Abstract:
Rivers act as a source of freshwater for terrestrial life, yet the discharges are poorly documented since the existing
direct observations are inadequate and some observation stations have been interrupted or discontinued. Discharge
estimates using remote sensing thus have a great potential to supplement ground observations. There
are remote sensing methods established to estimate discharge based on single parameter derived relationships;
however, they are limited to specific sections due to their empirical nature. In this study, we propose an innovative
method to estimate daily discharges for continental rivers (with river channel widths N800 m (Birkett and
Beckley, 2010)) using two satellite derived parameters.Multiple satellite altimetry data andModerate Resolution
Imaging Spectroradiometer (MODIS) data are used to provide a time series of river stages and effective river
width. The derived MODIS and altimetry data are then used to optimize unknown parameters in a modified
Manning's equation. In situ measurements are used to derive rating curves and to provide assessments of the estimated
results. The Nash–Sutcliffe efficiency values for the estimates are between 0.60 and 0.97, indicating the
power of the method and accuracy of the estimations. A comparisonwith a previously developed empirical multivariate
equation for estimating river discharge shows that our method produces superior results, especially for
large rivers. Furthermore, we found that discharge estimates using both effective river width and stage information
consistently outperform those that only use stage data.
