iMOD User Manual version 4.4 (html)

10.3Data Set 2: Configuration

Data Set 2



The number of model layers that the current simulation will take into account. There is no need to adjust the Runfile as long as NLAY will be smaller or equally to MXNLAY. Whenever NLAY becomes less than MXNLAY all active model cells, within model layer NLAY, operate as a Dirichlet boundary condition and simulate a vertical flux over the edge stressed by the starting head condition (SHD, see Data Set 8) or last given heads from the constant head package (CHD, see Data Set 8) for that particular model layer.


This runfile-option is scheduled for a next iMOD release Currently MXNLAY always equals NLAY. MXNLAY is used to determine whether the lowest model layer NLAY should be modeled as an open model boundary, which is the case whenever NLAY \(<\) MXNLAY.


The number of time periods (conform the stress periods within standard MODFLOW) to be simulated. For each time period it is compulsory to define at least appropriate model input. iMODFLOW does not support the concept of time steps within time periods as standard MODFLOW does.


Specify ISAVEENDDATE=1 to save each file with a time stamp equal to the end of the corresponding stress period (and/or time step). By default ISAVEENDDATE=0 and the time stamp will be equal to the start date of each stress period (and/or time step). Note This keyword was obsolete since v3.0 and had a different purposes at that time. Be careful whenever a runfile is used that was compatible for v3.0 or older.


Flag that determines the methodology of constructing the modeling network:


The modeling network will be identical to the network that is described in the IDF file (or entered xy coordinates) given by de keyword BNDFILE, see Data Set 9. In this manner, it is possible to compute with networks that distorted spatially on different locations.


The modeling network will be defined by Data Set 6. The buffer around the area of interest will be equal to the chosen grid sizes within that area of interest.


The modeling network will be defined by Data Set 6 whereby the grid sizes within the buffer around the area of interest will increase up to a given maximum size.


Flag to indicate the mode in which iMODFLOW will perform the simulation:


Start the simulation without testing the existence of files. Any none existing file will terminate the simulation and after recovering such file the simulation need to be restarted from the beginning.


This option 1 is scheduled for a next iMOD release.
Test the entire Runfile on the existence of files and correct content of IPF files. The model will not be computed and at the end of the evaluation a summary is written in a file called: imodflow_[version-tag].log.


Within a model configuration it can occur that within identical model cells, the drainage level from the Drainage package (DRN, see Data Set 8) and/or the drainage level from the Overlandflow package (OLF, see Data Set 8), or even other elements from a River package (RIV, see Data Set 8) are positioned below a specified water level of the River package (RIV) itself. To avoid such undesired situation, e.g. within flooded areas, these drainage systems (DRN, OLF and RIV) can be inactivated for this situation, automatically.


No adjustments of the DRN and OLF packages


The DRN, OLF and/or RIV systems are turned off whenever their drainage levels are below existing river water levels (RIV-package) in corresponding model cells.


This flag indicates whether time series need to be computed during the simulation.


No time series included


Include n-number of IPF files with location of time series to be computed for each stress period throughout the simulation, See Data Set 3.


Apply an interpolation of computed heads toward the location of the measurement.


This flag indicates the usage of unconfinedness for aquifers.


All aquifers are confined, unconfinedness is supported via the NAM-file export mode only, see section Section 5.5 and Section 8.6.5.


This flag indicates the methodology to be used computing the conductance for streams given in the ISG package. The default value is IFVDL=0.


River conductance is a function of river length (m), wetted perimeter (m) and river resistance (d), solely.


River conductance is a function of river length (m), wetted perimeter (m), river resistance (d), permeability and thickness of appropriate aquifer, resistance of first aquitard.

Whenever IFVDL=1, it is obliged to have the keywords TOP and BOT activated or the package SFT should be active


Use this to specify artificial recharge to be read from an IPF file