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

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.Le bassin hydrologique du Barada et de l’Awaj est le plus important et le plus intensément exploité de Syrie. Le sous bassin amont de la rivière Awaj occupe la partie sud-ouest de ce bassin. Dans cette région aride, l’eau souterraine représente la principale réserve et ressource de production d’eau. Dans l’optique de caractériser le fonctionnement du système hydrogéologique multicouche local et de calculer un bilan hydrologique pour l’aquifère superficiel, une méthodologie multi techniques couplant hydrochimie, isotopie et hydrodynamisme a été déployée. L’analyse détaillée des données hydrochimiques recueillies a mis en évidence la grande variabilité du fond géochimique local, directement fonction de la stratigraphie. Cette complexité stratigraphique induit une vision hydrogéologique complexe de nombreux corps aquifères. L’évolution de la chimie des eaux révèle la prépondérance du phénomène de dissolution/précipitation des roches carbonatées comme principal mécanisme de contrôle de l’hydrochimie, devant l’hydrolyse des silicates, la dissolution du gypse et l’échange ionique. En conséquence il n’a pas été possible de déduire de l’hydrochimie des eaux les preuves d’une recharge par drainance ascendante depuis l’aquifère du jurassique vers les aquifères superficiels, bien que la similarité des faciès hydrochimiques tend à consolider l’hypothèse d’une origine unique des eaux, sans toutefois permettre une identification des chemins d’écoulement. Les données isotopiques indiquent quant à elles, une infiltration importante et rapide des eaux météoritiques, avant qu’une importante phase d’évaporation n’ait lieu. Ainsi, l’important flux d’infiltration qui se produit essentiellement dans la partie montagneuse de la zone, représente la principale source de recharge du système aquifère multicouche régional. De ce fait la zone d’étude peut se subdiviser en deux sous régions : la première (A) se caractérise par une dissolution active et des flux de circulation d’eau souterraine fortement orientés verticalement vers la profondeur, alors que la seconde (B) est caractérisée par des écoulements peu profonds associés à des interactions hydrochimiques avec les roches encaissantes. Les résultats de la modélisation hydrodynamique du système mettent en évidence la connexion hydraulique entre l’aquifère profond du Jurassique et les aquifères surincombants par le biais d’une drainance ascendante. Le bilan hydrologique de l’aquifère se surface a ainsi pu être appréhendé : les principaux flux de recharge proviennent de l’infiltration des eaux météoritiques mais également de l’écoulement latéral du Jurassique dans la partie montagneuse. La drainance ascendante depuis le Jurassique dans la partie aval est également non négligeable. Du point de vue des sorties, le flux d’écoulement le plus important se situe en direction de l’est vers le centre du bassin. Ce constat permet de concevoir que La sous bassin amont de le rivière Awaj est la principale zone de recharge occidentale du bassin de Barada et Awaj

Groundwater Modeling as an Alternative Approach to Limited Data in the Northeastern Part of Mt. Hermon (Syria), to Develop a Preliminary Water Budget

In developing countries such as Syria, the lack of hydrological data affects groundwater resource assessment. Groundwater models provide the means to fill the gaps in the available data in order to improve the understanding of groundwater systems. The study area can be considered as the main recharge area of the eastern side of Barada and Awaj basin in the eastern part of Mt. Hermon. The withdrawal for agricultural and domestic purposes removes a considerable amount of water. The steady-state three-dimensional (3D) groundwater model (FEFLOW which is an advanced finite element groundwater flow and transport modeling tool), was used to quantify groundwater budget components by using all available data of hydrological year 2009–2010. The results obtained may be considered as an essential tool for groundwater management options in the study area. The calibrated model demonstrates a good agreement between the observed and simulated hydraulic head. The result of the sensitivity analysis shows that the model is highly sensitive to hydraulic conductivity changes and sensitive to a lesser extent to water recharge amount. Regarding the upper aquifer horizon, the water budget under steady-state condition indicates that the lateral groundwater inflow from the Jurassic aquifer into this horizon is the most important recharge component. The major discharge component from this aquifer horizon occurs at its eastern boundary toward the outside of the model domain. The model was able to produce a satisfying estimation of the preliminary water budget of the upper aquifer horizon which indicates a positive imbalance of 4.6 Mm3·y−1

Integrative Approach for Groundwater Pollution Risk Assessment Coupling Hydrogeological, Physicochemical and Socioeconomic Conditions in Southwest of the Damascus Basin

Groundwater is the main resource for irrigation and drinking supply in most parts of Syria, as for most Mediterranean countries, however this resource suffers from mismanagement. In the study area (northeast of Mt. Hermon), the lack of information makes water management in this area extremely difficult. Assessing groundwater pollution risk is the most essential issue for water resources management, especially in the regions where complex interaction between climate, geology, geomorphology, hydrogeology, water scarcity and water resource mismanagement exist. This complexity leads to significant complication in determining pollution risk of studied system. In the present work, we adopted an integrative approach to assess groundwater pollution risk in the study area. This methodology is based on the analysis of hydrogeological characteristics of aquifer systems and the available information about socioeconomic context and physiochemical groundwater conditions that might affect this system. This approach allowed us to delineate the groundwater pollution risk map based on the analysis of concerning parameters/indicators. The degree of risk was assessed as the sum and average of rating of these parameters and indicators for each subarea. Typically, very high pollution risk index was identified over the Quaternary/Neogene horizon, i.e., shallow and unconfined aquifer and in the lower part of Jurassic aquifer. In these two parts, the majority of anthropogenic activities are concentrated. Low pollution risk index was found for the outcropping of low permeable Quaternary basalt at the Southern part of the study area. A moderate pollution index was identified for the low/moderate permeability of silt, clay and marly limestone-rich horizons of the major part of Neogene aquifer outside of the intersected zones with Quaternary aquifer and for the Paleogene formations. The spatial analysis shows that about 50% of the study area is characterized as being at very high and high pollution risk index. Hence, the overall natural protective capacity of this area is still poor. This study demonstrates the flexibility of the proposed approach to assess groundwater pollution risk in local complex aquifer system characterized by lack of information and data in order to reduce the risk of future groundwater pollution

Hydrochemistry, isotopes and groundwater modeling to characterize multi-layered aquifers flow system in the upper part of Awaj River - Damascus Basin (Syria)

Le bassin hydrologique du Barada et de l’Awaj est le plus important et le plus intensément exploité de Syrie. Le sous bassin amont de la rivière Awaj occupe la partie sud-ouest de ce bassin. Dans cette région aride, l’eau souterraine représente la principale réserve et ressource de production d’eau. Dans l’optique de caractériser le fonctionnement du système hydrogéologique multicouche local et de calculer un bilan hydrologique pour l’aquifère superficiel, une méthodologie multi techniques couplant hydrochimie, isotopie et hydrodynamisme a été déployée. L’analyse détaillée des données hydrochimiques recueillies a mis en évidence la grande variabilité du fond géochimique local, directement fonction de la stratigraphie. Cette complexité stratigraphique induit une vision hydrogéologique complexe de nombreux corps aquifères. L’évolution de la chimie des eaux révèle la prépondérance du phénomène de dissolution/précipitation des roches carbonatées comme principal mécanisme de contrôle de l’hydrochimie, devant l’hydrolyse des silicates, la dissolution du gypse et l’échange ionique. En conséquence il n’a pas été possible de déduire de l’hydrochimie des eaux les preuves d’une recharge par drainance ascendante depuis l’aquifère du jurassique vers les aquifères superficiels, bien que la similarité des faciès hydrochimiques tend à consolider l’hypothèse d’une origine unique des eaux, sans toutefois permettre une identification des chemins d’écoulement. Les données isotopiques indiquent quant à elles, une infiltration importante et rapide des eaux météoritiques, avant qu’une importante phase d’évaporation n’ait lieu. Ainsi, l’important flux d’infiltration qui se produit essentiellement dans la partie montagneuse de la zone, représente la principale source de recharge du système aquifère multicouche régional. De ce fait la zone d’étude peut se subdiviser en deux sous régions : la première (A) se caractérise par une dissolution active et des flux de circulation d’eau souterraine fortement orientés verticalement vers la profondeur, alors que la seconde (B) est caractérisée par des écoulements peu profonds associés à des interactions hydrochimiques avec les roches encaissantes. Les résultats de la modélisation hydrodynamique du système mettent en évidence la connexion hydraulique entre l’aquifère profond du Jurassique et les aquifères surincombants par le biais d’une drainance ascendante. Le bilan hydrologique de l’aquifère se surface a ainsi pu être appréhendé : les principaux flux de recharge proviennent de l’infiltration des eaux météoritiques mais également de l’écoulement latéral du Jurassique dans la partie montagneuse. La drainance ascendante depuis le Jurassique dans la partie aval est également non négligeable. Du point de vue des sorties, le flux d’écoulement le plus important se situe en direction de l’est vers le centre du bassin. Ce constat permet de concevoir que La sous bassin amont de le rivière Awaj est la principale zone de recharge occidentale du bassin de Barada et Awaj.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

Hydro-Geochemical Characteristics of the Shallow Alluvial Aquifer and Its Potential Artificial Recharge to Sustain the Low Flow of the Garonne River

The complex and interconnected water challenges linked to global climate change and natural and anthropogenic water resources pressure have become major challenges in the 21st century. The Garonne River and its accompanying alluvial aquifers are considered the most important source for agricultural activities in the Garonne Valley, Nouvelle-Aquitaine Region, southwest France. The water is used for irrigation in summer and to reduce frost damage in spring. The alluvial shallow aquifer is recharged by rainfall, lateral inflow from the hillside, and seepage from the riverbed during the flood periods. The aquifer maintains the flow of the river during dry periods. Moreover, the potential recharge of this aquifer is particularly sensitive to annual climatic fluctuations and consequently affects surrounding ecosystems and related socio-economic activities. The increasing impacts of climate change have increased the concern about the availability of these resources. Various adaptation strategies have been considered to mitigate and adapt to the new situation in southwest France. The artificial recharge of the alluvial aquifer is one such regional adaptation strategy to adapt to climate change. The study has two main objectives: to assess the natural and anthropogenic influence on the groundwater chemistry, and to model water infiltration, and understand the aquifer response and, consequently, the effects on river baseflow. The TAG (Technopole Agen-Garonne) project aims to increase the economic wealth of the region while respecting the region’s agricultural traditions. Runoff water from the TAG zone is collected in retention basins and is a potential source to recharge the shallow alluvial aquifer. Sampling campaigns were carried out during the summer of 2019 to collect groundwater samples from several observation wells. Groundwater levels were measured in 132 wells/boreholes to determine the groundwater level fluctuations and create piezometric maps. Piper, spatial distribution, and ionic ratio plots were used to determine the dominant hydrochemical processes and to delineate the hydrochemical facies in the study area. The groundwater chemistry is controlled by silicate weathering and anthropogenic influence. Groundwater quality appears to be affected by the river water in the wells located in the low plain area. The measurements showed that the groundwater levels in the wells located near the river increase more than 2 m after a flood event. The artificial recharge has increased the groundwater level by more than 1 m close to the infiltration basin after a rainstorm. Similarly, a three-dimensional (3D) groundwater model shows a similar magnitude aquifer response to the induced infiltration. The modeling-obtained result shows that the infiltrated water would take about 4 months to reach the Garonne River, which is an appropriate time to maintain the river’s low-flow and thermal buffering capacity, and thus the functioning of its ecosystems during dry periods

Groundwater Modeling as an Alternative Approach to Limited Data in the Northeastern Part of Mt. Hermon (Syria), to Develop a Preliminary Water Budget

International audienc

Integrative Approach for Groundwater Pollution Risk Assessment Coupling Hydrogeological, Physicochemical and Socioeconomic Conditions in Southwest of the Damascus Basin

Groundwater is the main resource for irrigation and drinking supply in most parts of Syria, as for most Mediterranean countries, however this resource suffers from mismanagement. In the study area (northeast of Mt. Hermon), the lack of information makes water management in this area extremely difficult. Assessing groundwater pollution risk is the most essential issue for water resources management, especially in the regions where complex interaction between climate, geology, geomorphology, hydrogeology, water scarcity and water resource mismanagement exist. This complexity leads to significant complication in determining pollution risk of studied system. In the present work, we adopted an integrative approach to assess groundwater pollution risk in the study area. This methodology is based on the analysis of hydrogeological characteristics of aquifer systems and the available information about socioeconomic context and physiochemical groundwater conditions that might affect this system. This approach allowed us to delineate the groundwater pollution risk map based on the analysis of concerning parameters/indicators. The degree of risk was assessed as the sum and average of rating of these parameters and indicators for each subarea. Typically, very high pollution risk index was identified over the Quaternary/Neogene horizon, i.e., shallow and unconfined aquifer and in the lower part of Jurassic aquifer. In these two parts, the majority of anthropogenic activities are concentrated. Low pollution risk index was found for the outcropping of low permeable Quaternary basalt at the Southern part of the study area. A moderate pollution index was identified for the low/moderate permeability of silt, clay and marly limestone-rich horizons of the major part of Neogene aquifer outside of the intersected zones with Quaternary aquifer and for the Paleogene formations. The spatial analysis shows that about 50% of the study area is characterized as being at very high and high pollution risk index. Hence, the overall natural protective capacity of this area is still poor. This study demonstrates the flexibility of the proposed approach to assess groundwater pollution risk in local complex aquifer system characterized by lack of information and data in order to reduce the risk of future groundwater pollution

Origin and recharge mechanisms of groundwater in the upper part of the Awaj River (Syria) based on hydrochemistry and environmental isotope techniques

International audienc