Hydrochemical constraints between the karst Tabular Middle Atlas Causses and the Sais basin (Morocco): implications of groundwater circulation
Las limitaciones hidroquímicas entre el karst Tabular Middle Atlas Causses y la cuenca Saïs (Marruecos): implicancias en la circulación del agua subterránea
Contraintes hydrochimiques entre les Causses karstiques du Moyen atlas tabulaire et le bassin de Saïs (Maroc): implications de la circulation des eaux souterraines
Restrições hidroquímicas entre o carste dos Causses Tabulares do Atlas Médio e a Bacia do Saïs (Marrocos): implicações da circulação das águas subterrâneas
Résumé
The karst Tabular Middle Atlas Causses reservoir is the main drinking-water supply of Fez-Meknes region (Sais Basin) in Morocco. Recent analyses showed a decline in associated groundwater chemical quality and increased turbidity. To understand this hydrosystem, four surveys were undertaken during fall and spring, 2009-2011. Hydrogeochemical studies coupled with isotopic analyses (δ 18 O, δD and 222 Rn) showed that the aquifers between the causses (mountains) and the Saïs Basin are of Liassic origin and at the southern extremities are of Triassic origin. Five recharge zones of different altitudes have been defined, including two main mixing zones in the south. Deuterium excess results suggest local recharge, while a plot of δ 18 O versus δD characterizes a confined aquifer in the eastern sector. 222 Rn results reveal areas of rapid exchanges with an upwelling time of less than 2 weeks. A schematic conceptual model is presented to explain the groundwater circulation system and the behavior of this karst system.
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