Challenges for water-quality research in the new IAHS decade on: Hydrology Under Societal and Environmental Change

Emerging water quality research challenges of the next decade are related to understanding how the function of complex catchment sub-systems interact and co-evolve in response to an unprecedented level of environmental change. Several high-level challenges are identified in this paper that relate to those of the new IAHS thematic decade ("Panta Rhei": 2013-2022), but explored within the specific context of water quality science. We review current research trends and outline the need for new approaches able to deal with complexity, non-stationarity and uncertainty in future scenarios. We then identify opportunities that exist for the community-driven integration of the diversity of models of hydrology, biogeochemistry and society, with environmental sensing approaches and cyber-infrastructure as a way to integrate process-driven and data-driven approaches for exploring river basin health and water quality dynamics. By embedding our collective efforts in development of a global network of catchment observatories, we believe we can support further knowledge discovery through facilitating comparative analyses and synthesis activities.