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SWATArc View interface, and project generated maps and tables Neitsch et al., 2005.
MapWindow is an open source Programmable Geographic Information
System that supports manipulation, analysis, and viewing of geospatial data and
associated attribute data in several standard GIS data formats. MapWindow is a
mapping tool, a GIS modeling system and a GIS application programming interface API all in one convenient redistributable open source solution Usman et al, 2008
and Gatry et al, 2007.
The MapWindow application is a free, extensible geographic information
system GIS that can be used in many ways:
•
As an open-source alternative desktop GIS
•
To distribute data to others
•
To develop and distribute custom spatial data analysis tools
2.5 Calibration and Validation
Calibration is testing of the model with known input and output used to adjust or estimate factor. The model calibration procedure can be either manual or
auto-calibration; the manual calibration depends to knowledge, experience and patience. Validation is a comparison between simulation and the observed data on
time step with the use of several indexes, and mainly in Nash and Sutcliffe coefficient. The Nash and Sutcliffe coefficient is an estimate of the variation of a
time series from another, provided by equation; ∑
, ,
∑
, ,
Where; Q
sim
= Simulation time series Q
Obs
= Observe time series Q
sim
= the numerical mean for simulation time series A Nash and Sutcliffe coefficient can approach identifying that the simulation
is almost identical to the observed data Nash and Sutcliffe, 1970 in Pikounis M. et al
, 2003.
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2.6 GIS and Remote Sensing in Hydrology model
Remote sensing and Geographic Information Systems GIS are providing new tools for advanced ecosystem management. The collection of remotely sensed
data facilitates the synoptic analyses of earth-system function, patterning, and change at local, regional, and global scales over time. Such data also provide a vital
link between intensive, localized ecological research and the regional, national, and international conservation and management of biological diversity Mansouri and
Mazouz, 2007. GIS is a special type of information system in which the data source is a
database of spatially distributed features and procedures to collect, store, retrieve, analyze, and display geographic data. In other words, a key element of the
information used by utilities is its location relative to other geographic features and objects Shami, 2002 in Weizhe, 2007.
Digital Elevation Model DEM and Grid format SWAT model need DEM data as input for delineating the catchment
boundary, sub-catchment and stream network. DEM is digital representation of ground surface and also known as a digital terrain model DTM. DEM can be
visualized as a raster squared grid or a Triangular Irregular Network TIN. DEM are commonly developed using remote sensing technique or land surveying.
The grid model is simpler and more efficient to process than other models. Elevation data in grid model is relatively abundant and inexpensive. TIN represent
surface using contiguous, non overlapping triangle facets. One can estimate surface values anywhere in the triangulation by averaging node value of nearby triangles,
giving more weight and influence to those that are closer. The resolution of TIN can vary; they can be more detail in area where the surface is more complex and less
detail area where the surface is simpler.
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III. METHODOLOGY
