scholarly journals Coastal Groundwater Dynamics - Investigation of Using Geoelectrical and Hydrochemical Tools for Saline Intrusion Monitoring

2021 ◽  
Author(s):  
◽  
Eva Maria Sutter
Keyword(s):  
Time Series ◽  
Seawater Intrusion ◽  
Tidal Cycle ◽  
Preferential Flow ◽  
Groundwater Resources ◽  
Time Frame ◽  
Real Field ◽  
Major Influence ◽  
Fresh Groundwater ◽  
Mixing Behaviour

<p>With over 65 % of the global population currently living in areas near a coast, increasing fresh groundwater demands within these areas, shifted precipitation patterns, and rising mean sea levels, increased seawater intrusion into coastal aquifers has become a major issue for groundwater resources in many coastal countries all around the world. Although there are many past studies researching the saline interface in affected aquifers from a modelling, laboratory or field perspective with different hydrological and geophysical approaches, little is known about real field dynamics over various time spans and in different geological settings. This PhD project aims at detecting and characterising seawater intrusion into a shallow coastal Holocene sand and gravel aquifer at New Zealand's west coast with respect to seasonally changing aquifer resistivity and hydrochemical tracers, as well as investigating resistivity and hydraulic property changes within a tidal time frame. Seawater mixing behaviour over different time spans was monitored with electrical resistivity tomography (ERT) over the course of two years, and additional hydrochemical sampling was carried out during the second year of the long-term seawater intrusion monitoring study. During two consecutive years, repeat ERT measurements were able to determine seasonal and shorter-term cycles in seawater mixing behaviour within the shallow coastal aquifer. There are strong indications that increasing urbanisation has a major influence on seasonal seawater intrusion patterns, and the dominant processes at the field locations were identified to be tied to the amount of freshwater available over the course of a year, as well as enhanced evapotranspiration / evaporation during summer. Hydrochemical data backed these observations and were also able to characterise seawater intrusion as a function of depth at the field location. Within the smaller tidal cycle investigations, similarly behaving parts of the aquifer could be identified from resistivity ratios and time series analyses. Varying amplitudes in resistivity changes led to the conclusion that saline mixing within a diurnal tidal cycle is strongly dependent on the recharge regime of the aquifer and decreases significantly for times during the year when recharge is continuous as opposed to times with little general recharge but intense, isolated rainfall events. In addition, tidal time series were used to qualitatively infer hydraulic properties of the aquifer and ultimately delineate preferential flow paths for seawater intrusion at the field site. The results of this project support findings of previous modelling, laboratory and short-term field studies, and put the concepts into a much broader time frame. For the first time the dynamics of seawater mixing in a shallow coastal sand aquifer were conclusively studied at the same location and within different time frames, and are thus of great value for sustainable groundwater management in the area of investigation and similar coastal environments.</p>

scholarly journals Coastal Groundwater Dynamics - Investigation of Using Geoelectrical and Hydrochemical Tools for Saline Intrusion Monitoring

2021 ◽  
Author(s):  
◽  
Eva Maria Sutter
Keyword(s):  
Time Series ◽  
Seawater Intrusion ◽  
Tidal Cycle ◽  
Preferential Flow ◽  
Groundwater Resources ◽  
Time Frame ◽  
Real Field ◽  
Major Influence ◽  
Fresh Groundwater ◽  
Mixing Behaviour

<p>With over 65 % of the global population currently living in areas near a coast, increasing fresh groundwater demands within these areas, shifted precipitation patterns, and rising mean sea levels, increased seawater intrusion into coastal aquifers has become a major issue for groundwater resources in many coastal countries all around the world. Although there are many past studies researching the saline interface in affected aquifers from a modelling, laboratory or field perspective with different hydrological and geophysical approaches, little is known about real field dynamics over various time spans and in different geological settings. This PhD project aims at detecting and characterising seawater intrusion into a shallow coastal Holocene sand and gravel aquifer at New Zealand's west coast with respect to seasonally changing aquifer resistivity and hydrochemical tracers, as well as investigating resistivity and hydraulic property changes within a tidal time frame. Seawater mixing behaviour over different time spans was monitored with electrical resistivity tomography (ERT) over the course of two years, and additional hydrochemical sampling was carried out during the second year of the long-term seawater intrusion monitoring study. During two consecutive years, repeat ERT measurements were able to determine seasonal and shorter-term cycles in seawater mixing behaviour within the shallow coastal aquifer. There are strong indications that increasing urbanisation has a major influence on seasonal seawater intrusion patterns, and the dominant processes at the field locations were identified to be tied to the amount of freshwater available over the course of a year, as well as enhanced evapotranspiration / evaporation during summer. Hydrochemical data backed these observations and were also able to characterise seawater intrusion as a function of depth at the field location. Within the smaller tidal cycle investigations, similarly behaving parts of the aquifer could be identified from resistivity ratios and time series analyses. Varying amplitudes in resistivity changes led to the conclusion that saline mixing within a diurnal tidal cycle is strongly dependent on the recharge regime of the aquifer and decreases significantly for times during the year when recharge is continuous as opposed to times with little general recharge but intense, isolated rainfall events. In addition, tidal time series were used to qualitatively infer hydraulic properties of the aquifer and ultimately delineate preferential flow paths for seawater intrusion at the field site. The results of this project support findings of previous modelling, laboratory and short-term field studies, and put the concepts into a much broader time frame. For the first time the dynamics of seawater mixing in a shallow coastal sand aquifer were conclusively studied at the same location and within different time frames, and are thus of great value for sustainable groundwater management in the area of investigation and similar coastal environments.</p>

scholarly journals Management of Seawater Intrusion in Coastal Aquifers: A Review

Water ◽  
2019 ◽  
Vol 11 (12) ◽  
pp. 2467 ◽  
Author(s):  
Mohammed S. Hussain ◽  
Hany F. Abd-Elhamid ◽  
Akbar A. Javadi ◽  
Mohsen M. Sherif
Keyword(s):  
Seawater Intrusion ◽  
Coastal Aquifers ◽  
Arid Regions ◽  
Saline Water ◽  
Groundwater Resources ◽  
Management Strategies ◽  
Environmental Costs ◽  
Fresh Groundwater ◽  
Advantages And Disadvantages ◽  
And Control

Seawater intrusion (SWI) is one of the most challenging and widespread environmental problems that threaten the quality and sustainability of fresh groundwater resources in coastal aquifers. The excessive pumping of groundwater, associated with the lack of natural recharge, has exacerbated the SWI problem in arid and semi-arid regions. Therefore, appropriate management strategies should be implemented in coastal aquifers to control the impacts of SWI problems, considering acceptable limits of economic and environmental costs. The management of coastal aquifers involves the identification of an acceptable ultimate landward extent of the saline water body and the calculation of the amount of seaward discharge of freshwater that is necessary to keep the saline–freshwater interface in a seacoast position. This paper presents a comprehensive review of available hydraulic and physical management strategies that can be used to reduce and control SWI in coastal aquifers. Advantages and disadvantages of the different approaches are presented and discussed.

scholarly journals Modeling Seawater Intrusion to Coastal Aquifers in South Coast of Laizhou Bay, China

2018 ◽  
Vol 54 ◽  
pp. 00004
Author(s):  
Yawen Chang ◽  
Bill X. Hu ◽  
Xue Li
Keyword(s):  
Seawater Intrusion ◽  
Coastal Aquifers ◽  
Saline Water ◽  
Groundwater Resources ◽  
Water Area ◽  
Laizhou Bay ◽  
Precipitation Condition ◽  
Fresh Groundwater ◽  
Depression Cone ◽  
Error Method

In this study, a two-dimensional SEAWAT 2000 model is developed to simulate the seawater intrusion to coastal aquifers and brine water/fresh water interaction in the south of Laizhou Bay, Shandong Province, China and forecast the seawater intrusion and brine water/freshwater interface development in the coming years. The model profile is perpendicular to the coastal line, about 40 km long and 110 m in depth, and consists of two interfaces, freshwater-saline water interface and brine water-saline water-seawater interface. The parameters of aquifers in the SEAWAT-2000 model are calibrated by trial-error method repeatedly to fit the head and salinity measurements. Based on the historical groundwater and brine water exploration and natural precipitation condition, the prediction results indicate that equivalent freshwater head in shallow freshwater-saline water area will decrease year by year and decline 2.0 m in the forecasting period, caused by groundwater over-pumping for irrigating farmlands. The groundwater head in the brine-saline water area will also decrease about 1.8 m in forecasting period. A larger depression cone appears in the brine area, with smaller funnels in other areas. The salinity in the brine area finally drops below 105g/l. In the meanwhile, the salinity increases in other areas, damage fresh groundwater resources.

Groundwater and salinization risk: tapping works and management experience in the Mediterranean Area

2021 ◽  
Author(s):  
Giorgio De Giorgio ◽  
Livia Emanuela Zuffianò ◽  
Maurizio Polemio
Keyword(s):  
Seawater Intrusion ◽  
Coastal Aquifers ◽  
Groundwater Resources ◽  
Regional Scale ◽  
Mediterranean Area ◽  
Management Approach ◽  
Fresh Groundwater ◽  
Groundwater Exploitation ◽  
Saline Groundwater ◽  
The Mediterranean

&lt;p&gt;The progressive population growth in coastal areas constitutes a huge worldwide problem, particularly relevant for coastal aquifers of the Mediterranean basin.&lt;/p&gt;&lt;p&gt;The increasing use of groundwater and the effect of seawater intrusion makes the study of coastal aquifers extremely relevant.&lt;/p&gt;&lt;p&gt;There are various measures, practices, and actions throughout the world for managing groundwater when this natural resource is subject to salinization risk.&lt;/p&gt;&lt;p&gt;This research focused on the seawater intrusion, classifies the different practical solutions protecting the groundwater through salinization mitigation and/or groundwater salinity improvements along the Mediterranean Area.&lt;/p&gt;&lt;p&gt;The literature review was based on 300 papers, which are mainly international journal articles (76%). The rest includes conference papers (11.8%), reports and theses (7%), and books or chapters of a book (25%).&lt;/p&gt;&lt;p&gt;Three main schematic groundwater management approaches can be distinguished for the use of groundwater resources at risk of salinization.&lt;/p&gt;&lt;p&gt;The &lt;strong&gt;engineering approaches&lt;/strong&gt; pursue locally the discharge increase avoiding or controlling the salinity increase.&lt;/p&gt;&lt;p&gt;The most recent experiences of tapping submarine springs were realized using underground concrete dams, tools shaped like a parachute or tulip, or a fiberglass telescopic tube-bell, especially in the case of karstic aquifers.&lt;/p&gt;&lt;p&gt;The current widespread form of the engineering approach is to address the issue of groundwater exploitation by wells.&lt;/p&gt;&lt;p&gt;More complex solutions use subhorizontal designs. Subhorizontal tapping schemes were realized using tunneling and/or boring in combination with wide-diameter wells or shafts.&lt;/p&gt;&lt;p&gt;These works include horizontal drains or radial tunnels bored inside the saturated aquifer, shafts excavated down to the sea level with radial galleries or drains realized together with weirs to improve the regulation of the discharge rate and of salinization. Application of these solutions in areas where a thin fresh groundwater lens floats on the saline groundwater, as in the case of narrow and highly permeable islands, can yield high discharges, thus causing a very low drawdown over very wide areas. These solutions were successfully applied in Malta Islands.&lt;/p&gt;&lt;p&gt;The &lt;strong&gt;discharge management approach&lt;/strong&gt; encompasses at least an entire coastal aquifer and defines rules concerning groundwater utilization and well discharge.&lt;/p&gt;&lt;p&gt;A multi-methodological approach based on monitoring networks, spatiotemporal analysis of groundwater quality changes, and multiparameter well logging is described in Apulian karstic coastal aquifers (Italy). The core is the definition of the salinity threshold value between pure fresh groundwater and saline groundwater mixture. The basic tools were defined to be simple and cost-effective to be applicable to the widest range of situations.&lt;/p&gt;&lt;p&gt;The &lt;strong&gt;water and land management approach&lt;/strong&gt; should be applied on a regional scale. The main choice for this approach is pursuing water-saving measures and water demand adaptation. A multiple-users and multiple-resources-water supply system model was implemented to evaluate the effectiveness of the increasing maximum capacity of the surface reservoir and managed aquifer recharge in Apulia, a semi-arid region of Southern Italy.&lt;/p&gt;

Construct Validity

2017 ◽  
Author(s):  
Richard McCleary ◽  
David McDowall ◽  
Bradley J. Bartos
Keyword(s):  
Time Series ◽  
Construct Validity ◽  
Hypothesis Test ◽  
Secondary Data ◽  
Time Frame ◽  
Primary Data ◽  
Optimal Time ◽  
Intervention Model ◽  
Right Hand ◽  
The Right

Chapter 8 focuses on threats to construct validity arising from the left-hand side time series and the right-hand side intervention model. Construct validity is limited to questions of whether an observed effect can be generalized to alternative cause and effect measures. The “talking out” self-injurious behavior time series, shown in Chapter 5, are examples of primary data. Researchers often have no choice but to use secondary data that were collected by third parties for purposes unrelated to any hypothesis test. Even in those less-than-ideal instances, however, an optimal time series can be constructed by limiting the time frame and otherwise paying attention to regime changes. Threats to construct validity that arise from the right-hand side intervention model, such as fuzzy or unclear onset and responses, are controlled by paying close attention to the underlying theory. Even a minimal theory should specify the onset and duration of an impact.

scholarly journals Distributed Scatterer InSAR Reveals Surface Motion of the Ancient Chaoshan Residence Cluster in the Lianjiang Plain, China

2019 ◽  
Vol 11 (2) ◽  
pp. 166 ◽  
Author(s):  
Yuzhou Liu ◽  
Peifeng Ma ◽  
Hui Lin ◽  
Weixi Wang ◽  
Guoqiang Shi
Keyword(s):  
Time Series ◽  
Deformation Rate ◽  
First Generation ◽  
Groundwater Resources ◽  
Potential Threat ◽  
Groundwater Exploitation ◽  
Surface Motion ◽  
Elastic Rebound ◽  
Surface Patterns ◽  
Change Dynamic

The Lianjiang Plain in China and ancient villages distributed within the plain are under the potential threat of surface motion change, but no effective monitoring strategy currently exists. Distributed Scatterer InSAR (DSInSAR) provides a new high-resolution method for the precise detection of surface motion change. In contrast to the first-generation of time-series InSAR methodology, the distributed scatterer-based method focuses both on pointwise targets with high phase stability and distributed targets with moderate coherence, the latter of which is more suitable for the comprehensive environment of the Lianjiang Plain. In this paper, we present the first study of surface motion change detection in the Lianjiang Plain, China. Two data stacks, including 54 and 29 images from Sentinel-1A adjacent orbits, are used to retrieve time-series surface motion changes for the Lianjiang Plain from 2015 to 2018. The consistency of measurement has been cross-validated between adjacent orbit results with a statistically significant determination coefficient of 0.92. The temporal evolution of representative measuring points indicates three subzones with varied surface patterns: Eastern Puning (Zone A) in a slight elastic rebound phase with a moderate deformation rate (0–40 mm/yr), Chaonan (Zone B) in a substantial subsidence phase with a strong deformation rate (−140–0 mm/yr), and Chaoyang (Zone C) in a homogeneous and stable situation (−10–10 mm/yr). The spatial distribution of these zones suggests a combined change dynamic and a strong concordance of factors impacting surface motion change. Human activities, especially groundwater exploitation, dominate the subsidence pattern, and natural conditions act as a supplementary inducement by providing a hazard-prone environment. The qualitative and quantitative analysis of spatial and temporal details in this study provides a basis for systematic surface motion monitoring, cultural heritage protection and groundwater resources management.

scholarly journals The influence of the lunar nodal cycle on Arctic climate

2006 ◽  
Vol 63 (3) ◽  
pp. 401-420 ◽  
Author(s):  
Harald Yndestad
Keyword(s):  
Time Series ◽  
Signal To Noise Ratio ◽  
Phase Relationship ◽  
Harmonic Spectrum ◽  
Arctic Climate ◽  
The Arctic ◽  
Major Influence ◽  
Sea Temperature ◽  
Arctic Ice

Abstract The Arctic Ocean is a substantial energy sink for the northern hemisphere. Fluctuations in its energy budget will have a major influence on the Arctic climate. The paper presents an analysis of the time-series for the polar position, the extent of Arctic ice, sea level at Hammerfest, Kola section sea temperature, Røst winter air temperature, and the NAO winter index as a way to identify a source of dominant cycles. The investigation uses wavelet transformation to identify the period and the phase in these Arctic time-series. System dynamics are identified by studying the phase relationship between the dominant cycles in all time-series. A harmonic spectrum from the 18.6-year lunar nodal cycle in the Arctic time-series has been identified. The cycles in this harmonic spectrum have a stationary period, but not stationary amplitude and phase. A sub-harmonic cycle of about 74 years may introduce a phase reversal of the 18.6-year cycle. The signal-to-noise ratio between the lunar nodal spectrum and other sources changes from 1.6 to 3.2. A lunar nodal cycle in all time-series indicates that there is a forced Arctic oscillating system controlled by the pull of gravity from the moon, a system that influences long-term fluctuations in the extent of Arctic ice. The phase relation between the identified cycles indicates a possible chain of events from lunar nodal gravity cycles, to long-term tides, polar motions, Arctic ice extent, the NAO winter index, weather, and climate.

scholarly journals Investigation of correlation of the variations in land subsidence (detected by continuous GPS measurements) and methodological data in the surrounding areas of Lake Urmia

2012 ◽  
Vol 19 (6) ◽  
pp. 675-683 ◽  
Author(s):  
K. Moghtased-Azar ◽  
A. Mirzaei ◽  
H. R. Nankali ◽  
F. Tavakoli
Keyword(s):  
Time Series ◽  
Land Subsidence ◽  
Salt Lake ◽  
Linear Trend ◽  
Groundwater Resources ◽  
Time Interval ◽  
Gps Measurements ◽  
Lake Urmia ◽  
North West ◽  
Continuous Gps

Abstract. Lake Urmia, a salt lake in the north-west of Iran, plays a valuable role in the environment, wildlife and economy of Iran and the region, but now faces great challenges for survival. The Lake is in immediate and great danger and is rapidly going to become barren desert. As a result, the increasing demands upon groundwater resources due to expanding metropolitan and agricultural areas are a serious challenge in the surrounding regions of Lake Urmia. The continuous GPS measurements around the lake illustrate significant subsidence rate between 2005 and 2009. The objective of this study was to detect and specify the non-linear correlation of land subsidence and temperature activities in the region from 2005 to 2009. For this purpose, the cross wavelet transform (XWT) was carried out between the two types of time series, namely vertical components of GPS measurements and daily temperature time series. The significant common patterns are illustrated in the high period bands from 180–218 days band (~6–7 months) from September 2007 to February 2009. Consequently, the satellite altimetry data confirmed that the maximum rate of linear trend of water variation in the lake from 2005 to 2009, is associated with time interval from September 2007 to February 2009. This event was detected by XWT as a critical interval to be holding the strong correlation between the land subsidence phenomena and surface temperature. Eventually the analysis can be used for modeling and prediction purposes and probably stave off the damage from subsidence phenomena.

Fresh groundwater resources and their use in emergencies

2015 ◽  
Vol 42 (4) ◽  
pp. 405-419 ◽  
Author(s):  
I. S. Zektser ◽  
O. A. Karimova ◽  
A. V. Chetverikova
Keyword(s):  
Groundwater Resources ◽  
Fresh Groundwater
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