Using hydrochemistry and environmental isotopes in the assessment of groundwater quality in the Euphrates alluvial aquifer,Syria

Hydrochemical and environmental isotope methods were used to characterize the groundwater quality in ten wells belonging to the Euphrates alluvial aquifer in Syria, with the aim to assess the origin and dynamic of groundwater salinization in this system. The Euphrates River (ER) water along its entire course in Syria is rather fresh (TDS < 0.5 g/L), and thus, it is suitable for drinking and irrigation purposes. Groundwater salinity progressively increases from north to south, changing from almost freshwater (TDS < 0.6 g/L), with a Ca–Mg and HCO₃ type near the Syrian–Turkish border to brackish water (1 < TDS < 3 g/L), with a Ca–Mg or Na–Ca–Mg and SO₄–HCO₃ type in the vicinity of Al-Raqqa, and hence it can safely be used for irrigation. Downstream Deir-Ezzor the groundwater quality becomes fairly saline to very saline (3 < TDS < 29 g/L), with a Na–Cl type, and therefore it has an absolute hazard (SAR > 5) for irrigation uses. This pattern of chemical evolution, which is also clearly reflected in the variations of groundwater ionic ratios, completely agrees with the thermodynamic simulation results obtained by an experimental evaporation essay of a water sample taken from the ER near Deir-Ezzor. Stable isotopes permit the distinction between three main evaporation processes: under high, intermediate and low humidity conditions. Radioisotopes (³H and ¹⁴C) indicate the recent age and renewability of groundwater in this aquifer and confirm that its origin is entirely belonged to the ER water, either by direct bilateral interconnection or by vertical infiltration of the irrigation water totally taken from the ER. Relationships between major ions and δ¹⁸O values of the groundwater allow to differentiate between two main enrichment processes: either evaporation only or evaporation plus dissolution, that can explain altogether the development of groundwater salinity in such a dry area.     

Hydrochemical and isotopic investigation of groundwater of Al-Batin alluvial fan aquifer,Southern Iraq

Major ions and important trace elements in addition to δ¹⁸O and δ²H were analysed for 43 groundwater samples sampled from the Al-Batin alluvial fan aquifer, South Iraq. The most dominant ions (with respect to molarity) were: Na⁺ > Cl^? > SO₄ ^2? > Ca²⁺ > Mg²⁺ > NO₃ ^? > HCO₃ ^?, with total dissolved solids (TDS) averaging 7855 mg/L. High concentrations were found for the trace elements U, Mo, V, B, Sr, and Cr. This study suggests a hydraulic connection exists near the fan apex between the uppermost part of the Al-Batin aquifer and the underlying Dammam aquifer by means of the Abu-Jir fault system. Except for the effects of extensive irrigation, fertilizer use, and poorly maintained sewers, the groundwater chemistry is mainly controlled by geological processes such as dissolution of evaporites and the enrichment of dissolved ions as a result of the high evaporation and low recharge rate. Furthermore, it is shown that the Kuwaiti fuel–oil burning during Gulf War in 1991 contributed to the enrichment of V and Mo in the studied aquifer. The spatial distribution of most ions appears to generally increase from the south-west towards the north-east, in the direction of groundwater flow. The stable isotopes show heavier values in groundwater with a gradually increasing trend in the direction of groundwater flow due to the decreasing depth to groundwater and thus increasing of evaporation from both groundwater or irrigation return water. Additionally, the stable isotope signature suggests that rainfall from sources in the Arabian Gulf and the Arabian Sea is the major source of recharge for the Al-Batin aquifer. Except for two samples of groundwater, all samples were not suitable for potable use according to the WHO standards. Most of the groundwater is suitable for some agricultural purpose and for livestock water supply. Apart from the high salinity, boron represents the most critical element in the groundwater with respect to agricultural purposes.     

Hydrochemistry of surface water and groundwater from a fractured carbonate aquifer in the Helwan area,Egypt

Groundwater is an important water resource in the Helwan area, not only for drinking and agricultural purposes, but also because several famous mineral springs have their origin in the fractured carbonate aquifer of the region. The area is heavily populated with a high density of industrial activities which may pose a risk for groundwater and surface water resources. The groundwater and surface water quality was investigated as a basis for more future investigations. The results revealed highly variable water hydrochemistry. High values of chloride, sulphate, hardness and significant mineralization were detected under the industrial and high-density urban areas. High nitrate contents in the groundwater recorded in the southern part of the study area are probably due to irrigation and sewage infiltrations from the sewage treatment station. The presence of shale and marl intercalation within the fissured and cavernous limestone aquifer promotes the exchange reactions and dissolution processes. The groundwater type is sodium, sulphate, chloride reflecting more mineralized than surface water. The results also showed that water in the study area (except the Nile water) is unsuitable for drinking purposes, but it can be used for irrigation and industrial purposes with some restrictions.     

冲洪积扇含水层地下水可开采量数值模拟——以文峪河冲洪积扇为例

依据钻孔岩性,水文地质资料,将文峪河冲洪积扇平原分为上游单一潜水区和中下游承压水区,中下游垂向划分为上部弱水含水层和下部较强承压水含水层,对上游潜水和中下游承压水用二维侧向流数学模型,对中下游弱潜水用一维垂向流数学模型,在计算了现状开采条件下的水资源基础上,进一步计算出,在扇上游集中采水时,按工业开采和农业开采,以地下水多年总补排均衡,水位长期稳定的约束条件地下水可开采量。     

Hydrochemical characteristics and seasonal variations in groundwater quality of an alluvial aquifer in parts of Central Ganga Plain,Western Uttar Pradesh,India

The present study was undertaken to assess major ion chemistry of groundwater in parts of the Central Ganga Plain and observe seasonal variations in its chemical quality. Systematic sampling was carried out during November 2005 and June 2006. The major ion chemistry of groundwater shows large variations, so much so that at times the meteoric signature seems to be completely obliterated. In many samples the concentrations of SO₄, NO₃ and F are above the permissible limit for human consumption. The graphical treatment of major ion chemistry helps in identifying four types of groundwater. All possible ionic species such as NaCl, KCl, NaHCO₃, NaSO₄, KNO₃, NaNO₃, CaHCO₃, MgHCO₃, MgSO₄ are likely to occur in groundwater system. The observed chemical variations may be attributed to sediment water interaction, ion exchange, dissolution mechanisms and anthropogenic influences such as application of fertilizers and effluents from sugar factories and paper mills. A general increase in TDS is observed in samples during June 2006. The increase in salinity is attributed to evaporation from water table, irrigation return flows, anthropogenic activities and below average rainfall in 2005 and 2006. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Modelling the vulnerability of groundwater to contamination in an unconfined alluvial aquifer in Pakistan

The area of Thal Doab is located in the Indus Basin and is underlain by a thick alluvial aquifer called the Thal Doab aquifer (TDA). The TDA is undergone intense hydrological stress owing to rapid population growth and excessive groundwater use for livestock and irrigated agricultural land uses. The potential impact of these land uses on groundwater quality was assessed using a DRASTIC model in a Geographic Information System environment. Seven DRASTIC thematic maps were developed at fixed scale and then combined into a groundwater vulnerability map. The resultant vulnerability index values were grouped into four zones as low, moderate, high and very high. The study has established that 76% of the land area that is underlain by the TDA has a high to very high vulnerability to groundwater contamination mainly because of a thin soil profile, a shallow water table and the presence of soils and sediments with high hydraulic conductivity values. In addition, only 2 and 22% of the total area lie in low and moderate vulnerability zones, respectively. The outcomes of this study can be used to improve the sustainability of the groundwater resource through proper land-use management.     

Integration of geoelectric and hydrochemical approaches for delineation of groundwater potential zones in alluvial aquifer

Geoelectric and hydrochemical approaches are employed to delineate the ground-water potential zones in District Okara, a part of Bari Doab, Punjab, Pakistan. Sixty-seven VES surveys are conducted with the Electrical Resistivity Meter. The resultant resistivity verses depth model for each site is estimated using computer-based software IX1D. Aquifer thickness maps and interpreted resistivity maps were generated from interpreted VES results. Dar-Zarrouk parameters, transverse resistance (TR), longitudinal conductance (SL) and anisotropy (λ) were also calculated from resistivity data to delineate the potential zones of aquifer. 70% of SL value is ≤3S, 30% of SL value is > 3S. According to SL and TR values, the whole area is divided into three potential zones, high, medium and low potential zones. The spatial distribution maps show that north, south and central parts of study area are marked as good potential aquifer zones. Longitudinal conductance values are further utilized to determine aquifer protective capacity of area. The whole area is characterized by moderate to good and up to some extent very good aquifer protective area on the basis of SL values. The groundwater samples from sixty-seven installed tube wells are collected for hydro-chemical analysis. The electrical conductivity values are determined. Correlation is then developed between the EC (μS/cm) of groundwater samples vs. interpreted aquifer resistivity showing R2 value 0.90.     

Hydrochemistry and quality assessment of groundwater in part of NOIDA metropolitan city,Uttar Pradesh

An attempt has been made to study the groundwater geochemistry in part of the NOIDA metropolitan city and assessing the hydrogeochemical processes controlling the water composition and its suitability for drinking and irrigation uses. The analytical results show that Na and Ca are the major cations and HCO₃ and Cl are the major anions in this water. The higher ratios of Na+K/TZ⁺ (0.2–0.7), Ca+Mg/HCO₃ (0.8–6.1); good correlation between Ca-Mg (0.75), Ca-Na (0.77), Mg-Na (0.96); low ratio of Ca+Mg/Na+K (1.6), Ca/Na (1.03), Mg/Na (0.64), HCO₃/Na (1.05) along with negative correlation of HCO₃ with Ca and Mg signify silicate weathering with limited contribution from carbonate dissolution. The hydro-geochemical study of the area reveals that many parameters are exceeding the desirable limits and quality of the potable water has deteriorated to a large extent at many sites. High concentrations of TDS, Na, Cl, SO₄, Fe, Mn, Pb and Ni indicate anthropogenic impact on groundwater quality and demand regional water quality investigation and integrated water management strategy. SAR, %Na, PI and Mg-hazard values show that water is of good to permissible quality and can be used for irrigation. However, higher salinity and boron concentration restrict its suitability for irrigation uses at many sites.     

Hydrochemistry and salt-water intrusion in the Van aquifer,east Turkey

Groundwater in the Van coastal aquifer is one of the main sources of potable, industrial and irrigational water in Van City, because of its semi-arid climate. Groundwater extraction has been in excess of replenishment owing to increased agricultural and economic activities and a growing population during the last 20 years. A hydrochemical survey of the Van aquifer provided data on the groundwater chemistry patterns and the main mineralization processes. The main processes influencing the groundwater chemistry are salinisation from salt-water intrusion, silicate mineral dissolution, cation exchange and human activity. Deterioration in water quality has resulted from intrusion of the salt water of Lake Van along the coastal regions into the Van plain. At present, the mixing rate of salt water in the Van aquifer is between 1 and 5.5% and salt water has already invaded about 5 km inland in the iskele and the airport region.     

Recharge areas and geochemical evolution of groundwater in an alluvial aquifer system in the Sultanate of Oman

A regional hydrogeochemical model was developed to evaluate the geochemical evolution of different groundwaters in an alluvial aquifer system in the Interior of Oman. In combination with environmental isotopes the model is able to extract qualitative and quantitative information about recharge, groundwater flow paths and hydraulic connections between different aquifers. The main source of water to the alluvial aquifer along the flow paths of Wadi Abyadh and Wadi Muaydin in the piedmont is groundwater from the high-altitude areas of the Jabal Akhdar and local infiltration along the wadi channels. In contrast, the piedmont alluvial aquifer along Wadi Halfayn is primarily replenished by lateral recharge from the ophiolite foothills to the east besides smaller contributions from the Jabal Akhdar and local infiltration. Further down gradient in the Southern Alluvial Plain aquifer a significant source of recharge is direct infiltration of rain and surface runoff, originating from a moisture source that approaches Oman from the south. The model shows that the main geochemical evolution of the alluvial groundwaters occurs along the flow path from the piedmont to the Southern Alluvial Plain, where dedolomitization is responsible for the observed changes in the chemical and carbon isotope composition in these waters.

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Resumen Un modelo hidrogeoquímico regional fue desarrollado, para evaluar la evolución geoquímica de diferentes aguas subterráneas en un sistema acuífero aluvial ubicado en el interior de Omán. El modelo, en combinación con isótopos ambientales, es capaz de obtener información cualitativa y cuantitativa sobre recarga, direcciones de flujo de agua subterránea y sobre las conexiones hidráulicas entre diferentes acuíferos. La fuente principal de agua para el acuífero aluvial en el piedemonte son las aguas subterráneas, a lo largo de las direcciones de flujo del Wadi Abyadh y del Wadi Muaydin, desde las áreas de gran altura de Jabal Akhdar y como infiltración local a lo largo de los canales del wadi. En contraste, el acuífero aluvial del piedemonte a lo largo del Wadi Halfayn, esta alimentado principalmente por recarga lateral desde las partes bajas de las montañas de ofiolitas hacia el Este, además por pequeñas contribuciones desde el Jabal Akhdar e infiltración local. Siguiendo gradiente abajo en el acuífero de la Llanura Aluvial del Sur, allí tanto la infiltración directa de lluvia, como la escorrentía superficial constituyen fuentes significativas de recarga, las cuales se originan en una fuente de humedad que llega a Omán proveniente del Sur. El modelo muestra, que la evolución geoquímica principal de las aguas subterráneas en el aluvión, sucede a lo largo de la dirección de flujo, que va desde el piedemonte hacia la Llanura Aluvial Sur, en donde el proceso de des-dolomitización es el responsable de los cambios observados en la composición química y también del contenido de isótopos de carbono en estas aguas.

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Résumé On a développé un modèle régional hydrogéochimique pour évaluer lévolution géochimique des différentes eaux souterraines dans le système aquifère de lintérieur dOman. Avec la contribution des isotopes denvironnement, le modèle est capable de fournir des informations qualitatives et quantitatives sur la recharge, les directions découlement et sur les connections hydrauliques entre les différents aquifères du système. La source principale pour laquifère situé au long de la direction découlement des oueds de Abdyah et de Muaydin dans le piémont est leau souterraine provenant des zones de haute altitude de Jabal Akhbar ainsi que linfiltration locale au long des canaux de loued. Par contre, à part dune petite contribution provenant des infiltrations locaux et de Jabal Akhbar, l aquifère alluvial de Wadi Halfayan est en principal alimenté par la recharge latérale provenant des ophiolites situées dans la partie est. Les plus importantes sources de recharge dans laval de laquifère de la Plaine Alluviale sont linfiltration directe et le ruissellement provenant dune source dhumidité qui sapproche dOman par le sud. Le modèle montre que la principale évolution géochimique se produise au long de la direction découlement qui part de piémont de la Plaine Alluviale du Sud, où le procès de dédolomisation est responsable pour les changements observés dans la composition géochimique et en carbone des eaux.

     

Degradation of groundwater quality in coastal aquifer of Sabratah area,NW Libya

Overextraction of groundwater is widely occurring along the coast where good quality groundwater is at risk, due to urbanization, tourist development and intensive agriculture. The Sabratah area at the northern central part of Jifarah Plain, Northwest Libya, is a typical area where the contamination of the aquifer in the form of saltwater intrusion, gypsum/anhydrite dissolution and high nitrate concentrations is very developed. Fifty groundwater samples were collected from the study area and analysed for certain parameters that indicate salinization and pollution of the aquifer. The results demonstrate high values of the parameters electrical conductivity, sodium, potassium, magnesium, chloride and sulphate which can be attributed to seawater intrusion. The intensive extraction of groundwater from the aquifer reduces freshwater outflow to the sea, creates drawdown cones and lowering of the water table to as much as 30 m below mean sea level. Irrigation with nitrogen fertilizers and domestic sewage and movement of contaminants in areas of high hydraulic gradients within the drawdown cones probably are responsible for the high nitrate concentration towards the south of the region. Seawater intrusion and deep salt water upconing result in general high SO₄ ^2? concentrations in groundwater near the shoreline, where localized SO₄ ^2? anomalies are also due to the dissolution of sebkha deposits for few wells in the nearby sebkhas. Upstream, the increase in SO₄ ^2? concentrations in the south is ascribed to the dissolution of gypsum at depth in the upper aquifer.     

Hydrochemistry and origins of mineralized waters in the Puebla aquifer system,Mexico

Significant upward movement of mineralized water takes place in the Puebla aquifer system. Preferential groundwater flow paths related to the geological structure and the lowering of the potentiometric surface are suspected to be the prime factors for this intrusion. A combined approach of geochemical and isotope analyses was used to assess the sources of salinity and processes that are controlling the changes in groundwater chemical composition in the Puebla aquifer. Geochemical and isotope data indicate that the likely source of increased solutes is mineralized water from the dissolution of evaporites of the Cretaceous age at the base of the Upper deep aquifer, which is deeper than the intakes of the shallow wells. Dedolomitization and cation exchange seems also to occur along flow paths where sulphate concentrations tend to increase. The deep regional flow paths controls the chemical stratification of groundwater in response to decreased heads through interconnecting vertical and horizontal pathways, such as in the Fosa Atlixco. The results also suggest that high sulphate concentrations originating in the Lower deep aquifer are currently affecting shallow production wells. It is concluded that hydrodynamic aspects together with hydrogeochemical characteristics need to be taken into account to correctly explain the hydrochemical evolution in the stratified aquifer.     

Use of chloride-mass balance and environmental isotopes for evaluation of groundwater recharge in the alluvial aquifer, Wadi Tharad, western Saudi Arabia

Groundwater recharge estimation has become a priority issue for humid and arid regions, especially in regions like Saudi Arabia, where the precipitation varies over space and time as a result of topography and seasonality. Wadi Tharad is a typical arid area in western Saudi Arabia. Within its drainage area of 400 km², the groundwater system shows a graded hydrochemical zonation from the hydrocarbonate in the upper reach to the chloride zone in the lower reach. The saturation index (SI) varies depending on the concentrations of carbonate minerals; the mean for calcite and dolomite is about in equilibrium (e.g., zero value). As halite and gypsum indices are negative, it is undersaturated. Isotopic compositions of H and O in the groundwater show that the groundwater recharge resources are mainly from meteoric water. The chloride-mass balance method was refined to estimate the amount of recharge, which is probably 11% of the effective annual rainfall. These results can be used to improve the accuracy of future groundwater management and development schemes.     

Hydrochemistry of groundwater in a coastal region of Cuddalore district, Tamilnadu, India: implication for quality assessment

A hydrogeochemical investigation was conducted in a coastal region of Cuddalore district to identify the influence of saltwater intrusion and suitability of groundwater for domestic and agricultural purposes. The geology of the study area comprises of sandstone, clay, alluvium, and laterite soils of Tertiary and Quaternary age. A total of 18 groundwater samples were analyzed for 14 different water quality parameters and the result indicates higher concentrations of ions like Cl (3,509 mg/l), Na (3,123 mg/l), and HCO₃ (998 mg/l) when compared with WHO, BIS, and ISI standards. A positive correlation (r ²?=?0.82) was observed between Na and Cl, indicating its sources from salt water intrusion. Three factors were extracted with a total variance of 64% which indicates the sources of salinization, cation exchange, and anthropogenic impact to the groundwater. The Piper trilinear diagram indicates both Na–Cl and mixed Na–HCO₃–Cl-type, indicating that groundwater was strongly affected by anthropogenic activities. The plot of (Ca?+?Mg)/(K?+?Na) indicates evidences of cation exchange and salt water intrusion. The (Ca–0.33*HCO₃)/ SO₄ plot indicates salt water intrusion for elevated SO₄ levels rather than gypsum dissolution. The spatial distribution of total dissolved solid indicates the saline water encroachment along the SW part of the study area. As per sodium adsorption ratio (SAR), 50% of the samples with <10 SAR are suitable for irrigation and >10 SAR indicates that water is unsuitable for irrigation purposes. The residual sodium carbonate classification indicates that 50% of the samples fall in safe and 50% of the samples fall in bad zones and prolonged usage of this water will affect the crop yield. The Chloro Alkaline Index of water indicates disequilibrium due to a higher ratio of Cl?>?Na–K, indicating the influence of salt water intrusion. The Permeability Index of the groundwater indicates that the groundwater from the study area is moderate to good for irrigation purposes.     

Renewed Geoarchaeological Investigations of Mwanganda's Village (Elephant Butchery Site), Karonga,Malawi

The site of Mwanganda's Village, located along a paleochannel in northern Malawi, is one of only a few sites that have characterized the Middle Stone Age (MSA) of Malawi for decades (Clark & Haynes, 1970 ; Clark et al., 1970 ; Kaufulu, 1990 ). The Malawi Earlier‐Middle Stone Age Project has re‐examined the site using new mapping and chronometric tools in order to reinterpret the site's significance within the context of current debates surrounding human origins and the potential role the environment played in shaping human behavior. The new data do not support the previous hypothesis that the site was an elephant butchery location (contra Clark & Haynes, 1970 ; Clark et al., 1970 ; Kaufulu, 1990 ). Instead, the evidence shows successive colonization of riparian corridors by MSA hunter‐gatherers focused on exploiting localized resources during periods of generally humid climates while other lakes desiccated across Africa. We challenge the hypothesis that stable and intermediately high lake levels within the African Rift Valley System (sensu Trauth et al., 2010 ) catalyzed the evolution of regional interaction networks between 42 and 22 ka. Instead, we interpret the evidence to suggest that regional variants of technology persist into the late MSA as foragers focused on exploiting resources from local catchments.