Land & Environment

USU Ecologist says 'Hydropeaking' Harming Colorado River Ecosystems

In Grand Canyon, a volunteer scoops a native fish called the 'Humpback Chub' from the Colorado River for study. Efforts by ‘citizen scientists’ were crucial to the study of the river’s food webs, says USU ecologist Scott Miller. Courtesy USGS.

So you drag yourself out of bed each morning and, along with millions of your fellow neighbors of the American West, you jump in a hot shower, rev up your coffeemaker and toss some bread in the toaster. All of that energy usage takes on toll on utility companies and they respond by amping up supplies to meet demand.

Good news for you, but maybe not for the environment. In particular, widespread use of “hydropeaking,” a practice used to increase river flows from hydroelectric dams during peak demand, is harming the Colorado River’s fragile food webs, says Utah State University ecologist Scott Miller.

“Aquatic organisms such as insects have adapted to natural disturbances, including spring flooding from snow melt,” says Miller, assistant professor in USU’s Department of Watershed Sciences and the USU Ecology Center. “But these are disturbances that occur over weeks or months. The river’s tiny critters aren’t prepared for novel disturbances by humans, such as hydropeaking, that occur in the span of hours.”

The result is a decline in the health of the river’s aquatic ecosystems, which Miller and colleagues from the U.S. Geological Survey, Idaho State University and Oregon State University, describe in the May 2, 2016, early online edition of BioScience.

Aquatic insects play an essential role in river food webs and are the main food source for the region’s fish, birds, bats and other wildlife.

“This study is unique because it focuses on how abrupt water level changes affect aquatic insects at every stage of life,” says Miller, director of the USU-based Bureau of Land Management National Aquatic Monitoring Center, known as “The Bug Lab.”

Having this information, he says, offers a path forward in making adjustments to mitigate the effects of hydropeaking.

Miller’s colleague Ted Kennedy, USGS scientist and lead author of the study, says the research determines, for the first time, the ecological impacts of hydropeaking separated from other dam-imposed stressors.

“It identifies specific cause-and-effect relationships responsible for biodiversity loss below hydroelectric dams,” Kennedy says. “These results may help resource managers improve river health, while still meeting societal needs for renewable hydroelectricity.”

One idea for reducing the effects of hydropeaking is “to give insects the weekend off,” Miller says.

“Managers still have to meet human customer demands, but a course of action might be to avoid hydropeaking on weekends or at least avoid it during dawn or dusk, when insects often lay their eggs,” he says.

Miller’s USU colleague Jack Schmidt, a professor in the Department of Watershed Sciences, encouraged research focused on river ecosystems during his tenure as chief of the USGS Grand Canyon Monitoring and Research Center from 2011 to 2014.

“Hydropower production is a pervasive component of American’s energy portfolio and transformation of free-flowing rivers into reservoirs is an unavoidable impact of dams,” Schmidt says. “But, with this study, Miller, Kennedy and their colleagues demonstrate that mitigation of the adverse impacts of hydropower generation is possible. Society will have to evaluate how to balance the costs of this mitigation with the benefits of healthier downstream aquatic ecosystems.”

Related links:

Contact: Scott Miller, 435-797-2612,

Writer: Mary-Ann Muffoletto, 435-797-3517,

Katie Winkelman, a study volunteer with Grand Canyon Youth, takes photos on the Colorado River. USU ecologist Scott Miller says the study provides insights to mitigate the harmful effects of hydropower on river food webs. Courtesy USGS.


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