Hydrodynamic assessment of the Sangha Basin – sensitivity of flows to changes in climate and land use

The Congo River Basin ranks second in the world after the Amazon, both from its discharge and drainage area.  The Congo basin is known as the “lung of the earth” due to its capacity of absorbing more carbon than the Amazon. Its rivers provide huge benefit to the societies and the ecosystems in Central Africa (Alsdorf et al., 2016). In particular, the hydrodynamic processes between the different major drainage units of the Congo basin as well as the impacts of global change on its evolution are still poorly documented.

The Sangha River is one of the main tributaries of the Congo basin, which remains poorly understood. It is long of 720 km and drains a watershed of 220,000 Km2 at its outlet in the Republic of Congo. It is shared between three countries: Cameroon, the Central African Republic and the Republic of Congo; and is home to the “Sangha Trinational“, which is a natural World Heritage, thus justifying the importance of the conservation of its ecosystem.

The hydrodynamics of the Sangha is complex and less studied, which hinders our understanding of how this hydrosystem could respond to future impacts of environmental change. This basin has already shown signs of variation in its hydrological regimes, with a significant decrease observed between 1970 and 1975.  Previous studies have also highlighted a negative trend in the streamflow of the Congo River main stem linked to hydrological variability in the Sangha (Laraque et al., 1998, 2012). This observation requires further knowledge of their origins and their consequences on other tributaries of the Congo Basin. 

This PhD thesis project aims to establish a detailed assessment of the parameters and conditions that govern hydrological behaviour in the Sangha basin, while estimating the potential impacts of climate change and changes in land surface conditions on the hydrological regime. The main scientific questions on which this study is based are: 

• What are the main causes of hydrological fluctuations in the Sangha Basin?
• How do climate variations and changes in surface conditions affect the hydrological dynamics of the Sangha Basin?
• How would the flows of the Sangha evolve under certain climatic and environmental scenarios?

This research work will require an integrated approach to watershed analysis and will combine modern hydroclimatic analysis methods and tools:

• A large bibliographic database will be necessary to better define the contours of this research project;
• Intense work on hydrometric instrumentation and field measurements will be carried out for the collection of hydrological data; 
• The methods of hydrological data analysis will combine statistics, spatial analyses using GIS;
• Hydrological simulations will be carried out to assess the sensitivity of rivers to different climatic and environmental scenarios. 
• Close collaboration is envisaged with other CBSI observatories to facilitate data sharing, including: the Basin Climate Observatory, the Vegetation Observatory and the Congo Basin Land Use and Land Use Observatory.