1. GLOBAL PROCESS DATA
Name File: Contains the names of most input and output files and controls the parts of the model program that are active.
Discretization File: Contains data that defines the physical size of the finite difference grid and the fundamental components of time discretization.
Multiplier File: Contains data to define multiplier arrays.
Zone File: Contains data to define zone arrays.
Global Processes

2. NAME FILE Contains the names of most input and output files and controls the parts of the model program that are active.
Example Name File twri.nam
For each simulation, in free format
Ftype Nunit Fname
Ftype—is the file type with special character values. It is not case specific.
Nunit—is the Fortran unit to be used when reading from or writing to a file (1-95).
Fname—is the name of the file. Pathnames maybe specified.
Name File is read on unit 99. Comments are indicated by the # character in column 1.
Global Processes

3. FTYPE
Global for the global listing file—if this type is not present, the LIST file is used for global listing as well as for the forward run listing
List for the forward run listing—if this file is not present, the Global file isused for the forward run listing as well as for the global listing
The name file must always include a record that specifies GLOBAL or LIST for Ftype.
Both record can be included, and if so, the GLOBAL record must be the first non-comment record and LIST the second non-comment record.
If only one of these records is included, it must be the first non-comment record
Global Processes

4. FTYPE CONTINUED Global Process Files DIS Discretization
MULT Multiplier Array
ZONE Zone Array
GWF Process Packages
BAS6 Basic
OC Output Control
BCF6 Block-Centered Flow
LPF Layer Property Flow
HFB6 Horizontal Flow Barrier
RCH Recharge
RIV River
WEL Well
DRN Drain
GHB General-Head Boundary
EVT Evapotranspiration
STR Stream-Aquifer
CHD Constant-Head
GWF Solvers Packages
SIP Strongly Implicit Procedure
SOR Slice-Successive Over- Relaxation
PCG Preconditioned Conjugate Gradient
DE4 Direct Solution
Global Processes

5. FTYPE CONTINUED Data Files
DATA(BINARY) A binary (unformatted) file such as those used to save
cell-by-cell budget data. Rewound for parameter estimation
DATA A formatted (text) file such as those used to save heads and drawdown, and for input of data from files that are separate from primary package input files. Rewound for parameter estimation.
Data Files For Parameter estimation (we probably won’t use these)
DATAGLO(BINARY) A binary file (unformatted)—Not rewound
DATAGLO A formatted (text) file—Not rewound
Global Processes

6. DISCRETIZATION FILE Contains data that defines the physical size of the finite difference grid and the fundamental components of time discretization.
Horizontal Discretization
Columns are numbered starting from the left side of the grid
Rows are numbered starting from upper edge of grid
Horizontal grid dimensions are specified in variables DELR and DELC.
All cells in a column have the same width so there is one value of DELR for each of the columns.
There is one value of DELC for each of the rows
Global Processes

7. DISCRETIZATION FILE CONTINUED
Vertical Discretization
Layers are numbered from the top layer down.
Elevation of the top of layer 1 is defined in addition to the bottom elevation of every layer.
Cell thickness is calculated from the elevation information.
Below each layer, except for the bottom layer, there may be a confining unit where only vertical flow is treated (Quazi 3d).
For the confining units, the elevation of the bottom of bed is defined.
For each layer, the present or absents of a quazi-3D confining bed must be indicated (LAYCBD).
Global Processes

8. DISCRETIZATION FILE CONTINUED
Time Discretization
The fundamental component of time is the time step.
Time steps are grouped into stress periods.
Time dependent input data can be changed every stress period.
Specified by user each stress
period:
PERLEN Length of stress period
TSMULT Time step multiplier
NSTP Number of time steps in a stress period
If TSMULT>1, the length of the first time step (Δt1) is determined from the following equation for a geometric series:
And for 2≤m≤NSTP,
Global Processes

9. DISCRETIZATION FILE CONTINUED
MODFLOW can simulate steady state (SS) or transient conditions (TR).
A single stress period length is specified for steady state and only a single time step is required.
Individual stress periods in a single simulation maybe either steady state or transient.
The steady state and transient stress periods can occur in any order.
Global Processes

10. DISCRETIZATION FILE CONTINUED
Within the listing outputs, units of length and time may be labeled
ITMUNI indicates the time label:
0 – undefined 3 – hours
1 – seconds 4 – days
2 - minutes 5 – years
LENUNI indicates the length label:
0 – undefined 2 - meters
1 - feet 3 – centimeters
Note: Be sure to use consistent units for all input data!
Global Processes

11. DISCRETIZATION FILE CONTINUED
Spatial
NROW Number of rows
NCOL Number of columns
NPER Number of stress periods
ITMUNI Time unit
LENUNI Length unit
LAYCBD Quazi 3D confining layer indicator. There is one value for each layer.
LAYCON =1→Confining unit
LAYCON=0→No confining unit
DELR Cell width along the row, there is one value for each NCOL columns. This data is read using a utility package (U1DREL)
Discretion File Data
Discretion File Data Example
Global Processes

12. DISCRETIZATION FILE CONTINUED
DELC Cell width along the columns, there is one value for each NROW rows. This data is read using a utility package (U1DREL)
Top Top elevation for Layer 1. This data is read using a utility package (U2DREL)
BOTM The bottom elevation. There is one for each layer and quazi 3D confining layer. This data is read using a utility package (U2DREL)
Discretion File Data
Discretion File Data Example
Global Processes

13. DISCRETIZATION FILE CONTINUED
Temporal
PERLEN The length of a stress period
NSTP Number of time steps in a stress period
TSMULT Multiplier for the length of successive time steps
Ss/Tr Is a character variable that indicates if a stress period is transient or steady state,
TR Transient
SS Steady State
Note: The four temporal variables are read for each stress period.
Discretion File Data
Discretion File Data Example
Global Processes

14. PARAMETERS
A Parameter is a single value that can be used to determine data values for multiple cells.
Changing the parameter value changes all of the associated data values.
Parameters are used in the Parameter-Estimation Process because there is not enough data to estimate all types of inputs for all cells.
Parameters are a convenient way to specify input data even if not using the Parameter-Estimation process.
Global Processes

15. PARAMETERS Layer or Array Data
A value is required for every cell in one or more horizontal of the grid (e.g. hydraulic conductivity)
Data can either be read using the utility modules or using parameters, but the same method must be used consistently for any data type (e.g. if parameters are used to define hydraulic conductivity in a layer, then parameters must be used to define hydraulic conductivity for all the layers).
Global Processes

16. PARAMETERS
List Data
Data values are required for only some of the cells (e.g. cell that have river nodes).
MODFLOW-2000 allows only some list data to be defined using parameters (e.g. streambed conductance, but not stage or river bottom elevation).
Parameters can be used, or one line of data can be read for each cell for which the data is required.
It is generally possible to define some values in the list by directly reading and other values in the same list through parameters.
Global Processes

17. PARAMETERS
When parameters are used for list data, the data value for the cell is calculated as the product of the parameter value, which may apply to many cells, and a cell multiplier or factor, which applies only to the cell.
Global Processes

18. PARAMETERS
When parameters are used for array data, multipliers are defined using multiplier arrays.
There may be a different multiplier array for each layer and each parameter type .
If a specific parameter type has more than one parameter values for a layer, a zone array is used to assign specific values to specific cells.
There can be a different zone array for each layer and each parameter type.
Global Processes

19. PARAMETERS
The data value in a cell can be determined by more than one parameter.
If two or more parameters of the same type include the same cell, the final data value equals the sum of the contributions for all of the parameters.
When two or more parameters are used to define the value for cells, the parameters are said to be additive.
Global Processes

20. PARAMETERS
Multiplier Array for P1
Example: Use of two parameters to determine layer data values for the same cells.
It is desired to have a hydraulic conductivity distribution (layer data) vary linearly from 10 to 100 from the left side to the right side.
Let P1 and P2 be the two parameters with multiplier arrays shown on the right.
Multiplier Array for P2
Global Processes

21. PARAMETERS
P1=10 and P2=100
The contributions from both parameters will be added as indicated in the upper right table.
The final result is shown in the lower right table.
Note: The same distribution could have been created other ways.
Final Result
Global Processes

22. PARAMETERS
Parameter P1 Data List
Example: Use of two parameters to determine list data values for the same cells.
Streambed conductance is assumed to be a mixture of two types of material: coarse grained (P1) and fine grained (P2)
Parameters P1 and P2 both include the five cells where the two river bed materials are intermixed.
Parameter P2 Data List
Global Processes

23. MULTIPLIER FILE
TEXT
The # character in column 1 and any type of characters there after up to 199 in number. Used for comments.
NML
The number of multiplier arrays to be defined.
MLTNAM
Name of multiplier array. May be up to 10 characters in length and is not case sensitive.
FUNCTION
Optional keyword indicating that a multiplier array will be constructed from other multiplier arrays.
Global Processes

24. MULTIPLIER FILE [RMLT(NCOL,NROW)] – U2DREL The multiplier array.
MLTNAM1, MLTNAM2, MLTNAM3…
Are names of the multiplier arrays that have already been defined.
Op1, op2, op3…
Are arithmetic operators used to define a multiplier array based other multiplier arrays. The operators +, -, * and / are allowed.
Global Processes

25. Example Multiplier Array Input Using FUNCTION keyword
MULTIPLIER FILE
Example Multiplier Array Input Using FUNCTION keyword
Global Processes

26. ZONE FILE NZN The number of zone arrays to be defined. ZONNAM
The name of a zone array May be up to 10 characters in length and is not case sensitive.
IZON(NCOL,NROW) – U2DINT
A zone name.
Global Processes

27. ZONE FILE
Zone File Example
Global Processes