In geography , a confluence (also: conflux ) occurs where two or more watercourses join to form a single channel . A confluence can occur in several configurations: at the point where a tributary joins a larger river ( main stem ); or where two streams meet to become the source of a river of a new name (such as the confluence of the Monongahela and Allegheny rivers, forming the Ohio River ); or where two separated channels of a river (forming a river island ) rejoin at the downstream end. The point of confluence where the channel flows into a larger body of water may be called the river mouth .
22-646: Cwmystwyth (also Cwm Ystwyth , Welsh pronunciation: [kʊmˈəstʊɨθ] ; English: "valley of the River Ystwyth " ) is a village in Ceredigion , Wales near Devil's Bridge , and Pont-rhyd-y-groes . The Ordnance Survey calculates Cwmystwyth to be the centre point of Wales ( 52°19′48.791″N 3°45′59.072″W / 52.33021972°N 3.76640889°W / 52.33021972; -3.76640889 ( Centre of Wales ) ; grid reference SN7972871704 ). Discovery of small, oval-shaped stone tools in
44-597: A tripoint . Various examples are found in the list below. A number of major cities, such as Chongqing , St. Louis , and Khartoum , arose at confluences; further examples appear in the list. Within a city, a confluence often forms a visually prominent point, so that confluences are sometimes chosen as the site of prominent public buildings or monuments, as in Koblenz , Lyon , and Winnipeg . Cities also often build parks at confluences, sometimes as projects of municipal improvement, as at Portland and Pittsburgh . In other cases,
66-414: A confluence can be divided into six distinct features which are commonly called confluence flow zones (CFZ). These include The broader field of engineering encompasses a vast assortment of subjects which concern confluences. In hydraulic civil engineering , where two or more underground culverted / artificially buried watercourses intersect, great attention should be paid to the hydrodynamic aspects of
88-619: A confluence is an industrial site, as in Philadelphia or Mannheim . Often a confluence lies in the shared floodplain of the two rivers and nothing is built on it, for example at Manaus , described below. One other way that confluences may be exploited by humans is as sacred places in religions . Rogers suggests that for the ancient peoples of the Iron Age in northwest Europe, watery locations were often sacred, especially sources and confluences. Pre-Christian Slavic peoples chose confluences as
110-482: A corresponding shift in habitat characteristics." Another science relevant to the study of confluences is chemistry , because sometimes the mixing of the waters of two streams triggers a chemical reaction, particularly in a polluted stream. The United States Geological Survey gives an example: "chemical changes occur when a stream contaminated with acid mine drainage combines with a stream with near-neutral pH water; these reactions happen very rapidly and influence
132-443: A variety of sciences. Hydrology studies the characteristic flow patterns of confluences and how they give rise to patterns of erosion, bars, and scour pools. The water flows and their consequences are often studied with mathematical models . Confluences are relevant to the distribution of living organisms (i.e., ecology ) as well; "the general pattern [downstream of confluences] of increasing stream flow and decreasing slopes drives
154-467: Is believed to have inspired a passage in his poem Kubla Khan . The house was demolished in 1955, but the landscape remains today. The River still carries elevated levels of lead, zinc and silver in its water, mostly due to seepage from abandoned mine tailings and discharges from mine adits . At the Frongoch mine near Pont-rhyd-y-groes, Natural Resources Wales has introduced a new technique for reducing
176-735: Is used to describe the meeting of tidal or other non-riverine bodies of water, such as two canals or a canal and a lake. A one-mile (1.6 km) portion of the Industrial Canal in New Orleans accommodates the Gulf Intracoastal Waterway and the Mississippi River-Gulf Outlet Canal ; therefore those three waterways are confluent there. The term confluence can also apply to the process of merging or flowing together of other substance. For example, it may refer to
198-786: The Community Archives Wales project in 2007. Cwmystwyth experiences an oceanic climate ( Köppen climate classification Cfb ) similar to almost all of Wales and the United Kingdom. This translates to a narrow range of temperatures, rainfall in all seasons and low sunshine levels, particularly at upland locations such as inland Wales. The MetOffice maintains a weather station in the village, with online climate records dating back to 1959. Temperatures range from an absolute high of 32.3 °C (90.1 °F) recorded during July 2006, down to an absolute low of −16.7 °C (1.9 °F), recorded during January 1963. During an 'average' year,
220-608: The Afon Diliw, located on the west slopes of Plynlimon on the border of Ceredigion and Powys in the Cambrian Mountains . The Ystwyth flows westwards before its confluence with the Afon Rheidol and the estuary at Aberystwyth to drain into Cardigan Bay . The Ystwyth valley is sparsely populated with villages, namely Ysbyty Ystwyth , Cwm Ystwyth , Pont-rhyd-y-groes , Llanilar and Llanfarian . In previous centuries,
242-470: The Ystwyth valley today. Hafod Uchtryd was a mansion built by Thomas Johnes from 1783, part of it being designed by John Nash . The landscaped gardens were formed by blasting away parts of hills to create vistas. Roadways and bridges were built and hundreds of thousands of trees were planted. The result was a landscape that became famous and attracted many visitors including Samuel Taylor Coleridge , and it
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#1732858132101264-434: The archive includes transcriptions of census data, baptismal registers and log books as a means of interpreting the history of the village. In the long-term, it is hoped that the project will act as a springboard for establishment of a Cwmystwyth History Society which would produce materials relating to the area and eventually to the creation of a heritage centre to showcase the history of the village. Cofnodion Cwmystwyth joined
286-446: The area points to the fact that it has been mined for lead since the time of ancient Britons and during Roman occupation. Documentation of mining activities occurred during the reign of Elizabeth I . She engaged the services of two German miners, then went on to sub-let to Hugh Myddleton. The only significant flat area of the cwm is found before the river reaches maturity near Trawsgoed some 6 miles (9.7 km) further west. Above
308-587: The form of structural bracing. The velocities and hydraulic efficiencies should be meticulously calculated and can be altered by integrating different combinations of geometries, components such a gradients, cascades and an adequate junction angle which is sympathetic to the direction of the watercourse’s flow to minimise turbulent flow, maximise evacuation velocity and to ultimately maximise hydraulic efficiency. Since rivers often serve as political boundaries, confluences sometimes demarcate three abutting political entities, such as nations, states, or provinces, forming
330-617: The pollution. Water is drawn away from the mine in a leat to a wetland area, where biological processes involving the vegetation immobilise much of the pollutants. A similar approach is being used at Cwm Rheidol mine, near Aberystwyth. These remedies are considered important because the area supports a rich variety of wildlife, as well as bringing anglers and tourists to the area. [REDACTED] Media related to Afon Ystwyth at Wikimedia Commons 52°19′50″N 3°53′47″W / 52.33056°N 3.89639°W / 52.33056; -3.89639 Confluence Confluences are studied in
352-448: The sites for fortified triangular temples, where they practiced human sacrifice and other sacred rites. In Hinduism , the confluence of two sacred rivers often is a pilgrimage site for ritual bathing. In Pittsburgh, a number of adherents to Mayanism consider their city's confluence to be sacred. Mississippi basin Atlantic watersheds Pacific watersheds Occasionally, "confluence"
374-613: The subsequent transport of metals downstream of the mixing zone." A natural phenomenon at confluences that is obvious even to casual observers is a difference in color between the two streams; see images in this article for several examples. According to Lynch, "the color of each river is determined by many things: type and amount of vegetation in the watershed, geological properties, dissolved chemicals, sediments and biologic content – usually algae ." Lynch also notes that color differences can persist for miles downstream before they finally blend completely. Hydrodynamic behaviour of flow in
396-401: The system to ensure the longevity and efficiency of the structure. Engineers have to design these systems whilst considering a list of factors that ensure the discharge point is structurally stable as the entrance of the lateral culvert into the main structure may compromise the stability of the structure due to the lack of support at the discharge, this often constitutes additional supports in
418-476: The valley was relatively densely populated due to its mineral wealth. Silver , lead and zinc have been mined in the valley since Roman times, an activity that reached its peak in the 18th century. The largest of the very many mines was Cwm Ystwyth Mine . It is reputed that the average age at death of the miners in Cwm Ystwyth was 32, largely because of acute lead poisoning . There is no active metal mining in
440-634: The village to the east steep slopes rise to the Elenydd moors, above the cwm of the Nant Milwyn, at the head of the hill of Domen Milwyn. Cofnodion Cwmystwyth is a recently established local history group based in Cwmystwyth. The group has 14 regular members of various ages drawn from the Communities First area of Tregaron Uplands, all with a passion for the history of the area. As well as including images,
462-504: The warmest day will likely reach 26.1 °C (79.0 °F) and the coldest night fall to −8.0 °C (17.6 °F). In total just over 3 days should record a temperature of 25.1 °C (77.2 °F) or above, and 59.3 nights should report an air frost. Rainfall, as one might expect for an elevated place in Wales, is high, at nearly 2,000 millimetres (79 in) a year. At least 1 millimetre (0.039 in) will be observed on over 189 days of
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#1732858132101484-408: The year, on average. All averages refer to the period 1971–2000. River Ystwyth The River Ystwyth ( Welsh : Afon Ystwyth ; [ˈəstʊɨ̯θ] ; lit. ' winding river ' ) is a river in Ceredigion , Wales . The length of the main river is 20.5 miles (33.0 km). Its catchment area covers 75 square miles (190 km ). Its source is a number of streams that include
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