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48-818: The Dreisam begins in the Dreisam Valley ( Dreisamtal ) which is located in the Southern Black Forest ( Südschwarzwald ). The origin of the river can be found close to a bridge on the Landesstraße 127 which leads from Kirchzarten to Stegen. Here, two streams, the Rotbach and Wagensteinbach, meet to form the Dreisam river. This confluence is located in the western part of the Southern Black Forest Nature Park below

96-427: A hierarchical pattern . Other terms for a drainage basin are catchment area , catchment basin , drainage area , river basin , water basin , and impluvium . In North America, they are commonly called a watershed , though in other English-speaking places, "watershed" is used only in its original sense, that of the drainage divide line. A drainage basin's boundaries are determined by watershed delineation ,

144-437: A common task in environmental engineering and science. In a closed drainage basin, or endorheic basin , rather than flowing to the ocean, water converges toward the interior of the basin, known as a sink , which may be a permanent lake, a dry lake , or a point where surface water is lost underground . Drainage basins are similar but not identical to hydrologic units , which are drainage areas delineated so as to nest into

192-454: A drainage basin, and there are different ways to interpret that data. In the unlikely event that the gauges are many and evenly distributed over an area of uniform precipitation, using the arithmetic mean method will give good results. In the Thiessen polygon method, the drainage basin is divided into polygons with the rain gauge in the middle of each polygon assumed to be representative for

240-540: A drainage boundary is referred to as watershed delineation . Finding the area and extent of a drainage basin is an important step in many areas of science and engineering. Most of the water that discharges from the basin outlet originated as precipitation falling on the basin. A portion of the water that enters the groundwater system beneath the drainage basin may flow towards the outlet of another drainage basin because groundwater flow directions do not always match those of their overlying drainage network. Measurement of

288-608: A few kilometres east of Freiburg, where it widens into a broad, level valley floor, the Zarten Basin ( Zartener Becken ). The main town of the valley is Kirchzarten which incorporates the village of Zarten, a settlement of Celtic origin ( Tarodunum ). Other places in the valley are Stegen , where the Eschbach valley from St. Peter joins, Buchenbach , where it meets the Wagensteig valley coming from St. Märgen and

336-469: A flood. In order to prevent accidents like this, the city is planning to install boom gates along the path. The drainage basin of the Dreisam as far as Riegel covers 568 km². In Germany it is therefore characterized as a drainage basin of medium size. The drainage system of the Dreisam has many branches and can be characterized as a complex first degree river regime which is marked by two major discharges. A maximum discharges can be measured in spring as

384-602: A multi-level hierarchical drainage system . Hydrologic units are defined to allow multiple inlets, outlets, or sinks. In a strict sense, all drainage basins are hydrologic units but not all hydrologic units are drainage basins. About 48.71% of the world's land drains to the Atlantic Ocean . In North America , surface water drains to the Atlantic via the Saint Lawrence River and Great Lakes basins,

432-400: A result of melting snow. Another major discharge can also be measured in summer or fall depending on when it is raining the most. There are a couple of rivers that coalesce with the Dreisam, which are the headwater streams Rotbach and Wagensteigbach and (ordered towards downstream): Krummbach (which is also called Zastler Bach in the upper section), Brugga, Eschbach and Glotter . The waters of

480-465: Is also of significance in the matter of individual traffic since on the south bank there are bikeways and on both sides motorways that lead to the city center of Freiburg and the “Zubringer Mitte” (highway 31a) to Beratzhausen. Since 2011, the Dreisam has also been used as the venue of an annual duck race fund-raiser that starts in Freiburg's city center. Thousands of numbered rubber ducks are tossed into

528-418: Is an area of land in which all flowing surface water converges to a single point, such as a river mouth , or flows into another body of water , such as a lake or ocean . A basin is separated from adjacent basins by a perimeter, the drainage divide , made up of a succession of elevated features, such as ridges and hills . A basin may consist of smaller basins that merge at river confluences , forming

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576-487: Is referred to as " watershed management ". In Brazil , the National Policy of Water Resources, regulated by Act n° 9.433 of 1997, establishes the drainage basin as the territorial division of Brazilian water management. When a river basin crosses at least one political border, either a border within a nation or an international boundary, it is identified as a transboundary river . Management of such basins becomes

624-614: Is the Dead Sea . Drainage basins have been historically important for determining territorial boundaries, particularly in regions where trade by water has been important. For example, the English crown gave the Hudson's Bay Company a monopoly on the fur trade in the entire Hudson Bay basin, an area called Rupert's Land . Bioregional political organization today includes agreements of states (e.g., international treaties and, within

672-713: The African Great Lakes , the interiors of Australia and the Arabian Peninsula , and parts in Mexico and the Andes . Some of these, such as the Great Basin, are not single drainage basins but collections of separate, adjacent closed basins. In endorheic bodies of water where evaporation is the primary means of water loss, the water is typically more saline than the oceans. An extreme example of this

720-651: The Black Forest . For many tourists, the Dreisam valley is mainly known for its hiking and mountain biking trails through the Black Forest. The proximity to Freiburg as well as to neighbouring Alsace make the area a popular destination. The Schauinsland hill and the Feldberg , the highest mountain in the Black Forest, are easily accessible from the valley. The four municipalities of Kirchzarten, Stegen, Buchenbach and Oberried have joined forces to promote

768-607: The Eastern Seaboard of the United States, the Canadian Maritimes , and most of Newfoundland and Labrador . Nearly all of South America east of the Andes also drains to the Atlantic, as does most of Western and Central Europe and the greatest portion of western Sub-Saharan Africa , as well as Western Sahara and part of Morocco . The two major mediterranean seas of the world also flow to

816-552: The Elz . From 1817 to 1842 the Dreisam was canalized in its whole length from Kirchzarten to Riegel under the leadership of Johann Gottfried Tulla . However it should be renaturalized in the east of Freiburg at a length of 800m. It overcomes 199m height, from Kirchzarten (337m NHN) until its mouth into the Elz (178m) at Riegel. 135m above or southwards of the river mouth the Glotter leads into

864-687: The Glotter at Nimburg-Bottingen. As a result, the Freiburger Bächlewasser flows into the Dreisam only shortly before Riegel . In the urban area of Freiburg, the Dreisam itself runs in northwestern direction along the B31. After crossing under the A5 the river flows through March, at the eastern edge of the Kaiserstuhl as well as the western edge of Nimberg towards Riegel, where it leads into

912-790: The Höllental valley which descends from Hinterzarten , and Oberried , where the Oberried valley joins from the Notschrei . The Freiburg subdistricts of Kappel , Ebnet and Littenweiler also lie within the Dreisamtal. The eponymous river flows through the Dreisam Valley, which was formed by sedimentary deposits from the inflowing streams that unite to form the Dreisam . More than 10 million m of groundwater are withdrawn from

960-735: The Mississippi (3.22 million km ), and the Río de la Plata (3.17 million km ). The three rivers that drain the most water, from most to least, are the Amazon, Ganges , and Congo rivers. Endorheic basin are inland basins that do not drain to an ocean. Endorheic basins cover around 18% of the Earth's land. Some endorheic basins drain to an Endorheic lake or Inland sea . Many of these lakes are ephemeral or vary dramatically in size depending on climate and inflow. If water evaporates or infiltrates into

1008-825: The Naturschutzgebiet Taubergießen. The Dreisam's catchment area is especially prone to flooding due to the steep topography and the climatically and orographically high precipitation. From the Feldberg to the Pegel Ebnet the average slope is at 21° or rather 43% downhill grade. Because of its round shape the area has a high aspect ratio of 0.7 and a high circularity ratio of 0.55 which leads to temporal runoff concentration and thus can quickly lead to flooding. The aquifer, which consists primarily of solid rock, absorbs little water and hence leads to quick drainage, particularly in cases of heavy rainfall. Because of melting snow and heavy rainfalls in spring,

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1056-809: The Nile River ), Southern , Central, and Eastern Europe , Turkey , and the coastal areas of Israel , Lebanon , and Syria . The Arctic Ocean drains most of Western Canada and Northern Canada east of the Continental Divide , northern Alaska and parts of North Dakota , South Dakota , Minnesota , and Montana in the United States, the north shore of the Scandinavian peninsula in Europe, central and northern Russia, and parts of Kazakhstan and Mongolia in Asia , which totals to about 17% of

1104-789: The Andes. The Indian Ocean 's drainage basin also comprises about 13% of Earth's land. It drains the eastern coast of Africa, the coasts of the Red Sea and the Persian Gulf , the Indian subcontinent , Burma, and most parts of Australia . The five largest river basins (by area), from largest to smallest, are those of the Amazon (7 million km ), the Congo (4 million km ), the Nile (3.4 million km ),

1152-726: The Atlantic. The Caribbean Sea and Gulf of Mexico basin includes most of the U.S. interior between the Appalachian and Rocky Mountains , a small part of the Canadian provinces of Alberta and Saskatchewan , eastern Central America , the islands of the Caribbean and the Gulf, and a small part of northern South America. The Mediterranean Sea basin, with the Black Sea , includes much of North Africa , east-central Africa (through

1200-535: The Dreisam Valley touristically. Parts of the valley are designated as a landscape conservation area, from the eastern city limits of Freiburg to Buchenbach between the lower reaches of the Wagensteigbach stream and the lower reaches of the Rotbach brook. 47°58′50″N 7°55′18″E  /  47.98056°N 7.92167°E  / 47.98056; 7.92167 Drainage basin A drainage basin

1248-603: The Dreisam directly west of the Höllentalbahnbrücke bridge which is located in the Stühlinger district. The remaining water runs through the areas Eschholz and Bischofslinde towards the west and ultimately flows back into the Dreisam near Lehen. The northern branch of the river runs often subterraneously through the northwestern historic center of the districts Beurbarung and Brühl and flows westwards of Gundelfingen into Schobbach. Schobbach then again leads into

1296-497: The Dreisam used to drive mills, yielding energy for industrial establishments like gem grinderies and tanneries. Today there are still small river power stations like at the Sandfang. In the past, people even caught salmon in the Dreisam, today however, the fishery does no longer have any importance. Nowadays, the Dreisam with its bank paths and meadows serves as a recreational spot for taking walks, swimming or barbecueing. The Dreisam

1344-582: The Dreisam was secured on both sides through walls and channelized from Freiburg onward. However, on December 23, 1991 there was a flood that caused damage in the eastern part of Freiburg. The riverside paths below the bridges of the Mannheim-Basel-Karlsruhe-railway, called Rheintalbahn in German, are often flooded during high water. Even though warning signs were installed along the path, two cyclists died there in 2010 and 2013 during

1392-556: The Dreisam, coming from south-southeastern. Northeastern of St. Michaelsberg (241 m NHN), the Alte Dreisam, from south-southwestern, flows into the direct mouth of Dreisam and Elz. The 15 km long Leopoldskanal branches off right below the confluence of the earlier mentioned Elz. This canal is used to drain water to the Rhine if the Dreisam has high-water. The canal ends north-west of Rheinhausen , south-west of Rust and west of

1440-484: The Freiburg soccer stadium called Schwarzwald-Stadion and continues flowing westwards. In the eastern part of the city, water is withdrawn from the river at Sandfang. It is used to supply the Gewerbekanal, an industrial canal, and the famous Freiburg Bächle with water. A division of the river into a northern and southern branch takes place in the historic city center. The majority of the southern branch flows back into

1488-623: The US, interstate compacts ) or other political entities in a particular drainage basin to manage the body or bodies of water into which it drains. Examples of such interstate compacts are the Great Lakes Commission and the Tahoe Regional Planning Agency . In hydrology , the drainage basin is a logical unit of focus for studying the movement of water within the hydrological cycle . The process of finding

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1536-406: The basin, it can form tributaries that change the structure of the land. There are three different main types, which are affected by the rocks and ground underneath. Rock that is quick to erode forms dendritic patterns, and these are seen most often. The two other types of patterns that form are trellis patterns and rectangular patterns. Rain gauge data is used to measure total precipitation over

1584-430: The discharge of water from a basin may be made by a stream gauge located at the basin's outlet. Depending on the conditions of the drainage basin, as rainfall occurs some of it seeps directly into the ground. This water will either remain underground, slowly making its way downhill and eventually reaching the basin, or it will permeate deeper into the soil and consolidate into groundwater aquifers. As water flows through

1632-441: The drainage area is dependent on the soil type. Certain soil types such as sandy soils are very free-draining, and rainfall on sandy soil is likely to be absorbed by the ground. However, soils containing clay can be almost impermeable and therefore rainfall on clay soils will run off and contribute to flood volumes. After prolonged rainfall even free-draining soils can become saturated , meaning that any further rainfall will reach

1680-697: The drainage basin to the mouth, and may accumulate there, disturbing the natural mineral balance. This can cause eutrophication where plant growth is accelerated by the additional material. Because drainage basins are coherent entities in a hydrological sense, it has become common to manage water resources on the basis of individual basins. In the U.S. state of Minnesota , governmental entities that perform this function are called " watershed districts ". In New Zealand, they are called catchment boards. Comparable community groups based in Ontario, Canada, are called conservation authorities . In North America, this function

1728-435: The ground and along rivers it can pick up nutrients , sediment , and pollutants . With the water, they are transported towards the outlet of the basin, and can affect the ecological processes along the way as well as in the receiving water body . Modern use of artificial fertilizers , containing nitrogen (as nitrates ), phosphorus , and potassium , has affected the mouths of drainage basins. The minerals are carried by

1776-781: The ground at its terminus, the area can go by several names, such playa, salt flat, dry lake , or alkali sink . The largest endorheic basins are in Central Asia , including the Caspian Sea , the Aral Sea , and numerous smaller lakes. Other endorheic regions include the Great Basin in the United States, much of the Sahara Desert , the drainage basin of the Okavango River ( Kalahari Basin ), highlands near

1824-460: The maximum amount of draining water runs off in April. Even though the heaviest rainfalls occur in summer, the high water consumption of the local vegetation only leads to secondary drainage maximums. In March 1896 a historic flood killed two people and destroyed several bridges. Among the people that were killed was Carl Siegel, a German jurist. Nowadays floods do usually not cause major damages since

1872-418: The rainfall on the area of land included in its polygon. These polygons are made by drawing lines between gauges, then making perpendicular bisectors of those lines form the polygons. The isohyetal method involves contours of equal precipitation are drawn over the gauges on a map. Calculating the area between these curves and adding up the volume of water is time-consuming. Isochrone maps can be used to show

1920-631: The responsibility of the countries sharing it. Nile Basin Initiative , OMVS for Senegal River , Mekong River Commission are a few examples of arrangements involving management of shared river basins. Management of shared drainage basins is also seen as a way to build lasting peaceful relationships among countries. The catchment is the most significant factor determining the amount or likelihood of flooding . Catchment factors are: topography , shape, size, soil type, and land use (paved or roofed areas). Catchment topography and shape determine

1968-527: The river and flow a few hundred meters upstream before being fished out again. 47°59′N 7°50′E  /  47.983°N 7.833°E  / 47.983; 7.833 Dreisam Valley The Dreisam Valley ( German : Dreisamtal ) is a valley east of the south German city of Freiburg . The valley lies within the Southern Black Forest Nature Park in the state of Baden-Württemberg . The Dreisam Valley runs for

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2016-461: The river rather than being absorbed by the ground. If the surface is impermeable the precipitation will create surface run-off which will lead to higher risk of flooding; if the ground is permeable, the precipitation will infiltrate the soil. Land use can contribute to the volume of water reaching the river, in a similar way to clay soils. For example, rainfall on roofs, pavements , and roads will be collected by rivers with almost no absorption into

2064-587: The so-called Höllental, where the Rotchbach flows through, and the Wagensteig valley. From there on the Dreisam, which was canalized, flows towards the west and reaches Freiburg at the eastern end of Ebnet. Along the way the Dreisam meets the Krummbach and Brugga, two streams originating south of the Dreisam, as well as the Eschbach stream which flows north of the Dreisam. The river leaves the Black Forest at

2112-418: The speed with which the runoff reaches a river. A long thin catchment will take longer to drain than a circular catchment. Size will help determine the amount of water reaching the river, as the larger the catchment the greater the potential for flooding. It is also determined on the basis of length and width of the drainage basin. Soil type will help determine how much water reaches the river. The runoff from

2160-415: The time taken for rain to reach the river, while catchment size, soil type, and development determine the amount of water to reach the river. Generally, topography plays a big part in how fast runoff will reach a river. Rain that falls in steep mountainous areas will reach the primary river in the drainage basin faster than flat or lightly sloping areas (e.g., > 1% gradient). Shape will contribute to

2208-477: The time taken for runoff water within a drainage basin to reach a lake, reservoir or outlet, assuming constant and uniform effective rainfall. Drainage basins are the principal hydrologic unit considered in fluvial geomorphology . A drainage basin is the source for water and sediment that moves from higher elevation through the river system to lower elevations as they reshape the channel forms. Drainage basins are important in ecology . As water flows over

2256-482: The whole of the valley every year, a considerable part of which provides drinking water for the city of Freiburg. The flat valley floor is therefore partly a water protection area ( Wasserschutzgebiet ). (by way of comparison, the annual groundwater outflow from the valley is less than 15 million m .) The B 31 and the Höllentalbahn railway run through the Dreisam valley, each leading from Freiburg into

2304-789: The world's land. Just over 13% of the land in the world drains to the Pacific Ocean . Its basin includes much of China, eastern and southeastern Russia, Japan, the Korean Peninsula , most of Indochina, Indonesia and Malaysia, the Philippines, all of the Pacific Islands , the northeast coast of Australia , and Canada and the United States west of the Continental Divide (including most of Alaska), as well as western Central America and South America west of

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