Using satellites to detect groundwater levels

May 2, 2019



Globally, climate change and population growth will put increasing pressure on the availability of water resources in the coming decades leading to low water levels and droughts in some regions. Groundwater is a critically important water resource as it is used by industry, agriculture, and municipalities, and is essential for maintaining healthy aquatic ecosystems.  


There are many ways of detecting and measuring groundwater levels, one of which has been developed by the Gravity Recovery and Climate Experiment (GRACE) satellite mission which is sponsored by the National Aeronautics and Space Administration (NASA) and the German Aerospace Centre. The technique involves two satellites flying in a polar orbit that are continuously changing in speed and distance relative to each other due to highs and lows in the Earth’s gravity field. Since fluctuations in terrestrial water storage is the only process that can affect the Earth’s gravity field to any significant degree, the changes in the speed and distance between the satellites can be translated into a map of Earth’s gravity for a given time period, which can then be converted into groundwater levels.


Hachborn et al. (2017) sought to assess whether GRACE data could be used to detect changes in groundwater levels in southern Ontario and particularly, if the data could be useful in detecting and monitoring low water regions. Despite being located within the Great Lakes and St Lawrence River basins (which collectively are the largest freshwater system in the world), southern Ontario has experienced low water levels and drought conditions in recent decades.


At the time of the study, Ontario was only using precipitation and stream gauges to assess low water conditions. However, the province’s Ministry of Environment and Climate Change has also been monitoring groundwater since 1946 through a system called the Provincial Groundwater Monitoring Network (PGMN). Hachborn et al. (2017) obtained groundwater data for 48 PGMN wells located in southern Ontario that were monitored between 2003 and 2013. These data were compared against data provided by GRACE for the same time period and region.


Overall, there was a strong correlation between PGMN and GRACE-derived groundwater levels indicating that GRACE could be a useful resource for detecting and monitoring groundwater. The authors suggest that the GRACE data, which was publicly available, could be useful to water resource managers operating on a limited budget and for detecting fluctuating groundwater levels in remote regions that are difficult to access overland.


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Hachborn E, Berg A, Levison J, Ambadan JT. 2017. Sensitivity of GRACE-derived estimates of groundwater-level changes in southern Ontario, Canada. Hydrogeology Journal. 25(8):2391-2402.