Geophysical constraints on the groundwater circulation and its renewal at the main Bittit spring, supplying Meknes and its region (Sais Basin): Characterization & conceptual model.

Gineth Saracco (1) , Mohamed Rouai (2) , Konstantinos Chalikakis (3, 4, 5) , Abdelilah Dekayir (2) , Helene Miche (1) , Adriano Mayer (3) , Khaoula Qarqori (2) , Brahim Abderahim (2) , Christophe Emblanch (6, 3)

1 CEREGE - Centre européen de recherche et d'enseignement des géosciences de l'environnement
2 UMI - جامعة مولاي إسماعيل = Université Moulay Ismaïl
3 EMMAH - Environnement Méditerranéen et Modélisation des Agro-Hydrosystèmes
4 AU - Avignon Université
5 SNO Karst - Service National d'Observation sur le KARST
6 LHA - Laboratoire d'Hydrogéologie d'Avignon

Previous hydrochemical and isotopic studies of the tabular Middle-Atlas karst showed that the Sais basin is mainly fed at its northern border by the carbonated Causses of the fractured Lias, in particular by El Hajeb causse to the east and the Guigo causse west (Miche et al, 2018). In a context of over-exploitation of the water karst system accentuated by the current climatic variations, with recurrent droughts and sparse strong thunderstorms, the karstic spring of Bittit, main water source of Meknes and its region, is strongly solicited. Since we have obtained a conceptual model using hydrochemical and isotopic data, Bittit is mainly involved by the causse of El Hajeb (1500m) and partially by the causse of Imouzzer (1340m). It is necessary to localize the depth of mixing zones and the direction of preferential flows around Bittit spring, for a better understanding of aquifers renewal. The coupling of electromagnetic sounding (EM34) and electrical resistivity tomography (ERT) show a tightening of conductivity zones according to the SE-NW direction. It means preferential flows at depth quasi-perpendicularly to the causses, contrary to what was supposed. This was confirmed by depth estimates of potential sources (drainage area in the porous structure) by using electrical multi-scale wavelet tomography of spontaneous potential (SP) around Bittit. A global conceptual model based on hydrochemical, isotopic and geophysical data is proposed.

Mots clés: Electromagnetic Mapping; Electrical Resistivity Tomography ERT; Electrical conductivity; Spontaneous Potential; Multi-Scale Wavelet Tomography; Conceptual model

Domaines: Interfaces continentales, environnement; Géophysique [physics.geo-ph]; Hydrologie; Sciences du Vivant [q-bio]

Gineth Saracco, Mohamed Rouai, Konstantinos Chalikakis, Abdelilah Dekayir, Helene Miche, et al.. Geophysical constraints on the groundwater circulation and its renewal at the main Bittit spring, supplying Meknes and its region (Sais Basin): Characterization & conceptual model.. 2nd Annual Meeting MedGU, Nov 2022, Marrakech, Morocco. pp.1-6. ⟨hal-03831266⟩