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

Geological Unit Parameter values (md -1 )
GROUNDWATER FLOW MODELLING
Kx max Kx min Kx cal Kz max Kz min Kz cal
Sandstone 5 0.5 2 1 0.1 0.2
Weathered
Sandstone
5 0.5 3 2 0.1 1
Alluvial gravel 15 0.1 5 5 0.1 0.5
Made ground 20 0.05 1 2 0.005 0.1
Stream bed 15 1 5 10 0.01 0.5
max = maximum realistic value, min = minimum realistic value,
cal = calibrated model value (a single value changed on each run)
Table 6.2 Conductivity values used in the FAT3D model sensitivity analyses.
The vertical conductivity (Kz 0.5 md -1 ) was assigned as 10% of Kx. The value of Kz is low
for gravel but borehole logs indicate the occurrence of discontinuous units of clay which
justify the lower value. Data on the made ground are sparse (4 values) but indicate high
variability with values of conductivity 0.04, 0.03, 10, 20 md -1 ; mean estimates of Kx 1 md -1
,Kz 0.1 md -1 were used. A vertical conductivity for the riverbed sediments Kz 1 md -1 was
assigned, based on the results of falling head tests but subsequently reduced during the
calibration process.
6.5.3.2 Sensitivity analyses
The sensitivity of total groundwater discharge to variations in conductivity was carried out on
the calibrated model under transient conditions. The conductivity of a single unit was changed
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