Determination of aquifer parameters based on measurements of tidal effects on a coastal aquifer near Beihai, China

Abstract

Abstract:Measurements of the tide and groundwater levels in coastal zones are of importance in determining the properties of coastal aquifers. The solution to a one-dimensional unsteady groundwater flow model in a coastal confined aquifer with sinusoidal fluctuation of the tide shows that the tidal efficiency decreases exponentially with distance and the time lag increases linearly with distance from the coast. The aquifer property described by the ratio of storage coefficient to transmissivity is determined if the damping constant of the tidal efficiency or the slope of the time lag with distance are obtained on the basis of tidal measurements. Hourly observations of the tide and groundwater levels at 10 wells on the northern coast near Beihai, China show that with distance from the coast, tidal efficiency decreases roughly exponentially and the time lag increases roughly linearly. The estimated ratio of storage coefficient to transmissivity of the confined aquifer ranges from 1Ð169 ð 10 6 d m 2 to 1Ð83 ð 10 7 d m 2 . For a given transmissivity of 750 m 2 d 1 , the storage coefficient of the aquifer is 8Ð7675 ð 10 4 with the tidal efficiency method and 1Ð3725 ð 10 4 with the time lag method. The damping constant of the tidal efficiency with distance can be defined as the tidal propagation coefficient. The value of the confined aquifer is determined as 0Ð0018892 m 1 .

The Impact of the Degree of Aquifer Confinement and Anisotropy on Tidal Pulse Propagation

“…Previous studies have applied the above simple 1D expressions (Equations 3 and ) to estimate D for coastal aquifers (Schultz and Ruppel ; Zhou ), riverbank aquifers (Trefry and Johnston ), island aquifers (Trefry and Bekele ; Rotzoll and El‐Kadi ), and atoll aquifers (Chattopadhyay et al ). To further constrain T and S (or K and S s ), independent measurements including slug tests and pumping tests are often conducted in conjunction with tidal methods (Erskine ; Millham and Howes ; Trefry and Johnston ).…”

“…These were derived for confined aquifers (Jacob 1950;Ferris 1951;van der Kamp 1972;Song et al 2007;Guo et al 2010), leaky confined aquifers (Jiao and Tang 1999;Jeng et al 2002;Chuang and Yeh 2007;Xia et al 2007;Chuang and Yeh 2008;Sun et al 2008;Chuang et al 2010;Chuang and Yeh 2011), and unconfined aquifers (Li et al 2000;Teo et al 2003;Song et al 2007;Chang et al 2010;Yeh et al 2010). Although multidimensional sophisticated analytical solutions exist for complex aquifers, a simple 1D Jacob-Ferris model assuming a semi-infinite, homogeneous, isotropic, and confined aquifer with a vertical bank submitted to sinusoidal wave variation has been widely used for estimating D (Erskine 1991;Millham and Howes 1995;Trefry and Johnston 1998;Schultz and Ruppel 2002;Jha et al 2003;Trefry and Bekele 2004;Zhou 2008;Rotzoll et al 2013;Zhou et al 2015). The following equations have been modified to calculate diffusivity using either amplitude attenuation method (D AAM ) or time lag method (D TLM ) following the Jacob-Ferris approach:…”

“…where x is the distance from monitoring well to shoreline, h is the diffusive wave amplitude observed at the monitoring well, h 0 is wave amplitude in the river or surface water body, t 0 is wave period, and t L is time lag. Previous studies have applied the above simple 1D expressions (Equations 3 and 4) to estimate D for coastal aquifers (Schultz and Ruppel 2002;Zhou 2008), riverbank aquifers (Trefry and Johnston 1998), island aquifers (Trefry and Bekele 2004;, and atoll aquifers (Chattopadhyay et al 2015). To further constrain T and S (or K and S s ), independent measurements including slug tests and pumping tests are often conducted in conjunction with tidal methods (Erskine 1991;Millham and Howes 1995;Trefry and Johnston 1998).…”

Barometric and tidal-induced aquifer water level fluctuation near the Ariake Sea

“…The governing equation, boundary conditions, and initial equation have been presented in numerous reports of the relevant literature (Jacob 1950;Jiao and Tang 1999;Zhou 2008;Guo et al 2010;Dong et al 2012). Furthermore, the solution which describes aquifer response to tidal variation is…”

Hydrogeological Characterization of Coastal Aquifer on the Basis of Observed Sea Level and Groundwater Level Fluctuations: Neretva Valley Aquifer, Croatia

“…On the basis of two monitoring wells, the study elaborated effects of tidally induced fluctuations 1 km inland from the shoreline. Potential of assessment of transmissivity and storage from time lag and tidal efficiency has been demonstrated for Beihai aquifer in China [32]. In [33], the authors presented a framework to assess the hydraulic diffusivities of both confined and unconfined aquifers.…”