Adapting water resource systems to a changing future: challenges for UK hydrology in the 21st century.

The aquatic environment globally is under enormous pressure. People responsible for managing and regulating water resources face very difficult decisions about how to allocate water, restore the natural environment and use their scarce financial resources. Their decisions will depend upon challenging scientific questions about how catchments and river basins are going to change in the future and how they will respond to combinations of interventions at a range of different spatial scales. We contend that hydrological science in the UK is not yet, or in some instances even near to, providing the evidence that is needed to manage the quantity and quality of water resources in the 21 century, given the scale and complexity of interventions that are now being considered and the uncertainty in catchment response. In some respects, hydrology has been exemplary in the decision-orientation of much of the research in the field. Enhancements in observation (especially Earth Observation), combined with modern data-driven methods are having a transformative impact on hydrology. But we will argue to tackle the water challenges for the UK in the 21st century requires further fundamental improvements in the capacity to model catchment processes and the impacts of a wide range of management interventions.This article is part of the discussion meeting issue 'Hydrology in the 21st century: challenges in science, to policy and practice'.