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bjacoby

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About bjacoby

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  1. If I wanted to export the simulated watertable elevations through MODFLOW, I would select MODFLOW->Observations->Export Trans. Obs. I would like to do the same thing with my MT3D data. Do you know if there is a way to export simulated concentration values for observation points? Thanks!
  2. I am working on a site that has transient/perched water above the saturated zone. Is this possible in MODFLOW? I have read about the UZF package, but am unfamiliar with it. Any guidance/ideas/thoughts would be appreciated. Thanks in advance!!
  3. Steady State vs. Transient

    I have a calibrated Steady State Model that shows my site at current conditions. I would like to know how the water table will react to various closure scenarios of a landfill. To do this, I converted my model into transient and added values for specific storage and specific yield. I created two stress periods and in the second stress period, I made the recharge over the landfill equal to 0 to simulate an impermeable liner. I run the model out 100 years, and the heads in the landfill only drop 10 feet. I was expecting more drawdown, so I decided to run the model as steady state and 0 recharge over the landfill. The steady state model demonstrates 30 feet of drawdown, which is much more in line with what I expected. I returned to the transient model and have adjusted the storage values orders of magnitude up and down and do not get any change in my final heads at 100 years; at least not more than a few feet. I have tried different solver packages to see if that would adjust my heads and that didn't seem to work either. I have tried to run the model out to 1000 years instead of 100 and this doesn't seem to have a affect on the final heads. Is there another property or function I am missing? Any other troubleshooting suggestions? Any thoughts would be appreciated!!
  4. IBOUND

    Thank you!! I also saw that "MODPATH also uses a copy of IBOUND in it's input and uses the absolute value of IBOUND to indicate special zones.". I did change the MODPATH zones to identify various areas in the model. This might have also affected the IBOUND array. Thanks again!
  5. IBOUND

    I have a model where my IBOUND array varies from 1 to 4. I understand that values < 0 make constant head cells, values = 0 create inactive cells, and values > 1 create active cells, but what does this variation in positive values do to the model? What is the purpose? Thanks, Brianne
  6. Modeling Liner Placement

    I am working with a transient model of an impoundment. The impoundment will be lined over the course of 10 years. Currently, there is a 100 acre pool on one end of the impoundment. I have this pool modeled via the river package. I have modeled the liner by adjusting the RCH to 0 in various areas, equivalent to schedule for liner placement. about halfway through liner placement, the pool is lined. To model this, at the 5 year timestep, I adjust the RCH to 0 and the river package conductance to 0. My model runs fine, but my output does not make sense. After the river package is turned off, I expect a drop in water levels throughout the impoundment over the course of a few months. There is 70 feet of drawdown occurring in the matter of hours. This is not realistic of actual conditions. Does anyone have any ideas on how to trouble shoot this? thanks.
  7. Boundary Condition Issue

    Have you tried to add nodes to your river and GHB boundaries and assign elevations to them? If you add a vertex to a line within the conceptual model, right-click on the vertex and choose convert to node, then you can right-click on the new node and assign an elevation and head value. Do this is a few locations along your arc/line and convert to MODFLOW again.
  8. Starting head initiation

    I have had the same problem with a model I am working on. The only solution I found was to use the rewetting package.
  9. What Processor do you use?

    I have been running GMS 10 and have noticed it is extremely slow. I have a few TINs in my file, a few solids, and a conceptual model in addition to the MODFLOW files. I would not say the speed issue is unique to 10 as I have the same issue when I was using 9. I am running the software on a laptop that meets the requirements established by Aquaveo. Have any of you run into this problem? What processor do you use? How much RAM do you have? Have you been satisfied with the performance? Thank you for your time. -B
  10. Basic MODFLOW question

    thanks!
  11. Basic MODFLOW question

    Thanks Alan. Here: http://water.usgs.gov/nrp/gwsoftware/modflow2000/MFDOC/index.html?chd.htm It talks about the CHB being time-variant. How can that be if the head is specified?
  12. Basic MODFLOW question

    What is the difference/advantage/disadvantage to using the River Package verses a Changing Head Boundary Condition? I am having trouble understanding the function of each. Any comments are appreciated! Thanks!
  13. I have 5 layers in my model, all of which are at different elevations. This model was created prior to GMS' existence and has confining beds between each layer. We have modeled this by setting space between the bottom of layer 1 and the top of layer 2 and so on for all the layers. Whenever I go into the Elevation Arrays and change the values so that this space is evident, it only "sticks" to cells that do not have a layer above it. I have gone into MODFLOW|Global Option|Confining beds and selected that a confining bed be in place beneath layers 1-4. I am using GMS 8.3. Do you know why I can't make specific elevation ranges for every cell in a layer and/or how I can fix it so that all cells in a given layer are within a specific interval, regardless if a cell is above it or not? Thank you so much!
  14. Observation Points

    Thank you! That helped in addition to confirming that the layer was Identified correctly in the attribute table. Even though I set up the coverage to apply to a certain layer, some of the points were in the wrong layer. Cheers!
  15. Observation Points

    I have brought a model into GMS that was not created in GMS. The target points from the old model were not transfered over, so I created coverages for each layer (I have 5) and digitized where they were based on grid information I had. The only thing I selected in the coverage setup was Observation Points|head. Then I made sure the default layer range and elevation were appropriate for that layer and obersevation points. 3D grid layer option for obs. pts.: is set to By layer number. I asigned the points elevations within the layer's elevations, made sure the point was actually on the grid, and then saved my file. Once I do that, I get a warning stating that the 'following observation wells were outside of the model grid and were not written into the *.hob file. Check 3D Grid Layer option for obs. pts. in the coverage setup dialog. Also check that any well screen intersects the model grid." Theses are observation points concerned with head, so I don't understand where I can input the screen information. The head values are within the layer elevations. Any thoughts? Thanks!
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