This is still such an incredible story it is difficult to even understand what is going on here.
My father worked at some mines in West Virginia for Dow Chemical. The locals often spoke of discovering passages in coal mines that looked like they were cut for little people to run through. Every once in a while somebody even reported seeing one of these little people coming or going. Some miners said that after blasting they had sometimes found what were hairless monkeys with strangely human features in the rubble and the company had told them to keep it under their hat. (Environmentalists would have shut them down and they would never be permitted to mine there again.)
The Cherokee believed there were little people running around underground all over North America.
Some people have suggested that when they find bones of these creatures that are recent, they get rid of them by pushing them into the past so far they cease to be a threat to our orthodoxy.
It is possible that the biggest problem for scientific advancement is that every time we discover something really interesting, we also discover that we cannot accept this new paradigm because it destroys so many others we will lose our bearings given what we currently believe.
I'm not saying I really believe in the Little People. I'm saying the story above is literally weirder than most human brains can even absorb in it's implications.
These aren't water channels. They show signs of being dug by hand or with stone tools. The question is who dug these out and why.