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Sean Czarniecki

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  1. Interesting. I don't really have time to look into it further, so I'll brainstorm with you. I'm wondering if setting IPHDRY to a positive number could be causing the problem, depending on what you are setting HDRY at. Try putting IPHDRY to 0 to see what happens. The cell would then clearly not be available for particles. " IPHDRY is a flag that indicates whether groundwater head will be set to HDRY when the groundwater head is less than 1×10-4 above the cell bottom (units defined by LENUNI). • If IPHDRY=0, then head will not be set to HDRY. • If IPHDRY>0, then head will be set to HDRY. If the head solution from one simulation will be used as starting heads for a subsequent simulation, or if the Observation Process is used (Harbaugh and others, 2000), then HDRY should not be printed to the output file for dry cells (that is, the UPW Package input variable should be set as IPHDRY=0).
  2. Is that output line at the end showing top and bottom elevation of the specified cell (which appears to be reversed), or the head and the bottom elevation in the cell?
  3. You can just select cells manually and change the conductivity in the properties dialog....or set up a coverage with polygons to change just small areas when it maps over to MODFLOW. Test it out so that you can confirm everything else remains the same when you map it over.
  4. So let me tell you something that might help you to figure out what is going on. I had built a model using MODFLOW-USG....one of the reasons was because it managed dry cells without actually making them dry (model converged with no issue). Well, after months of working with this model, a newer MODFLOW-USG executable came out (and was being used in GMS) that eliminated that part of the programming (I guess it was not helpful to some people - enough complaints got the programming changed). Well, that certainly messed up my modeling. It wouldn't converge anymore. The solution was ultimately to set GMS to use the older executable. Soooo.....long story short.....the older MODFLOW-USG executable may solve your original model.
  5. It would only use it during transient runs.
  6. Open up your output file and see if it gives you more details about the issue. It could be that you've got more time steps than the variable allows. I'm not sure what that array value is, but it sounds like that could be the issue.
  7. The only ways you can fix this is to either add more layers or change the thickness of your layers.....neither of which you probably want to do. If you read up on MODFLOW, you will see that it prefers if you don't make big transitions, but it will still be okay if you have them. We often have a thin confining layer (e.g., 1 m thick) above a thicker layer. For that warning to go away, you would have to make the next layer below no greater than 1.5 m thick, then another below that no greater than 2.25 m thick.....etc. You can see that this is often not practical. I suggest you don't worry about that warning. Other people may feel differently.
  8. Warnings are not always a problem. The Cell Dimensions warning is telling you that the model results will be better if you have a smoother transition from smaller cells to larger cells (this will often come up based on layer thickness differences). The model will still work - this isn't usually a big concern. The second set of warnings is pretty clear - you need to establish hydraulic conductivities in layers 4 through 8....check your materials. You can also make these changes in other ways by opening the LPF package and editing layers individually, or by making coverages for each layer.
  9. The entire layer is blocked. If you need it to stop at a certain elevation, you need to set the bottom elevation of the layer at that elevation.
  10. Under the Grid menu, there is an option for MODFLOW Layers -> 2D Scatter Points. Under there, select the flow package properties.
  11. You have to go under display and go into General Mode instead of Ortho Mode. You will then be able to rotate the display in all directions. Note that if you are in a multi-layer model, you may need to select other layers and hide them as all layers become visible at the same time in General Mode.
  12. http://www.aquaveo.com/software/gms-learning go into the tutorials under the Conceptual Model modules (by going through 1 and 3, you should be able to figure out how to define different layer extents).
  13. Yes. However, if it is bigger than the current extent, you will have to expand the overall grid and then inactivate the cells outside of the current extent in your current layer. You can cut the layer using the grid tools and then change the extent of the second layer as necessary by inactivating cells beyond whatever extent you are looking for. You can do a lot of this by making a boundary polygon for each layer (see the GMS tutorials).
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