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

STUDY SETTING
water quality throughout the unconfined aquifer with the exception of two boreholes cased to
a depth of >135 m. In all surveys the abstraction regime of the sampled well was found to be a
major influence on temporal quality variations. Intermittent pumping was found to take high
proportions of shallow water. Evidence was also found of migration of contaminants down
the side of borehole casing. Rises in groundwater have led to a reduction in the unsaturated
zone increasing the vulnerability of the groundwater. Closure of industry and reduction of
abstraction mean migration of contaminant plumes off site is now more likely to occur.
Of the 28 inorganic determinands measured from 70 abstraction wells (Ford et al.,1994) only
nitrate and barium regularly approached the European Community drinking water standards.
However, localised areas showing high levels of groundwater contamination, including heavy
metals, were observed. The principal organic contaminants detected in the groundwater are
chlorinated solvents (Rivett, 1989) which could be directly related to metal work degreasing
or dry cleaning industries. Little correlation was found between the distributions of organic
and inorganic contaminants, probably reflecting differences in physical transport
processes,chemical interactions and histories of chemical usage. The worst case of inorganic
pollution was found in west Birmingham and the worst case of organic contamination was
within the Tame Valley. The extent of microbiological contamination within the Birmingham
Aquifer is unknown but a study of shallow groundwater in the Triassic Sandstone beneath
Nottingham has revealed the widespread occurrence of bacteria and bacteriophage marker
species related to leakage from sewers.
Temporal variations in groundwater quality have been investigated by Ford et al., (1994),
Rivett, (1989) and Taylor and Rivett, (1999). Contaminant travel times to the water table have
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