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

GROUNDWATER FLUX
150 m was used, together with the maximum detected concentrations in the plume, and a
discharge of 1 m 3 d -1 per metre length of channel to calculate the impact on the surface water
(Table 8.6).
Maximum concentration
in the plume (mgl -1 )
Mass flux
(kgd -1 )
Change in surface water
concentration *1
(mgl -1 )
Percentage of mean daily
mass flux to the 7.4 km
study reach *2
Estimate of mass flux from the plume detected in Profile 8
F NO3 SO4 Al Pb Cu Zn Ni
198 233 470 33 0.011 0.097 0.294 0.139
29700 34950 70500 4950 1.65 14.55 44.1 20.85
0.18 0.21 0.42 0.03 0.00001 0.00009 0.0003 0.0001
4.9 2.3 1.2 4.3 1.0 4.9 2.0 1.7
*1 Under typical flow conditions of 166 Mld -1 and a total plume discharge of 260 m 3 d -1 .
*2 Based on mass flux calculated from baseflow analyses and riverbed piezometer samples.
Table 8.6 The estimated contaminant mass flux from the plume identified at Profile 8.
The mass flux to the surface water is significant for both F and Cu, amounting to ~ 5% of the
total mass flux to the study reach. If higher values of discharge are used, such as indicated by
the modelling, then the contribution to the NO3, Al, Zn, Ni surface water loading also
becomes significant. The source of the Cu, Zn, and Ni in this plume may be from the riverbed
sediments themselves where the discharge of acidic groundwater has mobilised the metals
(Section 7.5) and other acidic plumes may cause a similar effect. The F concentration used
was the maximum value from four different sampling events. The concentrations from the
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