Coupling MODIS and Radar Altimetry Data for Discharge Estimation in Poorly Gauged River Basins

The capability of coupling measurements of river velocity derived from Moderate Resolution Imaging Spectroradiometer (MODIS) and water levels derived from ENVISAT Advanced Radar Altimeter (RA-2) for river discharge estimation is thoroughly investigated. The method is applied even considering the possible unavailability of the river cross-section survey by using the entropy theory for reconstructing the bathymetry. The discharge estimation accuracy is validated using in situ measurements along the Po River (Northern Italy) where daily observations are available for the period 2005-2010. The agreement with the observed discharge is fairly satisfactory with coefficient of correlation of 0.91 and relative root-mean-square error (RMSE) of  ~  37% on average. Therefore, the coupling of the two sensors provides, with a good level of accuracy, the hydraulic quantities to use for discharge estimation. These results are particularly significant for the forthcoming European Space Agency Sentinel-3 mission, in which a visible-near infrared multispectral sensor and an altimeter will be onboard the same satellite platform providing significant improvements in terms of vertical accuracy and spatial-temporal resolution.