THC Science

The Three Gorges Dam in Central China is the world's largest power producing facility of any kind.

Hydroelectricity is electricity produced from hydropower. In 2015 hydropower generated 16.6% of the world's total electricity and 70% of all renewable electricity,^[1] and was expected to increase about 3.1% each year for the next 25 years.

Hydropower is produced in 150 countries, with the Asia-Pacific region generating 33 percent of global hydropower in 2013. China is the largest hydroelectricity producer, with 920 TWh of production in 2013, representing 16.9 percent of domestic electricity use.

The cost of hydroelectricity is relatively low, making it a competitive source of renewable electricity. The hydro station consumes no water, unlike coal or gas plants. The average cost of electricity from a hydro station larger than 10 megawatts is 3 to 5 U.S. cents per kilowatt-hour.^[2] With a dam and reservoir it is also a flexible source of electricity since the amount produced by the station can be changed up or down very quickly to adapt to changing energy demands. Once a hydroelectric complex is constructed, the project produces no direct waste, and in many cases, has a considerably lower output level of greenhouse gases than fossil fuel powered energy plants.^[3]

History

Hydropower has been used since ancient times to grind flour and perform other tasks. In the mid-1770s, French engineer Bernard Forest de Bélidor published Architecture Hydraulique which described vertical- and horizontal-axis hydraulic machines. By the late 19th century, the electrical generator was developed and could now be coupled with hydraulics.^[5] The growing demand for the Industrial Revolution would drive development as well.^[6] In 1878 the world's first hydroelectric power scheme was developed at Cragside in Northumberland, England by William Armstrong. It was used to power a single arc lamp in his art gallery.^[7] The old Schoelkopf Power Station No. 1 near Niagara Falls in the U.S. side began to produce electricity in 1881. The first Edison hydroelectric power station, the Vulcan Street Plant, began operating September 30, 1882, in Appleton, Wisconsin, with an output of about 12.5 kilowatts.^[8] By 1886 there were 45 hydroelectric power stations in the U.S. and Canada. By 1889 there were 200 in the U.S. alone.^[5]

At the beginning of the 20th century, many small hydroelectric power stations were being constructed by commercial companies in mountains near metropolitan areas. Grenoble, France held the International Exhibition of Hydropower and Tourism with over one million visitors. By 1920 as 40% of the power produced in the United States was hydroelectric, the Federal Power Act was enacted into law. The Act created the Federal Power Commission to regulate hydroelectric power stations on federal land and water. As the power stations became larger, their associated dams developed additional purposes to include flood control, irrigation and navigation. Federal funding became necessary for large-scale development and federally owned corporations, such as the Tennessee Valley Authority (1933) and the Bonneville Power Administration (1937) were created.^[6] Additionally, the Bureau of Reclamation which had begun a series of western U.S. irrigation projects in the early 20th century was now constructing large hydroelectric projects such as the 1928 Hoover Dam.^[9] The U.S. Army Corps of Engineers was also involved in hydroelectric development, completing the Bonneville Dam in 1937 and being recognized by the Flood Control Act of 1936 as the premier federal flood control agency.^[10]

Hydroelectric power stations continued to become larger throughout the 20th century. Hydropower was referred to as white coal for its power and plenty.^[11] Hoover Dam's initial 1,345 MW power station was the world's largest hydroelectric power station in 1936; it was eclipsed by the 6809 MW Grand Coulee Dam in 1942.^[12] The Itaipu Dam opened in 1984 in South America as the largest, producing 14,000 MW but was surpassed in 2008 by the Three Gorges Dam in China at 22,500 MW. Hydroelectricity would eventually supply some countries, including Norway, Democratic Republic of the Congo, Paraguay and Brazil, with over 85% of their electricity. The United States currently has over 2,000 hydroelectric power stations that supply 6.4% of its total electrical production output, which is 49% of its renewable electricity.^[6]

Future potential

The technical potential for the growth of hydropower around the world are, 71% Europe, 75% North America, 79% South America, 95% Africa, 95% Middle East, 82% Asia Pacific. The political realities of new reservoirs in western countries, economic limitations in the third world and the lack of a transmission system in undeveloped areas, result in the possibility of developing 25% of the remaining potential before 2050, with the bulk of that being in the Asia Pacific area.^[13] A few countries are highly developed and have very little room for growth, Switzerland 12% and Mexico 20%.

Generating methods

Conventional (dams)

Most hydroelectric power comes from the potential energy of dammed water driving a water turbine and generator. The power 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. A large pipe (the "penstock") delivers water from the reservoir to the turbine.^[14]

Pumped-storage

This method produces electricity to supply high peak demands by moving water between reservoirs at different elevations. At times of low electrical demand, the excess generation capacity is used to pump water into the higher reservoir. When the demand becomes greater, water is released back into the lower reservoir through a turbine. Pumped-storage schemes currently provide the most commercially important means of large-scale grid energy storage and improve the daily capacity factor of the generation system. Pumped storage is not an energy source, and appears as a negative number in listings.^[15]

Run-of-the-river

Run-of-the-river hydroelectric stations are those with small or no reservoir capacity, so that only the water coming from upstream is available for generation at that moment, and any oversupply must pass unused. A constant supply of water from a lake or existing reservoir upstream is a significant advantage in choosing sites for run-of-the-river. In the United States, run of the river hydropower could potentially provide 60,000 megawatts (80,000,000 hp) (about 13.7% of total use in 2011 if continuously available).^[16]

Tide

A tidal power station makes use of the daily rise and fall of ocean 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 water wheels. Tidal power is viable in a relatively small number of locations around the world. In Great Britain, there are eight sites that could be developed, which have the potential to generate 20% of the electricity used in 2012.^[17]

Sizes, types and capacities of hydroelectric facilities

Large facilities

Large-scale hydroelectric power stations are more commonly seen as the largest power producing facilities in the world, with some hydroelectric facilities capable of generating more than double the installed capacities of the current largest nuclear power stations.

Although no official definition exists for the capacity range of large hydroelectric power stations, facilities from over a few hundred megawatts are generally considered large hydroelectric facilities.

Currently, only four facilities over 10 GW (10,000 MW) are in operation worldwide, see table below.^[2]

Rank	Station	Country	Location	Capacity (MW)
1.	Three Gorges Dam	China	30°49′15″N 111°00′08″E / 30.82083°N 111.00222°E / 30.82083; 111.00222 (Three Gorges Dam)	22,500
2.	Itaipu Dam	Brazil Paraguay	25°24′31″S 54°35′21″W / 25.40861°S 54.58917°W / -25.40861; -54.58917 (Itaipu Dam)	14,000
3.	Xiluodu Dam	China	28°15′35″N 103°38′58″E / 28.25972°N 103.64944°E / 28.25972; 103.64944 (Xiluodu Dam)	13,860
4.	Guri Dam	Venezuela	07°45′59″N 62°59′57″W / 7.76639°N 62.99917°W / 7.76639; -62.99917 (Guri Dam)	10,200

Panoramic view of the Itaipu Dam, with the spillways (closed at the time of the photo) on the left. In 1994, the American Society of Civil Engineers elected the Itaipu Dam as one of the seven modern Wonders of the World.^[18]

Small

Small hydro is the development of hydroelectric power on a scale serving a small community or industrial plant. The definition of a small hydro project varies but a generating capacity of up to 10 megawatts (MW) is generally accepted as the upper limit of what can be termed small hydro. This may be stretched to 25 MW and 30 MW in Canada and the United States. Small-scale hydroelectricity production grew by 28% during 2008 from 2005, raising the total world small-hydro capacity to 85 GW. Over 70% of this was in China (65 GW), followed by Japan (3.5 GW), the United States (3 GW), and India (2 GW).^[19]

Small hydro stations may be connected to conventional electrical distribution networks as a source of low-cost renewable energy. Alternatively, small hydro projects may be built in isolated areas that would be uneconomic to serve from a network, or in areas where there is no national electrical distribution network. Since small hydro projects usually have minimal reservoirs and civil construction work, they are seen as having a relatively low environmental impact compared to large hydro. This decreased environmental impact depends strongly on the balance between stream flow and power production.

Micro

Micro hydro is a term used for hydroelectric power installations that typically produce up to 100 kW of power. These installations can provide power to an isolated home or small community, or are sometimes connected to electric power networks. There are many of these installations around the world, particularly in developing nations as they can provide an economical source of energy without purchase of fuel.^[20] Micro hydro systems complement photovoltaic solar energy systems because in many areas, water flow, and thus available hydro power, is highest in the winter when solar energy is at a minimum.

Pico

Pico hydro is a term used for hydroelectric power generation of under 5 kW. It is useful in small, remote communities that require only a small amount of electricity. For example, to power one or two fluorescent light bulbs and a TV or radio for a few homes.^[21] Even smaller turbines of 200-300W may power a single home in a developing country with a drop of only 1 m (3 ft). A Pico-hydro setup is typically run-of-the-river, meaning that dams are not used, but rather pipes divert some of the flow, drop this down a gradient, and through the turbine before returning it to the stream.

Underground

An underground power station is generally used at large facilities and makes use of a large natural height difference between two waterways, such as a waterfall or mountain lake. An underground tunnel is constructed to take water from the high reservoir to the generating hall built in an underground cavern near the lowest point of the water tunnel and a horizontal tailrace taking water away to the lower outlet waterway.

Measurement of the tailrace and forebay rates at the Limestone Generating Station in Manitoba, Canada.

Calculating available power

A simple formula for approximating electric power production at a hydroelectric station is: $P=\rho hrgk$ , where

$P$ is Power in watts,
$\rho$ is the density of water (~1000 kg/m³),
$h$ is height in meters,
$r$ is flow rate in cubic meters per second,
$g$ is acceleration due to gravity of 9.8 m/s²,
$k$ is a coefficient of efficiency ranging from 0 to 1. Efficiency is often higher (that is, closer to 1) 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.

Properties

Advantages

The Ffestiniog Power Station can generate 360 MW of electricity within 60 seconds of the demand arising.

Flexibility

Hydropower is a flexible source of electricity since stations can be ramped up and down very quickly to adapt to changing energy demands.^[2] Hydro turbines have a start-up time of the order of a few minutes.^[22] It takes around 60 to 90 seconds to bring a unit from cold start-up to full load; this is much shorter than for gas turbines or steam plants.^[23] Power generation can also be decreased quickly when there is a surplus power generation.^[24] Hence the limited capacity of hydropower units is not generally used to produce base power except for vacating the flood pool or meeting downstream needs.^[25] Instead, it serves as backup for non-hydro generators.^[24]

Low cost/high value power

The major advantage of conventional hydroelectric dams with reservoirs is their ability to store water at low cost for dispatch later as high value clean electricity. The average cost of electricity from a hydro station larger than 10 megawatts is 3 to 5 U.S. cents per kilowatt-hour.^[2] When used as peak power to meet demand, hydroelectricity has a higher value than base power and a much higher value compared to intermittent energy sources.

Hydroelectric stations have long economic lives, with some plants still in service after 50–100 years.^[26] 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 station 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.^[27] Additionally, some data shows that in most countries large hydropower dams will be too costly and take too long to build to deliver a positive risk adjusted return, unless appropriate risk management measures are put in place.^[28]

Suitability for industrial applications

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. The Grand Coulee Dam switched to support Alcoa aluminium in Bellingham, Washington, United States for American World War II airplanes before it was allowed to provide irrigation and power to citizens (in addition to aluminium 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.

Reduced CO₂ emissions

Since hydroelectric dams do not use fuel, power generation does not produce carbon dioxide. While carbon dioxide is initially produced during construction of the project, and some methane is given off annually by reservoirs, hydro in specific nordic cases, has the lowest lifecycle greenhouse gas emissions for power generation.^[29] Compared to fossil fuels generating an equivalent amount of electricity, hydro displaced three billion tonnes of CO2 emissions in 2011.^[30] One measurement of greenhouse gas related and other externality comparison between energy sources can be found in the ExternE project by the Paul Scherrer Institute and the University of Stuttgart which was funded by the European Commission.^[31] According to that study, hydroelectricity in Europe produces the least amount of greenhouse gases and externality of any energy source.^[32] Coming in second place was wind, third was nuclear energy, and fourth was solar photovoltaic.^[32] The low greenhouse gas impact of hydroelectricity is found especially in temperate climates. The above study was for local energy in Europe; presumably similar conditions prevail in North America and Northern Asia, which all see a regular, natural freeze/thaw cycle (with associated seasonal plant decay and regrowth). Greater greenhouse gas emission impacts are found in the tropical regions because the reservoirs of power stations in tropical regions produce a larger amount of methane than those in temperate areas.^[33]

Other uses of the reservoir

Reservoirs created by hydroelectric schemes often provide facilities for water sports, and become tourist attractions 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.^[34]

Disadvantages

Ecosystem damage and loss of land

Merowe Dam in Sudan. Hydroelectric power stations that use dams submerge large areas of land due to the requirement of a reservoir. These changes to land color or albedo, alongside certain projects that concurrently submerge rainforests, can in these specific cases, result in the global warming impact, or equivalent life-cycle greenhouse gases of hydroelectricity projects, to exceed that of coal power stations.

Large reservoirs associated with traditional hydroelectric power stations result in submersion of extensive areas upstream of the dams, sometimes destroying biologically rich and productive lowland and riverine valley forests, marshland and grasslands. Damming interrupts the flow of rivers and can harm local ecosystems, and building large dams and reservoirs often involves displacing people and wildlife.^[2] The loss of land is often exacerbated by habitat fragmentation of surrounding areas caused by the reservoir.^[35]

Hydroelectric projects can be disruptive to surrounding aquatic ecosystems both upstream and downstream of the plant site. 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.^[36] Since turbine gates are often opened intermittently, rapid or even daily fluctuations in river flow are observed.

Water loss by evaporation

A 2011 study by the United States National Renewable Energy Laboratory concluded that hydroelectric plants in the U.S. consumed between 1,425 and 18,000 gallons of water per megawatt-hour (gal/MWh) of electricity generated, through evaporation losses in the reservoir. The median loss was 4,491 gal/MWh, which is higher than the loss for generation technologies that use cooling towers, including concentrating solar power (865 gal/MWh for CSP trough, 786 gal/MWh for CSP tower), coal (687 gal/MWh), nuclear (672 gal/MWh), and natural gas (198 gal/MWh). Where there are multiple uses of reservoirs such as water supply, recreation, and flood control, all reservoir evaporation is attributed to power production.^[37]

Siltation and flow shortage

When water flows it has the ability to transport particles heavier than itself downstream. This has a negative effect on dams and subsequently their power stations, particularly those on rivers or within catchment areas with high siltation. Siltation can fill a reservoir and reduce its capacity to control floods along with causing additional horizontal pressure on the upstream portion of the dam. Eventually, some reservoirs can become full of sediment and useless or over-top during a flood and fail.^[38]^[39]

Changes in the amount of river flow will correlate with the amount of energy produced by a dam. Lower river flows will reduce the amount of live storage in a reservoir therefore reducing the amount of water that can be used for hydroelectricity. The result of diminished river flow can be power shortages in areas that depend heavily on hydroelectric power. The risk of flow shortage may increase as a result of climate change.^[40] One study from the Colorado River in the United States suggest that modest climate changes, such as an increase in temperature in 2 degree Celsius resulting in a 10% decline in precipitation, might reduce river run-off by up to 40%.^[40] Brazil in particular is vulnerable due to its heavy reliance on hydroelectricity, as increasing temperatures, lower water ﬂow and alterations in the rainfall regime, could reduce total energy production by 7% annually by the end of the century.^[40]

Methane emissions (from reservoirs)

Lower positive impacts are found in the tropical regions, as it has been noted that the reservoirs of power plants in tropical regions produce substantial amounts of methane. This is due to plant material in flooded areas decaying in an anaerobic environment, and forming methane, a greenhouse gas. According to the World Commission on Dams report,^[41] 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.^[42]

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.^[43]

Relocation

Another disadvantage of hydroelectric dams is the need to relocate the people living where the reservoirs are planned. In 2000, the World Commission on Dams estimated that dams had physically displaced 40-80 million people worldwide.^[44]

Failure risks

Because large conventional dammed-hydro facilities hold back large volumes of water, a failure due to poor construction, natural disasters or sabotage can be catastrophic to downriver settlements and infrastructure.

During Typhoon Nina in 1975 Banqiao Dam failed in Southern China when more than a year's worth of rain fell within 24 hours. The resulting flood resulted in the deaths of 26,000 people, and another 145,000 from epidemics. Millions were left homeless.

The creation of a dam in a geologically inappropriate location may cause disasters such as 1963 disaster at Vajont Dam in Italy, where almost 2,000 people died.^[45]

The Malpasset Dam failure in Fréjus on the French Riviera (Côte d'Azur), southern France, collapsed on December 2, 1959, killing 423 people in the resulting flood.^[46]

Smaller dams and micro hydro facilities create less risk, but can form continuing hazards even after being decommissioned. For example, the small earthen embankment Kelly Barnes Dam failed in 1977, twenty years after its power station was decommissioned; causing 39 deaths.^[47]

Comparison and interactions with other methods of power generation

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.

Nuclear power

Compared to nuclear power, hydroelectricity construction requires altering large areas of the environment while a nuclear power station has a small footprint, and hydro-powerstation failures have caused tens of thousands of more deaths than any nuclear station failure.^[35]^[45]^[47] The creation of Garrison Dam, for example, required Native American land to create Lake Sakakawea, which has a shoreline of 1,320 miles, and caused the inhabitants to sell 94% of their arable land for $7.5 million in 1949.^[48]

However, nuclear power is relatively inflexible; although nuclear power can reduce its output reasonably quickly. Since the cost of nuclear power is dominated by its high infrastructure costs, the cost per unit energy goes up significantly with low production. Because of this, nuclear power is mostly used for baseload. By way of contrast, hydroelectricity can supply peak power at much lower cost. Hydroelectricity is thus often used to complement nuclear or other sources for load following. Country examples were they are paired in a close to 50/50 share include the electric grid in Switzerland, the Electricity sector in Sweden and to a lesser extent, Ukraine and the Electricity sector in Finland.

Wind power

Wind power goes through predictable variation by season, but is intermittent on a daily basis. Maximum wind generation has little relationship to peak daily electricity consumption, the wind may peak at night when power isn't needed or be still during the day when electrical demand is highest. Occasionally weather patterns can result in low wind for days or weeks at a time, a hydroelectric reservoir capable of storing weeks of output is useful to balance generation on the grid. Peak wind power can be offset by minimum hydropower and minimum wind can be offset with maximum hydropower. In this way the easily regulated character of hydroelectricity is used to compensate for the intermittent nature of wind power. Conversely, in some cases wind power can be used to spare water for later use in dry seasons.

In areas that do not have hydropower, pumped storage serves a similar role, but at a much higher cost and 20% lower efficiency. An example of this is Norway's trading with Sweden, Denmark, the Netherlands and possibly Germany or the UK in the future.^[49] Norway is 98% hydropower, while it's flatland neighbors are installing wind power.

World hydroelectric capacity

The ranking of hydro-electric capacity is either by actual annual energy production or by installed capacity power rating. In 2015 hydropower generated 16.6% of the worlds total electricity and 70% of all renewable electricity.^[1] Hydropower is produced in 150 countries, with the Asia-Pacific region generated 32 percent of global hydropower in 2010. China is the largest hydroelectricity producer, with 721 terawatt-hours of production in 2010, representing around 17 percent of domestic electricity use. Brazil, Canada, New Zealand, Norway, Paraguay, Austria, Switzerland, and Venezuela have a majority of the internal electric energy production from hydroelectric power. Paraguay produces 100% of its electricity from hydroelectric dams, and exports 90% of its production to Brazil and to Argentina. Norway produces 98–99% of its electricity from hydroelectric sources.^[50]

A hydro-electric station 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.^[51]

Ten of the largest hydroelectric producers as at 2014.^[50]^[52]^[53]
Country	Annual hydroelectric production (TWh)	Installed capacity (GW)	Capacity factor	% of total production
China	1064	311	0.37	18.7%
Canada	383	76	0.59	58.3%
Brazil	373	89	0.56	63.2%
United States	282	102	0.42	6.5%
Russia	177	51	0.42	16.7%
India	132	40	0.43	10.2%
Norway	129	31	0.49	96.0%
Japan	87	50	0.37	8.4%
Venezuela	87	15	0.67	68.3%
France	69	25	0.46	12.2%

Major projects under construction

Name	Maximum Capacity (MW)	Country	Construction started	Scheduled completion	Comments
Belo Monte Dam	11,181	Brazil	March, 2011	2015	Preliminary construction underway.^[54] Construction suspended 14 days by court order Aug 2012^[55]
Siang Upper HE Project	11,000	India	April, 2009	2024	Multi-phase construction over a period of 15 years. Construction was delayed due to dispute with China.^[56]
Tasang Dam	7,110	Burma	March, 2007	2022	Controversial 228 meter tall dam with capacity to produce 35,446 GWh annually.
Xiangjiaba Dam	6,400	China	November 26, 2006	2015	The last generator was commissioned on July 9, 2014
Grand Ethiopian Renaissance Dam	6,000	Ethiopia	2011	2017	Located in the upper Nile Basin, drawing complaint from Egypt
Nuozhadu Dam	5,850	China	2006	2017
Jinping 2 Hydropower Station	4,800	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.
Diamer-Bhasha Dam	4,500	Pakistan	October 18, 2011	2023
Jinping 1 Hydropower Station	3,600	China	November 11, 2005	2014	The sixth and final generator was commissioned on 15 July 2014
Jirau Power Station	3,300	Brazil	2008	2013	Construction halted in March 2011 due to worker riots.^[57]
Guanyinyan Dam	3,000	China	2008	2015	Construction of the roads and spillway started.
Lianghekou Dam^[58]	3,000	China	2014	2023
Dagangshan Dam	2,600	China	August 15, 2008^[59]	2016
Liyuan Dam	2,400	China	2008^[60]	2013
Tocoma Dam Bolívar State	2,160	Venezuela	2004	2014	This power station would be the last development in the Low Caroni Basin, bringing the total to six power stations on the same river, including the 10,000MW Guri Dam.^[61]
Ludila Dam	2,100	China	2007	2015	Brief construction halt in 2009 for environmental assessment.
Shuangjiangkou Dam	2,000	China	December, 2007^[62]	2018	The dam will be 312 m high.
Ahai Dam	2,000	China	July 27, 2006	2015
Teles Pires Dam	1,820	Brazil	2011	2015
Site C Dam	1,100	Canada	2015	2024	First large dam in western Canada since 1984
Lower Subansiri Dam	2,000	India	2007	2016

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^ John Macknick and others, A Review of Operational Water Consumption and Withdrawal Factors for Electricity Generating Technologies, National Renewable Energy Laboratory, Technical Report NREL/TP-6A20-50900.
^ Patrick James, H Chansen (1998). "Teaching Case Studies in Reservoir Siltation and Catchment Erosion" (PDF). Great Britain: TEMPUS Publications. pp. 265–275. Archived from the original (PDF) on 2009-09-02. {{cite web}}: Unknown parameter |deadurl= ignored (|url-status= suggested) (help)
^ Șentürk, Fuat (1994). Hydraulics of dams and reservoirs (reference. ed.). Highlands Ranch, Colo.: Water Resources Publications. p. 375. ISBN 0-918334-80-2.
^ ^a ^b ^c Frauke Urban and Tom Mitchell 2011. Climate change, disasters and electricity generation Archived September 20, 2012, at the Wayback Machine. London: Overseas Development Institute and Institute of Development Studies
^ "WCD Findal Report". Dams.org. 2000-11-16. Archived from the original on 2013-08-21. {{cite web}}: Unknown parameter |deadurl= ignored (|url-status= suggested) (help)
^ "Hydroelectric power's dirty secret revealed". Newscientist.com.
^ ""Rediscovered" Wood & The Triton Sawfish". Inhabitat. 2006-11-16.
^ "Briefing of World Commission on Dams". Internationalrivers.org. 2008-02-29.
^ ^a ^b References may be found in the list of Dam failures.
^ http://ecolo.org/documents/documents_in_french/malpasset/malpasset.htm retrieved 02sep2015
^ ^a ^b Toccoa Flood USGS Historical Site, retrieved 02sep2009
^ Lawson, Michael L. (1982). Dammed Indians: the Pick-Sloan Plan and the Missouri River Sioux, 1944–1980. Norman: University of Oklahoma Press.
^ https://www.sintef.no/en/latest-news/norway-is-europes-cheapest-battery/
^ ^a ^b "Binge and purge". The Economist. 2009-01-22. Retrieved 2009-01-30. 98-99% of Norway's electricity comes from hydroelectric plants. {{cite news}}: Cite has empty unknown parameter: |coauthors= (help)
^ Consumption BP.com^{[dead link]}
^ "2015 Key World Energy Statistics" (PDF). report. International Energy Agency (IEA). Retrieved 1 June 2016.
^ "Indicators 2009, National Electric Power Industry". Chinese Government. Retrieved 18 July 2010.
^ "Belo Monte hydroelectric dam construction work begins". Guardian UK. 10 March 2011. Retrieved 2 April 2011.
^ "Belo Monte dam construction halted by Brazilian court". Guardian UK. 16 August 2012. Retrieved 24 August 2012.
^ "Upper Siang project likely to be relocated on Chinese concerns". Thehindubusinessline.com. 2006-03-24. Retrieved 2012-07-22.
^ "Brazil Sends Forces to Jirau Dam After Riots". Wall Street Journal. 18 March 2011. Retrieved 2 April 2011.
^ "二滩水电开发有限责任公司". Ehdc.com.cn. 2009-04-25. Archived from the original on 2012-10-18. Retrieved 2012-07-22. {{cite web}}: Unknown parameter |deadurl= ignored (|url-status= suggested) (help)
^ "Archived copy". Archived from the original on 2011-07-07. Retrieved 2008-12-12. {{cite web}}: Unknown parameter |deadurl= ignored (|url-status= suggested) (help)CS1 maint: archived copy as title (link)
^ "陆良县人口和计划生育局". Zt.xxgk.yn.gov.cn. Archived from the original on 2012-07-17. Retrieved 2012-07-22. {{cite web}}: Unknown parameter |deadurl= ignored (|url-status= suggested) (help)
^ Staff (2004). "Caroní River Watershed Management Plan" (PDF). Inter-America Development Bank. Archived from the original (PDF) on October 28, 2008. Retrieved 2008-10-25. {{cite web}}: Unknown parameter |deadurl= ignored (|url-status= suggested) (help)
^ CJWSJY.com.cn Archived June 29, 2010, at the Wayback Machine

External links

International Hydropower Association
Hydroelectric power at Curlie
National Hydropower Association, USA
Hydropower Reform Coalition
Interactive demonstration on the effects of dams on rivers
European Small Hydropower Association
IEC TC 4: Hydraulic turbines (International Electrotechnical Commission - Technical Committee 4) IEC TC 4 portal with access to scope, documents and TC 4 website

[ren21.net-1] ttp://www.ren21.net/wp-content/uploads/2016/06/GSR_2016_Full_Report_REN21.pdf

[wi2012-2] Worldwatch Institute (January 2012). "Use and Capacity of Global Hydropower Increases".

[REN21-2011-3] Renewables 2011 Global Status Report, page 25, Hydropower, REN21, published 2011, accessed 2016-02-19.

[4] One of the Oldest Hydroelectric Power Plants in Europa Built on Tesla’s Principels, Explorations in the History of Machines and Mechanisms: Proceedings of HMM2012, Teun Koetsier and Marco Ceccarelli, 2012.

[doehis-5] "History of Hydropower". U.S. Department of Energy.

[watenc-6] "Hydroelectric Power". Water Encyclopedia.

[7] Association for Industrial Archaeology (1987). Industrial archaeology review, Volumes 10-11. Oxford University Press. p. 187.

[8] "Hydroelectric power - energy from falling water". Clara.net.

[act-9] "Boulder Canyon Project Act" (PDF). December 21, 1928. Archived from the original (PDF) on June 13, 2011. {{cite web}}: Unknown parameter |deadurl= ignored (|url-status= suggested) (help)

[Arnold-10] The Evolution of the Flood Control Act of 1936, Joseph L. Arnold, United States Army Corps of Engineers, 1988 Archived 2007-08-23 at the Wayback Machine

[11] The Book of Knowledge. Vol. Vol. 9 (1945 ed.). p. 3220. {{cite encyclopedia}}: |volume= has extra text (help); Missing or empty |title= (help)

[12] "Hoover Dam and Lake Mead". U.S. Bureau of Reclamation.

[13] ttp://www.iea.org/publications/freepublications/publication/hydropower_essentials.pdf

[14] "hydro electricity - explained".

[15] Pumped Storage, Explained Archived 2012-12-31 at the Wayback Machine

[16] "Run-of-the-River Hydropower Goes With the Flow".

[17] "Energy Resources: Tidal power".

[18] Pope, Gregory T. (December 1995), "The seven wonders of the modern world", Popular Mechanics, pp. 48–56

[19] Renewables Global Status Report 2006 Update Archived July 18, 2011, at the Wayback Machine, REN21, published 2006

[20] "Micro Hydro in the fight against poverty". Tve.org. Archived from the original on 2012-04-26. Retrieved 2012-07-22. {{cite web}}: Unknown parameter |deadurl= ignored (|url-status= suggested) (help)

[21] "Pico Hydro Power". T4cd.org. Archived from the original on 2009-07-31. Retrieved 2010-07-16. {{cite web}}: Unknown parameter |deadurl= ignored (|url-status= suggested) (help)

[Huggins2010-22] Robert A. Huggins (1 September 2010). Energy Storage. Springer. p. 60. ISBN 978-1-4419-1023-3.

[SusskindRaseman1970-23] Herbert Susskind; Chad J. Raseman (1970). Combined Hydroelectric Pumped Storage and Nuclear Power Generation. Brookhaven National Laboratory. p. 15.

[Sørensen2004-24] Bent Sørensen (2004). Renewable Energy: Its Physics, Engineering, Use, Environmental Impacts, Economy, and Planning Aspects. Academic Press. pp. 556–. ISBN 978-0-12-656153-1.

[(U.S.)1980-25] Geological Survey (U.S.) (1980). Geological Survey Professional Paper. U.S. Government Printing Office. p. 10.

[26] Hydropower – A Way of Becoming Independent of Fossil Energy? Archived 28 May 2008 at the Wayback Machine

[27] "Beyond Three Gorges in China". Waterpowermagazine.com. 2007-01-10. Archived from the original on 2011-06-14. {{cite web}}: Unknown parameter |deadurl= ignored (|url-status= suggested) (help)

[28] (http://papers.ssrn.com/sol3/papers.cfm?abstract_id=2406852), Should We Build More Large Dams? The Actual Costs of Hydropower Megaproject Development, Energy Policy, March 2014, pp. 1-14

[29] Lifecycle greenhouse gas emissions pg19

[30] ttp://www.iea.org/topics/renewables/subtopics/hydropower/

[ExternEFTR-31] Rabl A.; et al. (August 2005). "Final Technical Report, Version 2" (PDF). Externalities of Energy: Extension of Accounting Framework and Policy Applications. European Commission. Archived from the original (PDF) on March 7, 2012. {{cite web}}: Explicit use of et al. in: |author= (help); Unknown parameter |deadurl= ignored (|url-status= suggested) (help)

[ExternEGraphs-32] "External costs of electricity systems (graph format)". ExternE-Pol. Technology Assessment / GaBE (Paul Scherrer Institut). 2005. Archived from the original on 1 November 2013. {{cite web}}: Cite has empty unknown parameter: |dead-url= (help)

[33] Wehrli, Bernhard (1 September 2011). "Climate science: Renewable but not carbon-free". Nature Geoscience. 4 (9): 585–586. doi:10.1038/ngeo1226 – via www.nature.com.

[Water:_Science_and_Issues-34] Atkins, William (2003). "Hydroelectric Power". Water: Science and Issues. 2: 187–191.

[:0-35] Robbins, Paul (2007). "Hydropower". Encyclopedia of Environment and Society. 3.

[36] "Sedimentation Problems with Dams". Internationalrivers.org. Retrieved 2010-07-16.

[37] John Macknick and others, A Review of Operational Water Consumption and Withdrawal Factors for Electricity Generating Technologies, National Renewable Energy Laboratory, Technical Report NREL/TP-6A20-50900.

[38] Patrick James, H Chansen (1998). "Teaching Case Studies in Reservoir Siltation and Catchment Erosion" (PDF). Great Britain: TEMPUS Publications. pp. 265–275. Archived from the original (PDF) on 2009-09-02. {{cite web}}: Unknown parameter |deadurl= ignored (|url-status= suggested) (help)

[39] Șentürk, Fuat (1994). Hydraulics of dams and reservoirs (reference. ed.). Highlands Ranch, Colo.: Water Resources Publications. p. 375. ISBN 0-918334-80-2.

[ODI1-40] Frauke Urban and Tom Mitchell 2011. Climate change, disasters and electricity generation Archived September 20, 2012, at the Wayback Machine. London: Overseas Development Institute and Institute of Development Studies

[41] "WCD Findal Report". Dams.org. 2000-11-16. Archived from the original on 2013-08-21. {{cite web}}: Unknown parameter |deadurl= ignored (|url-status= suggested) (help)

[42] "Hydroelectric power's dirty secret revealed". Newscientist.com.

[43] ""Rediscovered" Wood & The Triton Sawfish". Inhabitat. 2006-11-16.

[44] "Briefing of World Commission on Dams". Internationalrivers.org. 2008-02-29.

[:1-45] References may be found in the list of Dam failures.

[46] ttp://ecolo.org/documents/documents_in_french/malpasset/malpasset.htm retrieved 02sep2015

[:2-47] Toccoa Flood USGS Historical Site, retrieved 02sep2009

[48] Lawson, Michael L. (1982). Dammed Indians: the Pick-Sloan Plan and the Missouri River Sioux, 1944–1980. Norman: University of Oklahoma Press.

[49] ttps://www.sintef.no/en/latest-news/norway-is-europes-cheapest-battery/

[norway-50] "Binge and purge". The Economist. 2009-01-22. Retrieved 2009-01-30. 98-99% of Norway's electricity comes from hydroelectric plants. {{cite news}}: Cite has empty unknown parameter: |coauthors= (help)

[51] Consumption BP.com^{[dead link]}

[IEA2015-52] "2015 Key World Energy Statistics" (PDF). report. International Energy Agency (IEA). Retrieved 1 June 2016.

[53] "Indicators 2009, National Electric Power Industry". Chinese Government. Retrieved 18 July 2010.

[54] "Belo Monte hydroelectric dam construction work begins". Guardian UK. 10 March 2011. Retrieved 2 April 2011.

[55] "Belo Monte dam construction halted by Brazilian court". Guardian UK. 16 August 2012. Retrieved 24 August 2012.

[56] "Upper Siang project likely to be relocated on Chinese concerns". Thehindubusinessline.com. 2006-03-24. Retrieved 2012-07-22.

[57] "Brazil Sends Forces to Jirau Dam After Riots". Wall Street Journal. 18 March 2011. Retrieved 2 April 2011.

[58] "二滩水电开发有限责任公司". Ehdc.com.cn. 2009-04-25. Archived from the original on 2012-10-18. Retrieved 2012-07-22. {{cite web}}: Unknown parameter |deadurl= ignored (|url-status= suggested) (help)

[59] "Archived copy". Archived from the original on 2011-07-07. Retrieved 2008-12-12. {{cite web}}: Unknown parameter |deadurl= ignored (|url-status= suggested) (help)CS1 maint: archived copy as title (link)

[60] "陆良县人口和计划生育局". Zt.xxgk.yn.gov.cn. Archived from the original on 2012-07-17. Retrieved 2012-07-22. {{cite web}}: Unknown parameter |deadurl= ignored (|url-status= suggested) (help)

[61] Staff (2004). "Caroní River Watershed Management Plan" (PDF). Inter-America Development Bank. Archived from the original (PDF) on October 28, 2008. Retrieved 2008-10-25. {{cite web}}: Unknown parameter |deadurl= ignored (|url-status= suggested) (help)

[62] CJWSJY.com.cn Archived June 29, 2010, at the Wayback Machine

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Hydropower
Hydroelectricity generation	Dam List of conventional hydroelectric power stations Pumped-storage hydroelectricity Small hydro Micro hydro Pico hydro Run-of-the-river hydroelectricity
Hydroelectricity equipment	Francis turbine Kaplan turbine Tyson turbine Gorlov helical turbine Pelton wheel Turgo turbine Cross-flow turbine Water wheel

@@ Line 1: / Line 1: @@
+{{pp-semi-protected|small=yes}}
-#REDIRECT [[Hydroelectricity]]
+[[File:ThreeGorgesDam-China2009.jpg|upright=1.35|thumb|The [[Three Gorges Dam]] in Central China is the [[List of largest power stations in the world#Top 20 largest power producing facilities|world's largest]] power producing facility of any kind.]]
+{{Sustainable energy}}
+'''Hydroelectricity''' is [[Electricity generation|electricity produced]] from [[hydropower]]. In 2015 hydropower generated 16.6% of the world's total electricity and 70% of all [[renewable energy|renewable electricity]],<ref name="ren21.net">http://www.ren21.net/wp-content/uploads/2016/06/GSR_2016_Full_Report_REN21.pdf</ref> and was expected to increase about 3.1% each year for the next 25 years.
+Hydropower is produced in 150 countries, with the [[Asia-Pacific]] region generating 33 percent of global hydropower in 2013. [[China]] is the largest hydroelectricity producer, with 920 TWh of production in 2013, representing 16.9 percent of domestic electricity use.
+The cost of hydroelectricity is relatively low, making it a competitive source of renewable electricity. The hydro station consumes no water, unlike coal or gas plants. The average cost of electricity from a hydro station larger than 10 [[megawatt]]s is 3 to 5 U.S. cents per [[kilowatt-hour]].<ref name=wi2012/> With a dam and reservoir it is also a flexible source of electricity since the amount produced by the station can be changed up or down very quickly to adapt to changing energy demands. Once a hydroelectric complex is constructed, the project produces no direct waste, and in many cases, has a considerably lower output level of [[greenhouse gas]]es than [[fossil fuel]] powered energy plants.<ref name="REN21-2011">[http://www.ren21.net/Portals/0/documents/Resources/GSR2011_FINAL.pdf Renewables 2011 Global Status Report, page 25, Hydropower], ''[[REN21]]'', published 2011, accessed 2016-02-19.</ref>
+==History==
+{{See also|Hydropower#History}}
+[[File:Hidroelektrana na Đetinji 01.jpg|thumb|upright=1.15|Museum Hydroelectric power plant ″Under the Town″ in [[Serbia]], built in 1900.<ref>[https://books.google.com/books?id=-x9NHOLSnNUC&pg=PA397&lpg=PA397&dq=One+of+the+oldest+hydroelectric+power+plants+built+on+tesla+principles&source=bl&ots=gUv_MLF960&sig=JJY5otdOeGypfDKBcWMegoJtjyo&hl=sr&sa=X&ei=sLHoU_bfB-fk4QTb8oDoBw&ved=0CDgQ6AEwAw#v=onepage&q=One%20of%20the%20oldest%20hydroelectric%20power%20plants%20built%20on%20tesla%20principles&f=false ''One of the Oldest Hydroelectric Power Plants in Europa Built on Tesla’s Principels''], Explorations in the History of Machines and Mechanisms: Proceedings of HMM2012, Teun Koetsier and Marco Ceccarelli, 2012.</ref>]]
+Hydropower has been used since ancient times to grind flour and perform other tasks. In the mid-1770s, French engineer [[Bernard Forest de Bélidor]] published ''Architecture Hydraulique'' which described vertical- and horizontal-axis hydraulic machines. By the late 19th century, the [[electrical generator]] was developed and could now be coupled with hydraulics.<ref name="doehis">{{cite web|url=https://www.energy.gov/eere/water/history-hydropower|title=History of Hydropower|publisher=U.S. Department of Energy}}</ref> The growing demand for the [[Industrial Revolution]] would drive development as well.<ref name="watenc">{{cite web
+  |title=Hydroelectric Power|url=http://www.waterencyclopedia.com/Ge-Hy/Hydroelectric-Power.html|publisher=Water Encyclopedia
+}}</ref> In 1878 the world's first hydroelectric power scheme was developed at [[Cragside]] in [[Northumberland]], England by [[William Armstrong, 1st Baron Armstrong|William Armstrong]]. It was used to power a single [[arc lamp]] in his art gallery.<ref >{{cite book
+  |title=Industrial archaeology review, Volumes 10-11|year=1987|publisher=Oxford University Press|page=187
+  |url=https://books.google.com/books?id=4xg9AQAAIAAJ&dq=Industrial%20archaeology%20review%3A%20Volumes%2010-11&source=gbs_book_other_versions|author=Association for Industrial Archaeology
+}}</ref>  The old [[Robert Moses Niagara Hydroelectric Power Station#Origins|Schoelkopf Power Station No. 1]] near [[Niagara Falls]] in the U.S. side began to produce electricity in 1881. The first [[Thomas Alva Edison|Edison]] hydroelectric power station, the [[Vulcan Street Plant]], began operating September 30, 1882, in [[Appleton, Wisconsin]], with an output of about 12.5 kilowatts.<ref>{{cite web|url=http://home.clara.net/darvill/altenerg/hydro.htm|title= Hydroelectric power - energy from falling water|publisher=Clara.net}}</ref> By 1886 there were 45 hydroelectric power stations in the U.S. and Canada. By 1889 there were 200 in the U.S. alone.<ref name="doehis"/>
+[[File:Warwick Castle - Engine House, Waterwheel, Weir, and Old Castle Bridge.jpg|thumb|upright=1.15|The [[Warwick Castle]] water-powered generator house, used for the generation of electricity for the castle from 1894 until 1940]]
+At the beginning of the 20th century, many small hydroelectric power stations were being constructed by commercial companies in mountains near metropolitan areas. [[Grenoble]], France held the [[International Exhibition of Hydropower and Tourism]] with over one million visitors. By 1920 as 40% of the power produced in the United States was hydroelectric, the [[Federal Power Act]] was enacted into law. The Act created the [[Federal Power Commission]] to regulate hydroelectric power stations on federal land and water. As the power stations became larger, their associated dams developed additional purposes to include [[flood control]], [[irrigation]] and [[navigable|navigation]]. Federal funding became necessary for large-scale development and federally owned corporations, such as the [[Tennessee Valley Authority]] (1933) and the [[Bonneville Power Administration]] (1937) were created.<ref name="watenc"/> Additionally, the [[Bureau of Reclamation]] which had begun a series of western U.S. irrigation projects in the early 20th century was now constructing large hydroelectric projects such as the 1928 [[Boulder Canyon Project Act|Hoover Dam]].<ref name="act">{{cite web|title=Boulder Canyon Project Act|url=http://www.usbr.gov/lc/region/g1000/pdfiles/bcpact.pdf|date=December 21, 1928|deadurl=yes|archiveurl=https://web.archive.org/web/20110613142851/http://www.usbr.gov/lc/region/g1000/pdfiles/bcpact.pdf|archivedate=June 13, 2011|df=}}</ref> The [[U.S. Army Corps of Engineers]] was also involved in hydroelectric development, completing the [[Bonneville Dam]] in 1937 and being recognized by the [[Flood Control Act of 1936]] as the premier federal flood control agency.<ref name=Arnold>[http://www.usace.army.mil/publications/eng-pamphlets/ep870-1-29/entire.pdf The Evolution of the Flood Control Act of 1936, Joseph L. Arnold, [[United States Army Corps of Engineers]], 1988] {{webarchive|url=https://web.archive.org/web/20070823024822/http://www.usace.army.mil/publications/eng-pamphlets/ep870-1-29/entire.pdf |date=2007-08-23 }}</ref>
+Hydroelectric power stations continued to become larger throughout the 20th century. Hydropower was referred to as ''white coal'' for its power and plenty.<ref>{{cite encyclopedia|encyclopedia=The Book of Knowledge|volume=Vol. 9|page=3220|edition=1945}}</ref> [[Hoover Dam]]'s initial 1,345 MW power station was the world's largest hydroelectric power station in 1936; it was eclipsed by the 6809 MW [[Grand Coulee Dam]] in 1942.<ref>{{cite web|url=http://www.a2zlasvegas.com/otherside/sights/hoover.html|title=Hoover Dam and Lake Mead|publisher=U.S. Bureau of Reclamation}}</ref> The [[Itaipu Dam]] opened in 1984 in South America as the largest, producing 14,000 MW but was surpassed in 2008 by the [[Three Gorges Dam]] in China at 22,500 MW. Hydroelectricity would eventually supply some countries, including [[Norway]], [[Democratic Republic of the Congo]], [[Paraguay]] and [[Brazil]], with over 85% of their electricity. The United States currently has over 2,000 hydroelectric power stations that supply 6.4% of its total electrical production output, which is 49% of its renewable electricity.<ref name="watenc"/>
+==Future potential==
+The technical potential for the growth of hydropower around the world are, 71% Europe, 75% North America, 79% South America, 95% Africa, 95% Middle East, 82% Asia Pacific.
+The political realities of new reservoirs in western countries, economic limitations in the third world and the lack of a transmission system in undeveloped areas, result in the possibility of developing 25% of the remaining potential before 2050, with the bulk of that being in the Asia Pacific area.<ref>http://www.iea.org/publications/freepublications/publication/hydropower_essentials.pdf</ref> A few countries are highly developed and have very little room for growth, Switzerland 12% and Mexico 20%.
+==Generating methods==
+[[File:Sala de turbinas.jpg|thumb|upright=1.35|Turbine row at El Nihuil II Power Station in [[Mendoza, Argentina|Mendoza]], Argentina]]
+[[File:Dam generator impeller.jpg|thumb|upright=0.9|right|An old [[Impeller|impeller]] on display at the [[Glen Canyon Dam]]]]
+[[File:Hydroelectric dam.svg|thumb|upright=1.35|Cross section of a conventional hydroelectric dam.]]
+[[File:Water turbine - edit1.svg|thumb|A typical [[Water turbine|turbine]] and [[electrical generator|generator]]]]
+===Conventional (dams)===
+{{See also|List of conventional hydroelectric power stations}}
+Most hydroelectric power comes from the [[potential energy]] of [[dam]]med water driving a [[water turbine]] and [[electric generator|generator]]. The power 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 (hydraulic)|head]]. A large pipe (the "[[penstock]]") delivers water from the [[reservoir]] to the turbine.<ref>{{cite web|url=http://www.electricityforum.com/hydroelectricity.html|title=hydro electricity - explained|publisher=}}</ref>
+===Pumped-storage===
+{{Main article|Pumped-storage hydroelectricity}}
+{{See also|List of pumped-storage hydroelectric power stations}}
+This method produces electricity to supply high peak demands by moving water between [[reservoir]]s at different elevations. At times of low electrical demand, the excess generation capacity is used to pump water into the higher reservoir. When the demand becomes greater, water is released back into the lower reservoir through a turbine. Pumped-storage schemes currently provide the most commercially important means of large-scale [[grid energy storage]] and improve the daily [[capacity factor]] of the generation system. Pumped storage is not an energy source, and appears as a negative number in listings.<ref>[http://thesouthslope.com/content/pumped-storage-explained Pumped Storage, Explained] {{webarchive|url=https://web.archive.org/web/20121231233454/http://thesouthslope.com/content/pumped-storage-explained |date=2012-12-31 }}</ref>
+===Run-of-the-river===
+{{Main article|Run-of-the-river hydroelectricity}}
+{{See also|List of run-of-the-river hydroelectric power stations}}
+Run-of-the-river hydroelectric stations are those with small or no reservoir capacity, so that only the water coming from upstream is available for generation at that moment, and any oversupply must pass unused. A constant supply of water from a lake or existing reservoir upstream is a significant advantage in choosing sites for run-of-the-river. In the United States, run of the river hydropower could potentially provide {{convert|60000|MW}} (about 13.7% of total use in 2011 if continuously available).<!--total use in 2011 was 3841 billion kWh from Annual Energy Outlook http://www.eia.gov/forecasts/aeo/er/ --><ref>{{cite web|url=http://www.renewableenergyworld.com/rea/news/article/2012/01/run-of-the-river-hydropower-goes-with-the-flow|title=Run-of-the-River Hydropower Goes With the Flow|publisher=}}</ref>
+===Tide===
+{{Main article|Tide power}}
+{{See also|List of tidal power stations}}
+A [[tidal power]] station makes use of the daily rise and fall of ocean water due to tides; such sources are highly predictable, and if conditions permit construction of reservoirs, can also be [[Dispatchable generation|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 [[water wheel]]s. Tidal power is viable in a relatively small number of locations around the world. In Great Britain, there are eight sites that could be developed, which
+have the potential to generate 20% of the electricity used in 2012.<ref>{{cite web|url=http://www.darvill.clara.net/altenerg/tidal.htm|title=Energy Resources: Tidal power|publisher=}}</ref>
+==Sizes, types and capacities of hydroelectric facilities==
+=== Large facilities ===
+{{See also|List of largest power stations in the world|List of largest hydroelectric power stations}}
+Large-scale hydroelectric power stations are more commonly seen as the largest power producing facilities in the world, with some hydroelectric facilities capable of generating more than double the installed capacities of the current [[List of nuclear power stations|largest nuclear power stations]].
+Although no official definition exists for the capacity range of large hydroelectric power stations, facilities from over a few hundred [[megawatt]]s are generally considered large hydroelectric facilities.
+Currently, only four facilities over {{nowrap|10 [[Gigawatt|GW]]}} ({{nowrap|10,000 [[Megawatt|MW]]}}) are in operation worldwide, see table below.<ref name=wi2012>{{cite web |url=http://www.worldwatch.org/node/9527 |title=Use and Capacity of Global Hydropower Increases |author=Worldwatch Institute |date=January 2012 |work= }}</ref>
+{|class="wikitable"
+|-
+! Rank !! width=150 | Station !! width=150 | Country !! [[Geographic coordinate system|Location]] !! Capacity ([[Megawatt|MW]])
+|-
+| align=center | 1. || [[Three Gorges Dam]] || {{flag|China}} || {{Coord|30|49|15|N|111|00|08|E|name=Three Gorges Dam}} || align=center | 22,500
+|-
+| align=center | 2. || [[Itaipu Dam]] || {{flag|Brazil}}<br />{{flag|Paraguay}} || {{Coord|25|24|31|S|54|35|21|W|name=Itaipu Dam}} || align=center | 14,000
+|-
+| align=center | 3. ||[[Xiluodu Dam]] || {{flag|China}} || {{Coord|28|15|35|N|103|38|58|E|name=Xiluodu Dam}} || align=center | 13,860
+|-
+| align=center | 4. || [[Guri Dam]] || {{flag|Venezuela}} || {{Coord|07|45|59|N|62|59|57|W|name=Guri Dam}} || align=center | 10,200
+|}
+{{wide image|Itaipu Décembre 2007 - Vue Générale.jpg|1500px|Panoramic view of the [[Itaipu Dam]], with the spillways (closed at the time of the photo) on the left. In 1994, the [[American Society of Civil Engineers]] elected the Itaipu Dam as one of the seven modern [[Wonders of the World]].<ref>{{Citation| last = Pope| first = Gregory T.| title = The seven wonders of the modern world| newspaper = Popular Mechanics| pages = 48–56| date = December 1995| url = https://books.google.com/books?id=O2YEAAAAMBAJ&lpg=PA50&dq=itaipu&as_brr=1&pg=PA50#v=onepage&q&f=false}}</ref>
+}}
+===Small===
+{{Main article|Small hydro}}
+Small hydro is the development of [[hydroelectric power]] on a scale serving a small community or industrial plant. The definition of a small hydro project varies but a generating capacity of up to 10 [[megawatt]]s (MW) is generally accepted as the upper limit of what can be termed small hydro. This may be stretched to 25 MW and 30 MW in [[Canada]] and the [[United States]]. Small-scale hydroelectricity production grew by 28% during 2008 from 2005, raising the total world small-hydro capacity to {{nowrap|85 [[Gigawatt|GW]]}}. Over 70% of this was in [[China]] ({{nowrap|65 GW}}), followed by [[Japan]] ({{nowrap|3.5 GW}}), the United States ({{nowrap|3 GW}}), and [[India]] ({{nowrap|2 GW}}).<ref>[http://www.ren21.net/globalstatusreport/download/RE_GSR_2006_Update.pdf Renewables Global Status Report 2006 Update] {{webarchive |url=https://web.archive.org/web/20110718181410/http://www.ren21.net/globalstatusreport/download/RE_GSR_2006_Update.pdf |date=July 18, 2011 }}, ''[[REN21]]'', published 2006</ref>
+[[File:Nw vietnam hydro.jpg|thumb|upright=1.35|A micro-hydro facility in [[Vietnam]]]]
+[[File:Amateur Hydroelectricity.jpg|thumb|upright=1.35|Pico hydroelectricity in [[Mondulkiri]], [[Cambodia]]]]
+Small hydro stations may be connected to conventional electrical distribution networks as a source of low-cost renewable energy. Alternatively, small hydro projects may be built in isolated areas that would be uneconomic to serve from a network, or in areas where there is no national electrical distribution network. Since small hydro projects usually have minimal reservoirs and civil construction work, they are seen as having a relatively low environmental impact compared to large hydro. This decreased environmental impact depends strongly on the balance between stream flow and power production.
+===Micro===
+{{Main article|Micro hydro}}
+Micro hydro is a term used for [[hydroelectric power]] installations that typically produce up to {{nowrap|100 [[Kilowatt|kW]]}} of power. These installations can provide power to an isolated home or small community, or are sometimes connected to electric power networks. There are many of these installations around the world, particularly in developing nations as they can provide an economical source of energy without purchase of fuel.<ref>{{cite web|url=http://www.tve.org/ho/doc.cfm?aid=1636&lang=English |title=Micro Hydro in the fight against poverty |publisher=Tve.org |date= |accessdate=2012-07-22 |deadurl=yes |archiveurl=https://web.archive.org/web/20120426092643/http://tve.org/ho/doc.cfm?aid=1636&lang=English |archivedate=2012-04-26 |df= }}</ref> Micro hydro systems complement [[photovoltaics|photovoltaic]] solar energy systems because in many areas, water flow, and thus available hydro power, is highest in the winter when solar energy is at a minimum.
+===Pico===
+{{Main article|Pico hydro}}
+Pico hydro is a term used for [[hydroelectric power]] generation of under {{nowrap|5 [[Kilowatt|kW]]}}. It is useful in small, remote communities that require only a small amount of electricity. For example, to power one or two fluorescent light bulbs and a TV or radio for a few homes.<ref>{{cite web|url=http://www.t4cd.org/Resources/ICT_Resources/Projects/Pages/ICTProject_287.aspx|title=Pico Hydro Power|publisher=T4cd.org|accessdate=2010-07-16|deadurl=yes|archiveurl=https://web.archive.org/web/20090731064419/http://www.t4cd.org/Resources/ICT_Resources/Projects/Pages/ICTProject_287.aspx|archivedate=2009-07-31|df=}}</ref> Even smaller turbines of 200-300W may power a single home in a developing country with a drop of only {{Convert|1|m|ft|0|abbr=on}}. A Pico-hydro setup is typically [[#Run-of-the-river|run-of-the-river]], meaning that dams are not used, but rather pipes divert some of the flow, drop this down a gradient, and through the turbine before returning it to the stream.
+===Underground===
+{{Main article|Underground power station}}
+An [[underground power station]] is generally used at large facilities and makes use of a large natural height difference between two waterways, such as a waterfall or mountain lake. An underground tunnel is constructed to take water from the high reservoir to the generating hall built in an underground cavern near the lowest point of the water tunnel and a horizontal tailrace taking water away to the lower outlet waterway.[[File:Tailrace-Forebay-Limestone.JPG|thumb|Measurement of the tailrace and forebay rates at the [[Limestone Generating Station]] in [[Manitoba]], [[Canada]].]]
+===Calculating available power===
+{{Main article|Hydropower}}
+A simple formula for approximating electric power production at a hydroelectric station is: <math> P = \rho hrgk </math>, where
+*<math>P</math> is Power in watts,
+*<math>\rho</math> is the density of water (~1000&nbsp;kg/m<sup>3</sup>),
+*<math>h</math> is height in meters,
+*<math>r</math> is flow rate in cubic meters per second,
+*<math>g</math> is acceleration due to [[gravity]] of 9.8&nbsp;m/s<sup>2</sup>,
+*<math>k</math> is a coefficient of efficiency ranging from 0 to 1. Efficiency is often higher (that is, closer to 1) 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.
+==Properties==
+===Advantages===
+[[File:Stwlan.dam.jpg|thumb|The [[Ffestiniog Power Station]] can generate {{nowrap|360 [[Megawatt|MW]]}} of electricity within 60 seconds of the demand arising.]]
+====Flexibility====
+Hydropower is a flexible source of electricity since stations can be ramped up and down very quickly to adapt to changing energy demands.<ref name=wi2012/> Hydro turbines have a start-up time of the order of a few minutes.<ref name="Huggins2010">{{cite book|author=Robert A. Huggins|title=Energy Storage|url=https://books.google.com/books?id=Nn5y9gQeIlwC&pg=PA60|date=1 September 2010|publisher=Springer|isbn=978-1-4419-1023-3|pages=60}}</ref> It takes around 60 to 90 seconds to bring a unit from cold start-up to full load; this is much shorter than for gas turbines or steam plants.<ref name="SusskindRaseman1970">{{cite book|author1=Herbert Susskind|author2=Chad J. Raseman|title=Combined Hydroelectric Pumped Storage and Nuclear Power Generation|url=https://books.google.com/books?id=zbu5m1Een2sC|year=1970|publisher=Brookhaven National Laboratory|page=15}}</ref> Power generation can also be decreased quickly when there is a surplus power generation.<ref name="Sørensen2004">{{cite book|author=Bent Sørensen|title=Renewable Energy: Its Physics, Engineering, Use, Environmental Impacts, Economy, and Planning Aspects|url=https://books.google.com/books?id=Y17FoN2VUEwC&pg=PA556|year=2004|publisher=Academic Press|isbn=978-0-12-656153-1|pages=556–}}</ref> Hence the limited capacity of hydropower units is not generally used to produce base power except for vacating the flood pool or meeting downstream needs.<ref name="(U.S.)1980">{{cite book|author=Geological Survey (U.S.)|title=Geological Survey Professional Paper|url=https://books.google.com/books?id=37dUAAAAYAAJ&pg=PA10|year=1980|publisher=U.S. Government Printing Office|pages=10}}</ref> Instead, it serves as backup for non-hydro generators.<ref name="Sørensen2004" />
+====Low cost/high value power====
+The major advantage of conventional hydroelectric dams with reservoirs is their ability to store water at low cost for [[Dispatchable generation|dispatch later]] as high value clean electricity. The average cost of electricity from a hydro station larger than 10 megawatts is 3 to 5 U.S. cents per kilowatt-hour.<ref name=wi2012/> When used as peak power to meet demand, hydroelectricity has a higher value than base power and a much higher value compared to [[intermittent energy source]]s.
+Hydroelectric stations have long economic lives, with some plants still in service after 50–100 years.<ref>[http://reme.epfl.ch/webdav/site/reme/users/106542/public/SHS4/Gr01.pdf Hydropower – A Way of Becoming Independent of Fossil Energy?]  {{webarchive |url=https://web.archive.org/web/20080528070938/http://reme.epfl.ch/webdav/site/reme/users/106542/public/SHS4/Gr01.pdf |date=28 May 2008 }}</ref> 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 station 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.<ref>{{cite web|url=http://www.waterpowermagazine.com/story.asp?storyCode=2041318 |title=Beyond Three Gorges in China |publisher=Waterpowermagazine.com |date=2007-01-10 |deadurl=yes |archiveurl=https://web.archive.org/web/20110614050746/http://www.waterpowermagazine.com/story.asp?storyCode=2041318 |archivedate=2011-06-14 |df= }}</ref> Additionally, some data shows that in most countries large hydropower dams will be too costly and take too long to build to deliver a positive risk adjusted return, unless appropriate risk management measures are put in place.<ref>(http://papers.ssrn.com/sol3/papers.cfm?abstract_id=2406852), Should We Build More Large Dams? The Actual Costs of Hydropower Megaproject Development, Energy Policy, March 2014, pp. 1-14</ref>
+====Suitability for industrial applications====
+While many hydroelectric projects supply public electricity networks, some are created to serve specific [[industry|industrial]] enterprises. Dedicated hydroelectric projects are often built to provide the substantial amounts of electricity needed for [[aluminium]] electrolytic plants, for example. The [[Grand Coulee Dam]] switched to support [[Alcoa]] aluminium in [[Bellingham, Washington]], [[United States]] for American [[World War II]] airplanes before it was allowed to provide irrigation and power to citizens (in addition to aluminium 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 [[Comalco|Tiwai Point]].
+====Reduced CO<sub>2</sub> emissions====
+Since hydroelectric dams do not use fuel, power generation does not produce [[carbon dioxide]].  While carbon dioxide is initially produced during construction of the project, and some methane is given off annually by reservoirs, hydro in specific nordic cases, has the lowest [[Greenhouse gas#Life-cycle greenhouse-gas emissions of energy sources|lifecycle greenhouse gas emissions]] for power generation.<ref>Lifecycle greenhouse gas emissions pg19</ref> Compared to fossil fuels generating an equivalent amount of electricity, hydro displaced three billion tonnes of CO2 emissions in 2011.<ref>http://www.iea.org/topics/renewables/subtopics/hydropower/</ref> One measurement of greenhouse gas related and other externality comparison between energy sources can be found in the ExternE project by the [[Paul Scherrer Institute]] and the [[University of Stuttgart]] which was funded by the [[European Commission]].<ref name="ExternEFTR">{{cite web|url=http://www.externe.info/expoltec.pdf |title=Final Technical Report, Version 2 |author=Rabl A. et. al. |date=August 2005 |work=Externalities of Energy: Extension of Accounting Framework and Policy Applications |publisher=European Commission |deadurl=yes |archiveurl=https://web.archive.org/web/20120307120342/http://www.externe.info/expoltec.pdf |archivedate=March 7, 2012 }}</ref> According to that study, hydroelectricity in Europe produces the least amount of [[greenhouse gases]] and [[externality]] of any energy source.<ref name="ExternEGraphs">{{cite web|url=http://gabe.web.psi.ch/projects/externe_pol/index.html|title=External costs of electricity systems (graph format)|year=2005|publisher=Technology Assessment / GaBE ([[Paul Scherrer Institut]])|archive-url=https://web.archive.org/web/20131101201452/http://gabe.web.psi.ch/projects/externe_pol/index.html|archive-date=1 November 2013|dead-url=|work=ExternE-Pol}}</ref> Coming in second place was [[wind energy|wind]], third was [[Nuclear power|nuclear energy]], and fourth was [[solar energy|solar]] [[photovoltaic]].<ref name="ExternEGraphs"/> The low [[greenhouse gas]] impact of hydroelectricity is found especially in [[temperate climate]]s. The above study was for local energy in [[Europe]]; presumably similar conditions prevail in North America and Northern Asia, which all see a regular, natural freeze/thaw cycle (with associated seasonal plant decay and regrowth). Greater greenhouse gas emission impacts are found in the tropical regions because the reservoirs of power stations in tropical regions produce a larger amount of [[methane]] than those in temperate areas.<ref>{{cite journal|url=http://www.nature.com/ngeo/journal/v4/n9/full/ngeo1226.html|title=Climate science: Renewable but not carbon-free|first=Bernhard|last=Wehrli|date=1 September 2011|publisher=|journal=Nature Geoscience|volume=4|issue=9|pages=585–586|via=www.nature.com|doi=10.1038/ngeo1226}}</ref>
+====Other uses of the reservoir====
+Reservoirs created by hydroelectric schemes often provide facilities for [[List of water sports|water sports]], and become tourist attractions themselves. In some countries, [[aquaculture]] in reservoirs is common. [[Multipurpose reservoir|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.<ref name="Water: Science and Issues">{{cite journal|last=Atkins|first=William|title=Hydroelectric Power|journal=Water: Science and Issues|year=2003|volume=2|pages=187–191}}</ref>
+===Disadvantages===
+{{see also|Renewable energy debate#Disadvantages of hydroelectricity}}
+====Ecosystem damage and loss of land====
+[[File:MeroweDam01.jpg|thumb|[[Merowe Dam]] in [[Sudan]]. Hydroelectric power stations that use [[dam]]s submerge large areas of land due to the requirement of a [[reservoir]]. These changes to land color or [[albedo]], alongside certain projects that concurrently submerge rainforests, can in these specific cases, result in the global warming impact, or equivalent [[Life-cycle greenhouse-gas emissions of energy sources|life-cycle greenhouse gases]] of hydroelectricity projects, to exceed that of coal power stations.]]
+Large reservoirs associated with traditional hydroelectric power stations result in submersion of extensive areas upstream of the dams, sometimes destroying biologically rich and productive lowland and riverine valley forests, marshland and grasslands. Damming interrupts the flow of rivers and can harm local ecosystems, and building large dams and reservoirs often involves displacing people and wildlife.<ref name=wi2012/> The loss of land is often exacerbated by [[habitat fragmentation]] of surrounding areas caused by the reservoir.<ref name=":0">{{cite journal|last=Robbins|first=Paul|title=Hydropower|journal=Encyclopedia of Environment and Society|year=2007|volume=3}}</ref>
+Hydroelectric projects can be disruptive to surrounding aquatic [[ecosystem]]s both upstream and downstream of the plant site. 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.<ref>{{cite web|url=http://internationalrivers.org/en/node/1476|title=Sedimentation Problems with Dams|publisher=Internationalrivers.org|accessdate=2010-07-16}}</ref> Since turbine gates are often opened intermittently, rapid or even daily fluctuations in river flow are observed.
+====Water loss by evaporation====
+A 2011 study by the United States National Renewable Energy Laboratory concluded that hydroelectric plants in the U.S. consumed between 1,425 and 18,000 gallons of water per megawatt-hour (gal/MWh) of electricity generated, through evaporation losses in the reservoir. The median loss was 4,491 gal/MWh, which is higher than the loss for generation technologies that use cooling towers, including concentrating solar power (865 gal/MWh for CSP trough, 786 gal/MWh for CSP tower), coal (687 gal/MWh), nuclear (672 gal/MWh), and natural gas (198 gal/MWh). Where there are multiple uses of reservoirs such as water supply, recreation, and flood control,  all reservoir evaporation is attributed to power production.<ref>John Macknick and others, [http://www.nrel.gov/docs/fy11osti/50900.pdf A Review of Operational Water Consumption and Withdrawal Factors for Electricity Generating Technologies], National Renewable Energy Laboratory, Technical Report NREL/TP-6A20-50900.</ref>
+====Siltation and flow shortage====
+When water flows it has the ability to transport particles heavier than itself downstream. This has a negative effect on dams and subsequently their power stations, particularly those on rivers or within catchment areas with high siltation. [[Siltation]] can fill a reservoir and reduce its capacity to control floods along with causing additional horizontal pressure on the upstream portion of the dam. Eventually, some reservoirs can become full of sediment and useless or over-top during a flood and fail.<ref>{{cite web|last=Patrick James|first=H Chansen|title=Teaching Case Studies in Reservoir Siltation and Catchment Erosion|url=http://www.ijee.dit.ie/articles/Vol14-4/ijee1012.pdf|publisher=TEMPUS Publications|location=Great Britain|pages=265–275|year=1998|deadurl=yes|archiveurl=https://web.archive.org/web/20090902184753/http://www.ijee.dit.ie/articles/Vol14-4/ijee1012.pdf|archivedate=2009-09-02|df=}}</ref><ref>{{cite book|last=Șentürk|first=Fuat|title=Hydraulics of dams and reservoirs|year=1994|publisher=Water Resources Publications|location=Highlands Ranch, Colo.|isbn=0-918334-80-2|edition=reference.|page=375}}</ref>
+Changes in the amount of river flow will correlate with the amount of energy produced by a dam. Lower river flows will reduce the amount of live storage in a reservoir therefore reducing the amount of water that can be used for hydroelectricity. The result of diminished river flow can be power shortages in areas that depend heavily on hydroelectric power. The risk of flow shortage may increase as a result of [[climate change]].<ref name=ODI1>Frauke Urban and Tom Mitchell 2011. [http://www.odi.org.uk/resources/details.asp?id=5792&title=climate-change-disasters-electricity-generation Climate change, disasters and electricity generation] {{webarchive |url=https://web.archive.org/web/20120920024704/http://www.odi.org.uk/resources/details.asp?id=5792&title=climate-change-disasters-electricity-generation |date=September 20, 2012 }}. London: [[Overseas Development Institute]] and [[Institute of Development Studies]]</ref> One study from the [[Colorado River]] in the United States suggest that modest climate changes, such as an increase in temperature in 2 degree Celsius resulting in a 10% decline in precipitation, might reduce river run-off by up to 40%.<ref name=ODI1/> [[Brazil]] in particular is vulnerable due to its heavy reliance on hydroelectricity, as increasing temperatures, lower water ﬂow and alterations in the rainfall regime, could reduce total energy production by 7% annually by the end of the century.<ref name=ODI1/>
+====Methane emissions (from reservoirs)====
+[[File:Hoover Dam Nevada Luftaufnahme.jpg|thumb|The [[Hoover Dam]] in the [[United States]] is a large conventional dammed-hydro facility, with an installed capacity of {{nowrap|2,080 [[Megawatt|MW]]}}.]]
+{{See also|Environmental impacts of reservoirs}}
+Lower positive impacts are found in the tropical regions, as it has been noted that the reservoirs of power plants in tropical regions produce substantial amounts of [[methane]]. This is due to plant material in flooded areas decaying in an [[Hypoxia (environmental)|anaerobic]] environment, and forming methane, a [[greenhouse gas]]. According to the [[World Commission on Dams]] report,<ref>{{cite web|url=http://www.dams.org/report/|title=WCD Findal Report|publisher=Dams.org|date=2000-11-16|deadurl=yes|archiveurl=https://web.archive.org/web/20130821120709/http://www.dams.org/report/|archivedate=2013-08-21|df=}}</ref> 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.<ref>{{cite web|url=https://www.newscientist.com/article.ns?id=dn7046|title=Hydroelectric power's dirty secret revealed|publisher=Newscientist.com}}</ref>
+In [[Boreal forest|boreal]] reservoirs of Canada and Northern Europe, however, [[Greenhouse gas#Life-cycle greenhouse-gas emissions of energy sources|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.<ref>{{cite web|url=http://inhabitat.com/2006/12/01/rediscovered-wood-the-triton-sawfish/#more-1973|title="Rediscovered" Wood & The Triton Sawfish|publisher=Inhabitat|date=2006-11-16}}</ref>
+====Relocation====
+Another disadvantage of hydroelectric dams is the need to relocate the people living where the reservoirs are planned. In 2000, the World Commission on Dams estimated that dams had physically displaced 40-80 million people worldwide.<ref>{{cite web|url=http://internationalrivers.org/en/way-forward/world-commission-dams/world-commission-dams-framework-brief-introduction|title=Briefing of World Commission on Dams|publisher=Internationalrivers.org|date=2008-02-29}}</ref>
+====Failure risks====
+{{See also|Dam failure|List of hydroelectric power station failures}}
+Because large conventional dammed-hydro facilities hold back large volumes of water, a failure due to poor construction, natural disasters or sabotage can be catastrophic to downriver settlements and infrastructure.
+During Typhoon Nina in 1975 [[Banqiao Dam]] failed in Southern China when more than a year's worth of rain fell within 24 hours. The resulting flood resulted in the deaths of 26,000 people, and another 145,000 from epidemics. Millions were left homeless.
+The creation of a dam in a geologically inappropriate location may cause disasters such as 1963 disaster at [[Vajont Dam]] in Italy, where almost 2,000 people died.<ref name=":1">References may be found in the list of [[Dam failure]]s.</ref>
+The [[Malpasset Dam]] failure in [[Fréjus]] on the [[French Riviera]] (Côte d'Azur), southern France, collapsed on December 2, 1959, killing 423 people in the resulting flood.<ref>http://ecolo.org/documents/documents_in_french/malpasset/malpasset.htm retrieved 02sep2015</ref>
+Smaller dams and [[micro hydro]] facilities create less risk, but can form continuing hazards even after being decommissioned. For example, the small earthen embankment [[Kelly Barnes Dam]] failed in 1977, twenty years after its power station was decommissioned; causing 39 deaths.<ref name=":2">[http://ga.water.usgs.gov/news/historical-toccoa/ Toccoa Flood] USGS Historical Site, retrieved 02sep2009</ref>
+===Comparison and interactions with other methods of power generation===
+Hydroelectricity eliminates the [[flue gas emissions from fossil fuel combustion]], including pollutants such as [[sulfur dioxide]], [[nitric oxide]], [[carbon monoxide]], dust, and [[mercury (element)|mercury]] in the [[coal]]. Hydroelectricity also avoids the hazards of [[coal mining]] and the indirect health effects of coal emissions.
+====Nuclear power====
+Compared to [[nuclear power]], hydroelectricity construction requires altering large areas of the environment while a nuclear power station has a small footprint, and hydro-powerstation failures have caused tens of thousands of more deaths than any nuclear station failure.<ref name=":0"/><ref name=":1"/><ref name=":2"/> The creation of [[Garrison Dam]], for example, required Native American land to create Lake Sakakawea, which has a shoreline of 1,320 miles, and caused the inhabitants to sell 94% of their arable land for $7.5 million in 1949.<ref>Lawson, Michael L. (1982). ''Dammed Indians: the Pick-Sloan Plan and the Missouri River Sioux, 1944–1980''. Norman: University of Oklahoma Press.</ref>
+However, nuclear power is relatively inflexible; although nuclear power can reduce its output reasonably quickly. Since the cost of nuclear power is dominated by its high infrastructure costs, the cost per unit energy goes up significantly with low production. Because of this, nuclear power is mostly used for [[baseload]]. By way of contrast, hydroelectricity can supply peak power at much lower cost. Hydroelectricity is thus often used to complement nuclear or other sources for [[load following]]. Country examples were they are paired in a close to 50/50 share include [[Electricity sector in Switzerland|the electric grid in Switzerland]],  the [[Electricity sector in Sweden]] and to a lesser extent, [[Energy in Ukraine#Electricity|Ukraine]] and the [[Electricity sector in Finland]].
+====Wind power====
+[[Wind power]] goes through predictable [[Variable renewable energy|variation]] by season, but is [[Intermittent energy source|intermittent]] on a daily basis. Maximum wind generation has little relationship to peak daily electricity consumption, the wind may peak at night when power isn't needed or be still during the day when electrical demand is highest. Occasionally weather patterns can result in low wind for days or weeks at a time, a hydroelectric reservoir capable of storing weeks of output is useful to balance generation on the grid. Peak wind power can be offset by minimum hydropower and minimum wind can be offset with maximum hydropower. In this way the easily regulated character of hydroelectricity is used to compensate for the intermittent nature of wind power. Conversely, in some cases wind power can be used to spare water for later use in dry seasons.
+In areas that do not have hydropower, [[pumped storage]] serves a similar role, but at a much higher cost and 20% lower efficiency. An example of this is [[Electricity sector in Norway|Norway's trading]] with [[Sweden]], [[Denmark]], the [[Netherlands]] and possibly [[Germany]] or the [[United Kingdom|UK]] in the future.<ref>https://www.sintef.no/en/latest-news/norway-is-europes-cheapest-battery/</ref> Norway is 98% hydropower, while it's flatland neighbors are installing wind power.
+==World hydroelectric capacity==
+[[File:Ren2008.svg|thumb|upright=1.35|World renewable energy share (2008)]]
+[[File:Top 5 Hydropower-Producing Countries.png|thumb|upright=1.35|Trends in the top five hydroelectricity-producing countries]]
+{{See also|List of countries by electricity production from renewable sources|Cost of electricity by source}}
+{{See also|Category:Hydroelectricity by country}}
+The ranking of hydro-electric capacity is either by actual annual energy production or by installed capacity power rating. In 2015 hydropower generated 16.6% of the worlds total electricity and 70% of all renewable electricity.<ref name="ren21.net"/>
+Hydropower is produced in 150 countries, with the Asia-Pacific region generated 32 percent of global hydropower in 2010. China is the largest hydroelectricity producer, with 721 terawatt-hours of production in 2010, representing around 17 percent of domestic electricity use. [[Brazil]], [[Canada]], [[New Zealand]], [[Norway]], [[Paraguay]], [[Austria]], [[Switzerland]], and [[Venezuela]] have a majority of the internal electric energy production from hydroelectric power. [[Paraguay]] produces 100% of its electricity from hydroelectric dams, and exports 90% of its production to Brazil and to Argentina. [[Norway]] produces 98–99% of its electricity from hydroelectric sources.<ref name=norway/>
+A hydro-electric station 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.<ref>[http://www.bp.com/liveassets/bp_internet/globalbp/globalbp_uk_english/reports_and_publications/statistical_energy_review_2009/STAGING/local_assets/downloads/spreadsheets/statistical_review_full_report_workbook_2009.xls Consumption BP.com]{{dead link|date=March 2018|bot=medic}}{{cbignore|bot=medic}}</ref>
+{| class="wikitable sortable" style="margin:auto;"
+|+ Ten of the largest hydroelectric producers as at 2014.<ref name=norway>{{cite news |first= |last= |authorlink= |coauthors= |title=Binge and purge |url=http://www.economist.com/displaystory.cfm?story_id=12970769 |quote=98-99% of Norway’s electricity comes from hydroelectric plants. |work=[[The Economist]] |accessdate=2009-01-30 |date=2009-01-22}}</ref><ref name="IEA2015">{{cite web |url=https://www.iea.org/publications/freepublications/publication/KeyWorld_Statistics_2015.pdf |title=2015 Key World Energy Statistics |date= |accessdate=1 June 2016 |work=report |format=PDF |publisher=International Energy Agency (IEA) |author=}}</ref><ref>{{cite web|title=Indicators 2009, National Electric Power Industry|url=http://www.sdpc.gov.cn/tztg/W020100106306926853623.doc|publisher=Chinese Government|accessdate=18 July 2010}}</ref>
+|-
+! Country !! data-sort-type="numeric"|Annual hydroelectric<br>production ([[TWh]]) !! data-sort-type="numeric"|Installed<br>capacity ([[Gigawatt|GW]]) !! data-sort-type="numeric"|Capacity<br>factor !! data-sort-type="numeric"|% of total <br>production
+|-
+| {{flag|China}} || align="right"|1064 || align="right"|311 || align="right"|0.37 || align="right"|18.7%
+|-
+| {{flag|Canada}} || align="right"|383 || align="right"|76 || align="right"|0.59 || align="right"|58.3%
+|-
+| {{flag|Brazil}} || align="right"|373 || align="right"|89 || align="right"|0.56 || align="right"|63.2%
+|-
+| {{flag|United States}} || align="right"|282 || align="right"|102 || align="right"|0.42 || align="right"|6.5%
+|-
+| {{flag|Russia}} || align="right"|177 || align="right"|51 || align="right"|0.42 || align="right"|16.7%
+|-
+| {{flag|India}} || align="right"|132 || align="right"|40 || align="right"|0.43 || align="right"|10.2%
+|-
+| {{flag|Norway}} || align="right"|129 || align="right"|31 || align="right"|0.49 || align="right"|96.0%
+|-
+| {{flag|Japan}} || align="right"|87 || align="right"|50 || align="right"|0.37 || align="right"|8.4%
+|-
+| {{flag|Venezuela}} || align="right"|87 || align="right"|15 || align="right"|0.67 || align="right"|68.3%
+|-
+| {{flag|France}} || align="right"|69 || align="right"|25 || align="right"|0.46 || align="right"|12.2%
+|}
+==Major projects under construction==
+{{update section|date=February 2018}}
+{| class="wikitable sortable"
+|-
+! Name
+! data-sort-type="number"| Maximum Capacity (MW)
+! Country
+! Construction started
+! Scheduled completion
+! Comments
+|-
+|[[Belo Monte Dam]]
+|11,181
+|[[Brazil]]
+|March, 2011
+|2015
+|Preliminary construction underway.<ref>{{cite web|title=Belo Monte hydroelectric dam construction work begins|url=https://www.theguardian.com/environment/2011/mar/10/belo-monte-hydroelectric-work|publisher=Guardian UK|accessdate=2 April 2011|date=10 March 2011}}</ref>
+Construction suspended 14 days by court order Aug 2012<ref>{{cite web|title= Belo Monte dam construction halted by Brazilian court|url=https://www.theguardian.com/world/2012/aug/16/belo-monte-dam-construction-suspended|publisher=Guardian UK|accessdate=24 August 2012|date=16 August 2012}}</ref>
+|-
+|[[Siang Upper HE Project]]
+|11,000
+|[[India]]
+|April, 2009
+|2024
+|Multi-phase construction over a period of 15 years. Construction was delayed due to dispute with China.<ref>{{cite web|url=http://www.thehindubusinessline.com/2006/03/24/stories/2006032401830500.htm |title=Upper Siang project likely to be relocated on Chinese concerns |publisher=Thehindubusinessline.com |date=2006-03-24 |accessdate=2012-07-22}}</ref>
+|-
+|[[Tasang Dam]]
+|7,110
+|[[Burma]]
+|March, 2007
+|2022
+|Controversial 228 meter tall dam with capacity to produce 35,446 GWh annually.
+|-
+|[[Xiangjiaba Dam]]
+|6,400
+|[[People's Republic of China|China]]
+|November 26, 2006
+|2015
+|The last generator was commissioned on July 9, 2014
+|-
+|[[Grand Ethiopian Renaissance Dam]]
+|6,000
+|[[Ethiopia]]
+|2011
+|2017
+| Located in the upper Nile Basin, drawing complaint from Egypt
+|-
+|[[Nuozhadu Dam]]
+|5,850
+|[[People's Republic of China|China]]
+|2006
+|2017
+|
+|-
+|[[Jinping 2 Hydropower Station]]
+|4,800
+|[[People's Republic of China|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.
+|-
+|[[Diamer-Bhasha Dam]]
+|4,500
+|[[Pakistan]]
+|October 18, 2011
+|2023
+|
+|-
+|[[Jinping 1 Hydropower Station]]
+|3,600
+|[[People's Republic of China|China]]
+|November 11, 2005
+|2014
+|The sixth and final generator was commissioned on 15 July 2014
+|-
+|[[Jirau Power Station]]
+|3,300
+|[[Brazil]]
+|2008
+|2013
+|Construction halted in March 2011 due to worker riots.<ref>{{cite web|title=Brazil Sends Forces to Jirau Dam After Riots|url=https://www.wsj.com/articles/SB10001424052748704608504576208640384691826|publisher=Wall Street Journal|accessdate=2 April 2011|date=18 March 2011}}</ref>
+|-
+|[[Guanyinyan Dam]]
+|3,000
+|[[People's Republic of China|China]]
+|2008
+|2015
+|Construction of the roads and spillway started.
+|-
+|[[Lianghekou Dam]]<ref>{{cite web |url=http://www.ehdc.com.cn/newsite/DisplayNewsMaster/ShowNews.aspx?Id=1175 |title=二滩水电开发有限责任公司 |publisher=Ehdc.com.cn |date=2009-04-25 |accessdate=2012-07-22 |deadurl=yes |archiveurl=https://web.archive.org/web/20121018201733/http://www.ehdc.com.cn/newsite/DisplayNewsMaster/ShowNews.aspx?Id=1175 |archivedate=2012-10-18 |df= }}</ref>
+|3,000
+|[[People's Republic of China|China]]
+|2014
+|2023
+|
+|-
+|[[Dagangshan Dam]]
+|2,600
+|[[People's Republic of China|China]]
+|August 15, 2008<ref>{{cite web |url=http://www.cb600.cn/info_view.asp?id=1357280 |title=Archived copy |accessdate=2008-12-12 |deadurl=yes |archiveurl=https://web.archive.org/web/20110707013437/http://www.cb600.cn/info_view.asp?id=1357280 |archivedate=2011-07-07 |df= }}</ref>
+|2016
+|
+|-
+|[[Liyuan Dam]]
+|2,400
+|[[People's Republic of China|China]]
+|2008<ref>{{cite web|url=http://zt.xxgk.yn.gov.cn/canton_model12/newsview.aspx?id=368628|title=陆良县人口和计划生育局|publisher=Zt.xxgk.yn.gov.cn|date=|accessdate=2012-07-22|deadurl=yes|archiveurl=https://web.archive.org/web/20120717015158/http://zt.xxgk.yn.gov.cn/canton_model12/newsview.aspx?id=368628|archivedate=2012-07-17|df=}}</ref>
+|2013
+|
+|-
+|[[Tocoma Dam]] [[Bolívar (state)|Bolívar State]]
+|2,160
+|[[Venezuela]]
+|2004
+|2014
+|This power station would be the last development in the Low Caroni Basin, bringing the total to six power stations on the same river, including the 10,000MW [[Guri (Simón Bolívar)|Guri Dam]].<ref>{{cite web|url=http://idbgroup.org/exr/doc98/pro/pvel1003-06eng.pdf |format=PDF |title=Caroní River Watershed Management Plan |last=Staff |year=2004 |publisher=Inter-America Development Bank |accessdate=2008-10-25 |deadurl=yes |archiveurl=https://web.archive.org/web/20081028220929/http://idbgroup.org/exr/doc98/pro/pvel1003-06eng.pdf |archivedate=October 28, 2008 }}</ref>
+|-
+|[[Ludila Dam]]
+|2,100
+|[[People's Republic of China|China]]
+|2007
+|2015
+|Brief construction halt in 2009 for environmental assessment.
+|-
+|[[Shuangjiangkou Dam]]
+|2,000
+|[[People's Republic of China|China]]
+|December, 2007<ref>[http://www.cjwsjy.com.cn/News/Company/200808055706.htm CJWSJY.com.cn] {{webarchive |url=https://web.archive.org/web/20100629051317/http://www.cjwsjy.com.cn/News/Company/200808055706.htm |date=June 29, 2010 }}</ref>
+|2018
+|The dam will be 312 m high.
+|-
+|[[Ahai Dam]]
+|2,000
+|[[People's Republic of China|China]]
+|July 27, 2006
+|2015
+|
+|-
+|[[Teles Pires Dam]]
+|1,820
+|[[Brazil]]
+|2011
+|2015
+|
+|-
+|[[Site C Dam]]
+|1,100
+|[[Canada]]
+|2015
+|2024
+|First large dam in western Canada since 1984
+|-
+|[[Lower Subansiri Dam]]
+|2,000
+|[[India]]
+|2007
+|2016
+|
+|}
+==See also==
+{{portal|Renewable energy|Energy|Water}}
+* [[Hydraulic engineering]]
+* [[International Rivers]]
+* [[List of energy storage projects]]
+* [[List of hydroelectric power station failures]]
+* [[List of hydroelectric power stations]]
+* [[List of largest hydroelectric power stations in the United States]]
+* [[List of largest power stations in the world]]
+* [[Xcel Company Fire|Xcel Energy Cabin Creek Hydroelectric Plant Fire]]
+* [[List of renewable energy topics by country|Renewable energy by country]]
+==References==
+{{Reflist|30em}}
+==External links==
+{{Commons category|Hydroelectricity}}
+*[http://www.hydropower.org/ International Hydropower Association]
+*{{dmoz|Science/Technology/Energy/Renewable/Hydro/}}
+*[http://www.hydro.org/ National Hydropower Association, USA]
+*[http://www.hydroreform.org/ Hydropower Reform Coalition]
+*[http://www.dameffects.org/ Interactive demonstration on the effects of dams on rivers]
+*[https://web.archive.org/web/20110501225851/http://www.esha.be/ European Small Hydropower Association]
+*[http://www.iec.ch/dyn/www/f?p=103:7:0::::FSP_ORG_ID,FSP_LANG_ID:1228,25 IEC TC 4: Hydraulic turbines] (International Electrotechnical Commission - Technical Committee 4) IEC TC 4 portal with access to scope, documents and [http://tc4.iec.ch/index-tc4.html TC 4 website]
+{{Electricity generation}}
+{{Hydropower}}
+{{Energy country lists}}
+{{Authority control}}
+[[Category:Hydroelectricity| ]]
+[[Category:Landscape]]
+[[Category:Sustainable technologies]]

Revision as of 08:26, 20 July 2018