That area is a cold spring, known as "Hidden Canyon". The growth covers the majority of the spring area and runnoff. When I last visited that area, there was MUCH wildlife in the area using it for water and dens.
The lower end of that waterflow is intersting though, when you decend down to the base of the first hill (Mofo) and before getting to the 4x4 road, you can hang a quick right around those rocks and back toward that valley. There is an old metal cannister that the water fills for a horse trough, but from there the water flows back underground. Check it out next time you go, but I do NOT recommend trying to find that source unless you want to meet a pack of wild dogs or possibly a local cat.
Happy Hunting.