Impact of environmental isotopes in the fissured aquifer study in Mali

Interpretation of environmental isotopes in fissured au Mali has led to an improvement of the general knowledge obtained through classical hydrogeology and piezometric measurements. Tritium concentrations has proved the occurrence of important renewable water resources in the western and southern fissured aquifers of the country, even in the Sahelian zone. For this aquifer's type however, the recharge rate mainly depends on the lithology, the granulometry and the thickness of the superficial layers. Stable isotope contents and C-14 activities have confirmed the general present origin of most of the water bodies. However, some fossil water, recharged during the last humid Holocene period, has been demonstrated in precambrian sedimentary formations. The spatial distribution of isotope contents does not show any regional trends. It demonstrates the main importance of local circulation and evaporation in the natural water balance. (author). 16 refs, 8 figs, 5 tabs