Understanding the way water storage space-time distribution controls and/or responds to water fluxes (precipitation, evapotranspiration, streamflow...) is a fundamental step to reveal critical zone processes, that is, the way each compartment in the critical zone is linked with the others.
Streamflow generation in Sudanian West-Africa
By combining a whole range of different hydro (precipitation, streamflow, water table depths, soil moisture), geophysical (ERT, EM38) and hybrid gravity measurements, we could reveal streamflow (here mostly baseflow) generation processes at a headwater catchment scale in Sudanian West-Africa (Northern Benin) from observation of the internal catchment dynamics (i.e. spatial distribution of water storage changes).
Evapotranspiration of different land covers in West-Africa:
Comparing temporal dynamics and amplitudes of evapotranspiration fluxes from Savannah and forested land cover in Sudanian area, as measured by Eddy-correlation from flux-tower data brings significant insights into how would the large land-use change impact water storage and the water cycle (fluxes). In many parts of West-Africa, anthropic pressure (past, present, and expected in the future due to the strong demographic rates) increases replacement wood cover by savannah and plots.
The hydrological role of inland valleys in Sudanian West-Africa
Inland valleys are small headwater wetlands in Subsaharan Africa. In the Sudanian basement area, they provide a large part of the river flow. They are mostly composed by a low permeability layer at a few meter depth below the valley thalweg which collects subsurface lateral flow and provide the seasonal baseflow to the downstream section. They seem to play an important ecological role due to their wetland caracteristics (maintaining moisture during the dry season), but also due to their impact on downstream streamflow. They carry an important agronomic potential, as counter season cultivation is possible. However, little is known about the fundamental functioning of such systems, which hinders the development of studies regarding to their development sustainability. Based on a highly studied inland valley in the AMMA-CATCH observing system, we could model the complete critical zone system of a small inland valley, and matching many observations (water storage changes, water table, soil moisture, evapotranspiration, streamflow). Then virtual experiments have been undertaken to show that the system was highly sensitive to its vegetation cover, and how pedological features specific to inland valley affected the water budgets and dynamics.
Groundwater recharge below sahelian rivers
[story to come]