Significance of hydraulic head gradients within horizontal wells in unconfined aquifers of limited saturated thickness

Rushton, K. R.; Brassington, F. C.

doi:10.1016/j.jhydrol.2013.04.006

Cited by 14 publications

(4 citation statements)

References 18 publications

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“…For the analytical calculation of saltwater upconing due to pumping by a horizontal well with a finite extent, it was assumed that the frictional head losses (Rushton and Brassington ) within the horizontal well are negligible. In case the head losses are significant, however, the inflow along the horizontal well varies significantly.…”

Section: Discussionmentioning

confidence: 99%

Saltwater Upconing Due to Cyclic Pumping by Horizontal Wells in Freshwater Lenses

et al. 2015

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This article deals with the quantification of saltwater upconing below horizontal wells in freshwater lenses using analytical solutions as a computationally fast alternative to numerical simulations. Comparisons between analytical calculations and numerical simulations are presented regarding three aspects: (1) cyclic pumping; (2) dispersion; and (3) finite horizontal wells in a finite domain (a freshwater lens). Various hydrogeological conditions and pumping regimes within a dry half year are considered. The results show that the influence of elastic and phreatic storage (which are not taken into account in the analytical solutions) on the upconing of the interface is minimal. Furthermore, the analytical calculations based on the interface approach compare well with numerical simulations as long as the dimensionless interface upconing is below 1/3, which is in line with previous studies on steady pumping. Superimposing an analytical solution for mixing by dispersion below the well over an analytical solution based on the interface approach is appropriate in case the vertical flow velocity around the interface is nearly constant but should not be used for estimating the salinity of the pumped groundwater. The analytical calculations of interface upconing below a finite horizontal well compare well with the numerical simulations in case the distance between the horizontal well and the initial interface does not vary significantly along the well and in case the natural fluctuation of the freshwater lens is small. In order to maintain a low level of salinity in the well during a dry half year, the dimensionless analytically calculated interface upconing should stay below 0.25.

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Section: Discussionmentioning

confidence: 99%

Saltwater Upconing Due to Cyclic Pumping by Horizontal Wells in Freshwater Lenses

et al. 2015

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“…They concluded that the well can be used for sustainable water supply at the study site. In addition, Rushton and Brassington (2013a) extended Mohamad and Rushton (2006) study by enhancing the Darcy-Weisbach formula to describe frictional head lose inside a horizontal well. The spatial distributions of predicted flux along the well revealed that the flux at the pumping end is 4 times the magnitude of that at the far end.…”

Section: C-s Huang Et Al: Approximate Analysis Of Three-dimensionamentioning

confidence: 95%

Approximate analysis of three-dimensional groundwater flow toward a radial collector well in a finite-extent unconfined aquifer

Huang

Chen

Yeh

2016

Hydrol. Earth Syst. Sci.

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Abstract. This study develops a three-dimensional (3-D) mathematical model for describing transient hydraulic head distributions due to pumping at a radial collector well (RCW) in a rectangular confined or unconfined aquifer bounded by two parallel streams and no-flow boundaries. The streams with low-permeability streambeds fully penetrate the aquifer. The governing equation with a point-sink term is employed. A first-order free surface equation delineating the water table decline induced by the well is considered. Robin boundary conditions are adopted to describe fluxes across the streambeds. The head solution for the point sink is derived by applying the methods of finite integral transform and Laplace transform. The head solution for a RCW is obtained by integrating the point-sink solution along the laterals of the RCW and then dividing the integration result by the sum of lateral lengths. On the basis of Darcy's law and head distributions along the streams, the solution for the stream depletion rate (SDR) can also be developed. With the aid of the head and SDR solutions, the sensitivity analysis can then be performed to explore the response of the hydraulic head to the change in a specific parameter such as the horizontal and vertical hydraulic conductivities, streambed permeability, specific storage, specific yield, lateral length, and well depth. Spatial head distributions subject to the anisotropy of aquifer hydraulic conductivities are analyzed. A quantitative criterion is provided to identify whether groundwater flow at a specific region is 3-D or 2-D without the vertical component. In addition, another criterion is also given to allow for the neglect of vertical flow effect on SDR. Conventional 2-D flow models can be used to provide accurate head and SDR predictions if satisfying these two criteria.

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“…A finite difference approximation to the groundwater flow equation is used. Insights can be gained from other regional groundwater studies such as a coastal aquifer in Sarawak, (Mohamed and Rushton, 2006), an aquifer system in Norfolk, England where the deepening of drainage ditches has led to the ingress of saline water (Simpson et al, 2011) and an aquifer of limited saturated thickness in north-west England (Rushton and Brassington (2013). Important features of this computational model are summarised in Appendix A.1(d).…”

Section: Estimation Of Rechargementioning

confidence: 99%

Sustainable yields from large diameter wells in shallow weathered aquifers

Rushton

Silva

2016

Journal of Hydrology

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Significance of hydraulic head gradients within horizontal wells in unconfined aquifers of limited saturated thickness

Cited by 14 publications

References 18 publications

Saltwater Upconing Due to Cyclic Pumping by Horizontal Wells in Freshwater Lenses

Saltwater Upconing Due to Cyclic Pumping by Horizontal Wells in Freshwater Lenses

Approximate analysis of three-dimensional groundwater flow toward a radial collector well in a finite-extent unconfined aquifer

Sustainable yields from large diameter wells in shallow weathered aquifers

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