I would like to ask about the length of the* computational time of the transient model*. I have built already several more complex models, but my transient models never exceeded 1 or max 2 hours to be finished. Not this time.

I had built (I have to admit rather big model) with the number of the cells around 3 000 000. As flow package there is used **HUF **and as the solver **PCG2**. For the steady state my model finishes somewhere at the 10^{th} iteration with the total computational time around 7 min.

Built on that is the transient model with 27 stress periods. From previous experience I would guess the maximum time around 1.5 hour – stress periods usually are getting faster to be run. What surprised me is that I am getting to the time more than 4 hours. Changing convergence criteria doesn’t help me, as the problem is not the convergence of the model itself – at least for outer iterations (for each stress period I have convergence within 3 – 5 iterations). Neither changes of the solver had helped me.

In my model occurs several bigger places with dry cells – but I am not allowing rewetting – could it be the problem?

I had built similar model in with NWT solver – there was the time around 1.5 hour to complete transient model. Is there any reason why HUF should cause longer computation?

Thanks for any kind of the tips or ideas to get this model faster ;-)

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Kind regards,

Jonas

]]>I have encountered a problem with exporting native modflow files from GMS. Some of the model parameters are defined using Pilot points. Lets say that I would like to use different version of MODFLOW to calibrate the model. I have succesfully exported the MODFLOW native files and I was able to start USGS version of modflow. The input data are read correctly, first stress period is solved, however during the second period MODFLOW stops. Here is the end of the output file:

PERCENT DISCREPANCY = -0.03 PERCENT DISCREPANCY = -0.03 TIME SUMMARY AT END OF TIME STEP 1 IN STRESS PERIOD 1 SECONDS MINUTES HOURS DAYS YEARS ----------------------------------------------------------- TIME STEP LENGTH 2.67840E+06 44640. 744.00 31.000 8.48734E-02 STRESS PERIOD TIME 2.67840E+06 44640. 744.00 31.000 8.48734E-02 TOTAL TIME 2.67840E+06 44640. 744.00 31.000 8.48734E-02 1 1 STRESS PERIOD NO. 2, LENGTH = 29.00000 ----------------------------------------------- NUMBER OF TIME STEPS = 1 MULTIPLIER FOR DELT = 1.000 INITIAL TIME STEP SIZE = 29.00000 PARAMETER "sc1v1 " IN PARAMETER INPUT FILE HAS NOT BEEN DEFINED -- STOP EXECUTION PARAMETER "sc1v2 " IN PARAMETER INPUT FILE HAS NOT BEEN DEFINED -- STOP EXECUTION PARAMETER "sc1v3 " IN PARAMETER INPUT FILE HAS NOT BEEN DEFINED -- STOP EXECUTION PARAMETER "sc1v4 " IN PARAMETER INPUT FILE HAS NOT BEEN DEFINED -- STOP EXECUTION .... PARAMETER "GHB_3405 " IN PARAMETER INPUT FILE HAS NOT BEEN DEFINED -- STOP EXECUTION PARAMETER "GHB_3409 " IN PARAMETER INPUT FILE HAS NOT BEEN DEFINED -- STOP EXECUTION PARAMETER "GHB_3406 " IN PARAMETER INPUT FILE HAS NOT BEEN DEFINED -- STOP EXECUTION

When modflow starts no interpolation is performed for the pilot points. I assume there is some custom routine in the GMS version that handles the interpolation from PP to the MF grid array. Please advice how this is supposed to be handled or what am I doing wrong.

]]>Are observations not set up to work in MODFLOW-USG?

]]>when converting a steady state model to transient I initialize the stress periods and import transient boundary conditions via MAP to MODFLOW. This seems to work.

But for Recharge the following error occurs when looking at RCH or RCH rate:

Within the properties of RCH rate all stress periods seem to be in the right format (identical to what has been defined under "Global options - stress periods" and same as for other boundary conditions like transient pumping rates e.g.).

Can you help?

Am using version 10.3

Mark

]]>

I'm building a multilayer model with GMS (MODFLOW-USG) for a region in Portugal and i start the calibration fase.

Can anyone tell me the best way to calibrate my model?

I'm thinking about to using the pilot point method, but i cant find a tutorial on how to proceed for calibration of multilayer models...

Can anyone help me?

Thanks in advance

]]>

I noted GMS has values for porosity in both MODFLOW and MT3D. In MODFLOW menu (MODFLOW options) one can enter values for porosity, although porosity is not used in flow computations as far as I know. Also in MT3D menu it is essential to enter porosity value.

In the model I have (which is a SEAWAT model) I entered values for porosity in the MT3D options, but I noticed there are different values -by default- in the MODFLOW options. Which values does the model consider in this case? and why is there an option for porosity in MODFLOW?

Thanks

]]>When viewing model result value as a table and trying to export the result to dataset.txt file, GMS crashes if the old dataset file is open in excel. It should not crash but prompt a message or something like that.

]]>it is often the case to treat WEL package data (e. g. well pumping/injection rate or specified flow BCs) as adjustable parameters when doing inverse modelling for parameter estimation or optimisation. I would like to see a better GMS handlig of this. One cannot use conceptual model at all when trying to define specified inflow BCs as parameters, because GMS treats the Key value as flow rate and distribute it between the cells intersected by the BC conceptual model geometry.

In the case of pumping well it is possible to specify Key value in the conceptual model and map it to MODFLOW (hopefully) correctly. However there is no check whether this exact Key value does not appear in the regular pumping data. This could easily lead to an error. Especialy when the model is continuosly used and the pumping data with some key values are reasigned over and over during the model application.

I would consider wise to be able to specify in GMS whether a particular value is Key value or not and to treat it accordingly in GMS. Also a model checker should check for conflicts in the WEL package for the reasons described above. This obviously extends to MNW package as well.

I am wondering if anybody else experienced this problem and would like to see this implemented.

]]>Why call it support for SFR2 while it is actually support for SFR1?

Would be great to have this functionality added to GMS in the (near) future.

Regards,

George

]]>I am using Modflow 2000 code in GMS 10.2.6 64bit version for the simulation of groundwater flow and MT3DMS for the transport and fate of nitrates in a aquifer study area. The study of the aquifer’s pollution by nitrates is carried out at the level of Municipal Districts (30 Municipal Districts, each has a unique polygon). Τhe reason why I'm communicating with you is that I have a problem with MT3DMS calibration.

- I follow all the steps along with the default times described in the tutorial of MT3DMS Conceptual Model Approach to set up my MT3DMS simulation which runs successfully.
- The sensitivity analysis indicates that the nitrate leaching parameter is the most uncertain parameter. As a result, the calibration is based on the nitrate leaching rate using a trial and error method, but every time I change the nitrate leaching, no significant difference noted to any polygons .
- Ιt may be a silly mistake that I can not figure out.
- Μaybe the answer would be to do an observation point to each polygon? but it is a whole area with consists of polygons.

Kind Regards,

Georgios Tziatzios

I am using SEEP2D and I would like to calculate the factor of safety with software values. I obtained gradient values for vertical but these values very very small. While I calculating the factor of safety, the result is not acceptable such as 600 or higher value. I checked everything like formula, model design but I don't understand what is the problem. Permeabilities for horizontal is 0.0001 and for vertical 0.00025. for reservoir area, the boundary condition is the head, and another side is exit face boundary condition. Under the dam has alluvium foundation and beneath the foundation has basalt. My values are m/s for each data. What should I do to obtain reasonable factor safety value? Because hydraulic gradient is important to calculate.

]]>I am currently modeling slurry trench simulation via SEEP2D. I obtained some histograms from software but actually I do not understand how should I can interpret about histogram results. I added histograms below. Also, in Y axis is total head or flowline or flowrate etc. but X axis is Frequency. The condition is steady state which means time accepted 1.0. So, what is the X axis (Frequency) unit? In addition, may I change Frequency in X axis instead of other type value? Thank you for your answers.

]]>

I tried to increase the resolution of the USG grid but still get holes (white areas). Do these holes will allow leakage through the barrier?

]]>At hand, there are data of the positions of the 6 geological boundary surfaces represented by the distribution of points (x, y, z) and the positions of the 6 faults also represented by distribution of points(x, y, z).

How can I make appropriate modeling? Which package should I use? ]]>

(note that I'm using GMS 10.3.3 - I don't think that the CLN_CB file even got pulled into GMS 10.2, but I haven't fully looked into it)

Thanks!

]]>The process starts with a calculation of the Jacobian matrix:

But ends like this:

It always works when I run the model without pilot points. A forward run with the pilot points also works.

I have managed to run both a parameter estimation and NSCM with SVD-assists before with the same model constraints but when experience this problem when I attempt to make changes in the model.

Ideas on how to solve this issue?

]]>I built a model with Streams (SFR2) and lakes (LAK3). I know that, until now, GMS cannot automatically connect SFR2 with LAK3 when converting the conceptual model from Map ->MDFLOW. As a workaround, we edit the OUTSEG and INSEG IDs of the SFR2 manually using the negative lake IDs (after the performing a Map-> MODFKOW conversion). The problem is that, although the segment numbers are correct, I still get Error Messages when I run the Model Checker as shown in the figure below.

Is there any possibility to remove this error message from model checker?

Thank you

]]>
Thank you for your reply on my messages and my requests. I would like also to ask if it is possible to add another issue to the Model Checker in order to recognize an error that related to the SFR2 Package. I have noticed that the Model Checker does not compare the streambed-elevation (ELEVUP or ELEVDN) with the cell bottom elevation in a similar way as it works with the River Package (RIV1). This means that even if the elevation of the streambed is below the cell bottom elevation, which may cause many problems in some models, the Model Checker still give the green message that there is “*No Errors or Warnings found in model inputs”*.

In order to clarify this issue, I sent you a very simple example as Attachment.

Thanks

]]>Using the command "auto assign horizons", i realized that GMS does´t follow that logic. If i understand it right, than GMS should start at the deepest Borehole and assigns horizon numbers. In my case it seems to choose the highest borehole(in elevation) in the area and starts assigning the horizons . As this borehole is also shallow a huge error is introduced, as horizon 1 is located high in the landscape and GMS, according to its algorithm(horizon to solids), fills up the areas below horizon "1" with its corresponding unit. Thereby it ignores all deeper occuring layers eventhough they are specified in the crosssections manually.

Is there a bug in the program or is it simply a misunderstanding of mine?

Looking forward for answers!

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