Bug Flow experiment to be conducted this summer under the Glen Canyon experimental and management plan – St George News

The mayfly is a common aquatic insect and one of several species upon which trout feed in the Colorado River | SBTheGreenMan, iStock / Getty Images Plus, St. George News

SALT LAKE CITY—With the goal of improving aquatic insects’ egg-laying conditions, the Bureau of Reclamation started Sunday its Macroinvertebrate Production Flow, or Bug Flow, at Glen Canyon Dam.

Brown caddisfly isolated on white background | HHelene, iStock / Getty Images Plus, St. George News

As part of the Long-Term Experimental and Management Plan, this experiment through Aug. 31 and will provide data about these insects, which are the primary food source for fish in the Colorado River, according to a Bureau of Reclamation news release.

A collaborative team, including the Department of the Interior’s Bureau of Reclamation, US Geological Survey, National Park Service, US Fish and Wildlife Service and Bureau of Indian Affairs, rendered the decision to study these flow experiments, which are designed to “optimize benefits to the Lees Ferry Reach and Grand Canyon’s Colorado River ecosystem while meeting water delivery requirements and minimizing negative impacts to hydropower production,” the news release said.

“We are pleased to continue our research on the effects of modifying release flow patterns to benefit the Colorado River ecosystem,” said Michael Moran, Acting Chief of the US Geological Survey Grand Canyon Monitoring and Research Center, which monitors the Colorado River ecosystem response to all Glen Canyon Dam flow experiments. “Past research has shown that many different resources have benefitted from previous experimental flows, and we are looking forward to collecting this additional data on the river.”

Bug Flows are a water flow experiment that consists of steady, low weekend releases from Glen Canyon Dam and normal fluctuating releases for hydropower during weekdays, according to the news release. Bug Flows do not affect total annual, monthly or weekly release volumes from Lake Powell through Glen Canyon Dam but slightly modify release schedules and flow rates.

Recreational river users will likely notice steady flows resulting from the steady weekend releases as they move downstream through the Lees Ferry Reach and the Grand Canyon. Dam releases and minimum flows are within the range typically experienced by recreation users (eg, anglers, boaters, kayakers and campers), according to the news release.

“In this time of drought, continuing experiments like Bug Flows in with the Grand Canyon Protection Act is critical,” said Reclamation’s Upper Colorado Basin Regional Director Wayne Pullan. “At the same time, drought makes assessing and mitigating for the effects of experiments at other resources like those hydropower, water supply and recreation more important.”

The purpose of these experimental flows is to determine whether this type of operation can improve the abundance, diversity and stability of aquatic insect populations, thereby increasing aquatic insect prey available for a variety of wildlife. Insects expected to benefit from this experiment are an important food source for many species of fish, birds and bats in the canyonthe release said.

Bug Flow findings from 2018-2020 suggest that the previous Bug Flow experiments may have improved conditions for adult insects, increased the abundance of caddisflies river-wide and increased algae production. In addition, angles captured more rainbow trout on average during Bug Flows than they did during typical fluctuating flow patterns.

Contrary to predictions, no increase in the abundance of midge’s flies were observed during the first three years of the experiment. Scientists believe that further experimentation, research and monitoring may help to determine whether the Bug Flows experiment benefits native fishes in the Lees Ferry Reach below the Glen Canyon Dam and in the Grand Canyon, the news release stated. This experiment provides scientific information important to future decision-making.

The Glen Canyon Dam Implementation Team will closely monitor the condition of resources during the experiment and may terminate implementation at any time if unanticipated negative impacts are observed or are likely to occur due to ongoing drought and low lake levels.

For more information about flow volumes, click on the following links: Lees Ferry and Lake Powell.

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