Mark Flooded cells

[thuyhuong tran]

Dear all, 

I use GMS model to simulate 8 model layers. After I run, layers 1 and 2 of the model are flooded in the cells. Can someone help me solve this problem?

[Robert Lanning]

We need more information on your problem to better provide any potential answers. In general, it sounds like you may have too much water accumulating in your upper two layers; in other words, enough water cannot leave the layers either horizontally through boundary conditions, drains, or recharge to a river/stream/pond (if one exists), or vertically into lower layers due to insufficient hydraulic conductivity. Please let us know more about your model:

    - Does your model run and converge?  If so, what does the water balance file show for model input and output (I'm not familiar with GMS files)

    - By "flooded" do you mean your potentiometric surface is above ground level?  Or just higher than that in observed wells?

    - Is your precipitation recharge reasonable? It may be too high for the rest of the parameters in your model

    - What settings do you have for cell wetting (again, not familiar with GMS parameter options)

    - Is there a river, stream, or lake in the top layer?

    - Do you have boundary heads in at least some or all of your model borders, particularly in the upper two layers?

    - Do you have lower heads in at least one border boundary in all layers to allow an exit from the model?

    - Hydraulic conductivities may be too low in layers below your top two layers.

    - Do you have any drains in any of your layers?

Once folks know more they may be able to provide some guidance on specifics to check in your model, but the above are general thoughts/questions I can think of at this point.

Best regards,

Geolbob

[Jakab Andras - Gmail]

Please provide some more info as your concern could equally represent anything from normal to abnormal depending on what you are trying to infer with the model.

thuyhuong tran <thuyhu...@gmail.com> ezt írta (időpont: 2024. máj. 22., Sze, 16:40):

Dear all, 

I use GMS model to simulate 8 model layers. After I run, layers 1 and 2 of the model are flooded in the cells. Can someone help me solve this problem?

--
This group was created in 2004 by Mr. C. P. Kumar, Former Scientist 'G', National Institute of Hydrology, Roorkee. Please visit his webpage at https://www.angelfire.com/nh/cpkumar/
---
You received this message because you are subscribed to the Google Groups "MODFLOW Users Group" group.
To unsubscribe from this group and stop receiving emails from it, send an email to modflow+u...@googlegroups.com.
To view this discussion on the web visit https://groups.google.com/d/msgid/modflow/bb7c6bfa-63d3-4954-b350-4bea3384b192n%40googlegroups.com.

[Philip Margarit]

I am dealing with this in one of my models now. How I am handling this is I created a drain package in all of my upper most cells that don’t have a boundary condition or surface water feature and I set my bottom elevation of my drain to the cell top elevation. I set a conductance that won’t give me stability issues (I use a default of 10). I then change my flow budget zone for those cells to their own zone. You will have to use the Bud2smp and smp2smp PEST utilities on your ccf file GMS makes to create a parameter for that zone. For your observed value give it a value of 0 and weight it for visibility (it may give you multiple parameters depending on how many flow budget zones you have drains in, just change the others’ weight to 0). 

What this does is it will tell PEST to penalize flooded cells in your model (any drains that have outflow will add to your objective function so PEST will calibrate to not have flooded cells) To do all of this, you have to run PEST outside of GMS. If you need help taking the files outside of GMS or with the workflow for the utilities. Let me know and I can send you example files. To take your model out of GMS, run PEST in GMS until you see it wrote all of your PEST input files and the run started, select abort on the run dialog, and just make sure you moved your files off any kind of cloud storage and you should be good to go. Always check everything with the PESTCHEK utility when you do this to make sure GMS wrote your files correctly. You can really easily add in your calibrated parameters back into GMS just importing the .par file or .bpa file after your run. If you go this route, let me know and I can tell you about our workflow and what files you need from GMS to do this. 

Philip Margarit

Water Resources Science PhD Candidate

College of Food, Agriculture, and Natural Resources Science 

University of Minnesota, Twin Cities

651-262-3561

On Wed, May 22, 2024 at 8:40 AM thuyhuong tran <thuyhu...@gmail.com> wrote:

Dear all, 

I use GMS model to simulate 8 model layers. After I run, layers 1 and 2 of the model are flooded in the cells. Can someone help me solve this problem?

[Philip Margarit]

One additional note and one correction, please read "drain parameter" as observation, that was a blunder on my part. 

If you have flooded cells in most of your layer 1 and 2, you would most likely have a structural issue (i.e. parameters may be too high (ex: recharge) or too low (ex: hydraulic properties) or missing (ex: boundary conditions)) with your model that you would need to look into. If it is just patches that you can't get rid of, that PEST workflow is fairly well suited for testing if you have further structural issues that you overlooked during your initial model building. If you run your model in PEST with geologically reasonable parameter constraints and it still can't fit the data well (i.e. it can not deal with the flooded cells), then that would be a good clue that there is something structural missing in those areas of the model. What you don't want to do is ratchet up your hydraulic properties in areas where you have flooded cells to get rid of them as using hydraulic properties as proxy parameters for what is going on in the subsurface can cause a lot of issues later on when you want to use that model to make predictions. An example of this is we had a large patch of flooded cells in one area of our model that PEST couldn't deal with given reasonable parameter bounds when we added our drain outflow to the objective function. This lead us to find out that area was tile drained which is why PEST couldn't reduce flooded cells in those areas given geologically reasonable parameter constraints. PEST is a great tool for testing if you have an issue with your conceptual model so if you go through manual adjustment and can't get rid of your flooded cells without unreasonable parameters, I would try out my workflow listed above. 

Best of luck and reach out if you need help setting anything up with the files GMS outputs. 

Philip Margarit

Water Resources Science PhD Candidate

College of Food, Agriculture, and Natural Resources Science 

University of Minnesota, Twin Cities

651-262-3561

On Wed, May 22, 2024 at 8:40 AM thuyhuong tran <thuyhu...@gmail.com> wrote:

Dear all, 

I use GMS model to simulate 8 model layers. After I run, layers 1 and 2 of the model are flooded in the cells. Can someone help me solve this problem?