Understanding the hydrodynamics of the Congo

Whilst the global significance of large basin wetland hydrology and biogeochemistry is undisputed, considerable uncertainty surrounds estimates of these processes. Until very recently, available data sources or models have been incapable of resolving the spatial or temporal dynamics of floodplain inundation within these freshwater systems, with the notable exception of the Amazon basin. It is likely that not accounting for such large scale dynamics will have a significant impact on the estimates of hydrological and biogeochemical fluxes for water resources management under a changing climate on a global scale. An obvious solution to this problem is to use two-dimensional hydrodynamic models to simulate inundation over floodplains. Such modelling has, until recently, been prevented by a lack of available data. The Congo basin, the world’s second largest freshwater resource (Figure 1) is a prime example of a largely ungauged and understudied hydrodynamic system. However, developments in remote sensing data capture mean that sufficient topography, flow, water level and inundation data now exist that can be used to drive and validate such a hydrodynamic model.

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Figure 1: A MODIS false colour image (bands 7, 4, 1 on R, G, B) showing parts of the complex river network of the Congo basin, the second largest in the world after the Amazon (© NASA).

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Figure 2: Measurements of changes in water level (∂h/∂t) superimposed on SRTM elevation maps in [A] Amazon and [B] Congo. Spatial patterns of temporal water level changes are measured from repeat-pass interferometric JERS-1 SAR. Locations without interferometric measurements were not flooded during at least one of the overpasses (Jung et al., 2010). Note the rather smoothly varying valley slope gradient in the Amazon water levels [A] as opposed to the very diffuse gradients in the Congo levels [B].

Preliminary investigatory studies using largely remotely sensed data sets have alluded to the fact that the Congo River basin is hydrodynamically very distinct from the Amazon River basin (Figure 2). These initial findings suggest that the world's largest floodplain water systems are rather unique and hence their functioning cannot be generalised in the way we are able to do for smaller, more commonly studied, river reaches. However, this hypothesis requires much more rigorous evaluation. The aim of this research project is therefore to provide the first rigorous analysis of the hydrodynamics of the Congo river-floodplain system in order to answer some fundamental science questions.

Dr Guy Schumann
University of Bristol

Guy was awarded a Research Project Grant in November 2011; providing £137,915 over 36 months.