PEST
is considered the most powerful
and robust parameter estimation program available for automating and
improving model calibration in groundwater modeling.
The program works by optimizing
a set of user-defined model parameters in order to minimize
the calibration residuals from a set of user-defined
observations.
PEST is supported by both
Visual MODFLOW and Groundwater
Vistas.
Key Features:
- PEST
combines a robust inversion engine
with the ability to communicate with a model
through the model's own input and output files.
Thus PEST can be used without the
need for any programming.
- To calibrate a model,
simply:
- inform
PEST which numbers to adjust on model input
files
- identify
those numbers on model output files for which
there are corresponding field or laboratory
measurements
- instruct PEST how to run the model
- With
PEST, the
user can:
- calibrate models using
data gathered over noncontiguous time
intervals
- simultaneous
calibrate
- a steady-state and
a transient models
- a flow and a
transport models
- multiple recharge
models together with a flow model
- a flow model
combined with regularization
functionality
- PEST
calculates statistical data for optimized parameter
values including 95% confidence intervals together with
the parameter covariance and correlation-coefficient
matrices
- All
PEST data storage is
dynamically allocated; hence the problem size (including
numbers of adjustable parameters and the size of the
observation dataset) is limited only by the amount of
memory installed on the user’s machine
- PEST
MODFLOW / MT3D utilities are
supported by both Visual MODFLOW and Groundwater
Vistas
- The
MODFLOW/MT3D utilities are a set of programs that
automate construction of PEST interface files for use with
MODFLOW and MT3D. They are designed to facilitate calibration of
MODFLOW against borehole-measured heads and/or drawdowns,
and MT3D against borehole-measured concentrations.
- Adjustable
parameters can include just about anything found on a
MODFLOW or MT3D input file including:
- Tabulated
data such as drain and riverbed conductivity
- Array
based data such as transmissivity, recharge or
dispersivity
- The WinPEST
graphical interface allows the user to visualize and
understand the calibration and predictive analysis with
ease through a series of run-time and post-run displays
PEST Focus Features:
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User-Defined
Parameter Bounds Optimum parameter
values can be constrained to lie between
user-specified upper and lower bounds, thus ensuring
that estimated values are in range.
Prior information
on parameters or on relationships between parameters
can be incorporated into the estimation process.
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Data
Handling Observations and
parameters can be grouped for ease of property
definition and weights allocation, and to add
flexibility to the inversion process.
Individual model
parameters can be designated as adjustable, fixed or
linked to other parameters; adjustable parameters can
be log-transformed to increase optimization
efficiency.
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Predictive
Analysis PEST’s unique
predictive analyzer allows the user to estimate the
true range of predictive nonuniqueness associated with
a calibrated model.
The Predictive
Analyzer allows the modeler to calculate the
uncertainties in model predictions arising from
uncertainties in model parameters while ensuring the
model remains calibrated.
PEST will calculate
the highest or lowest value of a key model outcome
while at the same time ensuring that the parameter
values used to make this prediction are such as to
keep the model calibrated. This allows the user
to test best and worst case scenarios with ease,
design a fail-safe remediation system and/or optimize
the efficiency of a monitoring network.
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WinPEST
Graphical Interface
The WinPest
graphical user interface displays an extensive range
of run-time and post-run data for easy analysis and
post processing.
WinPest creates
several plots to examine parameter uncertainty and
nonuniqueness and analyze calibration residuals
including:
- Parameter values
- Composite
parameter sensitivities
- Objective
function value
- Parameter
correlation coefficient matrix
- Individual
parameter sensitivities from the Jacobian matrix
- Calculated vs.
observed values
- Calibration
residuals
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Intervention PEST allows
user-intervention in the parameter estimation process
whereby troublesome parameters can be held for a while
and the most recent parameter upgrade repeated without
the need for extensive recalculation.
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Model
Independence
PEST takes control
and runs the model as
many times as needed while adjusting
parameter values until the discrepancies between
model outputs and corresponding field or
laboratory measurements are as small as possible
in the weighted least squares sense.
PEST then lists
optimal parameter values, an estimate of the
uncertainty associated with optimal parameter
values, best-fit model outcomes,
model-to-measurement residuals, and numerous statistics related to the optimal parameter and
residual sets.
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Questions?
Write to Support@GroundwaterSoftware.com
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Software Online, LLC
520 Chicopee Row, Groton, MA 01450 USA
Tel: (978) 448-5818 Fax: (978) 772-0595
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