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

ABSTRACT
A field-based research study has been undertaken on the River Tame within the industrial city
of Birmingham, UK, to understand better the influence of urban groundwater discharge on
surface-water quality. The 8 km study reach receives ~6% of its total baseflow (60% of which
is groundwater) from the underlying Triassic Sandstone aquifer and flood-plain sediments. An
integrated set of surface water and groundwater flow, head and physical/chemical data was
collected from installed riverbed piezometers and existing monitoring across the aquifer. Field
data and supporting computer modelling indicated the convergence of groundwater flows
from the sandstone/drift deposits and variable discharge to the river (0.06 to 10.7 m 3 d -1 m -1 ,
mean 3.6 m 3 d -1 m -1 ), much of which occurred through the riverbanks. Significant
heterogeneity was also observed in groundwater quality along and across the river channel.
Key contaminants detected were copper, nickel, sulphate, nitrate, chlorinated solvents, e.g.
trichloroethene, and their biodegradation products. Groundwater contaminant concentrations
were generally lower than expected and ascribed to dilution and natural attenuation within the
aquifer and riverbed. High concentration plumes were detected, but their effect was localised
due to substantial dilution within the overlying water column of the river. Estimated
contaminant fluxes were not found to reduce significantly the present surface water quality,
which is poor (>30% is pipe-end discharge). Comparative studies elsewhere and further
elucidation of heterogeneity and natural attenuation controls are recommended.