The BaySys project: Hydrology, climate change, anthropogenic water use, and model uncertainty at the continental scale

Abstract:

The Hudson Bay Drainage Basin (HBDB) spans 4 million km², draining to the Hudson Bay Complex (HBC). The HBC is the world’s largest continental shelf sea, connecting to the north Atlantic and Arctic oceans. To understand changes to the HBC’s oceanography, sea ice circulation, and biogeochemistry we must first understand the individual and joint effects of high-latitude climate change and increasing hydroelectric regulation on terrestrial freshwater. The HBC receives roughly half of its terrestrial freshwater from two regulated complexes, the Nelson Churchill River Basin and La Grande Rivière Complex. This presentation summarizes six years of studies, touching on multiple elements of the hydrologic cycle in modelling, modelling methods, and this work’s contributions to a larger interdisciplinary study of the HBC. The work presented here ranges from studies of historic records to determine detectable impacts of regulation on streamflow, addition of generalized reservoir regulation to a continental-scale hydrologic model, development of a naturalized hydrologic model to directly compare regulation and climate change, projection of future hydrology using a robust atmospheric forcing ensemble as input, quantifying sensitivity of models in sparsely-gauged regions to model structure, calibration methodology, parameter estimation, and atmospheric input, and use of predictions in ungauged basins methods to determine model uncertainty for the 400 rivers delivering freshwater to the HBC. This work charts the development of 90 years of freshwater data from input selection, to input bias-correction, to model development and calibration, to process improvement, to sensitivity analyses, and finally to uncertainty estimation. Doing so in this biologically productive region which is also undergoing rapid change (anthropogenic and climatic) sheds light on key processes in the continental-scale hydrologic modelling chain, the importance of presenting time-variant uncertainty in hydrologic change, and the interdisciplinary impacts to changing terrestrial freshwater.