I have a weird phenomenon going on in QGIS.
I want to derive a channel network and also the catchment areas using "watershed basin" from SAGA. In the end I want to have the flow direction and flow accumulation. I created a small DEM and I also got a few raster layers from open web data to have a bit of context and orientation/information in my DEM. As you can see in the picture, I also have a hydrographic network raster layer which shows me all the channels etc.
As you can see, there is a lake in the middle and I think because of the lake the algorithm calculates the watershed basin very very wrong. Flow direction seems to be right.
Do you know a workaround regarding this problem?
I also tried to work with Strahler Order but the DEM size is too small for it, so its very faulty