Integration of MODIS and Radar Altimetry Data for River Discharge Estimation from Space

The study integrates data provided by Moderate Resolution Imaging Spectroradiometer, MODIS, onboard AQUA satellite and by RA-2 altimeter onboard ERS-2 and ENVISAT satellites for river discharge estimation along the Po River (northern Italy). The discharge is estimated by multiplying the velocity estimated from MODIS by the flow area computed considering the water level derived by altimetry data. In the case of river cross-section survey not available, the entropy theory may be applied for reconstructing the bathymetry starting from the water surface elevation observed or retrieved by the altimeter. The discharge estimation is validated using in-situ measurements of the nearest hydrometric station where daily observations are available for the period from February 2005 to August 2010. The agreement with the observed discharge is fairly satisfactory with coefficient of correlation equal to 0.91 and root mean square error of 37 % against observed discharge. The results suggest that the proposed methodology has potential applications from the forthcoming SENTINEL-3 mission, in which two similar sensors will be onboard the same satellite platform and where significant improvements will be obtained in terms of vertical accuracy and spatial and temporal resolution.