In geography, a confluence (also: conflux) occurs where two or more flowing bodies of water join together 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 at Pittsburgh, forming the Ohio); or where two separated channels of a river (forming a river island) rejoin at the downstream end.
Confluences are studied in 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 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 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 a confluence can be divided into six distinct featureswhich are commonly called confluence flow zones (CFZ). These include
Since rivers often serve as political boundaries, confluences sometimes demarcate three abutting political entities, such as nations, states, or provinces, forming 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, 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 employed by humans is as a sacred place in a religion. 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 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.
Occasionally "confluence" is used to describe the meeting of tidal or other non-riverine bodies of water, such as two canals 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.or a canal and a lake. A one-mile (1.6
The term confluence also applies to the merger of the flow of two glaciers.
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The Mississippi River is the second-longest river and chief river of the second-largest drainage system on the North American continent, second only to the Hudson Bay drainage system. From its traditional source of Lake Itasca in northern Minnesota, it flows generally south for 2,320 miles (3,730 km) to the Mississippi River Delta in the Gulf of Mexico. With its many tributaries, the Mississippi's watershed drains all or parts of 32 U.S. states and two Canadian provinces between the Rocky and Appalachian mountains. The main stem is entirely within the United States; the total drainage basin is 1,151,000 sq mi (2,980,000 km2), of which only about one percent is in Canada. The Mississippi ranks as the fourth-longest river and fifteenth-largest river by discharge in the world. The river either borders or passes through the states of Minnesota, Wisconsin, Iowa, Illinois, Missouri, Kentucky, Tennessee, Arkansas, Mississippi, and Louisiana.
The Rhine is one of the major European rivers, which has its sources in Switzerland and flows in a mostly northerly direction through Germany and the Netherlands, emptying into the North Sea. The river begins in the Swiss canton of Graubünden in the southeastern Swiss Alps, forms part of the Swiss-Liechtenstein, Swiss-Austrian, Swiss-German and then the Franco-German border, then flows through the German Rhineland and the Netherlands and eventually empties into the North Sea.
The Illinois River is a principal tributary of the Mississippi River and is approximately 273 miles (439 km) long. Located in the U.S. state of Illinois, the river drains a large section of central Illinois, with a drainage basin of 28,756.6 square miles (74,479 km2). The drainage basin extends into Wisconsin, Indiana, and a very small area of southwestern Michigan.
The Moselle is a river that flows through France, Luxembourg, and Germany. It is a left tributary of the Rhine, which it joins at Koblenz. A small part of Belgium is also drained by the Moselle through the Sauer and the Our.
The Havel is a river in north-eastern Germany, flowing through the German states of Mecklenburg-Vorpommern, Brandenburg, Berlin and Saxony-Anhalt. It is a right tributary of the Elbe and 325 kilometres (202 mi) long. However, the direct distance from its source to its mouth is only 94 kilometres (58 mi).
The source, or headwaters, of a river or stream is the farthest place in that river or stream from its estuary or confluence with another river, as measured along the course of the river.
The Wabash River is a 503-mile-long (810 km) river in Ohio and Indiana, United States, that flows from the headwaters near the middle of Ohio's western border northwest then southwest across northern Indiana turning south along the Illinois border where the southern portion forms the Indiana-Illinois border before flowing into the Ohio River. It is the largest northern tributary of the Ohio River. From the dam near Huntington, Indiana, to its terminus at the Ohio River, the Wabash flows freely for 411 miles (661 km). Its watershed drains most of Indiana. The Tippecanoe River, White River, Embarras River and Little Wabash River are major tributaries. The river's name comes from a Miami Indian word meaning "water over white stones".
The Salt River is a river in the U.S. state of Arizona. It is the largest tributary of the Gila River. The river is about 200 miles (320 km) long. Its drainage basin is about 13,700 square miles (35,000 km2) large. The longest of the Salt River's many tributaries is the 195-mile (314 km) Verde River. The Salt's headwaters tributaries, the Black River and East Fork, increase the river's total length to about 300 miles (480 km). The name Salt River comes from the fact that the river flows over large salt deposits shortly after the merging of the White and Black Rivers.
The Feather River is the principal tributary of the Sacramento River, in the Sacramento Valley of Northern California. The river's main stem is about 73 miles (117 km) long. Its length to its most distant headwater tributary is just over 210 miles (340 km). The main stem Feather River begins in Lake Oroville, where its four long tributary forks join together—the South Fork, Middle Fork, North Fork, and West Branch Feather Rivers. These and other tributaries drain part of the northern Sierra Nevada, and the extreme southern Cascades, as well as a small portion of the Sacramento Valley. The total drainage basin is about 6,200 square miles (16,000 km2), with approximately 3,604 square miles (9,330 km2) above Lake Oroville.
The Boise River is a 102-mile-long (164 km) tributary of the Snake River in the northwestern United States. It drains a rugged portion of the Sawtooth Range in southwestern Idaho northeast of Boise, as well as part of the western Snake River Plain. The watershed encompasses approximately 4,100 square miles (11,000 km2) of highly diverse habitats, including alpine canyons, forest, rangeland, agricultural lands, and urban areas.
A drainage divide, water divide, divide, ridgeline, watershed, water parting or height of land is elevated terrain that separates neighboring drainage basins. On rugged land, the divide lies along topographical ridges, and may be in the form of a single range of hills or mountains, known as a dividing range. On flat terrain, especially where the ground is marshy, the divide may be harder to discern.
The Black Fork is a principal tributary of the Cheat River in the Allegheny Mountains of eastern West Virginia, USA. It is a short stream, about four miles (6 km) in length, formed by the confluence of two other streams not far above its mouth. It was traditionally considered one of the five Forks of Cheat.
The main European watershed is the drainage divide ("watershed") which separates the basins of the rivers that empty into the Atlantic Ocean, the North Sea and the Baltic Sea from those that feed the Mediterranean Sea, the Adriatic Sea and the Black Sea. It stretches from the tip of the Iberian Peninsula at Gibraltar in the southwest to the endorheic basin of the Caspian Sea in Russia in the northeast.
The Chicago Portage is a water gap, and in the past a sometime wind-gap portage, connecting the watersheds (BrE: drainage basins) and the navigable waterways of the Mississippi River and the Great Lakes. It cuts through the Valparaiso and Tinley Moraines, crossing the Saint Lawrence River Divide that separates the Great Lakes and Gulf of St. Lawrence watersheds from the Gulf of Mexico watershed, making it one of the most strategic points in the interior of the North American continent. The saddle point of the gap is within the city of Chicago, and the Chicago Portage is a reason Chicago exists and developed to become an important city, ranking 7th in the world in the 2014 Global Cities Index. The official flag of the city of Chicago includes four red stars symbolizing city history, separating two blue stripes symbolizing the waters that meet at the city.
Side valleys and tributary valleys are valleys whose brooks or rivers flow into greater ones.
A stream is a body of water with surface water flowing within the bed and banks of a channel. The flow of a stream is controlled by three inputs - surface water, subsurface water and groundwater. The surface and subsurface water are highly variable between periods of rainfall. Groundwater, on the other hand, has a relatively constant input and is controlled more by long-term patterns of precipitation. The stream encompasses surface, subsurface and groundwater fluxes that respond to geological, geomorphological, hydrological and biotic controls.
A river is a natural flowing watercourse, usually freshwater, flowing towards an ocean, sea, lake or another river. In some cases a river flows into the ground and becomes dry at the end of its course without reaching another body of water. Small rivers can be referred to using names such as stream, creek, brook, rivulet, and rill. There are no official definitions for the generic term river as applied to geographic features, although in some countries or communities a stream is defined 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: the language is vague.
The Anyangcheon is a river in Gyeonggi-do and Seoul, South Korea. It has its source on the slopes of Mount Gwanggyo in the city of Uiwang and flows north, through the city of Gunpo, where a major cleanup operation saw several species of birds return to the area in 2005. Here, though, the water table remains depleted. The river then flows through Anyang City, where it is met by its major tributary, the Hakuicheon stream. From here, it loops around to the west before continuing north to the border with Gwangmyeong City. As the river passes to the west of Mount Gwanak, it forms the border between Gwangmyeong and Seoul, where it is lined on the Gwangmyeong side with rape fields and cherry blossom trees. After the stream is joined near Guil Station from the west by the Mokgamcheon stream, which forms another border between Gwangmyeong and Seoul, it is then totally within the capital. Here, it is also joined from the east by the Dorimcheon and passes through a conservation zone for migratory birds which was established after a 2005 cleanup operation, whereafter it joins the Han. Most of the length of the river has a path alongside providing easy access, the only parts without this lying in Uiwang. Seoul City Council has embarked on a programme of exclusive cycle path creation alongside its waterways, including the Anyangcheon, to be completed in 2010.
Coyote Creek is a principal tributary of the San Gabriel River in northwest Orange County, southeast Los Angeles County, and southwest Riverside County, California. It drains a land area of roughly 41.3 square miles (107 km2) covering five major cities, including Brea, Buena Park, Fullerton, La Habra, and La Palma. Some major tributaries of the creek in the highly urbanized watershed include Brea Creek, Fullerton Creek, and Carbon Creek. The mostly flat creek basin is separated by a series of low mountains, and is bounded by several small mountain ranges, including the Chino Hills, Puente Hills and West Coyote Hills.
The Oder is a river in Central Europe and Poland's third-longest river after the Vistula and Warta. It rises in the Czech Republic and flows 742 kilometres (461 mi) through western Poland, later forming 187 kilometres (116 mi) of the border between Poland and Germany as part of the Oder–Neisse line. The river ultimately flows into the Szczecin Lagoon north of Szczecin and then into three branches that empty into the Bay of Pomerania of the Baltic Sea.