MODFLOW: define error input

[Doung Ratha]

Hi,

Unsuccessful of running MODFLOW finishes with error message "MODFLOW terminated with error !". Model Checker is OK (NO error, when running model checker). Why it's happened? How to know what the error is? How to find out which parameter is inconvenience among all? Therefore, we can go through and check only that input rather than re-check all parameters.

Thank you in advance for your time.

Ratha

[Sean Czarniecki]

The model is not converging. Open your model output file, take a look near the end and you might get an idea for where the problem is occurring in the model. You might need to make some changes....maybe extend the number of iterations....maybe you need to fix your starting heads so that they are closer to what you expect for a solution. It can be a number of things.

[Doung Ratha]

Hello Sean,

Appreciated. Thank you very much for suggestion. You gave me idea how to figure out what/where the problem is.

Thank you.

[Doung Ratha]

Hello Sean,

I created a 5 layers model with constant head assigned for river at the right, and for sea at the left. The rest is NO flow. Modflow terminated with error. I open model output file, I toke a look near the end of the file, I found:

SOLVING FOR HEAD

CONSTANT-HEAD CELL WENT DRY -- SIMULATION ABORTED

0.000000000000000E+000 0.000000000000000E+000 0.0000000E+00

LAYER= 1 ROW= 79 COLUMN= 126 ITERATION= 1 TIME STEP= 1 STRESS PERIOD= 1

What does it mean? The error because of the cell become dry at layer 1, row 79, column 126? How to fix this problem?

Thanks in advance.

Ratha

[Sean Czarniecki]

It told you exactly what happened - a constant-head cell (in row 79, column 126 of layer 1) went dry. It did this because there was too much difference between the head calculated in the neighboring cells and the constant-head value. Think about it this way - even though you tell it to be constant-head, this is only one input to the solution for a cell. The model takes each input in a certain order as it solves for a cell. If the neighboring cells are dry or really different than the constant-head cell, it can cause the constant-head cell to go dry (so could an evapotranspiration rate that removes the water from the cell). There are many reasons why it could have gone dry. You need to look at this area of the model and figure out why it went dry. If your starting heads are too far off from the final solution, the neighboring cells may be fluctuating significantly, causing cells to dry out during the simulation. Also, it may be that your constant-head cell should actually be in the 2nd layer, but not in the first (is the constant head value below the bottom elevation of the cell?).