A barrage is a type of low-head, diversion dam which consists of a number of large gates that can be opened or closed to control the amount of water passing through. This allows the structure to regulate and stabilize river water elevation upstream for use in irrigation and other systems. The gates are set between flanking piers which are responsible for supporting the water load of the pool created.
The term barrage is borrowed from the French word "barrer" meaning "to bar". [1]
Barrage dams have a series of gates that control the amount of water passing through. A barrage dam can be used to divert water for irrigation needs or limit the amount of water downstream. In most cases, a barrage dam is built near the mouth of the river. The site of dam construction needs to be thoroughly investigated to ensure that the foundation is strong enough to support the dam and has low possibility of failing. [2] When dams are created, they are given a safety rating depending on the type of dam, location, and the possible effects in case of failure. The ratings are from one to five, five having the highest danger rating. The rating of five would be given to dams built with a town or city downstream, which would have higher possibility of injury to people in the case of dam failure. New designs have been made that are able to sustain greater amounts of water. An improved wedge-shaped block technology was developed by Rafael Moran and Miguel Toledo. The new structure is able to withstand severe flooding and uses less materials, reducing the production cost. [3]
Dam construction has several effects on the economy and the environment. Specifically, there are several ways in which the environment can be affected by dam construction. Species richness is usually measured to determine the effect of a dam on the ecosystem surrounding it. [4] To observe the species richness, scientists collect data on the fish and animal populations before and after construction of the dam. With that data, they are able to see how the population size increased or decreased. In some cases, it was found that the species richness was less downstream from a dam compared to further upstream. Inhibiting the volume of water was shown to be detrimental to species diversity and richness. Also, at the entrance of dams, there are fewer nutrients due to the high-water flow reducing the ecosystem's reproduction standard. Along with species richness, plankton diversity can be an indicator of the ecosystem's ability to handle the newly-built dam. It has been shown that dams can have an effect on the migration of fish, leading to less reproduction. [5] There are many small factors that can have a relatively large effect on the river ecosystems, such as species richness, water volume and nutrient levels. Different experiments have been done that looked into each of these individually and were able to determine why some dams cause such effects. While there is substantial evidence, including case studies, that points to dam construction having environmental impact, there are also studies that show less damage than expected. Looking at plankton near some dams has shown that plankton is able to continue to live through changes to its habitat. Changes such as the pH levels near dams have been recorded, and plankton was minimally affected. Other species, however, such as trout, are affected more, due to the physical dam inhibiting their migration and reproduction paths. [4] Barrage dams control the amount of water going through them, leading to differences in the amount of water upstream and downstream from the dam. This discrepancy has different effects on different species native to the area. While there can be reduced flow downstream, there can also be problems upstream. Dams can have buildup of pressure that fish are not accustomed to, and they migrate further upstream, causing part of the river to have reduced population sizes. [4] Although there are environmental effects that come with building new dams, there are also economic benefits from a dam. Without dams, it would be much harder to farm and grow livestock. The irrigation technology that comes with building a dam can exceed the risk factor.
According to the World Commission on Dams, a key difference between a dam and a barrage is that a dam is built for water storage in a reservoir, which raises the level of water significantly. A barrage is built for diverting water, and raises the water level by only a few feet. The latter is generally built on flat terrain across wide, often meandering rivers. [6] Similar distinctions are used in Egypt, where it is noted: "In this system a "dam" is a structure that forms a reservoir for the storage of water during the annual flood period of the Nile in order to supplement the natural flow of the river during the low-water period; a "barrage" merely raises the river or canal level, when necessary, to the height required for adequate flow into the canals that take off above it. [7] Barrages are usually larger than the headworks of irrigation and navigation canals, with which they are associated.
Barrages that are commonly used to dam a tidal lagoon or estuary as a method to capture tidal power from tidal flows are known as tidal barrages.
The English usage of the term barrage originates from the Delta Barrage across the Nile branches north of Cairo, built between 1833 and 1862 by the French Linant de Bellefonds and Eugène Mougel employed by the Egyptian Public Works Department, with assistance from Barthélemy Prosper Enfantin and with the blessing of the Egyptian Viceroy of the Ottoman Empire, Muhammad Ali. When the British, after 1882, had to look after these structures generally referred to as barrages, they adopted the term in their language and continued to use it for similar structures built by themselves across the Nile (Zefta Barrage and Assiut Barrage, both completed in 1902). Since the British in the Egyptian Public Works Department kept close relations to their counterparts in British India, the term barrages made its way to present-day India and Pakistan, as well as to the Middle East and thus generally into English.
A dam is a barrier that stops or restricts the flow of surface water or underground streams. Reservoirs created by dams not only suppress floods but also provide water for activities such as irrigation, human consumption, industrial use, aquaculture, and navigability. Hydropower is often used in conjunction with dams to generate electricity. A dam can also be used to collect or store water which can be evenly distributed between locations. Dams generally serve the primary purpose of retaining water, while other structures such as floodgates or levees are used to manage or prevent water flow into specific land regions.
The Aswan Dam, or more specifically since the 1980s, the Aswan High Dam, is one of the world's largest embankment dams, which was built across the Nile in Aswan, Egypt, between 1960 and 1970. When it was completed, it was the tallest earthen dam in the world, eclipsing the United States' Chatuge Dam. Its significance largely upstaged the previous Aswan Low Dam initially completed in 1902 downstream. Based on the success of the Low Dam, then at its maximum utilization, construction of the High Dam became a key objective of the new regime, the Free Officers movement of 1952; with its ability to better control flooding, provide increased water storage for irrigation and generate hydroelectricity, the dam was seen as pivotal to Egypt's planned industrialization. Like the earlier implementation, the High Dam has had a significant effect on the economy and culture of Egypt.
A weir or low-head dam is a barrier across the width of a river that alters the flow characteristics of water and usually results in a change in the height of the river level. Weirs are also used to control the flow of water for outlets of lakes, ponds, and reservoirs. There are many weir designs, but commonly water flows freely over the top of the weir crest before cascading down to a lower level. There is no single definition as to what constitutes a weir.
Lake Nasser is a vast reservoir in southern Egypt and northern Sudan. It is one of the largest man-made lakes in the world. Before its creation, the project faced opposition from Sudan as it would encroach on land in the northern part of the country, where many Nubian people lived who would have to be resettled. In the end Sudan's land near the area of Lake Nasser was mostly flooded by the lake. The lake has become an important economic resource in Egypt, improving agriculture and touting robust fishing and tourism industries.
Hydroelectricity, or hydroelectric power, is electricity generated from hydropower. Hydropower supplies one sixth of the world's electricity, almost 4,500 TWh in 2020, which is more than all other renewable sources combined and also more than nuclear power. Hydropower can provide large amounts of low-carbon electricity on demand, making it a key element for creating secure and clean electricity supply systems. A hydroelectric power station that has a dam and reservoir is a flexible source, since the amount of electricity produced can be increased or decreased in seconds or minutes in response to varying electricity demand. Once a hydroelectric complex is constructed, it produces no direct waste, and almost always emits considerably less greenhouse gas than fossil fuel-powered energy plants. However, when constructed in lowland rainforest areas, where part of the forest is inundated, substantial amounts of greenhouse gases may be emitted.
Tailwater refers to waters located immediately downstream from a hydraulic structure, such as a dam, spillway, bridge or culvert. Generally measured and reported as the average water depth downstream of a hydraulic structure, tailwater can vary based on the outlet from the structure as well as downstream influences that may restrict or advance the usual flow of water from the structure. The creation of a tailwater will have significant impacts on both the abiotic and biotic conditions of the waterway.
A reservoir is an enlarged lake behind a dam, usually built to store fresh water, often doubling for hydroelectric power generation.
The flooding of the Nile has been an important natural cycle in Nubia and Egypt since ancient times. It is celebrated by Egyptians as an annual holiday for two weeks starting August 15, known as Wafaa El-Nil. It is also celebrated in the Coptic Church by ceremonially throwing a martyr's relic into the river, hence the name, The Martyr's Finger. The flooding of the Nile was poetically described in myth as Isis's tears of sorrow for Osiris when killed by his brother Set.
The Delta Barrage is barrage-type dam that was constructed intermittently beginning in 1833 to its initial completion in 1862. Its purpose was to improve irrigation and navigation along the main Rosetta and Damietta branches of the Nile downstream of the point where they divide north of Cairo, Egypt. At its first operation however, the structure's foundations were found to be of such poor quality that its main irrigation purpose had to be largely abandoned for safety reasons. The barrages have been much maligned as only a romantic river crossing.
As a body of water that crosses numerous international political borders, the Nile river is subject to multiple political interactions. Traditionally it is seen as the world's longest river flowing 6,700 kilometres (4,200 mi) through ten countries in northeastern Africa – Rwanda, Burundi, Democratic Republic of the Congo (DRC), Tanzania, Kenya, Uganda, Ethiopia, South Sudan, Sudan and Egypt with varying climates.
The environmental impact of reservoirs comes under ever-increasing scrutiny as the global demand for water and energy increases and the number and size of reservoirs increases.
The Jawahar Sagar Dam is the third dam in the series of Chambal Valley Projects on the Chambal River, located 29 km upstream of Kota city and 26 km downstream of Rana Pratap Sagar dam. It is a concrete gravity dam, 45 meters high and 393 meters long, generating 60 MW of power with an installed capacity of 3 units of 33 MW. Its construction was completed in 1972. The dam's gross storage capacity is 67.07 million cubic meters. The total catchment area of the dam is 27,195 km2, of which only 1,496 km2 are in Rajasthan. The free catchment area below Rana Pratap Sagar dam is 2,331 km2. The dam is located after the Gandhi Sagar Dam and Rana Pratap Sagar Dam, but before the Kota Barrage.
Sir Murdoch MacDonald was a notable civil engineer and British politician. Born in Inverness, Scotland, MacDonald was educated at the Farraline Park Institution there, and would serve later as the constituency's MP from 1922 until 1950.
A river is a natural flowing watercourse, usually a freshwater stream, flowing on the Earth's land surface or inside caves towards another waterbody at a lower elevation, such as an ocean, sea, bay, lake, wetland, or another river. In some cases, a river flows into the ground or becomes dry at the end of its course without reaching another body of water. Small rivers can be referred to by names such as creek, brook, and rivulet. There are no official definitions for these various generic terms for a watercourse as applied to geographic features, although in some countries or communities, a stream is customarily referred to by one of these names as determined by its size. Many names for small rivers are specific to geographic location; examples are "run" in some parts of the United States, "burn" in Scotland and Northeast England, and "beck" in Northern England. Sometimes a river is defined as being larger than a creek, but not always; in English the language is vague compared to some languages like French, where a fleuve flows into the sea and a rivière is a tributary of another rivière or fleuve.
The Egyptian Department of Public Works was established in the early 19th century, and concentrates mainly on public works relating to irrigation and hydraulic engineering. These irrigation projects have constituted the bulk of work performed by this entity in Egypt. During its almost 200-year history, the Egyptian Department of Public Works employed many notable engineers and constructed massive public works projects throughout the country. It became the most respected engineering entity and was regarded as the 'best school' for civil engineers in modern Egypt. Its history can be broken into three periods:
The Assiut Barrage is a dam on the Nile River in the city of Assiut in Upper Egypt. It was completed in 1903.
The environmental effects of irrigation relate to the changes in quantity and quality of soil and water as a result of irrigation and the subsequent effects on natural and social conditions in river basins and downstream of an irrigation scheme. The effects stem from the altered hydrological conditions caused by the installation and operation of the irrigation scheme.
Water resources management in modern Egypt, is a complex process that involves multiple stakeholders who use water for irrigation, municipal and industrial water supply, hydropower generation and navigation. In addition, the waters of the Nile support aquatic ecosystems that are threatened by abstraction and pollution. Egypt also has substantial fossil groundwater resources in the Western Desert.
Ethiopia is called the water tower of Africa due to its combination of mountainous areas with a comparatively large share of water resources in Africa. Only a fraction of this potential has been harnessed so far, 1% at the beginning of the 21st century. In order to become the powerhouse of Africa, Ethiopia is actively exploiting its water resources by building dams, reservoirs, irrigation and diversion canals and hydropower stations. The benefits of the dams are not only limited to hydropower. Many dams are multi-purpose dams that are also designed to provide water for irrigation, drinking water and flood control. However, hydropower is expected to be the main benefit of the dams.
A tidal barrage is a dam-like structure used to capture the energy from masses of water moving in and out of a bay or river due to tidal forces.
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