Bridget Scanlon, Ph.D.
Senior Research Scientist
Bureau of Economic Geology
Jackson School of Geosciences
The University of Texas at Austin
Two decades of GRACE (Gravity Recovery and Climate Experiment) satellite data provide detailed insights into our understanding of global hydrology. GRACE satellites measure variations in Earth’s gravity which are controlled mostly by water storage changes, such as those related to droughts, floods, ice melting, and human water use. The vertically integrated land total water storage (TWS) variations monitored by GRACE include surface water, soil moisture, and groundwater. GRACE is like a scale in the sky, providing the big picture, and ideal for spatiotemporal variability in land water storage. Attribution analysis of GRACE water storage variability to human and climate drivers has greatly advanced over time. GRACE satellites were the first to show large scale groundwater depletion in the IndoGangetic Basin. Interpretation of GRACE water storage has improved by integrating additional data on human intervention (e.g., groundwater pumping, water use, land use change) and climate drivers (e.g., precipitation, drought indices). Some basins show combined effects of human intervention amplifying or dampening climate effects. Recent studies show the value of ground-based monitoring and regional modeling to provide long-term context for GRACE data with large scale net increases in water storage in the IndoGangetic Basin and Northwest US over the past century. The visual power of GRACE data helped communicate water storage variability to the public and influence water policy in many regions, including India and the US.