One of the spillways, seen on the right. The spillways set the maximum water level of the lake, and have only been used once, due to heavy snowmelts in the 1980s. Water from the spillways goes into tunnels, with outlets at water level downstream from the dam.

Our tour guide explains the water flow through the dam. The map includes intakes (to the right of the dam), spillways, tunnels which feed the generators and flood control outlets, and the tunnels for the spillways. Tunnels were also used to divert the river while the dam was being built; these are the outermost pairs of tunnels at top and bottom. The drawing shows the old riverbed.

Inside the diversion tunnels, looking at the pipe from the spillway on the Nevada side. The rings on the left are not the pipe itself, but concrete reinforcing and isolating rings around the pipe, installed to protect the pipe from earthquakes. The plastic sheeting around the top of the tunnel diverts seepage away from the pipe. You can hear a lot of water down here, but it's all seepage; the pipe itself is empty, as it is used only for flood control.

The needle valves, which control deliberate releases of water (as opposed to the spillways). When water is deliberately released, it flows from the intake towers and through the same set of penstock tubes which feed water to the generators.

The old outlets from the needle valves. These are now sealed permanently shut; when water needs to be released from the lake, it flows out through the old diversion tunnels. There are very spectacular pictures of water spraying out from these outlets, but they have only been used for testing.

Looking downstream on the Colorado River, which has now been controlled. Flooding on the river was the sole reason for building the dam; power generation was secondary. This picture was taken at the lower end of the power generating station.