Watershed
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Watershed has more than one meaning:
- In physical geography, watershed has two distinct meanings:
- * A watershed can be a drainage basin, especially in North American usage. This is the region of land whose water drains into a specified body of water.
- * A watershed can be a drainage divide, especially in Britain and other Commonwealth countries. This is the ridge of land that separates two adjacent drainage basins.
Etymology of watershed
The first recorded instance of the term watershed was in 1803. The definition ascribed is as a dividing line between two river basins (water divide):
- "Strathcluony..is a very high inland tract, being the water-shed of the country between the two seas."Oxford English Dictionary
The term soon developed an alternate and closely related meaning as "the slope down which the water flows from a water-parting,"Oxford English Dictionary, which corresponds to the area of surface runoff, and excludes channel flow. This meaning was ascribed to the following quote:
- "To the south~west of Kington the lower beds of the Old Red Sandstone..have been the sub-aqueous water-shed, down which the coarse detritus has been swept."Sir Roderick Impey Murchison, The Silurian system, founded on geological researches, (1839)
- "To avoid all ambiguity it is perhaps best to set aside the original meaning of ‘watershed’, and employ the term to denote the slope along which the water flows, while the expression ‘water-parting’ is employed for the summit of this slope". T.H. Huxley, Physiography: An Introduction to the Study of Nature, (1877)
- "The Missouri Region, in its broadest sense, as embracing the whole water~shed of that great river and its tributaries."Elliott Coues, Birds of the Northwest, (1874)
- "Midnight! the outpost of advancing day!.. The watershed of Time, from which the streams of Yesterday and To-morrow take their way.Henry Wadsworth Longfellow, Kéramos, and other poems", (1878)
References
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