I routinely drove across the Hoover Dam in the late 1990's and marveled at the water crashing over the spillways. The rings were present even then, albeit not very wide.

To manage the water level, a release was performed for the first time in the dam's history and it was spectacular. That was only 20+ years ago.

It is my understanding that the U.S. Bureau of Reclamation is having a very difficult time managing the water levels of Mead, Powell, Glen Canyon, and the upper Colorado. Not only due to drought but to the ever-increasing demand being placed on the system from development, agriculture, and inadequate conservation.

The potential inability to produce hydroelectric power is yet another wake-up call that things are changing fast.