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

CONCLUSIONS
A strong association was observed between land use and the distribution of contaminants
within the groundwater. Specific contaminant plumes were identified in the riverbed
associated with nearby industry or contaminated land e.g. TCE associated with the metal-
working industry. Other contaminants were more diffuse and widespread e.g. chloride from
road salting. A large amount of industry is now, and historically has been, located adjacent to
the river. With a narrow unsaturated zone, often permeable alluvial deposits and short
groundwater flow paths, the river is at greater risk of contaminated groundwater discharge
from these sites than from sites further away on the valley flanks.
Although the estimated contaminant flux from the groundwater to the river is not sufficient to
cause a significant reduction in current surface-water quality, in the long term the
groundwater, as a source of contaminants, does present a significant limiting factor in the
future improvement of surface-water quality. Improvements in pipe-end discharge quality
may be achieved relatively rapidly but improvements in groundwater quality will take
significantly longer. The aquifer will continue to receive significant pollutant loading, via
recharge in the urban environment, and long- term sources such as DNAPL pools are already
known to be present within the aquifer.
The impact of the urban groundwater aquifer is dependent on conditions within the overlying
river system. The Birmingham Aquifer discharges to a river that has risen in an urban
catchment and the groundwater does not significantly alter the surface water quality.
However, if Birmingham were located near the head-waters of a rural catchment, then the
contribution of contaminant flux from the groundwater would be more significant.
352