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

STUDY SETTING
this restricts the level of recharge to the bedrock. A geographical information system has been
used by Thomas (2001) to investigate the complex nature of recharge in Birmingham based
on land use and drift geology.
3.6 Hydrochemistry and Contamination of the Birmingham Aquifer
The extended period of urbanisation and industrial activity in the study area has had a
substantial impact on the groundwater quality, with widespread contamination of the shallow
portions of the unconfined aquifer, and local to some boreholes within the confined section.
Despite this, many parts of the aquifer contain water of good quality and sustainable use of
the aquifer for public supply has been investigated (Greswell et al., 2000). Research by
Jackson (1981), Ford (1990) and Rivett (1989) highlighted the distinct variations that occur in
the hydrochemistry of the aquifer between the confined and unconfined sections, and between
shallow and deep waters.
The natural hydrochemistry is a bicarbonate system dominated by dissolution of calcite
cement with high sulphate concentrations in some areas associated with the dissolution of
gypsum in the upper part of the Bromsgrove Sandstone Formation and the Mercia Mudstone
Group. Water from the Kidderminster and Bromsgrove Sandstone Formations is
oversaturated with respect to calcite, but undersaturated in the Wildmoor Formation owing to
the lower content of calcite cement. A 20 m thick zone of decementation reported (Ford et al.,
1992) at the top of the unconfined formations has developed as a result of acidic recharge
water primarily related to industrial pollution. Contributing factors to the acidification include
microbial activity increasing the PCO2 in the shallow groundwater e.g. microbially mediated
oxidation of hydrocarbons, industrial acid spills which may be locally important, and
oxidation of sulphide minerals present within the Quaternary deposits. The majority of the
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