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Dynamics of saltwater intrusion and submarine groundwater discharge in confined coastal aquifers: a case study in northern Israel

  • Anner PaldorEmail author
  • Eyal Shalev
  • Oded Katz
  • Einat Aharonov
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Abstract

Many coastal areas around the world suffer severe water stresses due to improper management of water resources. In these areas, groundwater is typically the most important source for drinking water, and its overexploitation may lead to deterioration in water quality. In coastal confined aquifers, the dynamics of saltwater intrusion (SWI) and well salinization are the focus of many recent studies that commonly do not include a geological study of the subsurface structure of the aquifer. The goal of the present work is to study the effect of groundwater extraction on SWI, using the Judea Group Aquifer as a case study representing a coastal confined aquifer that suffers drawdown due to excess pumping. First, the offshore-onshore structure of the aquifer is described, and then a groundwater model is constructed based on the inferred structure. The resulting model shows that under realistic conditions, a water well situated 5 km inland from the shoreline is expected to undergo salinization after ~190 years since level drop. The SWI advances inland faster when the confinement is efficient, suggesting that semi-confined aquifers should be preferred for pumping compared with confined ones. Additionally, the model shows that under certain conditions, deep submarine groundwater discharge (SGD) occurs through the aquifer outcrop, ~15 km offshore and at depths of ~200 m. The SGD comprises brackish and warm water. The insights from this work are important both for studies on freshwater budgets in coastal areas and for the study of SGD and its implications for the ocean.

Keywords

Saltwater intrusion Submarine groundwater discharge Coastal aquifers Confining units Israel 

Dynamique de l’intrusion saline et des sorties sous-marines d’eaux souterraines d’aquifères côtiers captifs: un cas d’étude dans le nord d’Israël

Résumé

De nombreuses régions du monde souffrent d’importants stress hydriques à cause d’une gestion impropre des ressources en eau. Dans ces régions, les eaux souterraines constituent généralement la plus importante source d’approvisionnement pour l’alimentation en eau potable, et leur surexploitation peut conduire à une détérioration de la qualité de l’eau. Pour les aquifères côtiers captifs, les dynamiques de l’intrusion d’eau salée (IES) et la salinisation des puits sont la cible de nombreuses études récentes qui généralement n’intègrent pas d’étude géologique de la structure de l’aquifère. L’objectif de ce présent travail est d’étudier l’effet de l’exploitation des eaux souterraines sur IES, en utilisant l’aquifère du groupe de Judée comme cas d’étude représentatif d’un aquifère côtier captif qui subit une diminution des niveaux des eaux souterraines, due à des pompages excessifs. Tout d’abord, la structure du continuum terre-mer de l’aquifère est décrite, et ensuite un modèle hydrogéologique est établi à partir de cette structure. Le modèle résultant montre que pour des conditions réalistes, un puits situé à 5km du rivage à l’intérieur des terres devrait subir une salinisation après ~190 ans depuis la diminution du niveau d’eau. L’IES progresse plus rapidement vers l’intérieur des terres lorsque le caractère captif de l’aquifère est efficace, suggérant que les aquifères semi-captifs devraient être préférés pour les pompages en comparaison avec les aquifères captifs. De plus, le modèle montre que pour certaines conditions, les sorties sous-marines d’eaux souterraines (SSES) en profondeur se produisent au niveau de l’affleurement de l’aquifère, ~15 km au large et à des profondeurs de ~200 m. Les SSES sont caractérisées par des eaux saumâtres et chaudes. Les enseignements tirés de ce travail sont importants à la fois pour les études sur les bilans hydriques d’eau douce dans les zones côtières et pour l’étude des SSES et leurs implications pour l’océan.

Dinámica de la intrusión de agua salada y la descarga submarina de aguas subterráneas en acuíferos costeros confinados: un estudio de caso en el norte de Israel

Resumen

Muchas zonas costeras de todo el mundo sufren graves tensiones hídricas debido a una gestión inadecuada de los recursos hídricos. En estas zonas, el agua subterránea suele ser la fuente más importante de agua potable, y su sobreexplotación puede dar lugar a un deterioro de la calidad del agua. En los acuíferos confinados costeros, la dinámica de la intrusión de agua salada (SWI) y la salinización de pozos son el foco de muchos estudios recientes que comúnmente no incluyen un estudio geológico de la estructura del acuífero en el subsuelo. El objetivo del presente trabajo es estudiar el efecto de la extracción de agua subterránea sobre la SWI, utilizando el Judea Group Aquifer como un estudio de caso que representa un acuífero confinado costero que sufre una depresión debido a un bombeo excesivo. Primero, se describe la estructura del acuífero dentro y fuera de la costa, y luego se construye un modelo de agua subterránea basado en la estructura inferida. El modelo resultante muestra que, bajo condiciones realistas, se espera que un pozo de agua situado a 5 km tierra adentro de la costa sufra salinización después de ~190 años desde la caída del nivel. El SWI avanza más rápido hacia el interior cuando el confinamiento es eficiente, lo que sugiere que los acuíferos semiconfinados deben ser preferidos para el bombeo en comparación con los confinados. Además, el modelo muestra que, bajo ciertas condiciones, la descarga submarina profunda de aguas subterráneas (SGD) ocurre a través del afloramiento del acuífero, ~15 km mar adentro y a profundidades de ~200 m. La SGD comprende agua salobre y caliente. Los resultados de este trabajo son importantes tanto para los estudios sobre los balances de agua dulce en las zonas costeras como para el estudio de la SGD y sus implicancias en el océano.

承压沿海含水层中海水入侵和海底地下水排泄动态:以以色列北部为例

摘要

由于水资源管理不当, 世界上许多沿海地区水资源压力大。在这些地区, 地下水通常是最重要的饮用水水源, 其过度开采会导致水质恶化。在沿海承压含水层中, 盐水入侵 (SWI)和井的盐化的动态是近年来研究的热点, 这些研究通常不包括含水层地下结构的地质研究。本研究的目的是研究地下水开采对SWI的影响:以Judea Group Aquifer为例阐述由于过度开采产生水位降深的沿海承压含水层。论文首先描述了含水层的海陆结构, 然后根据推断的结构构建了地下水模型。模型研究表明在理想条件时, 距离海岸线5公里的水井预计在水位下降后约190年后将产生盐化。当承压性很好时, SWI更快地向内陆推进, 表明与承压含水层相比, 半承压含水层应该优先被抽取。此外, 模型还表明在某些条件下, 深部海底地下水排放量(SGD)在距离海岸约15 km、深度约200 m的含水层露头产生。 SGD包括微咸水和温水。本研究形成的认识对于沿海地区的淡水水量平衡研究和SGD 研究及其对海洋的影响都很重要。

Dinâmica de intrusão salina e descarga submarina de água subterrânea em aquíferos confinados costeiros: um estudo de caso no nordeste de Israel

Resumo

Muitas áreas costeiras ao redor do mundo sofrem severos estresses de abastecimento devido à gestão imprópria dos seus recursos hídricos. Nessas áreas, a água subterrânea é tipicamente a fonte mais importante de água potável para consumo, e sua superexplotação pode levar à deterioração da qualidade da água. Em aquíferos confinados costeiros, a dinâmica da intrusão de água salina (IAS) e a salinização de poços são o foco de muitos estudos recentes, que comumente não incluem um estudo geológico estrutural do aquífero. O objetivo do presente trabalho é estudar o efeito da extração de água subterrânea no processo de IAS a partir do estudo de caso do Aquífero do Grupo Judéia, um aquífero confinado costeiro, que sofre rebaixamento devido ao bombeamento excessivo. Primeiro, descreve-se a estrutura do aquífero costeiro (porção terrestre e oceânica), em seguida, constrói-se um modelo hidrogeológico baseado na estrutura inferida. O modelo resultante mostra que, sob condições realistas, um poço de água situado a 5 km da costa deverá sofrer salinização após ~190 anos desde a queda de seu nível d’água. A IAS avança no interior mais rapidamente quando o confinamento do aquífero é eficiente, sugerindo que os aquíferos semiconfinados devem ser preferidos para o bombeamento em comparação com os confinados. Além disso, o modelo mostra que sob certas condições, a descarga submarina profunda de água subterrânea ocorre através do afloramento do aquífero, a ~15 km da costa e ~200 m profundidade. Essa descarga é composta por água salobra e morna. Os resultados deste trabalho são importantes tanto para estudos econômicos de abastecimento de água potável em áreas costeiras, quanto para o estudo da descarga submarina profunda de águas subterrâneas e suas implicações para o oceano.

Notes

Acknowledgements

The work was supported by the Israel Science Foundation (grant 954/15 to O.K.). The Authors thank the DHI group (https://www.mikepoweredbydhi.com/) for the use of the FEFLOW software under academic license. The authors also wish to thank the Mediterranean Sea Research Center of Israel for their support of this research.

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Copyright information

© Springer-Verlag GmbH Germany, part of Springer Nature 2019

Authors and Affiliations

  1. 1.Institute of Earth SciencesHebrew University of JerusalemJerusalemIsrael
  2. 2.Geological Survey of IsraelJerusalemIsrael

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