The Global Water Futures Core Modelling Strategy

Climate warming and human actions are altering precipitation, reducing snowpacks, accelerating glacier melt, intensifying floods, and increasing drought risk, while pollution from population growth and industrialization is degrading water systems. With such change, it is clear that the historical patterns of water availability are no longer a reliable. This is particularly evident in the cold regions that cover much of Canada and provide a large proportion of the world's freshwater supply. An integral part of the Global Water Futures Programme dictates that new, connected climate, hydrological, water quality and water management modeling tools that precisely capture these interconnected forces and their societal implications are necessary. Given this need, a core modelling team was formed to deliver the new modeling tools tied with the new monitoring systems for Canada and the cold regions of the world that were identified as programme deliverables. The systems being developed by the core modeling team are designed to support improved disaster warning and long term prediction of water futures. The modelling strategy is based on a sequence of atmospheric driving models, linked to terrestrial, riverine and management models, with a hierarchy of time horizons and objectives that scale from short term/real time operations to medium term predictions at weekly to seasonal scales to long term predictions at seasonal to decadal time scales. The strategy and models being evaluated and tested as part of the larger Global Water Futures programme are outlined. This includes scaling strategies, new basin segmentation approaches, data assimilation approaches, the role of hydrological observatories in model development and the multi-objective calibration strategies being examined. A multi-model approach is being used to quantify predictive uncertainty and show rapid advances over the 5 million km2 modelling domain. Examples of new models include hydrochemistry models suitable for Canadian agriculture and great lakes, glacier, river ice and permafrost hydrology models, multi-physics multi-scale modular models and coupled atmospheric land surface hydrology schemes. The modelling systems being developed may have application outside of Canada and have particular merit in cold and data-sparse regions of the world.