The hydrochemical characteristics and evolution of groundwater and surface water in the Heihe River Basin, northwest China

A combination of isotopic and chemical indicators has been used to characterize rainfall, surface water and groundwater in the Heihe River Basin, China. Surface- vs. groundwater chemistry data enabled geographical zones and chemical types to be differentiated. The dissolution of halite, Glauber’s salt, gypsum, dolomite and calcite determine Na⁺, Cl^?, Mg²⁺, Ca²⁺, $ {\text{SO}}^{{2 - }}_{4} A combination of isotopic and chemical indicators has been used to characterize rainfall, surface water and groundwater in the Heihe River Basin, China. Surface- vs. groundwater chemistry data enabled geographical zones and chemical types to be differentiated. The dissolution of halite, Glauber’s salt, gypsum, dolomite and calcite determine Na⁺, Cl⁻, Mg²⁺, Ca²⁺, and chemistry, but other processes such as evaporation, ion exchange, and deposition also influence the water composition. The majority of deep confined groundwaters are tritium-free and less mineralized than in the shallow aquifer. Radiocarbon values in the deeper groundwaters range from 18.8 to 38.9 pmc, and 80 pmc probably represents the upper limit of initial ¹⁴C activity; this yields ages of approximately 5,960–11,971 years BP, which is about 3,000 years older than those calculated by models in previous work. The shallow aquifer exhibits fairly high and variable tritium activities (4–75 TU), evidence of recent recharge and low residence time (<60 years), which is in line with estimates from previous work. Isotopic signatures indicate formation of deeper groundwaters in a colder and wetter climate during the late Pleistocene and Holocene. The results suggested that significant changes are urgently needed in water-use strategy to achieve sustainable development.

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Résumé Une combinaison de plusieurs indicateurs isotopiques et chimiques a été utilisée dans le but de caractériser les précipitations, les eaux de surface et les eaux souterraines dans le Bassin de la Rivière Heihe, en Chine. La confrontation des chimies des eaux souterraines et de surface a permis de différentier plusieurs secteurs géographiques et faciès chimiques. Les compositions chimiques en Na⁺, Cl⁻, Mg²⁺, Ca²⁺, et sont déterminées par la dissolution de la halite, du sel de Glauber, du gypse, de la dolomite et de la calcite, mais d’autres processus peuvent également avoir une influence, comme l’évaporation, les échanges de bases et la sédimentation. La majorité des eaux souterraines captives profondes ne contiennent pas de tritium, et sont moins minéralisées que dans l’aquifère superficiel. Les valeurs de carbone 14 dans l’aquifère le plus profond sont comprises entre 18.8 et 38.9 pcm, pour une valeur maximum probable d’activité initiale de 80 pcm; les ages estimés correspondants sont compris entre 5,960 et 11,971 ans, soit environ 3,000 ans de plus que ceux calculés auparavant par les modèles. L’aquifère superficiel présente des activités tritium plut?t élevées et variables (4 à 75 UT), démontrant l’existence d’une alimentation récente et d’un temps de résidence faible (<60 ans), ce qui concorde avec les études antérieures. Les signatures isotopiques indiquent une alimentation des eaux souterraines les plus profondes au cours d’épisodes climatiques plus froids et plus humides qu’actuellement, à la fin du Pléistocène et à l’Holocène. Les résultats suggèrent que des changements significatifs dans la planification des usages de l’eau sont nécessaires et urgents dans des perspectives d’exploitation durable.

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Resumen Se ha utilizado una combinación de indicadores isotópicos y químicos para caracterizar la precipitación, el agua superficial y el agua subterránea en la Cuenca del Río Heihe, China. Los datos químicos de aguas superficiales frente a las subterráneas no permiten diferenciar zonas geográficas y tipos químicos. La disolución de halita, sal de Glauber, yeso, dolomita y calcita determina la química de Na⁺, Cl⁻, Mg²⁺, Ca²⁺, y , pero otros procesos, como evaporación, intercambio de iones y precipitación influyen también en la composición del agua. La mayoría de las aguas subterráneas profundas confinadas no tienen Tritio y están menos mineralizados que el acuífero superficial. Los valores de radiocarbono en las aguas subterráneas más profundas oscilan entre 18.8 y 38.9 pmc, y el valor de 80 pmc representa probablemente el límite superior de la actividad inicial de ¹⁴C; proporcionando edades de aproximadamente 5,960–11,971 a?os BP, que son unos 3,000 a?os más antiguas de las calculadas mediante modelización en trabajos previos. El acuífero superficial tiene actividades de tritio bastante más altas y variables (4–75 UT), evidenciando una recarga reciente y unos tiempos de residencia bajos (<60 a?os), lo cual está en la línea de lo estimado en trabajos previos. Los datos isotópicos apuntan a la formación de aguas subterráneas más profundas en un clima más frío y húmedo durante el Pleistoceno superior y el Holoceno. Los resultados sugieren que se necesita hacer cambios significativos en la estrategia de uso del agua para alcanzar un desarrollo sostenible.

     

Environmental isotopic study on the recharge and residence time of groundwater in the Heihe River Basin, northwestern China

The recharge and origin of groundwater and its residence time were studied using environmental isotopic measurements in samples from the Heihe River Basin, China. δ¹⁸O and δD values of both river water and groundwater were within the same ranges as those found in the alluvial fan zone, and lay slightly above the local meteoric water line (δD=6.87δ¹⁸O+3.54). This finding indicated that mountain rivers substantially and rapidly contribute to the water resources in the southern and northern sub-basins. δ¹⁸O and δD values of groundwater in the unconfined aquifers of these sub-basins were close to each other. There was evidence of enrichment of heavy isotopes in groundwater due to evaporation. The most pronounced increase in the δ¹⁸O value occurred in agricultural areas, reflecting the admixture of irrigation return flow. Tritium results in groundwater samples from the unconfined aquifers gave evidence for ongoing recharge, with mean residence times of: less than 36 years in the alluvial fan zone; about 12–16 years in agricultural areas; and about 26 years in the Ejina oasis. In contrast, groundwater in the confined aquifers had ¹⁴C ages between 0 and 10 ka BP.     

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.     

Hydrochemical tracers in the middle Rio Grande Basin,USA: 1. Conceptualization of groundwater flow

Chemical and isotopic data for groundwater from throughout the Middle Rio Grande Basin, central New Mexico, USA, were used to identify and map groundwater flow from 12 sources of water to the basin, evaluate radiocarbon ages, and refine the conceptual model of the Santa Fe Group aquifer system.Hydrochemical zones, representing groundwater flow over thousands to tens of thousands of years, can be traced over large distances through the primarily siliciclastic aquifer system. The locations of the hydrochemical zones mostly reflect the modern predevelopment hydraulic-head distribution, but are inconsistent with a trough in predevelopment water levels in the west-central part of the basin, indicating that this trough is a transient rather than a long-term feature of the aquifer system. Radiocarbon ages adjusted for geochemical reactions, mixing, and evapotranspiration/dilution processes in the aquifer system were nearly identical to the unadjusted radiocarbon ages, and ranged from modern to more than 30 ka. Age gradients from piezometer nests ranged from 0.1 to 2 year cm^–1 and indicate a recharge rate of about 3 cm year^–1 for recharge along the eastern mountain front and infiltration from the Rio Grande near Albuquerque. There has been appreciably less recharge along the eastern mountain front north and south of Albuquerque.

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Resumen Se utilizaron datos químicos e isotópicos de agua subterránea a lo largo de la cuenca central del río Grande, Nuevo México, EEUU, para identificar y mapear el flujo de agua subterránea de 12 fuentes de agua a la cuenca para evaluar edades por medio de radio carbon y para refinar el modelo conceptual del sistema acuífero del Grupo Santa Fé. Se puede establecer zonas hidrotérmicas que representan el flujo de agua subterránea a lo largo de miles a miles de decenas de años en grandes distancias a través del sistema acuífero principalmente siliclástico. Las ubicaciones de las zonas hidroquímicas mayormente reflejan la distribucion de la cabeza hidráulica pre-desarollo moderna pero son inconsistentes con una depresión en los niveles de agua pre-desarollo en la zona central oeste de la cuenca. Esto indica que esta depresión es un rasgo transitorio y no un rasgo de largo plazo del sistema acuífero. Las edades de radio carbon ajustadas para los procesos de reaciones geoquímicas, de mezclado y de evapotranspiración-dilución son casi idénticas a los edades de radio carbon no ajustadas oscilan en un rango desde la modernidad a 30 mil años. Las gradientes de edad de nidos de piezometros van de 0.1 a 2 años cm^–1 e indican un sitio de recarga de aproximadamente 3 cm/yr para la recarga a lo largo del frente montañoso oriental e infiltración del río Grande cerca de Albuquerque. Se aprecia una recarga menor a lo largo del frente oriental de montañas al norte y al sur de Albuquerque.

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Résumé Des données sur les éléments chimiques et les isotopes présents dans leau souterraine prélevée à divers endroits dans le bassin moyen du Rio Grande, au centre du Nouveau-Mexique (É-U), ont permis de déterminer lexistence et létendue de douze sources deau régionales dans le bassin, dévaluer les âges radiocarbones et de raffiner le modèle conceptuel du système aquifère du groupe de Santa Fe. Des zones hydro-chimiques qui représentent lécoulement de leau souterraine depuis des dizaines de milliers dannées peuvent être suivies sur de longues distances à travers laquifère principalement siliclastique. La position des zones hydro-chimiques reflète principalement la distribution moderne des charges hydrauliques mais est incohérente avec une dépression dans le niveau deau dans la partie centre-ouest du bassin, ce qui indique que cette dépression est un élément transitoire du système aquifère plutôt quun élément à long terme. Les âges radiocarbones ajustés aux réactions géochimiques et aux processus de mélange et dévapotranspiration/dilution qui ont lieu dans laquifère sont presque identiques aux âges non ajustés et varient de la période moderne jusquà 30 ka. Les gradients dâge établis à partir des nids de piézomètres sétendent de 0.1 à 2 a cm^–1 et suggèrent un taux de recharge denviron 3 cm a^–1 le long du front des montagnes à lest et pour linfiltration provenant du Rio Grande près dAlbuquerque. Il y a eu substantiellement moins de recharge le long du front des montagnes à lest, au nord et au sud dAlbuquerque.

     

Environmental isotopic and hydrochemical study of groundwater in the Ejina Basin,northwest China

The study investigates the groundwater evolution and its residence time in the Ejina Basin, northwest China according to isotope and hydrochemical analyses results. The groundwater chemistry is mainly controlled by the dissolution of halite, Glauber’s salt, gypsum, dolomite and calcite, also influenced by other processes such as evaporation, ion exchange, and deposition. Based on tritium content in atmospheric precipitation and by adopting a model with exponential time distribution function, the mean residence time of the unconfined aquifer groundwater with fairly high tritium activities (21–49 TU) is evaluated. The results show that these groundwaters have low residence time (5–120 years) and are renewable. In contrast, the deep confined groundwaters are tritium-free and radiocarbon values range from 18.3 to 26.7 pmc. According to the most commonly used ¹⁴C correction models, the radiocarbon groundwater ages were calculated which yield ages of approximately 4,087–9,364 years BP. Isotopic signatures indicate formation of deep confined groundwaters in a colder and wetter climate during the late Pleistocene and Holocene. It is suggested that long-term, rational water usage guide should be set up for the Heihe River Basin as a whole to permit a considerable discharge to the Ejina Basin.     

Application of environmental groundwater tracers at the Sulphur Bank Mercury Mine, California, USA

Boron, chloride, sulfate, δD, δ¹⁸O, and ³H concentrations in surface water and groundwater samples from the Sulphur Bank Mercury Mine (SBMM), California, USA were used to examine geochemical processes and provide constraints on evaporation and groundwater flow. SBMM is an abandoned sulfur and mercury mine with an underlying hydrothermal system, adjacent to Clear Lake, California. Results for non-³H tracers (i.e., boron, chloride, sulfate, δD, and δ¹⁸O) identify contributions from six water types at SBMM. Processes including evaporation, mixing, hydrothermal water input and possible isotopic exchange with hydrothermal gases are also discerned. Tritium data indicate that hydrothermal waters and other deep groundwaters are likely pre-bomb (before ~1952) in age while most other waters were recharged after ~1990. A boron-based steady-state reservoir model of the Herman Impoundment pit lake indicates that 71–79% of its input is from meteoric water with the remainder from hydrothermal contributions. Results for groundwater samples from six shallow wells over a 6–month period for δD and δ¹⁸O suggests that water from Herman Impoundment is diluted another 3% to more than 40% by infiltrating meteoric water, as it leaves the site. Results for this investigation show that environmental tracers are an effective tool to understand the SBMM hydrogeologic regime.

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Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.

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Résumé Les concentrations en bore, chlorure, sulfate, δD, δ¹⁸O, et ³H d’échantillons d’eaux de surface et souterraine prélevés dans le banc de soufre de la mine de mercure (SBMM en anglais) en Californie, USA, ont été utilisées pour étudier les processus géochimiques et pour fournir des contraintes à l’évaporation et à l’écoulement des eaux souterraines. La SBMM est une mine de soufre et de mercure abandonnée, adjacente au lac Clear en Californie et sous laquelle se trouve un système hydrothermal.Les résultats des traceurs autres que le tritium (bore, chlorure, sulfate, δD, et δ¹⁸O) ont permis d’identifier des contributions de six types d’eaux à SBMM. Des processus tels que l’évaporation, le mélange, l’entrée d’eau hydrothermale et de possibles échanges isotopiques avec des gaz hydrothermaux ont également été identifiés. Les données de tritium montrent que les eaux hydrothermales et d’autres eaux profondes sont probablement d’age antérieure à la bombe (avant ~1952), alors que la plupart des autres eaux sont issues de la recharge après ~1990. Un modèle de réservoir représentant le lac situé dans la partie Herman Impoundment de l’ancienne mine, en régime permanent et basé sur le bore, montre que 71–79% de l’eau provient des précipitations, le reste provenant de contributions hydrothermales. Les résultats de δD et δ¹⁸O pour des échantillons d’eau souterraine de six puits peu profonds sur une période de 6 mois suggèrent que l’eau de Hermann Impoundment est encore diluée entre 3% jusqu’à plus de 40% lorsqu’elle quitte le site du fait de l’infiltration d’eau météorique. Les résultats de cette étude montrent que les traceurs environnementaux constituent un outil efficace pour comprendre le régime hydrogéologique de la SBMM.

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Resumen Se han utilizado datos de concentraciones de boro, cloruros, sulfatos, δD, δ¹⁸O, y ³H en muestras de aguas superficiales y subterráneas procedentes de la Mina de Mercurio Sulphur Bank (SBMM), California, USA, para estudiar los procesos geoquímicos y caracterizar la evaporación y el flujo del agua subterránea. SBMM es una mina abandonada de azufre y mercurio con un sistema hidrotermal subyacente, cercano al Lago Clear, California.Los resultados de los trazadores que no son ³H (por ejemplo, boro, cloruros, sulfatos δD, y δ¹⁸O) identifican las contribuciones de seis tipos de agua en la SBMM. Se han identificado diversos procesos, como evaporación, mezcla, entrada de agua hidrotermal y la posibilidad de intercambios isotópicos con gases hidrotermales. Los datos de tritio indican que las aguas hidrotermales y otras aguas subterráneas profundas son probablemente pre-bombas (previas a ~1952) en edad mientras que la mayoría de las otras aguas se han recargado después de ~1990. Un modelo estacionario basado en el boro de la fosa del lago Herman Impoundment indica que el 71–79% de su entrada procede de agua meteórica con restos de contribución hidrotermal. Los resultados para las muestras de aguas subterráneas procedentes de seis pozos superficiales en un periodo de 6 meses para δD y δ¹⁸O sugieren que el agua procedente de Herman Impoundment se diluye en otro 3% hasta más del 40% debido a la infiltración de agua meteórica., que sale del sitio. Los resultados de esta investigación muestran que los trazadores ambientales son una herramienta efectiva para entender el régimen hidrogeológico de la SBMM.

     

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.

     

Spatial characteristics of water quality,stable isotopes and tritium associated with groundwater flow in the Hutuo River alluvial fan plain of the North China Plain

The groundwater flow system and the flow velocity in the alluvial fan plain of the Hutuo River, China, have been studied, with an emphasis on relating geochemical characteristics and isotopes factors. Seven stretches of one river, six springs and 31 wells, with depths ranging from 0 m (river waters) to 150 m, were surveyed. The groundwater has a vertical two-layer structure with a boundary at about 80–100 m depth, yielding an upper and a lower groundwater layer. The δ¹⁸O and δD values range from ?10.56 to ?7.05‰ and ?81.83 to ?59‰, respectively. The groundwater has been recharged by precipitation, and has not been subjected to significant evaporation during infiltration into the aquifer in the upper layer. Using a tritium model, the groundwater flow in the alluvial fan plain showed horizontal flow velocity to be greater than vertical velocity. Groundwater in the upper layer is characterized by Ca–HCO₃ type. From the spatial distribution characteristics of the stable isotope and chemical composition of the groundwater, agricultural irrigation was considered to have an influence on the aquifer by causing excessive groundwater abstraction and irrigation return.     

Hydrogeochemistry and isotope analyses used to determine groundwater recharge and flow in low-gradient catchments of the province of Buenos Aires,Argentina

The region known as Pampa Plain, in Argentina, is a vast area characterized by slopes of less than 0.05%. The surface sediment is silty sand, mainly Aeolian, referred to as Pampean Loess, which is a phreatic aquifer unit of utmost importance for the water supply of the region. On account of the slight gradient, hydrogeological analyses using only hydraulic measurements are difficult to perform, often leading to confusing results. Thus, the study presented relies on hydrochemical modeling and isotopic determinations as well. The study area comprises three catchments in the inter-mountainous area corresponding to El Moro, Tamangueyú and Seco creeks, and covering 2,570 km² in the province of Buenos Aires. Measurements of piezometric levels and samples of groundwater, surface water and rainwater were carried out between January and March 2005. Major ion results were analyzed by means of hydrochemical graphs and hydrogeochemical modelling using NETPATH. The resulting data show that it is possible to identify local changes in recharge, flow direction and stream/groundwater relationship by using hydrochemical and isotopic information, which may become a useful and more precise tool for the study of particularly flat landscapes.     

Hydrochemistry and isotope compositions of groundwater from the Shihongtan sandstone-hosted uranium deposit, Xinjiang, NW China

Groundwaters and surface water in the Shihongtan sandstone-hosted U ore district, Xinjiang, NW China, were sampled and analyzed for their major-, and trace element concentrations and oxygen, hydrogen, boron and strontium isotope compositions in order to assess the possible origins of the waters and water–rock interactions that occurred in the deep aquifer system. The waters in the study district have been grouped into three hydrochemical facies: Facies 1, potable spring-water, is a pH neutral (7.0), Na–Ca–HCO₃ type water with low total dissolved solids (TDS; 0.2 g/l, fresh) and has δ¹⁸O of − 8.3‰, δD of − 48.2‰,δ¹¹B of 1.5‰, and ⁸⁷Sr/⁸⁶Sr of 0.70627. Facies 2 groundwaters are mildly acidic to mildly alkaline (pH of 6.5–8.0, mean 7.3), Na–Ca–Mg–Cl–SO₄ type waters with moderate TDS (8.2 g/l–17.2 g/l, mean 9.3 g/l, brackish) and haveδ¹⁸O values in the − 5.8‰ to − 9.3‰ range (mean − 8.1‰), δD values in the − 20.8‰ to − 85.5‰ range (mean − 47.0‰),δ¹¹B values in the + 9.5‰ to + 39.1‰ range (mean + 17.1‰), and ⁸⁷Sr/⁸⁶Sr values in the 0.70595 to 0.70975 range (mean 0.70826). Facies 3, Aiting Lake water, is a mildly alkaline (pH = 7.4), Na–Ca–Mg–Cl–SO₄ type water with the highest TDS (249.1 g/l, brine) and has δ¹⁸O of − 2.8‰, δD of − 45.8‰,δ¹¹B of 21.2‰, and ⁸⁷Sr/⁸⁶Sr of 0.70840. The waters from the study district show a systematic increase in major, trace element and TDS concentrations and δ¹¹B values along the pathway of groundwater migration which can only be interpreted in terms of water–rock interaction at depth and strong surface evaporation. The hydrochemical and isotopic data presented here confirm that the groundwaters in the Shihongtan ore district are the combined result of migration, water–rock interaction and mixing of meteoric water with connate waters contained in sediments.     

Use of multiple age tracers to estimate groundwater residence times and long-term recharge rates in arid southern Oman

Multiple age tracers were measured to estimate groundwater residence times in the regional aquifer system underlying southwestern Oman. This area, known as the Najd, is one of the most arid areas in the world and is planned to be the main agricultural center of the Sultanate of Oman in the near future. The three isotopic age tracers ⁴He, ¹⁴C and ³⁶Cl were measured in waters collected from wells along a line that extended roughly from the Dhofar Mountains near the Arabian Sea northward 400 km into the Empty Quarter of the Arabian Peninsula. The wells sampled were mostly open to the Umm Er Radhuma confined aquifer, although, some were completed in the mostly unconfined Rus aquifer. The combined results from the three tracers indicate the age of the confined groundwater is < 40 ka in the recharge area in the Dhofar Mountains, > 100 ka in the central section north of the mountains, and up to and > one Ma in the Empty Quarter. The ¹⁴C data were used to help calibrate the ⁴He and ³⁶Cl data. Mixing models suggest that long open boreholes north of the mountains compromise ¹⁴C-only interpretations there, in contrast to ⁴He and ³⁶Cl calculations that are less sensitive to borehole mixing. Thus, only the latter two tracers from these more distant wells were considered reliable. In addition to the age tracers, δ²H and δ¹⁸O data suggest that seasonal monsoon and infrequent tropical cyclones are both substantial contributors to the recharge. The study highlights the advantages of using multiple chemical and isotopic data when estimating groundwater travel times and recharge rates, and differentiating recharge mechanisms.     

Movement of water through the thick unsaturated zone underlying Oro Grande and Sheep Creek Washes in the western Mojave Desert,USA

Previous studies indicate that a small quantity of recharge occurs from infiltration of streamflow in intermittent streams in the upper Mojave River basin, in the western Mojave Desert, near Victorville, California. Chloride, tritium, and stable isotope data collected in the unsaturated zone between 1994 and 1998 from boreholes drilled in Oro Grande and Sheep Creek Washes indicate that infiltration of streamflow occurs to depths below the root zone, and presumably to the water table, along much of Oro Grande Wash and near the mountain front along Sheep Creek Wash. Differences in infiltration at sites along each wash are the result of hydrologic variables such as proximity to the mountain front, quantity of streamflow, and texture of the subsurface deposits. Differences in infiltration between the washes are the result of large-scale geomorphic processes. For example, Oro Grande wash is incised into the Victorville fan and infiltration has occurred at approximately the same location over recent geologic time. In contrast, Sheep Creek Wash overlies an active alluvial fan and the stream channel can move across the fan surface through time. Infiltration does not occur to depths below the root zone at control sites outside of the washes. Electronic Publication     

Recharge mechanism and hydrochemistry evaluation of groundwater in the Nuaimeh area, Jordan, using environmental isotope techniques

The relationship between the stable isotopic and chemical composition of precipitation and groundwater was studied in the Nuaimeh area of the Ajloun Highlands in Jordan. The isotopic composition values of precipitation and groundwater are almost identical. The spatial variation of stable isotopes in precipitation is mainly due to the effect of seasonal temperature, altitude and amount. The groundwater reveals identical variation in isotopic composition to the precipitation due to direct recharge and the karstic nature of the outcropping Turonian aquifer. Tritium levels in wells are high and their content is similar to the weighted mean value of tritium content in precipitation, indicating local recharge and low residence time. The ¹⁴C activity in the tritiated groundwater is found to be about half of the ¹⁴C activity of precipitation in the region. A geochemical evolution through dissolution of carbonate by water–carbonate rock interactions reduced the atmospheric ¹⁴C activity from 114 to 61 pmc in the groundwater. A ¹⁴C of around 61 pmc and 7.6 TU values are considered the initial concentration for the recharge in the shallow carbonate aquifer in the Yarmouk Basin. The large fluctuation of water level in observation wells during the rainy season indicates the sensitivity and direct response of the aquifer to the recharge. The chemical composition of the groundwater (Ca²⁺–HCO₃^–) gives emphasis to the short duration of water–rock interaction and indicates dissolution of the carbonate aquifer. The elevated concentrations of Cl^– and NO₃^– in groundwater are attributed to anthropogenic sources.

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Resumen Fue estudiada la relación entre la composición isotópica estable y la composición química, tanto de la precipitación como del agua subterránea, en el área de Nuaimeh en las montañas de Ajloun, en Jordania. Los valores de la composición isotópica de la precipitación y del agua subterránea son casi idénticos. La variación espacial de los isótopos estables en la precipitación, es debida principalmente al efecto de la temperatura estacional, a la altura y a la cantidad. El agua subterránea muestra una variación idéntica a la precipitación en cuanto a la composición isotópica, debido a la recarga directa y a la naturaleza cársica del acuífero Turoniano aflorante. Los niveles de tritio en los pozos son altos y su contenido es similar al valor medio ponderado del contenido de tritio en la precipitación, indicando una recarga local y un tiempo de residencia corto. Se ha encontrado que la actividad de ¹⁴C en el agua subterránea tritiada, es alrededor de la mitad de la actividad del ¹⁴C en la precipitación para la región. La evolución geoquímica ocurrida a partir de la disolución del carbonato, por las interacciones roca carbonatada–agua, redujeron la actividad atmosférica del ¹⁴C desde 114 en porcentaje de carbono moderno (pcm) hasta 61 pcm en el agua subterránea. Los valores del ¹⁴C cercanos a 61 pcm y de 7.6 unidades de tritio, se han considerado como las concentraciones originales para la recarga en el acuífero carbonatado somero de la Cuenca de Yarmouk. Una gran fluctuación en el nivel de agua de los pozos de observación, durante la estación lluviosa, indica la sensibilidad y la respuesta directa del acuífero frente a la recarga. La composición química del agua subterránea (Ca²⁺–HCO₃^–), enfatiza en la corta duración de la interacción de agua–roca, e indica disolución del acuífero carbonatado. La concentración elevada de Cl^– y NO₃^– en el agua subterránea, se atribuye a fuentes antropogénicas.

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Résumé Dans la région montagneuse dAjloun de Jordanie on a étudié la relation entre la composition chimique et isotopique des précipitations et des eaux souterraines. La composition isotopique est presque identique dans précipitations et les eaux souterraines. La variation spatiale de la teneur en isotopes stables dans les précipitations est déterminée en principal par les variations saisonnière de la température, laltitude ainsi que par la quantité des précipitations. A cause de la recharge directe et de la nature karstique des affleurements de laquifère dage touronienne, les eaux souterraines présentent la même composition isotopique que les précipitations. La teneur en ³H mesurée dans les forages présente des valeurs élevées, proches de la valeur moyenne des précipitations, ce quindique une recharge locale et un temps court de résidence. On a déterminé pour lactivité de ¹⁴C une valeur proche de la moitié trouvée dans les précipitations. Lévolution géochimique par dissolution des carbonates pendant linteraction entre leau et les roche a diminué lactivité du ¹⁴C, de la valeur de 114 pcm en atmosphère à 61 pcm dans les eaux souterraines. Dans laquifère calcaire de surface de bassin Yarmouk, on a considéré comme de concentrations initiales, les valeurs de 61 pcm pour ¹⁴C et 7.2 UT pour ³H. Les grandes fluctuations des niveaux des eaux souterraines observées dans les forages pendant les saisons pluvieux montrent la sensibilité ainsi que la réponse directe de laquifère au recharge. La composition chimique des eaux souterraines (Ca²⁺–HCO₃^–) montre de plus le temps court de linteraction entre leau et la roche, en indiquant aussi la dissolution de laquifère calcaire. Les taux élevées de la concentration en Cl^– et NO₃^– dans les eaux souterraines ont été attribuées aux sources humaines.

     

Characterization of surface water and groundwater in the Damascus Ghotta basin: hydrochemical and environmental isotopes approaches

The hydrochemistry of major ions and environmental isotope compositions (¹⁸O, ²H and tritium) of water samples have been used to investigate the characteristics of rainfalls, surface water and groundwater in the Damascus Ghotta basin. The groundwater salinity in the Damascus Ghotta basin gradually increases, as the groundwater moves from western to south-eastern and north-eastern parts of the basin. A strong relationship exists between the Barada river and the surrounded groundwaters, mainly in terms of recharge by infiltration of surface waters. The groundwater quality in the Adra region has clearly become less saline as a result of establishment of the sewage-water-treatment station in this area since 1997. The uncommon depleted stable isotope concentrations in the vicinity of Al-Ateibeh Lake and Adra valley could be interpreted as a result of sub-flow recharge from the Cenomanian–Turonian aquifer, mostly prolonged along the Damascus Fault, which forms direct contact between this complex and the Quaternary alluvium aquifers. The extensive exploitation of water from the Cenomanian–Turonian aquifer for drinking water supply would shortly be reflected by a gradual decline of the groundwater table in the Damascus Ghotta basin. Amelioration of water quality in the Damascus basin still requires further management strategies and efforts to be taken within the forthcoming years.     

Salinization of groundwater in the Nefzawa oases region,Tunisia: results of a regional-scale hydrogeologic approach

Groundwater pumped from the semi-confined Complexe Terminal (CT) aquifer is an important production factor in irrigated oases agriculture in southern Tunisia. A rise in the groundwater salinity has been observed as a consequence of increasing abstraction from the aquifer during the last few decades. All sources of contamination were investigated using hydrochemical data available from the 1980s. Water samples were taken from drains and observation wells tapping both the CT and the phreatic aquifers and analyzed with regard to chemistry, temperature, isotopes and other environmental tracers. Local salinization mechanisms are suggested, i.e. the upwelling of saline water from the underlying, confined Continental Intercalaire (CI) aquifer, as well as backflow of agricultural drainage water. At this stage, the main salt pan, the Chott el Djerid, is not a contamination source. A finite difference model was also developed to simulate groundwater flow and contaminant transport in the oases. Calibration for the period 1950–2000 was carried out in order to adjust geological and chemical system parameters. The simulation of planned extraction projects predicts a worsening of the present situation. Maintenance of the present abstraction regime will not reduce or stop the salinity increase.

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Résumé L’eau souterraine pompée dans l’aquifère semi-captif du Complexe Terminal (CT) est un facteur de production important pour l’agriculture des oasis irriguées du sud de la Tunisie. Une augmentation de la salinité de l’eau souterraine a été considérée comme la conséquence de l’augmentation des prélèvements dans l’aquifère au cours des dernières décades. Toutes les sources de contamination ont été étudiées à l’aide de données hydro-chimiques disponibles depuis les années 80. Des échantillons d’eau ont été prélevés dans des drains et des puits d’observation qui captent à la fois le CT et les aquifères phréatiques; la chimie, la température, les isotopes ainsi que d’autres traceurs environnementaux ont été analysés. Des processus locaux de salinisation sont proposés, comme par exemple la remontée d’eau salée en provenance de l’aquifère captif du Continental Intercalaire (CI) sous-jacent, ainsi que le reflux des eaux du drainage agricole. A ce stade, le principal marais salé, le Chott el Djerid, n’est pas une source de contamination. Un modèle aux différences finies a également été élaboré pour simuler les écoulements souterrains et le transport de contaminants dans les oasis. Une calibration pour la période 1950–2000 a été effectuée afin d’ajuster les paramètres des systèmes géologique et chimique. La simulation de projets planifiés d’extraction prédit une aggravation de la situation actuelle. La conservation du régime d’extraction actuel ne réduira ou ne stoppera pas l’augmentation de la salinité.

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Resumen El agua subterránea que se bombea del acuífero semi-confinado Terminal Complejo (CT) es un importante factor de producción en la agricultura de riego con oasis en el sur de Túnez. Se ha observado un incremento en la salinidad del agua subterránea como consecuencia de la abstracción creciente del acuífero durante las últimas décadas. Se investigaron todas las fuentes de contaminación usando datos hidroquímicos disponibles de la década de 1980s. Las muestras de agua se tomaron de drenajes y pozos de observación alojados tanto en el CT como los acuíferos freáticos y se analizaron en relación con química, temperatura, isótopos y otros trazadores ambientales. Se sugieren mecanismos de salinización local, i.e. el ascenso de agua salada a partir del acuífero confinado subyacente Intercalado Continental (CI), así como también retorno de flujo de agua de drenaje agrícola. En esta etapa, el pan salado principal, el Chott el Djerid, no es una fuente de contaminación. También se desarrolló un modelo de diferencia finita para simular el flujo de agua subterránea y el transporte de contaminantes en los oasis. Se calibró el modelo para el periodo 1950–2000 para de este modo ajustar parámetros del sistema químico y geológico. La simulación de los proyectos de extracción que se han planeado predice un empeoramiento de la situación actual. El mantenimiento del régimen de extracción actual no reducirá o detendrá el incremento de salinidad.

     

Hydrochemistry and isotope geochemistry as tools for groundwater hydrodynamic investigation in multilayer aquifers: a case study from Lomellina, Po plain, South-Western Lombardy, Italy

A multicriteria approach in studying hydrodynamics of a multilayer aquifer system has been used in the Lomellina region (Northern Italy). It involves the reconstruction of the hydrogeological framework coupled to the definition of the hydrochemical and isotopic features of the aquifers. A shallow phreatic aquifer, reaching depths of about 60–80 m from the surface, and deeper aquifers containing confined groundwater, were distinguished. Groundwater generally shows mineralisation decreasing with depth; dissolved ions depict calcium-bicarbonate hydrochemical facies and stable isotopes define the recharge mechanisms, the origin of groundwater, and the hydraulic confinement of deep aquifers. The phreatic aquifer is fed by local infiltration and by streams and irrigation channels. Tritium and Carbon-14 groundwater dating indicate long residence times (on the order of thousands of years) for confined aquifers. The confined aquifers show essentially passive hydrodynamic conditions and maintain a higher piezometric level than the phreatic aquifer. This inhibits the possibility of recent water penetrating far below the surface. The hydrogeological setting of the Lomellina region displays features which are common to other sectors of the Po plain. As a consequence, the results of this study, although conducted on a restricted area, are highly illustrative of groundwater hydrodynamics in large sedimentary aquifers.     

Application of hydrochemical signatures to delineating portable groundwater resources in Ordos Basin, China

The Ordos Basin of China encompasses Shaanxi, Gansu, and Shanxi provinces, Ningxia and Inner Mongolia autonomous regions. It lacks significant surface water resources. Among the water-bearing formations, the Luohe formation, with an area of 1.32×10⁵ km², is the most prospective aquifer. Groundwater quality data collected at 211 boreholes drilled into the Luhe formation indicate a complex distribution of groundwater chemistry. The hydrochemical properties were used to study the recharge, runoff, and discharge conditions of the groundwater in Ordos Basin and to evaluate sustainable groundwater resources. In the northern part of the basin, the hydrochemistry types and the total dissolved solids (TDS) show a clear lateral transition from SEE to NWW, indicating that the groundwater gets recharge in the northwest region and discharges in the southeast region. In the southern part of the basin, maximum TDS occurs at the center of the Malian River valley, from which the TDS decreases radially. Therefore, the groundwater in the southern basin gets recharge from the southeast and southwest regions, and the Malian River valley is the discharge zone. As a result of this research, the areas with portable groundwater were delineated. They include most of the southeast region of the Sishili Ridge, east of the Ziwu Mountain, and the southwest corner of the basin. The TDS of the groundwater in these regions is less than 1 g/l, and the hydrochemistry type is either HCO₃ or HCO₃·SO₄.     

Groundwater recharge in a sedimentary basin in semi-arid Mexico

Recharge mechanisms and the hydrochemical evolution of groundwater in a semi-arid, 6,840-km², intermountain basin in central Mexico were investigated using stable isotopes and major chemical constituents. Ionic ratio analysis helped to conceptualize and quantify in part the subsequent geochemical evolution in the aquifer system. Mass balance models (PHREEQC) were used to interpret and rectify the geochemical properties of the aquifer. The recharge conditions have not changed noticeably during the last several thousands of years. The recharge mechanisms are accompanied by leaching of meteoric salts on and near the ground surface during major rain events, which previously accumulated after minor rain events. Rapid and diffuse infiltration can be excluded. Indirect infiltration from wadis (arroyos) and depressions (playas) with little mixing in shallow groundwater contrasts with a high degree of mixing for water with deep circulation. The prevailing source of major cations (Ca²⁺, Mg²⁺, Na⁺, K⁺) is weathering of carbonates and albite, followed by exchange reactions on clays and hydroxides. Ca²⁺/Na⁺ exchange may interchange along the flow path with reverse (Na⁺/Ca²⁺) exchange, although the Ca²⁺/Na⁺ option is prevalent. Meteoric Ca and Mg inputs are relatively small; however, meteoric Na is insignificant. Irrigation return flow plays an important role in the western part of the study area, giving rise to elevated sulfate and chloride concentrations.

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Resumen Se han investigado los mecanismos de recarga y la evolución hidroquímica de las aguas subterráneas en una cuenca semiárida e intermontanosa de México central, de 6.840 km². Para ello, se han utilizado isótopos estables y los constituyentes químicos mayores. El análisis de las relaciones iónicas ha servido para conceptuar y cuantificar en parte su evolución geoquímica posterior dentro del sistema acuífero. Se ha recurrido a modelos de balance de masas (PHREEQC) para interpretar y rectificar las propiedades geoquímicas del acuífero. Las condiciones de recarga no han cambiado de forma apreciable durante los últimos miles de años. Los mecanismos de recarga se ven acompañados por el lixiviado de las sales meteóricas sobre y cerca de la superficie del terreno durante los episodios principales de lluvia, las cuales son acumuladas en episodios menores de lluvia. Se puede excluir la infiltración rápida y difusa. La infiltración indirecta desde arroyos ( wadis) y depresiones ( playas), que apenas se mezcla con las aguas subterráneas someras, contrasta con un elevado nivel de mezcla con el agua de circulación profunda. La fuente dominante de cationes mayores (calcio, magnesio, sodio, potasio) es la meteorización de los carbonatos y albita, mientras que las reacciones de intercambio en las arcillas e hidróxidos son menos importantes. El intercambio ión calcio-ión sodio puede ser reemplazado a lo largo de una línea de flujo por el intercambio opuesto (ión sodio-ión calcio), aunque la primera es prioritaria. Las aportaciones meteóricas de calcio y magnesio son relativamente pequeñas, mientras que la de sodio es insignificante. Los retornos de riego desempeñan un papel importante en la parte occidental del área de estudio, dando lugar a concentraciones elevadas de sulfato y cloruro.

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Résumé Les mécanismes de recharge et lévolution hydrochimique de leau souterraine dans un bassin de montagne de 6 840 km² en zone semi-aride, dans le centre du Mexique, ont été étudiés au moyen des isotopes stables et des composés chimiques majeurs. Lanalyse des rapports ioniques a aidé à conceptualiser et à quantifier en partie lévolution géochimique qui en résulte, dans le système aquifère. Des modèles de bilan de masse (PHREEQC) ont été utilisés pour interpréter et corriger les propriétés de laquifère. Les conditions de recharge nont pas changé notablement au cours des derniers millénaires. Les mécanismes de recharge sont accompagnés, durant les épisodes majeurs de précipitation, dun lessivage, à la surface du sol et à son voisinage, de sels météoriques accumulés auparavant pendant les petits épisodes de pluie. Linfiltration rapide et diffuse peut être exclue. Linfiltration indirecte à partir des oueds (arroyos) et des dépressions (playas) avec un faible mélange dans la nappe superficielle contraste avec le degré élevé de mélange de leau avec les circulations profondes. La source prépondérante des cations majeurs (Ca²⁺, Mg²⁺, Na⁺, K⁺) est laltération des carbonates et des feldspaths ; léchange de cations avec les argiles et les hydroxydes est moins important. Léchange de Ca²⁺ avec Na⁺ peut sinverser le long des axes découlements pour donner un échange de Na⁺ avec Ca²⁺, bien que le cas Ca²⁺/Na⁺ soit prépondérant. Les apports météoriques de Ca et de Mg sont relativement faibles, cependant que celui de Na météorique est insignifiant. Lécoulement par retour dirrigation joue un rôle important dans la partie occidentale de la région étudiée, produisant un accroissement des concentrations élevées en sulfate et en chlorure.

     

Groundwater replenishment analysis by using natural isotopes in Ejina Basin, Northwestern China

The Ejina Basin underlying complex aquifers is located in the lower reaches of the Heihe River with an arid climate and 40 mm mean annual precipitation. As the balance of the natural ecosystem in the Ejina Basin is fragile and easily upset, it is very important to estimate and rationally use the limited groundwater resources to maintain the balance. Water samples were collected from the Heihe River and wells for chemical and isotopic measurements across the basin. The Piper diagram gives two main types of hydrochemical features. Against the background of the regional geology, combining isotope ¹⁸O, tritium, and chemical analysis with groundwater flows indicated by a shallow groundwater level contour map, different kinds of groundwater sources and ways to replenish groundwater were discovered. North of the study area are artesian wells that are replenished by the mountainous area at the boundary between China and Mongolia. Replenishment for most of the groundwater resources of the Gurinai oasis comes from the Heihe River seepage flow of the highly conductive paleochannel, not from the Badain Jaran Desert as indicated by TDS and tritium analysis. The different groundwater ages which are younger than 35 years were approximately estimated by radioactive isotope tritium (T). By such efforts, groundwater resources can be effectively evaluated with the engineering impact of the Heihe River Project.     

Pumping decisions for sustainable development of groundwater resources in areas of grassland degradation: a case study in Lanqi Banner, Inner Mongolia, China

The best planting alternatives for satisfying high water use demands of forage and fodder crops in a region of Inner Mongolia, China, were determined by a multiobjective distributed-parameter groundwater management model. These alternatives took account of different cropping patterns and pumping decisions associated with both temporal and spatial aspects of water allocation. The model was developed for phreatic, homogenous, and isotropic aquifers using the response matrix technique of quadratic programming theory and, in this case, using the alternative direction implicit (ADI) scheme. Model solutions using effective rainfall with a probability of 50%, show that average water table drawdown in the planning period (2006–2017) is 0.22 m and the groundwater fluctuation in each pumping well is very low. In order to evaluate the pumping decisions under an effective rainfall with a probability of 75%, a sensitive analysis was also conducted. Analysis shows that it is useful to apply the results from the proposed model to control the landscape degradation due to overgrazing and overpumping activities.