On the contribution of remote sensing-based calibration to model
multiple hydrological variables in tropical regions
Abstract
The accuracy of hydrological model predictions is limited by
uncertainties in model structure and parameterization, and observations
used for calibration, validation and model forcing. While calibration is
usually performed with discharge estimates, the internal model processes
might be misrepresented, and the model might be getting the “right
results for the wrong reasons”, thus compromising model reliability. An
alternative is to calibrate model parameters with remote sensing (RS)
observations of the water cycle. Previous studies highlighted the
potential of RS-based calibration to improve discharge estimates,
focusing less on other variables of the water cycle. In this study, we
analyzed in detail the contribution of five RS-based variables (water
level (h), flood extent (A), terrestrial water storage (TWS),
evapotranspiration (ET) and soil moisture (W)) to calibrate a coupled
hydrologic-hydrodynamic model for a large Amazon sub-basin with
extensive floodplains. Single-variable calibration experiments with all
variables were able to improve discharge KGE from around 6.1% to 52.9%
when compared to a priori parameter sets. Water cycle representation was
improved with multi-variable calibration: KGE for all variables were
improved in the evaluation period. By analyzing different calibration
setups, a consistent selection of complementary variables for model
calibration resulted in a better performance than incorporating all RS
variables into the calibration. By looking at multiple RS observations
of the water cycle, inconsistencies in model structure and
parameterization were found, which would remain unknown if only
discharge observations were considered.