams in the 20th century Construction of dams to manage water resources dates back approx. 5000 years.   Modern era of big dams (>15m 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.

Purpose of dams Initially, big dams were solely for generating electricity but subsequent (and current) uses include:

Dams on a global scale Global stats*: most active phase of dam construction was 1950-1980’s; an average of 885 dams completed per year. 1961: 7408 large dams registered worldwide. by 1986: _____ large dams. * Source: International Commission on Large Dams

Construction of dams by decade (1900-2000) Source: Dams and Development. A New Framework for Decision-making. The report of the World Commission on Dams. Released Nov. 16, 2000. Note: excludes dams in China.

Dams constructed by region (1900-2000) Source: Dams and Development. A New Framework for Decision-making. The report of the World Commission on Dams. Released Nov. 16, 2000. Note: Information excludes the time-trend of dams in China.

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 <30m in height. _____% exceed 60m in height. by early 1990’s reservoirs controlled ____% of all land surface runoff.

Regional distribution of large dams at the end of the 20th century Source: Dams and Development. A New Framework for Decision-making. The report of the World Commission on Dams. Released Nov. 16, 2000.

Dams currently under construction Country No. dams Purpose India 695 – 960 * Irrigation, multipurpose China 280 Flood control, irrigation, hydropower Turkey 209 Irrigation, hydropower, water supply South Korea 132 Irrigation, hydropower, flood management, water supply Japan 90 Mainly flood control Iran 48 (above 60m) Source: Dams and Development. A New Framework for Decision-making. The report of the World Commission on Dams. Released Nov. 16, 2000. * - depending on source of information

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.

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 GHG’s.

4. Environmental impacts of big 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:

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.

Areas affected by hydro projects Cont’d: 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.

Columbia River Example of intensively managed river. Is the world’s largest generator of hydroelectricity with 19 major dams and 60 smaller dams.

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.

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

The dam & reservoir Creation of a reservoir results in a loss of resources in the inundated land area. Kenya

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

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)???

Water quality There are significant variations in water quality in the first decade of a reservoir’s 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.

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).

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 300,000 people. Three Gorges Dam on the Yangtze River will require moving over 1.9 million people from 19 main cities by 2008.

Population displacement Human displacement results in:

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.

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

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 reservoir’s completion.

Lake Brokopondo Effects of the Water Hyacinth: decline in aquatic diversity and populations due to the toxicity of the weed. absorbed much of the lake’s available nutrients. blocked the sun’s rays from penetrating to the depths of the lake. turbines clogged by the weeds, necessitating periodic shut-downs.

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.

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 GHG’s emitted via new hydro projects in Brazil will exceed the emissions that would be released by generating electricity through fossil-fuel burning.

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, 27,000 homes, 150 km of roads, the Krasnodar airport and ruined 100,000 ha of crops.

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 landslide (exacerbated by dam project) into the reservoir displaced water which flowed over the dam.

Vaiont Dam Resulting downstream wave was 260m high. Several villages were swept away; 2600 people died.

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.

Sedimentation rates of Chinese reservoirs River Period of record (years) Storage lost (%) Sanmenxia Huang Ho 7.5 35 Qingtongxia 5 84 Yanguoxia 4 68 Liujiaxia 8 11 Xingqiao Hongliuhe 14 71

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.

Downstream effects The hydrological regime of the river is modified: discharge – velocity – thermal characteristics –

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”.

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.

Downstream effects – wildlife Dams are barriers to fish migration – unable to move from lakes/oceans upstream to spawning grounds.

Three Gorges Dam (China) “cherished dream of Chinese leaders for several decades”.

The Three Gorges Dam project Purpose: to produce energy for burgeoning Chinese population. end disastrous floods along the Yangtze . 1998 Yangtze flood: 4,000 dead, 14 million left homeless and $24 billion in economic losses.

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 China's burgeoning domestic and export trade.

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).

The Three Gorges Dam project It will inundate >1000 important archaeological sites. About 74,000 ha of good agricultural land will be flooded.

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