Storage changes over the middle reach of the Congo River: comparison between its upper and lower middle reaches

Abstract:

Several studies have been conducted to quantify and characterize terrestrial water storage changes over the Congo’s wetlands, especially focusing on the central Congo Basin, or Cuvette Centrale, where vast wetlands can be found. The annual variations of the total storage changes over the Cuvette Centrale wetlands were estimated to range between ~20 km³ to ~30 km³ using PALSAR ScanSAR, Envisat altimetry, and GRACE RL05 data, mostly controlled by surface water. Furthermore, based on precipitation minus evapotranspiration anomalies, and a hydraulic analysis using Envisat altimetry data, the source of the Cuvette Centrale wetland’s water is likely to be local upland runoff rather than the fluvial process of river-floodplain exchange as in the Amazon.

On the other hand, if we consider the Cuvette Centrale as the lower middle reach of the Congo, little attention has been paid to the upper middle reach of the Congo River, from just downstream of Kisangani to the intersection where the mainstem and the Lulonga River meets. In this study, we will use PALSAR images and Envisat altimetry data to estimate surface water storage changes over the floodplains in the upper middle reaches to make comparison with the lower middle reach. We will also perform the hydraulic analysis using Envisat altimetry height profiles over the river and its adjacent floodplains to examine the source of its water. Finally, the total storage changes, estimated from GRACE regional solutions with higher temporal and spatial resolutions based on the energy conservation principle and the Hillslope River Routing (HRR) model will be investigated to highlight their differences between the upper and lower middle reaches.