Current global issues of water security related to both water quantity and quality are discussed, and the implications of increasing population and development in a changing world. There are important scientific challenges. For example, while hydrologists and water managers have well-developed design and simulation tools based on the assumption of stationarity, new approaches are needed to understand natural climate variability and to address non-stationary and uncertain climate futures. And major challenges also arise in predicting effects of land use and land management change under both current and future climates, for what are complex systems, determined not only by physical, but also by social, economic and policy dimensions.

There has been a long and fruitful history of collaboration between statisticians and hydrologists in statistical and stochastic hydrology. Stochastic models of precipitation developed by the statistical science community have played an important role in advancing hydrological design and simulation capability; more recently they have been adapted for climate change scenarios; current strengths and weaknesses are reviewed. Methods of uncertainty analysis have become ubiquitous in hydrological modelling of gauged and un-gauged areas, and turning to land management change, there is growing interaction between systems analysis, complex models and emulation modelling in the multi-scale analysis and simulation of environmental change.

Looking to the future, such collaboration is essential, but insufficient, to address these challenges. Environmental change is driven not just by climate, but also by people and policy; a new paradigm of interaction with social science is needed, socio-hydrology, if we are to manage uncertainty in what are complex human environmental systems and meet the challenges of water security in a changing world.

Keywords: Water security; Statistical science; Climate change; Land use change

Biography: Dr Howard Wheater is Canada Excellence Research Chair at the University of Saskatchewan and Distinguished Research Fellow at Imperial College London. He is a Fellow of the Royal Academy of Engineering, London and the American Geophysical Union. He is Chair of UNESCO's GWADI arid zone water resources programme and vice-Chair of the World Climate Research Programme's GEWEX initiative. He has advised governments and states on water issues world-wide and was awarded the Prince Sultan bin Abdulaziz international prize for water.