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

WATER QUALITY INTERACTIONS
errors in the pH measurements may have influenced the results. The deep uncontaminated
borehole beneath the city centre had a saturation index of –0.8 and a pH of 7.38. These values
represent a downward temporal trend, being lower than the results obtained by previous
workers (Table 7.4). An upward trend in EC was seen from 290 μScm to 356 μScm between
1988 and 2001. This may indicate increased contamination at depth but the results from the
other determinands do not support this conclusively.
The results of shallow groundwater sampling showed general saturation with respect to
calcite, with an average HCO3 - content of 294 mgl -1 . The piezometers were in general situated
on, or adjacent to, open land and would be expected to receive considerable recharge through
the soil zone with a high ppCO2 content. The riverbed piezometers showed a mixture of
saturation and undersaturation with respect to calcite and the surface water was saturated with
respect to calcite. The source of the recharge to the abstraction wells is of significance when
considering the active groundwater flow system in the Tame Valley that will ultimately
discharge to the river. The lack of any substantial contribution by old calcite saturated water
(i.e. the undersaturation) at depth (