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Ground Water. 2016 Jul;54(4):521-31. doi: 10.1111/gwat.12382. Epub 2015 Oct 22.

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

Author information

1
Department of Soil and Groundwater, Deltares, P.O. Box 85467, 3508 AL, Utrecht, The Netherlands.
2
Department of Soil Physics and Land Management, Wageningen University, P.O. Box 47, Wageningen, 6700 AA, The Netherlands.
3
Department of Physical Geography, Utrecht University, 3584 CS, Utrecht, The Netherlands.

Abstract

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.

PMID:
26491946
DOI:
10.1111/gwat.12382
[Indexed for MEDLINE]

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