Geoscience Reference
In-Depth Information
Figure 6.9
Predicted local water table levels for five discharges (0.1 to 6.8mm/hr) in the Saeternbekken
MINIFELT catchment, Norway, using global parameters calibrated on catchment discharge and recording
borehole data from October-November 1987 (after Lamb et al., 1997, with kind permission of John Wiley
and Sons).
Figure 6.9 shows the results of local calibration of saturated transmissivity,
T
o
, and effective porosity,
δθ
, parameters for two of the recording boreholes for the 1987 calibration period. The results show a
significant improvement. On the basis that the variation of
T
o
might be much greater than that of the
effective porosity, an apparent
T
o
value was calculated for each piezometer to match the observed and
predicted water table elevations at each point for each of the five available data sets (points showing
significant ponding were excluded). A similar approach to adjusting local transmissivities has also been
used by Jordan (1994) and Seibert
et al.
(1997). In this case, it was found that the adjustment necessary
was positively correlated with the topographic index, implying higher apparent transmissivities at higher
index values. The correlations were stronger for the composite model with coefficients varying from
