Application of remote sensing and GIS for groundwater modelling of large semiarid areas: example of the Lake Chad Basin, Africa

Because of its large extent and the extremes of its climatic and environmental conditions, the Lake Chad Basin is an example of a region where it is extremely difficult to collect hydro(geo)logical field observations. So far, the scale and the scope to which remote sensing and GIS can assist groundwater modelling in such regions has not been fully exploited. We detail applications of remote sensing and GIS to improve groundwater modelling of the large superficial Quaternary aquifer, which covers 500 000 km2 and forms the main water resource of the basin. Satellite imagery and GIS enabled us to refine the location of recharge and discharge areas. In a GIS framework, relevant maps and pertinent satellite images were analysed together with hydrogeological data. The rationale was to search and map key characteristics in the terrain that indicate groundwater discharge and recharge areas. In addition, maps and low cost satellite data, such as AVHRR and Meteosat, were used for a thorough mapping of the fluctuations of Lake Chad extent over the last three decades. Using GIS, this valuable information was implemented in a transient groundwater model, with the MODFLOW program. The model calibration was greatly improved by the use of remote sensing data