woodward

GMS Experts
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woodward last won the day on October 22 2009

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About woodward

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  • Birthday 12/21/1965

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    http://www.lincolnagritech.co.nz/
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    Hamilton, New Zealand
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    Vadose zone, nitrogen species transport and transformation, pastoral hill land, GMS, FEMWATER, ground-vadose-surface interactions

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  1. Yes the unsaturated curves can cause problems. I also recommend NOT using the spline interpolation, as sometimes this results in a non-monotonic curve. Be careful about the curve spacing and how far away from the water table you specify it (as the last value will be used for all higher tensions as well).
  2. Could be that you have accidentally applied constant head bcs also at the transient boundary? Also with transient simulations, it is often a good idea to start with small time steps, and increase them. You are welcome to send me the project and I can try it out here. Although not sure if my license is up to date.
  3. First thing I would look at is convergence on each time step. Is the model iterating and converging? It sounds like it is not. This could be because your convergence settings are too loose or too tight, or because your discretization is too coarse.
  4. Why thank you sir!
  5. I'm not sure about the effective/total porosity, but the Unsat Curve dialogue in GMS is simply to generate a look up table of values, it is not connected to any of the other model inputs (and the inputs are not stored by GMS). Also there is a bug in the units as discussed here:
  6. I'm glad you got it working
  7. Check this old post. Maybe you are right, the problem is the NUMBER of XY time series. It seems GMS doesn't remove old ones so you can exceed the array bound.
  8. By the way, does it make sense to use a 30 day time step when you are simulating movement through the unsaturated zone? Normally you need small grid spacing and time steps for this, although the FEMWATER Langrangian method might help. Check the Peclet and Courant numbers.
  9. Not too many XY series, but maybe some of your XY series are too long. You can edit the unsaturated zone curves in the dialogue box in GMS. There is a wizard for generating them. Or you can generate them outside GMS and paste them in manually i think (that's what i did, I think). It's a while since i used GMS. Or you can edit them directly in the FEMWATER text files produced by GMS. It really important to read the FEMWATER manual and be familiar with how it works, and the text files it reads. There are a few bugs here and there. If you check my older posts here (few years ago) I might have mentioned some of them. By the way DON'T use the spline smoothing option, it can cause errors because it is not guaranteed to be monotonic..
  10. Hi Han It means your model is too big. FEMWATER is unfortunately compiled with fixed array sizes, if your model is too big you will need to recompile FEMWATER with larger arrays or make your model smaller. The source code is available from AQUAVEO. In this case the problem is you have an XY series that is longer than 250 rows. XY series are used for time series and also for unsaturated zone curves. By the way, in my experience FEMWATER has poor mass balance for transport calculations. Simon
  11. Sadly I have not had the opportunity to use FEFLOW, as it is well beyond the budget of my organisation. We tend to stick with the cheaper options. Mostly we use MODFLOW. I'm not sure the best option for fully coupled models. There are other things I have heard of like COMSOL, HydroGeoSphere... PS: FEMWATER can do fully coupled models. There is a limit to the number of nodes and elements, this is hard coded, but if you recompile the exe you can change it. PPS: You could try asking on a general gw modelling forum such as gwmodel, for software suggestions.e.g. https://groups.yahoo.com/neo/groups/gwmodel/conversations/messages https://in.groups.yahoo.com/neo/groups/feflow/conversations/messages
  12. I used to be the FEMWATER support person here, I've done some coding with the FEMWATER source code (developed my own reactive transport version), and I've used it (unsuccessfully) for a small scale problem (I eventually switched to MODFLOW-NWT). My view is that FEMWATER is pretty limited in its usefulness. It does not have many features (e.g. no zone budget) and some of the advertised features do not actually exist (e.g. no river package, some element types don't work). It is an old code that may be useful for some simple problems. The author no longer supports it. Also, I found the transport mass balance to be very poor (this is why I abandoned it). And it is not compatible with modern calibration tools like PEST. Edit: If you decide to go with FEMWATER, I have a bunch of documentation that you might find useful.
  13. I have used PEST with Groundwater Vistas. I assume it's similar in GMS. If you want the realisations to converge, you can change the convergence criterion/increase the number of iterations. The number of iterations is usually set to only 2 for NSMC to make it fast. This might not be enough for your model. Have you checked the model batch file that PEST calls? Can you see where the HK file is created? Maybe the batch file is failing to create the HK file for some reason.
  14. Yeah it doesn't look right. Did you check that the zones are set up correctly?