Gravity-based Monitoring of Terrestrial Water Storage

Gravity-based monitoring exploits variations in Earth’s gravity field to infer changes in terrestrial water storage (TWS), encompassing soil moisture, surface water, snow, and groundwater. Satellite missions like GRACE and its successor GRACE-FO measure minute shifts in Earth’s mass distribution by tracking distance changes between twin spacecraft. These data provide monthly, basin-scale estimates of total water storage anomalies at resolutions of a few hundred kilometres. By subtracting contributions from snow, soil moisture and surface reservoirs—derived from auxiliary models or observations—researchers isolate groundwater changes. This approach offers an unparalleled, global view of water storage dynamics in regions lacking dense in situ networks. It has revealed critical trends such as large-scale aquifer depletion in semiarid regions, seasonal hydrological cycles in monsoon and temperate zones, and the impacts of climate variability and water-management interventions. Integrating gravity data with land surface models through data assimilation further enhances the accuracy of water budget components, supports drought assessment and informs sustainable water-resource management. As gravity missions continue and methods mature, gravity-based monitoring is becoming an indispensable tool for assessing hydrological responses to anthropogenic pressures and climate change at regional to global scales.

Research from Nature Portfolio

Recent studies have quantified the impact of large-scale engineering schemes on groundwater recovery. Investigations into inter-basin water transfer demonstrated that diversions to Beijing contributed roughly 3.6 km3 to groundwater storage recovery between 2006 and 2018, accounting for about 40 percent of observed replenishment alongside precipitation increases and irrigation controls. Another line of work has addressed uncertainties in satellite-based groundwater depletion estimates. By incorporating constrained forward modelling with ancillary hydrological information, researchers refined GRACE estimates over the Northwest India Aquifer, reconciling satellite-derived depletion rates with well-based measurements and highlighting the importance of a priori information to improve spatial patterns of estimated groundwater change.

Gravity-based Monitoring of Terrestrial Water Storage publication trend

The graph below shows the total number of articles in gravity-based monitoring of terrestrial water storage across all publications each year (not limited to Nature Index journals).

Technical terms

GRACE (Gravity Recovery and Climate Experiment): A satellite mission that measures temporal changes in Earth’s gravity field to derive terrestrial water storage variations.

Terrestrial Water Storage (TWS): The total quantity of water stored on and below the land surface, including soil moisture, snow, surface water and groundwater.

Mascon: “Mass concentration” approach that partitions gravity data into discrete regions, improving spatial resolution and reducing noise in water storage estimates.

Data Assimilation: A computational technique that merges observed data with numerical model outputs to produce improved estimates of hydrological variables.

References

1. South-to-North Water Diversion stabilizing Beijing’s groundwater levels. Nature Communications (2020).
2. Have GRACE satellites overestimated groundwater depletion in the Northwest India Aquifer?. Scientific Reports (2016).
3. Global GRACE Data Assimilation for Groundwater and Drought Monitoring: Advances and Challenges. Water Resources Research (2019).
4. Monitoring Groundwater Storage Changes Using the Gravity Recovery and Climate Experiment (GRACE) Satellite Mission: A Review. Remote Sensing (2018).