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

REVIEW
The median groundwater contribution was estimated as 56% of the total nitrate load under
baseflow. Harvey et al. (1998) examined the effect of enhanced maganese oxidation (and co-
precipitation of trace metals) in the hyporheic zone on basin-scale geochemical mass balance
in a drainage basin contaminated by copper mining.
2.3 UK Case Studies
Published data on groundwater quality and flow interactions in the UK are generally limited.
A few of the key studies are briefly presented.
A study of trace-element concentrations in the major rivers entering the Humber estuary
showed elevated levels in the rivers draining industrial urban catchments (Neal et al., 1996).
The relationship between concentration and flow was used to evaluate the sources of trace
elements; a negative relationship to flow implied a groundwater source. Within the urban
rivers, most elements in the dissolved phase exhibited negative relationships, indicating that
point-source discharges provided the major source of trace elements. Roberts et al. (1998)
investigated nitrate contamination of groundwater in the Lincolnshire Limestone resulting
from surface water recharge related to local groundwater abstractions.
Of particular concern in the UK has been the widespread detection of pesticides at low levels
within groundwaters and surface waters (Croll, 1991). Clark et al. (1991) investigated
pesticide occurrence in the River Granta and the underlying groundwater within the chalk
aquifer of Cambridgeshire. The maximum levels of pesticide were found in the river during
periods of high flow. However, even under low-flow conditions, levels of pesticide were
persistent and are probably derived from the groundwater. Of particular interest in the study,
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