An experimental high-flow release from Glen Canyon Dam next month is not expected to negatively impact the world-renowned Lees Ferry trout fishery downstream in Marble Canyon, according to Arizona Game and Fish officials.
Larry Riley, an Arizona Game and Fish Department biologist, said the proposed peak flow of 41,000 cubic feet per second would mean an increase of about four feet at the Lees Ferry boat ramp.
"Wild trout are well adapted to stream conditions that include spring flushing flows," he said. "The proposed test flows could temporarily displace adult rainbow trout by changing water currents.However, the rainbow trout are unlikely to leave the immediate area and fish will return to desirable habitats rather quickly."
A decision by the Department of the Interior is anticipated in late February, with plans to conduct the high flow in early March if there is a decision to move forward with the experiment.
The proposed 41,000 cfs flows would be about four times the average flow in recent years; however it's perhaps a third of the historic pre-dam spring peak flows of around 120,000 cfs and less than half of the peak flow during spill operations in 1983.
To put all that in perspective, in late January this year the Salt River was flowing at around 80,000 cfs into Roosevelt Lake.
The timing of this high-flow event is at the beginning of the growing season when sunlight is returning to the canyon bottom, and the aquatic algae is poised to exploit the space, increasing sunlight, and available nutrients to grow and expand rapidly.
"The experimental flows could trim the important alga beds of dead and aging fronds, just like trimming an aging tree, and could in fact create a bumper crop of high-quality food for trout." Riley said.
Another concern by anglers is that the trout won't be catchable after this high flow.
"Angler catch rates really did not change significantly as a result of the 1996 experiment. Fish behavior may shift following this event, but it shouldn't take long for anglers to adapt - it never does," Riley said.