Best to bring a torch along as you will pass through a few long dark tunnels along the way... (lest you want to hang out in the dark with the bats.......)
As you head up into the river valley, you will find that there is a small hydroelectric dam and water reservoir just east of Longjian........
You will see a few hydro plants in the valley, where they divert water through pipes from high up in the mountains down through turbines for power.
Though that means less waterfall action in the valley, I guess that is better than coal burning power plants.
Favorite thing: Be advised that this whole area is restricted. You will need to stop in Tongmen and pay a small fee and register to enter the valley. After registering continue west along the riverside road and hand the registration form to the guard at the toll gate.