Investigating the Role of the Cuvette Centrale in the Hydrology of the Congo River Basin

The increasing pressure on wetland resources continues to threaten the role wetlands play in maintaining the ecological balance of watersheds. The Cuvette Centrale of the Congo is the greatest intertropical peatland in the world. To fully understand its role in water resources and ecological services linked to the quality of water and life in the basin, we first need to quantify its role in the hydrological dynamics. To achieve this aim, we used the Soil and Water Assessment Tool model (SWAT) – modified for tropical environments – in combination with monthly discharge data. We analyzed water fluxes entering and flowing out of the Cuvette Centrale of the Congo River Basin on a monthly time scale for the 2000–2012 period. The model was calibrated, validated, and compared with discharge from gauging stations and surface water elevation from radar altimetry. Results showed that upland runoff from the Congo River was the highest contributor to the Cuvette Centrale (33%) followed closely by efficient precipitation inside the Cuvette Centrale (31%) with right bank and left bank tributaries contributing 25 and 11%, respectively. We simulated monthly mean interannual inflows of approximately 34,150 m 3 /s (88 billion m 3 ) with the main flood peaking in November (45,310 m 3 /s) and total outflows averaging around 39,860 m 3 /s (100 billion m 3 ) peaking at 52,430 m 3 /s in December for the simulation period. We subsequently estimated a negative monthly mean interannual variation of storage in the Cuvette Centrale wetlands in the order of 5,700 m 3 /s, suggesting that the Cuvette Centrale supplies the river during low water periods. This highlights the important regulatory function of the Cuvette Centrale and the need for protection of groundwater resources in order to maintain wetland water quantities and quality.