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Groundwater Modeling with GMS - Groundwater Modeling System - sophisticated groundwater modeling environment for MODFLOW, MODPATH, MT3D, FEMWATER, SEEP2D, SEAM3D, RT3D, PEST, UCODE, and UTCHEM Groundwater Modeling with GMS (Groundwater Modeling System) |
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What's New in GMS 4.0 (Groundwater Modeling System) PEST in GMS (Groundwater Modeling System) GMS (Groundwater Modeling System) supports PEST. PEST is a general purpose parameter estimation utility developed by John Doherty of Watermark Computing. The PEST interface in GMS can be used to perform parameter estimation for MODFLOW. The parameter zones can be assigned directly to the cells or by using GIS feature objects in the conceptual model. A unique feature of the GMS PEST interface is that it supports both head and flux observations. PEST is a model-independent interface that allows modelers to calibrate their own, tailor-made "composite models," built through assimilating one or more models and appropriate preprocessing and postprocessing software into a single batch file. Enormous creativity can be exercised in the construction and calibration of these models. UCODE in GMS (Groundwater Modeling System) UCODE is a general purpose parameter estimation utility developed by the Colorado School of Mines and the USGS. The UCODE interface in GMS can be used to perform automated parameter estimation for MODFLOW. MODFLOW 96 in GMS (Groundwater Modeling System) GMS v4.0 supports the MODFLOW2000. While this version has no major differences from MODFLOW 88, it does have a few minor differences. The most significant difference is that it supports a free-field format for all MODFLOW input files. MODFLOW 88 only allowed ten spaces in the input files for each floating point value including the plus or minus sign, all characters in the exponent for numbers written using scientific notation. This restriction often results in a loss of significant figures. GMS v3.1 writes all floating point values to the MODFLOW 96 input files using double precision (15 significant figures). Another advantage of MODFLOW 96 is that the text output file contains more information than the previous version. MODFLOW 96 will be distributed freely with GMS 4.0. It has been modified slightly to support the GMS super file and parameter estimation with PEST/UCODE. Fill Cells in GMS (Groundwater Modeling System) Solids - MODFLOW in GMS - Groundwater Modeling System Solids - MESH in GMS (Groundwater Modeling System) 2D Interpolation Options GMS (Groundwater Modeling System) 3D Interpolation Options GMS (Groundwater Modeling System) Log Contouring GMS (Groundwater Modeling System) Color Palettes GMS (Groundwater Modeling System) MT3DMS GMS (Groundwater Modeling System) Mass Loading in GMS (Groundwater Modeling System) When performing transport simulations, it often becomes necessary to simulate a point source corresponding to a small leak such as gasoline leaking from an underground storage tank. With previous versions of MT3D and MT3DMS, the only way this could be accomplished was by defining a point source in the MODFLOW model and associating a concentration with the source. This is typically accomplished by creating a small injection well. With the latest version of MT3DMS, a new option has been added called "mass loading." This option is supported in MT3DMS. With the mass loading option, a point source can be added to the transport model independent of any sources in the flow model. The user directly enters a mass transfer rate for the source. Mass loading is part of the Source/Sink Mixing package. Mass loading sources are defined by selecting a set of cells and selecting the Point Source/Sink command in the MT3D menu. Mass loading sources can also be defined using GIS objects in the Map module. Click here to learn more about the MT3DMS interface in GMS 4.0. Dual Domain Sorption in GMS (Groundwater Modeling System) With previous versions of MT3DMS, if the dual domain mass transfer option was selected in the Chemical Reactions package, sorption could not be simulated. In the most recent version of MT3DMS, a new option has been added that allows dual domain mass transfer and sorption to be modeled simultaneously. This option is supported in GMS v4.0. Pumping Well Data in GMS (Groundwater Modeling System) Obs. Well Data in GMS (Groundwater Modeling System) Coord. Transform in GMS (Groundwater Modeling System) FEMW Curves in GMS (Groundwater Modeling System) The FEMWATER model supported in the 3D Mesh module of GMS simulates flow in both the saturated and unsaturated zones. There are three curves assigned to each material type that define the characteristics of flow in the unsaturated zone: relative conductivity vs. pressure head, water content vs. pressure head, and water capacity vs. pressure head. Each of these curves must be defined by the user. In GMS v3.0, a new dialog was introduced for automatically generating unsaturated zone curves using the Van Genuchten equations. While this dialog made defining the curves easier, the resulting curves sometimes caused problems with model convergence. The curves are defined in a piecewise linear fashion. Some of the curves exhibit sharp breaks in curvature. If the points defining the curve are too sparse in the region where the curvature is sharp, FEMWATER may be unable to converge. The FEMWATER unsaturated zone curve generator has been greatly improved in version 4.0. The old curve generator determined the spacing of the points on the curve according to a "max percent change" criterion. The new curve generator allows the user to specify the exact number of points used on the curve. GMS then distributes the given number of points along the curve in an optimal fashion such that the spacing of the points on the curve decreases in regions of high curvature and increases in regions of low curvature. A close-up of two sample curves generated using the new approach is shown below. These new curves are much less likely to cause stability problems. |
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Click here to learn more about the FEMWATER interface in GMS 3.1. UTCHEM in GMS (Groundwater Modeling System) GMS includes an interface to the UTCHEM model in the 3D grid module. UTCHEM is a multiphase flow and transport model developed by the Center for Petroleum and Geosystems Engineering at the University of Texas at Austin. UTCHEM is ideally suited for pump and treat simulations, particularly the simulation of surfactant-enhanced aquifer remediation (SEAR). Future iterations of the GMS/UTCHEM interface will include the simulation of biodegradation. Starting Heads in GMS (Groundwater Modeling System) In version 3.0 of GMS, we introduced the "True Layer" approach for dealing with layer arrays in the BCF package of MODFLOW. With the traditional MODFLOW approach, the layer arrays required by the BCF package depend on the layer type. With the true layer approach, the top and bottom elevation, Kh and Kv are entered for each layer regardless of the layer type. When GMS saves the MODFLOW files, it automatically computes the required arrays for each layer using the elevation and K arrays. One of the arrays that must be calculated for the BCF package is the leakance (VCONT) array. This array is required for all layers except the bottom-most layer. It represents a conductance for flow in the vertical direction and is a function of the vertical distance between cell centers and the vertical hydraulic conductivity. In GMS v3.0, the conductance term for the top layer was calculated using the top elevation array entered by the user. In many cases, this elevation array represents the ground surface which may be significantly higher than the water table elevation. Leakance is more accurately computed using the water table elevation. While the exact location of the water table may not be known at the beginning of a simulation, it can often be reasonably approximated. A new option has been added to GMS v4.0 that allows the water table to be used in the leakance calculations. A toggle labeled "Use starting heads to compute leakance" has been added to the BCF package. If this toggle is selected, the starting head values are used to compute the VCONT array when the MODFLOW files are saved. This only applies to the first layer. For all other layers, the top elevation array is used to compute the VCONT array. Plot Files in GMS (Groundwater Modeling System) The "project file" approach to dealing with file i/o was introduced in version 3.0 of GMS. All of the data related to a modeling project can be automatically saved using the Save command in the File menu. This includes any model solutions that have been imported into GMS. The entire project can be read back into memory using the Open command in the File menu. In version 3.0, there was one type of data that was not saved with the project. Any plots that were set up using the plot window were not preserved with the project. Version 3.1 of GMS will now save a plot file with a project that saves all plots that have been defined by the user. The plots are fully restored when the project is read back into GMS. JPEG Files in GMS (Groundwater Modeling System) In previous versions of GMS, a scanned map or aerial photo could be imported into GMS and displayed in the background as a base map or texture mapped to 2D surfaces or to the top of 3D grids or meshes. These images were imported as TIFF files (*.tif). In GMS v3.1, digital images can now be imported as JPEG (*.jpg) files. Depending on the image, JPEG files are often much more efficient than TIFF files in terms of file size for a given color depth and image resolution. To import a JPEG image, select the Import command in the File menu and select the "*.jpg" filter. |
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Copyright 1999. GMS/WMS/SMS Group. All rights reserved. Email tech@scisoft-gms.com.
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