Mountaintop removal mining
Mountaintop removal mining known as mountaintop mining, is a form of surface mining at the summit or summit ridge of a mountain. Coal seams are extracted from a mountain by removing the overburden, above the seams; this method of coal mining is conducted in the Appalachian Mountains in the eastern United States. Explosives are used to remove up to 400 vertical feet of mountain to expose underlying coal seams. Excess rock and soil is dumped into nearby valleys, in what are called "holler fills" or "valley fills". Less expensive to execute and requiring fewer employees, mountaintop removal mining began in Appalachia in the 1970s as an extension of conventional strip mining techniques, it is occurring in Kentucky, West Virginia and Tennessee. The practice of mountaintop removal mining has been controversial; the coal industry cites economic benefits and asserts that mountaintop removal is safer than underground mining. Published scientific studies have found that mountaintop mining has serious environmental impacts that mitigation practices cannot address.
A high potential for human health impacts has been reported. Mountaintop removal mining known as mountaintop mining, is a form of surface mining that involves the topographical alteration and/or removal of a summit, hill, or ridge to access buried coal seams; the MTR process involves the removal of coal seams by first removing the overburden lying atop them, exposing the seams from above. This method differs from more traditional underground mining, where a narrow shaft is dug which allows miners to collect seams using various underground methods, while leaving the vast majority of the overburden undisturbed; the overburden from MTR is either placed back on the ridge, attempting to reflect the approximate original contour of the mountain, and/or it is moved into neighboring valleys. Excess rock and soil containing mining byproducts are disposed into nearby valleys, in what are called "holler fills" or "valley fills". MTR in the United States is most associated with the extraction of coal in the Appalachian Mountains, where the United States Environmental Protection Agency estimates that 2,200 square miles of Appalachian forests will be cleared for MTR sites by the year 2012.
Sites range from Ohio to Virginia. It occurs most in West Virginia and Eastern Kentucky, the top two coal-producing states in Appalachia, with each state using 1,000 tonnes of explosives per day for surface mining. At current rates, MTR in the U. S. will mine over 1.4 million acres by 2010, an amount of land area that exceeds that of the state of Delaware. Mountaintop removal has been practiced since the 1960s. Increased demand for coal in the United States, sparked by the 1973 and 1979 petroleum crises, created incentives for a more economical form of coal mining than the traditional underground mining methods involving hundreds of workers, triggering the first widespread use of MTR, its prevalence expanded further in the 1990s to retrieve low-sulfur coal, a cleaner-burning form, which became desirable as a result of amendments to the U. S. Clean Air Act that tightened emissions limits on high-sulfur coal processing. Land is deforested prior to mining operations and the resultant lumber is either sold or burned.
According to the Surface Mining Control and Reclamation Act of 1977, the topsoil is supposed to be removed and set aside for reclamation. However, coal companies are granted waivers and instead reclaim the mountain with "topsoil substitute"; the waivers are granted if adequate amounts of topsoil are not present on the rocky ridge top. Once the area is cleared, miners use explosives to blast away the overburden, the rock and subsoil, to expose coal seams beneath; the overburden is moved by various mechanical means to areas of the ridge mined. These areas are the most economical area of storage as they are located close to the active pit of exposed coal. If the ridge topography is too steep to adequately handle the amount of spoil produced additional storage is used in a nearby valley or hollow, creating what is known as a valley fill or hollow fill. Any streams in a valley are buried by the overburden. A front-end loader or excavator removes the coal, where it is transported to a processing plant.
Once coal removal is completed, the mining operators back stack overburden from the next area to be mined into the now empty pit. After backstacking and grading of overburden has been completed, topsoil is layered over the overburden layer. Next, grass seed is spread in a mixture of seed and mulch made from recycled newspaper. Depending on surface land owner wishes the land will be further reclaimed by adding trees if the pre-approved post-mining land use is forest land or wildlife habitat. If the land owner has requested other post-mining land uses the land can be reclaimed to be used as pasture land, economic development or other uses specified in SMCRA; because coal exists in multiple geologically stratified seams, miners can repeat the blasting process to mine over a dozen seams on a single mountain, increasing the mine depth each time. This can result in a vertical descent of hundreds of extra feet into the earth; as of 2015 one third of the electricity generated in the United States is produced by coal-fired power plants.
MTR accounted for less than 5% of U. S. coal production as of 2001. In some regions, the percentage is higher, for example, MTR provided 30% of the coal mined in West Virginia in 2006. In the U. S. the prevalent method of coal acquisition was underground mining, labor-intensive. In MTR, through the use of
National Park Service
The National Park Service is an agency of the United States federal government that manages all national parks, many national monuments, other conservation and historical properties with various title designations. It was created on August 25, 1916, by Congress through the National Park Service Organic Act and is an agency of the United States Department of the Interior; the NPS is charged with a dual role of preserving the ecological and historical integrity of the places entrusted to its management, while making them available and accessible for public use and enjoyment. As of 2018, the NPS employs 27,000 employees who oversee 419 units, of which 61 are designated national parks. National parks and national monuments in the United States were individually managed under the auspices of the Department of the Interior; the movement for an independent agency to oversee these federal lands was spearheaded by business magnate and conservationist Stephen Mather, as well as J. Horace McFarland. With the help of journalist Robert Sterling Yard, Mather ran a publicity campaign for the Department of the Interior.
They wrote numerous articles that praised the scenic and historic qualities of the parks and their possibilities for educational and recreational benefits. This campaign resulted in the creation of a National Park Service. On August 25, 1916, President Woodrow Wilson signed a bill that mandated the agency "to conserve the scenery and the natural and historic objects and wildlife therein, to provide for the enjoyment of the same in such manner and by such means as will leave them unimpaired for the enjoyment of future generations." Mather became the first director of the newly formed NPS. On March 3, 1933, President Herbert Hoover signed the Reorganization Act of 1933; the act would allow the President to reorganize the executive branch of the United States government. It wasn't until that summer when the new President, Franklin D. Roosevelt, made use of this power. Deputy Director Horace M. Albright had suggested to President Roosevelt that the historic sites from the American Civil War should be managed by the National Park Service, rather than the War Department.
President Roosevelt issued two Executive orders to make it happen. These two executive orders not only transferred to the National Park Service all the War Department historic sites, but the national monuments managed by the Department of Agriculture and the parks in and around the capital, run by an independent office. In 1951, Conrad Wirth became director of the National Park Service and went to work on bringing park facilities up to the standards that the public expected; the demand for parks after the end of the World War II had left the parks overburdened with demands that could not be met. In 1952, with the support of President Dwight D. Eisenhower, he began Mission 66, a ten-year effort to upgrade and expand park facilities for the 50th anniversary of the Park Service. New parks were added to preserve unique resources and existing park facilities were upgraded and expanded. In 1966, as the Park Service turned 50 years old, emphasis began to turn from just saving great and wonderful scenery and unique natural features to making parks accessible to the public.
Director George Hartzog began the process with the creation of the National Lakeshores and National Recreation Areas. Since its inception in 1916, the National Park Service has managed each of the United States' national parks, which have grown in number over the years to 60. Yellowstone National Park was the first national park in the United States. In 1872, there was no state government to manage it, so the federal government assumed direct control. Yosemite National Park began as a state park. Yosemite was returned to federal ownership. At first, each national park was managed independently, with varying degrees of success. In Yellowstone, the civilian staff was replaced by the U. S. Army in 1886. Due to the irregularities in managing these national treasures, Stephen Mather petitioned the federal government to improve the situation. In response, Secretary of the Interior Franklin K. Lane challenged him to lobby for creating a new agency, the National Park Service, to manage all national parks and some national monuments.
Mather was successful with the ratification of the National Park Service Organic Act in 1916. The agency was given authority over other protected areas, many with varying designations as Congress created them; the National Park System includes. The title or designation of a unit need not include the term park; the System as a whole is considered to be a national treasure of the United States, some of the more famous national parks and monuments are sometimes referred to metaphorically as "crown jewels". The system encompasses 84.4 million acres, of which more than 4.3 million acres remain in private ownership. The largest unit is Wrangell-St. Elias National Park and Preserve, Alaska. At 13,200,000 acres, it is over 16 percent of the entire system; the smallest unit in the system is Thaddeus Kosciuszko National Memorial, Pennsylvania, at 0.02 acre. In addition to administering its units and other properties, the National Park Service provides technical and financial assistance to several "affiliated areas" authorized by Congress.
The largest affiliated area is New Jersey Pinelands National Reserve at 1,164,025 acres. The smallest is Benjamin Franklin National Memorial at less than 0.01 acres. Although all units of the Nat
Advocacy is an activity by an individual or group that aims to influence decisions within political and social systems and institutions. Advocacy can include many activities that a person or organization undertakes including media campaigns, public speaking and publishing research or conducting exit poll or the filing of an amicus brief. Lobbying is a form of advocacy where a direct approach is made to legislators on an issue which plays a significant role in modern politics. Research has started to address how advocacy groups in the United States and Canada are using social media to facilitate civic engagement and collective action. An advocate is someone. There are several forms of advocacy, each representing a different approach in a way to initiate changes in the society. One of the most popular forms is social justice advocacy; the initial definition does not encompass the notions of power relations, people's participation and a vision of a just society as promoted by social justice advocates.
For them, advocacy represents the series of actions taken and issues highlighted to change the “what is” into a “what should be”, considering that this “what should be” is a more decent and a more just society. Those actions, which vary with the political and social environment in which they are conducted, have several points in common. They: Question the way policy is administered Participate in the agenda-setting as they raise significant issues Target political systems "because those systems are not responding to people's needs" Are inclusive and engaging Propose policy solutions Open up space for public argumentationOther forms of advocacy include: Budget advocacy: another aspect of advocacy that ensures proactive engagement of Civil Society Organizations with the government budget to make the government more accountable to the people and promote transparency. Budget advocacy enables citizens and social action groups to compel the government to be more alert to the needs and aspirations of people in general and the deprived sections of the community.
Bureaucratic advocacy: people considered "experts" have more chance to succeed at presenting their issues to decision-makers. They use bureaucratic advocacy to influence the agenda. Express versus issue advocacy: These two types of advocacy when grouped together refers to a debate in the United States whether a group is expressly making their desire known that voters should cast ballots in a particular way, or whether a group has a long-term issue that isn't campaign and election season specific. Health advocacy: supports and promotes patients' health care rights as well as enhance community health and policy initiatives that focus on the availability and quality of care. Ideological advocacy: in this approach, groups fight, sometimes during protests, to advance their ideas in the decision-making circles. Interest-group advocacy: lobbying is the main tool used by interest groups doing mass advocacy, it is a form of action that does not always succeed at influencing political decision-makers as it requires resources and organization to be effective.
Legislative advocacy: the "reliance on the state or federal legislative process" as part of a strategy to create change. Mass advocacy: any type of action taken by large groups Media advocacy: "the strategic use of the mass media as a resource to advance a social or public policy initiative". In Canada, for example, the Manitoba Public Insurance campaigns illustrate how media advocacy was used to fight alcohol and tobacco-related health issues. We can consider the role of health advocacy and the media in “the enactment of municipal smoking bylaws in Canada between 1970 and 1995.” Special education advocacy: advocacy with a "specific focus on the educational rights of students with disabilities."Different contexts in which advocacy is used: In a legal/law context: An "advocate" is the title of a specific person, authorized/appointed in some way to speak on behalf of a person in a legal process. In a political context: An "advocacy group" is an organized collection of people who seek to influence political decisions and policy, without seeking election to public office.
In a social care context: Both terms are used in the UK in the context of a network of interconnected organisations and projects which seek to benefit people who are in difficulty. In the context of inclusion: Citizen Advocacy organisations seek to cause benefit by reconnecting people who have become isolated, their practice was defined in two key documents: CAPE, Learning from Citizen Advocacy Programs. Advocacy in all its forms seeks to ensure that people those who are most vulnerable in society, are able to: Have their voice heard on issues that are important to them Defend and safeguard their rights Have their views and wishes genuinely considered when decisions are being made about their livesAdvocacy is a process of supporting and enabling people to: Express their views and concerns Access information and services Defend and promote their rights and responsibilities Explore choices and options Groups involved in advocacy work have been using the Internet to accomplish organizational goals.
It has been argued that the Internet helps to increase the speed and effectiveness of advocacy-related communication as well as mobilization efforts, suggesting that social media are beneficial to the advocacy community. People advocate for a large variety of topics; some of these are clear-cut social issues that are univers
A fish ladder known as a fishway, fish pass or fish steps, is a structure on or around artificial and natural barriers to facilitate diadromous fishes' natural migration. Most fishways enable fish to pass around the barriers by swimming and leaping up a series of low steps into the waters on the other side; the velocity of water falling over the steps has to be great enough to attract the fish to the ladder, but it cannot be so great that it washes fish back downstream or exhausts them to the point of inability to continue their journey upriver. Written reports of rough fishways date to 17th-century France, where bundles of branches were used to create steps in steep channels to bypass obstructions. A version was patented in 1837 by Richard McFarlan of Bathurst, New Brunswick, who designed a fishway to bypass a dam at his water-powered lumber mill. In 1852–1854, the Ballisodare Fish Pass was built in County Sligo in Ireland to draw salmon into a river that had not supported a fishery. In 1880, the first fish ladder was built in United States, on the Pawtuxet Falls Dam.
The ladder was removed in 1924, when the City of Providence replaced the wood dam with a concrete one. Concrete ladders are not always an improvement – the electric field-sensitive organs of the paddlefish are overloaded in the proximity of the rebar and other metal used in concrete construction, preventing them from gaining access to their spawning grounds and contributing to a catastrophic decline in their numbers; as the Industrial Age advanced and other river obstructions became larger and more common, leading to the need for effective fish by-passes. There are six main types of fishways: Pool and weir Baffle fishway Fish elevator Rock-ramp fishway Vertical-slot fish passage Fish siphonA pool and weir is one of the oldest styles of fish ladders, it uses a series of small dams and pools of regular length to create a long, sloping channel for fish to travel around the obstruction. The channel acts as a fixed lock to step down the water level. A baffle fishway uses a series of symmetrical close-spaced baffles in a channel to redirect the flow of water, allowing fish to swim around the barrier.
Baffle fishways need not have resting areas, although pools can be included to provide a resting area or to reduce the velocity of the flow. Such fishways can be built with switchbacks to minimize the space needed for their construction. Baffles come in variety of designs; the original design for a Denil fishway was developed in 1909 by G. Denil; the Alaskan Steeppass, for example, is a modular prefabricated Denil-fishway variant designed for remote areas of Alaska. Baffles have been installed by Project Maitai in several waterways in Nelson, New Zealand, to improve fish passage as part of general environmental restoration. A fish elevator or fish lift, as its name implies, breaks with the ladder design by providing a sort of elevator to carry fish over a barrier, it is well suited to tall barriers. With a fish elevator, fish swim into a collection area at the base of the obstruction; when enough fish accumulate in the collection area, they are nudged into a hopper that carries them into a flume that empties into the river above the barrier.
On the Connecticut River, for example, two fish elevators lift up to 500 fish at a time, 52 feet, to clear the Holyoke Dam. In 2013, the elevator carried over 400,000 fish. A rock-ramp fishway uses large rocks and timbers to create pools and small falls that mimic natural structures; because of the length of the channel needed for the ladder, such structures are most appropriate for short barriers. They have a significant advantage. A vertical-slot fish passage is similar to a pool-and-weir system, except that each "dam" has a narrow slot in it near the channel wall; this allows fish to swim upstream without leaping over an obstacle. Vertical-slot fish passages tend to handle reasonably well the seasonal fluctuation in water levels on each side of the barrier. Recent studies suggest that navigation locks have a potential to be operated as vertical slot fishways to provide increased access for a range of biota, including poor swimmers. A fish siphon allows the pass to be installed parallel to a water course and can be used to link two watercourses.
The pass utilises a syphon effect to regulate its flow. This style is favoured to aid flood defence. Fish ladders have a mixed record of effectiveness, they vary in effectiveness for different types of species, with one study showing that only three percent of American Shad make it through all the fish ladders on the way to their spawning ground. Effectiveness depends on the fish species' swimming ability, how the fish moves up and downstream. A fish passage, designed to allow fish to pass upstream may not allow passage downstream, for instance. Fish passages do not always work. In practice a challenge is matching swimming performance data to hydrodynamic measurements. Swim tests use the same protocol and the output is either a single-point measurement or a bulk velocity. In contrast and numerical modelling of fluid flow deliver a detailed flow map, with a fine spatial and temporal resolution. Regulatory agencies face a difficult task to match hydrodynamic measurements and swimming performance data.
During the last three decades, the ecological impact of culverts on natural streams and rivers has been recognised. While the culvert discharge capacity derives from hydrological and hydraulic eng
Canada is a country in the northern part of North America. Its ten provinces and three territories extend from the Atlantic to the Pacific and northward into the Arctic Ocean, covering 9.98 million square kilometres, making it the world's second-largest country by total area. Canada's southern border with the United States is the world's longest bi-national land border, its capital is Ottawa, its three largest metropolitan areas are Toronto and Vancouver. As a whole, Canada is sparsely populated, the majority of its land area being dominated by forest and tundra, its population is urbanized, with over 80 percent of its inhabitants concentrated in large and medium-sized cities, many near the southern border. Canada's climate varies across its vast area, ranging from arctic weather in the north, to hot summers in the southern regions, with four distinct seasons. Various indigenous peoples have inhabited what is now Canada for thousands of years prior to European colonization. Beginning in the 16th century and French expeditions explored, settled, along the Atlantic coast.
As a consequence of various armed conflicts, France ceded nearly all of its colonies in North America in 1763. In 1867, with the union of three British North American colonies through Confederation, Canada was formed as a federal dominion of four provinces; this began an accretion of provinces and territories and a process of increasing autonomy from the United Kingdom. This widening autonomy was highlighted by the Statute of Westminster of 1931 and culminated in the Canada Act of 1982, which severed the vestiges of legal dependence on the British parliament. Canada is a parliamentary democracy and a constitutional monarchy in the Westminster tradition, with Elizabeth II as its queen and a prime minister who serves as the chair of the federal cabinet and head of government; the country is a realm within the Commonwealth of Nations, a member of the Francophonie and bilingual at the federal level. It ranks among the highest in international measurements of government transparency, civil liberties, quality of life, economic freedom, education.
It is one of the world's most ethnically diverse and multicultural nations, the product of large-scale immigration from many other countries. Canada's long and complex relationship with the United States has had a significant impact on its economy and culture. A developed country, Canada has the sixteenth-highest nominal per capita income globally as well as the twelfth-highest ranking in the Human Development Index, its advanced economy is the tenth-largest in the world, relying chiefly upon its abundant natural resources and well-developed international trade networks. Canada is part of several major international and intergovernmental institutions or groupings including the United Nations, the North Atlantic Treaty Organization, the G7, the Group of Ten, the G20, the North American Free Trade Agreement and the Asia-Pacific Economic Cooperation forum. While a variety of theories have been postulated for the etymological origins of Canada, the name is now accepted as coming from the St. Lawrence Iroquoian word kanata, meaning "village" or "settlement".
In 1535, indigenous inhabitants of the present-day Quebec City region used the word to direct French explorer Jacques Cartier to the village of Stadacona. Cartier used the word Canada to refer not only to that particular village but to the entire area subject to Donnacona. From the 16th to the early 18th century "Canada" referred to the part of New France that lay along the Saint Lawrence River. In 1791, the area became two British colonies called Upper Canada and Lower Canada collectively named the Canadas. Upon Confederation in 1867, Canada was adopted as the legal name for the new country at the London Conference, the word Dominion was conferred as the country's title. By the 1950s, the term Dominion of Canada was no longer used by the United Kingdom, which considered Canada a "Realm of the Commonwealth"; the government of Louis St. Laurent ended the practice of using'Dominion' in the Statutes of Canada in 1951. In 1982, the passage of the Canada Act, bringing the Constitution of Canada under Canadian control, referred only to Canada, that year the name of the national holiday was changed from Dominion Day to Canada Day.
The term Dominion was used to distinguish the federal government from the provinces, though after the Second World War the term federal had replaced dominion. Indigenous peoples in present-day Canada include the First Nations, Métis, the last being a mixed-blood people who originated in the mid-17th century when First Nations and Inuit people married European settlers; the term "Aboriginal" as a collective noun is a specific term of art used in some legal documents, including the Constitution Act 1982. The first inhabitants of North America are hypothesized to have migrated from Siberia by way of the Bering land bridge and arrived at least 14,000 years ago; the Paleo-Indian archeological sites at Old Crow Flats and Bluefish Caves are two of the oldest sites of human habitation in Canada. The characteristics of Canadian indigenous societies included permanent settlements, complex societal hierarchies, trading networks; some of these cultures had collapsed by the time European explorers arrived in the late 15th and early 16th centuries and have only been discovered through archeological investigations.
The indigenous population at the time of the first European settlements is estimated to have been between 200,000
Robert Sterling Yard
Robert Sterling Yard was an American writer and wilderness activist. Born in Haverstraw, New York, Yard graduated from Princeton University and spent the first twenty years of his career in the editing and publishing business. In 1915, he was recruited by his friend Stephen Mather to help publicize the need for an independent national park agency, their numerous publications were part of a movement that resulted in legislative support for a National Park Service in 1916. Yard served as head of the National Parks Educational Committee for several years after its conception, but tension within the NPS led him to concentrate on non-government initiatives, he became executive secretary of the National Parks Association in 1919. Yard worked to promote the national parks as well as educate Americans about their use. Creating high standards based on aesthetic ideals for park selection, he opposed commercialism and industrialization of what he called "America's masterpieces"; these standards subsequently caused discord with his peers.
After helping to establish a relationship between the NPA and the United States Forest Service, Yard became involved in the protection of wilderness areas. In 1935, he became one of the eight founding members of The Wilderness Society and acted as its first president from 1937 until his death eight years later. Yard is now considered an important figure in the modern wilderness movement. Robert Sterling Yard was born in 1861 in New York to Robert Boyd and Sarah Yard. After attending the Freehold Institute in New Jersey, he graduated from Princeton University in 1883. Known throughout his life as "Bob", he became a prominent member of Princeton's Alumni Association, founded the Montclair Princeton Alumni Association. In 1895, he married Mary Belle Moffat. During the 1880s and 1890s, Yard worked as a journalist for the New York Sun and the New York Herald, he served in the publishing business from 1900 to 1915, variously as editor-in-chief of The Century Magazine and Sunday editor of the New York Herald.
After serving as editor of Charles Scribner's Sons' the Book Buyer, Yard helped launch the publishing firm of Moffat and Company. He served as vice editor-in-chief of the firm. In 1915, Yard was invited to Washington, D. C. by his friend Stephen Mather, who had started working on national parks as assistant to the Secretary of Interior. Yard and Mather became friends. Mather, who wanted someone to help publicize the need for an independent agency to oversee the national parks movement paid Yard's salary from his independent income; the United States had authorized 14 parks and 22 monuments over the previous forty years, but there was no single agency to provide unified management of the resources. In addition, some resources were managed by political appointees without professional qualifications. Together Mather and Yard ran a national parks publicity campaign for the Department of the Interior, writing numerous articles that praised the scenic qualities of the parks and their possibilities for educational and recreational benefits.
The unprecedented press coverage persuaded influential Americans about the importance of national parks, encouraged Congress to create an independent parks agency. Although Yard was not an outdoorsman like most advocates of a national park service, he felt a connection to the cause, became invested in its success. At the National Park Conference in March 1915, he stated, "I, the treader of dusty city streets, boldly claim common kinship with you of the plains, the mountains, the glaciers." He gathered data regarding popular American tourist destinations, such as Switzerland, Germany and Canada, together with reasons why people visited certain areas. One of his most recognized and passionate articles of the time, entitled "Making a Business of Scenery", appeared in The Nation's Business in June 1916: We want our national parks developed. We want trails like Switzerland's. We want hotels of all prices from lowest to highest. We want comfortable public camps in sufficient abundance to meet all demands.
We want lodges and chalets at convenient intervals commanding the scenic possibilities of all our parks. We want the cheapest accommodations for pedestrians and motorists. We want convenient transportation at reasonable rates. We want adequate supplies for camping out at lowest prices. We want good fishing. We want our wild animal life developed. We want special facilities for nature study. Yard's most successful publicity initiative during this time was the National Parks Portfolio, a collection of nine pamphlets that—through photographs interspersed with text lauding the scenic grandeur of the nation's major parks—connected the parks with a sense of national identity to make visitation an imperative of American citizenship. Yard and Mather distributed this publication to a selected list of prominent Americans, including every member of Congress; that same year, Yard wrote and published Glimpses of Our National Parks, followed in 1917 by a similar volume titled The Top of the Continent. The latter volume, subtitled A Cheerful Journey through Our National Parks and geared toward a younger audience, became a bestseller.
Yard and Mather's publicity and lobbying resulted in the creation of the National Park Service.
A dam is a barrier that stops or restricts the flow of water or underground streams. Reservoirs created by dams not only suppress floods but provide water for activities such as irrigation, human consumption, industrial use and navigability. Hydropower is used in conjunction with dams to generate electricity. A dam can be used to collect water or for storage of water which can be evenly distributed between locations. Dams 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 earliest known dam is the Jawa Dam in Jordan, dating to 3,000 BC. The word dam can be traced back to Middle English, before that, from Middle Dutch, as seen in the names of many old cities; the first known appearance of dam occurs in 1165. However, there is one village, mentioned in 1120; the word seems to be related to the Greek word taphos, meaning "grave" or "grave hill". So the word should be understood as "dike from dug out earth".
The names of more than 40 places from the Middle Dutch era such as Amsterdam and Rotterdam bear testimony to the use of the word in Middle Dutch at that time. Early dam building took place in the Middle East. Dams were used to control the water level, for Mesopotamia's weather affected the Tigris and Euphrates rivers; the earliest known dam is the Jawa Dam in Jordan, 100 kilometres northeast of the capital Amman. This gravity dam featured an 9-metre-high and 1 m-wide stone wall, supported by a 50 m-wide earth rampart; the structure is dated to 3000 BC. The Ancient Egyptian Sadd-el-Kafara Dam at Wadi Al-Garawi, located about 25 km south of Cairo, was 102 m long at its base and 87 m wide; the structure was built around 2800 or 2600 BC as a diversion dam for flood control, but was destroyed by heavy rain during construction or shortly afterwards. During the Twelfth Dynasty in the 19th century BC, the Pharaohs Senosert III, Amenemhat III and Amenemhat IV dug a canal 16 km long linking the Fayum Depression to the Nile in Middle Egypt.
Two dams called Ha-Uar running east-west were built to retain water during the annual flood and release it to surrounding lands. The lake called "Mer-wer" or Lake Moeris is known today as Birket Qarun. By the mid-late third millennium BC, an intricate water-management system within Dholavira in modern-day India was built; the system included 16 reservoirs and various channels for collecting water and storing it. One of the engineering wonders of the ancient world was the Great Dam of Marib in Yemen. Initiated somewhere between 1750 and 1700 BC, it was made of packed earth – triangular in cross section, 580 m in length and 4 m high – running between two groups of rocks on either side, to which it was linked by substantial stonework. Repairs were carried out during various periods, most important around 750 BC, 250 years the dam height was increased to 7 m. After the end of the Kingdom of Saba, the dam fell under the control of the Ḥimyarites who undertook further improvements, creating a structure 14 m high, with five spillway channels, two masonry-reinforced sluices, a settling pond, a 1,000 m canal to a distribution tank.
These extensive works were not finalized until 325 AD and allowed the irrigation of 25,000 acres. Eflatun Pınar is a Hittite spring temple near Konya, Turkey, it is thought to be from the time of the Hittite empire between the 15th and 13th century BC. The Kallanai is constructed of unhewn stone, over 300 m long, 4.5 m high and 20 m wide, across the main stream of the Kaveri river in Tamil Nadu, South India. The basic structure dates to the 2nd century AD and is considered one of the oldest water-diversion or water-regulator structures in the world, still in use; the purpose of the dam was to divert the waters of the Kaveri across the fertile delta region for irrigation via canals. Du Jiang Yan is the oldest surviving irrigation system in China that included a dam that directed waterflow, it was finished in 251 BC. A large earthen dam, made by Sunshu Ao, the prime minister of Chu, flooded a valley in modern-day northern Anhui province that created an enormous irrigation reservoir, a reservoir, still present today.
Roman dam construction was characterized by "the Romans' ability to plan and organize engineering construction on a grand scale." Roman planners introduced the then-novel concept of large reservoir dams which could secure a permanent water supply for urban settlements over the dry season. Their pioneering use of water-proof hydraulic mortar and Roman concrete allowed for much larger dam structures than built, such as the Lake Homs Dam the largest water barrier to that date, the Harbaqa Dam, both in Roman Syria; the highest Roman dam was the Subiaco Dam near Rome. Roman engineers made routine use of ancient standard designs like embankment dams and masonry gravity dams. Apart from that, they displayed a high degree of inventiveness, introducing most of the other basic dam designs, unknown until then; these include arch-gravity dams, arch dams, buttress dams and multiple arch buttress dams, all of which were known and employed by the 2nd century AD. Roman workforces were the first to build dam bridges, such as the Bridge of Valerian in Iran