Determining the validity of satellite-based measurements of groundwater level changes in Southern Ontario

In Ontario, low water conditions are currently assessed using precipitation and stream gauges by Conservation Authorities and the Ministry of Natural Resources and Forestry. Climate change studies have shown that it will become more important to understand Ontario’s groundwater resources in the future. Regional groundwater storage changes are not currently measured using satellite data in Ontario. In this study, the Gravity Recovery and Climate Experiment (GRACE) data are analyzed for southern Ontario from 2003 to 2013 in order to determine the applicability of GRACE for monitoring groundwater storage. Terrestrial water storage data from GRACE was corrected for soil moisture and snow water equivalent using the Global Land Data Assimilation System (GLDAS) model to obtain monthly groundwater storage (GWS) values. GWS values were also created by multiplying groundwater well levels from the Provincial Groundwater Monitoring Network (PGMN) by a specific yield value. Comparisons of GRACE-derived GWS to well-based GWS data determined that GRACE is sufficiently sensitive to obtain a meaningful signal in southern Ontario. Stream gauge measurements were also used to observe groundwater-surface water interactions in the region in comparison to GWS. Results show that GWS values produced by GRACE are useful for identifying regional changes in groundwater storage in areas with limited available hydrogeological characterization data. Results also indicate that GRACE may have an ability to forecast changes in groundwater storage which will become useful for climate shifts in the near future.