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

CONCLUSIONS
other compounds of interest, e.g. pesticides and PAHs, should also be included. Work
should be undertaken to calibrate the continuous conductivity measurements taken at
Water Orton gauging station for comparison with surface-water quality.
A survey with relatively short sample spacing (50-100m) using a removable drive-point
piezometer, pump and low volume flow cell could be undertaken to measure conductivity
and pH in the riverbed to identify ‘hot spots’ for detailed sampling. Geostatistics could be
performed to obtain the optimum sample spacing required to intercept the major plumes
and obtain an improved estimate of the groundwater geochemical flux to the river.
Further attempts should be made to quantify the contribution from other sources such as
the sewage treatment works to the surface water geochemical flux. Long-term monitoring
for chlorinated solvents and heavy metals could be undertaken using semi-permeable
membrane devices on the riverbed.
2. Tracer experiments could be performed within the riverbed to determine rates of
groundwater discharge. A surface water tracer test of known mass should be combined
with surface-water sampling to determine the dilution (groundwater inflow) and increase
in mass flux for individual determinants along the reach. This method would go some way
to removing the ‘noise’ introduced by the daily variations in sewage works discharges.
The survey could incorporate not only stations on the river bank but also a mobile boat
unit with fluorimeter, data-logger and GPS which could follow the tracer plume down
river, repeatedly traversing and sampling it.
357