Please help me about Errors of Visual MODFLOW Flex and PEST

[Minwook Lee]

Hello, I am Minwook Lee studying the groundwater flow modeling using Visual MODFLOW Flex.

I'm not familiar with Visual MODFLOW Flex.

I ran into a challenge while running the steady-state model.  

I set hydraulic conductivity, initial head, boundary conditions(recharge, ET, river..) etc.

As a result of "translation" and "run", it would seem to be sucessful because I saw the message such as "sucessful".

But when I saw a map, there are so many dry cell.

In addition, the chart distribution of modeling did not match the line at all.

So, I tried to calibrate using PEST and there also are a problem.

The message of error was that following;

The PEST run was not successful.
If you want to see more detailed information, please open file {0}
C:\Users\GSEL\Documents\Visual MODFLOW Flex\Projects\tunnel modeling version7.data\MODFLOW\NumericalGrid\Run1\MODFLOW-2005pest_run.rec

I want to know what's causing the error and how can I improve this model.

Let me attach some images and settings.

#Properties;

*Conductivity

-zone 1 Kx, Ky, Kz:12.96(m/d)

-zone 2 Kx, Ky, Kz:2.592(m/d)

-zone 3 Kx, Ky, Kz:0.05184(m/d)

*initial head

-Value: Surface(ground) - 8(m)

*Storage : default

#Boundary conditions

*Lake Leakance: 4.32e-08 / else: 0

*River conductance(m^2/d): 26

*Recharge(= recharge rate without ET): 130 mm/yr

*ET: 760 mm/yr

#model

*model boundary 2.8(km)*2.8(km)

*cell 200*200(layer 1/2/3)

[Richard B. Winston]

I think it was a mistake to start parameter estimation while you still have major problems with your model. You first need to figure out how to avoid having so many dry cells  and also how to make the simulated and observed values have at least some relationship. Once you do that, PEST may be able to help you.

[Asha Farsana M.]

Hi,

it seems you are modelling a sloping ground. please check if the initial head value given is greater than the ground surface elevation at the points you got dry cells. Also try cell rewetting option( might help if dry cell depth is small). need not look into the calibration chart unless the dry cell issue is solved. 

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Asha Farsana M

Research Scholar

Dept. of Civil Engg,

GEC Thrissur

Kerala, India

[Dwight Zedric Capus]

Hi,

I am receiving the same error even though my model converges. Was this problem already been fixed?

[Lai Ting-Yan]

Hello, would like to ask if there is a solution to the above problem?
Because I'm having a similar problem

thanks

ashafa...@gmail.com 在 2022年4月6日 星期三上午10:20:32 [UTC+8] 的信中寫道：

[András Jakab]

While one could of course provide all kinds of clues to solve the above problem(s), this is a much more complex matter. First, one shall first manually calibrate his/her model and have a thorough understanding of the model. When I say this I refer to things such as knowing why does the model behave as it does and not as expected, are boundary conditions correct, is the budget realistic, etc? Once these were sorted out, which of course involves a lot of learning, then it might be possible to use tools such as PEST to improve the fit. I perfectly agree with Richard's comment above. PEST, however, cannot fix a bad model. Unfortunately, the usage of both MODFLOW and PEST and all related programs and utilities involve learning. They are not black boxes by any means. I would suggest to first read the basic documentation of the code, perform a few tutorials and example problems, then start your project over. A good starting point could aslo be to attend a course. There are quite a few courses adevertised on the GUI developers' webpages.

Just to conclude. The above problems are not caused by the code, and they are a result of improper conceptualization. This also means that noone will be able to properly help solving these issues without themselves understanding your model.

[Dwight Zedric Capus]

In my case I did not change the time for PEST run

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