Intrusion of Saline Water into a Coastal Aquifer Containing Palaeogroundwater in the Viimsi Peninsula in Estonia

The Viimsi peninsula is located north-east of Tallinn, capital of Estonia. The Cambrian-Vendian (Cm-V) aquifer system is a sole source of drinking water in the area. Historically, the groundwater exploitation has led to freshening of groundwater in the peninsula, but in recent years an increase in chloride concentrations and enrichment in δ18O values has been detected, but in recent years hydrochemical parameters indicate an increasing influence of a saline water source. The exact origin of this saline water has remained unclear. The aim of the current study is to elucidate whether the increase in Cl− concentrations is related to seawater intrusion or to the infiltration of saline water from the underlying crystalline basement. To identify the source of salinity, chemical composition of the groundwater and the isotope tracers (e.g., δ18O and radium isotopes) were studied in the Viimsi peninsula in the period from 1987 to 2018. Our results show that chemical composition of Cm-V groundwater in the peninsula is clearly controlled by three-component mixing between glacial palaeogroundwater, saline water from the underling crystalline basement and modern meteoric water. The concentrations of Ra are also significantly affected by the mixing, but the spatial variation of radium isotopes (226Ra and 228Ra) suggests the widespread occurrence of the U in the surrounding sedimentary sequence. Our hypothesis is that, in addition to U originating from the crystalline basement, some U could be associated with secondary U deposits in sedimentary rocks. The formation of these secondary U deposits could be related to glacial meltwater intrusion in the Pleistocene. Although the results suggest that the infiltration of saline groundwater from the underlying crystalline basement as the main source of salinity in the study area, the risk of seawater intrusion in the future cannot be ruled out. It needs to be highlighted that the present groundwater monitoring networks may not be precise enough to detect the potential seawater intrusion and subsequent changes in water quality of the Cm-V aquifer system in the Viimsi peninsula.

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Modelling tools for quantitative evaluations on the Versilia coastal aquifer system (Tuscany, Italy) in terms of groundwater components and possible effects of climate extreme events

Acque Sotterranee-Italian Journal of Groundwater ◽

10.7343/as-2020-475 ◽

2020 ◽

Vol 9 (3) ◽

Author(s):

Matia Menichini ◽

Marco Doveri

Keyword(s):

Seawater Intrusion ◽

Extreme Events ◽

Coastal Aquifer ◽

Climate Extreme ◽

Aquifer Recharge ◽

Hydrogeological Model ◽

Groundwater Exploitation ◽

Aquifer System ◽

Open Platform ◽

Adequate Knowledge

The Versilia coastal plain hosts an important and strategic aquifer for water supply. Like all coastal aquifers, it is particularly vulnerable to the saltwater intrusion, which can be amplified not only by fresh water over-exploitation, but also by the effects of climate change, including the increase of extreme events. For an optimal management of this precious resource and for its protection both in quantitative and qualitative terms, an adequate knowledge of the aquifer system is necessary through the development of conceptual and mathematical hydrogeological models. The conceptual hydrogeological model was defined on the base of an integrated multidisciplinary approach with the elaboration of stratigraphic, hydrogeological and geochemical-isotopic data. Subsequently, groundwater flow mathematical models were created using the ModFlow code and Groundwater Vistas like graphical interface, subsequently transferred to the Freewat open platform. The models enabled acquiring further knowledge about this aquifer system and to identify and, where possible to quantify, the main processes and groundwater components involved, including the seawater ingression. An important groundwater component, both in terms of water quantity and quality,resulted widespread in the fan of the Versilia River and mainly fed by the river itself in the foothill zone. Although this component seems to be able to guarantee relative protection against marine ingression, in the summer season some piezometric depressions tied to groundwater exploitation tend to expand and move towards the coast, thus favouring the seawater intrusion process. These issues can be amplified by the extreme rainy events that frequently occur in the Apuan Alps region. The huge quantity of water that quickly flows by the river up to the sea during extreme events represents a lack of feeding respect to the aquifer, and consequently the mitigation role of the fan component towards seawater intrusion can be significantly weakened. Thanks to the water budget achieved by numerical model and considering real extreme events recently occurred in the Apuan-Versilian region it was possible to make considerations about possible effects these climate regimes on the aquifer system. As outcomes, we concluded that extreme events as those occurred in the area in the past, and awaited more frequently in the future, represent a concrete threat for the coastal aquifer system that over next decades could suffer more and more seawater intrusion. Given the reliance of local human activities on groundwater, far-sighted actions of water management (e.g. managed aquifer recharge) are recommended for mitigating such as climate effects.

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High Resolution Monitoring of Seawater Intrusion in a Multi-Aquifer System-Implementation of a New Downhole Geophysical Tool

Water ◽

10.3390/w11091877 ◽

2019 ◽

Vol 11 (9) ◽

pp. 1877 ◽

Cited By ~ 3

Author(s):

Tal ◽

Weinstein ◽

Baïsset ◽

Golan ◽

Yechieli

Keyword(s):

Electrical Conductivity ◽

Electric Conductivity ◽

Seawater Intrusion ◽

Saline Water ◽

Near Field ◽

Aquifer System ◽

Monitoring Wells ◽

New Device ◽

Subsurface Monitoring ◽

The Impact

Monitoring of seawater intrusion is extremely important for the management of coastal aquifers, and therefore requires reliable and high-frequency monitoring tools. This paper describes the use of a new near field and downhole geophysical tool that monitors seawater intrusion in boreholes with high vertical resolution. This sensor is further used to study the impact of pumping on water electrical conductivity profiles (ECP) at the fresh-saline water interface. The new device was installed in a confined calcareous sandstone aquifer along the northern Israeli coast. The site includes two monitoring wells and one pumping well located at distances of 50, 75 and 125 m from shoreline, respectively. The new geophysical tool, called the subsurface monitoring device (SMD), was examined and compared to water an electric conductivity profiler (ECP) and a conductivity temperature depth (CTD) driver’s data. All methods show similar salinity trends, and changes in pumping regime were clearly identified with both the SMD and CTD. The advantage of using the SMD tool is the high temporal and spatial resolution measurement, which is transferred via internet and can be analyzed and interpreted in real time. Another advantage of the SMD is that it measures the electrical resistivity of the aquifer mostly outside the well, while both water ECP and the CTD measure in-well electrical conductivity; therefore, are subjected to the artefact of vertical flow in the well. Accordingly, while the CTD shows an immediate and sharp response when pumping is stopped, the SMD provides a gradual electric conductivity (EC) change, demonstrating that stability is reached just after a few days, which illustrates, more precisely, the hydrological response of the aquifer.

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Upconing of saline water from the crystalline basement into the Cambrian–Vendian aquifer system on the Kopli Peninsula, northern Estonia

Estonian Journal of Earth Sciences ◽

10.3176/earth.2010.4.04 ◽

2010 ◽

Vol 59 (4) ◽

pp. 277 ◽

Cited By ~ 6

Author(s):

A Marandi ◽

L Vallner

Keyword(s):

Saline Water ◽

Crystalline Basement ◽

Aquifer System

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Effect of irrigation with saline water on growth and chemical composition of celery

Al-Azhar Journal of Agricultural Research ◽

10.21608/ajar.2019.102834 ◽

2019 ◽

Vol 44 (2) ◽

pp. 165-171

Author(s):

A. Ashmawi

Keyword(s):

Chemical Composition ◽

Saline Water

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Regulation of rectal secretion in saline-water mosquito larvae living in waters of diverse ionic composition

Journal of Experimental Biology ◽

10.1242/jeb.66.1.83 ◽

1977 ◽

Vol 66 (1) ◽

pp. 83-96 ◽

Cited By ~ 2

Author(s):

T. J. Bradley ◽

J. E. Philips

Keyword(s):

Chemical Composition ◽

External Medium ◽

Saline Water ◽

Ionic Composition ◽

Malpighian Tubules ◽

Fluid Composition ◽

Mosquito Larvae ◽

Major Site ◽

Osmotic Concentration ◽

Anal Papillae

1. Larvae of the saline-water mosquito Aedes campestris were adapted to three waters, all having an osmotic concentration of 700 mOsm, but differing in ionic rations. The (Na+Mg) SO4 medium was much moretoxic than the NAHCO3 or the NaCl media. 2. Ionic and osmotic concentrations of haemolymph and rectal secretion were measured in larvae adapted to all three media. The ratio of ionic concentrations in the rectal secretion reflected those in the external medium to which the larvae had been adapted, with the exception of SO42-, which was possibly replaced by HCO3-in the secretion. These differences in rectal fluid composition persisted even though all ligated recta were bathed in the same artificial haemolymph. 3. The Malpighian tubules were found to be the major site of SO42- excretion. In media containing high levels of NA+, Mg2+, K+, Cl- and HCO3-, the rectum secreted a hyperosmotic fluid containing these ions at concentrations several times greater than those found in the haemolymph. 4. These data provide the basis for speculation on the functioning of anal papillae in waters of diverse chemical composition.

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Salinization effects on coastal ecosystems: a terrestrial model ecosystem approach

Philosophical Transactions of the Royal Society B Biological Sciences ◽

10.1098/rstb.2018.0251 ◽

2018 ◽

Vol 374 (1764) ◽

pp. 20180251 ◽

Cited By ~ 5

Author(s):

C. S. Pereira ◽

I. Lopes ◽

I. Abrantes ◽

J. P. Sousa ◽

S. Chelinho

Keyword(s):

Seawater Intrusion ◽

Crop Yields ◽

Plant Biomass ◽

Saline Water ◽

Sampling Period ◽

Ecosystem Approach ◽

Soil Salinization ◽

Negative Effects ◽

Saline Irrigation ◽

Delayed Effects

In coastal areas, intrusion/irrigation with seawater can threaten biodiversity along with crop yields, and the leaching of salts from areas affected by these processes can increase the salinity of water bodies nearby. The aims of this study were to evaluate the effects of salinization on coastal soil ecosystems due to saline intrusion/irrigation. Terrestrial model ecosystems were used to simulate two soil salinization scenarios: (i) seawater intrusion and irrigation with distilled water and (ii) seawater intrusion and irrigation with saline water. Three sampling periods were established: T0—after acclimation period; T1—salinization effects; and T2—populations' recovery. In each sampling period, the abundance of nematodes, enchytraeids, springtails, mites and earthworms, and plant biomass were measured. Immediate negative effects on enchytraeid abundance were detected, especially at the higher level of saltwater via intrusion+irrigation. Eight weeks after the cessation of saline irrigation, the abundance of enchytraeids fully recovered, and some delayed effects were observed in earthworm abundance and plant biomass, especially at the higher soil conductivity level. The observed low capacity of soil to retain salts suggests that, particularly at high soil conductivities, nearby freshwater bodies can also be endangered. Under saline conditions similar to the ones assayed, survival of some soil communities can be threatened, leading to the loss of biodiversity. This article is part of the theme issue ‘Salt in freshwaters: causes, ecological consequences and future prospects’.

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Modelling multi-fissure zones above buried rock ridges in subsiding basins

10.5194/egusphere-egu21-7931 ◽

2021 ◽

Author(s):

Li yueting ◽

Pietro Teatini ◽

Shujun Ye ◽

Andrea Franceschini ◽

Matteo Frigo ◽

...

Keyword(s):

Land Surface ◽

Sedimentary Basins ◽

Interface Elements ◽

Groundwater Exploitation ◽

Aquifer System ◽

Sedimentary Sequences ◽

Earth Fissures ◽

One Year ◽

Stress Accumulation ◽

Maximum Opening

<p>Aseismic earth fissures due to the excessive groundwater exploitation have caused seriously damage in many subsiding sedimentary basins worldwide. Generally, multiple fissures almost parallel to each other with equal distances are prone to develop where a compacting aquifer system overlies impermeable and/or incompressible ridges. Here, an advanced finite-element interface-elements modelling approach is employed to understand this process within unfaulted sedimentary sequences. A simplified geological setting is initially used to investigate the effect of the ridge slope on ruptures behaviors. Then, we reproduce the case of Guangming village, China. In both the proposed scenarios, the model simulates the occurrence of multi-fissures that initiate at land surface and propagate downward, as observed in the sites. The earth fissures are formed as a result of the combination of tensile stress (bending condition) and shear stress (shearing conditions) accumulation around and above the tip and the slopes of the ridge, respectively. The numerical outcomes indicate that the steeper ridge results in higher magnitude stress accumulation above the ridge tip which favors the formation of fissures with significant opening and small or null offset, but at expense of the reduction in stress accumulation area and fissure distribution. In Guangming case, the outcomes show that two ruptures started sliding and only one year later a central fissure opened and propagated down to 15-30 m depth. The simulated maximum opening and sliding of the central and side fissures, respectively, approximate 30 cm, which are almost in agreement with the observations. The numerical results prove that the proposed modeling approach is an effective way to predict and analyze multi-fissure onset and development in subsiding basins.</p>

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Analysis of Water Cycle in Weizhou Island of Beihai City, Guangxi Province, Part II: Study On Groundwater Exploitation Plan

MATEC Web of Conferences ◽

10.1051/matecconf/201824602047 ◽

2018 ◽

Vol 246 ◽

pp. 02047

Author(s):

Shunfu Zhang ◽

Changjun Liu ◽

Chuanke Li ◽

Sili Long ◽

Jian Zhou ◽

...

Keyword(s):

Groundwater Flow ◽

Ground Water ◽

Seawater Intrusion ◽

Groundwater Level ◽

Water Cycle ◽

Variable Density ◽

Analysis Model ◽

Guangxi Province ◽

Groundwater Exploitation ◽

Groundwater Levels

To relieve the drop of groundwater and seawater intrusion in Weizhou Island caused by overexploitation, the analysis model of precipitation-runoff and variable-density groundwater flow in Weizhou Island was established and the model’s parameter identification results were used to investigate groundwater level and seawater/freshwater interface changes under different groundwater exploitation plans. Thereafter, a rational groundwater exploitation plan could be made to prevent the lowering of groundwater levels caused by ground water overexploitation and ecological deterioration caused by seawater intrusion. This could help accelerating the recovery of ground water and maintaining ecological system.

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Quantitative estimations of aquifer properties from resistivity in the Bolivian highlands

H2Open Journal ◽

10.2166/h2oj.2019.007 ◽

2019 ◽

Vol 2 (1) ◽

pp. 113-124

Author(s):

Etzar Gómez ◽

Viktor Broman ◽

Torleif Dahlin ◽

Gerhard Barmen ◽

Jan-Erik Rosberg

Keyword(s):

Hydraulic Conductivity ◽

Saline Water ◽

Cost Effective ◽

Unconsolidated Sediments ◽

Aquifer System ◽

Transient Electromagnetic ◽

Rock Formations ◽

Hydrogeological Characteristics ◽

Electrical Soundings ◽

Available Information

Abstract Resistivity data constitute the largest part of the available information to assess the hydrogeological characteristics of the aquifer system near Oruro, in the central part of the Bolivian Altiplano. Two aquifers are part of this system; top unconsolidated sediments storing fresh water in their granular voids, overlying fractured hard rock formations where saline water was detected in connection to some faults. This study proposes an indirect and cost-effective way to estimate aquifer hydraulic properties for the groundwater management in the region. Hydraulic conductivity and transmissivity in the top aquifer were estimated using an empirical linear relationship between hydraulic conductivity and resistivity. This latter parameter, as well as the aquifer thickness, were obtained from the inverted models corresponding to the geoelectrical tests performed in the study area (electrical resistivity tomography, transient electromagnetic soundings and vertical electrical soundings). The highest estimated transmissivity values are ∼4.0 × 10−2 m2/s located in the centre of the study area, the lowest values are ∼3.4 × 10−3 m2/s, located around thermal intrusions to the south and where the top of the bedrock is shallow (∼20 m depth) to the west. The methodology presented in this study makes wider use of resistivity measurements to identify promising groundwater production sites.

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