Watershed Analysis Using DEMs and GIS Techniques (Especially for GATE-Geospatial 2022)

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A watershed is the area of land where that falls in it and drains off of it goes into the same place or common outlet. A watershed is also defined by topographic divides between two or more adjacent catchment basins, such as a ridge or a crest.

Picture Shows Watershed Analysis in GIS

In simple words watershed is a region of land with which water flows down into a specified body, such as a river, lake, sea, or ocean; a drainage basin. Watershed used interchangeably with drainage basin or catchment. Ridges and hills that separate two watersheds are called the drainage divide.

Picture Shows Watershed Schematic

Watershed analysis refers to the process of using DEM and raster data operations to delineate watersheds and to derive features such as streams, stream network, catchment areas, basin etc.

Traditionally, watershed boundaries are drawn manually onto a topographic map. Today computer programs are also used to derive watersheds from DEMs. Using computer technology, we can generate preliminary watershed boundaries in a fraction of the time needed for the traditional method.

Delineation of watershed can also be area-based or point-based. An area-based method divides a study area into a series of watersheds, one for each stream section. A point-based method, on the other hand, derives a watershed for each select point. The select point may be an outlet, a gauge station, or a dam.

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