Here a good example and tutorial from youtube for watershed delineation and river formation using digital elevation model (DEM).
The steps as follows:
Watershed delineation
1. Spatial analysis tools
-> hydrology
-> fill
-> flow direction
-> flow accumulative
-> basin (using input from flow direction)
2. Conversion tools
-> from raster
-> raster to polygon (using input from STEP1-basin)
Clip the selected watershed
3. Geoprocessing
-> Clip (select watershed that want to clip)
River formation
4. Spatial analysis tools
-> map algebra
-> raster calculator
-> flow accumulative > 500 (value is example)
-> flow accumulative > 1000 (value is example)
5. Conversion tools
-> from raster
-> raster to polyline (using input from STEP 4-flow accumulative>1000)
-> Clip
Clip the DEM raster
6. Data management tools
-> raster
-> raster processing
-> clip (input (raster), output extend (basin, STEP3), click used input feature for clipping geometry)