Quantifying the Impact of Water Abstraction for Low Head ‘Run of the River’ Hydropower on Localized River Channel Hydraulics and Benthic Macroinvertebrates

‘Run of the river’ (ROR) hydropower schemes have undergone a recent resurgence in Europe, and with legislation requiring the protection and enhancement of the physical and ecological condition of European rivers, there is a need to understand the impacts of these schemes. This paper presents an assessment of the eco-hydraulic impact of a ROR hydropower scheme in the Peak District National Park, UK. Due to the ponded nature of the depleted stretch at the study site, this paper focuses on the characterization of the hydraulic impact of water abstraction for a ROR scheme at the hydropower outlet and samples microhabitats of benthic macroinvertebrates within the hydraulically affected zones. Measurement of hydraulic transects shows that the scheme's operation notably alters river channel hydraulics at 60% of water depth, whilst impacts are much less distinct in close proximity to the river bed. We identify eco-hydraulic relationships between benthic macroinvertebrate communities and localized near-bed velocity and turbulence conditions, thus indicating the potential for water abstraction by ROR schemes to impact lower trophic levels of riverine ecosystems. However, spatial patch-scale (10–100 m2) meso-habitat comparisons of invertebrate communities around the hydropower outlet showed only subtle differences, suggesting that in this case benthic communities are only minimally impacted by the ROR scheme.