The location is not far away from the spring of this river. It is very typical for limestone mountains where a lot of water gets in the karstic ground. This river can grow rapidly when there`s heavy rain though, you'd better not be there then.
Yeah, I could tell by the height of the fallen trees that it is a stream where the flow varies quite a bit. That's why I thought it was dammed up. It's great to see that there's still a few (relatively) untouched places left. Incidentally, I'm going fishing tomorrow.