Simulation of river flow in Britain under climate change: baseline performance and future seasonal changes

Climate change is likely to manifest in river flow changes across the globe, which could have wide‐ranging consequences for society and the natural environment. A number of previous studies used the UK Climate Projections 2009 (UKCP09) to investigate the potential impacts on river flows in Britain, but these projections were recently updated by the release of UKCP18, thus there is a need to update flow studies. Here, the UKCP18 Regional (12km) projections are applied using a national‐scale grid‐based hydrological model, to investigate potential future changes in seasonal mean river flows across Great Britain. Analysis of hydrological model performance using baseline climate model data (1980–2010) shows relatively good agreement with use of observation‐based data, particularly after application of a monthly precipitation bias‐correction. Analysis of seasonal mean flow changes for two future time‐slices (2020–2050 and 2050–2080) suggests large decreases in summer flows across the country (median ‐45% by 2050–2080), but possible increases in winter flows (median 9% by 2050–2080), especially in the north and west. Information on the potential range of flow changes using the latest projections is necessary to develop appropriate adaptation strategies, and comparisons with previous projections can help update existing plans, although such comparisons are often not straightforward.