Remote sensing for runoff predetermination in Sahel

Abstract

Rainfall-runoff modelling is basically used to simulate the response of gauged calibrated catchments. However, the problem usually is to predict an output discharge without prior calibration hence from the catchment physical and geomorphologic characteristics. Because remote sensing is essentially limited to the assessment of the ground surface characteristics, it appears particularly suited to sahelian catchments for which stormflow is generally accepted to be controlled by the soil toplayer. This paper presents the potential contribution of remote sensing to predetermine the discharge at the outlet of small sahelian catchments on an event basis. Results from a distributed approach that aims to upscale runoff from local remotely-sensed «infiltration excesså are discussed, and possible extensions are proposed. Finally, it is suggested that a complementary global statistical approach tending to downscale relevant hydrologic parameters derived from remote sensing could be very valuable from an operational point of view.