Dispersivity in PEST (Visual MODFLOW Flex)

[horta...@gmail.com]

Hi, 

I am using PEST in Visual MODFLOW to estimate dispersivity, however, in the parameters section in PEST I am unable to fine dispersivity or any contaminant related parameters. Please find the attached picture for reference.

Can anyone please help in this regard. 

Thank you

Mahima Horta

[Jakab Andras - Gmail]

Mahima,

The latest version of Flex (v.11) allows the following parameters to be estimated by PEST within Flex: conductivity, storage, UZF static and transient parameters, recharge and evapotranspiration. If you would like to use PEST to estimate other parameters, please use PEST outside of the Flex environment to build your PEST interface (i.e., control file and other related inputs to PEST). This of course requires more in depth knowledge of PEST and the way Flex builds the PEST interface for your model. As a matter of fact, you may manually modify the PEST interface built by Flex for the supported parameters by adding the new parameters and parameter groups to the control file along with related changes to some of the control variables, and build the necessary PEST template file(s). If you do that, you can then run PEST within the Flex interface.

András

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[mahima horta]

Hi Jakab,

Thanks for the response. However, I could not clearly follow when you say " you may manually modify the PEST interface built by Flex for the supported parameters by adding the new parameters and parameter groups to the control file..." since I do not find any way to modify the PEST interface and add dispersivity as a new parameter. Is there a reference I can follow? 

Thanks

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[Philip Margarit]

Hi Mahima,

To do this, make a copy of your .rct file and name it “file_name_rct.tpl”. In that copy, on the first line, add ptf $.

Next, find the lines that have your dispersivity values and replace them with $  parameter name $, make sure there is 12 characters including spaces between the two $. Go into your pest control file, add those new parameters to your parameter data section. Add the tpl file to the bottom of your control file in the model inputs section, and change the number of tpl files, parameter groups, and parameters in the control data portion of your control file at the top first two lines of your pst file. The pest documentation online can help you with this. If you need an example file to follow, I can email you files after work. Always make sure to run pestchek after your changes to make sure it’s all good. A good practice is when you make changes, make a copy of your .pst file and make the changes there. I typically do new as my original, then new1, new2, and so on each time I make a change. This lets you revert back if you made a mistake somewhere or decide against including something. 

If you want to use pilot points, I suggest using plproc. I am not sure what version of transport you are using but MT3D-USGS can be finicky since it is uses arrays in a certain format (I believe rows of 10 values with exactly 12 spaces between but that can be changed). Given that, you may have to code a post-processing script to add the array to the file in the correct format and add it to your model run batch file. Best of luck with everything! 

Philip Margarit

Water Resources Science PhD Candidate

College of Food, Agriculture, and Natural Resources Science 

University of Minnesota, Twin Cities

651-262-3561

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[mahima horta]

Hi Philip, 

I really appreciate your help and time, and thanks for the elaborate explanation. I have attached .RC3 file, is it the correct file I need to modify? It would be really helpful if you send me some example files so that I can follow, my mail ID is : horta...@gmail.com. Also, I am using MT3DMS.   

Thanks again

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[Jakab Andras - Gmail]

When I say PEST interface, I refer to all input files Flex creates in order to run PEST. These files are located in the same folder where the model files are placed by Flex. Making changes to these files requires in depth knowledge though, so I pnly mentioned it as a possibility rather than something you may perform within Flex. Sorry for the confusion.

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