Dazu wurden mehr als 1.000 Proben aus Grundwasser, Oberflächenwasser und Niederschlag auf Hydrochemie und umweltstabile Isotope analysiert. Anhand von Wasserchemie, Umwelt- ( 18O, 2H, 3H) und Kohlenstoff- ( 14C) Isotopen können Neubildungsprozesse bewertet und das Grundwasseralter grob abgeschätzt werden. Neubildungsquellen für den oberen Quartären Grundwasserleiter sind Niederschläge, Flüsse und Feuchtgebiete. Da die Wasserversorgung der Landbevölkerung und des größten Teils der Stadtbevölkerung vom Grundwasser abhängt, ist die Einschätzung der Grundwasserneubildung von entscheidender Bedeutung. Groundwater ages of 600–4,150 years, estimated from 14C analyses combined with high SO 4 concentrations, along the Bahr el Ghazal indicate that recharge was caused by residuals of the Mega Lake before it dried out completely.ĭas Tschadseebecken ist Afrikas größtes endorheisches Einzugsgebiet. Recharge is caused by surface water that undergoes evaporative processes before percolation. Groundwater along the Lake Chad shore and the Bahr el Ghazal corridor show high δ-values (δ 18O –0.78 to 7.45‰, δ 2H –13.6 to 30.8‰). Slightly high δ-values in water occur in the Waza Logone area between Chad and Cameroon. Focused recharge from fresh river water is typical for Salamat Region in south Chad and the Komadugu Yobe wetlands between Nigeria and Niger. The environmental isotope distribution shows recent recharge from precipitation north of Lake Chad (Kanem Region), where very low 3H values indicate occurrence before the 1960s bomb peak. Furthermore, 3H measurements and 14C values of dissolved inorganic carbon for groundwater from the northeastern part of the Basin are included in the evaluation. For this purpose, more than 1,000 samples from groundwater, surface water and precipitation were analysed for hydrochemistry and environmental stable isotopes. Using water chemistry, and environmental ( 18O, 2H, 3H) and carbon ( 14C) isotopes, recharge processes can be assessed and groundwater ages roughly estimated. Recharge sources for the upper Quaternary aquifer are precipitation, rivers, and swamps. Because water supply for the rural population and most of the urban population depends on groundwater, assessment of groundwater recharge is crucial. The Lake Chad Basin is Africa’s largest endorheic basin.
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