Greater Water Surface Variability Revealed by New Congo River Field Data: Implications for Satellite Altimetry Measurements of Large Rivers

Large river hydrodynamics studies inform global and regional issues pertaining to biogeochemical cycling, ecology, water availability, and flood risk. Such studies rely increasingly on satellite measurements, but these are limited by resolution, coverage, and uncertainty and their inability to directly measure bathymetry or discharge. We obtain new in situ data covering 650 km of the Congo's main stem, including elusive bathymetry and discharge measurements that complement space‐borne data sets. Our key findings relate to our water surface elevation measurements, which show that spatial coverage of existing satellite altimetry for deriving river water surface profiles may be adequate through the globally important Cuvette Centrale but is not at its outlet where our field data reveal significant spatial variability in water surface slope. The findings have implications for altimetry‐based hydrodynamics studies of other large rivers, such as those that involve estimating discharge or modeling multichannel river hydraulics.