Projected changes in water availability in the United Kingdom

There is evidence for a change in the seasonality of UK rainfall consistent with projections from climate models, which could have a significant impact on water availability. This paper describes an analysis of seasonal mean runoff in the UK calculated directly within an ensemble of regional climate models. Both surface and subsurface runoff have been analyzed, and the times at which a climate change signal in the runoff could be detected have also been calculated. Runoff is projected to increase in winter in all regions of the UK, by 5-25% by the 2080s, but remain the same or decrease in the other seasons. We find that a climate change signal could be detected in runoff in winter in western parts of the UK as early as the 2020s, but much later in eastern areas of England. In summer, detection times (2040-2060 s) are generally later than those in winter (2020-2040 s). Our results imply water resources in the southeast of the UK could be reduced during the twenty-first century, and adaptation may be needed long before a formal detection of a climate change signal is made.