G-MONARCH: Gravity-MONitoring for Alpine Research Catchment Hydrology

Wider research context: Snow water equivalent is an essential climate variable and has vital importance on the water cycle and the wellbeing of billions of people living in and downstream of mountain catchments. Estimating the amount and the spatiotemporal distribution of snow is currently considered as one of the most important challenges in alpine hydrology. Besides, it is extremely difficult to measure or estimate other alpine water storage components, e.g. karst reservoirs, and to examine the relationship between precipitation, evapotranspiration, storages, internal fluxes and discharge. Innovation: The Zugspitze Geodynamic Observatory Germany (ZUGOG) with its worldwide unique installation of a superconducting gravimeter at Mount Zugspitze on top of a well-instrumented, snow dominated high-alpine catchment is used as a novel hydrological sensor system for the direct, integral and non-invasive observation of the gravity effect of water storage variations. Due to its geological situation, the catchment itself can be regarded as a natural lysimeter allowing for detailed mass balance studies. Objectives: We will use this unique instrumental setup in synthesis with detailed physically-based and spatially distributed snowpack monitoring and modelling and karst- hydrological modelling of different complexity. The overall research question to be addressed is, to what extent the snow-hydro-gravimetric approach can contribute to a better understanding and quantification of hydrological processes, states and fluxes in high-alpine areas that can be transferred to other regions worldwide. Approach: Important steps that will be addressed are i) the provision of snow-hydro-meteorological observations for initial and boundary conditions regarding model setup, calibration and validation; ii) the improvement of the gravimeter modelling and enhancement of further gravimetric observations within the test site providing integral mass change information for conditioning the model; iii) the development of snow-hydro-gravimetric model setups to describe the spatiotemporal hydrological mass and gravimetric signal changes, including the embedding into an uncertainty estimation framework; and iv) reaching an overall synthesis on the additional value of the gravimetric signal for snow-hydrological modelling in high-alpine sites.