The GRACE twin satellite mission has proven to deliver valuable data for river basin water balance studies. Hydrological applications include river basin scale (> 5 10^5 km^2) estimation of terrestrial water storage dynamics, total streamflow and evapotranspiration. Recently, a high resolution (1 degree) distributed GRACE data set was made available. In this study we investigate the potential of distributed GRACE measurements to estimate spatially variable terrestrial water storage changes in the Colorado River basin. For the period 2003-2006 we correlate 1 degree GRACE data with distributed hydrologic simulations and in-situ observations of snow water equivalent (SWE), reservoir storage and streamflow.

We find that: (1) there exist a high correlation between VIC simulations of terrestrial storage anomalies and the distributed GRACE data for most of the Colorado River basin (CRB); (2) Upper CRB correlation is dominated by snow storage changes, while Lower CRB is dominated by groundwater storage changes, and soil moisture affects the entire CRB; (3) correlation is highest for wet periods, such as 2005; (4) VIC tends to overestimate storage dynamics in the Upper CRB, whereas VIC underestimates storage dynamics in Lower CRB; (5) strong agreement also exists with in-situ observations of SWE and reservoir storage, and (6) streamflow correlations are maximum for time lags of 0-4 months, depending on location of the sub-basin (highest lags in Upper CRB).