Estimating River Discharge Using Satellite Observed River Width and Water Surface Elevation

Abstract

Estimating river discharge using remotely sensed measurements from satellites and unmanned aerial vehicles has growing interests in scientific research and engineering applications. NASA’s SWOT satellite has a mission to collect river data, including width and surface elevation, for environmental research. To support the mission, researchers have proposed many methods to estimate discharge from surface width. At-a-station hydraulic geometry (AHG) is the mostly common method that correlates flow discharge and surface with using a power relationship. However, the coefficients in the power function, the constant and the exponent, are distinct for each cross section. The study of these relationships for each cross section can reveal vital information that could be used to improve river discharge estimation. Therefore, this study’s objective is to investigate the variation of these relationships between cross sections, reaches, and rivers using data from 19 large rivers located across the world. In addition to the conventional AHG method, the piecewise and the dimensionless AHG approaches were also explored to examine their potentials for discharge estimation. The relationships between discharge and surface width were formulated for each cross section using these three different AHG approaches. The results showed that the piecewise AHG approach significantly improved discharge estimation over the conventional AHG method. The dimensionless AHG approach performed poorly for most of the rivers. No universal relations were found that were valid for all cross sections in a reach or a river. Although the power relation between discharge and width are apparent in all cross sections, the coefficients vary from sections to section regardless of the AHG approach that was applied. These results identify a limitation of AHG approaches for discharge estimation. Additional research in alluvial river geometric characteristics is needed to further improve discharge estimation.