Application of TopoFlow, a spatially distributed hydrological model, to the Imnavait Creek watershed, Alaska

[1] This study presents the application of the hydrological model TopoFlow to the Imnavait Creek watershed, Alaska, United States. It summarizes the hydrologically important processes in this arctic basin, and focuses on the modeling of the hydrological processes in 2001. The model is evaluated for its capability to reproduce the different components of the hydrological cycle. Model simulations are done for different climate change scenarios to evaluate the impacts on the hydrology. Imnavait Creek (similar to 2 km(2)) is underlain by continuous permafrost, and two features characterize the channel network: The stream is beaded, and numerous water tracks are distributed along the hillslopes. These facts, together with the constraint of the subsurface system to the shallow active layer, strongly influence the runoff response to rain or snowmelt. Climatic conditions vary greatly during the course of the year, providing a good testing of model capabilities. Simulation results indicate that the model performs quantitatively well. The different components of the water cycle are represented in the model, with refinements possible in the small-scale, short-term reproduction of storage-related processes, such as the beaded stream system, the spatial variability of the active layer depth, and the complex soil moisture distribution. The simulation of snow melt discharge could be improved by incorporating an algorithm for the snow-damming process.