Re: Any idea what this was for?

I hope I added the photo right...

For years I've gone up and down the Vernal Falls trails and have seen this "dam" on the other side of the river. My mom's only guess is that this may have been an area they mined for gold in the early years, though it looks more modern then that. Anyone have any ideas? Any old maps that might show it? It is found over looking the stone wall when the trail turns toward the falls...

Old diversion dam for the water supply for the valley. It's not used any more.
My understanding is that all the water for the valley comes from 3 wells in the valley that is then pumped to the huge green water tank that is near where that shot was taken. If you take the road behind the Happy Isles bathrooms you'll end up at the water tank. The Horse trail goes along the road and then continues past the water tank. It crosses the IllIlouette creek on a couple of bridges. This is also where'd you go if you were wanting to explore getting up the Illilouette gorge.
The water used to be diverted from the Merced River by the dam in the picture. Most of the dam and piping have long ago been removed.
One of the reasons the water tank is so large is so they'll have enough water to fight any large fires in the valley should one occur.

qumqats~ thanks for the info..love learning about the parks history. Definately one to add to seeing something new.

I can't speak for the concrete, but that is definitely a valve wheel/handle and a stem sticking up out of it. I believe qumqats is right and the pipe was removed, but the concrete, stem and handle/wheel were left behind. It's tough to judge the size from the picture, but I'm pretty sure that it would have been at least a 12" pipe, if not closer to 20" (I'm guessing that the rungs for the ladder on the concrete wall are either 12" or 18" apart).