AHGW:MODFLOW Data Model

MODFLOW Data Model

The MODFLOW Data Model is an extension to the Simulation portion of the Arc Hydro Groundwater (AHGW) data model and is used to store complete MODFLOW simulations in an ArcGIS geodatabase. The data model consists of a set of tables for archiving MODFLOW model data. Having the model in the database makes it possible to utilize the mapping and plotting capabilities of ArcGIS. It also facilitates the use of tools, such as those provided in MODFLOW Analyst, for populating the MODFLOW package tables using data from the Arc Hydro groundwater and surface water data models. It also provides an archival tool for models facilitating permissions, check-in/check-out capabilities, and web services.

Documentation

In addition to this wiki, you should refer to the diagram of the MODFLOW Data Model.

• MODFLOW Data Model diagram as a PDF

The MODFLOW Data Model generally uses the same naming convention for variables defined by MODFLOW. The meanings of all these variables are only summarized here. Refer to the MODFLOW documentation for a full description.

• USGS MODFLOW site

Introduction

The AHGW data model includes a Simulation component that facilitates the storage of simulation models (grids, meshes, and associated data) in a geodatabase. The simulation component uses polygons, points, and multi-patches to represent 2D and 3D cells and nodes. The MODFLOW data model consists of a series of tables and relationships associated with the simulation component. The data model is based on MODFLOW 2000 and includes all of the standard MODFLOW packages. It will gradually be expanded to include supplemental packages.

For some of the MODFLOW packages, including the Global Package, the LPF package, and the Recharge package, the input data associated with the package is primarily one or more arrays of data representing cell-by-cell values. These arrays are represented in the data model using tables indexed by a cell ID. In the case of the stress packages, the package input data are typically not defined using an array corresponding to the entire grid. Rather, the data are associated with a subset of the grid cells. For example, the input to the well package is a list of well instances where each well lists the IJK indices of the corresponding cell and the pumping rate. For transient simulations, one set of values is listed for each stress period (simulation interval). The input to these packages is stored in tables which include the cell IDs, the stress period ID, and the attributes associated with the particular stress package (water level, conductance, etc.). In either case, the resulting tables can be joined with Cell2D, Cell3D, Node2D, and Node3D features to display the locations of the stress package objects in the model domain.

Cell and Node Features

The MODFLOW Data Model is an extension of the Arc Hydro Groundwater Simulation Feature Dataset. The MODFLOW data is stored primarily in a set of tables described below and the Cell and Node features of the Simulation Feature Dataset are used to generate map layers in ArcGIS in order to visualize MODFLOW models. The features are also used to perform spatial queries such as interpolating hydraulic conductivity values to the K array in the LPF package. When used with the MODFLOW Data Model, one additional field is added to each of the cell and node features in order to support joins based on MODFLOW cell ids. An IJ field is added to the Cell2D and Node2D features and an IJK field is added to the Cell3D and Node3D features. The resulting feature classes contain the following fields (in addition to the point and polygon fields):

Cell2D
Field	Type	Description
OBJECTID	OID
HydroID	Long Integer	Unique Arc Hydro identifier
HydroCode	Long Integer	Application-specific Arc Hydro identifier
IJ	Long Integer	Row/column-based MODFLOW cell identifier

Node2D
Field	Type	Description
OBJECTID	OID
HydroID	Long Integer	Unique Arc Hydro identifier
HydroCode	Long Integer	Application-specific Arc Hydro identifier
IJ	Long Integer	Row/column-based MODFLOW cell identifier

Cell3D
Field	Type	Description
OBJECTID	OID
HydroID	Long Integer	Unique Arc Hydro identifier
HydroCode	Long Integer	Application-specific Arc Hydro identifier
IJK	Long Integer	Row/column/layer-based MODFLOW cell identifier

Node3D
Field	Type	Description
OBJECTID	OID
HydroID	Long Integer	Unique Arc Hydro identifier
HydroCode	Long Integer	Application-specific Arc Hydro identifier
IJK	Long Integer	Row/column/layer-based MODFLOW cell identifier

CellIndex Table

In the MODFLOW input files, cells are identified by a combination of three integers representing the row, column, and layer indices of the cell (I, J, K). Since joins can only be accomplished using a single field, it is necessary to generate an integer field corresponding to a unique IJK combination. Furthermore, some MODFLOW input arrays are fundamentally 2D in nature (Evapotranspiration, Recharge, etc.) and require an integer identifier corresponding to a unique IJ combination. To facilitate joins and queries related to the MODFLOW data, the data model includes a CellIndex table containing the following fields:

CellIndex
Field	Type	Description
OBJECTID	OID
I	Long Integer	Row index
J	Long Integer	Column index
K	Long Integer	Layer index
IJ	Long Integer	Row/column index
IJK	Long Integer	Row/column/layer index

The IJ and IJK fields of the CellIndex table is populated from the I,J,K values by starting at a value of one for the cell corresponding to I=1, J=1, K=1, and looping through the cells in the grid row-by-row within each layer, and incrementing the index. The IJ index ordering is repeated within each layer. The following example indicates how this numbering would be accomplished in both the C and VB languages:

// C Syntax
// numI, numJ, numK = number of cells in the I, J and K directions
int index1 = 1;
for (int K = 0; K < numK; ++K) {
  int index2 = 1;
  for (int I = 0; I < numI; ++I) {
    for (int J = 0; J < numJ; ++J) {
      IJK = index1;
      IJ = index2;
      ++index1;
      ++index2;
    }
  }
}

' Visual Basic Syntax
' numI, numJ, numK = number of cells in the I, J and K directions
index1 = 1
For K = 1 To numK
  index2 = 1
  For I = 1 To numI
    For J = 1 To numJ
      IJ = index2
      IJK = index1
      index1 = index1 + 1
      index2 = index2 + 1
    Next J
  Next I
Next K

For example, consider a MODFLOW grid with three rows, four columns, and two layers (numI=3, numJ=4, numK=2). The CellIndex table for this grid would be as follows:

CellIndex Table
I	J	K	IJ	IJK
1	1	1	1	1
1	2	1	2	2
1	3	1	3	3
1	4	1	4	4
2	1	1	5	5
2	2	1	6	6
2	3	1	7	7
2	4	1	8	8
3	1	1	9	9
3	2	1	10	10
3	3	1	11	11
3	4	1	12	12
1	1	2	1	13
1	2	2	2	14
1	3	2	3	15
1	4	2	4	16
2	1	2	5	17
2	2	2	6	18
2	3	2	7	19
2	4	2	8	20
3	1	2	9	21
3	2	2	10	22
3	3	2	11	23
3	4	2	12	24

It is also helpful to view the IJ and IJK indices on a layer-by-layer basis (IJ values shown in red, IJK values in blue):

K=1
	J=1	J=2	J=3	J=4
I=1	1 1	2 2	3 3	4 4
I=2	5 5	6 6	7 7	8 8
I=3	9 9	10 10	11 11	12 12

K=2
	J=1	J=2	J=3	J=4
I=1	1 13	2 14	3 15	4 16
I=2	5 17	6 18	7 19	8 20
I=3	9 21	10 22	11 23	12 24

The Cell2D and Node2D features include an IJ field and the Cell3D and Node3D features include an IJK field where the IJ and IJK fields are populated using the same strategy used to populate the CellIndex table. The MODFLOW data is stored in a separate series of tables (described below) and the tables containing cell-by-cell data include either an IJ or IJK field depending on whether it is a 2D array or a 3D array. The MODFLOW tables are then joined to the cell and node features using the CellIndex table. For example, a map layer illustrating hydraulic conductivity values with polygons could be generated by first joining the IJK field of the LPFProperties table to the IJK field of the CellIndex table. The CellIndex.IJ field of the resulting temporary table would then be joined to the IJ field Cell2D feature class. This type of join can be easily generated in one step using the “Make Query Table” geo-processing tool in the MODFLOW Analyst. The values associated with individual grid layers in the resulting map layer can be displayed using a definition query (“CellIndex.K = 1, CellIndex.K=2, etc.). For 2D arrays or for models with only one grid layer, the CellIndex table can be bypassed and the IJ or IJK field of the MODFLOW tables can be joined directly with the IJ field of the Node2D and Cell2D features since the IJ and IJK values are identical for K=1. Similarly, joins can be performed directly between IJK-based tables and the Cell3D and/or Node3D features. Map layers of MODFLOW data associated with cell and node features can be symbolized and toggled on/off independently from other features in the TOC window in ArcMap and ArcScene.

Sometimes it is necessary to derive I, J, and K values from the IJ or IJK indices, or vice versa. The following C and Visual Basic code shows how to get the I and J indices given an IJ value:

// C Syntax
// '%' is the modulus operator
I = ((IJ - 1) / numJ) + 1;
J = (((IJ - 1) % numJ) + 1;

' Visual Basic Syntax
' 'Mod' is the modulus operator, 'Int' converts a decimal to an integer
I = Int((IJ - 1) / numJ) + 1
J = ((IJ - 1) Mod numJ) + 1

Likewise, to get the I, J, and K indices from an IJK value:

// C Syntax
I = (((IJK - 1) / numJ) % numI) + 1;
J = ((IJK - 1) % numJ) + 1;
K = ((IJK - 1) / (numI * numJ)) + 1;

' Visual Basic Syntax
I = (Int((IJK - 1) / numJ) Mod numI) + 1
J = (IJK - 1) Mod numJ + 1
K = Int((IJK - 1) / (numI * numJ)) + 1

Finally, IJ and IJK indices can be derived from I, J, and K values as follows:

// C Syntax
IJ = ((I - 1) * numJ) + J;
IJK = ((K-1) * numI * numJ) + ((I-1) * numJ) + J;

' Visual Basic Syntax
IJ = ((I - 1) * numJ) + J
IJK = ((K - 1) * numI * numJ) + ((I - 1) * numJ) + J

It should be noted that with this strategy, if the grid is modified by adding or deleting rows or columns, all tables which include IJ or IJK fields will need to be modified by renumbering the IJ and IJK values according to the new configuration. We will eventually provide tools to automate this process.

Groups

Tables that are related to each other are put together in a group and, in the diagram, are displayed together in a colored box. For example, three tables are used to represent the LPF package and these are grouped together in the data model. Groups typically are associated with MODFLOW packages but not necessarily. For example, the Output group does not correspond to any MODFLOW package.

Global Settings / Name File

The MDFGlobals table is used to store global variables that are not associated with a particular MODFLOW package or MODFLOW input file, but which are useful for managing the MDM. Currently the only field in this table is the model version. Additional fields will be added as the need arises. The Version field is used to indicate which MODFLOW version is represented in the data model (2000, 2005, etc.). This makes it possible to support multiple versions of the data model. Currently the only versions the data model supports are MODFLOW 2000 and 2005.

The Global Settings group also includes the NameFile table.

MDFGlobals
Field	Type	Description
OBJECTID	OID
MODFLOW_Version	Text	Version of MODFLOW targeted, e.g. "MODFLOW 2000"
DataModelVersion	Text	Version of the MODFLOW Data Model, e.g. "1.0"
NameFilePath	Text	Full path and filename of the exported or imported name file on disk.

NameFile
Field	Type	Description
OBJECTID	OID
FileType	Text	File type ("Ftype" in MODFLOW documentation, but "Ftype" has other meanings in Arc Hydro). FileType coded value domain.
Nunit	Long Integer	Fortran unit number
Fname	Text	Name of the file
Use	Short Integer	Flag indicating whether or not the file is being used. Only when this flag is true should the file be included in the name file. Uses TrueFalse coded value domain.

Discretization (DIS)

One of the main input files to MODFLOW is the Discretization (DIS) File. It defines the spatial and temporal discretization used in the model. Some of the information in the DIS file is represented by the Cell2D feature class. The rest comes from the following tables.

The DISVars table contains variables associated with the DIS file. The RefTime variable is not written to the DIS file. It is used by tools associated with the MDM to generate date/time values representing the beginning and ending of each stress period in the Stress Periods table. A geo-processing tool exists that computes these values and adds two columns (Start, End) to the table when necessary.

The DELRC table is used to store the widths (discretization) of the rows and columns. While this information could be derived from the geometry of the Cell2D polygons, it is convenient to store it explicitly in a table.

The StressPeriods table stores information on stress periods and time steps. The SPID field defines the stress period order and must begin with 1 and go to N where N is the number of stress periods. Other tables in the data model which refer to stress periods reference the stress period ID.

The DISLayers table contains variables defined on a layer-by-layer basis.

The TopElev and BotmElev tables are used to store the top and bottom elevations for the cells of the grid. For the TopElev table, only the cells in the top layer should be included. The top elevations for the remaining layers are assumed to be equivalent to the bottom elevations of the above layer as defined by the BotmElev table. Thus, the BotmElev table should include the bottom elevations for all cells in the grid. The BotmElevCBD field is used to store the bottom elevation of confining beds, if appropriate.

DISVars
Field	Type	Description
OBJECTID	OID
NLAY	Long Integer	Number of layers
NROW	Long Integer	Number of rows
NCOL	Long Integer	Number of columns
ITMUNI	Short Integer	Time unit. TimeUnit coded value domain
LENUNI	Short Integer	Length unit. LengthUnit coded value domain
RefTime	Date	The Date/Time of the beginning of the simulation

DELRC
Field	Type	Description
OBJECTID	OID
Direction	Text	Row or column. Direction coded value domain
Num	Long Integer	Row or column number
Width	Double	Row or column width

TopElev
Field	Type	Description
OBJECTID	OID
IJK	Long Integer	IJK Index
TopElev	Double	Top elevation of cell

BotmElev
Field	Type	Description
OBJECTID	OID
IJK	Long Integer	IJK Index
BotmElev	Double	Bottom elevation of cell
BotmElevCBD	Double	Bottom elevation of Quasi-3D confining bed below cell

DISLayers
Field	Type	Description
OBJECTID	OID
Layer	Long Integer	Layer
LAYCBD	Short Integer	Quasi-3D confining bed flag
AM_TopElev	Double	TopElev array multiplier
AM_BotmElev	Double	BotmElev array multiplier
AM_BotmElevCBD	Double	BotmElevCBD array multiplier

StressPeriods
Field	Type	Description
OBJECTID	OID
SPID	Long Integer	Stress period number used to define the order, e.g. 1, 2, 3
PERLEN	Double	Period length
NSTP	Long Integer	Number of time steps
TSMULT	Double	Time step multiplier
SSorTr	Text	Steady state or transient. SteadyState coded value domain
RIV_ITMP	Short Integer	Use previous flag
WEL_ITMP	Short Integer	Use previous flag
DRN_ITMP	Short Integer	Use previous flag
GHB_ITMP	Short Integer	Use previous flag
CHD_ITMP	Short Integer	Use previous flag
RCH_INRECH	Short Integer	Use previous flag
RCH_INIRCH	Short Integer	Use previous flag
EVT_INSURF	Short Integer	Use previous flag
EVT_INEVTR	Short Integer	Use previous flag
EVT_INEXDP	Short Integer	Use previous flag
EVT_INIEVT	Short Integer	Use previous flag
MNW1_ITMP	Short Integer	Use previous flag
STR_ITMP	Short Integer	Use previous flag
STR_IRDFLG	Short Integer	Use previous flag
STR_IPTFLG	Short Integer	Use previous flag
SFR_ITMP	Short Integer	Use previous flag
SFR_IRDFLG	Short Integer	Use previous flag
SFR_IPTFLG	Short Integer	Use previous flag
LAK_ITMP	Short Integer	Use previous flag
LAK_ITMP1	Short Integer	Use previous flag
LAK_LWRT	Short Integer	Use previous flag
DRT_ITMP	Short Integer	Use previous flag
ETS_INETSS	Short Integer	Use previous flag
ETS_INETSR	Short Integer	Use previous flag
ETS_INETSX	Short Integer	Use previous flag
ETS_INIETS	Short Integer	Use previous flag
ETS_INSGDF	Short Integer	Use previous flag

Basic Package (BAS6)

The Basic Package is represented using the tables below. The Options and HNOFLO values are stored in the BASVars table as a text string and a double. The IBOUND and STRT arrays are stored in the Basic table. The IBOUND array is used to define the active/inactive status of the grid and the STRT array is used to define the starting heads. Mulipliers for the IBOUND and STRT arrays are stored in the BasicArrayMult table.

BASVars
Field	Type	Description
OBJECTID	OID
Options	Text	Option words, space delimited
HNOFLO	Double	Head assigned to inactive cells
HEADNG1	Text	First comment line
HEADNG2	Text	Second comment line

Basic
Field	Type	Description
OBJECTID	OID
IJK	Long Integer	IJK Index
IBOUND	Long Integer	IBOUND array
STRT	Double	Starting heads array

BasicArrayMult
Field	Type	Description
OBJECTID	OID
Layer	Long Integer	Layer
AM_IBOUND	Long Integer	IBOUND array multiplier
AM_STRT	Double	Starting heads array multiplier

Output control

MODFLOW has two options for specifying output control: using words or using numeric codes. The MDM stores the options in tables patterned after the numeric codes option. The tool which converts MODFLOW models to geodatabases handles both options. Furthermore, the tools which export from the geodatabase to native MODFLOW files can be designed to export either format.

Not all of the output options are supported, in order to make the tables manageable.

The Output Control data consist of two parts: four global flags (IHEDFM, IDDNFM, IHEDUN, IDDNUN) and a set of flags that are specified for each time step. The global flags are stored in the OCVars table.

Time step data is stored in the OCTS table. Note that there is no INCODE value in the OCTS table. It is assumed that INCODE=0, indicating that all layers are treated the same way for a given time step. This allows the further assumption that there is one record for each output time step.

The OCTS table is entirely dependent on the records in the StressPeriods table and the number of time steps (NSTP) per stress period. Any tools used to manage the MDM will need to update the records in the OCTS table any time the StressPeriods table is edited.

Many of the MODFLOW packages include a flag at the top of the file indicating whether or not the cell-by-cell flow terms for the package should be output to the CCF file. These flags are stored in a single table called the CBFlags table.

OCVars
Field	Type	Description
OBJECTID	OID
IHEDFM	Short Integer	Format for printing heads. OCVarsFileType coded value domain
IDDNFM	Short Integer	Format for printing drawdowns. OCVarsFileType coded value domain
IHEDUN	Long Integer	Unit number for saving heads
IDDNUN	Long Integer	Unit number for saving drawdowns
IBDOPT	Long Integer	Compact budget
IAUXSV	Short Integer	Auxiliary flag for saving cell-by-cell budget data

OCTS
Field	Type	Description
OBJECTID	OID
SPID	Long Integer	Stress period ID
TSNum	Long Integer	Time step number
IHDDFL	Short Integer	Head and drawdown output flag
IBUDFL	Short Integer	Budget print flag
ICBCFL	Short Integer	Flag for writing cell-by-cell flow
Hdpr	Short Integer	Output flag for head printout
Ddpr	Short Integer	Output flag for drawdown printout
Hdsv	Short Integer	Output flag for head saving
Ddsv	Short Integer	Output flag for drawdown saving

CBFlags
Field	Type	Description
OBJECTID	OID
IBCFCB	Short Integer	Flag to store data to the CCF file
ILPFCB	Short Integer	Flag to store data to the CCF file
IRIVCB	Short Integer	Flag to store data to the CCF file
IWELCB	Short Integer	Flag to store data to the CCF file
IDRNCB	Short Integer	Flag to store data to the CCF file
IGHBCB	Short Integer	Flag to store data to the CCF file
IRCHCB	Short Integer	Flag to store data to the CCF file
IEVTCB	Short Integer	Flag to store data to the CCF file
IMNW1CB	Short Integer	Flag to store data to the CCF file
ILKCB	Short Integer	Flag to store data to the CCF file
IHUFCB	Short Integer	Flag to store data to the CCF file
ISTCB1_STR	Short Integer	Flag to store data to the CCF file
ISTCB2_STR	Short Integer	Flag to store data to the CCF file
ISTCB1_SFR	Short Integer	Flag to store data to the CCF file
ISTCB2_SFR	Short Integer	Flag to store data to the CCF file
IDRTCB	Short Integer	Flag to store data to the CCF file
IETSCB	Short Integer	Flag to store data to the CCF file
IUZFCB1	Short Integer	Flag to store data to the CCF file
IUZFCB2	Short Integer	Flag to store data to the CCF file

Block-Centered Flow Package (BCF6)

The data for the Block-Centered Flow Package are stored in a combination of variables and tables. The IBCFCB value is stored in the CBFlags table in the Output control group.

The BCFVars table stores various variables associated with the BCF package.

The BCFLayers table is used to store layer-by-layer variables. In the MODFLOW text input files, the Ltype flag consists of two digits: one representing the mean (LAYAVG) and one representing the layer type (LAYCON). These two digits are combined to a single flag in the input file but are stored separately in the MDM. There should be one record in the table for each layer in the grid.

The BCFProperties table stores the aquifer property arrays associated with the BCF package. Note that the data in these arrays are applicable to some layers, but not to others, depending on the layer type (Ltype). The users of the MDM (and the applications that operate on the MDM) will need to ensure that the fields of the records in the table are populated for the cells in the appropriate layers.

BCFVars
Field	Type	Description
OBJECTID	OID
HDRY	Double	Head assigned to dry cells
IWDFLG	Short Integer	Flag that determines if wetting capability is active
WETFCT	Double	Factor included in head calculation that is initially established at a cell when it is converted from dry to wet
IWETIT	Long Integer	Iteration interval for attempting to wet cells
IHDWET	Short Integer	Flag that determines which equation is used to define initial head at cells that become wet

BCFLayers
Field	Type	Description
OBJECTID	OID
Layer	Long Integer	Layer number
LAYAVG	Short Integer	Mean. BCFMean coded value domain
LAYCON	Short Integer	Layer type. BCFLayerType coded value domain
TRPY	Double	Horizontal anisotropy for the layer
AM_Sf1	Double	Sf1 array multiplier
AM_Tran	Double	Tran array multiplier
AM_HY	Double	HY array multiplier
AM_Vcont	Double	Vcont array multiplier
AM_Sf2	Double	Sf2 array multiplier
AM_WETDRY	Double	WETDRY array multiplier

BCFProperties
Field	Type	Description
OBJECTID	OID
IJK	Long Integer	IJK Index
HY	Double	Hydraulic conductivity
Tran	Double	Transmissivity
Vcont	Double	Vertical conductivity
Sf1	Double	Primary storage coefficient
Sf2	Double	Secondary storage coefficient
WETDRY	Double	wetting threshold and flag to indicate which neighboring cells can cause cell to become wet

Layer-Property Flow (LPF) Package

The LPF Package is handled similarly to the BCF package. The ILPFCB value is stored in the CBFlags table in the Output control group. Variables associated with the LPF package are stored in the LPFVars table. Layer-based variables associated with the LPF package are stored in the LPFLayers table. The LPF aquifer property arrays are stored in the LPFProperties table. As is the case with the BCF package, the contents of the “arrays” depend on the layer types defined by the LAYTYP flag in the LPFLayers table. Some arrays are only required for certain layer types. The VKCB field is used to store the vertical conductivity for quasi-3d confining beds as defined by the LAYCBD table in the DIS section. The IJK field in records associated with VKCB values is the cell in the layer just above the confining bed.

LPFVars
Field	Type	Description
OBJECTID	OID
HDRY	Double	Head assigned to dry cells
WETFCT	Double	Factor included in head calculation that is initially established at a cell when it is converted from dry to wet
IWETIT	Long Integer	Iteration interval for attempting to wet cells
IHDWET	Short Integer	Flag that determines which equation is used to define initial head at cells that become wet

LPFLayers
Field	Type	Description
OBJECTID	OID
Layer	Long Integer	Layer number
LAYTYP	Short Integer	Layer type. LPFLayerType coded value domain
LAYAVG	Short Integer	Mean. LPFMean coded value domain
CHANI	Double	Horizontal anisotropy flag
LAYVKA	Short Integer	Vertical hydraulic conductivity flag
LAYWET	Short Integer	Flag indicating if wetting is active
AM_HK	Double	HK array multiplier
AM_HANI	Double	HANI array multiplier
AM_VKA	Double	VKA array multiplier
AM_Ss	Double	Ss array multiplier
AM_Sy	Double	Sy array multiplier
AM_WETDRY	Double	WETDRY array multiplier
AM_VKCB	Double	VKCB array multiplier

LPFProperties
Field	Type	Description
OBJECTID	OID
IJK	Long Integer	IJK Index
HK	Double	Hydraulic conductivity
HANI	Double	Anisotropy
VKA	Double	Vertical conductivity or ratio
Ss	Double	Specific storage
Sy	Double	Specific yield
WETDRY	Double	Wetting threshold and flag
VKCB	Double	Vertical conductivity of Quasi-3D confining bed

Hydrogeologic Unit Flow (HUF2) Package (v 2.0+)

Coming soon in version 2.0...

HUFVars
Field	Type	Description
OBJECTID	OID
HDRY	Double	Head assigned to cells converted to dry in simulation
NHUF	Long Integer	Number of hydrogeologic units
IOHUFHEADS	Short Integer	Flag and unit number
IOHUFFLOWS	Short Integer	Flag and unit number
WETFCT	Double	Factor used when cell converted from dry to wet
IWETIT	Long Integer	Iteration interval for attempting to wet cells
IHDWET	Short Integer	Flag for equation used for initial head at cells that become wet

HUFLayers
Field	Type	Description
OBJECTID	OID
Layer	Long Integer	Layer
LTHUF	Short Integer	Flag specifying layer type
LAYWET	Short Integer	Flag indicating if wetting is active
AM_WETDRY	Double	WETDRY array multiplier

HUFWetDry
Field	Type	Description
OBJECTID	OID
IJK	Long Integer	IJK Index
WETDRY	Double	Wetting threshold and flag for neighboring cells to become wet

HUFUnits
Field	Type	Description
OBJECTID	OID
HGUID	Long Integer	Hydrogeologic unit ID
HGUNAME	Text	Name of the hydrogeologic unit
HGUHANI	Double	Flag and horizontal anisotropy value
HGUVANI	Double	Vertical hydraulic conductivity flag
AM_Top	Double	Top array multiplier
AM_Thick	Double	Thick array multiplier
PRINTCODE_HK	Short Integer	Flag for printing the VK array
PRINTCODE_HANI	Short Integer	Flag for printing the HANI array
PRINTCODE_VK	Short Integer	Flag for printing the VK array
PRINTCODE_Ss	Short Integer	Flag for printing the Ss array
PRINTCODE_Sy	Short Integer	Flag for printing the Sy array

HUFUnitProps
Field	Type	Description
OBJECTID	OID
IJ	Long Integer	IJ Index
HGUID	Long Integer	Hydrogeologic unit ID
Top	Double	Top elevation of the hydrogeologic unit
Thick	Double	Thickness of the hydrogeologic unit

List-Based Stress Packages

Most of the commonly-used stress packages in MODFLOW follow a simple strategy. The cells associated with a given type of stress are identified and an input entry is made for each instance in a list in the package input file. In some cases, multiple entries are made for a given cell (three wells in a single cell, for example). The River, Well, Drain, General Head Boundary, Constant-Head Boundary, and Horizontal Flow Barrier packages follow this format. Each of these packages are represented in the data model using a variable and a table. For each package, the cell-by-cell flow flag (IRIVCB, IWELCB, IDRNCB, etc.) are stored in the CBFlags table in the Output control group. The remaining data associated with the package are stored in a series of tables, one per package. Each record in the tables corresponds to an instance of the given stress at a particular cell for a particular stress period. The SourceID field is used to associate records with the spatial features from which they were derived. The SourceID represents the HydroID of the point, polyline, or polygon in the Framework component of the Arc Hydro database that was used to construct the record in the table. This field is only used when the tables are constructed using a tool in Arc Hydro GW. For the case where pre-built MODFLOW files are imported from another database, the SourceID values should all be Null.

RIV
Field	Type	Description
OBJECTID	OID
IJK	Long Integer	IJK Index
SPID	Long Integer	Stress Period ID
Stage	Double	River stage
Cond	Double	Conductance
Rbot	Double	Elevation of the bottom of the riverbed
IFACE	Long Integer	MODPATH auxiliary variable
Condfact	Double	Factor used to calculate conductance from the parameter value
SourceID	Long Integer	HydroID of the feature that the source comes from
LinearScale	Double	Length from the begining of a polyline to the center of the polyline segement within the MODFLOW cell

CHD
Field	Type	Description
OBJECTID	OID
IJK	Long Integer	IJK Index
SPID	Long Integer	Stress Period ID
Shead	Double	Head at start of stress period
Ehead	Double	Head at end of stress period
Shdfact	Double	Factor used to calculate Shead from the parameter value
Ehdfact	Double	Factor used to calculate Ehead from the parameter value
SourceID	Long Integer	HydroID of the feature that the source comes from
LinearScale	Double	Length from the begining of a polyline to the center of the polyline segement within the MODFLOW cell

WEL
Field	Type	Description
OBJECTID	OID
IJK	Long Integer	IJK Index
SPID	Long Integer	Stress Period ID
Q	Double	Pumping rate
Qfact	Double	Factor used to calculate Q from the parameter value
IFACE	Long Integer	MODPATH auxiliary variable
SourceID	Long Integer	HydroID of the feature that the source comes from
LinearScale	Double	Length from the begining of a polyline to the center of the polyline segement within the MODFLOW cell

DRN
Field	Type	Description
OBJECTID	OID
IJK	Long Integer	IJK Index
SPID	Long Integer	Stress Period ID
Elevation	Double	Elevation of the drain
Cond	Double	Conductance
IFACE	Long Integer	MODPATH auxiliary variable
Condfact	Double	Factor used to calculate conductance from the parameter value
SourceID	Long Integer	HydroID of the feature that the source comes from
LinearScale	Double	Length from the begining of a polyline to the center of the polyline segement within the MODFLOW cell

GHB
Field	Type	Description
OBJECTID	OID
IJK	Long Integer	IJK Index
SPID	Long Integer	Stress Period ID
Bhead	Double	Head on the boundary
Cond	Double	Conductance
IFACE	Long Integer	MODPATH auxiliary variable
Condfact	Double	Factor used to calculate conductance from the parameter value
SourceID	Long Integer	HydroID of the feature that the source comes from
LinearScale	Double	Length from the begining of a polyline to the center of the polyline segement within the MODFLOW cell

HFB6
Field	Type	Description
OBJECTID	OID
IJK1	Long Integer	IJK Index of cell on one side of barrier
IJK2	Long Integer	IJK Index of cell on other side of barrier
Hydchr	Double	Hydraulic characteristic
Factor	Double	Factor used to calculate Hydchr from the parameter value
SourceID	Long Integer	HydroID of the feature that the source comes from
LinearScale	Double	Length from the begining of a polyline to the center of the polyline segement within the MODFLOW cell.

MNW1
Field	Type	Description
OBJECTID	OID
IJK	Long Integer	IJK Index
SPID	Long Integer	Stress Period ID
WellID	Long Integer	Well ID
Qdes	Double	Desired volumetric pumping or recharge rate
QwVal	Double	Water-quality value
Rw	Double	Flag and a variable used to define the cell-to-well conductance
Skin	Double	Defines the friction losses to the well owing to the screen and to formation damage
Hlim	Double	Limiting water level
Href	Double	Reference elevation
DD	Long Integer	Flag that indicates the value of Hlim read is a drawdown or build-up from the reference elevation
Iwgrp	Long Integer	Water-quality group identifier
Cp_C	Double	Coefficient for nonlinear head losses
QCUT	Long Integer	Flag that indicates pumping limits
Qfrcmn	Double	Minimum pumping rate that a well must exceed to remain active
Qfrcmx	Double	Minimum potential pumping rate that must be exceeded to reactivate a well
SITE	Text	Optional label for identifying wells

MNW1Vars
Field	Type	Description
OBJECTID	OID
IWELPT	Short Integer	Flag for printing
NOMOITER	Long Integer	Flow in MNW wells will not be calculated after NOMITER iterations
kspref	Long Integer	Set of water levels that will be used as default reference values for calculating drawdown
LOSSTYPE	Text	Flag to determine the user-specified model for well loss
PLossMNW	Double	If LOSSTYPE is nonlinear, represents the exponent P
PREFIX	Text	Prefix name of file for outputting time series data from MNW
WEL1_FILE	Text	Name of an auxiliary output file
iunw1	Long Integer	Unit number
BYNODE_FILE	Text	Name of an auxiliary output file
iunby	Long Integer	Unit number
BYNODE_ALLTIME	Short Integer	Flag that indicates flow rates should be written to BYNODE or QSUM at every time step
QSUM_FILE	Text	Name of an auxiliary output file
iunqs	Long Integer	Unit number
QSUM_ALLTIME	Short Integer	Flag that indicates flow rates should be written to BYNODE or QSUM at every time step

Coming soon in version 2.0...

DRT
Field	Type	Description
OBJECTID	OID
IJK	Long Integer	IJK Index
SPID	Long Integer	Stress Period ID
Elevation	Double	Elevation of the drain
Cond	Double	Conductance
IFACE	Long Integer	MODPATH auxiliary variable
Condfact	Double	Factor used to calculate conductance from the parameter value
LayR	Long Integer	Return flow flag
RowR	Long Integer	Row number of the recipient cell
ColR	Long Integer	Column number of the recipient cell
Rfprop	Double	Return-flow proportion
SourceID	Long Integer	HydroID of the feature that the source comes from
LinearScale	Double	Length from the begining of a polyline to the center of the polyline segement within the MODFLOW cell

Array-Based Stress Packages

Two of the more common stress packages are array-based: the Recharge Package (RCH) and the Evapotranspiration Package (EVT). While the individual records are quite similar, both packages require some additional variables. Furthermore, both packages require input that are based on rows and columns, but are not necessarily tied to a particular layer. One approach to handle this would be to store IJ indices. However, it is necessary to do joins with the Cell2D and Node objects to display values. Thus, a IJ field is used with each record where the IJ index for the corresponding cell in the top layer is stored.

Recharge Package (RCH)

The cell-by-cell flow flag (IRCHCB) for the Recharge Package (IRCHCB) is stored in the CBFlags table in the Output control group. The remaining data are stored in the three tables below. The RCHVars table holds the NRCHOP variable (associated with a coded value domain). This variable defines the recharge option. For NRCHOP=1 or 2, a single recharge value (RECH) is stored for each IJ combination. For NRCHOP=3, an additional array of integer values (IRCH) is required. The RECH and IRCH values are stored in the RCHArrays table. The IRCH field will likely be rarely used. The RCHArrayMult table is used to store array multipliers.

RCHVars
Field	Type	Description
OBJECTID	OID
NRCHOP	Short Integer	Recharge option code. RechargeOption coded value domain

RCHArrays
Field	Type	Description
OBJECTID	OID
IJ	Long Integer	IJ Index
SPID	Long Integer	Stress period ID
RECH	Double	Recharge flux
IRCH	Long Integer	Layer number where recharge is applied

RCHArrayMult
Field	Type	Description
OBJECTID	OID
SPID	Long Integer	Stress period ID
AM_RECH	Double	Recharge flux array multiplier
AM_IRCH	Long Integer	IRCH array multiplier

Evapotranspiration Package (EVT)

The Evapotranspiration package is similar to the Recharge Package. The cell-by-cell flow variable (IEVTCB) is stored in the CBFlags table in the Output control group. The remaining data are stored in the three tables below. If NEVTOP=1, the IEVT field is ignored. If NEVTOP=2, the IEVT field is used.

EVTVars
Field	Type	Description
OBJECTID	OID
NEVTOP	Short Integer	Evapotranspiration option code. EvapotranspirationOption coded value domain

EVTArrays
Field	Type	Description
OBJECTID	OID
IJ	Long Integer	IJ Index
SPID	Long Integer	Stress period ID
SURF	Double	Elevation of the ET surface
EVTR	Double	Maximum ET flux
EXPD	Double	ET extinction depth
IEVT	Long Integer	Layer indicator variable

EVTArrayMult
Field	Type	Description
OBJECTID	OID
SPID	Long Integer	Stress period ID
AM_SURF	Double	SURF array multiplier
AM_EVTR	Double	EVTR array multiplier
AM_EXPD	Double	EXPD array multiplier
AM_IEVT	Long Integer	IEVT array multiplier

Evapotranspiration Segments Package (ETS) (v 2.0+)

Coming soon in version 2.0...

ETSVars
Field	Type	Description
OBJECTID	OID
NETSOP	Short Integer	Evapotranspiration option code
NETSEG	Long Integer	Number of segments

ETSArrays
Field	Type	Description
OBJECTID	OID
IJ	Long Integer	IJ Index
SPID	Long Integer	Stress period ID
ETSS	Double	Elevation of the ET surface
ETSR	Double	Maximum ET flux
ETSX	Double	ET extinction depth
IETS	Long Integer	Layer indicator variable

ETSArrayMult
Field	Type	Description
OBJECTID	OID
SPID	Long Integer	Stress period ID
AM_ETSS	Double	ETSS array multiplier
AM_ETSR	Double	ETSR array multiplier
AM_ETSX	Double	ETSX array multiplier
AM_IETS	Long Integer	IETS array multiplier

ETSSegArrays
Field	Type	Description
OBJECTID	OID
IJ	Long Integer	IJ Index
SPID	Long Integer	Stress period ID
SEGID	Long Integer	Segment ID
PXDP	Double	Proportion of the extinction depth
PETM	Double	Proportion of the maximum evapotranspiration rate

ETSSegArrayMult
Field	Type	Description
OBJECTID	OID
SPID	Long Integer	Stress period ID
SEGID	Long Integer	Segment ID
AM_PXDP	Double	PXDP array multiplier
AM_PETM	Double	PETM array multiplier

Stream Package (STR6) (v 2.0+)

Coming soon in version 2.0...

STRVars
Field	Type	Description
OBJECTID	OID
ICALC	Short Integer	Flag for calculating stream stages in reaches
CONST	Double	Constant value used in calculating stream reaches

STRItrib
Field	Type	Description
OBJECTID	OID
Seg	Long Integer	Stream segment
SPID	Long Integer	Stress period ID
Itrib	Long Integer	Segment number for each tributary that flows into a segment

STRIupseg
Field	Type	Description
OBJECTID	OID
Seg	Long Integer	Stream segment
SPID	Long Integer	Stress period ID
Iupseg	Long Integer	Number of upstream segment from which water is diverted

STRReaches
Field	Type	Description
OBJECTID	OID
IJK	Long Integer	IJK Index
SPID	Long Integer	Stress Period ID
Seg	Long Integer	Stream segment
Reach	Long Integer	Stream reach
Flow	Double	Streamflow entering a segment
Stage	Double	Stream stage
Cond	Double	Streambed hydraulic conductance
Sbot	Double	Elevation of the bottom of the streambed
Stop	Double	Elevation of the top of the streambed
Width	Double	Width of the stream channel
Slope	Double	Slope of the stream channel
Rough	Double	Manning's roughness coefficient
Condfact	Double	Factor used to calculate streambed hydraulic conductance
SourceID	Long Integer	HydroID of the feature that the source comes from
LinearScale	Double	Length from the begining of a polyline to the center of the polyline segement within the MODFLOW cell

Streamflow-Routing Package (SFR2) (v 2.0+)

Coming soon in version 2.0...

SFRVars
Field	Type	Description
OBJECTID	OID
CONST	Double	Value used in calculating stream depth for stream reach
DLEAK	Double	Closure tolerance for stream depth for calculating leakage

SFRReaches
Field	Type	Description
OBJECTID	OID
IJK	Long Integer	IJK Index
ISEG	Long Integer	Number of the stream segment this reach is located in
IREACH	Long Integer	Reach number in a stream segment
RCHLEN	Double	Length of channel of the stream reach within this model cell

SFRFlowTab
Field	Type	Description
OBJECTID	OID
SPID	Long Integer	Stress period ID
NSEG	Long Integer	Number of the stream segment
FLOWTAB	Double	Streamflow value
DPTHTAB	Double	Average depth
WDTHTAB	Double	Stream width

SFRSegments
Field	Type	Description
OBJECTID	OID
SPID	Long Integer	Stress period ID
NSEG	Long Integer	Number of the stream segment
ICALC	Short Integer	Used to calculate stream depth in this segment
OUTSEG	Long Integer	Downstream stream segment that receives tributary inflow from the last downstream reach of this segment
IUPSEG	Long Integer	Upstream segment from which water is diverted
IPRIOR	Short Integer	Prioritization system for diversion
NSTRPTS	Short Integer	Dimensions table relating streamflow with stream depth and width
FLOW	Double	Streamflow entering or leaving upstream end of stream segment
RUNOFF	Double	Volumetric rate of the diffuse overland runoff entering stream segment
ETSW	Double	Volumetric rate per unit area of water removed by evapotranspiration
PPTSW	Double	Volumetric rate per unit area of water added by precipitation
ROUGHCH	Double	Manning's roughness coefficient for the channel in all reaches of the segment
ROUGHBK	Double	Manning's roughness for the overbank areas in all reaches of the segment
CDPTH	Double	Coefficient used in relating stream depth to streamflow
FDPTH	Double	Exponent used in relating stream depth to streamflow
AWDTH	Double	Coefficient used in relating stream width to streamflow
BWDTH	Double	Exponent used in relating stream width to streamflow
HCOND1	Double	Hydraulic conductivity of streambed at upstream end of segment
THICKM1	Double	Thickness of streambed at upstream end of segment
ELEVUP	Double	Elevation at top of streambed at upstream end of segment
WIDTH1	Double	Average width of stream channel at upstream end of segment
DEPTH1	Double	Average depth of water in channel at upstream end of segment
HCOND2	Double	Hydraulic conductivity of streambed at downstream end of segment
THICKM2	Double	Thickness of streambed at downstream end of segment
ELEVDN	Double	Elevation at top of streambed at downstream end of segment
WIDTH2	Double	Average width of stream channel at downstream end of segment
DEPTH2	Double	Average depth of water in channel at downstream end of segment

SFRXsect
Field	Type	Description
OBJECTID	OID
SPID	Long Integer	Stress period ID
NSEG	Long Integer	Number of the stream segment
XCPT1	Double	Distance relative to the left bank of the stream channel
ZCPT1	Double	Height relative to the top of the lowest elevation of the streambed (thalweg)
XCPT2	Double	Distance relative to the left bank of the stream channel
ZCPT2	Double	Height relative to the top of the lowest elevation of the streambed (thalweg)
XCPT3	Double	Distance relative to the left bank of the stream channel
ZCPT3	Double	Height relative to the top of the lowest elevation of the streambed (thalweg)
XCPT4	Double	Distance relative to the left bank of the stream channel
ZCPT4	Double	Height relative to the top of the lowest elevation of the streambed (thalweg)
XCPT5	Double	Distance relative to the left bank of the stream channel
ZCPT5	Double	Height relative to the top of the lowest elevation of the streambed (thalweg)
XCPT6	Double	Distance relative to the left bank of the stream channel
ZCPT6	Double	Height relative to the top of the lowest elevation of the streambed (thalweg)
XCPT7	Double	Distance relative to the left bank of the stream channel
ZCPT7	Double	Height relative to the top of the lowest elevation of the streambed (thalweg)
XCPT8	Double	Distance relative to the left bank of the stream channel
ZCPT8	Double	Height relative to the top of the lowest elevation of the streambed (thalweg)

GAG Package (v 2.0+)

Coming soon in version 2.0...

GAGSFR
Field	Type	Description
OBJECTID	OID
GAGESEG	Long Integer	Stream segment number where gage is located
GAGERCH	Long Integer	Stream reach number where gage is located
UNIT	Short Integer	Unit number of output file for this gage
OUTTYPE	Short Integer	Flag for type of expanded listing desired in output file

GAGLAK
Field	Type	Description
OBJECTID	OID
LAKE	Long Integer	Lake number of the lake where the gage is located
UNIT	Short Integer	Unit number for output file
OUTTYPE	Short Integer	Code for type of expanded listing desired in output file

LAK3 Package (v 2.0+)

Coming soon in version 2.0... MOC3D properties unsupported.

LAKVars
Field	Type	Description
OBJECTID	OID
THETA	Double	Explicit, semi-implicit, or implicit solution for lake stages
NSSITR	Short Integer	Maximum number of iterations for Newton’s method solution for equilibrium lake stages in each MODFLOW iteration for steady-state aquifer head solution
SSCNCR	Double	Convergence criterion for equilibrium lake stage solution by Newton’s method

LAKArrays
Field	Type	Description
OBJECTID	OID
IJK	Long Integer	IJK Index
SPID	Long Integer	Stress period ID
LKARR	Long Integer	Lake array value
BDLKNC	Double	Lakebed leakance value

LAKStages
Field	Type	Description
OBJECTID	OID
LakeID	Long Integer	Lake ID
STAGES	Double	Initial stage of lake at the beginning of the run
SSMN	Double	Minimum stage allowed for lake in steady-state solution
SSMX	Double	Maximum stage allowed for lake in steady-state solution

LAKSublakes
Field	Type	Description
OBJECTID	OID
SPID	Long Integer	Stress period ID
SystemID	Long Integer	Multi-lake system ID
ISUB	Long Integer	Identification numbers of the sublakes in the sublake system
SILLVT	Double	Sill elevation that determines whether the center lake is connected with a given sublake

LAKRates
Field	Type	Description
OBJECTID	OID
SPID	Long Integer	Stress period ID
LakeID	Long Integer	Lake ID
PRCPLK	Double	Rate of precipitation per unit area at the surface of lake
EVAPLK	Double	Rate of evaporation per unit area from the surface of lake
RNF	Double	Overland runoff from an adjacent watershed entering lake
WTHDRW	Double	Volumetric rate, or flux, of water removal from lake by means other than rainfall, evaporation, surface outflow, or ground-water seepage
SSMN	Double	Minimum stage allowed for lake in steady-state solution
SSMX	Double	Maximum stage allowed for lake in steady-state solution

Unsaturated Zone Flow (UZF) Package (v 2.0+)

Coming soon in version 2.0...

UZFVars
Field	Type	Description
OBJECTID	OID
NUZTOP	Short Integer	Flag defining recharge to and discharge from cells
IUZFOPT	Short Integer	See MODFLOW documentation
IRUNFLG	Short Integer	Flag to route to stream segments or lakes
IETFLG	Short Integer	Flag to simulate evapotranspiration
NTRAIL2	Long Integer	Number of trailing waves
NSETS2	Long Integer	Number of wave sets
NUZGAG	Long Integer	Number of cells for printing water budget and content
SURFDEP	Double	Average height of undulations

UZFArrays
Field	Type	Description
OBJECTID	OID
IJ	Long Integer	IJ Index
IUZFBND	Long Integer	Aerial extent of active model
IRUNBND	Long Integer	Define the stream segments
VKS	Double	Saturated vertical hydraulic conductivity of the unsaturated zone
EPS	Double	Brooks-Corey epsilon of the unsaturated zone
THTS	Double	Saturated water content of the unsaturated zone
THTI	Double	Initial water content for each vertical column of cells

UZFArrayMult
Field	Type	Description
OBJECTID	OID
AM_IUZFBND	Long Integer	IUZFBND array multiplier
AM_IRUNBND	Long Integer	IRUNBND array multiplier
AM_VKS	Double	VKS array multiplier
AM_EPS	Double	EPS array multiplier
AM_THTS	Double	THTS array multiplier
AM_THTI	Double	THTI array multiplier

UZFGages
Field	Type	Description
OBJECTID	OID
IUZROW	Long Integer	Row number of the cell
IUZCOL	Long Integer	Column number of the cell
IFTUNIT	Long Integer	Unit number of the output file
IUZOPT	Long Integer	Type of expanded listing desired in the output file

UZFStressArrays
Field	Type	Description
OBJECTID	OID
IJ	Long Integer	IJ Index
SPID	Long Integer	Stress period ID
FINF	Double	Infiltration rate
PET	Double	ET demand rate
EXTDP	Double	ET extinction depth
EXTWC	Double	Extinction water content

UZFStressArrayMult
Field	Type	Description
OBJECTID	OID
SPID	Long Integer	Stress period ID
AM_FINF	Double	FINF array multiplier
AM_PET	Double	PET array multiplier
AM_EXTDP	Double	EXTDP array multiplier
AM_EXTWC	Double	EXTWC array multiplier
NUZF1	Short Integer	Flag for reusing or reading infiltration rates
NUZF2	Short Integer	Flag for reusing or reading ET demand rates
NUZF3	Short Integer	Flag for reusing or reading ET extinction depths
NUZF4	Short Integer	Flag for reusing or reading the extinction water content

Solver Packages

Representing solver package input in the MDM is a fairly simple process. None of the packages require any type of array- or list-based input; all input is in the form of a set of variables. For each solver package there is one table with one field for each of the variables used in the package. Each table contains only one record.

SIP
Field	Type	Description
OBJECTID	OID
MXITER	Long Integer	Max iterations per time step
NPARM	Long Integer	Number of iteration variables to be used
ACCL	Double	Acceleration variable
HCLOSE	Double	Head change criterion
IPCALC	Short Integer	Flag indicating where seed comes from
WSEED	Double	Seed for calculating iteration variables
IPRSIP	Long Integer	Printout interval

GMG
Field	Type	Description
OBJECTID	OID
RCLOSE	Double	Residual convergence criterion for the inner iteration
IITER	Long Integer	Maximum number of PCG iterations for each linear solution
HCLOSE	Double	Head change convergence criterion for nonlinear problems
MXITER	Long Integer	Maximum number of outer iterations
DAMP	Double	Value of the damping parameter
IADAMP	Short Integer	A flag that controls adaptive damping
IOUTGMG	Short Integer	Flag that controls output. IOUTGMGType coded value domain
IUNITMHC (optional)	Short Integer	IUNITMHC is a flag and a unit number, which controls output of maximum head change values
ISM	Short Integer	Flag that controls the type of smoother used in the multigrid preconditioner
ISC	Short Integer	Flag that controls semicoarsening in the multigrid preconditioner. ISCType coded value domain
DUP (optional)	Double	the maximum damping value that should be applied at any iteration when the solver is not oscillating
DLOW(optional)	Double	the minimum damping value to be generated by the adaptive-damping procedure
CHGLIMIT (optional)	Double	the maximum allowed head change at any cell between outer iterations; it has units of length
RELAX	Double	Relaxation parameter for the ILU preconditioned conjugate gradient method

LMG
Field	Type	Description
OBJECTID	OID
STOR1	Double	Variable controlling the amount of storage allocated
STOR2	Double	Variable controlling the amount of storage allocated
STOR3	Double	Variable controlling the amount of storage allocated
ICG	Short Integer	Variable controlling whether or not conjugate gradient iterations are used at the end of each multigrid cycle
MXITER	Long Integer	Maximum number of iterations
MXCYC	Long Integer	Maximum number of cycles allowed per call to the solver
BCLOSE	Double	Budget closure criterion for the scaled L2 norm of the matrix equations
DAMP	Double	Damping/accelerating parameter identical to ACCL of the DE4 solver
IOUTAMG	Short Integer	Flag that controls the information printed each time step from the solver to the LIST output file. IOUTAMGType coded value domain
DUP	Double	Maximum value of DAMP that should be applied at any iteration
DLOW	Double	Minimum value of DAMP that should be applied at any iteration

PCG
Field	Type	Description
OBJECTID	OID
MXITER	Long Integer	Max number of outer iterations
ITER1	Long Integer	Number of inner iterations
NPCOND	Short Integer	Flag used to select matrix conditioning method
HCLOSE	Double	Head change criterion
RCLOSE	Double	Residual criterion
RELAX	Double	Relaxation parameter
NBPOL	Short Integer	Flag indicating whether estimate on upper bound on maximum eigenvalue is 2.0 or calculated
IPRPCG	Long Integer	Printout interval
MUTPCG	Short Integer	Flag that controls printing of convergence information. MUTPCGType coded value domain
DAMP	Double	Damping factor

DE4
Field	Type	Description
OBJECTID	OID
ITMX	Long Integer	Max number of iterations each time step
MXUP	Long Integer	Max number of equations in upper part of equations to be solved
MXLOW	Long Integer	Max number of equations in lower part of equations to be solved
MXBW	Long Integer	Maximum band width plus 1
IFREQ	Short Integer	Flag indicating the frequency at which coefficients in [A] change
MUTD4	Short Integer	Flag that indicates the quantity of information that is printed
ACCL	Double	Multiplier for computed head change for each iteration
HCLOSE	Double	Head change closure criterion
IPRD4	Long Integer	Time step interval for printing convergence information

SOR
Field	Type	Description
OBJECTID	OID
MXITER	Long Integer	Max iterations per time step
ACCL	Double	Acceleration variable
HCLOSE	Double	Head change criterion
IPRSOR	Long Integer	Printout interval

Parameters

Beginning with MODFLOW 2000, the MODFLOW input files allow for the definition of parameters. Parameter definitions can be complex and representing parameters in a GIS database is challenging. The following design is an attempt to allow complex parameter definitions, yet provide a simple option for the most routine cases. The tables are related in multiple ways but those relationships are not shown here. Refer to the diagram.

Params
Field	Type	Description
OBJECTID	OID
ParamID	Long Integer	Parameter ID
PARNAM	Text	Parameter name
PARTYPE	Text	Standard MODFLOW parameter type from PARTYPE coded value domain. If "Custom", then the TableCode and FieldCode fields are used to define the parameter type.
TableCode	Text	The name of the table containing the parameter. Ignored unless PARTYPE is "Custom".
FieldCode	Text	The name of the field in the table identified by TableCode containing the parameter. Ignored unless PARTYPE is "Custom".
Parval	Double	Parameter value used for forward runs
Keyval	Double	Key value in the field identified by PARTYPE (or TableCode and FieldCode) that identifies the location of the parameter. The value should be one that does not normally occur in the data (e.g. -99999)
B	Double	"Starting" value used in sensitivity and inverse runs
BL	Double	Min parameter value
BU	Double	Max parameter value
BSCAL	Double	Scaling factor for the SEN and PES processes.
LN	Short Integer	Flag indicating whether or not the parameter should be log-transformed during the SEN and PES processes
ISENS	Short Integer	Flag indicating whether or not the parameter should be analyzed during SEN or PES processes
LogInterp	Short Integer	Flag whether or not to use log interpolation for pilot points
LogMinVal	Double	Minimum value when using log interpolation for pilot points
Tied	Text	Used by PEST. The name of another parameter used to link one parameter to another. The tied parameter is automatically adjusted along with the parent parameter by multiplying the parent parameter value by the Parval value of the tied parameter.
Source	Short Integer	Flag indicating how data values for the parameter will be populated. ParamSource coded value domain.

PilotPts
Field	Type	Description
OBJECTID	OID
ParamID	Long Integer	Parameter ID from Params table
PointName	Text	Point name
Parval	Double	Parameter value used for forward runs
B	Double	"Starting" value used in sensitivity and inverse runs
ISENS	Short Integer	Flag indicating whether or not the parameter should be analyzed during SEN or PES processes
MultID	Long Integer	Multiplier ID from Multipliers table
SourceID	Long Integer	HydroID of the feature that the record comes from

ParInstSP
Field	Type	Description
OBJECTID	OID
ParInstID	Long Integer	Parameter Instance ID from ParInstances table
SPID	Long Integer	Stress period ID from StressPeriods table

ParInstances
Field	Type	Description
OBJECTID	OID
ParInstID	Long Integer	Parameter instance ID
InstName	Text	Instance name
ParamID	Long Integer	Parameter ID from Params table

Clusters
Field	Type	Description
OBJECTID	OID
ClusterID	Long Integer	Cluster ID
ParInstID	Long Integer	Parameter Instance ID from ParInstances table
Layer	Long Integer	Layer
ZoneID	Long Integer	Zone ID from Zones table
MultID	Long Integer	Multiplier ID from Multipliers table
HGUNAME	Text	Hydrogeologic Unit Name

IZ
Field	Type	Description
OBJECTID	OID
ClusterID	Long Integer	Cluster ID from Clusters table
IZ	Long Integer	Zone code

ZoneNames
Field	Type	Description
OBJECTID	OID
ZoneID	Long Integer	Zone ID from Zones table
ZoneName	Text	Zone name
ArrayMult	Long Integer	Array multiplier

Zones
Field	Type	Description
OBJECTID	OID
ZoneID	Long Integer	Zone ID
IJ	Long Integer	IJ Index
IZON	Long Integer	Value stored at cell

Multipliers
Field	Type	Description
OBJECTID	OID
MultID	Long Integer	Multiplier ID
IJ	Long Integer	IJ Index
RMLT	Double	Array multiplier value

MultNames
Field	Type	Description
OBJECTID	OID
MultID	Long Integer	Multiplier ID from Multipliers table
MultName	Text	Multiplier Name
ArrayMult	Long Integer	Array multiplier
Function	Text	Simple mathematical operators used to combine multiplier arrays

The main table is the Params table. Parameters can be classified into two groups: 1) list-based parameters (well, drain, river, etc.) 2) array-based parameters (K, Ss, Sy, recharge, et, etc.). The strategy for managing the two types of parameters differs slightly. Another type of parameter exists that is non-native to MODFLOW: pilot points associated with array-based parameters.

List-Based Parameters

In the input files for the list-based stress packages, parameters are defined by providing a list of parameter definitions at the top of the file, above the main list of stress items and including a list of parameter names in the main list with each stress period group. Since this approach includes some redundancy and since it is difficult to directly duplicate in a database setting, a different strategy is used based on the concept of “key values”. The Keyval field in the Params table represents a value in the identified data column that identifies the location of the parameter. A value for the Keyval field should be selected such that it would not normally occur in the data column. For example, if the Keyval=-800 is used to identify river conductance, a query could be performed on this value to find all river stress objects with this value. The tools developed for the MDM are able to use this type of query to write out the MODFLOW files in the native format. Furthermore, a similar tool is able to read a MODFLOW package file in the native format and convert it to the Keyval format when importing the file. Using the Keyval approach also simplifies the process of parameterizing the model input in the GIS. The user simply assigns selected key values in the appropriate fields using standard editing tools. No special or additional tools are required.

For parameters associated with conductance values, the Condfact field is used to scale the parameter value for use with the conductance term. A similar approach is used with the Hydchr and Factor terms in the HFB table.

Array-Based Parameters

Array-based parameters are more complicated than list-based parameters. Array-based parameters can be defined in three ways: using key values, using clusters, and using pilot points.

Key Values. The Keyval field is used to identify the records in the data column corresponding to the parameter locations, similar to the process described above for list-based parameters. For most cases, this simple approach is sufficient. The only case where it is not sufficient is where you want to define a parameter that uses multiple zone arrays which cover distinct portions of the grid. When using the Key Value approach, only the Params table is necessary.

Clusters. The Clusters approach mimics the method used in the MODFLOW input files. Clusters are associated with Parameter Instances, even if a parameter only has a single instance. Clusters are defined using zone arrays and multiplier arrays. All of the tables, besides the Params and Pilot points tables, exist solely to support the clusters approach.

It should be noted that the entries in the Multipliers and Zones tables are referenced by IJ index. These arrays stored in this table are defined on a layer-by-layer basis with respect to the MODFLOW grid. Thus, each entry in the array is associated with an IJ index, independent of model layer (K). Going with an IJ index as opposed to two separate I, J fields simplifies the process of joining the tables with the Cell2D features. The IJ index for a particular entry corresponds to the cell in the top layer of the grid, regardless of which layer the Mulplier or Zone array is associated with. A GP tool exists that creates a temporary copy of the table and populates the table with I and J fields when needed.

Transient Array-Based Parameters

Transient array-based parameters are used with the Recharge and ET packages. In this case, MODFLOW utilizes “parameter instances” to define the parameters in the input file. Each parameter can be defined by multiple instances. Each parameter instance has a name and one or more clusters. Each parameter instance/cluster combination is linked to one or more stress periods. The ParInstances table contains the list of parameter instances.

Pilot Points

Pilot points allow one to define a distribution of values within an array by specifying parameter values at selected XY locations (pilot points) and interpolating to a zone of cells within a model layer. The Keyval field is used to identify which cells in the specified array are to be included in the pilot point interpolation. The PilotPts table is used to store the list of pilot points. Pilot points are organized into groups using the ParamID. The SourceID field could be used to represent the HydroID field of the associated point in a point layer from which the pilot point set was created. The Parval, and ISENS fields supersede the similarly named fields in the Params table. The weights associated with each pilot point are defined using a multiplier array. A tool will exist that displays the final paramter values based on the pilot point data.

Observations

Beginning with MODFLOW 2000, an Observation Process was provided in MODFLOW that allows the user to input head and flow observations. Simulated equivalents are then automatically computed by MODFLOW, from which residuals can be computed. This is an essential part of any type of calibration exercise. Both head and flow observations can be transient and head observations are allowed to span multiple layers. Flow observations are supported for the GHB, DRN, RIV, and CHD packages. This list will be expanded as more stress packages are added to the data model.

OBSVars
Field	Type	Description
OBJECTID	OID
OUTNAM	Text	Base file name for the output for the observation process
ISCALS	Long Integer	Controls printing of the observation-sensitivity tables
TOMULTH	Double	Time-offset multiplier for head observations
EVH	Double	Input error variance multiplier for head observations
IUHOBSV	Long Integer	File unit for saving observation data in a file
HOBDRY	Double	Value of the simulated equivalent when the observation is omitted because a cell is dry
TOMULTGB	Double	Time-offset multiplier for general-head-boundary observations
EVFGB	Double	Error variance multiplier for observations represented by the General-Head Boundary Package
IUGBOBSV	Long Integer	File unit for saving observation data in a file
TOMULTDR	Double	Time-offset multiplier for drain observations
EVFDR	Double	Error variance multiplier for observations represented by the Drain Package
IUDROBSV	Long Integer	File unit for saving observation data in a file
TOMULTRV	Double	Time-offset multiplier for river observations
EVFRV	Double	Error variance multiplier for river observations
IURVOBSV	Long Integer	File unit for saving observation data in a file
TOMULTCH	Double	Time-offset multiplier for constant-head flow observations
EVFCH	Double	Error variance multiplier for constant-head flow observations
IUCHOBSV	Long Integer	File unit for saving observation data in a file
TOMULTST	Double	Time-offset multiplier for stream observations
EVFST	Double	Error variance multiplier for stream observations
IUSTOBSV	Long Integer	File unit for saving observation data in a file
TOMULTDT	Double	Time-offset multiplier for drain-return observations
EVFDT	Double	Error variance multiplier for drain-return observations

HOB
Field	Type	Description
OBJECTID	OID
HOBID	Long Integer	Head observation ID
OBSNAM	Text	String used to identify the observation
IJ	Long Integer	IJ index of the cell in which the head observation is located
ROFF	Double	Row offset used to locate the observation within a finite-difference cell
COFF	Double	Column offset used to locate the observation within a finite-difference cell
ITT	Short Integer	Flag whether head or changes in head are to be used as observations

HOBLayers
Field	Type	Description
OBJECTID	OID
HOBID	Long Integer	Head observation ID from HOB table
Layer	Long Integer	Layer
PR	Double	Proportion of the simulated hydraulic head in layer used to calculate simulated multilayer head

HOBTimes
Field	Type	Description
OBJECTID	OID
HOBID	Long Integer	Head observation ID from HOB table
OBSNAM	Text	Observation name
IREFSP	Long Integer	Stress period to which the observation time is referenced
TOFFSET	Double	Time from beginning of stress period IREFSP to the time of the observation
HOBS	Double	Observed hydraulic head
HSIM	Double	Simulated hydraulic head (computed head)
STATh	Double	Value from which the weight is calculated if the observation is head
STATdd	Double	Value from which the weight is calculated if the observation is the temporal change in head
STATFLAG	Short Integer	STATFLAG coded value domain
PLOTSYMBOL	Long Integer	An integer intended to control the symbols used to plot data

FLOB
Field	Type	Description
OBJECTID	OID
FLOBID	Long Integer	Flow observation ID
FLOBType	Text	FLOBType coded value domain
OBSNAM	Text	Observation name
IREFSP	Long Integer	Stress period to which the observation time is referenced
TOFFSET	Double	Time from beginning of stress period IREFSP to the time of the observation
HOBS	Double	Observed hydraulic head
HSIM	Double	Simulated hydraulic head (computed head)
STATISTIC	Double	Value from which the weight for the observation is calculated
STATFLAG	Short Integer	STATFLAG coded value domain
PLOTSYMBOL	Long Integer	An integer intended to control the symbols used to plot data

FLOBFactors
Field	Type	Description
OBJECTID	OID
FLOBID	Long Integer	Flow observation ID from FLOB table
IJK	Long Integer	IJK Index
Factor	Double	Portion of the simulated gain or loss in this cell that is included in the total simulated gain or loss for this cell group

The OBSVars table is used to store individual variables related to observations. The OUTNAM and ISCALS variables are written to the OBS file. The TOMULT* and EV* variables are written to the HOBS, GBOB, DROB, RVOB, and CHOB files.

The HOB table is used to store the locations of the head observations. The HOBLayers table is used to store a list of layers associated with each observation. In the MODFLOW input file, a list of layers is only provided when there are multiple layers. However, the table is used for all cases (even when there is only one layer) in the interest of simplicity. The layers are stored in the HOBLayers table. The HOBTimes table is used to store the head measurements. For each head observation location, there may be multiple head observations at different points in time. Once again, the table is used even for cases with a single value in the interest of simplicity.

The FLOB table is used to store the flow observations. Each record in this table corresponds to an observation at a particular time defined by the IRESFP and TOFFSET variables. All types of flow observations are stored in the same table and are distinguished using the FLOBType field. The FLOBFactors table is used to identify the entries in the associated stress package table that correspond to the given flow observation. The manner in which the factors are associated with the entries in the stress package file follows the same method as outlined in the MODFLOW file formats. This method relies on the ordering of the items in the list. As a result, it typically makes most sense for the tools associated with these packages to build the entries for both the stress package tables and the flow observations tables at the same time.

The variance-covariance weight matrix option (WTQ array) is not supported for flow observations in this version of the MDM.

SEN and PES Processes

The tables associated with the SEN and PES processes are shown below. The data associated with the Sensitivity process are stored in two places: 1) the parameter variables (BSCAL, LN, and ISENS) are stored in the Params table, and 2) the remaining variables are stored in the SEN table. The PES data are all stored in the PES table. Lines 5-10 in the PES file are not supported. It is assumed that NPNG=0, IPR=0, and MPR=0.

SEN
Field	Type	Description
OBJECTID	OID
ISENALL	Short Integer	Flag that can override values of ISENS and can deactivate PES process
IUHEAD	Short Integer	Flag that allows user to choose between using scratch files or memory for storing grid sensitivities
IPRINTS	Short Integer	Flag indicating how saving and printing of sensitivity arrays are controlled
ISENSU	Short Integer	Flag that controls whether sensitivity arrays are to be saved and, if so, to what file.
ISENPU	Short Integer	Flag identifying whether sensitivity arrays are to be printed and, if so, to what file.
ISENFM	Short Integer	Code indicating the format for printing sensitivity arrays.

PES
Field	Type	Description
OBJECTID	OID
MAXITER	Double	See MODFLOW documentation
MAXCHANGE	Double	See MODFLOW documentation
TOL	Double	See MODFLOW documentation
SOSC	Double	See MODFLOW documentation
IBEFLG	Short Integer	See MODFLOW documentation
IYCFLG	Short Integer	See MODFLOW documentation
IOSTAR	Short Integer	See MODFLOW documentation
NOPT	Short Integer	See MODFLOW documentation
NFIT	Long Integer	See MODFLOW documentation
SOSR	Double	See MODFLOW documentation
RMAR	Double	See MODFLOW documentation
RMARM	Double	See MODFLOW documentation
IAP	Short Integer	See MODFLOW documentation
IPRCOV	Short Integer	See MODFLOW documentation
IPRINT	Short Integer	See MODFLOW documentation
LPRINT	Short Integer	See MODFLOW documentation
CSA	Double	See MODFLOW documentation
FCONV	Double	See MODFLOW documentation
LASTX	Double	See MODFLOW documentation

Output

Native MODFLOW output consists of four general types:

1. Head and drawdown files. Binary files listing the computed head and drawdown values grouped by time step (indexed by stress period and time step number). The drawdown file represents the computed head minus the starting head.
2. Flow budget files. Binary files listing the cell-by-cell flow terms grouped by time step. This includes three flow numbers for each cell representing flow in each of the axis directions. It also includes set of values for each stress type (RIV, DRN, WEL, etc.).
3. Head and flow file (HFF). This is the binary file produced by MODFLOW for use with the MT3D family of contaminant transport codes. It includes both the head and flow data.
4. Miscellaneous text output files. MODFLOW produces various text output files including the LST and GLOBAL files.

OutputFiles
Field	Type	Description
OBJECTID	OID
FileType	Text	"Head", "Drawdown", "CCF" etc.
Description	Text	Optional longer helpful description
Format	Text	File format such as ASCII or binary. OutputFormat coded value domain
Compress	Text	Flag indicating if the file is compressed and, if so, what type of compression is used. "", "zip", "tar" etc. Only used if the file is stored in the File field as a blob
File	Blob	The file stored as a Blob, or null if the file is not stored in the geodatabase
Path	Text	Path to the file on disk, or ""

OutputTime
Field	Type	Description
OBJECTID	OID
TimeID	Long Integer	Time ID
SPNum	Long Integer	Stress period number from output file - not SPID from StressPeriods table
TSNum	Long Integer	Time step number from output file
TotalTime	Double	Time from 0 to this time
PeriodTime	Double	Time from beginning of this stress period to this time
AbsoluteTime	Date	Date/Time of this time

OutputFlow
Field	Type	Description
OBJECTID	OID
TimeID	Long Integer	Time ID from OutputTime table
IJK	Long Integer	IJK Index
FlowType	Short Integer	Flow type. OutputFlowType coded value domain
Flow	Double	Flow value

OutputHead
Field	Type	Description
OBJECTID	OID
TimeID	Long Integer	Time ID from OutputTime table
IJK	Long Integer	IJK Index
Head	Double	Head value

OutputDrawdown
Field	Type	Description
OBJECTID	OID
TimeID	Long Integer	Time ID from OutputTime table
IJK	Long Integer	IJK Index
Drawdown	Double	Drawdown value

The OutputHead, OutputDrawdown and OutputFlow tables are used to store the head, drawdown, and cell-to-cell flow output for each cell for each time step. The flow values come from the compact budget file, which also contains flow values for the stress packages.

Since the output for a single MODFLOW simulation can be quite large, it may not be practical or desirable to keep the OutputHead, OutputDrawdown and OutputFlow tables populated at all times. In such cases, a geo-processing tool could be used to parse through the files listed in the OutputFiles table to populate temporary tables for the head and flow solution. Alternatively, geo-processing tools for post-processing could be designed to read directly from the binary MODFLOW output files.

Coded Value Domains

FileType
Field type: Text
Code	Name
GLOBAL	GLOBAL
LIST	LIST
DIS	DIS
MULT	MULT
ZONE	ZONE
BAS6	BAS6
OC	OC
BCF6	BCF6
LPF	LPF
HFB6	HFB6
RCH	RCH
RIV	RIV
WEL	WEL
DRN	DRN
GHB	GHB
EVT	EVT
CHD	CHD
SIP	SIP
SOR	SOR
PCG	PCG
DE4	DE4
IBS	IBS
LMG	LMG
GAGE	GAGE
ETS	ETS
DRT	DRT
FHB	FHB
HYD	HYD
RES	RES
MNW	MNW
DAF	DAF
DAFG	DAFG
STR	STR
KDEP	KDEP
LVDA	LVDA
SUB	SUB
LMT6	LMT6
OBS	OBS
ADV2	ADV2
CHOB	CHOB
DROB	DROB
DTOB	DTOB
GBOB	GBOB
HOB	HOB
RVOB	RVOB
STOB	STOB
SEN	SEN
PES	PES
DATA(BINARY)	DATA(BINARY)
DATA	DATA
DATAGLO(BINARY)	DATAGLO(BINARY)
DATAGLO	DATAGLO

TrueFalse
Field type: Short Integer
Code	Name
0	False
1	True

TimeUnit
Field type: Short Integer
Code	Name
0	undefined (0)
1	seconds (1)
2	minutes (2)
3	hours (3)
4	days (4)
5	years (5)

LengthUnit
Field type: Short Integer
Code	Name
0	undefined (0)
1	feet (1)
2	meters (2)
3	centimeters (3)

Direction
Field type: Text
Code	Name
R	Row
C	Column

SteadyState
Field type: Text
Code	Name
SS	SteadyState
TR	Transient

OCVarsFileType
Field type: Short Integer
Code	Name
1	11G10.3
2	9G13.6
3	15F7.1
4	15F7.2
5	15F7.3
6	15F7.4
7	20F5.0
8	20F5.1
9	20F5.2
10	20F5.3
11	20F5.4
12	10G11.4
13	10F6.0
14	10F6.1
15	10F6.2
16	10F6.3
17	10F6.4
18	10F6.5
19	5G12.5
20	6G11.4
21	7G9.2

BCFMean
Field type: Short Integer
Code	Name
0	Harmonic mean (0)
1	Arithmetic mean (1)
2	Logarithmic mean (2)
3	Arith t X log(k) (3)

BCFLayerType
Field type: Short Integer
Code	Name
0	Confined (0)
1	Unconfined (1)
2	Conf/Unconf (2)
3	Conf/Unconf (3)

LPFLayerType
Field type: Short Integer
Code	Name
0	Confined (0)
1	Convertible (1)

LPFMean
Field type: Short Integer
Code	Name
0	Harmonic mean (0)
1	Arithmetic mean (1)
2	Logarithmic mean (2)
3	Arith t X log(k) (3)

RechargeOption
Field type: Short Integer
Code	Name
1	Top (1)
2	Specified (2)
3	Highest Active (3)

EvapotranspirationOption
Field type: Short Integer
Code	Name
1	Top (1)
2	Specified (2)

MUTPCGType
Field type: Short Integer
Code	Name
0	Print max head change and residual each iteration
1	Print total number of iterations
2	No printing
3	Print only if convergence fails

IOUTAMGType
Field type: Short Integer
Code	Name
0	No printing
1	Scaling and residuals
2	Scaling, residuals, storage, time
3	Solver, scaling, residuals, storage, time

ISCType
Field type: Short Integer
Code	Name
0	Rows, columns, layers
1	Rows, columns
2	Columns, layers
3	Rows, layers
4	No coarsening

IOUTGMGType
Field type: Short Integer
Code	Name
0	Solver inputs
1	Linear solve
2	Convergence history
3	Linear solve terminal output
4	Convergence history terminal output

PARTYPE
Field type: Text
Code	Name
HK	HK
HANI	HANI
VK	VK
VANI	VANI
SS	SS
SY	SY
VKCB	VKCB
SYTP	SYTP
HFB	HFB
RIV	RIV
RCH	RCH
Q	Q
DRN	DRN
EVT	EVT
GHB	GHB
CHD	CHD
STR	STR
DRT	DRT
ETS	ETS
SFR	SFR
Custom	Custom

ParamSource
Field type: Short Integer
Code	Name
0	Parval
1	Pilot Points
2	Clusters

STATFLAG
Field type: Short Integer
Code	Name
0	Variance [L^2] (0)
1	Std. Dev. [L] (1)
2	Coeff. of variation [--] (2)

FLOBType
Field type: Text
Code	Name
GBOB	GBOB
DROB	DROB
RVOB	RVOB
CHOB	CHOB
STOB	STOB
DTOB	DTOB

OutputFormat
Field type: Text
Code	Name
ASCII	ASCII
binary	binary

May add others in future, like XML, HDF5 etc.

OutputFlowType
Field type: Short Integer
Code	Name
0	Right
1	Front
2	Lower
3	Wells
4	Drains
5	Rivers
6	ET
7	General Heads
8	Recharge
9	Constant Heads
10	Streams
11	Storage
12	Lakes

Managing Multiple Model Runs

In a typical modeling project, dozens, if not hundreds or thousands of model runs are performed. Each run represents a different combination of model inputs and/or grid configuration. While not all of these runs need to be archived, it is useful to archive many of the model runs for future reference or so that one can revisit and update an earlier model run. With the MDM described in this document, model runs could be archived simply by copying the entire simulation feature dataset (including Cell2D, Node, and the MDM tables) for each model run. Each simulation feature data set could be stored in a separate geodatabase to simplify the duplication process.

While duplicating a geodatabase is a simple and effective strategy, it could result in massive storage requirements for large models. Two models runs could be identical except for a single record in a table and yet the entire geodatabase would be duplicated. Fortunately, ArcGIS provides a powerful tool for managing multiple model runs without wasteful duplication of data. This tool is called “versioning” and is described in the following documents:

http://webhelp.esri.com/arcgisdesktop/9.2/index.cfm?TopicName=Understanding_versioning http://webhelp.esri.com/arcgisdesktop/9.2/index.cfm?TopicName=What_is_ArcSDE%3F http://webhelp.esri.com/arcgisdesktop/9.2/index.cfm?TopicName=An_overview_of_the_geodatabase_schema_in_SQL_Server

With a versioning strategy, a modeler would first set up a complete model and then turn on versioning and create a new “version”. This initiates the use of a pair of “adds” and “deletes” tables where changes to the database are recorded. In other words, any modifications made to the database by the user are recorded internally in the adds and deletes tables. However, the user continues to directly interact with and edit the database in a normal fashion. The layering of the adds and deletes tables is performed automatically and hidden from the user. Multiple versions can be created and the user can switch back and forth between versions using a simple interface. Versions can be deleted or merged with the original version as desired.

Other Model Types

It is anticipated that in the future the MDM will be expanded to include other models and utilities in the MODFLOW family including MODPATH, ZONEBUDGET, MT3DMS, RT3D, SEAM3D, PHT3D, SEAWAT, etc. Each of these models will share some data with MODFLOW but will require additional tables. As the new models are added to the MDM, the shared tables will be identified and names selected for the new tables that avoid confusion. Linkages will also be identified between models when appropriate.

Limitations

In order to model MODFLOW data in the form of a relational database some simplifications were required. Here is a brief summary of the main limitations and unsupported features of the current version of the MDM.

• Only MODFLOW 2000 and 2005 supported (not MODFLOW-LGR etc).
• Several packages aren't supported (STR, SFR2 etc.).
• Some of the options in the Output Control package aren't supported.
• The variance-covariance weight matrix option (WTQ array) is not supported for flow observations.
• Lines 5-10 in the PES file are not supported and it is assumed that NPNG=0, IPR=0, and MPR=0.
• LAK3 package (v2.0+) - Stages table does not include constituent data for use with MOC3D. i.e., CLAKE(1..NSOL). LAKRates does not include MOC3D solute concentrations.

Versions

• 1.0 - The initial model as it was when MODFLOW Analyst became available in February, 2009
• 2.0 - Include LAK3, STR1, SFR2, HUF2, MNW1 packages, and support for MODFLOW 2005.

See also

• Arc Hydro Groundwater Data Model