Waterwheels, turbines, and millsIn India, water wheels and watermills were built; in Imperial Rome, water powered mills produced flour from grain, and were also used for sawing timber and stone; in China, watermills were widely used since the Han Dynasty. In China and the rest of the Far East, hydraulically operated "pot wheel" pumps raised water into irrigation canals.In 1753, French engineer Bernard Forest de Blidor 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.[1] The growing demand for the Industrial Revolution would drive development as well.[2]The power of a wave of water released from a tank was used for extraction of metal ores in a method known as hushing. The method was first used at the Dolaucothi gold mine in Wales from 75 AD onwards, but had been developed in Spain at such mines as Las Medulas. Hushing was also widely used in Britain in the Medieval and later periods to extract lead and tin ores. It later evolved into hydraulic mining when used during the California gold rush.At the beginning of the Industrial revolution in Britain, water was the main source of power for new inventions such as Richard Arkwright's water frame.[3] Although the use of water power gave way to steam power in many of the larger mills and factories, it was still used during the 18th and 19th centuries for many smaller operations, such as driving the bellows in small blast furnaces (e.g. the Dyfi Furnace)[4] and gristmills, such as those built at Saint Anthony Falls, which uses the 50-foot (15m) drop in the Mississippi R Prevents floods: The dams also help prevent floods in the areas adjoining the large rivers. iver.

In the 1830s, at the early peak in U.S. canal-building, hydropower provided the energy to transport barge traffic up and down steep hills using inclined plane railroads. As railroads overtook canals for transportation, canal systems were modified and developed into hydropower systems; the history of Lowell, Massachusetts is a classic example of commercial development and industrialization, built upon the availability of water power.Technological advances had moved the open water wheel into an enclosed turbine or water motor. In 1848 James B. Francis, while working as head engineer of Lowell's Locks and Canals company, improved on these designs to create a turbine with 90% efficiency. He applied scientific principles and testing methods to the problem of turbine design. His mathematical and graphical calculation methods allowed confident design of high efficiency turbines to exactly match a site's specific flow conditions. The Francis reaction turbine is still in wide use today. In the 1870s, deriving from uses in the California mining industry, Lester Allan Pelton developed the high efficiency Pelton wheel impulse turbine, which utilized hydropower from the high head streams characteristic of the mountainous California interior. Irrigation of farms: Water from the dams can also be used for the irrigation of farm lands thus producing the agriculture outputs throughout the year even in the areas where there is scanty or no rainfall.Hydraulic power-pipe networksHydraulic power networks also developed, using pipes to carrying pressurized water and transmit mechanical power from the source to end users elsewhere locally; the power source was normally a head of water, which could also be assisted by a pump. These were extensive in Victorian cities in the United Kingdom. A hydraulic power network was also developed in Geneva, Switzerland. The world famous Jet d'Eau was originally designed as the over-pressure relief valve for the network.[5]Compressed air hydroSee also: TrompeWhere there is a plentiful head of water it can be made to generate compressed air directly without moving parts. In these designs, a falling column of water is purposely mixed with air bubbles generated through turbulence or a venturi pressure reducer at the high level intake. This is allowed to fall down a shaft into a subterranean, high-roofed chamber where the now-compressed air separates from the water and becomes trapped. The height of falling water column maintains compression of the air in the top of the chamber, while an outlet, submerged below the water level in the chamber allows water to flow back to the surface at a lower level than the intake. A separate outlet in the roof of the chamber supplies the compressed air. A facility on this principle was built on the Montreal River at Ragged Shutes near Cobalt, Ontario in 1910 and supplied 5,000 horsepower to nearby mines.[6]21st CenturyHaving fallen out of favor during the late 20th century due to the disruptive ecological and social effects of large impoundments, hydropower enjoyed a revival by 2013 as international institutions such as the World Bank tried to find solutions to economic development which avoided adding substantial amounts of carbon to the atmosphere.[7]Hydropower typesMain article: Hydroelectricity

A conventional dammed-hydro facility (hydroelectric dam) is the most common type of hydroelectric power generation. Conventional hydroelectric, referring to hydroelectric dams. Run-of-the-river hydroelectricity, which captures the kinetic energy in rivers or streams, without the use of dams. Small hydro projects are 10 megawatts or less and often have no artificial reservoirs. Micro hydro projects provide a few kilowatts to a few hundred kilowatts to isolated homes, villages, or small industries. Conduit hydroelectricity projects utilize water which has already been diverted for use elsewhere; in a municipal water system for example. Pumped-storage hydroelectricity stores water pumped during periods of low demand to be released for generation when demand is high.A hydropower resource can be evaluated by its available power. Power is a function of the hydraulic head and rate of fluid flow. The head is the energy per unit weight (or unit mass) of water. The static head is proportional to the difference in height through which the water falls. Dynamic head is related to the velocity of moving water. Each unit of water can do an amount of work equal to its weight times the head. The power available from falling water can be calculated from the flow rate and density of water, the height of fall, and the local acceleration due to gravity. In SI units, the power is: Can easily work during high peak daily loads: The daily demand of power is not constant throughout the day. The peak power occurs at night. It is very difficult to start and stop the thermal and nuclear power plants on daily basis. The hydroelectric power plants can be easily started and stopped without consuming much time. Water can be collected in the dam throughout the day and this can be used to generate electricity during peak periods. ritten by: Haresh Khemaniedited by: Lamar Stonecypherupdated: 9/19/2008Impacts and Trends Hydroelectric power is a clean source of renewable energy where an adequate water source is readily available. Hydropower plants provide inexpensive electricity without environmental pollution such as air emissions or waste byproducts. And, unlike other energy sources such as fossil fuels , water is not consumed during electrical production, but can be reused for other purposes. Long life: The life of hydroelectric power plants is longer than the life of thermal power plants. There are some hydroelectric power plants that were built more than 50-100 years ago and are still running.However, hydropower plants that rely on impoundments can negatively affect the reservoir site and the surrounding area. New reservoirs will permanently flood valleys that may have contained towns, scenic locations, and farmland. The permanent inundation also destroys fish and wildlife habitat that once existed at the reservoir site; however, new and different habitat is created. Hydropower operations that use run-of-the-river dams can block the passage of migrating fish, such as salmon. For example, many large dams in the Columbia River Basin impede Pacific salmon during their annual migrations through the river system. Only 2,400 of the 80,000 dams in the United States are used for hydroelectric power. It is costly to construct a new hydroelectric power plant, and construction uses much water and land. In addition, environmental concerns have been voiced against their use. According to the U.S. Geological Survey, the likely trend for the future is toward small-scale hydroelectric power plants that can generate electricity for single communities. No air-pollution is created: Since the hydroelectric power plants dont burn any fuel no pollution is caused by them. It does not emit harmful gases and particulate matter, thus keeps the surrounding atmosphere clean and healthy for living. written by: Jayant R Rowedited by: Lamar Stonecypherupdated: 8/23/2011No fuel required: One of the major advantages of the hydroelectric power plants is that they dont require any fuel for producing power. The hydroelectric power plants utilize renewable energy of water to generating electricity.SEE ALSO A RMY C ORPS OF E NGINEERS , U.S. ; B UREAU OF R ECLAMATION , U.S. ; C OLUMBIA R IVER B ASIN ; C ONFLICT AND W ATER ; D AMS ; E NERGY FROM THE O CEAN ; G EOTHERMAL E NERGY ; H OOVER D AM ; PLANNING AND M ANAGEMENT , H ISTORY OF W ATER R ESOURCES ; R ESERVOIRS , M ULTIPURPOSE ; S ALMON D ECLINE AND R ECOVERY ; S ECURITY AND W ATER ; T ENNESSEE V ALLEY A UTHORITY . William Arthur Atkins

Read more: http://www.waterencyclopedia.com/Ge-Hy/Hydroelectric-Power.html#ixzz2v9l87rwwBibliography Graham, Ian. Water Power. Austin, TX: Raintree Steck-Vaughn, 1999. Kellert, Stephen R., ed. Macmillan Encyclopedia of the Environment, vol. 3. New York: Macmillan Library Reference USA, 1997. Internet Resources Hydroelectric Power Water Use. Water Science for Schools, U.S. Geological Survey. . International Small-Hydro Atlas. .

Read more: http://www.waterencyclopedia.com/Ge-Hy/Hydroelectric-Power.html#ixzz2v9lQje6JSafety of the dams: The safety of the dams is very crucial as it can affect lives of millions of people. In this age when the terrorists attacks are increasing there are greater concerns for the safety of large dams.Affects on environment: Though the hydroelectric power plants do not require any fuel, dont produce greenhouse gases and dont create pollution directly, it does have a number of detrimental affects on the environment. The construction activity of the dam itself disturbs the environment to a great scale.When the course of water is changed the surrounding areas may get flooded disturbing natural flora and fauna. Human beings living in these areas also get displaced. The large quantities of water collected due to the floods also emit a lot of greenhouses gases like carbon dioxide. Thus though the hydroelectric power plants dont generate greenhouse gases directly, they generate it indirectly. Over several years, a number of vehicles coming to the construction site for loading and unloading materials also emit greenhouse gases that directly affect the sensitive plants and animal life found in forests.Very high capital cost or investment: The initial cost of the construction of the hydroelectric power plants is very high. It also takes long time to construct the plant. Lots of designing, planning, and testing goes into the construction of the dams. Each dam is unique in itself so the designs cannot be standardized. Construction of dams requires lots of steel, iron and cement which make the hydroelectric power plants very expensive. The project can contain multiple risks to humans and/or the environment. Overall, lots of time, money and human efforts are invested in the construction of hydroelectric power plants. 6) High quality construction: The construction materials used for the construction of the dams should be of high quality. Any breakage in the dam can cause large scale destruction of the human, plant and animal lives. The failure of the Banqiao Dam in China resulted in the deaths of more than 171,000 people and millions of people were rendered homeless.7) Site specific: The hydroelectric power plants cannot be constructed at any locations. They can be constructed only in places where abundant quantity of water is available at sufficient height and throughout the year. A number of other safety parameters also have to be considered. Construction of the dams at inappropriate locations can cause human casualties. An example of the inappropriate locations is of the Vajont Dam in Italy, where almost 2000 people died, in the year 1963.written by: Haresh Khemaniedited by: Lamar Stonecypherupdated: 10/19/2009 advantages Inexhaustible fuel source Minimal environmental impact Viable source--relatively useful levels of energy production Can be used throughout the worldWilliam HoweTrust Points: 3645 Member Since: 10/10ydroelectric energy offers a number of advantages for people who use it, the environment, and electricity suppliers. Read on to learn more about the advantages of hydroelectric power:1. Using this type of energy to generate electricity is not dependent upon the price of uranium, oil, or other types of fuel. This makes electricity costs lower and more stable, one of its most significant advantages. 2. The pollution created by hydroelectric energy generation is quite minimal. There is some pollution involved in initially constructing the power stations, but this is true of all power plants. It also does not produce radioactive waste or involve the environmental impact of fuel being transported to it.3. It doesn't require many employees to run a hydroelectric station. According to wikipedia.org, most plants of this type are largely automated. This is another one of the advantages which help keep the cost of hydroelectricity low.4. Hydroelectric power stations can be set up in almost any size, depending upon the river or stream used to operate them; big enough to power a single home, factory, small town, or large city.5. Another of its advantages is that hydroelectric is a renewable form of energy, like wind and solar; it does not rely upon finite resources like natural gas or coal to generate power.6. Hydroelectric stations can operate for many years after they are built. Wikipedia.org states that a number of operational hydro stations were constructed fifty to one-hundred years ago; in contrast to this, IAEA.org indicates that the "design life" of nuclear power plants is generally thirty to forty years.7. Small hydro electricity generation systems sometimes offer more economic advantages for home owners than solar power, and tend to last longer than solar panels do.The above-mentioned factors make hydroelectric a form of energy generation which offers advantages with regard to cost, pollution, flexibility of installation, and conservation of resources.Hydropower is the cheapest way to generate electricity today. No other energy source, renewable or nonrenewable, can match it. Producing electricity from hydropower is cheap because, once a dam has been built and the equipment installed, the energy source-flowing water-is free.

Although Hydropower does present a few environmental problems the inherent technical, economic and environmental benefits of hydroelectric power make it an important contributor to the future world energy mix,Environmental ImpactsHydro-electric power plants have many environmental impacts, some of which are just beginning to be understood. These impacts, however, must be weighed against the environmental impacts of alternative sources of electricity. Until recently there was an almost universal belief that hydro power was a clean and environmentally safe method of producing electricity. Hydro-electric power plants do not emit any of the standard atmospheric pollutants such as carbon dioxide or sulfur dioxide given off by fossil fuel fired power plants. In this respect, hydro power is better than burning coal, oil or natural gas to produce electricity, as it does not contribute to global warming or acid rain. Similarly, hydro-electric power plants do not result in the risks of radioactive contamination associated with nuclear power plants. A few recent studies of large reservoirs created behind hydro dams have suggested that decaying vegetation, submerged by flooding, may give off quantities of greenhouse gases equivalent to those from other sources of electricity. If this turns out to be true, hydro-electric facilities such as the James Bay project in Quebec that flood large areas of land might be significant contributors to global warming. Run of the river hydro plants without dams and reservoirs would not be a source of these greenhouse gases. ConclusionsHydro-electric power has always been an important part of the world's electricity supply, providing reliable, cost effective electricity, and will continue to do so in the future. Hydro power has environmental impacts which are very different from those of fossil fuel power plants. The actual effects of dams and reservoirs on various ecosystems are only now becoming understood. The future of hydro-electric power will depend upon future demand for electricity, as well as how societies value the environmental impacts of hydro-electric power copmpared to the impacts of other sources of electricity. Sources:Philip Raphals, "The Hidden Cost of Canada's Cheap Power", New Scientist, February 15, 1992. Geoffrey P. Sims, "Hydroelectric Energy", Energy Policy, october 1991. Eric M. Wilson, "Small-scale Hydroelectricity", Energy Policy, october 1991. Michael Brower, Cool Energy: The Renewable Solution to Global Warming, Union of Concerned Scientists, 1990. Solar Energy Research Institute, The Potential of Renewable Energy, An Interlaboratory White Paper, SERI/TP-260-3674, Golden Colorado, 1990.Peter Kakela, Gary Chilson & William Patric, "Low-Head Hydropower for Local Use", Environment, January/February 1984.To purchase a copy of this Fact Sheet, please visit the ICLEI Web Store where they are available for $3.50 (US) each or $50 (US) for the set of 30. We accept VISA and MasterCard through our secure server.