Influence of Tide‐Induced Unstable Flow on Seawater Intrusion and Submarine Groundwater Discharge

Fang, Yunhai; Zheng, Tianyuan; Zheng, Xilai; Yang, Huiyu; Wang, Huan; Walther, Marc

doi:10.1029/2020wr029038

Cited by 43 publications

(30 citation statements)

References 47 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…For example, Q f efflux in the seasonal case with a tidal amplitude of 1.85 cm exhibited high-frequency fluctuations within the intervals of 109-142 min and 752-971 min (unstable stage). Just as previous studies suggested (Fang et al, 2021;Greskowiak, 2014;Röper et al, 2015), the Q f efflux fluctuated over time under the unstable regime, which was also observed in the fixed case (unstable USP) with a tidal amplitude of 2.2 cm and inland freshwater input of 0.271 m 3 /d/m. Fixed cases presented an increased fluctuation amplitude of the Q f efflux over time as the tidal amplitude increased or the inland freshwater input decreased.…”

Section: Variations In Fluxes Across the Aquifer-sea Interface Under ...supporting

confidence: 72%

“…In other words, tide‐induced unstable flow is a natural phenomenon in coastal aquifers. Under the unstable USP situation, the extent of SWI, total SGD, and its components would vary obviously over time, which is significantly different from those observed under a stable situation (Fang et al., 2021; Greskowiak, 2014; Röper et al., 2015).…”

Section: Introductionmentioning

confidence: 79%

See 1 more Smart Citation

Influence of Dynamically Stable‐Unstable Flow on Seawater Intrusion and Submarine Groundwater Discharge Over Tidal and Seasonal Cycles

et al. 2022

Self Cite

View full text Add to dashboard Cite

Temporal changes in the external forcing conditions of coastal aquifer systems, such as seasonal inland freshwater input, may disturb the balance between the ocean forces and freshwater hydraulic gradient. An increase or decrease in this imbalance may affect the stability of tide‐induced upper saline plume (USP). In this study, we performed laboratory experiments and numerical simulations to investigate the influence of seasonal inland freshwater input on USP stability and the associated behavior of seawater intrusion (SWI) and submarine groundwater discharge (SGD). In contrast to previous studies, we found that USP was not always stable or unstable in the intertidal zone, but experienced a dynamically stable‐unstable process as the seasonal inland freshwater input varied. The extent of SWI and SGD showed a dual response to the seasonal inland freshwater input. On one hand, seasonal fluctuation in inland freshwater input directly induced responsive changes in SWI and SGD; on the other hand, dynamic stability of the USP caused by the seasonal fluctuation resulted in an additional high‐frequency fluctuation in the extent of SWI and SGD during the unstable flow. Moreover, the response of saline SGD and total SGD to the seasonal fluctuation in the inland freshwater input was nonlinear. This overall increased the SGD compared to the scenarios with a temporally constant inland freshwater input. Therefore, ignoring seasonal changes in the inland freshwater input may underestimate the amount of water exchanges across the aquifer‐sea interface.

show abstract

Section: Variations In Fluxes Across the Aquifer-sea Interface Under ...supporting

confidence: 72%

Section: Introductionmentioning

confidence: 79%

Influence of Dynamically Stable‐Unstable Flow on Seawater Intrusion and Submarine Groundwater Discharge Over Tidal and Seasonal Cycles

et al. 2022

Self Cite

View full text Add to dashboard Cite

show abstract

“…The most common practice in such studies is to run a steady‐state simulation of the studied area, with the model parameters adapted to match the modeled steady state to the observed average state of the aquifer. The output of the calibrated steady‐state model is applied as initial conditions for transient simulations (which may or may not include cyclical processes), which are used to constrain the dominant factors that control the hydrologic functioning of a given system (Fang et al., 2021; Levanon et al., 2016; Oz et al., 2015; Paldor et al., 2019). Transient simulations are also used to assess vulnerability to various environmental changes (e.g., sea‐level rise, recharge intensification), and to predict future trends in the hydrologic regime (Guimond & Michael, 2021; Masterson et al., 2014; Paldor & Michael, 2021; Xiao et al., 2018).…”

Section: Discussionmentioning

confidence: 99%

Dynamic Steady State in Coastal Aquifers Is Driven by Multi‐Scale Cyclical Processes, Controlled by Aquifer Storativity

Paldor

Frederiks

Michael

2022

Geophysical Research Letters

View full text Add to dashboard Cite

Coastal aquifers supply freshwater to nearly half the global population, yet they are threatened by salinization. Salinities are typically estimated assuming steady‐state, neglecting the effect of cyclical forcings on average salinity distributions. Here, numerical modeling is used to test this assumption. Multi‐scale fluctuations in sea level (SL) are simulated, from tides to glacial cycles. Results show that high‐frequency fluctuations alter average salinities compared with the steady‐state distribution produced by average SL. Low‐frequency forcing generates discrepancies between present‐day salinities estimated with and without considering the cyclical forcing due to overshoot effects. This implies that salinities in coastal aquifers may be erroneously estimated when assuming steady‐state conditions, since present distributions are likely part of a dynamic steady state that includes forcing on multiple timescales. Further, typically neglected aquifer storage characteristics can strongly control average salinity distributions. This has important implications for managing vulnerable coastal groundwater resources and for calibration of hydrogeological models.

show abstract

“…Laboratory experiments of Fang et al. (2021) and Röper et al. (2015) captured the salt finger movement in the intertidal region.…”

Section: Introductionmentioning

confidence: 99%

Transformation in the Stability of Tide‐Induced Upper Saline Plume Driven by Transient External Forcing

Fang

Zheng

Guo

et al. 2022

Water Resources Research

Self Cite

View full text Add to dashboard Cite

The fluctuation in sea level induced by tides generates an upper saline plume (USP) in the intertidal region, which is closely related to groundwater flow and solute transport processes in coastal aquifers. Thus, a clearer understanding of the USP configuration is needed to accurately predict the extent of seawater intrusion and water chemical fluxes to the ocean. This study experimentally and numerically examined the effect of transient external forcing conditions on the stability of tide‐induced USP, represented as seasonal subsurface inflow. In contrast to earlier studies, the USP was not always stable or unstable, but experienced a dynamic transformation of stability‐instability as the seasonal subsurface inflow fluctuated. The same intensity of subsurface inflow caused a stable USP in the fixed cases but a dynamic USP state in the seasonal cases. The USP responded rapidly to the fluctuation of seasonal subsurface inflow and was drawn to expand into the intertidal zone. These features of the USP contributed to the increased potential for the onset of an unstable flow when the subsurface inflow varied seasonally. Therefore, ignoring the timescale changes on external forcing conditions may underestimate the generation of unstable USPs. The frequency contrast between seasonal subsurface inflow and tide also influenced the dynamic transformation process occurring in the intertidal region. There was an inverse relationship between the frequency contrast and the duration of the unstable flow. These findings provide a new understanding of the complex intertidal environment in coastal aquifers.

show abstract

Influence of Tide‐Induced Unstable Flow on Seawater Intrusion and Submarine Groundwater Discharge

Cited by 43 publications

References 47 publications

Influence of Dynamically Stable‐Unstable Flow on Seawater Intrusion and Submarine Groundwater Discharge Over Tidal and Seasonal Cycles

Influence of Dynamically Stable‐Unstable Flow on Seawater Intrusion and Submarine Groundwater Discharge Over Tidal and Seasonal Cycles

Dynamic Steady State in Coastal Aquifers Is Driven by Multi‐Scale Cyclical Processes, Controlled by Aquifer Storativity

Transformation in the Stability of Tide‐Induced Upper Saline Plume Driven by Transient External Forcing

Contact Info

Product

Resources

About