Using PEST with MODFLOW-2000

Why would you want to use PEST to calibrate a groundwater model now that MODFLOW-2000 is available? Here are a few reasons:

• If you want to calibrate MODFLOW jointly with another model such as MT3D;

• If you want to link certain sets of parameters together so that their values vary in harmony throughout the parameter estimation process;

• If you want to use one of PEST's advanced modes of operation not available in MODFLOW-2000 - i.e. "regularization" or "predictive analysis" mode;

• If you want to introduce flexibility into the parameterization process through the use of pilot points;

• If your parameterization case is difficult and you wish to use advanced PEST functionality such as user-intervention, and PEST's ability to enforce hard upper and lower parameter bounds;

• If the MODFLOW-2000 parameter estimation process does not converge and you would like to try PEST's robust parameter estimation engine in any of its three modes of operation (i.e. "parameter estimation", "predictive analysis" and "regularization" modes).

A special version of MODFLOW-2000, modified for optimal use with PEST, is available; this is known as "MODFLOW-ASP". A MODFLOW2000-to-PEST translator is supplied with it. Using this translator, an input dataset for MODFLOW-2000's parameter estimation process can be converted to a MODFLOW/PEST input dataset virtually instantaneously. Thus using PEST's advanced parameter estimation functionality instead of MODFLOW's parameter estimation process is as easy as it can be. Documentation is included.

Download MODFLOW-ASP

A suite of utility software has been written to expedite the use of PEST in the MODFLOW/MT3DMS context. This is also downloadable, free of charge.