PEST - Model-Independent Parameter Estimation and Uncertainty Analysis

IWFM Utilities

PEST IWFM Utilities

The PEST IWFM Utilities were contributed by SSP&A Inc and CH2M Hill Technical support is available from

Under contract to the California Department of Water Resources (CA-DWR) five utility programs were developed to support the calibration of the integrated groundwater surface-water model version 2 (IGSM2) simulation code, now referred to as the integrated water flow model (IWFM). Four of these utilities were based upon existing PEST utilities, and a fifth program (REAL2IGSM) was developed specifically for the IGSM2/IWFM simulation programs. The documentation describes the program inputs required, their execution, and the outputs they produce. A flow chart illustrates the sequence of processes that must be completed when using the programs to parameterize and calibrate an IGSM2/IWFM model application. The utilities were developed to be general enough to be applicable to any application of the IGSM2/IWFM simulation program(s). The utilities are written in Fortran and make considerable use of Fortran-90 modules. The source code for each program is contained in a single file for portability, with the extension "F90". The distributed executables were compiled using the Lahey/Fujitsu Fortran 95 Compiler Release 5.50j.

The PEST IWFM utilities were developed to achieve the following objectives:

  • Support the use of the pilot point parameterization scheme for defining parameters in the IWFM (formerly IGSM/IGSM2) model.

  • Compile parameter values calculated on the basis of pilot points, or any other scheme that outputs node-specific parameter values, into a form readable by IWFM.

  • Support the assignment of Tikhonov style regularization between parameters defined on the basis of pilot points.

  • Streamline the post-processing of simulated equivalents to the observations, simplifying file formats and the process required to add or remove observations from the calibration data set.

See this page for further details and downloads.

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