Marine water from mid-Holocene sea level highstand trapped in a coastal aquifer: Evidence from groundwater isotopes, and environmental significance

Lee, Stephen; Currell, Matthew; Cendón, Dioni I.

doi:10.1016/j.scitotenv.2015.12.014

Cited by 42 publications

(15 citation statements)

References 35 publications

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“…We also stress that seawater intrusion is just one of several processes that lead to groundwater salinization. Others include dissolution of evaporite minerals 46 (e.g., halite, gypsum), mixing with naturally occurring brines 47 , infiltration of seawater reaching the land surface by storm surges or tsunamis [48][49][50][51] , mixing with seawaters emplaced during marine high-stands 52 (i.e., when local sea levels were higher than present), infiltration of salts derived from dry and wet deposition of airborne particles 53 , percolation 44% of well water level observations made within 1 km of the coast are below sea level 20% of well water level observations made more than 9 km but <10 km from the coast are below sea level a b Fig. 3 Fraction of well water elevations that are below sea level, as a function of distance from the coastline.…”

Section: Resultsmentioning

confidence: 99%

Groundwater level observations in 250,000 coastal US wells reveal scope of potential seawater intrusion

et al. 2020

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Seawater intrusion into coastal aquifers can increase groundwater salinity beyond potable levels, endangering access to freshwater for millions of people. Seawater intrusion is particularly likely where water tables lie below sea level, but can also arise from groundwater pumping in some coastal aquifers with water tables above sea level. Nevertheless, no nationwide, observation-based assessment of the scope of potential seawater intrusion exists. Here we compile and analyze~250,000 coastal groundwater-level observations made since the year 2000 in the contiguous United States. We show that the majority of observed groundwater levels lie below sea level along more than 15% of the contiguous coastline. We conclude that landward hydraulic gradients characterize a substantial fraction of the East Coast (>18%) and Gulf Coast (>17%), and also parts of the West Coast where groundwater pumping is high. Sea level rise, coastal land subsidence, and increasing water demands will exacerbate the threat of seawater intrusion.

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Section: Resultsmentioning

confidence: 99%

Groundwater level observations in 250,000 coastal US wells reveal scope of potential seawater intrusion

et al. 2020

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“…An almost identical profile was afterwards established, as evidenced by a second measurement on 15 November 2013 (shown in Figure 3(a), alongside with model results that will be discussed later on). During the second sampling, three individual water samples were obtained by low-flow sampling using a Grundfos MP1 pump from three different depths, similar to Lee et al [27]. It is known that coastal zone observation wells with long screens may indicate a higher position of the transition zone than in the aquifer [28,29].…”

Section: Methodsmentioning

confidence: 99%

Behaviour of Tritium and Tritiogenic Helium in Freshwater Lens Groundwater Systems: Insights from Langeoog Island, Germany

et al. 2019

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Tritium (3H) and its daughter product 3He have been widely used as tracers in hydrological studies, but quantitative analyses of their behaviour in freshwater lenses and the transition zone in coastal aquifers are presently lacking. In this paper, the fate of 3H and 3He in the freshwater lens and the transition zone as well as the saltwater wedge is studied using numerical variable-density flow and transport models of different degrees of complexity. The models are based on the conditions on the German island of Langeoog, which is uniquely suited for this purpose because of the high 3H concentration of the North Sea. It is found that most bomb-related tritiogenic 3He still resides in the freshwater lens, making it a useful tracer for young (<60 years) groundwater. Differences in dispersive transport between 3H and 3He can cause an apparent age bias on the order of 10 years. Under favourable conditions, 3H from seawater can penetrate deep into the offshore part of the aquifer and has potential to be used as a tracer to study saltwater circulation patterns. Our modelling suggests that the field-observed 3H in the transition zone does not originate from seawater but from freshwater affected by the bomb peak. Yet in models with a low (αL=0.5 m) dispersivity, no 3H was sequestered into the transition zone and the transition zone width was underestimated. Better results were obtained with αL=5 m, a value that is higher than in comparable modelling studies, which suggests that further work is needed to better understand the controls (tides, lithological heterogeneity, or transience of recharge and pumping) on transition zone mixing processes.

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“…In South Korean groundwater, such enrichment of fluoride was interpreted as the result of dissolution of F-bearing silicate minerals during water-rock interaction [56,[58][59][60]. The enrichments of Na and Cl (and increasing TDS) in some samples from the lower gravel aquifer are possibly due to remnant seawater that was entrapped in the intermediate silty clay layer during the sea level rise, and that has been subsequently washed out during the deposition of recent point-bar sediment [26,61]. Interestingly, the enrichments of dissolved Fe and Mn are observed in many samples from the upper aquifer ( Figure 6).…”

Section: Vertical Change Of Hydrochemistrymentioning

confidence: 99%

Lithologic Control of the Hydrochemistry of a Point-Bar Alluvial Aquifer at the Low Reach of the Nakdong River, South Korea: Implications for the Evaluation of Riverbank Filtration Potential

Moniruzzaman

Lee

Jung

et al. 2018

Water

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To assess the groundwater−river water interaction in a point-bar alluvial aquifer as a crucial step in site assessment for riverbank filtration, hydrochemical and hydrogeologic investigations were performed on a riverine island at the low reach of the Nakdong River, South Korea. The site was evaluated for the application of large-scale bank filtration. Unconsolidated sediments (~40 m thick) of the island comprise fine- to medium-grained sand (upper aquifer), silty sand with clay intercalations, and sandy gravel (lower aquifer) in descending order. The intermediate layer represents an impermeable aquitard and extends below the river bottom. A total of 66 water samples were collected for this study; groundwater (n = 57) was sampled from both preexisting irrigation wells, and three multi-level monitoring wells (each 35 m deep). Groundwater chemistry is highly variable, but it shows a distinct hydrochemical change with depth: shallow groundwater (<25 m deep) from the upper aquifer is characteristically enriched in NO3− and SO42−, due to agricultural contamination from the land surface, while deeper groundwater (>25 m deep) from the lower aquifer is generally free of NO3− and relatively rich in F. The lower aquifer groundwater is also higher in pH, and concentrations of K+, Mg2+, and HCO3−, indicating that the aquifer is likely fed by regional groundwater flow. Such separation of groundwater into two water bodies is the result of the existence of an impermeable layer at intermediate depth. In addition, the hyporheic flow of river water is locally recognized at the upstream part of the upper aquifer as the zone of low TDS (Total Dissolved Solids) values (<200 mg/L). This study shows that the study site does not seem to be promising for large-scale riverbank filtration because 1) the productive, lower aquifer is not directly connected to the bottom of the river channel, and 2) the upper aquifer is severely influenced by agricultural contamination. This study implies that the subsurface hydrogeologic environment should be carefully investigated for site assessment for riverbank filtration, which can be aided by a detailed survey of groundwater chemistry.

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Marine water from mid-Holocene sea level highstand trapped in a coastal aquifer: Evidence from groundwater isotopes, and environmental significance

Cited by 42 publications

References 35 publications

Groundwater level observations in 250,000 coastal US wells reveal scope of potential seawater intrusion

Groundwater level observations in 250,000 coastal US wells reveal scope of potential seawater intrusion

Behaviour of Tritium and Tritiogenic Helium in Freshwater Lens Groundwater Systems: Insights from Langeoog Island, Germany

Lithologic Control of the Hydrochemistry of a Point-Bar Alluvial Aquifer at the Low Reach of the Nakdong River, South Korea: Implications for the Evaluation of Riverbank Filtration Potential

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