Simulating fully-integrated hydrological dynamics in complex Alpine headwaters

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Authors

James Matthew Thornton , René Therrien , Grégoire Mariéthoz , Niklas Linde , Philip Brunner 

Abstract

Hydrological climate change impact assessments in mountainous areas still frequently rely upon highly simplified approaches. Fully-integrated surface-subsurface codes would appear to hold far greater potential to represent the distinctive regimes of steep, geologically complex headwaters. However, their application in mountainous terrain has thus far been predominantly limited to crystalline catchments in western North America, leaving their utility in Alpine contexts untested. Here, a model of two adjacent calcareous Alpine headwaters is presented that accounts for 2D surface flow, 3D variably-saturated groundwater flow, and evapotranspiration. An energy balance-based representation of snow dynamics contributes high-resolution forcing data, whilst a sophisticated 3D geological model helped inform the subsurface structure. In the first known attempt to calibrate an integrated, catchment-scale model in mountainous terrain automatically, numerous uncertain parameters were estimated. The salient features of the hydrological regime were ultimately satisfactorily reproduced; over an independent 11-month evaluation period, a Nash-Sutcliffe efficiency of 0.73 was attained at the principal streamflow gauge. The visualization of forcings and simulated responses further confirmed the model’s broad coherence. Closely replicating the somewhat contrasting groundwater level signatures observed in close proximity to one another was more elusive, presumably due to unresolved local subsurface heterogeneity. Finally, the impacts of various model simplifications on key predictions were assessed. Overall, our work demonstrates the feasibility and numerous attractions of applying integrated models – especially those that allow the stream network to evolve freely – in complex mountain systems, although certain outstanding challenges remain to be overcome if their global uptake is to increase.

DOI

https://doi.org/10.31223/X5RG7Q

Subjects

Hydrology

Keywords

snow, calibration, Mountain;, integrated hydrological modelling

Dates

Published: 2021-02-26 11:45

Last Updated: 2021-02-26 11:45

License

CC BY Attribution 4.0 International

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Conflict of interest statement:
None

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