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Greg

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  1. MODFLOW-USG: Recharge Mapping

    Hi Julian, I worked through this problem in another way with the help of Alan. I think the inactive layer is an easier alternative than what we did, but if other features don't work with the inactive layer then this may help. In general what we did is develop an array to identify the top cell in the UGrid. This was done by assigning a dummy KH/KV to the top cells which allowed us to get a list of the cell ids for the top cells. We then saved as native text and re-wrote the recharge file using recharge option 2 and assigning the recharge rate to the top cells and then 0 to all the others. From there I loaded the native text files back into GMS/MODFLOW and removed recharge from the conceptual model and reset the KH/KV with the appropriate value. There are some minor steps and details about how to set up the native recharge files, but I can't remember them off hand nor is it easy to describe. Alan, if I got something mixed up on this please correct me. In the future I will always have layer 1 extend across the model domain when setting up a USG model.
  2. Hi Alan, Yes we can use Zone budget to accomplish the same thing, it would still be nice to use the Zone Flow in MODFLOW-USG so I hope this can be fixed in the future. - Greg B.
  3. CLN Process

    Is there plans to implement more capabilities for the CLN process in GMS beyond just CLN Wells? In theory CLNs can be used in MODFLOW-USG to simulate a 3D tunnel network. Over 50% of the modeling we do could use CLNs to simulate tunnels or adits in dewatering/recovery analyses. Please let me know if this is in the works and if there is a projected release of expanded CLN capabilities in GMS. Thank you - Greg B.
  4. Hi Alan, I am referring to the "Zone Flow" section of the flow budget. When troubleshooting a model it can be useful to look at the flux in and out of selected cells. Can you explain why the Zone Flow is not useful in USG?
  5. Currently you can not get cell to cell flow budgets with MODFLOW-USG. This is a feature that can really help troubleshoot problems and analyze if the model is behaving correctly. Any plans in providing this in MODFLOW-USG?
  6. It would be great if you could add a feature to save the locations of your toolbars. If this is already a feature then please let me know the steps to save them. Thank you - Greg
  7. Adding Layers in a UGRID

    Is there a way to split a UGrid layer into multiple layers in GMS 10.0 or 10.1?
  8. Problems with Modflow model calibration

    If wells only go dry with higher Ks then you should reduce the range of K values in PEST. Another option is remove the obs. points that are going dry with the PEST runs then import the optimized parameter values and compare those to all of the observation wells. If they are still dry then there seems to be an issue with your conceptual model or layer construction.
  9. Hi All, We are working on a large sub-watershed mine dewatering model using MODFLOW-USG where we have to change material properties with time. To do so we are conducting 1 year simulations and stop the model, change the material properties in a new model and read in the previous model heads as starting heads for the next year of dewatering. Although this is somewhat combersome it is working fairly well. Where we are runnigng into a snag is we are using the stream package, which makes it necessary to change the stage in the stream package based on the calculated stream stage from the previous model run. Any help on how to import (copy/paste) the calculated stage from a previous run is appreciated. Cheers - Greg B.
  10. Modeling Low angle fault

    Hi All, I am trying to model two high angle faults (>80 degrees) and two low angle fault (~60 degrees) and was planning on using the HFB package for all of the faults to simulate the high gouge content in the hanging wall of the faults. This works great for the high angle faults where I have assumed them to be vertical, however with the lower angle faults there seems to be some potential for vertical pathways were there are larger layers in the lower portion of the model. Is there any way other than just changing cells aquifer properties to limit vertical flow? Thank you - Greg
  11. Please let us know when the CLN Package in MODFLOW-USG will be available in GMS. I have many projects that I could use this on. One is just starting up, with 2-3 starting later this year. The other request I have is for GMS to develop a scheme to allow for Time Varient Material Properties. I understand that MODFLOW does not allow for TVM properties, but it seems like there could be a sub routine that the GUI could implement to make it significantly easier to model projects where the aquifer properties are altered.
  12. Material properties changes

    Hi All, I am in the planning phase for a groundwater flow model of an underground mine dewatering project to evaluate mine inflows and effect on water resources in the area of the proposed mine. The mine plan consists of using paste backfill throughout all of the stopes. It is estimated that the hydraulic conductivity of the paste back fill will be 2-3 orders of magnitude lower than the native rock (storage will also change). I have worked with models that implement changing material properties by use of cascading models (export heads from transient model run, change material properties and run next stress period and repeat). This is tedious and I have never been too comfortable with the stability of the model between the model runs as you are not importing steady state heads into the next model. I would like to use MODFLOW to complete this analysis, but have concerns with drying up cells (which I hope will be better with MODFLOW-USG using the NWT re-wetting) and stability of model between model runs. Can anyone give advice as to MODFLOW being appropriate to conduct this analysis or if there are alternatives to using a cascading model approach in MODFLOW? I know this could be modeled using a finite element-variably saturated flow model in FEFLOW, but for many reasons (one being the client does not want to go there) I would like to avoid it if I can. Thank you for any input in advance. - Greg
  13. Dewatering Analysis

    Thank you Alan. I will review these and let you know if I have any questions. - Greg
  14. Dewatering Analysis

    Hi All, I am working with a client to simulate a mining project where we want to construct a regional model to evaluate mine dewatering effects on the local surface water bodies and groundwater sources in the area, and evaluate recovery of the groundwater system once mining is complete. The mine is designed to use cut and fill techniques with the fill material consisting of different hydrologic properties. There are multiple lithologic layers beneath the water table that will be removed from the cuts. I am considering using GMS/MODFLOW for this analysis, however I am concerned how it will handle the dewatering of the multiple layers and how to limit instability in the model due to the drying of cells and then rewetting of cells with the new material properties. I have tried to simplify the problem in some initial modeling efforts by use of a 2D horizontal model and averaging hydraulic properties between the different lithologies; however the regulatory review would like a more complete analysis. So I have a few conceptual ideas on how to handle this, and was hoping I could get some input. To handle the changing material properties I would most likely use a cascading model scheme where you would set up multiple models with different cuts and change the material properties for the appropriate cut as the mine advanced. Using the heads from the previous model run as the starting heads for the subsequent run. This seems fairly straight forward although it will be cumbersome. Use of rewetting has always been an issue with instabilities in MODFLOW models, however I have not tried them since GMS 6.5 so I may need to brush up on any improvements. If rewetting is a viable option for this analysis, can someone point me to some documentation that I can review to see how it has been improved. I will continue to conduct web searches, but in my initial reviews this topic is hard to find a good reference. The other possibility I have contemplated is modeling the system as confined and applying unconfined storage parameters to the alluvial systems and where the cuts will be applied. I have used this technique with success in transport modeling of steep/thin water tables; however in a dewatering project it seems that the change in thickness could be significant. I would assume the significance of the change in thickness would be greatest near the dewatered areas and it would become less significant at areas where there is limited dewatering.Any advice or constructive criticism of my conceptual plan would be appreciated. Thanks in advance - Greg
  15. Mine Dewatering

    Hi All, I am working with a client to simulate a mining project where we want to construct a regional model to evaluate mine dewatering effects on the local surface water bodies and groundwater sources in the area, and evaluate recovery of the groundwater system once mining is complete. The mine is designed to use cut and fill techniques with the fill material consisting of different hydrologic properties. There are multiple lithologic layers beneath the water table that will be removed from the cuts. I am considering using GMS/MODFLOW for this analysis, however I am concerned how it will handle the dewatering of the multiple layers and how to limit instability in the model due to the drying of cells and then rewetting of cells with the new material properties. I have tried to simplify the problem in some initial modeling efforts by use of a 2D model and averaging hydraulic properties; however the regulatory review would like a more complete analysis. So I have a few conceptual ideas on how to handle this, and was hoping I could get some input. To handle the changing material properties I would most likely use a cascading model scheme where you would set up multiple models with different cuts and change the material properties for the appropriate cut as the mine advanced. Using the heads from the previous model run as the starting heads for the subsequent run. This seems fairly straight forward although it will be cumbersome. Use of rewetting has always been an issue with instabilities in MODFLOW models, however I have not tried them since GMS 6.5 so I may need to brush up on any improvements. If rewetting is a viable option for this analysis, can someone point me to some documentation that I can review to see how it has been improved. I will continue to conduct web searches, but in my initial reviews this topic is hard to find a good reference. The other possibility I have contemplated is modeling the system as confined and applying unconfined storage parameters to the alluvial systems and where the cuts will be applied. I have used this technique with success in transport modeling of steep/thin water tables; however in a dewatering project it seems that the change in thickness could be significant. I would assume the significance of the change in thickness would be greatest near the dewatered areas and it would become less significant at areas where there is limited dewatering.Any advice or constructive criticism of my conceptual plan would be appreciated. Thanks in advance - Greg
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