A decade ago, ancient technology - using natural water to perform work - was the green goal. Today, dams are bad but now wind is back in fashion.
What changed? Dams got used, and 'our energy production is fine' is a terrible fundraising call to action so current methods have to be criticized. Now, dams that were once prized by activists, they generate more energy than all other renewable sources combined, are being criticized for the devastation of aquatic insect populations and the food webs that those insects underpin. Take that, native American scientists of yore. The virtual absence of mayflies, stoneflies and caddisflies from the Colorado River in Grand Canyon has also been a mystery to modern scientists.
Dr. Ted Kennedy, an ecologist with the US Geological Survey's Grand Canyon Monitoring and Research Center, and colleagues blame "hydropeaking", which is basically controlling how much water flows from the dam. A paper says this generates artificial tides that extirpate insect species. Aquatic insects play an essential role in river food webs and are the main food source for countless species of fish, birds, bats and other wildlife.
The research was based in part on a large citizen science project with more than 2,500 insect samples taken on the Colorado River in the Grand Canyon, downstream of Glen Canyon Dam. This dataset was collected almost entirely by river guides, educational groups, and other citizen scientists. Researchers also tested the effects of abrupt water levels changes on river health by comparing insect diversity across 16 large dammed rivers in the western United States that vary in the degree of hydropeaking.
In BioScience Talks, they offer possible solutions to the hydropeaking conundrum, such as mitigation measures like leaving river levels low and stable at times when impacts on power production at Glen Canyon Dam would be minimal, for example on weekends. This could allow insects a few days to lay their eggs with success.