Recharge and salinization in the Madrid Basin

The purpose of this work was to reinvestigate the existing hydrogeological conceptual model of the basin of Madrid, Spain. A cumulative chemical isotopic diagram which enabled the distinction between different groups of water as well as calculation of the mode of their blending was used for this investigation. It was found that the groups of discharge were lighter in their isotopic composition than that of recharge. The previous explanation of this fact, backed by carbon-14 dating, was the long residence time due to flow lines going down to depths of more than 1000 m. This flow model assumes homogenous conditions to these depths. This assumption can not be supported by evidence from deep wells. Thus a modified model is suggested which maintains homogenous conditions only to about 300 m and a deep confined aquifer below containing paleowater. The higher degree of depletion of this water has been explained by a colder climate on top of an altitude effect. Another interesting observation was the correlation between the isotopic composition of the rains, the month of the rain event and the composition of the recharge group groundwater. It could be seen that the winter rains resemble the groundwater composition, which shows that practically all the spring and summer rains were evapotranspirated.     

Contributions of boron isotopes to understanding the hydrogeochemistry of the coastal detritic aquifer of Castellón Plain,Spain

The Castellón Plain alluvial aquifer, Spain, is intensively exploited to meet the demand for agricultural irrigation and industrial water supply. The geochemistry of its groundwater shows complex salinization in the northern and southern parts of the aquifer, with significant pollution from human origin in the central portion. Boron content and B isotope geochemistry are useful for distinguishing between various sources of pollution and their relative importance in different parts of this aquifer. Boron concentrations in the groundwater vary between 0.01 and 0.85 mg/L. In the more saline groundwaters, found at the northern and southern ends of the study area, the presence of B is linked to inputs from seawater and water with a calcium-magnesium sulphate facies, which feed the aquifer and clearly influence the chemistry of its waters. Evidence of B adsorption processes in some samples is shown by the low B/Cl ratios and the high values of δ¹¹B. In the central portion of the aquifer, the high B/Cl ratios and the strongly negative δ¹¹B are related to pollution of human origin.     

Extension spatiale de la salinisation des ressources en eau et modèle conceptuel des sources salées dans la plaine des Triffa (Maroc nord-oriental)

The succession of drought years and excessive abstraction in the plain of Triffa caused deterioration in water quality and endangers future exploitation of groundwater resources. A combination of geophysical surveys, including electrical resistivity and hydrochemical data has been used to identify the geographical extension of salinization and identify its origin. Electrical conductivity measurements are used to show the history of salinization in space and time. In this paper, a first conceptual model of the brackish springs has been established. To cite this article: M. Boughriba et al., C. R. Geoscience 338 (2006).     

A new approach for the development and management of brackish karst springs

A new approach to the method of artificial upraising of the water outlet point, for management and development of brackish karst springs, uses the MODKARST model. Brackish karst springs simulation can be used to estimate the necessary upraising of the spring elevation, so that sea-water intrusion is blocked. The consequent freshwater loss to the sea, due to this upraising, can also be estimated. The method has been applied to the periodically brackish karst Almiros spring at Heraklion of Crete, Greece. The spring simulation showed that the sea-water intrusion could be prevented through an artificial upraising of the water-outlet point, realized by the construction of a dam. The exact upraising has been estimated. Freshwater loss to the sea because of this upraising has also been estimated. The model could also be used as a tool for the management of the spring. For example, it was used to assess management options for the spring during the depletion period of the year 1994. The best scenario for the development of the spring during this period has been estimated.     

The influence of marine inflows on the chemical composition of groundwater in small islands: the example of the Cyclades (Greece)

 Marine contamination of groundwater may be caused by seawater intrusion and by salt spray. The role of both processes was studied in the Cyclades archipelago on four small islands (45–195 km²) whose aquifers consist essentially of fractured, weathered metamorphic rocks. Annual rainfall ranges from 400 to 650 mm and precipitation has high total dissolved solids contents of 45–223 mg l^–1. The chemical characteristics of the groundwater, whose salinity is from 0.4 to 22 g l^–1, are strongly influenced by seawater intrusion. However, the effect of atmospheric input is shown in certain water sampling locations on high ground elevation where the dissolved chloride contents may attain 200 mg l^–1. Received: 14 November 1995 · Accepted: 9 September 1996     

Salinisation des nappes côtières : cas de la nappe nord du Sahel de Sfax,Tunisie

The intensive agricultural and economic activities induce the increase of the risk of groundwater quality degradation through high groundwater pumping rates. The salinization and contamination are the main sources of this pollution, especially in coastal aquifers. The explanation of the origin of salinity for the shallow aquifer of Northern Sahel of Sfax was analysed by a chemical study of the groundwater main compounds. The partitioning of groundwaters into homogenous groups is undertaken by graphical techniques, including a Stiff pattern diagram, an expanded Durov diagram and several binary diagrams. The study indicates the presence of various salinization processes. In the recharge area, salinization is the result of dissolution/precipitation of the aquifer formation material (group I). The irrigation water return and the intensive pumping have been identified as major sources of salinization in the south by direct cation exchange and mixing reactions (groups II and III). The anomaly of high groundwater salinity observed near the Hazeg zone was explained by the presence of a seawater intrusion in this area. This hypothesis is related to the high chloride concentration, to the presence of inverse cation exchange reactions (group IV), and to the piezometric level inferior to sea level. To cite this article: R. Trabelsi et al., C. R. Geoscience 337 (2005).     

黄河三角洲芦苇湿地生态修复效果评价研究

基于黄河三角洲芦苇湿地退化现状及所实施的生态修复工程,以正负参照系选取了4块不同修复年限的样地,从湿地生态系统的环境质量、结构与功能的角度构建了湿地修复效果评价指标体系,利用层次分析法确定各指标权重,利用模糊综合评价法对黄河三角洲盐渍化芦苇湿地的修复效果进行定量评价。结果表明:黄河三角洲芦苇湿地4年修复期的样地评价得分为4.01,2年修复期的样地评价得分为3.16,对应评价结果分别为"优"和"良"的等级。相比负向对照,修复区的水体指标和土壤指标参数显著改善,而植被生物量和密度与自然样地还有较大差距,说明生物群落的建立需要更长的时间;同时,湿地水资源管理是该区芦苇湿地生态修复工程的关键,应根据芦苇不同生长期的需水量,制定合理的抽灌制度,达到洗碱脱盐和植被建群的双重目的。     

Hydrogeology of the Winnipeg Formation in Manitoba, Canada

The Winnipeg Formation is the basal sedimentary unit throughout much of southern and central Manitoba, Canada, where it forms a regional aquifer over most of its extent. This aquifer is an important source of water in southeastern Manitoba and in Manitoba’s Interlake area, but in most other areas, groundwater within the aquifer is saline. Chemical and isotopic evidence indicate the presence of groundwaters of three different origins: (1) basin brines; (2) modern meteoric recharge; and (3) subglacial recharge that occurred during the late Pleistocene. Hydraulic head and sedimentary facies distributions indicate that the flow system in parts of the area is not in a state of equilibrium and saline waters will encroach on areas currently occupied by freshwater in some areas, while in other areas, freshwater will replace saline water. These features must be considered in groundwater resource management, as groundwater withdrawals will likely hasten these processes.

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Resumen La Formación Winnipeg es la unidad sedimentaria basal en la mayor parte de Manitoba central, Canadá, donde forma un acuífero regional en la mayor parte de su extensión. Este acuífero es una fuente importante de agua en el Sureste de Manitoba y el área de entrelagos de Manitoba, pero en la mayoría de las otras zonas del acuífero, el agua es salina. Las evidencias químicas e isotópicas indican que existen aguas subterráneas de tres orígenes diferentes: (1) salmueras de cuenca; (2) recarga meteórica actual; y (3) recarga subglacial ocurrida durante el Pleistoceno Superior. Los niveles piezométricos y la distribución de las facies sedimentarias indican que el sistema de flujo no se encuentra en estado de equilibrio en parte del área y las aguas salinas irán invadiendo áreas actualmente ocupadas con aguas dulces, mientras que en otras zonas el agua dulce está reemplazando al agua salina. Estos hechos deben ser considerados en la gestión de las aguas subterráneas como recurso, ya que las extracciones de agua acelerarán probablemente estos procesos.

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Résumé La Formation de Winnipeg est l’unité sédimentaire de base sur la plus grande partie du Sud et du centre du Manitoba au Canada, où elle forme un aquifère régional sur pratiquement toute son extension. Cet aquifère représente une ressource en eau importante dans le Sud-Est du Manitoba et dans les zones d’entre les lacs, mais salée dans la plus part des autres zones. Les indications isotopiques et chimiques permettent de distinguer trois différentes origines des eaux souterraines: (1) les saumures de bassin; (2) la recharge météoritique moderne; (3) la recharge sub-glaciaire qui est apparue durant le Pléistocène récent. Les charges hydrauliques et la distribution des faciès sédimentaires indiquent que le système d’écoulement dans certaines zones n’est pas dans un état d’équilibre et que les eaux salées empièteront sur des zones d’eau douce, tandis que dans d’autres zones l’eau douce remplacera les eaux salées. Ces aspects doivent être considérés dans la gestion des ressources en eau souterraine, car le prélèvement des eaux souterraines pourrait accentuer ces processus.

     

Aquifer development planning to supply a seaside resort: a case study in Goa,India

Using the hydrogeological and socio-economic data derived from a European Commission research project on the measurement, monitoring and sustainability of the coastal environment, two optimization models have been applied to satisfy the future water resources needs of the coastal zone of Bardez in Goa, India. The number of tourists visiting Goa since the 1970s has risen considerably, and roughly a third of them go to Bardez taluka, prompting growth in the tourist-related infrastructure in the region. The optimization models are non-linear mixed integer models that have been solved using GAMS/DICOPT++ commercial software. Optimization models were used, firstly, to indicate the most suitable zones for building seaside resorts and wells to supply the tourist industry with an adequate amount of water, and secondly, to indicate the best location for wells to adequately supply pre-existing hotels. The models presented will help to define the optimal locations for the wells and the hydraulic infrastructures needed to satisfy demand at minimum cost, taking into account environmental constraints such as the risk of saline intrusion.

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Résumé A l’aide de données hydrogéologiques et socio-économiques, dérivées d’un projet de recherche de la Commission Européenne sur l’étude, la surveillance et la durabilité de l’environnement c?tier, deux modèles d’optimisation ont été appliqués en vue de satisfaire les besoins futurs en ressources en eau de la zone c?tière de Bardez au Goa en Inde. Le nombre de touristes qui visitent le Goa depuis les années 70 a considérablement augmenté et environ un tiers d’entre eux se rend à Bardez taluka, ce qui encourage la croissance des infrastructures liées au tourisme dans la région. Les modèles d’optimisation sont des modèles non linéaires mixtes en nombres entiers qui ont été résolus en utilisant le logiciel commercial GAMS/DICOPT++. Les modèles d’optimisation ont été utilisés pour indiquer premièrement les zones les plus appropriées pour construire des stations balnéaires et des puits pour approvisionner en quantité d’eau suffisante l’industrie touristique, et deuxièmement pour indiquer la meilleure localisation de puits pour l’alimentation des h?tels préexistants. Les modèles présentés aideront à définir les localisations optimales des puits et des infrastructures hydrauliques nécessaires à la satisfaction de la demande à un co?t minimum, tout en prenant en compte les contraintes environnementales, tel que le risque d’intrusion saline.

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Resumen Se han aplicado dos modelos de optimización en base a datos socio-económicos e hidrogeológicos derivados de un proyecto de investigación de la Comisión Europea sobre medición, monitoreo y sostenibilidad del ambiente costero para satisfacer las necesidades futuras de recursos hídricos de la zona costera de Bardez en Goa, India. El número de turistas que visita Goa desde la década de 1970′s ha subido considerablemente y cerca de un tercio de ellos van a Bardez taluka impulsando el crecimiento en la infraestructura turística de la región. Los modelos de optimización son modelos de números enteros mixtos no-lineales que se han resuelto usando el programa comercial GAMS/DICOPT++. Los modelos de optimización se usaron, primero para indicar las zonas más adecuadas para la construcción de centros de diversión en las márgenes del océano y pozos para abastecer la industria turística con una adecuada cantidad de agua, y segundo, para indicar la mejor localización de pozos para el abastecimiento de hoteles pre-existentes. Los modelos que se presentan ayudarán a definir las localizaciones óptimas para los pozos y las infraestructuras hidráulicas necesarias para satisfacer la demanda al mínimo costo, tomando en consideración restricciones ambientales tal como el riesgo de intrusión salina.