Evaluation of prediction intervals for expressing uncertainties in groundwater flow model predictions

We tested the accuracy of 95% individual prediction intervals for hydraulic heads, streamflow gains, and effective transmissivities computed by ground water models of two Danish aquifers. To compute the intervals, we assumed t hat each predicted value can be written as the sum of a computed dependent variable and a random error. Testing was accomplished by using a cross-vali dation method and by using new field measurements of hydraulic heads and tr ansmissivities that were not used to develop or calibrate the models. The t ested null hypotheses are that the coverage probability of the prediction i ntervals is not significantly smaller than the assumed probability (95%) an d that each tail probability is not significantly different from the assume d probability (2.5%). In all cases tested, these hypotheses were accepted a t the 5% level of significance. We therefore conclude that for the groundwa ter models of two real aquifers the individual prediction intervals appear to be accurate.