Developing Freshwater Quality Futures for the UK

Multiple pressures, both past and present, influence the chemical and biological quality of UK freshwaters. While some of these pressures (e.g. metals, acidification, oxygen-consuming substances) appear to have eased in recent decades, others (e.g. industrial and personal organic micropollutants, nitrogen and phosphorus) remain and may be increasing. Reductions in levels of freshwater pollution following the introduction of regulations (e.g. European Urban Waste Water Treatment Directive) have driven a degree of biological recovery across the UK. Whether these improvements in UK freshwater quality and biodiversity will be maintained long term is of great interest to the public who rely on freshwaters for recreation, to water companies for drinking water supply, to industry and to statutory regulators.Our Long Term Large Scale Freshwater Ecosystems (LTLS-FE) project aims to understand the effects of multiple pressures and drivers on freshwater quality at a national scale using a multidisciplinary modelling approach. We are working to develop and analyse future scenarios of water quality and biodiversity in UK freshwaters which take account of both climate and socioeconomic change (RCP/SSP combinations).Here, we present the multidisciplinary modelling approach used in LTLS-FE, which links models of soil processes, agriculture and point source releases of pollutants to surface waters with a hydrological model of transport and transformation in the freshwater environment. These will then be used to drive a national-scale ecological model to predict impacts on freshwater biota. We will present the innovations that have been required to achieve this goal, including a national-scale model of sewage treatment, national datasets of metal fluxes from mine waters and anthropogenic abstractions, and scenarios of pollutant releases from domestic and industrial sources to 2080. We are now in the final year of our four-year project and will demonstrate how well the LTLS-FE freshwater model performs on historical periods before sharing early results of future scenarios.