Simplified modelling of pollutant transport in naturally-layered aquifers : a thesis submitted for the degree of Philosophiæ Doctor (PhD), 2015 February, Institute of Natural & Mathematical Sciences, Massey University
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Date
2015
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Massey University
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Abstract
Chemical species such as tracers or dissolved pollutants fl
ow along with
the slow-moving water as it makes its way through the complex porous
structure of the aquifer; during this process they are dispersed in different
directions. The rate of dispersion depends on the geometric characteristics
of the porous structure and speed of the fl
uid.
Generally, groundwater systems have layered structures determined by different
events in the geological processes that formed them. The layers in
a system have di erent physical properties, and their thicknesses are not
uniform. This naturally layered structure is used here to advantage by
discretizing them into almost horizontal layers, where each may have different
geometrical characteristics such as thickness permeability, dispersivitiy,
porosity, etc. The system of advection-dispersion equations that model the
uid and species transport then have coeffcients that depend mainly on
depth, but with a layer composition that may change with horizontal distance.
The mean dynamic pressure (or mean hydraulic head) may be assumed
constant vertically at each horizontal point if it is not in the vicinity of a
well or where there is very small vertical
ow. In the vicinity of recharge
or pumping wells, the mean dynamic pressures or hydraulic heads for each
sub-layer of the aquifer may be allowed to have different values for each
different sub-layer. Steady-state fl
uid fl
ow is considered in this thesis in
both confined and phreatic (unconfined) aquifers.
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Keywords
Groundwater pollution, Groundwater flow, Mathematical models, Research Subject Categories::INTERDISCIPLINARY RESEARCH AREAS::Water in nature and society