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80-473: Together with the adjacent 2,106 MW La Grande-2-A generating station (LG-2-A), commissioned in 1991–1992, it uses the reservoir and dam system of the Robert-Bourassa Reservoir to generate electricity. The two plants taken together account for more than 20% of Hydro-Québec's total installed capacity of 36,810 MW in 2009. It is Canada's largest hydroelectric power station , ranks in 15th place on

160-417: A dam constructed across a valley and rely on the natural topography to provide most of the basin of the reservoir. These reservoirs can either be on-stream reservoirs , which are located on the original streambed of the downstream river and are filled by creeks , rivers or rainwater that runs off the surrounding forested catchments, or off-stream reservoirs , which receive diverted water from

240-445: A pumping station ). Many gatehouses are strictly utilitarian, but especially in the nineteenth century, some were very elaborate. A set of outlet works is a device used to release and regulate water flow from a dam . Such devices usually consist of one or more pipes or tunnels through the embankment of the dam, directing water usually under high pressure to the river downstream. These structures are usually used when river flow exceeds

320-537: A block for migrating fish, trapping them in one area, producing food and a habitat for various water-birds. They can also flood various ecosystems on land and may cause extinctions. Creating reservoirs can alter the natural biogeochemical cycle of mercury . After a reservoir's initial formation, there is a large increase in the production of toxic methylmercury (MeHg) via microbial methylation in flooded soils and peat. MeHg levels have also been found to increase in zooplankton and in fish. Dams can severely reduce

400-636: A conventional oil-fired thermal generation plant. For instance, In 1990, the impoundment behind the Balbina Dam in Brazil (inaugurated in 1987) had over 20 times the impact on global warming than would generating the same power from fossil fuels, due to the large area flooded per unit of electricity generated. Another study published in the Global Biogeochemical Cycles also found that newly flooded reservoirs released more carbon dioxide and methane than

480-462: A cost of $ 348 million, and was paved over the next two years. The first stage of construction was the temporary diversion of the La Grande River; the tunnels had to be big enough to protect the construction site from floods, but not so large as to unnecessarily increase cost. Two diversion tunnels were drilled into the left bank of the river and were opened on April 27, 1975. For the next three and

560-473: A design flow of 3,100 cubic metres per second (110,000 cu ft/s). The Robert-Bourassa dam is located 117.5 kilometres (73.0 mi) from the mouth of the La Grande River, in the transition zone between the Laurentian Plateau (the elevated Canadian Shield ) and the coastal plain. It has a maximum height of 162 metres (531 ft) and is 2,836 metres (9,304 ft) long at the crest. The core of

640-529: A drop of water seep into the ocean without benefiting mankind." He created the reservoir named Parakrama Samudra ("sea of King Parakrama"). Vast artificial reservoirs were also built by various ancient kingdoms in Bengal, Assam, and Cambodia. Many dammed river reservoirs and most bank-side reservoirs are used to provide the raw water feed to a water treatment plant which delivers drinking water through water mains. The reservoir does not merely hold water until it

720-435: A feasibility study for a hydroelectric complex on the La Grande River. Another engineering firm, Asselin, Benoît, Boucher, Ducharme & Lapointe (ABBDL) was tasked with a feasibility study on the more southerly NBR (Nottaway, Broadback, Rupert) rivers. At RSW the development of the La Grande River was championed by François Rousseau, one of firm's associates and a former Hydro-Québec senior engineer. A final decision to build

800-411: A half years the flow of the river would be diverted through the tunnels. Each tunnel was 14.8 metres (49 ft) wide and 18 metres (59 ft) high; the north tunnel was 730 metres (2,400 ft) long and the south, 830 metres (2,720 ft). The tunnels were designed to carry the 65-year flood flow of the La Grande River, calculated at 7,500 cubic metres per second (260,000 cu ft/s). Since

880-455: A high-level reservoir is filled with water using high-performance electric pumps at times when electricity demand is low, and then uses this stored water to generate electricity by releasing the stored water into a low-level reservoir when electricity demand is high. Such systems are called pump-storage schemes. Reservoirs can be used in a number of ways to control how water flows through downstream waterways: Reservoirs can be used to balance

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960-570: A loss in both quantity and quality of water necessary for maintaining ecological balance and pose a risk of increasing severity and duration of droughts due to climate change. In summary, they consider it a misadaptation to climate change. Proponents of reservoirs or substitution reserves, on the other hand, see them as a solution for sustainable agriculture while waiting for a truly durable agricultural model. Without such reserves, they fear that unsustainable imported irrigation will be inevitable. They believe that these reservoirs should be accompanied by

1040-534: A maximum lift of 54.3 metres (178 ft). Each pump is powered by a 1,120 KW (1,500 hp) motor. The pumping station also served to divert water away from the Dessaulniers river bed, during the construction of dike D-20. The spillway , nicknamed Staircase of the Giants , is near the north end of the main dam and is part of dike D-4. It consists of a concrete control structure and a man-made waterfall discharging into

1120-419: A narrow valley or canyon may cover relatively little vegetation, while one situated on a plain may flood a great deal of vegetation. The site may be cleared of vegetation first or simply flooded. Tropical flooding can produce far more greenhouse gases than in temperate regions. The following table indicates reservoir emissions in milligrams per square meter per day for different bodies of water. Depending upon

1200-470: A nearby stream or aqueduct or pipeline water from other on-stream reservoirs. Dams are typically located at a narrow part of a downstream of a natural basin. The valley sides act as natural walls, with the dam located at the narrowest practical point to provide strength and the lowest cost of construction. In many reservoir construction projects, people have to be moved and re-housed, historical artifacts moved or rare environments relocated. Examples include

1280-549: A pump station was installed which removes water from the Dessaulniers to the Robert-Bourassa Reservoir. The pump station was designed to remove an annual average of 2.8 cubic metres per second (99 cu ft/s), from a drainage area of 160 square kilometres (62 sq mi). The pump station was commissioned in June 1977. It has four pumps with a capacity of 1.7 cubic metres per second (60 cu ft/s) each, with

1360-592: A reservoir is called the "conservation pool". In the United Kingdom, "top water level" describes the reservoir full state, while "fully drawn down" describes the minimum retained volume. There is a wide variety of software for modelling reservoirs, from the specialist Dam Safety Program Management Tools (DSPMT) to the relatively simple WAFLEX , to integrated models like the Water Evaluation And Planning system (WEAP) that place reservoir operations in

1440-450: A river of variable quality or size, bank-side reservoirs may be built to store the water. Such reservoirs are usually formed partly by excavation and partly by building a complete encircling bund or embankment , which may exceed 6 km (4 miles) in circumference. Both the floor of the reservoir and the bund must have an impermeable lining or core: initially these were often made of puddled clay , but this has generally been superseded by

1520-720: A river valley, with the potential to wash away towns and villages and cause considerable loss of life, such as the devastation following the failure of containment at Llyn Eigiau which killed 17 people. (see also List of dam failures ) A notable case of reservoirs being used as an instrument of war involved the British Royal Air Force Dambusters raid on Germany in World War II (codenamed " Operation Chastise " ), in which three German reservoir dams were selected to be breached in order to damage German infrastructure and manufacturing and power capabilities deriving from

1600-435: A stilling basin below the dam. The spillway has eight 12.2-metre (40 ft) wide gates, separated by 4.3-metre (14 ft) thick columns. The gates are opened and closed by cable winches , in order to control spills. The eight gates are all opened at the same time once every 15 years. Having passed through the gates, the kinetic energy of the water is dissipated in a 135-by-122-metre (443 ft × 400 ft) basin at

1680-574: A territorial project that unites all water stakeholders with the goal of preserving and enhancing natural environments. Two main types of reservoirs can be distinguished based on their mode of supply. Circa 3000 BC, the craters of extinct volcanoes in Arabia were used as reservoirs by farmers for their irrigation water. Dry climate and water scarcity in India led to early development of stepwells and other water resource management techniques, including

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1760-468: A watercourse that drains an existing body of water, interrupting a watercourse to form an embayment within it, excavating, or building any number of retaining walls or levees to enclose any area to store water. The term is also used technically to refer to certain forms of liquid storage, such the "coolant reservoir" that captures overflow of coolant in an automobile's cooling system. Dammed reservoirs are artificial lakes created and controlled by

1840-471: Is a natural lake whose level was raised by a low dam and into which the River Dee flows or discharges depending upon flow conditions, as part of the River Dee regulation system . This mode of operation is a form of hydraulic capacitance in the river system. Many reservoirs often allow some recreational uses, such as fishing and boating . Special rules may apply for the safety of the public and to protect

1920-480: Is a water reservoir for agricultural use. They are filled using pumped groundwater , pumped river water or water runoff and are typically used during the local dry season. This type of infrastructure has sparked an opposition movement in France, with numerous disputes and, for some projects, protests, especially in the former Poitou-Charentes region where violent demonstrations took place in 2022 and 2023. In Spain, there

2000-655: Is fraught with substantial land submergence, coastal reservoirs are preferred economically and technically since they do not use scarce land area. Many coastal reservoirs were constructed in Asia and Europe. Saemanguem in South Korea, Marina Barrage in Singapore, Qingcaosha in China, and Plover Cove in Hong Kong are a few such coastal reservoirs. Where water is pumped or siphoned from

2080-501: Is greater acceptance because all beneficiary users are involved in the implementation of the system. The specific debate about substitution reservoirs is part of a broader discussion related to reservoirs used for agricultural irrigation, regardless of their type, and a certain model of intensive agriculture. Opponents view these reservoirs as a monopolization of resources benefiting only a few, representing an outdated model of productive agriculture. They argue that these reservoirs lead to

2160-617: Is inhabited by a diverse array of aquatic flora and fauna. On November 27, 1978, the diversion tunnels were closed and water began to back up behind the dam. The enormous reservoir took over a year to completely fill. The water initially rose very fast: 43 metres (141 ft) during the first week, with 15 metres (49 ft) on the first day alone. The reservoir reached its minimum operational level of 167.6 metres (550 ft) on September 2, 1979, and reached its normal maximum level of 175.3 metres (575 ft) in December 1979. The construction of

2240-466: Is needed: it can also be the first part of the water treatment process. The time the water is held before it is released is known as the retention time . This is a design feature that allows particles and silts to settle out, as well as time for natural biological treatment using algae , bacteria and zooplankton that naturally live in the water. However natural limnological processes in temperate climate lakes produce temperature stratification in

2320-528: Is now used by the Aquarius Golf Club. Service reservoirs perform several functions, including ensuring sufficient head of water in the water distribution system and providing water capacity to even-out peak demand from consumers, enabling the treatment plant to run at optimum efficiency. Large service reservoirs can also be managed to reduce the cost of pumping by refilling the reservoir at times of day when energy costs are low. An irrigation reservoir

2400-520: Is poorly suited to forming a single large reservoir, a number of smaller reservoirs may be constructed in a chain, as in the River Taff valley where the Llwyn-on , Cantref and Beacons Reservoirs form a chain up the valley. Coastal reservoirs are fresh water storage reservoirs located on the sea coast near a river mouth to store the flood water of a river. As the land-based reservoir construction

2480-419: Is stored in the reservoir. Any excess water can be spilled via a specifically designed spillway. Stored water may be piped by gravity for use as drinking water , to generate hydro-electricity or to maintain river flows to support downstream uses. Occasionally reservoirs can be managed to retain water during high rainfall events to prevent or reduce downstream flooding. Some reservoirs support several uses, and

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2560-452: Is surfaced with riprap to reduce erosion. The original plan envisioned the construction of a concrete-face rock-fill dam , but this was rejected in favor of a more conventional embankment design, partly because of the lower cost, and also because the concrete face would have to be inspected from time to time requiring drainage of the reservoir. Because of the huge size of the reservoir, this would be essentially impossible. In order to hold

2640-466: Is the portion of the reservoir that can be used for flood control, power production, navigation , and downstream releases. In addition, a reservoir's "flood control capacity" is the amount of water it can regulate during flooding. The "surcharge capacity" is the capacity of the reservoir above the spillway crest that cannot be regulated. In the United States, the water below the normal maximum level of

2720-493: Is usually a canal or intake tower . A regulating gate or valve controls water flow into the pipes of the outlet works, which discharge downstream into a stilling basin or directly into the river. The inlets of the outlet works may consist of either gates or valves, or be composed of a more primitive system of stoplogs . Inlets may also contain a series of other devices for different purposes, including trash racks and fish screens . This architecture -related article

2800-498: The Duncan dykes (D17-D27), are located 30 kilometers (19 mi) south. The dam and dykes hold a reservoir covering an area of 2,835 square kilometres (1,095 sq mi) with a useful capacity of 19.365 billion m³. The generating station itself is located 137.2 meters (450 ft) underground , 6 kilometers (3.7 mi) downstream from the main dam. It hosts 16 Francis turbines, set up in two groups of eight each. In 1974, in what

2880-568: The La Grande River , a large river in Quebec's sparsely populated northern Quebec . It was also the first to be built, between 1974 and 1981. It was inaugurated by Premier René Lévesque of Quebec, on October 27, 1979. Design work on the generating station, dam and reservoir began in October 1970 when Montreal-based engineering firm Rousseau Sauvé Warren (RSW) was commissioned by Hydro-Québec to prepare

2960-448: The Ruhr and Eder rivers. The economic and social impact was derived from the enormous volumes of previously stored water that swept down the valleys, wreaking destruction. This raid later became the basis for several films. All reservoirs will have a monetary cost/benefit assessment made before construction to see if the project is worth proceeding with. However, such analysis can often omit

3040-543: The list of largest hydroelectric power stations and is the world's largest underground power station . Initially known as La Grande-2, it was renamed after Robert Bourassa who, as Premier of Quebec (1970–1976 and 1985–1994) gave the James Bay Project a vital political impetus. The Robert-Bourassa generating station is the main facility of the James Bay hydroelectric project , a large hydroelectric complex built on

3120-646: The 1800s, most of which are lined with brick. A good example is the Honor Oak Reservoir in London, constructed between 1901 and 1909. When it was completed it was said to be the largest brick built underground reservoir in the world and it is still one of the largest in Europe. This reservoir now forms part of the southern extension of the Thames Water Ring Main . The top of the reservoir has been grassed over and

3200-450: The Cree settlement at Fort George. The deadline was tight: 450 miles (720 km) in 450 days. The first challenge involved deploying teams of land surveyors and lumberjacks by seaplanes and helicopters to clear a path for a permanent road. Parallel to the path, a few kilometres away, an ice road was built to move heavy machinery north. The first milestone was reached on February 11, 1972, with

3280-536: The Duncan dikes partially blocked the flow of the Dessaulniers River, which is located to the southeast of the Robert-Bourassa Reservoir. The river flowed into Dessaulniers Lake at an elevation of 143.3 metres (470 ft), 32 metres (105 ft) below the level of the Robert-Bourassa Reservoir. To prevent the flooding of an additional 30 square kilometres (12 sq mi) and preserve the lake in its natural state,

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3360-710: The Meroitic town of Butana . The Hafirs catch the water during rainy seasons in order to ensure water is available for several months during dry seasons to supply drinking water, irrigate fields and water cattle. The Great Reservoir near the Lion Temple in Musawwarat es-Sufra is a notable hafir in Kush. In Sri Lanka , large reservoirs were created by ancient Sinhalese kings in order to store water for irrigation. The famous Sri Lankan king Parākramabāhu I of Sri Lanka said "Do not let

3440-485: The US. The capacity, volume, or storage of a reservoir is usually divided into distinguishable areas. Dead or inactive storage refers to water in a reservoir that cannot be drained by gravity through a dam's outlet works , spillway, or power plant intake and can only be pumped out. Dead storage allows sediments to settle, which improves water quality and also creates an area for fish during low levels. Active or live storage

3520-470: The amount of water reaching countries downstream of them, causing water stress between the countries, e.g. the Sudan and Egypt , which damages farming businesses in the downstream countries, and reduces drinking water. Outlet works A gatehouse , gate house , outlet works or valve house for a dam is a structure housing sluice gates , valves , or pumps (in which case it is more accurately called

3600-523: The area flooded versus power produced, a reservoir built for hydro- electricity generation can either reduce or increase the net production of greenhouse gases when compared to other sources of power. A study for the National Institute for Research in the Amazon found that hydroelectric reservoirs release a large pulse of carbon dioxide from decay of trees left standing in the reservoirs, especially during

3680-428: The base of the dam or some distance away. In a flat river valley a reservoir needs to be deep enough to create a head of water at the turbines; and if there are periods of drought the reservoir needs to hold enough water to average out the river's flow throughout the year(s). Run-of-the-river hydro in a steep valley with constant flow needs no reservoir. Some reservoirs generating hydroelectricity use pumped recharge:

3760-460: The build, often through a temporary tunnel or by-pass channel. In hilly regions, reservoirs are often constructed by enlarging existing lakes. Sometimes in such reservoirs, the new top water level exceeds the watershed height on one or more of the feeder streams such as at Llyn Clywedog in Mid Wales . In such cases additional side dams are required to contain the reservoir. Where the topography

3840-547: The building of a reservoir at Girnar in 3000 BC. Artificial lakes dating to the 5th century BC have been found in ancient Greece. The artificial Bhojsagar lake in present-day Madhya Pradesh state of India, constructed in the 11th century, covered 650 square kilometres (250 sq mi). The Kingdom of Kush invented the Hafir , a type of reservoir, during the Meroitic period . 800 ancient and modern hafirs have been registered in

3920-447: The capacity of the power plant or diversion capacity of the dam, but is not high enough to warrant use of the dam spillways . They may also be used when river flows must be bypassed due to maintenance work in the power station or diversion gates. Although similar in purpose to spillways, outlet works provide a more controlled release to meet downstream flow requirements. A typical set of outlet works begins in an intake structure, which

4000-442: The context of system-wide demands and supplies. In many countries large reservoirs are closely regulated to try to prevent or minimize failures of containment. While much of the effort is directed at the dam and its associated structures as the weakest part of the overall structure, the aim of such controls is to prevent an uncontrolled release of water from the reservoir. Reservoir failures can generate huge increases in flow down

4080-531: The dedication of the power plant by Quebec Premier René Lévesque . The underground complex, including a service tunnel, the generation room and a surge chamber , required the excavation of 2,350,000 cubic metres (83,000,000 cu ft) of material. The plant was constructed by Rousseau Sauvé Warren (RSW) of Montreal. Unlike other facilities in the James Bay Project, the LG2 was constructed to imperial rather than metric specifications, even though Canada had converted to

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4160-460: The developed world Naturally occurring lakes receive organic sediments which decay in an anaerobic environment releasing methane and carbon dioxide . The methane released is approximately 8 times more potent as a greenhouse gas than carbon dioxide. As a human-made reservoir fills, existing plants are submerged and during the years it takes for this matter to decay, will give off considerably more greenhouse gases than lakes do. A reservoir in

4240-507: The downstream river to maintain river quality, support fisheries, to maintain downstream industrial and recreational uses or for a range of other purposes. Such releases are known as compensation water . The units used for measuring reservoir areas and volumes vary from country to country. In most of the world, reservoir areas are expressed in square kilometers; in the United States, acres are commonly used. For volume, either cubic meters or cubic kilometers are widely used, with acre-feet used in

4320-414: The earthfill dam is made of glacial moraine which is impervious, and available in large quantities within a 10 kilometres (6.2 mi) radius of the dam site, due to extensive glaciation of the area during the last ice age . The core is slightly inclined upstream, to increase resistance against the immense pressure of water in the reservoir. The layers above consist of fill zones of varying coarseness, and

4400-440: The environmental impacts of dams and the reservoirs that they contain. Some impacts, such as the greenhouse gas production associated with concrete manufacture, are relatively easy to estimate. Other impacts on the natural environment and social and cultural effects can be more difficult to assess and to weigh in the balance but identification and quantification of these issues is now commonly required in major construction projects in

4480-491: The first decade after flooding. This elevates the global warming impact of the dams to levels much higher than would occur by generating the same power from fossil fuels . According to the World Commission on Dams report (Dams And Development), when the reservoir is relatively large and no prior clearing of forest in the flooded area was undertaken, greenhouse gas emissions from the reservoir could be higher than those of

4560-413: The flow in highly managed systems, taking in water during high flows and releasing it again during low flows. In order for this to work without pumping requires careful control of water levels using spillways . When a major storm approaches, the dam operators calculate the volume of water that the storm will add to the reservoir. If forecast storm water will overfill the reservoir, water is slowly let out of

4640-451: The foot of the control structure. It then flows down a 1,500-metre (4,900 ft) long rock channel with a vertical drop of 110-metre (360 ft) on its way back into the La Grande river. The channel has 10 steps ranging from 9.1 to 12.2 metres (30 to 40 ft) in height and 127 to 200 metres (417 to 656 ft) in length. The flow rate increases from 11 metres per second (36 ft/s) at

4720-478: The hydroelectric complex on the La Grande hydrographic system was made in 1972, after engineers determined the NBR project would be less cost effective because of the silty nature of the soils in the NBR area. The La Grande option had the added advantages of a lesser impact on First Nations hunting and fishing, on the boreal forest and would require less flooding. The main dam is located 117.5 kilometers (73.0 mi) from

4800-580: The hydroelectric reservoirs there do emit greenhouse gases, it is on a much smaller scale than thermal power plants of similar capacity. Hydropower typically emits 35 to 70 times less greenhouse gases per TWh of electricity than thermal power plants. A decrease in air pollution occurs when a dam is used in place of thermal power generation, since electricity produced from hydroelectric generation does not give rise to any flue gas emissions from fossil fuel combustion (including sulfur dioxide , nitric oxide and carbon monoxide from coal ). Dams can produce

4880-432: The landscape is relatively flat. Other service reservoirs can be storage pools, water tanks or sometimes entirely underground cisterns , especially in more hilly or mountainous country. Modern reserviors will often use geomembrane liners on their base to limit seepage and/or as floating covers to limit evaporation, particularly in arid climates. In the United Kingdom, Thames Water has many underground reservoirs built in

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4960-744: The metric system in the 1970s. The power station can be accessed either by an elevator or a tunnel. The plant has 16 Francis turbines , divided into two sets of eight each, and separated by a mounting area, workshops, control room, elevator shaft and ventilation system. The turbines were built by two partners of James Bay Energy (SEBJ). Units 1, 3, 5, 7, 10, 12, 14 and 16 were built by Marine Industries Limited (MIL), while units 2, 4, 6, 8, 9, 11, 13 and 15 were built by Canadian General Electric (alternators) and Dominion Engineering Works (turbines). The two groups have somewhat different characteristics. The turbines manufactured by MIL are lighter, 96 tonnes compared to 111, and have fifteen blades, compared to 11 for

5040-470: The modern use of rolled clay. The water stored in such reservoirs may stay there for several months, during which time normal biological processes may substantially reduce many contaminants and reduce turbidity . The use of bank-side reservoirs also allows water abstraction to be stopped for some time, for instance when the river is unacceptably polluted or when flow conditions are very low due to drought . The London water supply system exhibits one example of

5120-456: The mouth of the river, in the transition zone between the plateau and the coastal plain, and has a maximum height of 162 meters (531 ft). Twenty-nine dykes of various sizes close the reservoir. They are organized in three group: dykes D1-D4 are located north of the spillway, nicknamed the Staircase of the Giants , D5-D14 are located on the left shore of the river while a third group, nicknamed

5200-454: The opening of the 555 meters (1,821 ft) ice bridge crossing the Rupert River. The temporary road reached the La Grande River in December 1972, allowing the minimum necessary level of access needed to begin work – namely to construct housing for the thousands of people who would work on the dam for the next decade. A permanent road surfaced with gravel was completed on October 20, 1974, at

5280-415: The operating rules may be complex. Most modern reservoirs have a specially designed draw-off tower that can discharge water from the reservoir at different levels, both to access water as the water level falls, and to allow water of a specific quality to be discharged into the downstream river as "compensation water": the operators of many upland or in-river reservoirs have obligations to release water into

5360-466: The original construction schedule called for completion on February 15, 1980, the south diversion tunnel was scheduled to be closed in November 1978, during low river flows in the winter. However, the deadline was revised forward by 60 days, and the tunnel had to be reinforced to withstand harsh autumn conditions. After the dam was completed, the tunnels are still used as flood control outlet works and have

5440-536: The other group. Each turbine is rated at 339 MW at a 137-metre (449 ft) head and a speed of 133.33 rpm. The generators are rated at 370 megavolt amperes (MVA), which is increased to 390 MVA in the winter. Reservoir (water) A reservoir ( / ˈ r ɛ z ər v w ɑːr / ; from French réservoir [ʁezɛʁvwaʁ] ) is an enlarged lake behind a dam , usually built to store fresh water , often doubling for hydroelectric power generation . Reservoirs are created by controlling

5520-520: The perceived arrogance of American executives at the contractor, Bechtel Corporation . The first step towards the construction of the La Grande-2 generating station took place in June 1971, in Matagami , a small mining town located 630 kilometers (390 mi) south of La Grande River. Engineering firm Desjardins, Sauriol and Associates were tasked with the construction of a basic road to the future site and

5600-477: The pre-flooded landscape, noting that forest lands, wetlands, and preexisting water features all released differing amounts of carbon dioxide and methane both pre- and post-flooding. The Tucuruí Dam in Brazil (completed in 1984) had only 0.4 times the impact on global warming than would generating the same power from fossil fuels. A two-year study of carbon dioxide and methane releases in Canada concluded that while

5680-437: The quality of the water and the ecology of the surrounding area. Many reservoirs now support and encourage less formal and less structured recreation such as natural history , bird watching , landscape painting , walking and hiking , and often provide information boards and interpretation material to encourage responsible use. Water falling as rain upstream of the reservoir, together with any groundwater emerging as springs,

5760-526: The reservoir at its operating height of 175.3 metres (575 ft), 29 dikes surround the reservoir basin at various locations. Dikes D-1 to D-4 are located immediately to the north; D-5 to D-14 (the "Forebay dikes") to the south; and D-17 to D-27 (the "Duncan dikes") about 30 miles (48 km) further south. They range in size from D-26B, 82 metres (269 ft) long, to D-20, 6,052 metres (19,856 ft) long. Covering an area of 2,835 square kilometres (1,095 sq mi) – greater in size than Luxembourg –

5840-627: The reservoir prior to, and during, the storm. If done with sufficient lead time, the major storm will not fill the reservoir and areas downstream will not experience damaging flows. Accurate weather forecasts are essential so that dam operators can correctly plan drawdowns prior to a high rainfall event. Dam operators blamed a faulty weather forecast on the 2010–2011 Queensland floods . Examples of highly managed reservoirs are Burrendong Dam in Australia and Bala Lake ( Llyn Tegid ) in North Wales . Bala Lake

5920-574: The temples of Abu Simbel (which were moved before the construction of the Aswan Dam to create Lake Nasser from the Nile in Egypt ), the relocation of the village of Capel Celyn during the construction of Llyn Celyn , and the relocation of Borgo San Pietro of Petrella Salto during the construction of Lake Salto . Construction of a dammed reservoir will usually require the river to be diverted during part of

6000-450: The top of the spillway to 22 metres per second (72 ft/s) at the bottom. The Robert-Bourassa hydroelectric station , formerly named La Grande-2 or LG2, is located underground about 6 kilometres (3.7 mi) downstream of the main dam. With an installed capacity of 5,616 megawatts , it is the largest power station owned by Hydro-Québec, and the largest underground power station in the world. On October 27, 1979, 3,000 people gathered for

6080-493: The use of bank-side storage: here water is taken from the River Thames and River Lee into several large Thames-side reservoirs, such as Queen Mary Reservoir that can be seen along the approach to London Heathrow Airport . Service reservoirs store fully treated potable water close to the point of distribution. Many service reservoirs are constructed as water towers , often as elevated structures on concrete pillars where

6160-640: The vast Robert-Bourassa Reservoir is fed by an upstream catchment of 32,480 square kilometres (12,540 sq mi), plus water diversions from the James Bay Project , the Caniapiscau Reservoir and the EOL ( Eastmain -Opinaca-La Grande) diversion project. About 19.365 cubic kilometres (15,699,000 acre⋅ft) is active or usable storage for power generation, out of a total volume of 61.4 cubic kilometres (49,800,000 acre⋅ft). Because of its great size, it

6240-412: The water, which tends to partition some elements such as manganese and phosphorus into deep, cold anoxic water during the summer months. In the autumn and winter the lake becomes fully mixed again. During drought conditions, it is sometimes necessary to draw down the cold bottom water, and the elevated levels of manganese in particular can cause problems in water treatment plants. In 2005, about 25% of

6320-476: The world's 33,105 large dams (over 15 metres in height) were used for hydroelectricity. The U.S. produces 3% of its electricity from 80,000 dams of all sizes. An initiative is underway to retrofit more dams as a good use of existing infrastructure to provide many smaller communities with a reliable source of energy. A reservoir generating hydroelectricity includes turbines connected to the retained water body by large-diameter pipes. These generating sets may be at

6400-410: Was one of the most extreme cases of workplace sabotage up to that time, workers at the La Grande-2 site used bulldozers to topple electric generators, damage fuel tanks, and set buildings on fire. The project was delayed a year, and the direct cost of the damage estimated at CAD$ 2 million. The causes were not clear, however three factors have been cited: inter-union rivalry, poor working conditions, and

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