A hydrologic routing model suitable for climate‐scale simulations of arctic rivers: application to the Mackenzie River Basin

In this study, the Hillslope River Routing (HRR) model was modified for arctic river basin applications and used to route surface and subsurface run‐off from the Community Land Model (CLM) in the Mackenzie River Basin (MRB) for the period 2000–2004. The HRR modelling framework performs lateral surface and subsurface run‐off routing from hillslopes and channel/floodplain routing. The HRR model was modified here to include a variable subsurface active layer thickness (ALT; permafrost) to enable subsurface water to resurface, a distributed surface storage component to store and attenuate the rapid generation of snowmelt water, compound hillslopes to account for the low relief near rivers and floodplains, and reservoir routing to complete the total surface and subsurface water storage accounting. To illustrate the new HRR model components, a case study is presented for the MRB. The basin is discretized into 5077 sub‐basins based on a drainage network derived from the global digital elevation model (DEM) developed from the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) sensor on board NASA's Terra satellite and river widths extracted from LandSat images. The median hillslope land area is 68.5 km² with a flow length of 2.8 km. Gridded CLM surface and subsurface run‐offs are remapped to the HRR model's irregular sub‐basins. The role of each new model component is quantified in terms of peak annual streamflow (magnitude and timing) at select locations and basin‐wide total water storage anomalies. The role of distributed surface storage is shown to attenuate the relatively rapid generation of snowmelt water, impact the annual peak hydrograph (reduced peaks by >30% and detailed peak by >20 days), and account for 20% of the monthly total water storage anomalies averaged over the year and ranging from 14 to 25% (?10 to 30 mm) throughout the year. Although additional research is needed to dynamically link spatially distributed ALT to HRR, the role of ALT is shown to be important. A basin‐wide, uniform 1 m ALT impacts the annual peak hydrograph (reduced peaks by 9% and detailed peak by 8 days) and trends in total water storage anomalies. Copyright © 2014 John Wiley & Sons, Ltd.