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{{Short description|Land area where water converges to a common outlet}}
]
{{Redirect2|Catchment|Catchment basin|the human geography concept|Catchment area}}
A '''drainage basin''' is an extent or area of land where ] from ] and ] or ] drains downhill into a body of water, such as a ], ], ], ], ], ] or ]. The drainage basin includes both the streams and rivers that convey the water as well as the land surfaces from which water drains into those channels, and is separated from adjacent basins by a ].<ref>
] drains the largest area of any ] river, much of it ] regions. Agricultural runoff and other water pollution that flows to the outlet is the cause of the ] in the ].]]
{{cite web
|url=http://www.uwsp.edu/geo/faculty/ritter/glossary/a_d/drainage_basin.html
|title=drainage basin
|publisher=www.uwsp.edu
|accessdate=2008-02-21
|last=
|first=
}}
</ref>


A '''drainage basin''' is an area of land in which all flowing ] converges to a single point, such as a ], or flows into another ], such as a ] or ]. A basin is separated from adjacent basins by a perimeter, the '']'',<ref>{{cite web |url= http://www.uwsp.edu/geo/faculty/ritter/glossary/a_d/drainage_basin.html |title=drainage basin |work=The Physical Environment |publisher=University of Wisconsin–Stevens Point |archive-url=https://web.archive.org/web/20040321033433/http://www.uwsp.edu/geo/faculty/ritter/glossary/a_d/drainage_basin.html |archive-date=March 21, 2004 }}</ref> made up of a succession of elevated features, such as ]s and ]s. A basin may consist of smaller basins that merge at river ]s, forming a ].<ref name=whatis>{{cite web |url=http://www.wr.udel.edu/cb/whatwhycare.html |title=What is a watershed and why should I care? |publisher=University of Delaware |access-date=2008-02-11 |archive-url=https://web.archive.org/web/20120121122519/http://www.wr.udel.edu/cb/whatwhycare.html |archive-date=2012-01-21 |url-status=dead }}</ref>
The drainage basin acts as a ] by collecting all the water within the area covered by the basin and channelling it into a waterway. Each drainage basin is separated topographically from adjacent basins by a geographical barrier such as a ], ] or ], which is known as a ].


Other terms for a drainage basin are '''catchment area''', '''catchment basin''', '''drainage area''', '''river basin''', '''water basin''',<ref>{{cite book |last=Lambert |first=David |title=The Field Guide to Geology |publisher=Checkmark Books |year=1998 |pages= |isbn=0-8160-3823-6 |url-access=registration |url=https://archive.org/details/fieldguidetogeol00lamb_0/page/130}}</ref><ref>{{cite journal |last1=Uereyen |first1=Soner |last2=Kuenzer |first2=Claudia |title=A Review of Earth Observation-Based Analyses for Major River Basins |journal=Remote Sensing |date=9 December 2019 |volume=11 |issue=24 |pages=2951 |doi=10.3390/rs11242951 |bibcode=2019RemS...11.2951U |doi-access=free }}</ref> and ].<ref name="Huneau-2013">{{cite journal |last1=Huneau|first1=F. |last2=Jaunat |first2=J. |last3=Kavouri |first3=K. |last4=Plagnes |first4=V.| last5=Rey |first5=F. |last6=Dörfliger |first6=N. |date= 2013-07-18 |publisher= Elsevier |title= Intrinsic vulnerability mapping for small mountainous ] aquifers, implementation of the new PaPRIKa method to Western Pyrenees (France) |journal= Engineering Geology |volume= 161 |pages=81–93 |quote= 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"). |doi=10.1016/j.enggeo.2013.03.028 |bibcode=2013EngGe.161...81H }}</ref><ref>{{cite web |url= https://www.encyclopedie-environnement.org/en/water/natural-mineral-waters/#5_Protected_and_managed_over_time |title= Natural mineral waters |last=Lachassagne |first=Patrick |publisher=Encyclopédie de l'environnement |date=2019-02-07 |access-date=2019-06-10 |quote= 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 ] 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; ...}}</ref><ref>{{cite journal |doi=10.1016/S0022-1694(00)00321-8 |last1=Labat |first1=D. |last2=Ababou |first2=R. |last3=Manginb |first3=A. |title=Rainfall–runoff relations for ]ic springs. Part I: convolution and spectral analyses |journal= Journal of Hydrology |volume=238 |issue=3–4 |pages=123–148 |date=2000-12-05 |quote= 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. |bibcode=2000JHyd..238..123L}}</ref> In North America, they are commonly called a '''watershed''', though in other English-speaking places, "]" is used only in its original sense, that of the drainage divide line.
Other terms that are used to describe a drainage basin are '''catchment''', '''catchment area''', '''catchment basin''', '''drainage area''', '''river basin''', '''water basin''' and '''watershed'''.<ref>{{cite book
| last = Lambert
| first = David
| authorlink =
| title = The Field Guide to Geology
| publisher = Checkmark Books
| series =
| year = 1998
| pages =130–13
| doi =
| isbn = 0-8160-3823-6 }}</ref> In the technical sense, a watershed refers to a divide that separates one drainage area from another drainage area.<ref>{{cite web
|author=
|year=
|url=http://watershed.org/news/fall_94/terminology.html
|title=Recommended Watershed Terminology
|publisher=watershed.org
|accessdate=2008-02-10
}}
</ref> However, in the ] and ], the term is often used to mean a drainage basin or catchment area itself. Drainage basins drain into other drainage basins in a ], with smaller '''sub-drainage basins''' combining into larger drainage basins.<ref name=whatis>{{cite web
|author=
|year=
|url=http://www.wr.udel.edu/cb/whatwhycare.html
|title=What is a watershed and why should I care?
|publisher=university of delaware
|accessdate=2008-02-11
}}
</ref>


A drainage basin's boundaries are determined by ], a common task in environmental engineering and science.
The ] launched the website ] for the US public to exchange information and locate resources needed to restore local drainage basins in that country.


In a closed drainage basin, or ], rather than flowing to the ocean, water converges toward the interior of the basin, known as a ], which may be a permanent lake, a ], or a point where surface water is ].<ref name=virginia>{{cite web |url= http://www.dcr.virginia.gov/stormwater_management/hu.shtml |title= Hydrologic Unit Geography |publisher= Virginia Department of Conservation & Recreation |access-date= 21 November 2010 |url-status= dead |archive-url= https://archive.today/20121214100316/http://www.dcr.virginia.gov/stormwater_management/hu.shtml |archive-date= 14 December 2012 }}</ref>
== Major drainage basins of the world ==
{{see also|List of drainage basins}}


Drainage basins are similar but not identical to ]s, which are drainage areas delineated so as to nest into a multi-level hierarchical ]. 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.<ref name=virginia/>
=== Map ===
]s, showing drainage into the major oceans and seas of the world. Grey areas are ] basins that do not drain to the ocean.]]


== Major drainage basins of the world ==
Drainage basins of the principal oceans and seas of the world. Grey areas are ] basins that do not drain to the ocean.
{{Main list|List of drainage basins by area}}
]s, showing how terrestrial drainage basins drain into the oceans. Grey areas are ]s that do not drain to the oceans]]


=== Ocean basins === === Ocean basins ===
About 48.71% of the world's land drains to the ].{{citation needed|date=January 2017}} In ], surface water drains to the Atlantic via the ] and ] basins, the ] of the United States, the ], and most of ]. Nearly all of ] east of the ] also drains to the Atlantic, as does most of ] and ] and the greatest portion of western ], as well as ] and part of ].


The two major ] of the world also flow to the Atlantic. The ] and ] basin includes most of the U.S. interior between the ] and ], a small part of the Canadian provinces of ] and ], eastern ], the islands of the Caribbean and the Gulf, and a small part of northern South America. The ] basin, with the ], includes much of ], east-central ] (through the ]), ], Central, and ], ], and the coastal areas of ], ], and ].
There are numerous drainage basins throughout the world in all sorts of places. The following is a list of some of the major ones:
* About 47% of all land in the world drains to the ]. In North America, it directly drains the ] and ] basins, the ] of the United States, the ], and most of ]. It also directly drains nearly all of ] east of the ], most of Western and Central ], and the greatest portion of western ]. The three major ] of the world also flow to the Atlantic:
** The American Mediterranean Sea (the ] and ]) basin includes most of the ] interior between the Appalachian and Rocky Mountain ranges, a small part of the ] provinces of ] and ], eastern ], the islands of the Caribbean and the Gulf, and a small part of northern ].
** The European ] basin includes much of northern ], east-central ] (through the ]), southern, central, and eastern ], ], and the coastal areas of ], ], and ].
** The ] basin drains most of Western and Northern ] east of the ], the north shore of ] and parts of ], ], ], and ] in the United States, the north shore of the ] in Europe, and much of central and northern ].
* Just over 13% of the land in the world drains to the ]. Its basin includes much of ], southeastern ], ], ], most of ] and ], the ], all of the ], the northeast coast of ], and the western parts of Canada, the United States (including most of ]), ], and ].
* The ]'s drainage basin also comprises about 13% of Earth's land. It drains the eastern coast of Africa, the coasts of the ] and the ], the ], ], and most of ].
* The ] drains ]. Antarctica comprises approximately eight percent of the Earth's land.


The ] drains most of ] and ] east of the ], northern ] and parts of ], ], ], and ] in the United States, the north shore of the ] in Europe, central and northern Russia, and parts of ] and ] in ], which totals to about 17% of the world's land.<ref name="Vörösmarty-2000">{{Cite journal|last1=Vörösmarty|first1=C. J.|last2=Fekete|first2=B. M.|last3=Meybeck|first3=M.|last4=Lammers|first4=R. B.|date=2000|title=Global system of rivers: Its role in organizing continental land mass and defining land-to-ocean linkages|journal=Global Biogeochemical Cycles|language=en|volume=14|issue=2|pages=599–621|doi=10.1029/1999GB900092|bibcode=2000GBioC..14..599V|s2cid=129463497 |issn=1944-9224|doi-access=free}}</ref>
=== Largest river basins ===


Just over 13% of the land in the world drains to the ].<ref name="Vörösmarty-2000" /> Its basin includes much of China, eastern and southeastern Russia, Japan, the ], most of Indochina, Indonesia and Malaysia, the Philippines, all of the ], the northeast coast of ], 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 three largest river basins (by area), from largest to smallest, are the ] basin, the ] basin, and the ] basin.<ref>{{cite web|url=http://water.usgs.gov/nasqan/progdocs/factsheets/missfacts/missfs.html|title=NASQAN Mississippi River Basin Fact Sheet|last=Coupe Jr.; Goolsby|first=Richard; Donald|coauthors=Donald A. Goolsby|date=June 7, 1999|work=Geology|publisher=NASQAN|pages=1|accessdate=2008-06-24}}</ref> The three rivers that drain the most water, from most to least, are the ], ], and ] Rivers.<ref>Encarta Encyclopedia articles on ], ], and ] Published by Microsoft in computers.</ref>

The ]'s drainage basin also comprises about 13% of Earth's land. It drains the eastern coast of Africa, the coasts of the ] and the ], the ], Burma, and most parts of ].<ref>{{cite news |title=Largest Drainage Basins in the World |url=https://www.worldatlas.com/articles/largest-drainage-basins-in-the-world.html |work=WorldAtlas |date=17 May 2018}}</ref>

=== Largest river basins ===
The five largest river basins (by area), from largest to smallest, are those of the ] (7 million km{{sup|2}}), the ] (4 million km{{sup|2}}), the ] (3.4 million km{{sup|2}}), the ] (3.22 million km{{sup|2}}), and the {{Lang|es|]|italic=no}} (3.17 million km{{sup|2}}). The three rivers that drain the most water, from most to least, are the Amazon, ], and Congo rivers.


=== Endorheic drainage basins === === Endorheic drainage basins ===
] in ]]] ] in ]]]
{{main|Endorheic basin}} {{Main|Endorheic basin}}

] are inland basins that do not drain into an ocean; around 18% of all land drains to endorheic lakes or seas. The largest of these consists of much of the interior of ], and drains into the ] and the ]. Other basins include the ] in the ], much of the ], the watershed of the ] (]), highlands near the ], the interiors of ] and the ], and parts in ] and the ].
] 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 ] or ]. Many of these lakes are ] 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, ], or ].

The largest endorheic basins are in Central ], including the ], the ], and numerous smaller lakes. Other endorheic regions include the ] in the United States, much of the ], the drainage basin of the ] (]), highlands near the ], the interiors of ] and the ], and parts in ] and the ]. Some of these, such as the Great Basin, are not single drainage basins but collections of separate, adjacent closed basins.

In endorheic ] 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 ].{{citation needed||date=April 2023}}


== Importance ==
In endorheic ] where evaporation is the primary means of water loss, the water is typically more saline than the ]. An extreme example is the ].


== Importance of drainage basins ==
=== Geopolitical boundaries === === 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 ] crown gave the ] a monopoly on the ] in the entire ] basin, an area called ]. Today, ] can include agreements of states in a particular drainage basin to defend it. One example of this is the ]. Drainage basins have been historically important for determining territorial boundaries, particularly in regions where trade by water has been important. For example, the ] crown gave the ] a monopoly on the ] in the entire ] basin, an area called ]. ] political organization today includes agreements of states (e.g., international ] and, within the US, ]s) 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 ] and the ].


=== Hydrology === === Hydrology ===
], part of the ] drainage basin.]] ], part of the ] drainage basin]]
In ], the drainage basin is a logical unit of focus{{clarify|date=October 2024}} for studying the movement of water within the ]. The process of finding a drainage boundary is referred to as ]. Finding the area and extent of a drainage basin is an important step in many areas of science and engineering.


In ], the drainage basin is a logical unit of focus for studying the movement of water within the ], because the majority of water that discharges from the basin outlet originated as ] falling on the basin. A portion of the water that enters the ] 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 ] located at the basin's outlet. Most of the water that discharges from the basin outlet originated as ] falling on the basin.<ref>{{Cite web|title=drainage basin Definition, Example, & Facts|url=https://www.britannica.com/science/drainage-basin|access-date=2021-10-22|website=Encyclopedia Britannica|language=en}}</ref> A portion of the water that enters the ] 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 ] 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.<ref>{{Cite web|title=Watersheds and Drainage Basins|url=https://www.usgs.gov/special-topic/water-science-school/science/watersheds-and-drainage-basins?qt-science_center_objects=0#qt-science_center_objects|access-date=2021-10-22 |website=U.S. Geological Survey |date=June 8, 2019 |url-status=live |archive-url= https://web.archive.org/web/20211022172131/https://www.usgs.gov/special-topic/water-science-school/science/watersheds-and-drainage-basins?qt-science_center_objects=0#qt-science_center_objects|archive-date=2021-10-22 }}</ref>


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 ] patterns, and these are seen most often. The two other types of patterns that form are trellis patterns and rectangular patterns.<ref>{{Cite web|last=Earle|first=Steven|date=2015-09-01|title=13.2 Drainage Basins|url=https://opentextbc.ca/geology/chapter/13-2-drainage-basins/|language=en |work= Physical Geology |publisher=BCcampus Open Publishing |url-status=live |archive-url=https://web.archive.org/web/20240415103436/https://opentextbc.ca/geology/chapter/13-2-drainage-basins/ |archive-date= Apr 15, 2024 }}</ref>
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 ] method will give good results. In the ] method, the watershed is divided into polygons with the rain gauge in the middle of each polygon assumed to be representative for 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 ]al 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.


Rain gauge data is used to measure total precipitation over 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 ] method will give good results. In the ] method, the drainage basin is divided into polygons with the rain gauge in the middle of each polygon assumed to be representative for 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 ]al 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.
=== Geomorphology ===


]s can be used to show the time taken for ] within a drainage basin to reach a lake, reservoir or outlet, assuming constant and uniform effective rainfall.<ref name="hydrolearthsystsci bell 1998">{{cite journal | title=A grid-based distributed flood forecasting model for use with weather radar data: Part 1. Formulation | author=Bell, V. A. | journal=Hydrology and Earth System Sciences | year=1998 | volume=2 | issue=2/3 | pages=265–281 | doi=10.5194/hess-2-265-1998 | publisher=] | author2=Moore, R. J.| bibcode=1998HESS....2..265B | url=https://hal.archives-ouvertes.fr/hal-00304542/file/hess-2-265-1998.pdf | doi-access=free |via=HAL |bibcode-access=free |url-status=live |archive-url=https://web.archive.org/web/20240118075225/https://hal.science/hal-00304542/file/hess-2-265-1998.pdf |archive-date= Jan 18, 2024 }}</ref><ref name="subramanya 2008">{{cite book | title=Engineering Hydrology | publisher=Tata McGraw-Hill | author=Subramanya, K | year=2008 | pages=298 | isbn=978-0-07-064855-5 | url=https://books.google.com/books?id=LROqKvHaRyMC&q=Clark%E2%80%99s+IUH+time-area+method+isochrone&pg=PA298}}</ref><ref name="unesco ">{{cite web | url=http://webworld.unesco.org/water/ihp/db/glossary/glu/EN/GF0705EN.HTM | title=EN 0705 isochrone map | publisher=] | access-date=March 21, 2012 | url-status=dead | archive-url=https://web.archive.org/web/20121122145250/http://webworld.unesco.org/water/ihp/db/glossary/glu/EN/GF0705EN.HTM | archive-date=November 22, 2012 }}</ref><ref>{{Cite web |url=https://www.petropedia.com/definition/2126/isochron-map |title=Isochron Map |access-date=2021-09-03 |archive-date=2021-09-03 |archive-url=https://web.archive.org/web/20210903103537/https://www.petropedia.com/definition/2126/isochron-map |url-status=dead }}</ref>
Drainage basins are the principal hydrologic unit considered in ] ]. A drainage basin is the source for water and ] that moves through the river system and reshapes the channel.

=== Geomorphology ===
Drainage basins are the principal hydrologic unit considered in ] ]. A drainage basin is the source for water and ] that moves from higher elevation through the river system to lower elevations as they reshape the channel forms.


=== Ecology === === Ecology ===
] drainage basin. The dashed line is the main water divide of the ] basin.]]
] drains the largest area of any ] river, much of it ] regions. Agricultural runoff and other water pollution that flows to the outlet is the cause of the ] in the ].]]
] of the ]'s drainage basin in ]]]


Drainage basins are important elements to consider also in ]. As water flows over the ground and along rivers it can pick up nutrients, sediment, and ]. Like the water, they get transported towards the outlet of the basin, and can affect the ecological processes along the way as well as in the receiving water source. Drainage basins are important in ]. As water flows over the ground and along rivers it can pick up ], ], and ]. 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 ].


Modern usage of artificial fertilizers, containing nitrogen, phosphorus, and potassium, has affected the mouths of watersheds. The minerals will be carried by the watershed to the mouth and accumulate there, disturbing the natural mineral balance. This can cause eutrophication where plant growth is accelerated by the additional material. Modern use of ]s, containing ] (as ]s), ], and ], 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 ] where plant growth is accelerated by the additional material.


=== Resource management === === Resource management ===
{{Further|]}} {{Further|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 ] of ], governmental entities that perform this function are called ]s. In New Zealand, they are called catchment boards. Comparable community groups based in Ontario, Canada, are called ]. In North America this function is referred to as ]. 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 ], governmental entities that perform this function are called "]s".<ref>{{Cite web|date=2010-09-07|title=Twin Cities Metropolitan Area (TCMA) Watersheds|url=https://www.pca.state.mn.us/water/twin-cities-metropolitan-area-tcma-watersheds|access-date=2021-09-22|website=Minnesota Pollution Control Agency|language=en}}</ref> In New Zealand, they are called catchment boards. Comparable community groups based in Ontario, Canada, are called ]. In North America, this function is referred to as "]".
In ], the National Policy of Water Resources, regulated by Act n° 9.433 of 1997, establishes the drainage basin as territorial division of Brazilian water management. In ], 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 ]. Management of such basins becomes the responsibility of the countries sharing it. ], ] for ], ] 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.<ref>{{cite web|url=http://www.strategicforesight.com/inner-articles.php?id=310#.WA9Ia-V97GI|title=Water Cooperation for a Secure World|website=www.strategicforesight.com|date = 25 November 2013|last1= bin Talal|first1 = Hassan|last2= Waslekar|first2= Sundeep}}</ref>


== Catchment factors == == Catchment factors ==
The catchment is the most significant factor determining the amount or likelihood of ]. The catchment is the most significant factor determining the amount or likelihood of ].

Catchment factors are: ], shape, size, ] type and ] (paved or ]ed areas). Catchment topography and shape determine the time taken for ] to reach the river, while catchment size, soil type and development determine the amount of water to reach the river. Catchment factors are: ], shape, size, ] type, and ] (paved or ]ed areas). Catchment topography and shape determine the time taken for ] to reach the river, while catchment size, soil type, and development determine the amount of water to reach the river.


=== Topography === === Topography ===
Topography determines the speed with which the runoff will reach a river. Clearly rain that falls in steep ]ous areas will reach the river faster than flat or gently sloping areas. Generally, topography plays a big part in how fast runoff will reach a river. Rain that falls in steep ]ous areas will reach the primary river in the drainage basin faster than flat or lightly sloping areas (e.g., > 1% gradient).


=== Shape === === Shape ===
Line 112: Line 90:


=== Size === === Size ===
Size will help determine the amount of water reaching the river, as the larger the catchment the greater the potential for flooding. 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 ===
Soil type will help determine how much water reaches the river. Certain soil types such as ]y soils are very free draining and rainfall on sandy soil is likely to be absorbed by the ground. However, soils containing ] 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 ], meaning that any further rainfall will reach the river rather than being absorbed by the ground. 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 ]y soils are very free-draining, and rainfall on sandy soil is likely to be absorbed by the ground. However, soils containing ] 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 ], 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.<ref name="Huneau-2013" />


=== Land use === === 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, ] and ]s will be collected by rivers with almost no absorption into the ]. Land use can contribute to the volume of water reaching the river, in a similar way to clay soils. For example, rainfall on roofs, ], and ]s will be collected by rivers with almost no absorption into the ].
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 == == See also ==
{{Portal|Wetlands}}
* ]
* {{annotated link|Continental Divide of the Americas}}
* ]
* {{annotated link|Integrated catchment management}}
* ]
* {{annotated link|Interbasin transfer}}
* ]
* {{annotated link|International Journal of River Basin Management|abbreviation=JRBM}}
* ]
* ] (JRBM) * {{annotated link|International Network of Basin Organizations}}
* {{annotated link|Main stem}}
* ]
* ] * {{annotated link|River basin management plans}}
* {{annotated link|River bifurcation}}
* ]
* {{annotated link|Tenaja}}

* {{annotated link|Time of concentration}}
== Footnotes ==
*]
{{reflist}}


== References == == References ==
{{Reflist|30em}}
* DeBarry,Paul A. (2004). ''Watersheds: Processes, Assessment and Management.'' John Wiley & Sons.

== External links ==
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{{river morphology}} {{river morphology}}
{{Rivers, streams and springs}}
{{Wetlands}}
{{Authority control}}


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Latest revision as of 19:38, 26 December 2024

Land area where water converges to a common outlet "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 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 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, 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 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.

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 Atlantic Ocean. In North America, surface water drains to the Atlantic via the Saint Lawrence River and Great Lakes basins, 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 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 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 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 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.

Largest river basins

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), 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 drainage basins

Endorheic basin in Central Asia
Main article: Endorheic basin

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 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 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.

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 hydrology, the drainage basin is a logical unit of focus for studying the movement of water within the 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.

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 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 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 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 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 the time taken for runoff water within a drainage basin to reach a lake, reservoir or outlet, assuming constant and uniform effective rainfall.

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.
Digital terrain map of the Latorița River's drainage basin in Romania

Drainage basins are important in ecology. As water flows over 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 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 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 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 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.

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.

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. Lambert, David (1998). The Field Guide to Geology. Checkmark Books. pp. 130–13. ISBN 0-8160-3823-6.
  4. Uereyen, Soner; Kuenzer, Claudia (9 December 2019). "A Review of Earth Observation-Based Analyses for Major River Basins". Remote Sensing. 11 (24): 2951. Bibcode:2019RemS...11.2951U. doi:10.3390/rs11242951.
  5. ^ Huneau, F.; Jaunat, J.; Kavouri, K.; Plagnes, V.; Rey, F.; Dörfliger, N. (2013-07-18). "Intrinsic vulnerability mapping for small mountainous karst aquifers, implementation of the new PaPRIKa method to Western Pyrenees (France)". Engineering Geology. 161. Elsevier: 81–93. Bibcode:2013EngGe.161...81H. 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. Labat, D.; Ababou, R.; Manginb, A. (2000-12-05). "Rainfall–runoff relations for karstic springs. Part I: convolution and spectral analyses". Journal of Hydrology. 238 (3–4): 123–148. Bibcode:2000JHyd..238..123L. 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. ^ "Hydrologic Unit Geography". Virginia Department of Conservation & Recreation. Archived from the original on 14 December 2012. Retrieved 21 November 2010.
  9. ^ Vörösmarty, C. J.; Fekete, B. M.; Meybeck, M.; Lammers, R. B. (2000). "Global system of rivers: Its role in organizing continental land mass and defining land-to-ocean linkages". Global Biogeochemical Cycles. 14 (2): 599–621. Bibcode:2000GBioC..14..599V. doi:10.1029/1999GB900092. ISSN 1944-9224. S2CID 129463497.
  10. "Largest Drainage Basins in the World". WorldAtlas. 17 May 2018.
  11. "drainage basin Definition, Example, & Facts". Encyclopedia Britannica. Retrieved 2021-10-22.
  12. "Watersheds and Drainage Basins". U.S. Geological Survey. June 8, 2019. Archived from the original on 2021-10-22. Retrieved 2021-10-22.
  13. Earle, Steven (2015-09-01). "13.2 Drainage Basins". Physical Geology. BCcampus Open Publishing. Archived from the original on Apr 15, 2024.
  14. Bell, V. A.; Moore, R. J. (1998). "A grid-based distributed flood forecasting model for use with weather radar data: Part 1. Formulation" (PDF). Hydrology and Earth System Sciences. 2 (2/3). Copernicus Publications: 265–281. Bibcode:1998HESS....2..265B. doi:10.5194/hess-2-265-1998. Archived (PDF) from the original on Jan 18, 2024 – via HAL.
  15. Subramanya, K (2008). Engineering Hydrology. Tata McGraw-Hill. p. 298. ISBN 978-0-07-064855-5.
  16. "EN 0705 isochrone map". UNESCO. Archived from the original on November 22, 2012. Retrieved March 21, 2012.
  17. "Isochron Map". Archived from the original on 2021-09-03. Retrieved 2021-09-03.
  18. "Twin Cities Metropolitan Area (TCMA) Watersheds". Minnesota Pollution Control Agency. 2010-09-07. Retrieved 2021-09-22.
  19. bin Talal, Hassan; Waslekar, Sundeep (25 November 2013). "Water Cooperation for a Secure World". www.strategicforesight.com.
River morphology
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Rivers, streams and springs
Rivers
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Fluvial landforms
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