The number of small-scale hydropower schemes in the UK and Ireland has been growing in recent years due to the introduction of incentives for renewable energy generation, the burgeoning knowledge base for implementing such schemes, and innovations in small hydropower turbines. In the UK, the amount of electricity generated from small-scale hydropower has nearly tripled since 2010. One of the key areas of growth within the sector has been run-of-river hydropower schemes, with several hundred now operating across the UK and the Republic of Ireland; the majority situated in the mountainous areas of Scotland and Wales. Although the overall grid contribution of these schemes is small (~2%), they still play an important role, not only in decarbonising the grid and contributing to national emission reduction goals, but also at local scales, where schemes often provide financial benefit to local communities and individuals.

In this study, we quantify the impact of a worst-case future climate change scenario (Representative Concentration Pathway 8.5) on the generation potential of small-scale run-of-river hydropower schemes in the UK and Republic of Ireland. EXP-HYDRO hydrological model is used to simulate future daily streamflow for the 2020-2079 period for over 400 hydropower sites in more than 160 individual catchments across the two countries. We estimate daily abstraction potential at each site based on the local environmental regulator’s (for Scotland, England, Wales, Northern Ireland, and Ireland) general abstraction conditions. We then perform seasonal and annual Mann-Kendall trend analysis at each site to analyse the changes in: 1) the number of days when power generation is possible, 2) the number of days when maximum abstraction is reached, 3) the total abstractable volume, and 4) mean abstraction volume on days when power generation is possible. The scale of study undertaken allows for characterisation of both the impact of regional variation in future climate change forcing, as well as analysis of the impact of local environmental regulation, on the future generation potential of run-of-river hydropower in the UK and Ireland.