Chris Cutler of the office said that when the water level in the reservoir gets too close to the level of the inlet structures for the dam’s turbines, it starts creating a whirlpool-like vortex that draws in air and debris like equipment or even fish that are can be very damaging to the turbines.
Nobody knows exactly at what water level such cavitation can occur, said Kuhn and Cutler. Cutler leads the water and electricity services division for the Upper Basin office in Salt Lake City.
The purpose of keeping Powell at 3,525 was to keep a cushion above 3,490 to prevent cavitation, said Kuhn, retired general manager of the Colorado River District in Glenwood Springs.
The US Bureau of Reclamation has begun a six-month effort to raise Lake Powell 3 feet by the end of 2021 by releasing 181,000 acres of water from three upstream reservoirs.
Wayne Gustaveson
“Nobody knows how turbines will work at 3,490. As far as I know, there is little risk of cavitation. Even a small risk is something very, very serious, ”said Kuhn.
Cutler said that if the lake falls anywhere below 3,525 but above 3,490, there is little possibility of cavitation because “there is always the possibility of an unforeseen vortex problem from new equipment we have installed” in the turbines. He did point out, however, that the 3,525 level is 35 feet above the level at which they are most concerned, a vortex of air entering the turbines and causing cavitation.
If more water is needed to support Powell in the future, the office could potentially move 1 million to 2 million more acres into the lake from the Upper Basin reservoirs over the next two years, he said. However, a long-term plan would have to be drawn up in cooperation with the Upper Basin states, he said.
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