Nsimi forest catchment (Cameroon)

Natural chemical tracers revealed how groundwater, the rainforest swamp and the stream interact in the Nsimi tropical watershed. The study showed that groundwater circulation strongly controls water and solute transfers, while chemical weathering of the crystalline basement contributes substantially to dissolved-element export.

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Location: Nyong river basin, Cameroon

Elevation: 670 - 700 masl

Geology: Crystalline rock basement (granite)

Aquifer type: fractured crystalline-rock aquifer

Scientific question: "Is it the wetland or the aquiferthat stores the water in tropical head catchment?"

Nsimi is part of M-TROPICS Observatory and OZCAR research infrastructure

Location map

Key Findings

Groundwater is a major component of the hydrological functioning of the tropical watershed, linking the weathered basement, wetlands and stream network.
Natural chemical tracers reveal contrasting groundwater flow paths and allow the contribution of different hydrological compartments to the headwater stream to be identified.
The rainforest headwater swamp acts as an important hydrological regulator, controlling the transfer of water from the groundwater system toward the stream.
Chemical weathering is a major control on dissolved-element fluxes from the tropical crystalline-rock watershed, linking groundwater circulation, weathering and stream chemistry. The work also quantified elemental weathering fluxes and saprolite production rates.
The weathering profile is therefore not simply a passive geological layer: it is an active component of the hydrological and geochemical functioning of the watershed.