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

CONCLUSIONS
given an insight into monitoring strategies and the problems associated with estimating
contaminant flux to an urban river via the groundwater pathway.
Typically the quality of a river is determined by regular sampling of surface waters at several
widely-spaced points using simple concentration values rather than total mass flux. This
approach is unlikely to identify individual contaminant plumes discharging to the river due to
dilution effects and masking by upstream inputs. The sampling programme along a 7.5 km
section of the River Tame utilising piezometers in the river bed located discharge from
plumes of both organic and inorganic contaminants which were not identified by the detailed
surface-water sampling programme.
The WFD indicates that contaminant concentrations should be measured and regulated before
dilution occurs at the discharge point to the receptor. To assess the total mass of contaminant
flux from the plume to the river requires definition of the spatial extent of the plume,
concentration values and discharge rates. This is time and data intensive and requires
consideration of the temporal variability and the effect of any attenuation processes that may
occur across the groundwater surface water interface.
Current UK water-quality guidelines are generally expressed as maximum concentration
limits related to the possible toxic effects on humans and the wider ecology. However, to
allow effective management of a river system, knowledge of the geochemical mass flux
balance is required, though it is more problematic to obtain.
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