The water doesn't look good
You find your way to a thick forest. You can hear the sound of running water on the other side of the trees. So you start to hike to find the water. There are large trees and branches everywhere, hitting your face, your arms, and your legs. Despite the dense growth, you can sense the beaten down plants at your feet. Although overgrown, there was evidence of a path here at one time. So you continue along the path.
Soon you can see a clearing in front of you. The trees start to thin out, and walking becomes more bearable. Eventually you emerge into a relatively clear area where you can see a pool of water. This water has formed off of the main river. You continue along the pool to spot the source of the water. As you are walking along the shore of the pool, you can see that there is a strange red glow shimmering in the water. You then look up and see a red streak across the sky. Puzzled you hurry to the tree line. Without an explanation, your only option is to continue following the water.
After some time of exploring you finally find the source of the water. It is not a river, but rather a water drain from the city. You can see the outline of buildings through the tree line above you. The water itself is coming out of a large tube, one that can easily fit a couple of people. The water looks clear despite coming out of a drain. In fact it looks too clear, there is no dirt or grime as far as you can see.