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

GROUNDWATER FLUX
CHAPTER 8. ESTIMATION OF GROUNDWATER
FLUX TO THE RIVER TAME
The objective of this chapter is to estimate the dissolved chemical mass loading to the river
from the groundwater discharging across the 7.4 km reach overlying the Birmingham Aquifer.
The methods used included:
i) continuous measurements of electrical conductivity (EC) and discharge to derive
temporal variations in surface water mass flux at Water Orton gauging station which
result from changes in groundwater discharge;
ii) the use of baseflow analyses and mean riverbed sample concentrations to derive an
average mass flux to the river from the groundwater;
iii) combined surface water sampling and discharge measurements to determine the
increase in mass flux within the surface water across the study reach; and
iv) mass flux calculations for some of the individual contaminant plumes identified.
The calculation of mass flux requires measurement of both concentration and discharge. The
marked heterogeneity of the system introduces significant uncertainty to both which is
additive. The determination of groundwater discharge is not trivial. Increases in discharge
along a river may be measured directly by flow gauging but in an urban setting it is difficult
to separate the groundwater component reliably. Discharge may be calculated using hydraulic
conductivity and head measurements taken from piezometers in the riverbed, but these values
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