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

GROUNDWATER FLOW MODELLING
the model to take account of the presence of a seepage face and river lengths greater than the
cell width. The river stage is well constrained by surveyed data for riverbed elevations and
dry weather river levels.
6.3.2.3 Model Calibration
The model was constructed to reflect the style of the real system and to illustrate some of the
important features of groundwater flow across the flood plain. As the model is simplistic and
significantly constrained by the boundary conditions it was thought to be of little benefit to
apply stringent calibration criteria.
The calibration of the model was carried out on a trial and error basis by altering conductivity,
riverbed conductance, and recharge. The primary target was to achieve the groundwater
discharge along the 3.8 km model reach that was consistent with field data. Baseflow analyses
of 1999 gauging station data (Section 6.3.2) suggest a range in groundwater discharge to the
river of 11 MLd -1 to 25 MLd -1 for the model. Dry weather flow gauging undertaken on
23/5/01 within the specific model reach, estimates a groundwater discharge of 8 MLd -1 to 16
MLd -1 , depending on which estimate of industrial and tributary discharges is used. The flow-
gauging estimate lies within the range of values from the baseflow analyses, and is specific to
the model reach rather than an average over 23.8 km as calculated from the gauging station
data. Therefore, the model calibration criteria for groundwater discharge to the river were set
as > 8 MLd -1 and