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The watershed area can then be estimated using a planimeter, by overlaying graph paper and counting grid cells, or the result can be digitized for use with mapping software. The same process can be done on a computer, sketching the watershed boundary (with a mouse or stylus) over a digital copy of a topographic map. [ 1 ]
Subsequently every watershed along this coast is assigned a number using the Pfafstetter Coding System. This implies that the four largest watersheds are selected and receive numbers 2,4,6, or 8. The watersheds in between the large systems receive numbers 3, 5, and 7. Numbers 1 and 9 are used for the small watersheds on the edges of the strait.
These areas can still be included in topographically defined basins if the hypothetical flow of water (or ice) over the surface of the ground (or ice sheet) is considered. For example, the Antarctic ice sheet can be divided into basins, [ 1 ] and most of Libya is included in the Mediterranean Sea basin even though almost no water from the ...
Each subregion includes the area drained by a river system, a reach of a river and its tributaries in that reach, a closed basin or basins, or a group of streams forming a coastal drainage area. [6] Regions receive a two-digit code. The following levels are designated by the addition of another two digits. [7]
A hierarchical watershed transformation converts the result into a graph display (i.e. the neighbor relationships of the segmented regions are determined) and applies further watershed transformations recursively. See [18] for more details. A theory linking watershed to hierarchical segmentations has been developed in [19]
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 , [ 1 ] made up of a succession of elevated features, such as ridges and hills .
Most lakes are not actually endorheic, but endorheic basins may not have standing water, or have water only seasonally. The most significant endorheic basins are these: Great Basin covering most of Nevada, the western part of Utah, and smaller amounts of other U.S. states; Great Divide Basin on the Continental Divide in Wyoming; Guzmán Basin
The water that enters a high-drainage watershed during a storm will reach a channel relatively fast and travel in the high-velocity channels to the outlet of the watershed in a relatively short time. Conversely, the water entering a low drainage density basin will, on average, have to travel a longer distance over the low velocity hillslope to ...