Satellite-based hydrological dynamics of the world's largest continuous wetland

We investigate the potential for closing the water balance purely from remote sensing (RS) sources and quantify the hydrological dynamic of the Pantanal (Brazil), the world's largest continuous wetland. We use 10-year time series of total water storage changes (ΔS) derived from GRACE and the balance between precipitation (P) derived from TRMM and evapotranspiration (ET) derived from MOD16, as well as the overall vegetation response (EVI2) to water availability. The GRACE-estimates of total water storage were consistent with in situ measurements from the Ladário gauge station. Despite the coarse spatial resolution of GRACE, its estimates were able not only to represent the hydrological regime of the entire basin but also its internal variability. The total water storage change estimates correlated well with precipitation (r = 0.87), evapotranspiration (r = 0.83), and vegetation greenness (r = 0.85), particularly when a two to three month time lag was considered. Likewise, the MODIS-derived vegetation greenness was consistent with variations in precipitation (r = 0.77) and evapotranspiration (r = 0.79). Nevertheless, we found that the water balance could not be closed with these data. Inferred runoff was greatly overestimated due mainly to an underestimation of ET. The uncertainty in the inputs and scarce validation data were limiting factors.