FLOPY Meaning of ibound = -1?

[Gal Bartfeld]

I have seen an example (https://flopy.readthedocs.io/en/latest/Notebooks/mf_tutorial01.html) where some cells are set to ibound -1. My understanding is that 0 - inactive cell, 1 - active, but I am not sure what -1 means. 

[Richard Winston]

In MODFLOW-2005, a negative value of IBOUND means the cell is a constant head cell.

https://water.usgs.gov/ogw/modflow/MODFLOW-2005-Guide/bas6.html

On Mon, Sep 8, 2025, 3:11 PM Gal Bartfeld <galb...@gmail.com> wrote:

I have seen an example (https://flopy.readthedocs.io/en/latest/Notebooks/mf_tutorial01.html) where some cells are set to ibound -1. My understanding is that 0 - inactive cell, 1 - active, but I am not sure what -1 means. 

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[Mike Taves]

For older MODFLOW versions, negative IBOUND values are constant head cells, with the constant head values specified by STRT.

On Tue, 9 Sept 2025 at 07:11, Gal Bartfeld <galb...@gmail.com> wrote:

I have seen an example (https://flopy.readthedocs.io/en/latest/Notebooks/mf_tutorial01.html) where some cells are set to ibound -1. My understanding is that 0 - inactive cell, 1 - active, but I am not sure what -1 means. 

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[Jakab Andras - Gmail]

It means Constant head cells.

Gal Bartfeld <galb...@gmail.com> ezt írta (időpont: 2025. szept. 8., Hét 21:11):

I have seen an example (https://flopy.readthedocs.io/en/latest/Notebooks/mf_tutorial01.html) where some cells are set to ibound -1. My understanding is that 0 - inactive cell, 1 - active, but I am not sure what -1 means. 

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[Ashutosh]

Hi,

If i remember it right then -1 means that a constant head will be applied from the initial heads value.

//Ashutosh

Sent from my iPhone

On 8 Sep 2025, at 21:11, Gal Bartfeld <galb...@gmail.com> wrote:

I have seen an example (https://flopy.readthedocs.io/en/latest/Notebooks/mf_tutorial01.html) where some cells are set to ibound -1. My understanding is that 0 - inactive cell, 1 - active, but I am not sure what -1 means.