Drainage basin

Source: Wikipedia, the free encyclopedia.
(Redirected from
River basin
)
"Catchment" and "Catchment basin" redirect here. For the human geography concept, see Catchment area.
The Mississippi River drains the largest area of any U.S. river, much of it agricultural regions. Agricultural runoff and other water pollution that flows to the outlet is the cause of the hypoxic, or dead zone in the Gulf of Mexico.

A drainage basin is an area of land where 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,[1] 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 a hierarchical pattern.[2]

Other terms for a drainage basin are catchment area, catchment basin, drainage area, river basin, water basin,[3][4] and impluvium.[5][6][7] 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 a drainage divide.

A drainage basin's boundaries are determined by watershed delineation, a common task in environmental engineering and science.

In a closed drainage basin, or

sink, which may be a permanent lake, a dry lake, or a point where surface water is lost underground.[8]

Drainage basins are similar but not identical to hydrologic unit code, which are drainage areas delineated so as to nest into 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.[8]

Major drainage basins of the world

For a more comprehensive list, see List of drainage basins by area.
Major continental divides, showing how terrestrial drainage basins drain into the oceans. Grey areas are endorheic basins that do not drain to the oceans

Ocean basins

About 48.71% of the world's land drains to 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

Nile River), Southern, Central, and Eastern Europe, Turkey, and the coastal areas of Israel, Lebanon, and Syria
.

The

Scandinavian peninsula in Europe, central and northern Russia, and parts of Kazakhstan and Mongolia in Asia, which totals to about 17% of the world's land.[9]

Just over 13% of the land in the world drains to 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 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.[10]

Largest river basins

The five largest river basins (by area), from largest to smallest, are those of the

Nile (3.4M km2), the Mississippi (3.22M km2), and the Río de la Plata (3.17M km2). The three rivers that drain the most water, from most to least, are the Amazon, Ganges, and Congo rivers.[11]

Endorheic drainage basins

Endorheic basin in Central Asia
Main article: Endorheic basin

ephemeral or vary dramatically in size depending on climate and inflow. If water evaporates or infiltrates into 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

Sahara Desert, the drainage basin of the Okavango River (Kalahari Basin), highlands near 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 is the Dead Sea.[citation needed
]

Importance

Geopolitical boundaries

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 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.

Hydrology

Drainage basin of the Ohio River, part of the Mississippi River drainage basin

In

hydrological cycle. The process of finding 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.

The majority of water that discharges from the basin outlet originated as

precipitation falling on the basin.[12] 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 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.[13]

As water flows through 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.[14]

Rain gauge data is used to measure total precipitation over a drainage basin, and there are different ways to interpret that data. If the gauges are many and evenly distributed over an area of uniform precipitation, using 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.

runoff water within a drainage basin to reach a lake, reservoir or outlet, assuming constant and uniform effective rainfall.[15][16][17][18]

Geomorphology

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.

Ecology

Top-down illustration of a dendritic drainage basin. The dashed line is the main water divide of the hydrography basin.
Latorița River's drainage basin in Romania

Drainage basins are important in

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 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.

Resource management

Further information: Watershed management

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

conservation authorities. In North America, this function 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

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.[20]

Catchment factors

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 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.

Topography

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

Shape will contribute to the speed with which the runoff reaches a river. A long thin catchment will take longer to drain than a circular catchment.

Size

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

Soil type will help determine how much water reaches the river. The runoff from 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 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.[5]

Land use

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 the groundwater. A drainage basin is an area of land where 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.

See also

References

  1. ^ "drainage basin". The Physical Environment. University of Wisconsin–Stevens Point. Archived from the original on March 21, 2004.
  2. ^ "What is a watershed and why should I care?". University of Delaware. Archived from the original on 2012-01-21. Retrieved 2008-02-11.
  3. ISBN 0-8160-3823-6
    .
  4. doi:10.3390/rs11242951
    .
  5. ^
    doi:10.1016/j.enggeo.2013.03.028
    . Efficient management is strongly correlated to the proper protection perimeter definition around springs and proactive regulation of land uses over the spring's catchment area ("impluvium").
  6. ^ Lachassagne, Patrick (2019-02-07). "Natural mineral waters". Encyclopédie de l'environnement. Retrieved 2019-06-10. In order to preserve the long-term stability and purity of natural mineral water, bottlers have put in place "protection policies" for the impluviums (or catchment areas) of their sources. The catchment area is the territory on which the part of precipitated rainwater and/or snowmelt that infiltrates the subsoil feeds the mineral aquifer and thus contributes to the renewal of the resource. In other words, a precipitated drop on the impluvium territory may join the mineral aquifer; ...
  7. doi:10.1016/S0022-1694(00)00321-8
    . The non-karstic impluvium comprises all elements of the ground surface and soils that are poorly permeable, on a part of which water is running while also infiltrating on another minor part. This superficial impluvium, if it exists, constitutes the first level of organization of the drainage system of the karstic basin.
  8. ^ a b "Hydrologic Unit Geography". Virginia Department of Conservation & Recreation. Archived from the original on 14 December 2012. Retrieved 21 November 2010.
  9. ^
    S2CID 129463497. Archived from the original
    on 2021-08-15. Retrieved 2021-08-15.
  10. ^ "Largest Drainage Basins in the World". WorldAtlas. 17 May 2018.
  11. Ganga
    Published by Microsoft in computers.
  12. ^ "drainage basin Definition, Example, & Facts". Encyclopedia Britannica. Retrieved 2021-10-22.
  13. ^ "Watersheds and Drainage Basins". www.usgs.gov. Retrieved 2021-10-22.
  14. ^ Earle, Steven (2015-09-01). "13.2 Drainage Basins".
  15. doi:10.5194/hess-2-265-1998
    .
  16. ISBN 978-0-07-064855-5
    .
  17. ^ "EN 0705 isochrone map". UNESCO. Archived from the original on November 22, 2012. Retrieved March 21, 2012.
  18. ^ "Isochron Map". Archived from the original on 2021-09-03. Retrieved 2021-09-03.
  19. ^ "Twin Cities Metropolitan Area (TCMA) Watersheds". Minnesota Pollution Control Agency. 2010-09-07. Retrieved 2021-09-22.
  20. ^ bin Talal, Hassan; Waslekar, Sundeep (25 November 2013). "Water Cooperation for a Secure World". www.strategicforesight.com.
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