Future Water Resources for Hydropower

Climate change likely to have a substantial impact on the timing, quantity and quality of future streamflows, with knock-on implications for water abstractors. One such water abstracting sector is hydropower, in particular run-of-river schemes, which do not impound water and require a given minimum flow to be present in order for water to be abstracted for use. Hydropower plays a small but important role in renewable energy generation in the UK and Ireland, helping in work towards achieving governmental emissions reduction targets, and the overall stability of the energy grid. Therefore, understanding how future generation capacity and characterises may be affected is important for energy provision planning.

Our work quantifies the impact of future streamflow changes (2021-2080) on run-of-river hydropower schemes across the UK and Ireland, modelling future daily streamflow in catchments containing run-of-river hydropower abstractions. This work, encompassing 531 schemes in 178 catchments, is based on a worst-case scenario of future climate change, using representative concentration pathway 8.5 from the Intergovernmental Panel on Climate Change (IPCC). Modelling work has been conducted using the EXP-HYDRO hydrological model, with the latest climate change projections for the British Isles, the UK Climate Projections 2018 dataset (UKCP18). The daily amount of water available for abstraction at each scheme during the future modelled period has been calculated using standard abstraction licence conditions for each nation in the study region (England, Wales, Scotland, Northern Ireland, and Ireland). An estimation of the impact in terms of power generation has then also been made.

Our results suggest regional variation in changes in future total annual abstraction potential, with this likely being partly driven by nation-specific abstraction licence conditions and climate forcing. Variations in abstraction licence conditions mean that even if catchments in different nations display similar streamflow responses, the availability of water for abstraction, and therefore generation potential, may still differ. In general, there is also a reduction across the two islands in the number of days per year that abstraction for hydropower will be possible, with the only exceptions being schemes in northwest Scotland and the Lake District.

In terms of power generation implications, these have been calculated for Great Britain and the island of Ireland individually, owing to the energy network systems in place. Our results project an annual increase of 6.2% in power generation from run-of-river hydropower generation for Great Britain, when comparing the 2021-29 average to the 2072-80 average. This trend is driven by large increases in Scotland in winter and spring, which outweighs reductions seen in the summer and autumn in England in particular. For the island of Ireland, a 1.4% decrease is seen in annual power generation when comparing the same time periods, driven by large summer decreases and smaller winter increases.

The work presented here forms part of a paper published in Renewable Energy, which is available for free and open access at the following link: https://doi.org/10.1016/j.renene.2023.03.021.