GMS:LPF Package: Difference between revisions
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{{MODFLOW Links}} | {{MODFLOW Links}} | ||
The Layer-Property Flow (LPF) package is an alternative to the [[GMS:BCF Package|BCF]] and [[GMS:HUF Package|HUF]] packages and is similar to the "true layer" option used with the BCF package in version 3.1. With MODFLOW 2000, the layer elevations (top and bottom) are defined as input to the Global Process (using the [[GMS:Global Options/Basic Package|''Global Options'' dialog]]), regardless of which flow package is being used. With the LPF package, define the horizontal (K<sub>h</sub> or HK) and vertical hydraulic conductivity (K<sub>v</sub> or VK) for each layer. MODFLOW then computes the cell by cell conductances using the K values and the layer geometry. | |||
Other noteworthy features include the ability to enter horizontal anisotropy values on a cell by cell basis. There is also an option to specify vertical anisotropy factors rather than vertical hydraulic conductivity values. This option is particularly useful when performing automated parameter estimation since it ties the K<sub>v</sub> to K<sub>h</sub> and eliminates the need to define K<sub>v</sub> as an independent parameter. | Other noteworthy features include the ability to enter horizontal anisotropy values on a cell by cell basis. There is also an option to specify vertical anisotropy factors rather than vertical hydraulic conductivity values. This option is particularly useful when performing automated parameter estimation since it ties the K<sub>v</sub> to K<sub>h</sub> and eliminates the need to define K<sub>v</sub> as an independent parameter. | ||
Another feature of the LPF package relative to the BCF package is that there are now only two layer types: confined and convertible. A convertible layer is similar to the | Another feature of the LPF package relative to the BCF package is that there are now only two layer types: confined and convertible. A convertible layer is similar to the LAYCON = 2 and LAYCON = 3 types in the BCF package. The layer can be either confined or unconfined depending on the elevation of the computed water table. | ||
Once the LPF package has been chosen using the packages dialog, the LPF package dialog can be accessed through the LPF | Once the LPF package has been chosen using the packages dialog, the ''LPF package'' dialog can be accessed through the '''LPF – Layer Property Flow''' command in the ''MODFLOW'' menu. | ||
[[File:MODFLOW-LPF.png|thumb|350 px|The ''LPF Package'' dialog.]] | |||
=== Use data arrays === | === Use data arrays === | ||
This option allows | This option allows entering conductivities on a layer-by-layer basis. When this option is chosen, the '''Horizontal Hyd. Conductivity''', '''Vertical Hyd. Conductivity''', '''Specific Storage''', etc. buttons will be available. | ||
=== Use material ids === | === Use material ids === | ||
This options uses material sets in the place of property arrays. Property values are entered on a material-by-material basis. When MODFLOW files are saved, GMS internally replaces the correct values from the materials to the property arrays. When this option is chose, the property array buttons are replaced with the Material Properties and Material IDs buttons. | This options uses material sets in the place of property arrays. Property values are entered on a material-by-material basis. When MODFLOW files are saved, GMS internally replaces the correct values from the materials to the property arrays. When this option is chose, the property array buttons are replaced with the [[GMS:Materials|'''Material Properties''']] and [[GMS:MODFLOW_Array_Editor#Material_ID_Legend|'''Material IDs''']] buttons. | ||
=== Layer === | === Layer === | ||
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=== Layer type === | === Layer type === | ||
This radio group selects the layer type for the current layer. | This radio group selects the layer type for the current layer. There are four options, Confined, Convertible, Convertible Negative, and Convertible Upstream. By default, all layers are convertible (where the layer can be either confined or unconfined depending on the elevation of the computed water table). Here layer type can be changed to confined. Only one layer type can be assigned to each grid layer. | ||
=== Vertical hydraulic conductivity === | === Vertical hydraulic conductivity === | ||
The LPF package has the option to enter vertical hydraulic conductivity values as either actual hydraulic conductivity values or as anisotropy factors dependant on horizontal hydraulic conductivity. Vertical anisotropy (VKA) "is the ratio of horizontal to vertical hydraulic conductivity. In this case, HK is divided by VKA to obtain | The LPF package has the option to enter vertical hydraulic conductivity values as either actual hydraulic conductivity values or as anisotropy factors dependant on horizontal hydraulic conductivity. Vertical anisotropy (VKA) "is the ratio of horizontal to vertical hydraulic conductivity. In this case, HK is divided by VKA to obtain VK, and values of VKA typically are greater than or equal to 1.0."<ref> | ||
{{citation | {{citation | ||
|author=Harbaugh, A.W., Banta, E.R., Hill, M.C., McDonald, M.G. | |author=Harbaugh, A.W., Banta, E.R., Hill, M.C., McDonald, M.G. | ||
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|year=2000 | |year=2000 | ||
|url=http://water.usgs.gov/nrp/gwsoftware/modflow2000/ofr00-92.pdf | |url=http://water.usgs.gov/nrp/gwsoftware/modflow2000/ofr00-92.pdf | ||
|page=62 | |||
}}</ref> | }}</ref> | ||
These options are only available for multi-layer models. | These options are only available for multi-layer models. | ||
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=== Interblock transmissivity === | === Interblock transmissivity === | ||
The method used for computing interblock transmissivity is specified using the pull-down list in the middle right portion of the LPF Package dialog. | The method used for computing interblock transmissivity is specified using the pull-down list in the middle right portion of the ''LPF Package'' dialog. | ||
=== Layer Data Arrays === | === Layer Data Arrays === | ||
The | The seven buttons in the middle-right portion of the dialog represent layer data arrays such as elevations and hydraulic conductivity. Each of the seven buttons brings up the [[GMS:MODFLOW Array Editor|''MODFLOW Array Editor'']]. Not all of the data arrays need to be specified for each layer. Some arrays such as [[GMS:BCF_Package#Storage coefficients|Specific Storage]] and [[GMS:BCF_Package#Storage coefficients|Specific Yield]] are only required for transient models. | ||
=== | === Cell Wetting Parameters === | ||
If re-wetting of cells (when cells that went dry during the simulation later have head) is allowed, a wetting factor, wetting iteration interval, and wetting equation must be specified. | |||
===More LPF Options=== | |||
Clicking on the '''More LPF Options''' button brings up the ''LPF Package Options'' dialog where it is possible to remove vertical leakance correction or set a head value for dry cells. | |||
[[File:MODFLOW-LPFoptions.jpg|thumb|none|left|425 px|The ''LPF Package Options'' dialog.]] | |||
=== Remove vertical leakance correction === | ==== Remove vertical leakance correction ==== | ||
This is the value that MODFLOW will give to cells with a head level below the bottom elevation of the cell (dry cell). When reading in a solution, GMS will mark cells with this value with a dry cell symbol. The Layer Property Flow Package of MODFLOW-2000 was modified by A.W. Harbaugh (U.S. Geological Survey, written commun., 2002) to remove the vertical leakage correction for conditions in which a partially saturated cell is immediately below a fully or partially saturated cell (Harbaugh and others, 2000, p. 31-33). The vertical leakage correction simulates perched conditions within an aquifer system. However, perched conditions are not known to be widespread on a basin scale. The vertical leakage correction adds an additional nonlinear term to the model (A.W. Harbaugh, U.S. Geological Survey, written commun., 2002), which resulted in several of the numerical solvers (SIP (strongly implicit procedures), SOR (slice-successive overrelaxation), and PCG (Hill, 1990; Harbaugh and others, 2000) not coming to a solution and the LMG (link-algebraic multigrid; Mehl and Hill,2001) solver providing unacceptable volumetric budget errors (wrir02-4200.pdf) . Thus in the LPF package | This is the value that MODFLOW will give to cells with a head level below the bottom elevation of the cell (dry cell). When reading in a solution, GMS will mark cells with this value with a dry cell symbol. The Layer Property Flow Package of MODFLOW-2000 was modified by A.W. Harbaugh (U.S. Geological Survey, written commun., 2002) to remove the vertical leakage correction for conditions in which a partially saturated cell is immediately below a fully or partially saturated cell (Harbaugh and others, 2000, p. 31-33). The vertical leakage correction simulates perched conditions within an aquifer system. However, perched conditions are not known to be widespread on a basin scale. The vertical leakage correction adds an additional nonlinear term to the model (A.W. Harbaugh, U.S. Geological Survey, written commun., 2002), which resulted in several of the numerical solvers (SIP (strongly implicit procedures), SOR (slice-successive overrelaxation), and PCG (Hill, 1990; Harbaugh and others, 2000) not coming to a solution and the LMG (link-algebraic multigrid; Mehl and Hill,2001) solver providing unacceptable volumetric budget errors (wrir02-4200.pdf) . Thus in the LPF package there is the option to turn off the vertical leakance correction to account for these factors. After turning on the ''Remove Vertical Leakance Correction'' toggle, GMS then uses the [http://water.usgs.gov/nrp/gwsoftware/modflow2000/MFDOC/index.html?lpf.htm NOCVCORRCTION] option that is found in MODFLOW2005 to remove vertical leakance corrections. | ||
=== | ==== Head Assigned to Dry Cells ==== | ||
This is the value that MODFLOW will give to cells with a head level below the bottom elevation of the cell (dry cell). When reading in a solution, GMS will mark cells with this value with a dry cell symbol. | |||
==Notes== | ==Notes== | ||
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[[Category:MODFLOW]] | [[Category:MODFLOW]] | ||
[[Category:MODFLOW Packages]] | [[Category:MODFLOW Packages]] | ||
[[Category:MODFLOW Dialogs]] | |||
[[Category:MODFLOW-USG]] | |||
[[Category:External Links]] | |||
