Water Quality Responses to Floods and Droughts in the Context of Climate and Land Use Change. 

Anthropogenic pressures, including climate and land-use change, are expected to intensify hydrological extremes, such as floods and droughts, in many regions worldwide. These hydrological changes are likely to have cascading effects on water quality, affecting a range of stakeholders and the ecological health of the freshwater system. However, significant uncertainty exists in projections of future catchment-scale hydrological extremes and the resulting effect on different water quality parameters.In this study, we assess potential future changes in hydrological extremes and associated water quality responses across five hydrologically diverse catchments in Yorkshire, UK. Climate forcing is derived from 12 UK Climate Projections (UKCP) regional climate models at the highest available spatial resolution of 2.2 km. To account for socio-environmental change, three contrasting land use scenarios are considered, ranging from a sustainable transition (SSP1-2.6) to fossil-fuelled industrialisation (SSP5-8.5). The integrated hydrological and water quality model ‘HYdrological Predictions for the Environment’ (HYPE) is applied within a Generalised Likelihood Uncertainty Estimation (GLUE) framework to predict hydrological droughts and floods and the water quality response for an ensemble of climate and land use projections. In this talk, we first present how both hydrological droughts and floods are projected to change under future climate and land-use scenarios. We then show how water quality parameters (water temperature, suspended sediments, nitrogen, phosphorus) change during these extreme events. Lastly, we quantify how spatio-temporal uncertainty in climate, land use and HYPE parameterisation propagate through to the simulated flow and water quality parameters.