Publisher Correction: Groundwater Throughflow and Seawater Intrusion in High Quality Coastal Aquifers

Costall, Alex; Harris, Brett; Teo, B.; Schaa, Ralf; Wagner, F.; Pigois, Jon-Philippe

doi:10.1038/s41598-020-75736-9

Cited by 3 publications

(4 citation statements)

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“…Anisotropy also appeared to have a minor effect on phosphate transport than peat soil heterogeneity (Wang et al, 2020). The anisotropic angle was shown to be highly significant for determining the landward extent of seawater in a high hydraulic conductivity homogenous aquifer (Costall et al, 2020). However, such saltwater wedge has not been observed at the study site neither in drillings nor in our simulations.…”

Section: Other Factorsmentioning

confidence: 60%

Submarine Groundwater Discharge From Non-Tidal Coastal Peatlands Along the Baltic Sea

et al. 2021

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Submarine groundwater discharge (SGD) is an important pathway for water and materials within the land-ocean transition zone that can impact coastal environments and marine life. Although research from sandy shorelines has rapidly advanced in recent years, there is very little understanding of coastal areas characterized by a low hydraulic conductivity, such as carbon-rich coastal peatlands. The objective of this study was to determine the magnitude and location of terrestrial SGD to be expected from a non-tidal low-lying coastal peatland located along the Baltic Sea and to understand the controlling factors using numerical modeling. We employed the HYDRUS-2D modeling package to simulate water movement under steady-state conditions in a transect that extends from the dune dike-separated rewetted fen to the shallow sea. Soil physical properties, hydraulic gradients, geological stratifications, and topography were varied to depict the range of properties encountered in coastal peatlands. Our results show that terrestrial SGD occurs at the study site at a flux of 0.080 m2 d−1, with seepage rates of 1.05 cm d−1 (upper discharge region) and 0.16 cm d−1 (lower discharge region above submerged peat layer). These calculated seepage rates compare to observations from other wetland environments and SGD sites in the Baltic Sea. The groundwater originates mainly from the dune dike—recharged by precipitation and infiltration from ponded peatland surface water—and to a lesser extent from the sand aquifer. The scenario simulations yielded a range of potential SGD fluxes of 0.008–0.293 m2 d−1. They revealed that the location of terrestrial SGD is determined by the barrier function of the peat layer extending under the sea. However, it has little impact on volume flux as most SGD occurs near the shoreline. Magnitude of SGD is mainly driven by hydraulic gradient and the hydraulic conductivity of peat and beach/dune sands. Anisotropy in the horizontal direction, aquifer and peat thickness, and peatland elevation have little impacts on SGD. We conclude that SGD is most probable from coastal peatlands with high water levels, large Ks and/or a dune dike or belt, which could be an essential source for carbon and other materials via the SGD pathway.

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Section: Other Factorsmentioning

confidence: 60%

Submarine Groundwater Discharge From Non-Tidal Coastal Peatlands Along the Baltic Sea

et al. 2021

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“…This allows a direct estimate of the freshwater discharge to the coast to be made, based on either field observations of the toe length, as in Costall et al (2020), or design constraints. As illustrated in Figure 13, the approximation is an improvement over both the Dupuit solution and the solution of Verruijt.…”

Section: Tablementioning

confidence: 99%

“…Field sites subject to waves, tides, and variable freshwater discharge consistently indicate more extensive mixing zones. Despite the high level of uncertainty in the results of predictive models of coupled variable-density flow and solute transport, numerical modeling of flow in coastal aquifers is common (Costall et al, 2020;Langevin, 2003;Sanford & Pope, 2010).Analytical solutions to seawater intrusion problems are often based on the approximation of an interface separating two immiscible fluids. These solutions neglect the mixing zone between the freshwater and seawater, and are therefore in good agreement with laboratory experiments.…”

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confidence: 99%

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Analytical Solutions for Confined and Unconfined Coastal Interface Flow by the Hodograph Method

Anderson¹

2021

Water Resources Research

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We present an analytical solution describing steady, two‐dimensional groundwater flow in the vertical plane in an unconfined, coastal aquifer of finite depth. An interface separates flowing freshwater from stagnant seawater. The boundary conditions along both the phreatic surface and the interface are treated exactly by the use of the hodograph method and conformal mapping. Explicit expressions for the distance of the toe from the coast, and the distance of the tip from the coast, are presented as asymptotic expansions about small gradients valid for isotropic and vertically anisotropic aquifers. A new, and simpler form of the solution to the classical problem of confined interface flow is obtained as a limiting case of the unconfined solution. Both new solutions avoid the problem of crowding, which occurs in the existing solutions for confined interface flow, and is commonly encountered in conformal mappings of elongated domains. A comparison of the tip and toe locations is made for the unconfined and confined cases; the results compare favorably for typical values of seawater density. The exact equation for the toe length as a function of the gradient, truncated after two terms, provides a simple, accurate, and invertible expression for estimating the freshwater discharge to the coast based on field observations of the toe length.

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Spatial variation and drivers of vegetation structure and composition in coastal freshwater wetlands of subtropical Australia

Grieger

Capon

Hadwen

et al. 2021

Mar. Freshwater Res.

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Coastal freshwater wetlands (CFWs) are among the most understudied wetlands globally and are highly vulnerable to projected climate changes. To address CFW knowledge gaps in south-east Queensland, Australia, we surveyed the floristic composition and structure of wooded CFWs and explored variation in vegetation patterns in relation to selected environmental drivers. Understorey and shrub assemblages were surveyed using a cover-class scale and stem counts for tree species abundance. Vegetation structure attributes (stem density, basal area) were calculated from survey data. Redundancy analysis was used to investigate drivers of vegetation structure and the species composition of each stratum. Vegetation structure patterns were associated with gradients of rainfall, soil moisture, salinity and pH. Understorey species composition was associated with wallum wetland species, native perennial grass and herb species, and vegetation patterns of the canopy. Common CFW species, namely Melaleuca quinquenervia and Eucalyptus tereticornis, dominated tree assemblage variation. Overall, CFW vegetation exhibited strong associations with gradients of salinity, rainfall, groundwater dependence and disturbance. Alterations to key drivers of vegetation pattern with future climate changes are likely to markedly influence the composition, structure and function of CFW vegetation communities. Action is therefore required to maintain CFW vegetation communities and ecological function in these diverse and unique wetland systems.

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Publisher Correction: Groundwater Throughflow and Seawater Intrusion in High Quality Coastal Aquifers

Abstract: An amendment to this paper has been published and can be accessed via a link at the top of the paper.

Cited by 3 publications

References 0 publications

Submarine Groundwater Discharge From Non-Tidal Coastal Peatlands Along the Baltic Sea

Submarine Groundwater Discharge From Non-Tidal Coastal Peatlands Along the Baltic Sea

Analytical Solutions for Confined and Unconfined Coastal Interface Flow by the Hodograph Method

Spatial variation and drivers of vegetation structure and composition in coastal freshwater wetlands of subtropical Australia

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