A new flow for Canadian young hydrologists: Key scientific challenges addressed by research cultural shiftsCaroline Aubry-Wake1, Lauren D. Somers2,3, Hayley Alcock4, Aspen M. Anderson5, Amin Azarkhish6, Samuel Bansah7, Nicole M. Bell8, Kelly Biagi9, Mariana Castaneda-Gonzalez10, Olivier Champagne9, Anna Chesnokova10, Devin Coone6, Tasha-Leigh J. Gauthier11, Uttam Ghimire6, Nathan Glas6, Dylan M. Hrach11, Oi Yin Lai14, Pierrick Lamontagne-Halle3, Nicolas R. Leroux1, Laura Lyon3, Sohom Mandal12, Bouchra R. Nasri13, Natasa Popovic11, Tracy. E. Rankin14, Kabir Rasouli15, Alexis Robinson16, Palash Sanyal17, Nadine J. Shatilla9, 18, Brandon Van Huizen11, Sophie Wilkinson9, Jessica Williamson11, Majid Zaremehrjardy191 Centre for Hydrology, University of Saskatchewan, Saskatoon, SK, Canada2 Civil and Environmental Engineering, Massachusetts Institute of Technology, MA, USA3 Department of Earth and Planetary Sciences, McGill University, Montreal QC4 Department of Natural Resource Science, McGill University, Montreal, QC, Canada5 Department of Earth Sciences, Simon Fraser University, Burnaby, BC, Canada6 School of Engineering, University of Guelph, Ontario, ON, Canada7 Department of Geological Sciences, University of Manitoba, Winnipeg, Canada8 Centre for Water Resources Studies, Department of Civil & Resource Engineering, Dalhousie University, Halifax, NS, Canada9 School of Geography and Earth Sciences, McMaster University, Hamilton, ON, Canada.10 Department of Construction Engineering, Ecole de technologie superieure, Montreal, QC, Canada11 Department of Geography & Environmental Management, University of Waterloo, Waterloo, ON, Canada12 Department of Geography and Environmental Studies, Ryerson University, Toronto, ON, Canada13 Department of Mathematics and Statistics, McGill University, Montreal, Qc, Canada14 Geography Department, McGill University, Montreal, QC, Canada15 Meteorological Service of Canada, Environment and Climate Change Canada, Dorval, QC, Canada16 Department of Geography and Planning, University of Toronto, Toronto, ON17 Global Institute for Water Security, University of Saskatchewan.18 Lorax Environmental Services Ltd, Vancouver, BC, Canada.19 Department of Earth and Atmospheric Sciences, University of Alberta, Edmonton, AB, Canada

Abstract Ice phenology, defined as the timing of freeze-up and ice-cover breakup, plays a key role in streamflow regimes in cold-region river catchments. River freeze-up and ice-cover breakup events are controlled by meteorological and hydrological variables. In this study, we present a modelling framework consisting of a physically-based semi-distributed hydrological model and the integration of a 1D stream temperature model that can predict the ice duration in cold region rivers. The hydrological model provides streamflow and hydraulic parameters for the stream temperature model to obtain instream water temperature. The model was successfully applied in the Athabasca River basin in western Canada. Calibration was carried out using the water temperature recorded in the stations at the towns of Hinton, Athabasca and Fort McMurray. Model results show consistent correspondence between simulated freeze-up and breakup dates and the hydrometric station data. In the main tributaries of the basin, freeze-up timing spans from the last week of September to the second week of November and ice-cover breakup occurs from the second week of March to the last week of May. The model presents an application of water temperature and ice phenology simulation which can be incorporated in ice-jam flood forecasting and future climate change studies.

• A physically-based semi-distributed hydrological model and a 1D stream water temperature model forced by climate change scenarios is presented here to analyze the effects of stream flow and water temperature changes on fish habitat in the Athabasca River catchment. • Streamflow decreases in most of the catchment will reduce flow velocities and water depths causing current Athabasca Rainbow Trout habitat to be suboptimal. • Increases in water temperature will result in habitat contraction concentrating Athabasca Rainbow Trout in the upper headwaters of the catchment. • Athabasca Rainbow Trout habitat can potentially be reduced as the frequency of occurrence of life threatening and lethal water temperatures tend to increase, particularly in summer. Changes to natural flow and air temperature in the context of climate change can have impacts on physiology, distribution and survival of fish. Of particular interest is the Athabasca River basin, a highly biologically productive basin that includes one of the largest boreal freshwater inland river deltas in the world and serves as habitat for many fish species. Earlier melt events, higher winter and spring flows and lower summer flows are expected as a consequence of climate change in this basin. Here, we model changes in river flow and water temperature under changing climate scenarios through the integration of a physically-based semi-distributed hydrological model and a 1D stream water temperature model forced by climate change scenarios. The modeled changes in streamflow and water temperature are used to predict changes in habitat suitability for the Athabasca Rainbow Trout (ART) ( Oncorhynchus mykiss ), a unique ecotype of trout considered as a ‘species at risk’. The results indicate that future flow decreases in most of the basin can lead to reduced flow velocities and water depths making current ART habitat suboptimal. Also, warming low-land habitats and increasing water temperatures will increase metabolic rates and stress fish forcing them to migrate upstream to cooler waters confining their habitat range.