Continuous Monitoring with a Superconducting Gravimeter As a Proxy for Water Storage Changes in a Mountain Catchment

Abstract. The quantification of volumetric ice and water contents in active rock glaciers is necessary to estimate their role as water stores and contributors to runoff in dry mountain catchments. In the semi-arid to arid Andes of Argentina, active rock glaciers potentially constitute important water reservoirs due to their widespread distribution. Here however, water storage capacities and their interannual changes have so far escaped quantification in detailed field studies. Volumetric ice and water contents were quantified using a petrophysical four-phase model (4PM) based on complementary electrical resistivities (ERT) and seismic refraction tomographies (SRT) in different positions of Dos Lenguas rock glacier in the Upper Agua Negra basin, Argentina. We derived vertical and horizontal surface changes of the Dos Lenguas rock glacier, for the periods 2016–17 and 2017–18 using drone-derived digital elevation models (DEM). Interannual water storage changes of −36 mm yr−1 and +27 mm yr−1 derived from DEMs of Difference (DoD) for the periods 2016–17 and 2017–18, respectively, indicate that significant amounts of annual precipitation rates can be stored in and released from the active rock glacier. Heterogeneous ice and water contents show ice-rich permafrost and supra-, intra- and sub-permafrost aquifers in the subsurface. Active layer and ice-rich permafrost control traps and pathways of shallow ground water, and thus regulate interannual storage changes and water releases from the active rock glacier in the dry mountain catchment. The ice content of 1.7–2.0 × 109 kg in the active Dos Lenguas rock glacier represents an important long-term ice reservoir, just like other ground ice deposits in the vicinity, if compared to surface ice that covers less than 3 % of the high mountain catchment.

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Landscape-scale water balance monitoring with an iGrav superconducting gravimeter in a field enclosure

Hydrology and Earth System Sciences ◽

10.5194/hess-21-3167-2017 ◽

2017 ◽

Vol 21 (6) ◽

pp. 3167-3182 ◽

Cited By ~ 12

Author(s):

Andreas Güntner ◽

Marvin Reich ◽

Michal Mikolaj ◽

Benjamin Creutzfeldt ◽

Stephan Schroeder ◽

...

Keyword(s):

Time Series ◽

Water Balance ◽

Water Storage ◽

Superconducting Gravimeter ◽

Landscape Scale ◽

Temperate Climate ◽

Water Balance Components ◽

Climate Conditions ◽

The Road ◽

Field Deployment

Abstract. In spite of the fundamental role of the landscape water balance for the Earth's water and energy cycles, monitoring the water balance and its components beyond the point scale is notoriously difficult due to the multitude of flow and storage processes and their spatial heterogeneity. Here, we present the first field deployment of an iGrav superconducting gravimeter (SG) in a minimized enclosure for long-term integrative monitoring of water storage changes. Results of the field SG on a grassland site under wet–temperate climate conditions were compared to data provided by a nearby SG located in the controlled environment of an observatory building. The field system proves to provide gravity time series that are similarly precise as those of the observatory SG. At the same time, the field SG is more sensitive to hydrological variations than the observatory SG. We demonstrate that the gravity variations observed by the field setup are almost independent of the depth below the terrain surface where water storage changes occur (contrary to SGs in buildings), and thus the field SG system directly observes the total water storage change, i.e., the water balance, in its surroundings in an integrative way. We provide a framework to single out the water balance components actual evapotranspiration and lateral subsurface discharge from the gravity time series on annual to daily timescales. With about 99 and 85 % of the gravity signal due to local water storage changes originating within a radius of 4000 and 200 m around the instrument, respectively, this setup paves the road towards gravimetry as a continuous hydrological field-monitoring technique at the landscape scale.

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The benefits of gravimeter observations for modelling water storage changes at the field scale

Hydrology and Earth System Sciences ◽

10.5194/hess-14-1715-2010 ◽

2010 ◽

Vol 14 (9) ◽

pp. 1715-1730 ◽

Cited By ~ 23

Author(s):

B. Creutzfeldt ◽

A. Güntner ◽

S. Vorogushyn ◽

B. Merz

Keyword(s):

Measurement Techniques ◽

Water Storage ◽

Superconducting Gravimeter ◽

Calibration Data ◽

Field Scale ◽

Catchment Scale ◽

Individual Parameter ◽

State Variable ◽

Hydrological System ◽

Storage Term

Abstract. Water storage is the fundamental state variable of hydrological systems. However, comprehensive data on total water storage changes (WSC) are practically inaccessible by hydrological measurement techniques at the field or catchment scale, and hydrological models are highly uncertain in representing the storage term due to the lack of adequate validation or calibration data. In this study, we assess the benefit of temporal gravimeter measurements for modelling WSC at the field scale. A simple conceptual hydrological model is calibrated and evaluated against records of a superconducting gravimeter (SG), soil moisture, and groundwater time series. The model is validated against independently estimated WSC based on lysimeter measurements. Using gravimeter data as a calibration constraint improves the model results substantially in terms of predictive capability and variation of the behavioural model runs. Thanks to their capacity to integrate over different storage components and a larger area, gravimeters provide information on total WSC that can be used to constrain the overall status of the hydrological system in a model. The general problem of specifying the internal model structure or individual parameter sets can, however, not be solved with gravimeters alone.

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Modeling the Hydrological Effect on Local Gravity at Moxa, Germany

Journal of Hydrometeorology ◽

10.1175/jhm488.1 ◽

2006 ◽

Vol 7 (3) ◽

pp. 346-354 ◽

Cited By ~ 24

Author(s):

Shaakeel Hasan ◽

Peter A. Troch ◽

J. Boll ◽

C. Kroner

Keyword(s):

Transfer Function ◽

Hydrological Modeling ◽

Hydrological Model ◽

Water Storage ◽

Superconducting Gravimeter ◽

Hydrological Processes ◽

Earth Tides ◽

Time Averaging ◽

Distributed Hydrological Model ◽

High Positive Correlation

Abstract A superconducting gravimeter has observed with high accuracy (to within a few nm s−2) and high frequency (1 Hz) the temporal variations in the earth’s gravity field near Moxa, Germany, since 1999. Hourly gravity residuals are obtained by time averaging and correcting for earth tides, polar motion, barometric pressure variations, and instrumental drift. These gravity residuals are significantly affected by hydrological processes (interception, infiltration, surface runoff, and subsurface redistribution) in the vicinity of the observatory. In this study time series analysis and distributed hydrological modeling techniques are applied to understand the effect of these hydrological processes on observed gravity residuals. It is shown that the short-term response of gravity residuals to medium- to high-rainfall events can be efficiently modeled by means of a linear transfer function. This transfer function exhibits an oscillatory behavior that indicates fast redistribution of stored water in the upper layers (interception store, root zone) of the catchment surrounding the instrument. The relation between groundwater storage and gravity residuals is less clear and varies according to the season. High positive correlation between groundwater and gravity exists during winter months when the freezing of the upper soil layers immobilizes water stored in the unsaturated zone of the catchment. To further explore the spatiotemporal dynamics of the relevant hydrological processes and their relation to observed gravity residuals, a GIS-based distributed hydrological model is applied for the Silberleite catchment. Driven by observed atmospheric forcings (precipitation and potential evapotranspiration), the model allows the authors to compute the variation of water storage in three different layers: the interception store, the snow cover store, and the soil moisture store. These water storage dynamics are then converted to predicted gravity variation at the location of the superconducting gravimeter and compared to observed gravity residuals. During most of the investigated period (January 2000 to January 2004) predictions are in good agreement with the observed patterns of gravity dynamics. However, during some winter months the distributed hydrological model fails to explain the observations, which supports the authors’ conclusion that groundwater variability dominates the hydrological gravity signal in the winter. More hydrogeological research is needed to include groundwater dynamics in the hydrological model.

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Simulating the influence of water storage changes on the superconducting gravimeter of the Geodetic Observatory Wettzell, Germany

Geophysics ◽

10.1190/1.2992508 ◽

2008 ◽

Vol 73 (6) ◽

pp. WA95-WA104 ◽

Cited By ~ 51

Author(s):

Benjamin Creutzfeldt ◽

Andreas Güntner ◽

Thomas Klügel ◽

Hartmut Wziontek

Keyword(s):

Soil Moisture ◽

Water Storage ◽

Superconducting Gravimeter ◽

Spatiotemporal Variability ◽

Gravity Effect ◽

Snow Storage ◽

Superconducting Gravimeters ◽

Influence Of Water ◽

Gravity Signal ◽

Local Water

Superconducting gravimeters (SG) measure temporal changes of the Earth’s gravity field with high accuracy and long-term stability. Variations in local water storage components (snow, soil moisture, groundwater, surface water, and water stored by vegetation) can have a significant influence on SG measurements and — from a geodetic perspective — add noise to the SG records. At the same time, this hydrological gravity signal can provide substantial information about the quantification of water balances. A 4D forward model with a spatially nested discretization domain was developed to investigate the local hydrological gravity effect on the SG records of the Geodetic Observatory Wettzell, Germany. The possible maximum gravity effect was investigated using hypothetical water storage changes based on physical boundary conditions. Generally, on flat terrain, a water mass change of[Formula: see text] in the model domain causes a gravity change of [Formula: see text]. Simulation results show that topography increases this value to [Formula: see text]. Errors in the Digital Elevation Model can influence the results significantly. The radius of influence of local water storage variations is limited to [Formula: see text]. Detailed hydrological measurements should be carried out in a radius of [Formula: see text] around the SG station. Groundwater, soil moisture, and snow storage changes dominate the hydrological gravity effect at the SG Wettzell. Using observed time series for these variables in the 4D model and comparing the results to the measured gravity residuals show similarities in both seasonal and shorter-term dynamics. However, differences exist, e.g., the range comparison of the mean modeled [Formula: see text] gravity signal and the measured [Formula: see text] gravity signal, making additional hydrological measurements necessary to describe the full spatiotemporal variability of local water masses.

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SAGEEP2 Assessing Water Storage Changes on the Field Scale Combining Superconducting Gravimeter Observations with a Hydro-logical Model

Near Surface 2011 - 17th EAGE European Meeting of Environmental and Engineering Geophysics ◽

10.3997/2214-4609.20144488 ◽

2011 ◽

Author(s):

B. Creutzfeldt ◽

A. Güntner ◽

H. Wziontek ◽

B. Merz

Keyword(s):

Water Storage ◽

Superconducting Gravimeter ◽

Field Scale ◽

Logical Model

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The benefits of gravimeter observations for modelling water storage changes at the field scale

Hydrology and Earth System Sciences Discussions ◽

10.5194/hessd-7-2221-2010 ◽

2010 ◽

Vol 7 (2) ◽

pp. 2221-2260 ◽

Cited By ~ 4

Author(s):

B. Creutzfeldt ◽

A. Güntner ◽

S. Vorogushyn ◽

B. Merz

Keyword(s):

Measurement Techniques ◽

Water Storage ◽

Superconducting Gravimeter ◽

Calibration Data ◽

Field Scale ◽

Catchment Scale ◽

Individual Parameter ◽

State Variable ◽

Hydrological System ◽

Storage Term

Abstract. Water storage is the fundamental state variable of hydrological systems. However, comprehensive data on total water storage changes (WSC) are practically inaccessible by hydrological measurement techniques at the field or catchment scale, and hydrological models are highly uncertain in representing the storage term due to the lack of adequate validation or calibration data. In this study, we assess the benefit of temporal gravimeter measurements for modelling WSC at the field scale. A simple conceptual hydrological model is calibrated and evaluated against records of a superconducting gravimeter, soil moisture and groundwater time series. The model is validated against independently estimated WSC data. Using gravimeter data as a calibration constraint improves the model results substantially in terms of predictive capability and variation of the behavioural model runs. Thanks to their capacity to integrate over different storage components and a larger area, gravimeters provide generalised information on total WSC that is useful to constrain the overall status of the hydrological system in a model. The general problem of specifying the internal model structure or individual parameter sets can, however, not be solved with gravimeters alone.

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Assessing reliability of hydrological simulations through model intercomparison at the local scale in the Everest region

10.5194/hess-2017-401 ◽

2017 ◽

Author(s):

Judith Eeckman ◽

Santosh Nepal ◽

Pierre Chevallier ◽

Gauthier Camensuli ◽

Francois Delclaux ◽

...

Keyword(s):

Water Storage ◽

Local Scale ◽

High Mountain ◽

Physical Processes ◽

Central Himalayas ◽

Mountain Environments ◽

Mountain Catchment ◽

Spatio Temporal ◽

Surface Scheme ◽

Downstream Communities

Abstract. Understanding hydrological processes of high-altitude areas is vital because downstream communities depend on water resources for their livelihood. This paper compares the hydrological responses at the local scale of two models using different degrees of refinement to represent physical processes in sparsely instrumented mountainous Himalayan catchments. Two small catchments located in mid- and high- mountain environments were chosen to represent the very different climatic and physiographic characteristics of the Central Himalayas in the Everest region of eastern Nepal. This work presents the novelty of applying, at a small spatio-temporal scale and under the same forcing conditions, a fully distributed surface scheme based on mass and energy balance equations (ISBA surface scheme), and a semi-distributed calibrated model (J2000 hydrological model). A new conceptual module coupled to the ISBA surface scheme for flow routing is presented. The results show that both models describe the evapotranspiration, quick runoff and discharge processes in a similar way. The reliability of the simulations for these variables can therefore be considered as satisfactory. The differences in the structure and results of the two models mainly concern the water storage and flows in the soil, in particular for the high-mountain catchment. This conclusion suggests that the uncertainty associated with model structure is significant for water storage and flow in the soil.

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Landscape-scale water balance monitoring with an iGrav superconducting gravimeter in a field enclosure

10.5194/hess-2017-103 ◽

2017 ◽

Cited By ~ 1

Author(s):

Andreas Güntner ◽

Marvin Reich ◽

Michal Mikolaj ◽

Benjamin Creutzfeldt ◽

Stephan Schroeder ◽

...

Keyword(s):

Time Series ◽

Water Balance ◽

Water Storage ◽

Superconducting Gravimeter ◽

Landscape Scale ◽

Temperate Climate ◽

Water Balance Components ◽

Climate Conditions ◽

The Road ◽

Field Deployment

Abstract. In spite of the fundamental role of the landscape water balance for the Earth’s water and energy cycles, monitoring the water balance and its components beyond the point scale is notoriously difficult due to the multitude of flow and storage processes and their spatial heterogeneity. Here, we present the first field deployment of an iGrav superconducting gravimeter (SG) in a minimized enclosure for long-term integrative monitoring of water storage changes. Results of the field SG on a grassland site under wet-temperate climate conditions were compared to data provided by a nearby SG located in the controlled environment of an observatory building. The field system proves to provide gravity time series that are similarly precise as those of the observatory SG. At the same time, the field SG is more sensitive to hydrological variations than the observatory SG. We demonstrate that the gravity variations observed by the field setup are almost independent of the depth below the terrain surface where water storage changes occur (contrary to SGs in buildings), and thus the field SG system directly observes the total water storage change, i.e., the water balance, in its surroundings in an integrative way. We provide a framework to single out the water balance components actual evapotranspiration and lateral subsurface discharge from the gravity time series on annual to daily time scales. With about 99 % and 85 % of the gravity signal due to local water storage changes originating within a radius of 4000 and 200 meter around the instrument, respectively, this setup paves the road towards gravimetry as a continuous hydrological field monitoring technique at the landscape scale.

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

Hydrology and Earth System Sciences ◽

10.5194/hess-25-5047-2021 ◽

2021 ◽

Vol 25 (9) ◽

pp. 5047-5064

Author(s):

Christian Voigt ◽

Karsten Schulz ◽

Franziska Koch ◽

Karl-Friedrich Wetzel ◽

Ludger Timmen ◽

...

Keyword(s):

Snow Water Equivalent ◽

Water Storage ◽

Superconducting Gravimeter ◽

Technical Note ◽

Research Centre ◽

Mean Annual Precipitation ◽

Large Variability ◽

Spring Catchment ◽

Alpine Research ◽

Set Up

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.

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