Townley, L.R., and Wilson, J.L. (1984), CERT Documentation and Users' Manual, Open-file report at the New Mexico Institute of Mining and Technology, Hydrology Program, Socorro NM, 276 pp.

CERT is a computer code for groundwater flow modelling and parameter estimation which includes a methodology for unCERTainty propagation. CERT is primarily intended to aid with the characterisation of regional groundwater systems and the assessment of their waste isolation performance. To assist in the characterisation of a groundwater system, data collection programs can be focused on those parameters identified by CERT to have the largest influence on system performance. Model parameter estimation is accomplished through the systematic comparison of computed and observed piezometric heads, expedited by adjusting the most sensitive parameters in a realistic manner. Most importantly for waste isolation applications, CERT enables the uncertainty in predicted piezometric heads due to uncertainty in model parameters to be objectively determined and used in an assessment of waste isolation performance uncertainty.

CERT can perform classical numerical simulation of steady-state or transient groundwater flow, sophisticated parameter estimation using statistical tests of observed parameters and piezometric heads, and prediction of piezometric head uncertainty. Prior estimates of parameters are obtained through kriging and other statistical means, while a generalised weighted least squares method is used to estimate parameters from observations of head in the so called "inverse problem". First order second moment methods are used to propagate uncertainties in the piezometric heads as a function of the uncertainties in the parameters.