Aquatic insects want the weekend off: Changing dam release strategies to restore river health
Hydropower is often seen as a green energy solution, but dams cause substantial environmental damage that is not part of the ‘green’ labelling. The conundrum of meeting both human and river health needs in a cost effective manner was highlighted in the Perspective piece written by the IAE’s Professor LeRoy Poff, and his colleague, Professor John Schmidt of Utah State University, in the prestigious journal, Science.
“Releasing water below the dam has a clear economic cost associated with it, so there is a conflict between environmental needs and financial gain,” says Professor Poff. “We need to build support for environmental flows and targeted releases with specific and attainable ecological outcomes.” Poff argues this can be achieved, with small operational tweaks proven to be ecologically beneficial with minimal costs in forgone hydroelectric production.
Dams substantially change rivers by generating lakes, altering flow, and creating barriers which impede the movement of aquatic organisms and sediment flow. Many hydropower dams release more water during the day, when electricity demands are greatest in a practice called hydropeaking. Downstream shoreline habitats can be severely impaired by this repeated wetting and drying, and aquatic insects that mate and lay eggs in shallow water are particularly vulnerable. These insects are key to river food webs as prey for fish and terrestrial predators such as birds, bats and spiders.
Poff and Schmidt summarise recent studies that demonstrate how small changes to dam operation can have large effects downstream. One such study on the Colorado River downstream from the dam at Glen Canyon showed that eliminating hydropeaking on weekends, when demand is lowest, would make reliable egg-laying habitat for aquatic insects. Restricting hydropeaking during prime reproductive season might also allow these highly fecund insects to recover in abundance within a few years. This would in turn help to restore the integrity of the food web and support fish production.
“There are about 58,000 dams around the world, so we need to incorporate ecological thinking to our existing water management strategies,” says Professor Poff. “With thousands more proposed it is important we design new dams to minimise the distortion of natural flows. Doing this at the design phase is the most effective way to reduce ecosystem function loss. This act of balancing economic gain against environmental degradation is a challenge given the competing needs for water. Identifying specific ecological targets that can be met with small amounts of water will build more support for environmental flows.”
You can read the full Perspective piece here.