Effects of vadose zone on groundwater table fluctuations in unconfined aquifers

Kong, Jun; Xin, Pei; Ge, Hua; Luo, Zhaoyang; Shen, Chengji; Chen, Dan; Li, Ling

doi:10.1016/j.jhydrol.2015.06.045

Cited by 59 publications

(39 citation statements)

References 48 publications

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“…However, data indicate that dual signal interference does not occur at our study site as the tidal signal is rapidly damped in the unconfined aquifer with increasing distance from the north and south shorelines (i.e., W06 and W37, Figure ). While surface water features and complex land topography can also cause nonuniform tidal propagation (Kong et al, ), these factors do not explain the isolated nature of the tide‐induced water table fluctuations observed in Areas 1 and 2. Rather, data indicate that fluctuations in Areas 1 and 2 may be due to leakage of the tidal pressure signal from an underlying confined aquifer (Jeng et al, ).…”

Section: Resultsmentioning

confidence: 99%

Analysis of Tide and Offshore Storm‐Induced Water Table Fluctuations for Structural Characterization of a Coastal Island Aquifer

Trglavcnik

Morrow

Weber

et al. 2018

Water Resources Research

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Analysis of water table fluctuations can provide important insight into the hydraulic properties and structure of a coastal aquifer system including the connectivity between the aquifer and ocean. This study presents an improved approach for characterizing a permeable heterogeneous coastal aquifer system through analysis of the propagation of the tidal signal, as well as offshore storm pulse signals through a coastal aquifer. Offshore storms produce high wave activity, but are not necessarily linked to significant onshore precipitation. In this study, we focused on offshore storm events during which no onshore precipitation occurred. Extensive groundwater level data collected on a sand barrier island (Sable Island, NS, Canada) show nonuniform discontinuous propagation of the tide and offshore storm pulse signals through the aquifer with isolated inland areas showing enhanced response to both oceanic forcing signals. Propagation analysis suggests that isolated inland water table fluctuations may be caused by localized leakage from a confined aquifer that is connected to the ocean offshore but within the wave setup zone. Two‐dimensional groundwater flow simulations were conducted to test the leaky confined‐unconfined aquifer conceptualization and to identify the effect of key parameters on tidal signal propagation in leaky confined‐unconfined coastal aquifers. This study illustrates that analysis of offshore storm signal propagation, in addition to tidal signal propagation, provides a valuable and low resource approach for large‐scale characterization of permeable heterogeneous coastal aquifers. Such an approach is needed for the effective management of coastal environments where water resources are threatened by human activities and the changing climate.

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Section: Resultsmentioning

confidence: 99%

Analysis of Tide and Offshore Storm‐Induced Water Table Fluctuations for Structural Characterization of a Coastal Island Aquifer

Trglavcnik

Morrow

Weber

et al. 2018

Water Resources Research

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“…It should be noted that in the work of Kong et al . (, ) parameters α and β were assigned the same value. Nevertheless, in the present paper, we assigned values to these parameters separately to examine their individual effects on wave motion.…”

Section: Theorymentioning

confidence: 99%

“…Although the revised models proposed by Kong et al . (, ) showed better precision compared with traditional Boussinesq models when applied in simulating the wave or tidal induced groundwater wave, the coefficients adopted in the revised models often deviate much away from the actual ones. Some studies have attributed such discrepancy to hysteresis effect, which results in moisture asymmetry during the alternative drying and wetting processes (Stauffer and Kinzelbach, ; Cartwright, ; Shoushtari et al ., ).…”

Section: Introductionmentioning

confidence: 98%

“…Furthermore, Kong et al . () proposed a revised Boussinesq equation subjected to long‐period boundary oscillations by considering the influence of unsaturated flow on non‐hydrostatic pressure in saturated zone. Both equations considered the vertical water exchange between saturated and unsaturated zones.…”

Section: Introductionmentioning

confidence: 99%

“…In order to investigate the hysteresis effect on groundwater wave propagation, we further evaluated the work of Kong et al . (, ) and proposed an alternative Boussinesq equation based on the improved Gardner's soil‐water retention function. This paper is organized as follows: in Section ‘Theory’ the governing equation for groundwater flow is described, and a unified Boussinesq equation is proposed; in Section ‘Analytical Solution’, the analytical solution for the unified equation is derived, and parametric analysis is conducted to reveal the hysteresis influence on groundwater wave motion; final conclusions are drawn in Section ‘Concluding Remarks’.…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

An alternative Boussinesq equation considering the effect of hysteresis on coastal groundwater waves

Kong

Luo

Shen

et al. 2016

Hydrological Processes

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Abstract:This paper presents an alternative Boussinesq equation considering hysteresis effect via a third-order derivative term. By introducing an improved moisture-pressure retention function, this equation describes, with reasonable precision, groundwater propagation in coastal aquifers subject to Dirichlet boundary condition of different oscillation frequencies. Test results confirmed that it is necessary to consider horizontal and vertical flows in unsaturated zone, because of their variable influences on hysteresis. Hysteresis in unsaturated zone can affect the water table wave number of groundwater wave motion, such as wave damping rate and phase lag. Oscillations with different periods exert different hysteresis effect on wave propagation. Truncation/shrinkage of unsaturated zones also affects the strength of hysteresis. These impacts can be reflected in the alternative Boussinesq equation by adjusting the parameter representing the variation rate of moisture associated with pressure change, as opposed to traditional computationally expensive hysteresis algorithms. The present Boussinesq equation is simple to use and can provide feasible basis for future coupling of groundwater and surface water models.

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Improvement of the hillslope‐storage Boussinesq model by considering lateral flow in the unsaturated zone

Kong

Shen

Luo

et al. 2016

Water Resources Research

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Unsaturated flow is an important factor that affects groundwater motion. Among various drainage models, the nonlinear Hillslope-storage Boussinesq (HSB) model has been commonly used to predict water flux along a slope. In this study, we improved this model by considering lateral flow in the unsaturated zone. Using modified van Genuchten functions, we analytically expressed the concept of equivalent propagation thickness in the vadose zone. This analytical expression was then incorporated into the HSB model to reflect two different stages of the drainage process and to simulate the hillslope drainage process more accurately. The model results indicated that lateral flow has significant effects in the unsaturated zone during the hillslope drainage process. Even in sandy aquifers, the amount of water contributed by the unsaturated zone is a key factor that enables a decrease in the water table during the middle and late stages of the process. A comparison between the measured and simulated results based on both convergent-type and divergent-type hillslope drainage processes revealed that the thickness of the saturated zone decreases as the unsaturated flow increases. This study emphasizes the necessity of considering unsaturated flow in the HSB model to improve the accuracy of predicting groundwater outflow rates and develop more accurate hydrographs. The concept of equivalent propagation thickness also provides a criterion for assessing the importance of unsaturated lateral flow for future drainage research.

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Effects of vadose zone on groundwater table fluctuations in unconfined aquifers

Cited by 59 publications

References 48 publications

Analysis of Tide and Offshore Storm‐Induced Water Table Fluctuations for Structural Characterization of a Coastal Island Aquifer

Analysis of Tide and Offshore Storm‐Induced Water Table Fluctuations for Structural Characterization of a Coastal Island Aquifer

An alternative Boussinesq equation considering the effect of hysteresis on coastal groundwater waves

Improvement of the hillslope‐storage Boussinesq model by considering lateral flow in the unsaturated zone

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