How to delineate watershed using QSWAT

1. Watershed
Delineation
Using QSWAT

2. Raster Analysis
• represent a continuous variable in space such
as
• elevation,
• precipitation,
• noise,
• satellite images or product generated.

3. Watershed delineation needs an outlet
and DEM
Outlet
• bring XY
• Add to QGIS
• Convert to shape file
DEM
• Download

4. How WS delineated from DEM
• Fill
• Flow direction
• Flo accumulation
• Slope ,
• Aspect,
• Hill shade …
• Such delineation is a physical based ( not Hydrological)
• It relay on Elevation

5. Fill/sink
• A pit is a set of one or more cells which has no
downstream cells around it
• Unless these pits are removed they become sinks
and isolate portions of the watershed

6. Flow direction
calculates the direction water will flow using
slope from neighboring cells.
Direction of steepest descent

8. Flow Accumulation
Area draining in to a grid cell

9. Channel and Watersheds – Stream Definition

10. Outlet
If the out let is sown find the area of he
watershed

11. Watershed boundary
contributing area convention.

12. • Solution
• Open Excel
• Write column headings
• add the corresponding values
• Save in CSV
• Open QGIS and add to QGIS
• Export to shape file
• Where the WS outlet lies?
• Out let given
• X: 395065
• Y: 1313419
• CS: WGS UTM Zone 37

13. Extraction
• Clipping raster my masking layer
• Clip raster by extent

14. Examine the DEM and roughly determine the WS boundary

15. Clipping a raster
1. Go to Raster | Extraction | Clip Raster by
Extent | Clip Raster by Mask Layer.
For Our case we hall to use clip
Raster by Mask

16. Install
• find the compatible version for your QGIS version
• Be sure you have install the appropriate MS Office bits
• Make your outlet ready in shape file
• Open QGIS
• Go to Plugins > Manage and Install Plugins as shown here:

17. Start QSWAT
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20. Add your outlet and zoom to it
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23. Open attribute Table 
Select All
Save the dialogue box
Merge
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