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

River level data
GROUNDWATER FLOW MODELLING
Steady state river level data are representative of typical dry weather flow conditions recorded
from a stilling well at Profile 8 between 22/5/01 and 31/5/01. Transient river stage data were
collected from the stilling well at 5 minute intervals during a river flood event on the 6/3/01
and 7/3/01.
6.4.3.4 Model Calibration
The objective of the model is to simulate the groundwater flow system at profile 8 and its
interaction with the surface water. The model uses the available geological, piezometric and
river discharge data from Profile 8. However, there is considerable heterogeneitity within the
geology of the system at this location, with the possibility of multiple aquifer units. Also,
limited data exists on the aquifer properties. Alternative combinations of aquifer properties
could achieve calibration of the model, making the benefit of exact calibration limited. The
model was first examined under steady state conditions to select a suitable model upon which
to perform transient calibration.
Calibration of the steady state model is based on the net groundwater discharge to the river
and the squared error in hydraulic head (headmodel-headobserved) 2 for the riverbank and
multilevel river bed piezometers. River discharge measurements indicate groundwater inputs
to the river of between 2 and 4 m 3 d -1 per unit length of channel and the MODFLOW model
estimated groundwater inputs of 3 to 5 m 3 d -1 per unit length of channel. A variation of +/- 5
cm was deemed acceptable for the riverbank piezometers. The riverbed piezometers were
considered of secondary importance in the calibration as they represent a single time point
and also have an increased likelihood of survey error. A total of 0.05 cm 2 for the sum of
173