- For a term related to television programmes, see watershed (television).
A watershed is the region of land that drains into a specified body of water, such as a river, lake, sea, or
ocean. Rain that falls anywhere within a given body
of water's watershed will eventually drain into that body of water. A nice map of the primary watersheds in the world can be
found at [1]
The term can also mean the topographical dividing line between these
drainage basins: watersheds usually run along mountain ridges.
Each area of a drainage basin has its own drainage system.
Watersheds in ecology
Watersheds constitute a very important type of ecoregion. They do things such
as provide habitats for animals, lessen flooding, and prevent erosion. Pollution anywhere within the watershed can potentially
affect life anywhere downstream from it.
Watersheds in politics
Watersheds have been important historically in determining 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 Indian trade in the entire Hudson Bay watershed, an area called Rupert's Land. The company later acquired the North American watershed of the Arctic Ocean (the North-Western
Territory). These lands later became part of Canada as the Northwest Territories, making up the majority of Canada's land
area.
Today, bioregional democracy can include agreements of
states in a particular watershed to defend it. These include the Great Lakes Commission, which deals with the largest fresh watershed in the world.
Ocean watersheds
One can divide up the world among the watersheds of the oceans and largest seas.
The Atlantic Ocean watershed consists of the Saint Lawrence River and Great Lakes watersheds, plus the Eastern
Seaboard, Canadian Maritimes, Newfoundland and Labrador in North America; nearly all of South America (that portion east of the Andes); northern Europe; and the greatest portion of western Sub-Saharan Africa.
The Caribbean Sea watershed consists of all of the American interior (the Louisiana Purchase, which involved the watershed of the Mississippi River); eastern Central America;
and far northern South America.
The Mediterranean Sea watershed consists of much of
northeastern Africa, including Egypt, Libya, and Sudan (the Nile watershed), as well as southern and eastern Europe, Turkey, and the
Levant.
Of course, the previous two can be considered part of the Atlantic watershed, since the Caribbean Sea is part of the Atlantic
ocean, and the Atlantic drains into the Mediterranean due to its higher evaporation.
The Indian Ocean watershed consists of the eastern coast of Africa, the
coasts of the Red Sea and the Persian Gulf, the Indian subcontinent,
Burma, and most of Australia.
The Pacific Ocean watershed consists of much of China, southeastern Russia, Japan, Korea, most of Indonesia and Malaysia, the Philippines, the rest of the Pacific islands, and the northeast coast of Australia; as well as Alaska, British Columbia, the
western United States and Central America, and the coast of South America
(the smaller portion west of the Andes).
The Arctic Ocean watershed consists of the aforementioned Rupert's Land,
and most of the territory of Russia.
In addition to the oceanic watersheds, a portion of the Earth's land surface consists of inland basins, which drain into no
ocean. The largest of these consists of much of the interior of Asia, and drains into the
Caspian Sea and the Aral Sea.
Other basins include the Great Basin in the United States, much of the
Sahara Desert, the watershed of the Okavango River, highlands near the African
Great Lakes, the interiors of Australia and the Arabian
Peninsula, and parts in Mexico and the Andes.
See also
External links
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