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Hydroelectric Energy


Context within Nora

Relationships to Needs

Electricity from hydroelectric dams can be used in a vast variety of ways, including the pumping of water to where it is needed, processing, transportation and refrigeration of food, lighting, heating and other services that contribute to security and comfort in houses, the production of clothing, the provision of services for health and for opportunities to learn (for example, computers require electricity to run), and the provision of transportation for mobility (electric vehicles and trains).

Factors pushing increasing demand for hydroelectric power include the growing human population, billions of people aspiring to the comforts now available in the wealthy countries, and people everywhere looking for alternatives to fossil fuels and nuclear power. However, increased energy efficiency may also counteract these growth factors.

Relationships to Organizational Forms

The construction of large hydroelectric dams requires capital investment on a large scale, which typically involves governments, large banks, and large construction companies as well as subcontractors; these are linked to each other through committed sales or services usually involving contracts over many years. The utilities which ultimately own and operate the dams are likewise linked to their customers through committed sales or service contracts. Currencies and markets are required for all of these transactions.

Large scale hydroelectric projects often entail coercion and denial of choice in forcing people to relocate away from the flooded areas; two very prominent examples of this in recent years are in the Narmada Dam project in India and the Three Gorges Dam in China (in the latter, over a million people have been forced to relocate).

Micro-hydro projects can be built and operated at a community level in projects of community solidarity or even self provisioning.

Self-provisioning in the household can conserve energy for the use of the community as a whole. There are large percentages of energy that is wasted every year due to a lack of this type of self-provisioning. Households can take advantage of other sources of renewable resources, such as solar power, to lessen the dependence on non-renewable forms of energy.

Relationships to Resources

Hydroelectric power can be available in most locations of the world with the abundance of water around the world and considering that most settlements are near water sources. Having hydroelectric energy abundant in these areas will make people less dependent on other sources of energy.

Hydroelectric power is also a clean source of energy that does not contribute pollution and the depletion of fossil fuels making it an advantageous source of energy for the future. Carbon dioxide emissions will also be lessened as the transition to this form of energy production continues. 

The construction of dams with reservoirs does, however, flood substantial areas of land along with the living things that grow on it, replacing human settlements and riparian habitats with a large lake with slow-moving water.

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Understanding Current Patterns of Abundance and Scarcity


A hydroelectric dam generates energy through relatively simple mechanics. The usual process begins by damming a river to impound a lake (a reservoir) behind the dam. Inside the dam, gates control the inflow of the water into the "penstock," a pipeline in which the water pressure is built up. After the pressurized water flows through the penstock, it turns the large blades of the turbine. The water then passes through pipes and outflows into the river downstream. The turbine is connected to the generator above it by a shaft and this is how the energy is collected from the pressurized water (Bonsor 2001).

The power is created by the generator. The turbine has large magnets connected to its blades and these magnets pass underneath copper coils which creates an alternating current (AC). The powerhouse inside the dam complex contains the transformer that converts the AC to a higher voltage current. High-voltage power lines take the energy out of the complex to the public (Bonsor 2001).

Hydropower can also be provided by "run of river" schemes where there is little or no storage of water – the naturally running water is used to turn a turbine. A further use of hydropower uses pumped storage – if excess power is available from other sources and cannot be used immediately, that power can be used to pump water uphill into a reservoir and then generate hydropower when it is needed (IRENA 2012). This is a relatively cheap method of energy storage, and could potentially be used in combination with solar or wind power (to use that power generated when the sun or wind is very strong but electricity demand is low).

Hydroelectric schemes can vary tremendously in size, from small installations on creeks or small rivers all the way to the size of the Three Gorges Dam in China with its 22,500 MW generating capacity. IRENA (2012) classifies hydropower schemes in the following size categories:

  • pico-hydro: from a few hundred watts up to 5 kW (for remote areas or off-grid)
  • micro-hydro: 5-100 kW (small communities or industries, off-grid)
  • mini-hydro: 100 kW-1MW (may or may not be connected to the electric grid)
  • small hydro: 1-20 MW (usually grid-connected)
  • medium hydro: 20-100 MW (almost always grid-connected)
  • large hydro: over 100 MW (feeding into large grid)

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Short History

Water has been used as a source of energy for thousands of years. In pre-industrial times, rivers were used to turn mills that would grind gain or power small machinery. The 1800s showed the first steps into hydroelectric power when generators were added to mills, for example in Grand Rapids, Michigan USA to power theater and storefront lights. Early hydroelectric schemes were very small in size, but by the 1930s, very large dams were constructed (e.g., the Hoover Dam in the US). By the 1940s, 40% of the US electricity generation was provided by hydroelectric power (Office of Energy Efficiency and Renewable Energy 2014). 

After World War II, large hydropower dams were constructed in many countries, and were seen as a key part of modern economic development. Jawaharlal Nehru, the first prime minister of India, famously referred to them as the "temples of modern India." The World Bank provided loans for dam construction in many countries, regarding them as key investment to provide cheap electric power for industry. The Bank also favored large schemes that minimized administrative overhead (a few large loans require less time to administer than many small ones), and large dam projects fit this bill perfectly.

Today, hydroelectricity provides roughly 16% of world electric power. The percentage varies tremendously between countries; for example, Norway with its very large hydropower potential and rather small population provides 99% of its electricity from hydropower; in total more than 25 countries supply at least 90% of their power from hydro. Among the 65 countries where hydropower is the most important energy source, one can also list Brazil (84%), Venezuela (74%), Canada (59%) and Sweden (49%) (IRENA 2012). Most other countries provide less than 20% of their power from hydro; the figure for the United States is 10%.[4] 

Despite their successes in generating large amounts of reliable and cheap power, hydroelectric dams (especially large ones) have come under increasing criticism because, among other impacts,

  • they inundate large amounts of land which may include unique biological habitats, productive agricultural land, and numerous villages and towns,
  • the reservoirs trap fertile sediments that are unavailable downstream, alter patterns of erosion and sediment deposition, and limit the useful life of the dam,
  • in arid regions, the huge surface area of a reservoir enhances rates of evaporation, reducing the total amount of water available downstream,
  • the huge weight of the water in a reservoir may lead to earthquakes,
  • the dams are insuperable to many fish species, preventing their migrations and interfering with their reproduction, and
  • the human rights of the people in the inundated area have often been grossly violated, not respecting their rights to the land or livelihoods, with inadequate compensation for their losses.

The controversies around dams led to the formation of the World Commission on Dams in 1998; it issued a report in 2000 reviewing the costs and benefits of dams. It made a number of policies recommendation, among which the recommendation to involve all stakeholder groups in decision-making is perhaps the most important. One of the members of the commission, Medha Patkar, one of the leaders against the Narmada Dam project, noted in a comment that this is not enough, however:

"A full assessment of the options for meeting water and energy needs as the first part of project planning needs to be supported. But only creating a level playing field for options cannot suffice. We should instead give priority to more equitable, sustainable and effective options to satisfy basic human needs and livelihoods for all before supporting the additional luxuries of the few, unjustified in the face of the many who remain deprived." (Comment by Medha Patkar, Final Report of the World Commission on Dams, p. 322)

In the wake of these controversies, many environmental groups favor the construction of many small or micro-hydro facilities rather than a few mega-projects. They also favor a comprehensive review of all available options, including measures to increase energy efficiency and reduce total electricity demand, an approach known as Integrated Resource Planning (International Rivers 2013, see Links section). However, large dams continue to be constructed, most notably the Three Gorges Dam in China (completed in 2012), which led to the displacement of some 1.2 million people (the most ever displaced due to a single development project).

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New, less environmentally disruptive technologies to generate electricity from moving water may be the focal point of hydroelectricity's future. New processes such as using waves, marine currents, and designing less intrusive turbines are changing the scope of hydroelectric power. Other technologies have been introduced to improve the process as well. A setback to using dams was that they interrupt fish migrations and interfere with their reproduction (for example, of salmon which migrate up rivers to lay their eggs). Many dams have begun to use fish ladders that allow them to cross the dam and lessen the controversy (Office of Energy Efficiency and Renewable Energy 2014). Dams can also be "repowered," meaning that more efficient turbines are installed in existing dams so that their power output is increased without any further impacts on the environment.

With climate change emerging as an important issue in the last 10-15 years, scientists have begun examining its effects on hydroelectric dams. Increased global temperatures have resulted in higher evaporation rates and have contributed more ice cap melt runoff. Both of these factors have resulted in less discharge from hydroelectric dams (Blackshear et al. 2011). Since hydroelectricity is a major energy source for many parts of the world, less discharge from hydroelectric plants may result in blackouts in some areas. Conversely, hydroelectric dams can contribute to climate change in their establishment phase, because terrestrial vegetation flooded in the reservoir rots and thereby emits methane, a powerful greenhouse gas. However, hydropower remains the most important source of renewable electric power; it does not consume the water that runs down the river, and the operation of the dam itself does not generate greenhouse gases: these are all aspects of hydropower that continue to stand in its favor.


Some Controversial Cases

Large hydroelectric dams are the primary source of hydropower and are typically constructed along powerful water sources. These waterways are a source of water for many towns and villages, and can affect millions of people. When these rivers are dammed, they can have numerous adverse affects as outlined above. The following are several controversial cases.

Belo Monte, Amazon River, Brazil

In Brazil, there have been plans for years to construct the Belo Monte dam along the Amazon river. If constructed, this dam would have been among the largest in the world. This dam threatened the lands of indigenous peoples who lived in the Amazon, along with threatening large regions of the ecosystem. The construction of the dam was eventually halted since the construction company failed to consult with the indigenous people about the environmental effects (Common Dreams 2012).

Xayaburi Dam, Mekong River, Laos

The Xayaburi Dam in Laos is currently being constructed along the Mekong River and the people in this area fear that the dam will have negative effects on their homes. The people downstream of the dam believe the dam will not allow for the passage of fish, which will devastate the fishing industry. The company that is constructing the dam has indicated that they are using new technology that will allow for the passage of these fish and will minimally affect downstream fishing. Until the engineers of the dam further their construction of the dam and the new technologies, the fate of the Mekong River and its numerous species of fish is unknown (Fawthrop 2013).

The broader context of hydropower and related development on the Mekong is discussed by Bakker 1999 (see references below).

Dams on the Nile: Egypt, Sudan and Ethiopia

The most famous river on the Nile is the Aswan High Dam, which was built in order to provide a steady source of irrigation water and hydroelectric power for Egypt. Completed in 1971, the Dam impounds a huge reservoir, known as Lake Nasser, that flooded the sites of the ancient Egyptian Abu Simbel temples (which were relocated). The dam has successfully evened out the seasonal flow of water, providing irrigation and electric power throughout the year. However, it also traps fertile sediments that used to annually replenish the agricultural fields downstream, and alters sedimentation and erosion patterns (endangering the edges of the Nile Delta). Furthermore, because the reservoir is in an areas with one of the world's highest evaporation rates (virtually no rainfall and very high temperatures), it has led to greatly increased evaporation, reducing the total available water downstream.

Construction of the dam necessitated a treaty with Sudan, because part of Sudanese territory was flooded. This treaty included an agreement on the sharing of the Nile waters. However, Ethiopia was not included in this treaty, and essentially no water was allocated to the use of the Ethiopians. At the time, Ethiopia could not muster the finance to build water projects of its own, and this remained the case through many years of civil war (see Beschorner 1992, Collins 1996). However, this has recently changed. The Grand Renaissance Dam in Ethiopia has been under construction since 2012 and will be the largest hydroelectric dam in Africa once completed. Egypt and Sudan argue that the dam will threaten their greatest natural resource. These countries fear that Ethiopia will have the ability to control the flow of the Nile. This is a major threat considering that 85% of the water that travels to Egypt and Sudan originates in Ethiopia. Ethiopia denies these claims and stressed that machines will control the flow of the river to regulate a steady flow of water (Eastwood and El Bagir 2012). If the three countries come to an agreement about regulating water flows, this would actually provide a chance to shut down the Aswan High Dam, reducing the amount of water that evaporates from the Nile, and thus increasing the total amount of water that is available in the river basin.

Narmada River Dams, India

To be added.

Three Gorges Dam, Changjiang (Yangtse) River, China

To be added

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Ways Forward

Dams continue to be an attractive source of electric power because they do not generate greenhouse gases while they are in use (disregarding the construction and filling phase), and because no water is used in the process of generating power. Also, the hydroelectric dams do not pollute the water as it passes through the turbines and create no type of byproduct through the process. Hydropower is also one of the cheapest sources of power available. However, dams are also costly to build and take large amounts of resources to construct. They take years to build which makes it impossible for any type of immediate return on the investment for construction (which is why they are very often financed by governments). Finally, they can cause massive ecological and social disruptions. How then to move forward?

It should be observed first of all that, if the benefits of a dam indeed exceed its costs to everyone concerned, it should be possible for the developers to pay the full costs. If they are not able to pay the full costs, this is proof that the benefits of the dam do not exceed its costs, and therefore it should not be built. The way to determine what are indeed the full costs of a dam project is to involve all stakeholders in decision-making, and to respect the rights of the people to the land that they use.

It is also vitally important that all possible alternatives be explored, including the use of other types of renewable energy, the use of small and micro-scale hydroelectric projects that could be in community control, and the potential for increased energy efficiency. Again, a participatory process is needed in exploring alternatives. For one approach to doing this, see International Rivers, Introduction to Integrated Resources Planning in the links section below.

When dams are built, it is important to use the least disruptive technologies, such as fish ladders that allow most fish species to travel up and down past the dam.


Approaches Toward Creating Greater Abundance

Repowering existing dams

Increasing energy efficiency


Integrated Resource Planning

Rights to Land of Peasants and Indigenous People

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Friends of River Narmada

International Energy Agency/International Renewable Energy Agency: IEA/IRENA Global Renewable Energy Joint Policies and Measures Database.

International Rivers, an environmental organization to protect rivers, opposing destructive river projects and promoting better options.

International Rivers (Christopher Greacen, Chuenchom Greacen, David von Hippel, and David Bill). 2013. An Introduction to Integrated Resources Planning.

IRENA (International Renewable Energy Agency)

Michigan Department of Natural Resources. Fishladders and Fishways.

Renewable Energy Policy Network for the 21st Century. Renewables 2012 Global Status Report.

Renewable Energy World A network of renewable energy professionals with news and information about renewable sources of energy.

United Nations Development Programme (UNEP). Dams and Development Project.

US Geological Survey (USGS). Hydroelectric Power: How it Works.

World Commission on Dams. 2000. Dams and Development: A New Framework for Decision-making. London: Earthscan.

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Bakker, Karen. 1999. The Politics of Hydropower: Developing the Mekong. Political Geography 18 (2): 209-232.

Beschorner, N. 1992. Water and Instability in the Middle East. Adelphi Paper 273. London: The International Institute for Strategic Studies.

Blackshear, Ben, Tom Crocker, Emma Drucker, John Filoon, Jak Knelman, and Mikaela Skiles. 2011. Hydropower Vulnerability and Climate Change: A Framework for Modeling the Future of Global Hydroelectric Resources. Middlebury College Environmental Studies Senior Seminar.

Bonsor, Kevin. September 2001 (Accessed March 2014). How Hydropower Plants Work. How Stuff Works. How HydroPlants Work.

Collins, Robert. 1996. The Waters of the Nile: Hydropolitics and the Jonglei Canal, 1900-1988. Princeton, NJ: Marcus Wiener.

Common Dreams. 15 August 2012. "A Great Victory": Controversial Brazilian Dam Construction HaltedCommon Dreams.

Eastwood, Victoria, and Nima Elbagir. June 2012. Ethiopia Powers on with Controversial Dam Project. Marketplace Africa. CNN.

Fawthrop, Tom. 13/14 September 2013. Controversial Mekong Dam Could Devastate Local Population. South China Morning Post.

Hammond. Michael. 2013 The Grand Ethiopian Grand Renaissance Dam and the Blue Nile: Implications for transboundary water governance. Global Water Forum Discussion Paper 1307.

Heggelund, Gørild. 2006. Resettlement Programmes and the Environmental Capacity in the Three gorges Dam Project. Development and Change 37 (1): 179-199.

IRENA (International Renewable Energy Agency). 2012. Hydropower. Renewable Energy Technologies: Cost Analysis Series. Volume 1: Power Sector, Issue 3/5.

Office of Energy Efficiency and Renewable Energy (US Department of Energy). History of Hydropower. Accessed March 2014.

Roy, Arundhati. 1999. The Greater Common Good.

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