Water divide
Encyclopedia
A drainage divide, water divide, divide or (outside North America
) watershed is the line separating neighbouring drainage basin
s (catchments). In hill
y country, the divide lies along topographical
peaks
and ridge
s, and may be in the form of a single range of hills or mountain
s (known as a Dividing range), but in flat country (especially where the ground is marsh
y) the divide may be invisible – just a more or less notional line on the ground on either side of which falling raindrops will start a journey to different river
s, and even to different sides of a region or continent
.
Drainage divides are important geographical
, and often also political
boundaries
. Road
s (such as ridgeway
s) and rail tracks
often follow divides to minimise grades (gradients), and to avoid marshes and rivers.
A divide is also known as:
A valley floor divide is a low drainage divide running across a valley, sometimes created by deposition or stream capture.
Drainage divides are a hindrance to river navigation
. In pre-industrial times water divides were crossed at portage
s. Later, canal
s were built to connect the adjoining drainage basins.
North America
North America is a continent wholly within the Northern Hemisphere and almost wholly within the Western Hemisphere. It is also considered a northern subcontinent of the Americas...
) watershed is the line separating neighbouring drainage basin
Drainage basin
A drainage basin is an extent or an area of land where surface water from rain and melting snow or ice converges to a single point, usually the exit of the basin, where the waters join another waterbody, such as a river, lake, reservoir, estuary, wetland, sea, or ocean...
s (catchments). In hill
Hill
A hill is a landform that extends above the surrounding terrain. Hills often have a distinct summit, although in areas with scarp/dip topography a hill may refer to a particular section of flat terrain without a massive summit A hill is a landform that extends above the surrounding terrain. Hills...
y country, the divide lies along topographical
Topography
Topography is the study of Earth's surface shape and features or those ofplanets, moons, and asteroids...
peaks
Pyramidal peak
A pyramidal peak, or sometimes in its most extreme form called a glacial horn, is a mountaintop that has been modified by the action of ice during glaciation and frost weathering...
and ridge
Ridge
A ridge is a geological feature consisting of a chain of mountains or hills that form a continuous elevated crest for some distance. Ridges are usually termed hills or mountains as well, depending on size. There are several main types of ridges:...
s, and may be in the form of a single range of hills or mountain
Mountain
Image:Himalaya_annotated.jpg|thumb|right|The Himalayan mountain range with Mount Everestrect 58 14 160 49 Chomo Lonzorect 200 28 335 52 Makalurect 378 24 566 45 Mount Everestrect 188 581 920 656 Tibetan Plateaurect 250 406 340 427 Rong River...
s (known as a Dividing range), but in flat country (especially where the ground is marsh
Marsh
In geography, a marsh, or morass, is a type of wetland that is subject to frequent or continuous flood. Typically the water is shallow and features grasses, rushes, reeds, typhas, sedges, other herbaceous plants, and moss....
y) the divide may be invisible – just a more or less notional line on the ground on either side of which falling raindrops will start a journey to different river
River
A river is a natural watercourse, usually freshwater, flowing towards an ocean, a lake, a sea, or another river. In a few cases, a river simply flows into the ground or dries up completely before reaching another body of water. Small rivers may also be called by several other names, including...
s, and even to different sides of a region or continent
Continent
A continent is one of several very large landmasses on Earth. They are generally identified by convention rather than any strict criteria, with seven regions commonly regarded as continents—they are : Asia, Africa, North America, South America, Antarctica, Europe, and Australia.Plate tectonics is...
.
Drainage divides are important geographical
Geography
Geography is the science that studies the lands, features, inhabitants, and phenomena of Earth. A literal translation would be "to describe or write about the Earth". The first person to use the word "geography" was Eratosthenes...
, and often also political
Politics
Politics is a process by which groups of people make collective decisions. The term is generally applied to the art or science of running governmental or state affairs, including behavior within civil governments, but also applies to institutions, fields, and special interest groups such as the...
boundaries
Border
Borders define geographic boundaries of political entities or legal jurisdictions, such as governments, sovereign states, federated states and other subnational entities. Some borders—such as a state's internal administrative borders, or inter-state borders within the Schengen Area—are open and...
. Road
Road
A road is a thoroughfare, route, or way on land between two places, which typically has been paved or otherwise improved to allow travel by some conveyance, including a horse, cart, or motor vehicle. Roads consist of one, or sometimes two, roadways each with one or more lanes and also any...
s (such as ridgeway
Ridgeway (track)
Ridgeways are a particular type of ancient road that exploits the hard surface of hilltop ridges for use as unpaved, zero-maintenance roads, though they often have the disadvantage of steeper gradients along their courses, and sometimes quite narrow widths. Before the advent of turnpikes or toll...
s) and rail tracks
Rail tracks
The track on a railway or railroad, also known as the permanent way, is the structure consisting of the rails, fasteners, sleepers and ballast , plus the underlying subgrade...
often follow divides to minimise grades (gradients), and to avoid marshes and rivers.
A divide is also known as:
- A watershed, the line between drainage basins – shedding is an old term for splitting or dividing, so it is the line which divides the water (however in North AmericaNorth AmericaNorth America is a continent wholly within the Northern Hemisphere and almost wholly within the Western Hemisphere. It is also considered a northern subcontinent of the Americas...
"watershed" has come to mean the drainage basin itself); - a water parting;
- a height of land (in CanadaCanadaCanada is a North American country consisting of ten provinces and three territories. Located in the northern part of the continent, it extends from the Atlantic Ocean in the east to the Pacific Ocean in the west, and northward into the Arctic Ocean...
).
A valley floor divide is a low drainage divide running across a valley, sometimes created by deposition or stream capture.
Types
Drainage divides can be grouped in three types:- Continental divideContinental divideA continental divide is a drainage divide on a continent such that the drainage basin on one side of the divide feeds into one ocean or sea, and the basin on the other side either feeds into a different ocean or sea, or else is endorheic, not connected to the open sea...
- A divide in which the waters on each side flow to different oceans (example: the Nile and CongoCongo RiverThe Congo River is a river in Africa, and is the deepest river in the world, with measured depths in excess of . It is the second largest river in the world by volume of water discharged, though it has only one-fifth the volume of the world's largest river, the Amazon...
divide, Lunghin Pass triple divide)- Major drainage divide
- The waters on each side of the divide never meet again, but do flow into the same ocean (example: the divide between the Yellow RiverYellow RiverThe Yellow River or Huang He, formerly known as the Hwang Ho, is the second-longest river in China and the sixth-longest in the world at the estimated length of . Originating in the Bayan Har Mountains in Qinghai Province in western China, it flows through nine provinces of China and empties into...
basin and the YangtzeYangtze RiverThe Yangtze, Yangzi or Cháng Jiāng is the longest river in Asia, and the third-longest in the world. It flows for from the glaciers on the Tibetan Plateau in Qinghai eastward across southwest, central and eastern China before emptying into the East China Sea at Shanghai. It is also one of the...
)- Minor drainage divide
- The waters part but eventually join again at a river confluence (example: the MississippiMississippi RiverThe Mississippi River is the largest river system in North America. Flowing entirely in the United States, this river rises in western Minnesota and meanders slowly southwards for to the Mississippi River Delta at the Gulf of Mexico. With its many tributaries, the Mississippi's watershed drains...
and MissouriMissouri RiverThe Missouri River flows through the central United States, and is a tributary of the Mississippi River. It is the longest river in North America and drains the third largest area, though only the thirteenth largest by discharge. The Missouri's watershed encompasses most of the American Great...
divide)
Drainage divides are a hindrance to river navigation
Navigation
Navigation is the process of monitoring and controlling the movement of a craft or vehicle from one place to another. It is also the term of art used for the specialized knowledge used by navigators to perform navigation tasks...
. In pre-industrial times water divides were crossed at portage
Portage
Portage or portaging refers to the practice of carrying watercraft or cargo over land to avoid river obstacles, or between two bodies of water. A place where this carrying occurs is also called a portage; a person doing the carrying is called a porter.The English word portage is derived from the...
s. Later, canal
Canal
Canals are man-made channels for water. There are two types of canal:#Waterways: navigable transportation canals used for carrying ships and boats shipping goods and conveying people, further subdivided into two kinds:...
s were built to connect the adjoining drainage basins.
See also
- Watersheds
- List of watershed topics
- European WatershedEuropean WatershedThe European Watershed is the line which divides the drainage basins of the major rivers of Germany: the Rhine, which originates in the Swiss Alps and empties into the North Sea via the Netherlands, and the Danube, which originates in the Black Forest and flows eastward emptying into the Black...
- Scottish watershedScottish watershedThe Scottish watershed is the drainage divide in Scotland which separates river systems that flow to the east from those that flow to the west. On the summit of Ben Lomond for example, looking west all water flows to the Firth of Clyde, and looking east all water flows into the Firth of...
- Drainage basinDrainage basinA drainage basin is an extent or an area of land where surface water from rain and melting snow or ice converges to a single point, usually the exit of the basin, where the waters join another waterbody, such as a river, lake, reservoir, estuary, wetland, sea, or ocean...
- Source (river or stream)Source (river or stream)The source or headwaters of a river or stream is the place from which the water in the river or stream originates.-Definition:There is no universally agreed upon definition for determining a stream's source...
(headwater) - Mountain passMountain passA mountain pass is a route through a mountain range or over a ridge. If following the lowest possible route, a pass is locally the highest point on that route...