Such marquee rapids on the Grand as Hance, Horn Creek, Hermit, Crystal and Lava Falls had a little more meat to them this month as the Department of Interior conducted a high flow experimental release from Glen Canyon Dam November 10-15…
Under the protocol, high flow releases linked to sediment input and other resource conditions below Glen Canyon Dam were increased up to full power plant capacity of about 22,500 cfs on Nov. 10. Later, bypass tubes at Glen Canyon Dam were opened and releases continued to increase up to 37,500 cfs by that evening.
Paddlers on the river during that time saw freakishly high levels for that time of year.
The releases were maintained at peak release for four days before ramping back down and returning to normal in the afternoon of Nov. 15. The entire experiment lasted five and a half days. November releases prior to and after the HFE release were the customary 6,500 cfs to 9,000 cfs, says the BLM’s Katrina Grantz.
For water watchers, the elevation of Lake Powell decreased 2.9 feet during the experiment.
In December, the release volume is expected to fluctuate between 9,500 cfs in the nighttime to 17,500 cfs in the daytime.
The forecast for water year 2015 unregulated inflow to Lake Powell, issued by the Colorado Basin River Forecast Center, projects that unregulated inflow volume will be 88 percent of average based on the period 1981-2010. The forecast ranges from a minimum of 68% of average to a maximum probable of 172% of average, should El Nino fill the Colorado Basin’s rivers at full force.