2. The significance of groundwater tidal fluctuations

White, J.; Roberts, T. O. L.

doi:10.1680/gpiua.19744.0004

Cited by 44 publications

(20 citation statements)

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“…Confined aquifers may exhibit low attenuation with fluctuations potentially extending one hundred meters or more from the open water. Unconfined aquifers are heavily damped, and very often, significant fluctuations are unlikely to extend to more than 20-30 m from open water (White and Roberts 1994).…”

Section: The Ocean Tide Effectmentioning

confidence: 99%

Processes Influencing Groundwater Level and the Freshwater-Saltwater Interface in a Coastal Aquifer

Vallejos

Sola

Pulido−Bosch

2014

Water Resour Manage

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Few studies have focused on the relationship between the various causes of groundwater level fluctuations and the seawater intrusion process, due to the complexity of this relationship, being the aim of this paper. Piezometric fluctuations in coastal aquifers are determined by a number of processes and their characterization depends on the complexity of the aquifer stratigraphy, as well as many other hydrodynamic factors. The precipitation regime, tides, wave setup and storm surges, as well as atmospheric pressure are the most relevant of these processes. By means of a series of observations made at an experimental site in south-eastern Spain, this study demonstrates the complexity of water table fluctuations in coastal zones. The study employed two piezometers situated very close to the shoreline, excavated in detritic deposits with highly variable hydraulic conductivity (semi-confined aquifer). Continuous measurements were taken of hydraulic head, tide height, electrical conductivity and water temperature. The study concludes that precipitation has the greatest effect on piezometric level, followed by atmospheric pressure and wave action, while the semi-diurnal and fortnightly tidal cycles caused variations of smaller amplitude in the piezometric logs. All these oscillations affect the position of the fresh water-seawater interface. The attenuation of the tidal amplitude observed at the two monitoring points was lower than the value calculated using analytical solutions, and this is due to the semi-confined nature of the aquifer. The calculated tidal efficiency is around 0.4-0.5, giving a t lag of about 3 h, with a 10-15 min delay between monitoring boreholes, P-II and PI. We also identified that the response of water conductivity and temperature to tidal cycles is not synchronized with the variations in the piezometric level influenced by tidal fluctuations.

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Section: The Ocean Tide Effectmentioning

confidence: 99%

Processes Influencing Groundwater Level and the Freshwater-Saltwater Interface in a Coastal Aquifer

Vallejos

Sola

Pulido−Bosch

2014

Water Resour Manage

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“…In a coastal aquifer system, there is usually an unconfined aquifer above one or more confined aquifers [White and Roberts, 1994;Chen and Jiao, 1998]. The pressure waves in unconfined aquifers tend to be damped because the storage coefficient is usually several orders of magnitude larger than the confined storage coefficient that governs pressure changes at Copyright 1999 by the American Geophysical Union.…”

Section: Introductionmentioning

confidence: 99%

An analytical solution of groundwater response to tidal fluctuation in a leaky confined aquifer

Jiao¹,

Tang²

1999

Water Resources Research

182

235

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Abstract. An analytical solution is derived to investigate the influence of leakage on tidal response in a coastal leaky confined aquifer system. The analytical solution developed here is more general than the traditional solution obtained by Ferris [1951], which can be regarded as a special case of the solution presented in this paper. This solution is based on a conceptual model under the assumption that the groundwater level in the confined aquifer fluctuates in response to sea tide while that of the overlying unconfined aquifer remains constant. This conceptual model is supported by numerous field studies by previous researchers which have demonstrated that the tidal response in an unconfined aquifer may be negligible compared to that in a confined aquifer. The leakage has a significant impact on the tidal behavior of the confined aquifer. Hypothetical studies indicate that both tidal amplitude of groundwater head in the aquifer and the distance over which the aquifer can be disturbed by the sea tide will be considerably reduced because of the existence of leakage. This analytical solution is used to investigate the tidal and piezometer data at the Chek Lap Kok airport, Hong Kong Special Administrative Region, People's Republic of China. IntroductionIn most coastal areas, groundwater and seawater are in con- While the tidal fluctuation in an unconfined aquifer may be negligible compared to that in a confined aquifer, the unconfined aquifer may influence the tidal fluctuation in the underlying confined aquifer via leakage. To the authors' knowledge, there has not been any research to address this issue. In this paper an attempt will be made to develop an analytical solution to investigate the influence of leakage on tidal response in a coastal leaky confined aquifer system. This solution will then be used to discuss the impact of leakage on the tidal behavior of the confined aquifer. The tidal and piezometer data at the Chek Lap Kok (CLK) airport, Hong Kong Special Administrative Region, People's Republic of China are used as a case study.

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“…Many researches revealed that the head fluctuation in the unconfined aquifer due to tides is significantly damped by its storage (e.g., Millham and Howes, 1995;Chen and Jiao, 1999). White and Roberts (1994) indicated that the farthest distance that tidal propagation can reach, defined as the intrusion distance, is usually not over Several previous researches indicated that the effect of the leakage on the groundwater in coastal leaky aquifer systems is significant. Jiao and Tang (1999) developed an analytical solution for describing the head fluctuation in coastal confined aquifers, where the aquitard infinitely extends from the coastal line to the inland.…”

Section: Introductionmentioning

confidence: 99%

Groundwater fluctuations in heterogeneous coastal leaky aquifer systems

Chuang

Huang

et al. 2010

Hydrol. Earth Syst. Sci.

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Abstract. In the past, the coastal leaky aquifer system, including two aquifers and an aquitard between them, was commonly assumed to be homogeneous and of infinite extent in the horizontal direction. The leaky aquifer system may however be heterogeneous and of finite extent due to variations in depositional and post depositional processes. In this paper, the leaky aquifer system is divided into several horizontal regions for the heterogeneous aquitard and underlying aquifer. A one-dimensional analytical model is developed for describing the head fluctuation in such a heterogeneous leaky aquifer system. The hydraulic head of the upper unconfined aquifer is assumed constant. It is found that both the length and location of the discontinuous aquitards presented in the coastal area have significant effects on the amplitude and phase shift of the head fluctuation in the lower aquifer. In addition, the influence of the formation heterogeneity on the spatial head distribution is also investigated.

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2. The significance of groundwater tidal fluctuations

Cited by 44 publications

References 0 publications

Processes Influencing Groundwater Level and the Freshwater-Saltwater Interface in a Coastal Aquifer

Processes Influencing Groundwater Level and the Freshwater-Saltwater Interface in a Coastal Aquifer

An analytical solution of groundwater response to tidal fluctuation in a leaky confined aquifer

Groundwater fluctuations in heterogeneous coastal leaky aquifer systems

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