Irène KINOTI soutiendra devant le jury composé de :

SUMMARY

The Stampriet Transboundary Aquifer System (STAS) is a key groundwater source shared by Namibia, Botswana, and South Africa. This PhD research aims to build on research already conducted in STAS to develop an integrated hydrological model (IHM) to better understand and manage STAS. To achieve this, the research first created a hydrogeological model to define the aquifer’s structure, flow, and properties. Since rainfall is the main driving force of the IHM? various precipitation datasets were analyzed, with the Multi-Source Weighted-Ensemble Precipitation (MSWEP) showing the best results. IHMs often rely on limited in-situ measurements of water levels and stream discharge which may lead to uncertainties. To improve accuracy, the study used satellite data from GRACE, which tracks water storage changes, alongside traditional groundwater measurements. The research found that most water in STAS is stored in the unsaturated zone where it eventually evapotraspirates. Combining GRACE data with other measurements improved the accuracy of groundwater recharge estimates.