Presentation / Talk

Flow and Temperature Dynamics in the Hydrologic Response of Alpine Catchments: Travel Time Formulation and Geomorphologic Signatures

We present a travel time formulation of water and energy transport at sub-catchment scale. The derived equations are implemented in Alpine3D, a physically-based model of snow processes, which provides the necessary boundary conditions to perform hydro-thermal response simulations of Alpine catchments. The model set-up accounts for advective and non- advective energy fluxes to perform spatially distributed simulations of streamflow and temperature in river networks having an arbitrary degree of geomorphological complexity. The model gives reliable predictions of streamflow and tem- perature, as shown by comparing modeled and measured hydrographs and thermographs at the outlet of the Dischma catchment (45 km2) in the Swiss Alps. Our model setup is applied to investigate the role of hillslope aspects, representing the main control on radiation and snowmelt patterns, in the flow regime of the study catchment. The distributed simu- lation results show that snowmelt-induced discharge exhibits a visible geomorphologic signature of aspects at sub-catch- ment scale, but this progressively fades out going from headwater streams to the outlet. Accordingly, the geomorphologic signature is scale-dependent: it is significant at small scales where the high aspect correlation generates predominant orientations but is lost at larger scales where aspects are de-correlated and different orientations are averaged out. We further apply the model to investigate the geomorphologic signature of drainage density in the thermal regime of the study catchment. The results show that the contribution of the advective energy fluxes becomes progressively smaller when the drainage density increases, while the one of the non-advective energy fluxes becomes larger. Moreover, such variations balance out at the catchment outlet, where the temperature signal is not sensitive to the increasing drainage density. The relevance of the performed invetigations stems from the increasing scientific interest concerning the impacts of the warming climate on water resources management and temperature-influenced ecological processes.

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