Hydrology

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About Hydrology

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  1. I have created materials in a GMS model, and assigned the materials to different modflow layers. The material characteristics such as hydraulic conductivity that I have assigned to each material do not seem to be mapped to the layers in the modflow model. If I assign Hk and Hv within each layer's attribute table it works correctly, but when I assign materials to a layer it does not seem to work. Am I doing something wrong?
  2. Never mind, I rebooted my computer and now it seems to be working ok. It still does not ask to use the refine points, but it is using them anyway.
  3. I am trying to create a 3d grid for a modflow model. The model will not use the refine points when I go from map to 3d grid. About 1 out of every 6 times that I try to create the grid, it will ask me if I want to use the refine points, but even then, it still does not use them. The interface goes to the default grid creation menu with nothing grayed out. The cell size and bias should be grayed out. I tried to create the grid in GMS 10.0 and 10.1 and I get the same results. This is a small simple 2 layer model with 4 wells, nothing else. I brought up an old working model from last year and tried to recreate the grid, and GMS will not use the refine points in that model either. Last year this old model worked perfectly. Is anybody else having problems with refine points?
  4. Thanks, I guess that I forgot that second step.
  5. It seems that the "Layer Contours to Arcs" command no longer works in GMS 10.0.5. I get a dialog box that says it has completed, but there are no shape files in the output directory. The function also does not ask the same questions that previous versions of GMS asked. Is this command still supported?
  6. I was thinking that maybe the grid had gotten corrupted, so I deleted the grid frame and grid. Then created a new grid frame and grid. I created a new modflow model and mapped my model to modflow. On the first run, the whole of layer 1 was brought down to elev. -3.5. No slope, just a flat gw elev across the whole model, it seemed to ignore all of the boundary conditions. I then remapped the model without changing anything and ran it again. This time it picked up the boundary conditions and wells correctly, the the groundwater drawdown is different from any of the other runs that we have had.
  7. I have also noticed that on some runs, areas within the upper layer of the model dry out. They are discontinuous random blobs of dried out cells. These are in areas of the model where absolutely nothing should be happening. They are a long way from where my well is, plus, the well does not go to the bottom of the layer, so nothing should ever dry out. The well is not drying out, so things further away from the well should definitely not dry out. Sometimes when I rerun the same model, the whole grid dries out.
  8. I tried to check the 64bit box in the Global settings for MODFLOW thinking that it might give me greater accuracy, but the program immediately crashes when I try to assign a starting head to the model if the 64bit box is checked. Update, I don't think that it is the 64bit check box, because it sometimes happens without it being checked. It seems that if you run it one time without setting the starting gw (ie let the gw default to the top of the layer), then set the gw to the correct elevation prior to the second run, then GMS wont crash. By the way, you get a different answer if you set the gw vs if you let it default to the top of the grid.
  9. I have tried ver. 9.2.6 and ver. 10.0.4, and I get the same varying results. The differences are not small. I am running a pump test and the latest 2 runs show a drawdown of 5.7' 25 ft. away from the pump well and the next run showed 6.6 ft' drawdown 25 ft. away from the pump well. Both measurements were taken at the same cell. I am using Modflow 2005, Parallel, with the PCG2 solver. I will email the files to you.
  10. Can you have an unstable MODFLOW model that still converges every time? I have a steady state model that runs to completion each time, but it gives me a different answer each time I run it. If I run the model over and over I get the same answer. But, if I close out GMS, then reopen GMS and run the model, I get a different answer. Or, if I change a k and remap, then change it back to the original and remap, I can get a different answer. This is driving me nuts and its put this project way behind schedule. Any help would be appreciated.
  11. I have been using vertical drains as wells in my model. This works ok as long as the drain is in the upper most layer. But, when the vertical drain runs through several layers, the adjacent cells in the upper layers go dry and then there is no lateral inflow into the drain/well from these upper layers. The water then has to flow vertically down into the next layer and then horizontally over to the drain. This causes the water level in these adjacent cells to rise inappropriately. It seems like I need to somehow model a seepage face along the vertical drain column to allow water to continue to simulate flow into the well casing. Is there any way to allow the water in the cells adjacent to my drain to continue to flow into the drain/well?
  12. Thanks.
  13. Thanks, I have been using PCG2, I will try PCGN. I don't see SAMG, is that an add-on package to buy?
  14. Hi, I am trying to get Modflow to run in parallel but have not had any success. When I look in Task Manager I see "mk2k_h5_parallel.exe" running, but it is only using one processor (6% CPU utilization ie 1 of my 16 cores). Is there something else that I need to be doing to get it to access some of the other 16 cores that I have on my machine? I would think that a finite difference model would scale quite well in a parallel environment.
  15. Does a barrier always extend completely through a layer. You can set the default layer range for a barrier and you can also set the elevation of the bounding nodes at each end of a barrier arc. Which one controls?