Using QGIS,I attempted Africa's watershed delineation taking the following steps:
- Downloaded DEM from earthexplorer USGS (GTOPO30)
- Created a mosaic of the downloaded DEM
- Reprojected the mosaic DEM to EPSG:54010 World_Eckert_ VI(For equal area world map projections)
- Rescaled map cell size to 1km by 1km(For faster processing time) using the Align Rasters function
- Filled depressions using Wang & Liu XXL algorithm -Created stream order using strahler order function
- Choose strahler order threshold using raster calculator function
- Created the basins and channels using SAGA channel network and drainage basins function
The output (Picture 1) do not look satisfactory.
How do I improve the results?
The goal is to have a clearly delineated River Niger Basin- the basin with thickened blue border line in picture 2