Aveneu Park, Starling, Australia

The entire stream system. Point-based and area-based

The
area which drains surface water to a common outlet forms a watershed. Hydrological
term that is used for the planning and management of water resources is called watershed.
Traditionally, the boundaries of watershed are delineated manually onto a topographic
map but computer software and programs are used for delineation of watersheds
using Digital Elevation Models. We can generate preliminary watershed boundaries
in a very short interval of time using geographic information system as
compared to traditional method. The flow of water in downslope direction is the
fundamental principle in water shed analysis. Watershed delineation can be
applied to the images of different spatial scales. A large watershed can
consist of the whole stream system and many smaller watersheds can be there for
smaller tributaries in the entire stream system.

Point-based and area-based
are the types of watershed delineation. The study area is divided into a series
of watersheds in area-based delineation. Whereas the point- based is the
delineation of the watershed for each select point. The selected point may be
an outlet, gauge station or a dam. The same series of steps are applied for
both the types.

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Accurate
delineation of a watershed is very important for the management of watershed.
Management efforts such as analyzing land use, land change, soil types, geology
and river flows are dependent upon the proper delineation of the features so
that the appropriate conclusion can be drawn. By the Digital elevation model
(DEM) a series of additional grids are produced that represent various
hydrological properties of the landscape. From these hydrological grids a
Geographic information System can delineate watershed boundaries by identifying
all location within a DEM that are uphill of an outlet. Study area consist of
the region which drain Mangla dam. Mangla dam is constructed on Jhelum River in
Pakistan.

Using GIS, study has
been done on watershed delineation of ashok nagger in Madhya pardesh India for
water resource management. The use of Digital elevation model for watershed
analysis was the focus in the study.  Watershed
delineation of amazon sub basin system using DEM was conducted in 2009. By the
use of GIS application the watershed characterization of wadi aurnah western
Arabian Peninsula was done. It provides detailed information on the
geomorphological setting of the catchment and its hydrological characteristics.

The
Normalized Difference Water Index (NDWI) is an algorithm that is developed for
water features to enhance their presence in remotely-sensed digital imagery.
The NDWI method uses the Short Wave Infrared and Near Infrared bands to enhance
the water bodies on the surface. It is observed that the (NDWI) may also
provide the turbidity estimations of water bodies to researchers with the use
of remotely sensed data. The (NDWI) is a suitable method for drawing water
features. The water features can be enhanced more efficiently in most of the
cases by the normalize difference water index. It is delicate to built-up areas
and often results in over-estimation of water bodies.

The aim of the study
is to investigate and demonstrate GIS application for watershed delineation of
Mangla basin and use of NDWI index for enhancing water body in the region and
calculating the area of lake of output image using measure tool.

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