Mmmmm, but it could be contaminated. I was a Boy Scout when I was younger, I would know. I remember my leader telling me that there could be some animal taking a crap in the water upstream, so I never drank the water downstream.
Oh, and bears are really fast, just saying. Like, the running speed of a grizzly bear is about 35 MPH, and the fastest man alive only runs 27 MPH. So yeah, good luck with that.
Actually, there are only certain bears who can climb trees. Not counting pandas, only black bears can climb trees. However, this bear seems to have long claws, so it might be able to climb the tree. I would try to climb the tree, since it is not likely that it could climb after you. But...