6. Workshop Alpine Hydrologie

The understanding and quantification of the high-alpine water balance is very challenging. This includes that the estimation of the amount of snow and its spatiotemporal distribution in complex terrain is currently considered as one of the most important challenges in Alpine Hydrology. Since 2019, a superconducting gravimeter has been in operation at the Zugspitze Geodynamic Observatory Germany on top of a snow-dominated and karstified high-alpine site in the Northern European Alps. Hydro-gravimetry is a non-invasive method of observing temporal gravity variations after the reduction of all other geophysical signals as the integral of all hydrological mass variations. The gravimetric signals include short-term, seasonal and long-term cryospheric and hydrological mass changes in a few kilometres scale radius. At the site of Mt. Zugspitze, the seasonal snowpack variation has the largest impact on the gravimetric signal, however, also fluxes and storage changes, such as ice melt, the movement of water in the karstic vadose zone and sublimation can be detected. The spatiotemporal gravimetric contribution of the snowpack was simulated with the physically-based snowpack model Alpine3D including a satellite-based snow depth image derived by stereo photogrammetry for precipitation and snow pattern scaling. The snowpack model was coupled with the routing scheme of the conceptual hydrological model GR4J, which was calibrated and validated against discharge measurements at Partnach Urspung (KGE_cal: 0.91 ± 0.01; KGE_val: 0.87 ± 0.03). The results for a period of more than seven years shows a high agreement between the observed and simulated gravity signals (R²=0.98; RMSE=55 nm/s²). Overall, this innovative monitoring approach combined with coupled snow-hydrological modelling has a high potential to contribute to a better understanding and quantification of cryo-hydrological processes and storages in snow-dominated high-alpine catchments.