Greater Water Surface Variability Revealed by New Congo River Field Data: Implications for Satellite Altimetry Measurements of Large Rivers
Geophysical Research Letters
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
... 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. Plain Language Summary Understanding the dynamics of surface water along the world's large river channel systems is of major importance. For example, it controls the duration and extents of floods that sustain globally important floodplain and wetland ecosystems. However, this understanding remains poor for unmonitored systems where access is difficult. In this study, we report results from a field campaign covering 650 km of the Congo River. Key measurements of river depth, flow rate, velocity, and water surface elevation are combined with satellite measurements to characterize this system. We find flow conditions vary minimally along most of the 650 km surveyed. However, significant changes occur along a 150-km reach at the outlet of the Cuvette Centrale wetland region, and a comparison of different data sets shows that measurements of water surface elevation from space by satellites have insufficient coverage to detect major changes in the water surface at this location. These findings have important implications given the widespread use of these satellite measurements in a number of applications such as computer modeling of floods and the estimation of river flows from space.