Researchers at the University of Brighton’s School of Environment and Technology found that in five out of six widely used fish metrics, there were no statistically significant impacts from small-scale run-of-river hydroelectric power schemes.
The goal of this project was to understand the environmental effects of hydropower schemes in rivers, and the study looked at change in fish communities compared with a set of control sites without hydropower across a range of river types and locations.
The researchers do say that the small number of samples (23 run-of-river sites) means subtle changes may not have been detected.
The study used data collected by the Environment Agency as part of routine long-term monitoring programs. The sites examined had run-of-river hydro schemes that had been operating for an average of four years. Researchers identified 23 paired control sites to see what variation in fish populations might have occurred for other reasons.
The six measures of fish community composition studied were:
- Number of fish species (recorded as density for a given area)
- Number of fish
- Number of Atlantic salmon
- Number of Atlantic salmon greater than 1 year old
- Number of brown trout
- Number of brown trout greater than 1 year old
The only statistically significant change found was a very small decrease in the mean number of fish species (-0.06 species per 100 m2 of surface water area) in the period after hydropower construction relative to the period before construction. At the same time, there was a small increase in the mean number of species (+0.13 species per 100 m2) at the control sites.
This research project was jointly funded by the Environment Agency’s Evidence Directorate and the Natural Environment Research Centre through a Policy Placement Fellowship.
More information is available here.