DETERMINING THE RANGE OF PREDICTIONS OF A GROUNDWATER MODEL WHICH ARISES FROM ALTERNATIVE CALIBRATIONS

A major element in constructing a groundwater model is choosing the pa rameter values. The traditional approach is to aim for a single best s et of values. The parameters used in a model are effective rather than measureable, and this combined with the inherent uncertainties in the modeling process means that there are often many plausible sets of va lues. A single prediction obtained from a single set of parameter valu es is not appropriate, but rather the range in predictions from the al ternative calibrations should be used. A method is presented for findi ng the best case and worst case predictions among the plausible parame ter sets and is applied to a real case study. Widely different feasibl e parameter sets were found giving significantly different predictions .