In EoTW Shadar Logoth is shown being west of a River. I don't have my book with me at the moment, but I think its the Eldar. Anyway, the name doesn't matter. What does is that its supposed to be west of it.

 

 

Yet, in the BWB the nation of Aridhol doesn't reach west of that main river. Its all north and east of it. So how is the capitol of that country west of it?

I've never had the BWB but isn't it possible for rivers to change course?

 

Hopefully that answers your question.

The map in the BWB doesn't show the border drooping below the river. So, I guess it was just an error in the BWB.