As I said yesterday, I decided to limit the semantics of batlaam to only include larger rivers, simply out of personal preference. So, today, I decided to make another term for the semantic space that's left by that.
bun ni stream, creek, tributary
As suggested by "stream" and "creek", bun is usually for much smaller bodies of water than batlaam. However, in the sense "tributary", it can be quite large. Thus, if it is used to describe a body of flowing water in isolation, that's likely a small, easily fordable stream, but if it is referring a body of water that flows into another, it could be quite large.
Sometime when I'm not fiendishly busy with other things, I will work out some examples.