The building houses equipment for two Archimedes screw water turbines to generate up to 220kW of electricity from the natural flow over the weir. This type of turbine works well for high flow, low head as is the case here. Behind the white concrete wall is the fish pass to allow salmon and trout to bypass the turbines, which are only allowed to operate if the flow is sufficiently high.
Uploaded to Geograph by Jim Barton on 11 December 2016
Photo © Jim Barton, 11 December 2016. Licensed for reuse under this Creative Commons licence