The impact of urban groundwater upon surface water - eTheses ...

GROUNDWATER FLOW MODELLING
on each occasion to the maximum or minimum expected value for the unit. The effect of
reducing the sandstone aquifer thickness to 10 m was also examined.
6.5.4 Application of the analytical model of aquifer thickness
The analytical model provided information on the effective saturated thickness of the aquifer
adjacent to the river. The model incorporated field data representative of groundwater head
values at three locations within the cross section parallel to groundwater flow on the eastern
bank adjacent to profile 8 (Section 5.8). Head conditions were imposed at the eastern
boundary, the river boundary and on the river bank at the site of piezometer P10. The
sensitivity of the model to variations in the head values was examined to see if the
groundwater boundary at the river was equal to river stage alone, or contained an additional
head component i.e. a seepage face. The initial model head conditions were based on mean
(DWF) values for the river stage (90.3 m.a.o.d) and water levels in the piezometers P10
(90.86 m.a.o.d) and BH19 (93.25 m.a.o.d) at distances of 13.27m and 175m respectively
from the river bank.
6.5.5 Results and discussion
The geological controls on groundwater flow to the river may be considered in terms of the
hydraulic conductivity and the spatial distribution (thickness) of each geological unit.
Modelling was used to investigate these controls under horizontal and convergent flow
conditions. The control of specific yield on groundwater – surface water interactions will be
considered in Section 6.10.
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