Impacts of climate change on future water availability for hydropower and public water supply in Wales, UK

Study region: Wales, United Kingdom.
Study focus: Climate change is predicted to have a large impact on the hydrological regimes of Welsh rivers. However, its influence on the abstraction capability of key sectors, such as public water supply (PWS) and hydroelectric power (HEP), is not yet fully understood. We use the Soil and Water Assessment Tool (SWAT) to generate future (2021–2079) streamflows under a worst-case scenario of greenhouse gas emissions (Representative Concentration Pathway 8.5) at two catchments in Wales, the Conwy and Tywi. SWAT streamflow output is used to estimate total unmet demand for PWS and changes in generation characteristics for HEP. PWS unmet demand is assessed using the Water Evaluation And Planning (WEAP) system under increasing, static, and declining demand scenarios. Mann-Kendall analysis is performed to detect and characterise trends.
New hydrological insights for the region: Under all future demand scenarios, there is increased occurrence of insufficient streamflow to satisfy PWS demand. For HEP, decrease in annual abstraction volume results in a loss of generation potential, despite an increasing number of days that maximum abstraction is reached. Changes in HEP generation and PWS availability are most pronounced in the medium-term (2021–2054), with rate of change slowing after 2060. We provide a novel perspective on future water resource availability in Wales, giving context to management planning to ensure future PWS sustainability and HEP generation efficiency.