GRACE storage-runoff hystereses reveal the dynamics of regional watersheds
Citation:
Sproles, E., S. Leibowitz, J. Reager, P. Wigington, J. Famiglietti, AND S. Patil. GRACE storage-runoff hystereses reveal the dynamics of regional watersheds. HYDROLOGY AND EARTH SYSTEM SCIENCES. EGS, 19:3253-3272, (2015).
Impact/Purpose:
Data from the Gravity Recovery and Climate Experiment (GRACE) satellites provide a novel dataset for understanding changes in the amount of water stored across and through the surface of the Earth. Previous GRACE studies focused on describing current and previous hydrologic conditions. We advance regional-scale hydrology, by demonstrating for the first time the relationship between storage (from GRACE) and stream flow. We also use GRACE as a predictive tool, effectively forecasting stream flow later in the water year. Such predictions could provide greater clarity and validation for model-based forecasts presently used by water resource managers. Our work focuses on the Columbia River Basin, but is widely applicable across the globe, and could prove to be particularly useful in regions with minimal hydrologic data measurements.
Description:
Watersheds function as integrated systems where climate and geology govern the movement of water. In situ instrumentation can provide local-scale insights into the non-linear relationship between streamflow and water stored in a watershed as snow, soil moisture, and groundwater. However, there is a poor understanding of these processes at the regional scale—primarily because of our inability to measure water stores and fluxes in the subsurface. Now NASA’s Gravity Recovery and Climate Experiment (GRACE) satellites quantify changes in the amount of water stored across and through the Earth, providing measurements of regional hydrologic behavior. Here we apply GRACE data to characterize for the first time how regional watersheds function as simple, dynamic systems through a series of hysteresis loops. While the physical processes underlying the loops are inherently complex, the vertical integration of terrestrial water in the GRACE signal provides process-based insights into the dynamic and non-linear function of regional-scale watersheds. We use this process-based understanding with GRACE data to effectively forecast seasonal runoff (mean R2 of 0.91) and monthly runoff (mean R2 of 0.77) in three regional-scale watersheds (>150,000 km2) of the Columbia River Basin, USA.
