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Michal

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Everything posted by Michal

  1. Specified flow boundary condition with Modflow-USG

    Hi Alan and Bill, thank you for looking into it. Let me post just a few remarks. That looks like exactly the correct behaviour, I think this is how the check is implemented in MODFLOW. I may be wrong on this one. What if GMS just checked, that the layer above the top most spec. flow BC has the complete spatial XY coverage of the model region you mentioned? This would allow users to cover near-surface aquifers, that does not span across entire model with apropriate top layer in the multiaquifer system and still be able to apply spec. flow BC for the deeper aquifers/layers.
  2. About 3D Grid

    I believe, it is just due to interpolation from cell center points to gridlines intersection. It should not affect the solution for MODFLOW. Its just a matter of how GMS displays the data.
  3. Fixed pilot points in PEST NSMC

    I believe the problem is, that some parameters are cited in the covariance matrix C(k), but are not included in the PEST control file as adjustable parameters. Check it with the sc1v145 parameter.
  4. Fixed pilot points in PEST NSMC

    Hi Jonas, this is interesting. What interpolation method have you used for the pilot points in the first place? Did GMS just read the pre-generated values from the RANDPAR utility and than continued itself with the PNULPAR, etc. ?
  5. PEST, SVD and SVD-assist

    You are welcome. I am happy I could help you.
  6. MODFLOW-USG & CLN cells staying wet

    I think the behaviour you are describing relates to the Upstream Weighting scheme of MF-NWT, that is implemented in MF-USG as Upstream Convertible. See this report, chapter treatment of dry cells.
  7. Specified flow boundary condition with Modflow-USG

    Hi there, I am also interested in solving this issue. I have found out so far, that the ugrid has to be a "stacked" ugrid in order for the GMS spec. flow BC to map from the conceptual model. This means, that layer discretisation must not change from layer to layer. This sucks, because GMS Specified flow boundary condition utilizes WEL package and you can easily do the assignment manualy on the grid level even on a grid, that is not strictly "stacked". All you have to do is to ensure, that the cells in the column, where WEL is assigned have the same horizontal dimmensions through the vertical column of cells. Here is a short demonstration. It is a simple test three layer model computed with MF-USG using quadtree geometry. It utilizes CHD for south BC and GHB for a river runnnig through the domain. This GHB river is in the top layer and it is densely discretized (see the first picture). There is also Recharge in the top layer. There are three pumping wells (WEL package), that withdraw water from the third bottom most layer. These are densely discretized in all three layers. The specified flow BC is in the third (bottom) layer as inflow 100 l/s. It was assigned to the north model boundary using grid aproach by dividing the flow equaly between cells. The cells with this spec. flow BC have all equal vertical column sizes. The point is, that the river running through the domain is discretized only in the top and second layer, not in the third one (see the picture below). This approach can save a lot of computation time as it reduces the number of cells significantly. The solution is the same as when everything is assigned on the stacked grid and the river is densely discretized through all layers. The question is if there realy is necessary such a strict limitation on the grid geometry when mapping Spec. flow BC from the conceptual model? By my opinion only the vertical column sizes must have the same dimmensions and the grid doesnt need to be "stacked". The same thing as with specifying wells in GMS should apply to the Spec. flow BC.
  8. PEST, SVD and SVD-assist

    Hi Jonas, If you try to generate random parameter values with this utility you have to decide how to describe the variability in the generated values. If you choose, that random values should obey (log)normal distribution you must specify its properties for each ajustable parameter (e.g. uncertainty of that parameter). This is done by specifing uncertainty file (see section 2.5 in PEST manual part II). Within this file uncertainties can be supplied on a parameter-by-parameter basis; alternatively one or a number of parameter covariance matrices can be supplied. If you want to avoid all this, try selecting (log)uniform distribution for the random values. Then you should be able to generate the uniformly distributed values without any problems. Hope it makes sense
  9. PEST Variables - Drain Conductance

    Hi Bruce, you may try to make one parameter adjustable (parent) and the rest in the basin tied to the parent. Relevant part from PEST manual: Or, alternatively, you could include the ratio between the pertinent parameters as prior information and adjust its weight accordingly. This way it would still be treated individualy, but the solution would tend to respect the parameter ratios. It is also also possible, that the contribution to total phi for drain observation group is too low, so it is invisible for the inversion proces. You may try to look at it in the case.rec file. It could be resolved by adjusting the weights for the observation groups. There is a nice utility form the PEST suit, that can help to balance this, its called PWTADJ1.
  10. PEST, SVD and SVD-assist

    If it is the case, that there is a bug in gms, so that it does not perform the final model run with the best parameter values stored in the case.bpa you would probably have to move the entire analysis out of GMS. I would suggest you to look at http://www.pesthomepage.org/. There you will find some guidelines on how to formulate the problem for the NSMC analysis to get the desired results. The usage of parrep utility is prety simple, it is command line utility, so since it is in your environment PATH variable you can run it from CMD: parrep parfile.bpa case_orig.pst case_new.pst The common framework for any NSMC analysis would be to manualy generate random parameter sets with the randpar utility then to project these sets into the solution space using pnulpar. Then runing PEST for each projected parameter set with 1 or 2 optimisation iteration to account for model nonlinearities and colect the best parameter values (.bpa files). Finaly you may run the model with these parameter sets to collect the predictions of interest.
  11. PEST, SVD and SVD-assist

    Hello Jonas, from my humble opinion it looks like PEST is doing its job well. It decreases Phi to 63.5% and finish optimisation after one iteration since NOPTMAX is set to 1.Which is probably correct if you try to do NSMC analysis. The reason it does not load solution into GMS may be a GMS glitch. What I think is happening, when PEST is run using svd-assisted inversion it does not carry the final model run using the best parameter values. As is described in the manual to PEST, it is encouraged for the user to do it him/herself using the PARREP utility and setting NOPTMAX to 0 in the PEST control file. So I am guesing that GMS does not do this for you. It would be best if someone from the GMS devs looked into it. Kind Regards Michal
  12. MT3D-NaCl barrier tessting

    Helo, it is hard to say without seeing the model. Could you be more specific in what do you mean by "nothing happens"? Do you mean like, the tracer concentration is zero everywhere through the simulation? First look at the mt3dms list file (case.out) and make sure, that the simulation ended without any errors. Then I would suggest to look at Output control in the basic transport package and make sure it is set properly, so MT3d is writing the concentration binary arrays at correct times. Also try to look at the model cell containing the injection well via sources/sinks dialog and check, that there is associated concentration with it.
  13. Dry cells

    There should be no obstacles in inactivating inner area of a single layer model using IBOUND. See the attached image.
  14. Coordinate Significant Figures

    Is each head observation in the *.hob file maped to the unique cell (IJK) and stress period? Athought it shouldn't matter if the observation's coordinates/times are not identical due to the offset variables (TOFFSET, ROF, COF), I can imagine certain confusion if multiple observation are defined for the same cell and stress period when using PEST.
  15. Hi It would be a nice feature to be able to display piezometric water level of a specifed layer(s) in a cross sectional view (row or column view) in adition to the free water table already implemented. I guess it would be suffictient to add one additinal curve to display and an option to specify from which layer the heads should be extracted. Clipping of the contours could remain as it is - using water table if water table is switched On or the second curve if water table is Off. Thx Michal
  16. constant concentration and source/sink

    Hi speedy, it seems you need to enable the MT3DMS SSM package to enable the mixing of fluid coming from the constant conc. BCs. I would try to enable SSM and set ICBUND to -1. It should work then. Hope it helps. Michal
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