Application of Meteosat thermal data to map soil infiltrability in the central part of the Lake Chad basin, Africa.

Abstract

1] In the central part of the Lake Chad Basin, Africa, the superficial Quaternary aquifer (500,000 km 2 ) forms the main water resource. Little is known about the aquifer recharge processes. Large piezometric depressions affect the aquifer and are still unexplained. Meteosat thermal composite data were used to infer qualitative information about time-space variations of soil moisture. Over the aquifer, Meteosat data reveal that after heavy rainfall, the piezometric depressions (Kadzell, Chari-Baguirmi) appear cooler than the surrounding areas (Manga and Harr). The interpretation is that above the depressions, rainwater accumulates at the surface and does not infiltrate deep into the ground, leading to the observed cooler ground. Accordingly, the depressions are characterized by low rainwater infiltrability, which presumably results in a small rainfall recharge. As far as we know, this is the first time that an observed surface phenomenon is directly related to the origin of some piezometric depressions.

Application of AVHRR imagery and GRACE measurements for calculation of actual evapotranspiration over the Quaternary aquifer (Lake Chad basin) and validation of groundwater models

“…The higher clay content in soils (UNESCO-PNUD-CBLT, 1972) supports the idea that this region is less favourable for recharge than the surrounding dunes of Manga. Similar conclusions were made for the Kadzell and the Chari-Baguirmi regions by Leblanc et al (2003) after studying T max values of METEOSAT images.…”

Apport de la géologie, de l’hydrogéologie et des isotopes de l’environnement à la connaissance des «nappes en creux» du Grand Yaéré (Nord Cameroun)

“…ARCHAMbAULT (1960ARCHAMbAULT ( , 1987 définit les « nappes en creux » comme des anomalies hydrogéologiques majeures, très répandues en Afrique subsaharienne semi-aride, se traduisant par des courbes piézométriques fermées et concentriques, des creux très accentués pouvant atteindre plusieurs dizaines de mètres au-dessous du niveau normal de la nappe. Les connaissances sur ces types de nappe se sont enrichies de nombreux travaux dont DEGALLIER (1962), DEPAGnE (1967, DIEnG et al (1990), nGOUnOU nGATCHA (1993), ARAnYOSSY et nDIAYE (1993), FAVREAU et al (2002, LEbLAnC et al (2003), GAULTIER (2004).…”

Hydrological Evaluation of Lake Chad Basin Using Space Borne and Hydrological Model Observations

“…They used satellite images from Landsat and Moderate Resolution Imaging Spectrometer (MODIS) for their studies. Thermal remote sensing techniques, such as the Meteosat thermal maximum composite data, was used to account for the variability of inundated areas within the lake under flooded vegetation [17]. Satellite imagery and GRACE data were used to study the regional hydrogeology and made an attempt at estimating the actual evapotranspiration over the LCB [5].…”