Technical note: Introduction of a superconducting gravimeter as novel hydrological sensor for the Alpine research catchment Zugspitze

Abstract

Abstract. GFZ (German Research Centre for Geosciences) set up the Zugspitze Geodynamic Observatory Germany with a worldwide unique installation of a superconducting gravimeter at the summit of Mount Zugspitze on top of the Partnach spring catchment. This high alpine catchment is well instrumented, acts as natural lysimeter and has significant importance for water supply to its forelands, with a large mean annual precipitation of 2080 mm and a long seasonal snow cover period of 9 months, while showing a high sensitivity to climate change. However, regarding the majority of alpine regions worldwide, there is only limited knowledge on temporal water storage variations due to sparsely distributed hydrological and meteorological sensors and the large variability and complexity of signals in alpine terrain. This underlines the importance of well-equipped areas such as Mount Zugspitze serving as natural test laboratories for improved monitoring, understanding and prediction of alpine hydrological processes. The observatory superconducting gravimeter, OSG 052, supplements the existing sensor network as a novel hydrological sensor system for the direct observation of the integral gravity effect of total water storage variations in the alpine research catchment at Zugspitze. Besides the experimental set-up and the available data sets, the gravimetric methods and gravity residuals are presented based on the first 27 months of observations from 29 December 2018 to 31 March 2021. The snowpack is identified as being a primary contributor to seasonal water storage variations and, thus, to the gravity residuals with a signal range of up to 750 nm s−2 corresponding to 1957 mm snow water equivalent measured with a snow scale at an altitude of 2420 m at the end of May 2019. Hydro-gravimetric sensitivity analysis reveal a snow–gravimetric footprint of up to 4 km distance around the gravimeter, with a dominant gravity contribution from the snowpack in the Partnach spring catchment. This shows that the hydro-gravimetric approach delivers representative integral insights into the water balance of this high alpine site.

Environmental and anthropogenic gravity contributions at the Þeistareykir geothermal field, North Iceland

“…Gitlein et al (2013) modelled the combined gravity contributions of local and global atmospheric mass changes and applied them for reduction of superconducting gravity data, which improved the residuals by about 15% compared to the standard air pressure reduction with an admittance of −0.3 µGal hPa −1 . Voigt et al (2021) used a superconducting gravity meter for hydrological monitoring of Mount Zugspitze and identified the snowpack as the primary contributor to seasonal water storage variations, with a snowgravimetric footprint (i.e. snow related gravity contributions > 10 -4 µGal) of up to 4 km distance around the gravity meter.…”

An empirically-derived hydraulic head model controlling water storage and outflow over a decade in degraded permafrost rock slopes (Zugspitze, D/A)

“…Because of this dynamic, climate-change-induced variations in the snow cover will strongly affect water availability in the RCZ (Weber et al, 2016). Furthermore, Voigt et al (2021) used relative gravity measurements to detect water storage variations in the RCZ with promising results. Still, the only known measurements of water discharge in shallow unsaturated bedrock were conducted for measuring persistent organic pollutants in shallow percolated water (Levy et al, 2017), using the same loggers as in this study.…”

Superconducting Gravimeters: A Novel Tool for Validating Remote Sensing Evapotranspiration Products

“…Equation ( 2) defines the radius of influence of the SG, which depends on the depth z. The dependence on depth explains why different radii of influence ranging from 50 to 4000 m are reported in the literature (e.g., [8,12,49]). Since the mean groundwater depth in the study site is 13 m, a radius of influence of less than 1300 m would be expected.…”

“…where ET, P, and Rs are cumulative ET, precipitation, and runoff (in mm), respectively, during an arbitrary period of time Δt = ti − ti−1, and Δ𝑆 represents the water storage Equation ( 2) defines the radius of influence of the SG, which depends on the depth z. The dependence on depth explains why different radii of influence ranging from 50 to 4000 m are reported in the literature (e.g., [8,12,49]). Since the mean groundwater depth in the study site is 13 m, a radius of influence of less than 1300 m would be expected.…”