Featuring Dr. Bridget Scanlon, Senior Research Scientist, The University of Texas at Austin, Jackson School of Geosciences

Although we increasingly rely on models and satellites to evaluate global water resources, their reliability is questionable. Unlike past research that compared modeled river discharges with monitored discharges, our work focuses on comparing modeled land water storage (snow, surface water, soil moisture and groundwater) trends to storage trends from Gravity Recovery and Climate Experiment (GRACE) satellites.

Likened to giant weighing scales in the sky, GRACE satellites have monitored monthly changes in land water storage globally since their launch in 2002. The satellites show that global land water storage, summed over 186 river basins, increased over the past decade, although models show decreasing global water storage. This suggests opposing contributions to global mean sea level, with GRACE indicating a negative contribution to sea level and models indicating a positive contribution.

While there is considerable interest in global scale analyses, water management generally occurs at the river basin scale, with models underestimating large decadal (2002–2014) trends in water storage relative to GRACE satellites. Comparing models with GRACE highlights potential areas of future model development, particularly simulated water storage. The inability of models to capture large decadal water storage trends based on GRACE indicates that model projections of climate and human induced water storage changes may be underestimated.

Dr. Bridget Scanlon leads the Sustainable Water Resources Program at The University of Texas at Austin. A hydrologist and senior research scientist, Scanlon was elected a member of the National Academy of Engineering in 2016.