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The modeling environment of PMWIN showing a concentraion plume calculated by MT3D and pathlines and contours generated by PMPATH for Windows. A DXF-background site-map is overlaid on the model grid.

Introducing Processing Modflow for Windows

Processing Modflow for Windows (PMWIN) is a complete simulation system for modeling ground water flow and transport processes with the 3D-finite-difference groundwater model MODFLOW, the particle tracking models PMPATH for Windows or MODPATH, the solute transport model MT3D and the parameter estimation program PEST. PMWIN comes with MODFLOW (executable and source), the powerful PMPATH for Windows, various modeling tools and the educational version of MT3D and PEST - MT3DLITE and PESTLITE. PMWIN is also compatible to the public domain version of MT3D Version DoD_1.5.

Development of a contamination plume during remeadiation. The model is described in the user's manual of MT3D.

Access All Memory

PMWIN is capable of using all available memory. PMWIN can handel models with up to 80 layers and 1000 stress periods, and each model layer can consist of up to 2000 × 2000 cells. The coordinate system can be defined by the user. The model grid can be shifted, rotated, refined and overlaid on up to five DXF-background maps. Model data can be specified for each finite-difference cell individually, in the form of zones, or even automatically interpolated by the Field Interpolator.

Packages Supported

PMWIN supports the simulation of the effects of wells, rivers, drains, head-dependent boundaries, recharge and evapotranspiration. Five additional packages of MODFLOW are supported by PMWIN - HFB1, CHD1and IBS1- for simulating slurry walls and calculating compaction. The supported packages are listed below:

Basis Package(BAS1)
Block-Centered Flow Package 2 (BCF2)
Direct Solution Package (DE45)
Drain Package (DRN1)
Evapotranspiration Package (EVT1)
General-Head Boundary Package (GHB1)
Horizontal-Flow Barrier Package (HFB1)
Interbed-Storage Package (IBS1)
LKMT Package (this package creates interface files to MT3D)
Output Control Options (OC)
Preconditioned Conjugate Gradient Package 2 (PCG2)
Reservoir Package (RES1)
River Package (RIV1)
Recharge Package (RCH1)
Strongly Implicit Procedure Package (SIP1)
Slice-Successive Overrelaxation Package (SOR1)
Streamflow-Routing Package (STR1)
Time-Variant Specified-Head Package (CHD1)
Well Package (WEL1)

MT3D Supported

PMWIN supports the use of MT3D (version 1.x and MT3D96) to simulate changes in concentration of single species miscible contaminants in groundwater considering advection, dispersion and chemical reactions. There are four soluition schemes for the advecton term - the method of characteristics (MOC), the modified method of characteristics (MOC), the hybrid method of characteristics (HMOC) and the pure finite-difference method. In MT3D, the concentration change due to dispersion alone is solved with a fully explicit central finite-difference scheme. Chemical reactions supported by the MT3D transport model include equilibrium-controlled sorption reactions and first-order irreversible rate reactions, such as redioactive decay or biodegradation.

Support PEST for Automatic Calibration

The purpose of PEST (which is an acronym for Parameter ESTimation) is to assist in data interpretation and in model calibration. If there are field or laboratory measurements, PEST can adjust model parameters and/or excitation data in order that the discrepancies between the pertinent model-generated numbers and the corresponding measurements are reduced to a minimum. It does this by taking control of the model (MODFLOW) and running it as many times as is necessary in order to determine this optimal set of parameters and/or excitations. PMWIN helps the user to inform PEST of assigning the adjustable parameters and excitations. PMWIN provides comprehensive supports to PEST. All you have to do is to specify the observation data and define zones of parameters and send them to a Parameter List. It is all accomplished with a few clicks of the mouse.

Powerful Modeling Tools

A New Particle Tracking Model PMPATH included
PMPATH is an advective transport model running independently from PMWIN. PMPATH retrieves the groundwater models created in PMWIN and simulation result files from the flow model MODFLOW. A semi-analytical particle tracking scheme is used to calculate the groundwater paths and travel times. Both forward and backward particle tracking are allowed for steady-state and transient flow simulations. Through the interactive graphical modeling environment of PMPATH, you can place particles and perform particle tracking with just a few mouse clicks. While most available particle tracking models need postprocessors for visualization of computed paths and times data, PMPATH calculates and shows the pathlines and travel time marks simultaneously. Moreover, PMPATH provides various on-screen graphical options including head contours, drawdown contours and velocity vectors for any selected model layer and time step.

Field Interpolator
Numerical ground water models require areally distributed parameters (e.g., hydraulic conductivity or hydraulic heads, etc.) be assigned to each cell in the model domain. Usually, the modeler obtains a parameter distribution in the form of XYZ scattered data points. The field interpolator interpolates the XYZ data to each model cell. The model grid can be irregularly spaced. Four interpolation methods are currently provided, including Kriging, Shepard's Inverse Distance and triangulation methods developed by Akima and Renka.

Digitizer
Using the Digitizer you can digitize, shift or delect points and assign a value to each of these points. You can save or load the points of the current layer in or from an XYZ file. An XYZ file can be accepted by the Field Interpolator.

Graph Viewer
You can display temporal development curves of the measured values as well as simulation results including hydraulic heads, drawdowns, concentration, preconsolidation heads, compaction of a model layer and subsidence of an entire aquifer. Using the simulation results and user-specified observation values, PMWIN can create scatter diagrams, which are often used to present the calibration results. The observed values are plotted on one axis and the calculated values on the other. For exact agreement between measurement and simulation, all points would lie on the 45° line. The narrower the area of scatter around the line, the better is the match.

Head vs. time curve generated by the Graph Viewer


A scatter diagram generated by the Graph Viewer

View your Results with the powerful Result Extractor
This powerful tool allows you to extract results from any stress period, time step and layer and put them into a spread sheet. You can examine the results, create contour plots with PMWIN or save them in ASCII format or even SURFER compatible files. The extractable result files include hydraulic heads, drawdown, cell-by-cell flow terms, preconsolidation head, compaction, subsidence and concentration.

Calculation of Subregional Water Budget
There are situations in which it is useful to calculate flow terms for various subregions of the model. An improved Water Budget Calculator allows you to calculate budget for user-specified zones and the exchange of flows between zones.

Stochastic Modeling

In stochastic modeling, uncertainty due to unknown small-scale distribution of the model parameters is addresses directly by assuming that the parameters are random variables. The Field Generator of PMWIN generates synthetic fields with (lognormally) heterogeneously-distributed transmissivity or hydraulic conductivity and allows you to incorporate effects and influences of unknown small-scale heterogeneities into the groundwater model. This capablity allows you to do stochastic modeling within PMWIN.

Random fields generated and displayed by PMWIN. A mean value of -2.3 and standard deviation 0.5 (both log10 based) were used by the Field Generator. The ratio of correlation length to the field width is 0.1.

Graphics Output

PMWIN provides the WYSIWYG (What You See Is What You Get) capability. It can create contour maps or solid fill plots of input data or simulation results. Solid Fill can utilize the full range of RGB values to fill cells with different colors. It is very useful for displaying concentration plumes or distributions of parameters. Contours can be added to solid fill plots. Velocity vectors and pathlines with time marks can be created by PMPATH for Windows. Report-quality graphics may be saved to a wide variety of file types, including SURFER, DXF, HPGL and BMP (Windows Bitmap). Through the use of DXF files, you can use CAD or graphics software (such as AutoCAD or CorelDraw) to overlay as many plots as you wish.

Elevation distribution and Cross-sections overlaid on a background bitmap.

Extensive Online Help

PMWIN features an online help system and includes a comprehensive 200-page user's guide with a step-by-step tutorial, explanations of all applications and examples, and the underlying theory of all supported packages. The examples include a pumping test application, stochastic modeling, model calibration with PEST, simulation of solute transport and the other practical problems from the STR1, IBS1 and BCF2 packages.