"Disagreements in Land Water Storage Trends between GRACE Satellites and Global Models"
Dr. Bridget R. Scanlon
Senior Research Scientist, Sustainable Water Resources
Bureau of Economic Geology
While satellites and global modeling are increasingly being used to assess global water issues, such as groundwater depletion, water scarcity, and sea level rise, the results may not be highly reliable. Here we provide the first comprehensive comparison of water storage trends from satellites (Gravity Recovery and Climate Experiment [GRACE]) and global hydrologic (WGHM and PCR-GLOBWB) and land surface (LSMs, GLDAS) models in 186 river basins. Results show marked differences between GRACE and models and among models with positive net land water storage trends (2002–2014), summed over all basins, for GRACE (~+60 km3/yr) but negative trends for models (-5 to -492 km3/yr), contributing opposite trends to global mean sea level. The models mostly underestimate water storage depletions related to irrigation and storage increases related to climate variability. Correlations in storage trends between GRACE and models and among models is extremely low. Understanding the differences in storage trends between GRACE and models should help advance future GRACE processing and model development and may benefit from integrating satellites and models.