Hydrochimie, isotopie et modélisation hydrodynamique pour la caractérisation du système aquifère multicouche amont de la rivière Awaj - Bassin de Damas (Syrie)

摘要

Barada and Awaj basin is the most important and extensively used water basin in Syria. The upper part of Awaj River occupies the southwestern part of this basin. In this arid region, groundwater is considered to be as a main source of water supply. In order to assess the main features which characterize the hydrogeological system in this area and calculate the water budget of the first aquifer horizon, a multi approach methodology using hydrochemistry, environmental stable isotopes and groundwater modeling were used as integrated tools. The detailed description of hydrogeochemical conditions has underlined the very complex variability of the stratigraphic sequences and hence the numerous hydrogeological units within the study area. Hydrogeochemical evolution reveals the domination of dissolution/precipitation of carbonate rocks as a main mechanism controlling groundwater chemical composition and to less extend, the silicate hydrolysis, dissolution of gypsum and reverse ion exchange. Consequently, hydrochemical patterns did not give enough evidences for the expecting of huge feeding flow from the Jurassic aquifers towards the Neogene/Quaternary aquifer. The similarity in water type tends to express the existence of a unique hydrochemical system where the individualised groundwater flow paths are difficult to delineate. The isotope compositions imply an important rapid infiltration of atmospheric precipitation before significant evaporation takes place. Hence the infiltrated precipitation provides the main source of groundwater recharge all over the study area and mainly throughout the mountainous parts. The study area can be dividing into two main sub-regions. The sub-region (A) which characterizes by active dissolution phenomena and deep vertical groundwater flow. And sub-region (B) which characterizes by a shallow horizontal flow component associated with active interaction between groundwater and hosting rocks. The result of groundwater model indicates a hydraulic connection between the deep aquifers and the overlying first aquifer through the upward leakage of groundwater. The components of the water budget of the first aquifer had determined. The lateral discharge from the Jurassic aquifer as well as the meteoric recharge is the most important recharging component of this budget. The upward leakage of groundwater from deeper aquifers also plays an important role. However, the lateral discharge from the eastern boundary is the largest discharge component which indicates that the study area can be considered as a main recharge region of the western side of the Barada and Awaj Basin.