The Gravity Recovery and Climate Experiment (GRACE) is now providing the first space based estimates of terrestrial water storage changes. Other than GRACE, there are no simple and reliable methods for monitoring terrestrial water storage over large areas, hence validating these new estimates is problematic. Furthermore, the spatial and temporal resolutions of GRACE are low compared to other hydrological measurement techniques, and the relative contributions of groundwater, soil moisture, snow, and surface water to total water storage variations are not well understood. Here we compare land surface model, water budget, and ground observation based estimates of groundwater, soil moisture, snow water equivalent, and total water with GRACE derived terrestrial water storage changes. Comparisons demonstrate that GRACE based mass variations do, indeed, reflect the redistribution of terrestrial water storage. The results also provide insight towards the challenges of deconvolving the individual contributions of the storage components and utilizing the GRACE data for constraining higher resolution hydrometeorological investigations.