Abstract
Regional groundwater modelling studies in large semiarid regions are often hampered by field data scarcity, in both space and time. In such a case, remote sensing can offer complementary datasets and guide further investigations. Presented here is an example of how remote sensing and geographic information system (GIS) techniques have helped regional groundwater modelling through a better definition of groundwater recharge and discharge areas, groundwater/surface water interaction, and palaeohydrological settings. The work focuses on the Quaternary unconfined aquifer covering 500,000 km2 in the central part of the Lake Chad Basin in north-central Africa.