Parameter uncertainties in groundwater modelling - A study on the effect of calibration method on parameter uncertainties in an inverse stochastic groundwater model
Typ
Examensarbete för masterexamen
Program
Infrastructure and environmental engineering (MPIEE), MSc
Publicerad
2020
Författare
Berling, Vilhelm
Strömberg, Jonas
Modellbyggare
Tidskriftstitel
ISSN
Volymtitel
Utgivare
Sammanfattning
Numerical models can be used to forecast the effects of underground constructions
on groundwater conditions. Such forecasts always includes uncertainties, with values
of used parameters being one common source of uncertainty. This study aims
to assess how these parameter uncertainties and the resulting model outcome uncertainty
are affected by either calibrating an inverse stochastic groundwater model
against historic mean head observations or against a disturbance of the hydrogeological
conditions. Two sections of the planned train tunnel Västlänken through
Gothenburg are used as case studies to evaluate the effect that calibration method
has on uncertainties. The first modelled section, Linné service tunnel uses historical
mean head observations for the first case of calibration and leakage to the partially
constructed tunnel with the effect on groundwater levels for the second calibration
case. The other modelled section, Korsvägen, uses the same type of observations for
the first calibration case, while the second case uses the effects of a pumping test.
It was seen that the model over Linné service tunnel resulted in larger uncertainties
for calibration case two compared to case one, while the model over Korsvägen resulted
in less uncertainties for calibration case two compared to case one. This study
shows that calibration method effects uncertainties deriving from used parameters
and that more observations does not always mean less uncertainty.
Beskrivning
Ämne/nyckelord
Stochastic groundwater modelling , GMS MODFLOW , inverse calibration , parameter uncertainty , PEST , Null Space Monte Carlo