Hydroelectricity

(electricity) Electric power produced by hydroelectric generators. Also known as hydropower.

Electricity generated from the energy of running water, usually water falling over a dam.

• Only a small proportion of the electricity in the United States is produced by hydroelectric power.

Energy produced as generators are turned by the power of running water. The necessary conditions are a constant supply of water from rivers and lakes, steep slopes to aid the fall of water, and stable geological conditions for the construction of dams.

However, recent research indicates that the construction of dams may trigger off earth movements. The energy generated is a function of the height of falling water as well as of the mass of water concerned. A high proportion of the energy is converted into electricity.

(click to enlarge)
A hydro station generates power by the controlled release of water from the reservoir of a dammed … (credit: © Merriam-Webster Inc.)

Electricity produced from generators driven by water turbines that convert the energy in falling or fast-flowing water to mechanical energy. Water at a higher elevation flows downward through large pipes or tunnels (penstocks). The falling water rotates turbines, which drive the generators, which convert the turbines' mechanical energy into electricity. The advantages of hydroelectric power over such other sources as fossil fuels and nuclear fission are that it is continually renewable and produces no pollution. Norway, Sweden, Canada, and Switzerland rely heavily on hydroelectricity because they have industrialized areas close to mountainous regions with heavy rainfall. The U.S., Russia, China, India, and Brazil get a much smaller proportion of their electric power from hydroelectric generation. See also tidal power.

For more information on hydroelectric power, visit Britannica.com.

The capability to produce and deliver electricity for widespread consumption was one of the most important factors in the surge of American economic influence and wealth in the late nineteenth and early twentieth centuries. Hydroelectric power, among the first and simplest of the technologies that generated electricity, was initially developed using low dams of rock, timber, or granite block construction to collect water from rainfall and surface runoff into a reservoir. The water was funneled into a pipe (or pen-stock) and directed to a waterwheel (or turbine) where the force of the falling water on the turbine blades rotated the turbine and its main shaft. This shaft was connected to a generator, and the rotating generator produced electricity. One gallon (about 3.8 liters) of water falling 100 feet (about 30 meters) each second produced slightly more than 1,000 watts (or one kilowatt) of electricity, enough to power ten 100-watt light bulbs or a typical hairdryer.

There are now three types of hydroelectric installations: storage, run-of-river, and pumped-storage facilities. Storage facilities use a dam to capture water in a reservoir. This stored water is released from the reservoir through turbines at the rate required to meet changing electricity needs or other needs such as flood control, fish passage, irrigation, navigation, and recreation. Run-of-river facilities use only the natural flow of the river to operate the turbine. If the conditions are right, this type of project can be constructed without a dam or with a low diversion structure to direct water from the stream channel into a penstock. Pumped-storage facilities, an innovation of the 1950s, have specially designed turbines. These turbines have the ability to generate electricity the conventional way when water is delivered through penstocks to the turbines from a reservoir. They can also be reversed and used as pumps to lift water from the powerhouse back up into the reservoir where the water is stored for later use. During the daytime when electricity demand suddenly increases, the gates of the pumped-storage facility are opened and stored water is released from the reservoir to generate and quickly deliver electricity to meet the demand. At night when electricity demand is lowest and there is excess electricity available from coal or nuclear electricity generating facilities the turbines are reversed and pump water back into the reservoir. Operating in this manner, a pumped-storage facility improves the operating efficiency of all power plants within an electric system. Hydroelectric developments provide unique benefits not available with other electricity generating technologies. They do not contribute to air pollution, acid rain, or ozone depletion, and do not produce toxic wastes. As a part of normal operations many hydroelectric facilities also provide flood control, water supply for drinking and irrigation, and recreational opportunities such as fishing, swimming, water-skiing, picnicking, camping, rafting, boating, and sightseeing.

Origins of the Hydroelectric Industry 1880–1930

Hydroelectric power technology was slow to develop during the first ten years of the hydroelectric era (1880–1889) due to the limitations of direct current electricity technology. Some pioneering hydropower developments using direct current technology are described below.

The Grand Rapids Electric Light and Power Company in Michigan connected a dynamo to a waterwheel for the Wolverine Chair Factory in July 1880 and this installation powered 16 brush-arc lamps.

A dynamo was connected to a hydropower turbine at Niagara Falls in 1881 to power the arc lamps for the city streets.

The first hydropower facility in the western United States was completed in San Bernardino, California, in 1887.

By 1889 there were about 200 small electric generating facilities in the United States that used water for some or all of their electricity production.

The potential for increasing hydroelectric development was dramatically enhanced in 1889 when alternating current technology was introduced, enabling electricity to be conveyed economically over long distances.

The next 30 years of the modern era of hydroelectric development, 1890 to 1920, began with the construction of individual hydroelectric facilities by towns, cities, cooperatives, and private manufacturing companies for their own specific needs, and ended with the organization of the first utility system in the country. Cities and towns used hydroelectric facilities to provide electricity for trolley systems, streetlights, and individual customers. Cooperatives brought together groups of individuals and businesses to establish a customer pool that could finance and construct hydroelectric facilities for their own needs. Hundreds of small factories and paper mills in New England, the South, and throughout the Midwest constructed hydroelectric facilities for their own specific industrial use. Just prior to World War I, Southern Power Company purchased a large number of hydroelectric facilities from cites, towns, cooperatives, and factories, and consolidated them into the first regional utility power system in the United States. By 1920 hydroelectric facilities supplied 25 percent of the electricity used in the United States.

The hydroelectric industry matured between 1920 and 1930. During this period, electrical grid systems expanded, reaching more customers who were eager to receive and use electricity. Industrial production grew to satisfy the demand for consumer goods, requiring additional electricity. To meet the increasing demand, town and city electrical systems and regional utility systems grew in number and size throughout the more populated areas of the country. By 1930 hydroelectric facilities were delivering almost 30 percent of the nation's electricity needs.

The Hydroelectric Industry Prospers 1930–1980

The hydroelectric industry prospered from 1930 to 1980 for a number of reasons. Considerable federal funding was provided from 1930 through the 1960s for the construction of large federal dams and hydroelectric facilities. A major percentage of the massive increases in electricity required for wartime production during the 1940s was met by the construction of a sizable number of hydroelectric facilities; and to meet escalating electricity needs in response to the dramatic expansion of consumer demand and industrial production throughout the decades of the 1950s, 1960s, and 1970s, many new electric generating facilities, including hydroelectric developments, were constructed.

In the 1930s, major federal funding for new dam and hydroelectric facility development was allocated for three locations: the Tennessee River under authority of the Tennessee Valley Authority (TVA), the Colorado River under authority of the U.S. Bureau of Reclamation (Bureau), and the Columbia River under authority of the Bureau and the U.S. Army Corps of Engineers (COE). The TVA was established during the Great Depression in 1933 to develop multiple-use water resource projects in the Tennessee River system and spur economic development in Tennessee. It began construction in 1935 on a series of dams with hydroelectric facilities, which included almost 30 dams by the time the system was completed in 1956. Most of the TVA growth took place during World War II when the electrical demand necessary to develop the atomic bomb in the region surged by 600 percent between 1939 and 1945.

The Bureau, established in 1902 to promote the development of the western United States through the construction of federal irrigation dams, completed the world famous Hoover Dam on the Colorado River in 1936. Hoover Dam, which opened three years ahead of schedule, was a public works project intended to relieve unemployment during the Great Depression and provide critical electricity to meet the growing needs of the City of Los Angeles, California. At the same time, the Bureau and COE undertook the development of the great dams on the Columbia River in the northwestern United States. Within six years of the initial operation of Hoover, the Bureau completed Grand Coulee Dam on the Columbia

River, still the largest dam in the northwestern United States. During the mid-1940s, Grand Coulee supplied the electricity needed to produce planes and other war material to support U.S. victory in World War II. Bonneville Dam, completed in 1938 by the COE and also located on the Columbia River, was a public works project to help relieve regional unemployment during the Great Depression. Like Grand Couleee, Bonneville also supplied critical electricity in support of World War II production efforts. In 1940 hydroelectric plants supplied more than 35 percent of the nation's electricity.

Grand Coulee and Bonneville, along with the other large hydroelectric projects constructed in the northwest region from the 1940s through the 1960s, supplied between 80 and 90 percent of the electricity consumed in the states of Washington and Oregon by 1980. However, the portion of the nation's electricity supplied by hydroelectric facilities had declined to 12 percent. Federal support for constructing dams where a hydroelectric plant could be included was declining and initial steps were being taken to alter the primary mission of the Bureau and COE from developing new projects to operating and maintaining existing facilities.

Regulation of the Hydroelectric Industry 1899–1986

Hydroelectric power development has always been closely linked to political influences. Federal recognition of the necessity to control development on the nation's waterways began with the passage of the Rivers and Harbors Act in 1899, less than twenty years after the appearance of the first hydroelectric facility. The rapid expansion of interest in natural and water resources led to the creation of the Inland Waterways Commission in 1907. This Commission issued a report advocating a national policy to regulate development on streams or rivers crossing public lands. A White House Natural Resources Conference the following year proposed increased development of the nation's hydroelectric resources. As a result, the Federal Water Power Act (FWPA) was passed in 1920, establishing the Federal Power Commission (FPC) with the authority to issue licenses for non-federal hydroelectric development on public lands and waterways. Recognizing that the FWPA did not extend to all waterways, Congress enacted the Federal Power Act (FPA) in 1935 to amend the FWPA. The FPA extended the FPC's authority to all hydroelectric projects built by utilities engaged in interstate commerce. The FPA also required that the effects of a project on other natural resources be considered along with the electricity to be produced by the project.

From 1940 to 1980, twenty-two federal laws were passed that affect the hydroelectric licensing decisions of the FPC (renamed the Federal Energy Regulatory Commission [FERC] in 1977). Included among these laws are the Fish and Wildlife Coordination Act, Wilderness Act, National Historic Preservation Act, Wild and Scenic Rivers Act, National Environmental Policy Act, Endangered Species Act, Federal Land Policy and Management Act, Soil and Water Resources Conservation Act, Public Utility Regulatory Policies Act, and Energy Security Act. The enactment of these laws coincided with increasing concerns that negative environmental consequences result from dam construction. These concerns included flooding large land areas, disrupting the ecology and the habitat of fish and wildlife, changing the temperature and oxygen balance of the river water, creating a barrier to the movement of fish upstream and downstream, and modifying river flows. By 1980 concerns that the salmon runs in the Columbia River system were in jeopardy prompted congress to pass the Pacific Northwest Power Planning and Conservation Act. This Act established the Northwest Power Planning Council, which is responsible for the protection and recovery of salmon runs in the Columbia River system. The implementation of many of these laws resulted in a more complex and expensive process to obtain a license for a hydroelectric facility.

The Hydroelectric Industry Stabilizes 1986–2000

The Electric Consumers Protection Act (ECPA) of 1986, which increased the focus on non-power issues in the hydroelectric licensing process, has contributed to an increase in development costs to the point where new hydroelectric facilities are often only marginally competitive with other conventional electric generating technologies. Since 1986, the time required to obtain a hydroelectric license has grown from two years to four years and the licensing cost has doubled for projects of all sizes. Even with more efficient technology, hydroelectric generation increased only slightly between 1986 and 2000. By 1986, the average size of all hydroelectric projects in the United States was about 35,500 kilowatts. After 1986, new projects completing the licensing and construction process average less than 5,000 kilowatts in size.

The recent availability of cheap natural gas and the minimal permitting requirements for gas-fired electricity generating plants has resulted in a dramatic increase in the construction of these plants. These gas-fired plants are meeting the increasing electricity demand more economically than other generating resources.

In today's climate of increased environmental awareness, the construction of new dams is often viewed more negatively than in the past. Therefore, the construction of a new dam for hydroelectric generation is rare. Only six hydroelectric projects were constructed between 1991 and 2000 with new dam or diversion structures and all of these structures are less than 30 feet (10 meters) in height. Hydroelectric facilities are installed at only about 2 percent of the nation's dams.

Present Geographical Distribution of the Industry

Almost 70 percent of all U.S. hydroelectric generation is produced in the western United States during an average water year. The northwestern states of Washington, Oregon, Montana, Wyoming, and Idaho generate about 50 percent of all hydroelectric output. The mountains are high and water is plentiful in this region, yielding optimal conditions for hydroelectric generation. Another 20 percent of the nation's hydroelectric output occurs in the southwestern states of Colorado, Utah, Nevada, California, Arizona, and New Mexico. While these states have terrain similar to those in the northwest, the climate is drier. The southeastern states of Virginia, North Carolina, Tennessee, South Carolina, Georgia, Alabama, Mississippi, and Florida contribute about 10 percent of U.S. hydroelectric production. This region includes large TVA and utility dams with hydroelectric plants. The State of New York produces over 8 percent of the nation's hydroelectricity. At a capacity of 2,500,000 kilowatts, the New York Power Authority's Robert Moses Niagara hydroelectric project is the primary contributor of this electricity. The remainder of the country produces 12 percent of U.S. hydroelectric generation.

The Financial Picture of the Hydroelectric Industry

The financial status of the hydroelectric industry is generally healthy due to long equipment life and low maintenance and operating costs. Hydroelectric facilities in the United States had total capital value in 2000 of about $159 billion based on average new facility costs compiled by DOE of $1,700 to $2,300 per kilowatt of capacity. The gross revenue for the industry in 2000 was about $18 billion based on U.S. electricity production of 269 billion kilowatt hours and DOE's $0.066/kilowatt hour estimate for the national average value of electricity. Using DOE's data, net profit for the industry in 2000 was calculated to be about $11 billion after deducting licensing and regulatory costs (about $500 million), capital costs (about $4.6 billion), and operation and maintenance costs (about $1.9 billion). In the mid-1990s, the hydroelectric industry directly employed nearly 48,000 people and their earnings totaled approximately $2.7 billion according to DOE. Another 58,000 people indirectly provided services and material needed to operate and maintain hydroelectric dams and generating facilities. Few businesses that are 125 years old are as efficient and as important to the U.S. economy as the hydroelectric industry.

Future Directions for the Hydroelectric Industry

The hydroelectric industry has been termed "mature" by some who charge that the technical and operational aspects of the industry have changed little in the past 60 years. Recent research initiatives counter this label by establishing new concepts for design and operation that show promise for the industry. A multi-year research project is presently testing new turbine designs and will recommend a final turbine blade configuration that will allow safe passage of more than 98 percent of the fish that are directed through the turbine. The DOE also recently identified more than 30 million kilowatts of untapped hydroelectric capacity that could be constructed with minimal environmental effects at existing dams that presently have no hydroelectric generating facilities, at existing hydroelectric projects with unused potential, and even at a number of sites without dams. Follow-up studies will assess the economic issues associated with this untapped hydroelectric resource. In addition, studies to estimate the hydroelectric potential of undeveloped, small capacity, dispersed sites that could supply electricity to adjacent areas without connecting to a regional electric transmission distribution system are proceeding. Preliminary results from these efforts have improved the visibility of hydroelectric power and provide indications that the hydroelectric power industry will be vibrant and important to the country throughout the next century.

Bibliography

Barnes, Marla. "Tracking the Pioneers of Hydroelectricity." Hydro Review 16 (1997): 46.

Federal Energy Regulatory Commission. Hydroelectric Power Resources of the United States: Developed and Undeveloped. Washington, 1 January 1992.

———. Report on Hydroelectric Licensing Policies, Procedures, and Regulations: Comprehensive Review and Recommendations Pursuant to Section 603 of the Energy Act of 2000. Washington, May 2001.

Foundation for Water and Energy Education. Following Nature's Current: Hydroelectric Power in the Northwest. Salem, Oregon, 1999.

Idaho National Engineering Laboratory and United States Department of Energy—Idaho Operations Office. Hydroelectric Power Industry Economic Benefit Assessment. DOE/ID-10565.Idaho Falls, November 1996.

———. Hydropower Resources at Risk: The Status of Hydropower Regulation and Development 1997. DOE/ID-10603.Idaho Falls, September 1997.

United States Department of Energy, Energy Information Administration. Annual Energy Review 2000. DOE/EIA-0384 (2000).Washington, August 2001.

United States Department of Energy—Idaho Operations Office. Hydropower: Partnership with the Environment. 01-GA50627. Idaho Falls, June 2001.

The Three Gorges Dam, the largest hydro-electric power station in the world.

Renewable energy
Biofuel Biomass Geothermal Hydropower Solar power Tidal power Wave power Wind power

Hydroelectricity is electricity generated by hydropower, i.e., the production of power through use of the gravitational force of falling or flowing water. It is the most widely used form of renewable energy. Once a hydroelectric complex is constructed, the project produces no direct waste, and has a considerably lower output level of the greenhouse gas carbon dioxide (CO₂) than fossil fuel powered energy plants. Worldwide, hydroelectricity supplied an estimated 816 GWe in 2005. This was approximately 20% of the world's electricity, and accounted for about 88% of electricity from renewable sources.^[1]

Contents 1 Electricity generation 2 Industrial hydroelectric plants 3 Small-scale hydro-electric plants 4 Advantages 4.1 Economics 4.2 Greenhouse gas emissions 4.3 Related activities 5 Disadvantages 5.1 Environmental damage 5.2 Greenhouse gas emissions 5.3 Population relocation 5.4 Dam failures 5.5 Affected by flow shortage 6 Comparison with other methods of power generation 7 Countries with the most hydro-electric capacity 8 Old hydro-electric power stations 8.1 Northern hemisphere 8.2 Southern hemisphere 9 Major schemes under construction 10 Proposed major hydroelectric projects 11 Cost 11.1 United States 12 See also 13 Notes 14 References 15 External links

Electricity generation

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Hydraulic turbine and electrical generator.

Hydroelectric dam in cross section

Main article: Electricity generation

Most hydroelectric power comes from the potential energy of dammed water driving a water turbine and generator. In this case the energy extracted from the water depends on the volume and on the difference in height between the source and the water's outflow. This height difference is called the head. The amount of potential energy in water is proportional to the head. To obtain very high head, water for a hydraulic turbine may be run through a large pipe called a penstock.

Pumped storage hydroelectricity produces electricity to supply high peak demands by moving water between reservoirs at different elevations. At times of low electrical demand, excess generation capacity is used to pump water into the higher reservoir. When there is higher demand, water is released back into the lower reservoir through a turbine. Pumped storage schemes currently provide the only commercially important means of large-scale grid energy storage and improve the daily load factor of the generation system. Hydroelectric plants with no reservoir capacity are called run-of-the-river plants, since it is not then possible to store water. A tidal power plant makes use of the daily rise and fall of water due to tides; such sources are highly predictable, and if conditions permit construction of reservoirs, can also be dispatchable to generate power during high demand periods.

Less common types of hydro schemes use water's kinetic energy or undammed sources such as undershot waterwheels.

A simple formula for approximating electric power production at a hydroelectric plant is: P = hrgk, where P is Power in kilowatts, h is height in meters, r is flow rate in cubic meters per second, g is acceleration due to gravity of 9.8 m/s², and k is a coefficient of efficiency ranging from 0 to 1. Efficiency is often higher with larger and more modern turbines.

Annual electric energy production depends on the available water supply. In some installations the water flow rate can vary by a factor of 10:1 over the course of a year.

Industrial hydroelectric plants

While many hydroelectric projects supply public electricity networks, some are created to serve specific industrial enterprises. Dedicated hydroelectric projects are often built to provide the substantial amounts of electricity needed for aluminium electrolytic plants, for example. In the Scottish Highlands there are examples at Kinlochleven and Lochaber, constructed during the early years of the 20th century. The Grand Coulee Dam, long the world's largest, switched to support Alcoa aluminum in Bellingham, Washington for America's World War II airplanes before it was allowed to provide irrigation and power to citizens (in addition to aluminum power) after the war. In Suriname, the Brokopondo Reservoir was constructed to provide electricity for the Alcoa aluminium industry. New Zealand's Manapouri Power Station was constructed to supply electricity to the aluminium smelter at Tiwai Point. As of 2007 the Kárahnjúkar Hydropower Project in Iceland remains controversial.^[2]

Small-scale hydro-electric plants

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Main article: Small hydro

Although large hydroelectric installations generate most of the world's hydroelectricity, some situations require small hydro plants. These are defined as plants producing up to 10 megawatts, or projects up to 30 megawatts in North America. A small hydro plant may be connected to a distribution grid or may provide power only to an isolated community or a single home. Small hydro projects generally do not require the protracted economic, engineering and environmental studies associated with large projects, and often can be completed much more quickly. A small hydro development may be installed along with a project for flood control, irrigation or other purposes, providing extra revenue for project costs. In areas that formerly used waterwheels for milling and other purposes, often the site can be redeveloped for electric power production, possibly eliminating the new environmental impact of any demolition operation. Small hydro can be further divided into mini-hydro, units around 1 MW in size, and micro hydro with units as large as 100 kW down to a couple of kW rating.

Small hydro schemes are particularly popular in China, which has over 50% of world small hydro capacity.^[1]

Small hydro units in the range 1 MW to about 30 MW are often available from multiple manufacturers using standardized "water to wire" packages; a single contractor can provide all the major mechanical and electrical equipment (turbine, generator, controls, switchgear), selecting from several standard designs to fit the site conditions. Micro hydro projects use a diverse range of equipment; in the smaller sizes industrial centrifugal pumps can be used as turbines, with comparatively low purchase cost compared to purpose-built turbines.

Advantages

The upper reservoir and dam of the Ffestiniog pumped storage scheme. 360 megawatts of electricity can be generated within 60 seconds of the need arising.

Economics

The major advantage of hydroelectricity is elimination of the cost of fuel. The cost of operating a hydroelectric plant is nearly immune to increases in the cost of fossil fuels such as oil, natural gas or coal, and no imports are needed.

Hydroelectric plants also tend to have longer economic lives than fuel-fired generation, with some plants now in service which were built 50 to 100 years ago.^[3] Operating labor cost is also usually low, as plants are automated and have few personnel on site during normal operation.

Where a dam serves multiple purposes, a hydroelectric plant may be added with relatively low construction cost, providing a useful revenue stream to offset the costs of dam operation. It has been calculated that the sale of electricity from the Three Gorges Dam will cover the construction costs after 5 to 8 years of full generation.^[4]

Greenhouse gas emissions

Since hydroelectric dams do not burn fossil fuels, they do not directly produce carbon dioxide (a greenhouse gas). While some carbon dioxide is produced during manufacture and construction of the project, this is a tiny fraction of the operating emissions of equivalent fossil-fuel electricity generation.

Related activities

Reservoirs created by hydroelectric schemes often provide facilities for water sports, and become tourist attractions in themselves. In some countries, aquaculture in reservoirs is common. Multi-use dams installed for irrigation support agriculture with a relatively constant water supply. Large hydro dams can control floods, which would otherwise affect people living downstream of the project.

Disadvantages

Recreational users must exercise extreme care when near hydroelectric dams, power plant intakes and spillways.^[5]

Environmental damage

Hydroelectric projects can be disruptive to surrounding aquatic ecosystems both upstream and downstream of the plant site. For instance, studies have shown that dams along the Atlantic and Pacific coasts of North America have reduced salmon populations by preventing access to spawning grounds upstream, even though most dams in salmon habitat have fish ladders installed. Salmon spawn are also harmed on their migration to sea when they must pass through turbines. This has led to some areas transporting smolt downstream by barge during parts of the year. In some cases dams have been demolished (for example the Marmot Dam demolished in 2007)^[6] because of impact on fish. Turbine and power-plant designs that are easier on aquatic life are an active area of research. Mitigation measures such as fish ladders may be required at new projects or as a condition of re-licensing of existing projects.

Generation of hydroelectric power changes the downstream river environment. Water exiting a turbine usually contains very little suspended sediment, which can lead to scouring of river beds and loss of riverbanks.^[7] Since turbine gates are often opened intermittently, rapid or even daily fluctuations in river flow are observed. For example, in the Grand Canyon, the daily cyclic flow variation caused by Glen Canyon Dam was found to be contributing to erosion of sand bars. Dissolved oxygen content of the water may change from pre-construction conditions. Depending on the location, water exiting from turbines is typically much warmer than the pre-dam water, which can change aquatic faunal populations, including endangered species, and prevent natural freezing processes from occurring. Some hydroelectric projects also use canals to divert a river at a shallower gradient to increase the head of the scheme. In some cases, the entire river may be diverted leaving a dry riverbed. Examples include the Tekapo and Pukaki Rivers.

Greenhouse gas emissions

Bonnington hydroelectric power station, River Clyde, Scotland.

The reservoirs of power plants in tropical regions may produce substantial amounts of methane and carbon dioxide. This is due to plant material in flooded areas decaying in an anaerobic environment, and forming methane, a very potent greenhouse gas. According to the World Commission on Dams report, where the reservoir is large compared to the generating capacity (less than 100 watts per square metre of surface area) and no clearing of the forests in the area was undertaken prior to impoundment of the reservoir, greenhouse gas emissions from the reservoir may be higher than those of a conventional oil-fired thermal generation plant.^[8] Although these emissions represent carbon already in the biosphere, not fossil deposits that had been sequestered from the carbon cycle, there is a greater amount of methane due to anaerobic decay, causing greater damage than would otherwise have occurred had the forest decayed naturally.

The pipes supplying water from the River Clyde to Bonnington hydroelectric power station, Scotland.

In boreal reservoirs of Canada and Northern Europe, however, greenhouse gas emissions are typically only 2% to 8% of any kind of conventional fossil-fuel thermal generation. A new class of underwater logging operation that targets drowned forests can mitigate the effect of forest decay.^[9]

In 2007, International Rivers accused hydropower firms for cheating with fake carbon credits under the Clean Development Mechanism (CDM), for hydropower projects already finished or under construction at the moment they applied to join the CDM. These carbon credits – of hydropower projects under the CDM in developing countries – can be sold to companies and governments in rich countries, in order to comply with the Kyoto protocol.^[10]

Population relocation

Another disadvantage of hydroelectric dams is the need to relocate the people living where the reservoirs are planned. In February 2008, it was estimated that 40-80 million people worldwide had been physically displaced as a direct result of dam construction.^[11] In many cases, no amount of compensation can replace ancestral and cultural attachments to places that have spiritual value to the displaced population. Additionally, historically and culturally important sites can be flooded and lost. Such problems have arisen at the Three Gorges Dam project in China, the Clyde Dam in New Zealand and the Ilısu Dam in Southeastern Turkey.

Dam failures

Failures of large dams, while rare, are potentially serious — the Banqiao Dam failure in Southern China resulted in the deaths of 171,000 people and left millions homeless. Dams may be subject to enemy bombardment during wartime, sabotage and terrorism. Smaller dams and micro hydro facilities are less vulnerable to these threats. The creation of a dam in a geologically inappropriate location may cause disasters like the one of the Vajont Dam in Italy, where almost 2000 people died, in 1963.

Affected by flow shortage

Changes in the amount of river flow will correlate with the amount of energy produced by a dam. Because of global warming, the volume of glaciers has decreased, such as the North Cascades glaciers, which have lost a third of their volume since 1950, resulting in stream flows that have decreased by as much as 34%.^[12] The result of diminished river flow can be power shortages in areas that depend heavily on hydroelectric power.

Comparison with other methods of power generation

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The hydroelectric power station of Aswan Dam, Egypt

Hydroelectric reservoir in Vianden, Luxembourg

Hydroelectricity eliminates the flue gas emissions from fossil fuel combustion, including pollutants such as sulfur dioxide, nitric oxide, carbon monoxide, dust, and mercury in the coal. Hydroelectricity also avoids the hazards of coal mining and the indirect health effects of coal emissions. Compared to nuclear power, hydroelectricity generates no nuclear waste, has none of the dangers associated with uranium mining, nor nuclear leaks. Unlike uranium, hydroelectricity is also a renewable energy source.

Compared to wind farms, hydroelectricity power plants have a more predictable load factor. If the project has a storage reservoir, it can be dispatched to generate power when needed. Hydroelectric plants can be easily regulated to follow variations in power demand.

Unlike fossil-fueled combustion turbines, construction of a hydroelectric plant requires a long lead-time for site studies, hydrological studies, and environmental impact assessment. Hydrological data up to 50 years or more is usually required to determine the best sites and operating regimes for a large hydroelectric plant. Unlike plants operated by fuel, such as fossil or nuclear energy, the number of sites that can be economically developed for hydroelectric production is limited; in many areas the most cost effective sites have already been exploited. New hydro sites tend to be far from population centers and require extensive transmission lines. Hydroelectric generation depends on rainfall in the watershed, and may be significantly reduced in years of low rainfall or snowmelt. Long-term energy yield may be affected by climate change. Utilities that primarily use hydroelectric power may spend additional capital to build extra capacity to ensure sufficient power is available in low water years.

In parts of Canada (the provinces of British Columbia, Manitoba, Ontario, Quebec, Newfoundland and Labrador) hydroelectricity is used so extensively that the word "hydro" is often used to refer to any electricity delivered by a power utility. The government-run power utilities in these provinces are called BC Hydro, Manitoba Hydro, Hydro One (formerly "Ontario Hydro"), Hydro-Québec and Newfoundland and Labrador Hydro respectively. Hydro-Québec is the world's largest hydroelectric generating company, with a total installed capacity (2007) of 35,647 MW, including 33,305 MW of hydroelectric generation^[13].

Countries with the most hydro-electric capacity

The ranking of hydro-electric capacity is either by actual annual energy production or by installed capacity power rating. A hydro-electric plant rarely operates at its full power rating over a full year; the ratio between annual average power and installed capacity rating is the capacity factor. The installed capacity is the sum of all generator nameplate power ratings. Sources came from BP Statistical Review - Full Report 2009^[14] List of the largest hydoelectric power stations. Norway produces 98-99% of its electricity from hydroelectric.^[15]

Brazil, Canada, Norway and Venezuela are the only countries in the world where the majority of their internal electric energy production is from hydroelectric power.

Country	Annual Hydroelectric Energy Production(TWh)	Installed Capacity (GW)	Capacity Factor	Percent of all electricity
People's Republic of China(2008)[16]	585.2	171.52	0.37	17.18
Canada	369.5	88.974	0.59	61.12
Brazil	363.8	69.080	0.56	85.56
USA	250.6	79.511	0.42	5.74
Russia	167.0	45.000	0.42	17.64
Norway	140.5	27.528	0.49	98.25[15]
India	115.6	33.600	0.43	15.80
Venezuela	86.8	-	-	67.17
Japan	69.2	27.229	0.37	7.21
Sweden	65.5	16.209	0.46	44.34
Paraguay(2006)	64.0	-	-
France	63.4	25.335	0.25	11.23

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Old hydro-electric power stations

Northern hemisphere

• Appleton, Wisconsin, USA completed 1882, A waterwheel on the Fox river supplied the first commercial hydroelectric power for lighting to two paper mills and a house, two years after Thomas Edison demonstrated incandescent lighting to the public. Within a matter of weeks of this installation, a power plant was also put into commercial service at Minneapolis.

• Niagara Falls, New York. For many years the largest hydroelectric power station in the world. Operation began locally in 1895 and power was transmitted to Buffalo, New York, in 1896.

• Decew Falls 1, St. Catharines, Ontario, Canada completed 25 August 1898. Owned by Ontario Power Generation. Four units are still operational. Recognized as an IEEE Milestone in Electrical Engineering & Computing by the IEEE Executive Committee in 2002.

• Claverack Creek, in Stottville, New York, believed to be the oldest hydro power site in the United States. The turbine, a Morgan Smith, was constructed in 1869 and installed 2 years later. It is one of the earliest water wheel installations in the United States to generate electricity. It is owned today by Edison Hydro.^{[citation needed]}

• The oldest continuously-operated commercial hydroelectric plant in the United States is built on the Hudson River at Mechanicville, New York. The seven 750 kW units at this station initially supplied power at a frequency of 38 Hz, but later were increased in speed to 40 Hz. It went into commercial service July 22,1898. It is now being restored to its original condition and remains in commercial operation.^[17]

• The oldest continuously-operated hydroelectric generator in Canada is located in St. Stephen, New Brunswick, Canada. Part of the construction of the Milltown Cotton Mill, this rope-driven generator originally powered the electric lights for the mill when it opened in 1882, and in 1888 started providing power to homes in the town. NB Power now owns and operates this as part of the Milltown Dam hydroelectric station.

Southern hemisphere

• A small hydroelectric station, generating 650 kW, opened at Waratah, Tasmania, in 1885
• Duck Reach, Launceston, Tasmania. Completed 1895. The first publicly owned hydro-electric plant in the Southern Hemisphere. Supplied power to the city of Launceston for street lighting.
• Chivilingo was the first hydroelectric plant in Chile and the second in South America. With first power produced in 1897, it has two Pelton wheel turbines each turning a 215 kW generator. It was installed to provide power to mines and the city of Lota, Chile.^[18]
• The Snowy Mountains Scheme has turbines all along the tunnel so it, in some perspectives it is also another hydroelectric station. However it only operates during peak hours of the day and mostly during the evening and early night. It supplies electricity to all over the state of NSW.

Major schemes under construction

This section includes a list of references, related reading or external links, but its sources remain unclear because it lacks inline citations. Please improve this article by introducing more precise citations where appropriate. (August 2008)

Only projects with generating capacity greater than or equal to 2,000 MW are listed.

Name	Maximum Capacity	Country	Construction started	Scheduled completion	Comments
Three Gorges Dam	22,500 MW	China	December 14, 1994	2011	Largest power plant in the world. First power in July 2003, with 12,600 MW installed by October 2007.
Xiluodu Dam	12,600 MW	China	December 26, 2005	2015	Construction once stopped due to lack of environmental impact study.
Siang Upper HE Project	11,000 MW	India	April, 2009	2024	Multi-phase construction over a period of 15 years. Construction was delayed due to dispute with China.
Xiangjiaba Dam	6,400 MW	China	November 26, 2006	2015
Longtan Dam	6,300 MW	China	July 1, 2001	December 2009
Nuozhadu Dam	5,850 MW	China	2006	2017
Jinping 2 Hydropower Station	4,800 MW	China	January 30, 2007	2014	To build this dam, 23 families and 129 local residents need to be moved. It works with Jinping 1 Hydropower Station as a group.
Laxiwa Dam	4,200 MW	China	April 18, 2006	2010
Xiaowan Dam	4,200 MW	China	January 1, 2002	December 2012
Jinping 1 Hydropower Station	3,600 MW	China	November 11, 2005	2014
Pubugou Dam	3,300 MW	China	March 30, 2004	2010
Goupitan Dam	3,000 MW	China	November 8, 2003	2011
Guanyinyan Dam	3,000 MW	China	2008	2015	Construction of the roads and spillway started.
Lianghekou Dam[19]	3,000 MW	China	2009	2015
Boguchan Dam	3,000 MW	Russia	1980	2012
Chapetón	3,000 MW	Argentina
Dagangshan	2,600 MW	China	August 15, 2008[20]	2014
Jinanqiao Dam	2,400 MW	China	December 2006	2010
Guandi Dam	2,400 MW	China	Novermber 11 2007	2012
Liyuan Dam	2,400 MW	China	2008[21]
Tocoma Dam Bolívar State	2,160 MW	Venezuela	2004	2014	This new power plant would be the last development in the Low Caroni Basin, bringing the total to six power plants on the same river, including the 10,000MW Guri Dam.[22]
Ludila Dam	2,100 MW	China	2007	2015	Construction halt due to lack of the evnironmental assessment.
Bureya Dam	2,010 MW	Russia	1978	2009
Shuangjiangkou Dam	2,000 MW	China	December, 2007[23]		The dam will be 314 m high.
Ahai Dam	2,000 MW	China	July 27, 2006
Lower Subansiri Dam	2,000 MW	India	2005	2010

Proposed major hydroelectric projects

This section includes a list of references, related reading or external links, but its sources remain unclear because it lacks inline citations. Please improve this article by introducing more precise citations where appropriate. (August 2008)

Only projects with generating capacity greater than or equal to 2,000 MW are listed.

Name	Maximum Capacity	Country	Construction starts	Scheduled completion	Comments
Red Sea dam	50,000 MW	Middle East	Unknown	Unknown	Still in planning, would be largest dam in the world
Grand Inga	40,000 MW	Democratic Republic of the Congo	2010	Unknown
Baihetan Dam	13,050 MW	China	2009	2015	Still in planning
Wudongde Dam	7,500 MW	China	2009	2015	Still in planning
Rampart Dam	4,500 MW	United States			Canceled
Maji Dam	4,200 MW	China	2008	2013
Songta Dam	4,200 MW	China	2008	2013
Liangjiaren Dam	4,000 MW	China	2009	2015	Still in planning
Jirau Dam	3,300 MW	Brazil	2007	2012
Pati Dam	3,300 MW	Argentina
Santo Antônio Dam	3,150 MW	Brazil	2007	2012
Dibang	3,000 MW	India
Lower Churchill	2,800 MW	Canada	2009	2014
HidroAysén	2,750 MW	Chile		2020
Lenggu Dam	2,718 MW	China	2015
Subansiri Upper HE Project	2,500 MW	India	2012	Unknown
Changheba Dam	2,200 MW	China	2009	2015
Banduo 1 Dam	2,000 MW	China	2009

Cost

United States

In the United States, a study is required before constructing a hydroelectric project. In 2008, a study could cost up to $50,000 for a 100 feet (30 m) run of a stream. Both federal and state licenses were required. A license typically cost between $150,000 and $1 million. A project earns money from the sale of energy, the sale of capacity, and the sale of renewable energy credits.^[24]

See also

Renewable energy
Biofuel Biomass Geothermal Hydropower Solar power Tidal power Wave power Wind power

Energy portal

Topics:

• Environmental concerns with electricity generation
• Environmental impacts of dams
• Hydropower
• Pumped-storage hydroelectricity
• Run-of-the-river hydroelectricity
• Small hydro
• Water power engine

Lists:

• List of countries by electricity production from renewable sources
• List of the largest hydroelectric power stations
• List of reservoirs and dams

Categories:

• Category:Hydroelectric power plants by country

Organisations:

• International Hydropower Association (IHA)

Notes

1. ^ ^{a b} Renewables Global Status Report 2006 Update, REN21, published 2007, accessed 2007-05-16; see Table 4, p. 20.
2. ^ Summer of International dissent against Heavy Industry, Saving Iceland, published 2007, accessed 2007-05-17
3. ^ Hydropower – A Way of Becoming Independent of Fossil Energy?
4. ^ Beyond Three Gorges in China
5. ^ Stay Clear, Stay Safe, Ontario Power Generation
6. ^ "Sandy River – Marmot Dam’s removal in 2007 has returned the Sandy River to a wild, free-flowing river". Portland General Electric. http://www.portlandgeneral.com/community_and_env/hydropower_and_fish/sandy/default.aspx. Retrieved on 2009-05-10. 
7. ^ Sedimentation Problems with Dams
8. ^ Hydroelectric power's dirty secret revealed
9. ^ Inhabitat » “Rediscovered” Wood & The Triton Sawfish
10. ^ Nick Davies (3 December 2007). "Power firms accused of emissions trade cheating". The Guardian. http://www.guardian.co.uk/environment/2007/dec/03/climatechange.greenpolitics1. Retrieved on 2009-05-10. 
11. ^ Briefing of World Commission on Dams
12. ^ Gregoire, Christine (2008) (PDF), Executive Order 07-02: Washington Climate Change Challenge, http://governor.wa.gov/execorders/eo_07-02.pdf .
13. ^ Hydro-Québec. 2007 Annual Report. Montreal, April 2008.
14. ^ Consumption TWh'!A1
15. ^ ^{a b} "Binge and purge". The Economist. 2009. http://www.economist.com/displaystory.cfm?story_id=12970769. Retrieved on 2009-01-30. "98-99% of Norway’s electricity comes from hydroelectric plants." 
16. ^ [1]
17. ^ The Historic Mechanicville Hydroelectric Station Part 1: The Early Days, IEEE Industry Applications Magazine, Jan/Feb. 2007
18. ^ Carl Sulzberger, The Chivilingo Plant- Early Hydropower in Chile, in IEEE Power & Energy, Volume 6, No. 4 July/August 2008, ISSN 1540-7977, pg. 60
19. ^ http://www.ehdc.com.cn/newsite/DisplayNewsMaster/ShowNews.aspx?Id=1175
20. ^ http://www.cb600.cn/info_view.asp?id=1357280
21. ^ http://zt.xxgk.yn.gov.cn/canton_model12/newsview.aspx?id=368628
22. ^ Staff (2004). "Caroní River Watershed Management Plan" (PDF). Inter-America Development Bank. http://idbgroup.org/exr/doc98/pro/pvel1003-06eng.pdf. Retrieved on 2008-10-25. 
23. ^ http://www.cjwsjy.com.cn/News/Company/200808055706.htm
24. ^ Gresser, Joseph (August 20, 2008). Panel considers small hydro power potential. the Chronicle. 

References

• World Commission on Dams (November 16, 2000). "Dams and Development – A New Framework for Decision-Making". http://dams.org/report/. Retrieved on 2009-05-10. 
• New Scientist report on greenhouse gas production by hydroelectric dams.
• International Water Power and Dam Construction Venezuela country profile
• International Water Power and Dam Construction Canada country profile
• Tremblay, Varfalvy, Roehm and Garneau. 2005. Greenhouse Gas Emissions - Fluxes and Processes, Springer, 732 p.

External links

Wikimedia Commons has media related to: Hydroelectric power

• International Hydropower Association
• Hydroelectricity at the Open Directory Project
• Mechanicville Hydroelectric Station Tour at YouTube
• National Hydropower Association, USA
• Hydropower Reform Coalition, USA
• Interactive site that demonstrates dams' effects on rivers
• Center of expertise on hydropower impacts on fish and fish habitat, Canada
• Hydro-Québec
• CBC Digital Archives – Hydroelectricity: The Power of Water
• University of Washington Libraries – Seattle Power and Water Supply Collection
• International Rivers
• United States Federal Energy Regulatory Commission (FERC)
• European Small Hydropower Association
• Power at Niagara Falls Niagara Falls Public Library (Ont.)
• Milford Hydroelectric Station Restoration Tour Built by Henry Ford in 1939
• 60,000,000 Horsepower Ready to be Harnessed for Work: when these giants are set in action, the real age of electricity will begin and our dreams will become realities, Popular Science monthly, February 1919, page 46-47, Scanned by Google Books: http://books.google.com/books?id=7igDAAAAMBAJ&pg=PA46

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