GLOBAL ANALYSIS OF THE ROLE OF THE GRACE SATELLITES IN WATER RESOURCE ASSESSMENTS

Limited water-resource monitoring in many regions globally underscores the value of remote sensing for assessing spatiotemporal variability in water resources. Here we evaluate water storage changes using GRACE satellite data for the past decade (2003 – 2013) in ~60 basins globally. Seasonal variations in water storage dominate the signal in many basins in humid tropical regions. Examples of long-term trends in water storage include increases in West Africa (e.g. Niger Basin) that are attributed to land use change, decreases in Tigris Euphrates related to drought, and decreases in the IndoGangetic basin related to irrigation. Some basins show increases and decreases within the decade, such as the Murray Darling basin with decreases during the millennial drought followed by large scale increase after 2010. Disaggregating total water storage into groundwater storage is more problematic because of uncertainties in soil moisture storage and lack of data to compare with remote sensing based estimates. GRACE satellites provide a valuable contribution to trends in global scale water resources in response to climatic and anthropogenic forcing.