Tpitsch of the three, the susnset with tracks reflecting is the winner.. Really nice composition, perhaps a longer exposure would of yielded you more of the water being silkier.
As for the stilted shed out in nature, it looks like it might be a blind for wildlife. A early morning sunrise/ foggy atmosphere or sunset would make it a lot more interesting, as would when the leaves change. Think about shooting it with those thoughts in mind, and you should walk away with a keeper.
As for the waterfall, if there are rocks out in the middle, where you could get the waterfall staight on, that would be the shot. However that may or may not be possible.
So lets talk about your the vantage point you were shooting from, first I would of gotten my tripod as low to the ground, as to make the rocks the foreground impact feature, and the waterfall the focal point. I would try it both in Portrait ( not needing to get the entire waterfall in the frame perhaps some trees and sky as well) and in landscape without the pipe in the composition. It's not always necessary to get the entire waterfall in the frame to be impactful. Also think about a fall shot with the foliage changing colors, and perhaps incorporate it into the composition.
Thank you for posting, keep shooting !!