MONITORING TERRESTRIAL WATER VARIATIONS FROM SPACE USING GRACE

Groundwater is both a vital resource and a useful indicator of hydroclimatic variability. Soil moisture is the primary source of water available to plants, and it also affects atmospheric processes through its control of evapotranspiration. In the United States, groundwater storage and soil moisture are somewhat well monitored, and measurement records are freely and easily accessible. Outside of the U.S., hydrological variables are often not monitored systematically, and even where they are the data are rarely centralized and publicly available. Since 2002 NASA’s Gravity Recovery and Climate Experiment (GRACE) satellite mission has delivered gravity field observations which have been used to infer variations in total terrestrial water storage (the sum of groundwater, soil moisture, snow and ice, and surface waters) at regional to continental scales. Challenges to using GRACE for hydrology include its relatively coarse spatial and temporal resolutions, its inability to differentiate the terrestrial water storage components, and typical 2-4 month data latency. In this presentation I will describe progress to date on overcoming these challenges and applying GRACE, together with other observations and models, for quantifying groundwater depletion, monitoring droughts, and assessing flood potential in the U.S. and worldwide.