For the water to leave the lake, as you can see in the picture below, it rolls down the river to the waterfall to the canyon below.
Here above we see the view of the spillway from the lake down to the the canyon.
Now we can see close up the first stages of the river to the spillway as it was being built.
Then we see the copper finish being added on the riverbed.
The copper will soon tarnish and naturalize in its look, blending with the wood and the coming water as it spills down into the canyon below. We won’t see this until we fill the lake with water.
Above is a wider shot of the spillway, with the canyon in the forefront. Take a look. The riverbed under construction is in the right center of the picture. It’s about a third of the way down the photograph.