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Found 42 results

  1. Hi All, I am trying to calibrate a MODFLOW model using PEST. My model has multiple layers (12). However, I do not know how to parameterize the model. Aquaveo tutorials explain it as specifying hydraulic conductivity and recharge values are negative values in different areas. However, I am not able to do this because my model is developed in such a way that these Hydro-geological properties are specified as a properties of materials and these materials are assigned to different areas in each layer. Would you please help me to parameterize my model? Thank you, Lalith
  2. Dear all, I am trying to model a “subsurface dam” using the Horizontal Flow Barrier (HFB) package which simulates thin low-permeability geologic features to impede the horizontal flow of groundwater. I have a model with two alluvium layers which are shown in the attached schematic figure. In the HFB package, the cell boundary represents a vertical face between two adjacent cells. The question here is how I can define a barrier within one cell (layer) up to a specific level rather than the whole cell thickness (like layer 1 in the figure). Your help and insight would be highly appreciated. Best regards,
  3. Hi, I have recently started using the UZF package to simulated groudwater flow in a regional model. I firstly developed a steady state model using spatially distributed recharge from a surface model. I was using the «recharge» and the «EVT» package. With this configuration i was able to obtain a water budget with % error < 0.001%. When i replaced the recharge and EVT packages by the UZF, the water budget output file shows a line with a component called «HORT+DUNN» which i suspect to be the surface runoff flow. This component is not well describe in the USGS MODFLOW documentation. The problem is that this volume of water is only present in the «IN» part. In then creates a poor water balance ~1% to 5% error. If i remove it from the balance, the % error is good (> 0.01%). Any idea of how to deal with this water budget component? Regards
  4. Dear all I have trouble modeling a square site with different BC. at one side I have river (I put constant head as BC) and no problem in that for modeling. now, 1) at one side I have rock (no flow coming in or out from site at this side) and 2) at other side of square area I have no BC (I mean the water can flow out of area etc) what is the difference in modeling number 1 and 2? how to difine them in my model? my model currently have active cells in coverage so I think it means all sides I have rock, right? Thank you, Zara
  5. Hello, Can anyone please tell me that how velocity is calculated from flow data in GMS(not through GUI). Though I had already referred to the following the link: https://www.aquaveo.com/blog/2012/05/15/velocity-vectors ,the velocity calculated by me is not matching the velocity obtained through GMS. I had applied the following for the calculation of velocity: V = Q/(saturated_area*porosity); where, Q is the flow through a cell face, obtained from ccf file, Saturated area = (head-bottom_elevation)*cell_width {for unconfined aquifer} and head is obtained through .hed file. Thanks in advance. Have a great day!
  6. Hi, I have a problem regarding flooding and wetting which makes it difficult to calibrate the model. It is representing a coastal area with thin clay layers and sandy till which we assumed to be 1 m each. The two bottom layers represent rock with the upper one being fractured and thus have a higher hydraulic conductivity. The surfaces are imported from ArcMap and ranges between 30 and 0 m. constant head and no-flow was assumed.The main problem I found is that the groundwater table is almost completely flat in contrast to the terrain. Any ideas of packages, solvers or any tips in general, of how we can tackle the issue. We are thankful for any answers that could help us!
  7. I would like to be able to export the MNW1 package to a shape file or some other format. Or create point features. Is that possible? Not every modeling project begins from scratch. Many times you start with someone else's model (say a USGS model) and want to develop the map data/feature objects from that model. It seems like GMS doesn't serve that pathway of development well.
  8. Refining a regional steady-state model where the local grid boundary intersects rivers and drains (see image). I went through the tutorials for SS refinement. This model departs from that example in a couple of ways - flow field is not nicely uniform in area; and MF BCs are intersected. I created 4 arcs initially to set up the boundary of the local model. Then I started to wing it - created nodes at each intersection of 1' head contours to map constant heads to the arcs but I'm thinking that may not be the best way to go. Any suggestions on a strategy for mapping the heads and the BCs to the local model are much appreciated. Ted
  9. Hi, I'm relatively new to the GMS software and have performed a few of the basic tutorials Aquaveo provides. I have XYZ data that provides spatial reference to every observed pressure points/head values. These points are evenly spaced/gridded. I would like to create a MODFLOW simulation with these pressure data. To my understanding, the best way about creating this model would be to generate a raster that stores XYZ and P data (GeoTIFF). Theoretically, I'd like to create a 3D grid that stores these X, Y, Z, and P data. From there I'm going to need to create an IBOUND layer that specifies the head based on the P value. I've successfully performed these simulations in 2D space but am unable to comprehend where to start in the 3D space. See the attached screenshot for an example of a longitudinal cross-section of a 2D simulation. Can someone provide me some insight on how to begin setting up this model? Let me know if there are further things I need to clarify.
  10. Hi Community, I am trying to run MT3D-USGS in a model which contains plenty of dry cells computed by mf2k5, but MT3D-USGS chrashes. The .out file reports that plenty of cells have "saturated thickness =0.0000" (i.e. they are dry), "not allowed in transport model" and furthers says "reset as incative". I have attempted to set some of the dry cells as inactive, but those cell still show up as erroneous in the output file. What am I missing, or what can I do to make MT3D-USGS work? - Niklas
  11. Hello everybody I noted GMS has values for porosity in both MODFLOW and MT3D. In MODFLOW menu (MODFLOW options) one can enter values for porosity, although porosity is not used in flow computations as far as I know. Also in MT3D menu it is essential to enter porosity value. In the model I have (which is a SEAWAT model) I entered values for porosity in the MT3D options, but I noticed there are different values -by default- in the MODFLOW options. Which values does the model consider in this case? and why is there an option for porosity in MODFLOW? Thanks
  12. I'm trying to find a suitable work around for modelling flow pathways through abandoned mineworkings, some of which are above the water table (dry) and therefore subject to non-darcian flows. My data, however, is a blanket of worked seams and lacking any tunnel or shaft data (the hope was to use CLN utilising this network data). I am hoping someone may have some experience with battling similar issues? The data is all vector data used in ArcMap and I've noticed that some files will transfer into MODFLOW easily (such as DTMs), yet others like TINS do not. During the initial process, I have a few questions I hope someone with more experience may be able to answer. 1) How to site the workings at their respective heights using Arcmap shape files and TINs. (MODFLOW doesn't seem to like TINS but does recognise them). The shape files are divided by 20-50 meter barriers of solid seam (walls of major blocks), would this kind of shape file transfer when placed into MODFLOW easily distinguish between Open channel flow for the known workings, and a general value for the aquitard wall materials. 2) Once the workings are in place at their respective depths, is there a way within GMS to allow all surrounding lithologies to be generalised (i say this as the local geology is cyclotherms and is made more complex by the inclusion of coal mineworkings). I've included the 3D geology image below, exhibiting the space between the coloured seam workings. 3) Would the easiest way to produce connecting shafts between the various seams be by using wells? Thanks in advance, M
  13. Can you use the LAK Package if you do not have the "sub-surface characterization" component of the GMS software, and therefore, cannot create a TIN? How would you establish lake bathymetry without a TIN? Can you use a raster interpolated from 3rd party software? What happens if you leave the bathymetry portion of the LAK package dialogue blank?
  14. Dear members, I am trying to generate velocity vectors in a density dependent model. The GMS is displaying error, pic of which is attached below. I have been generating velocity vectors and never faced any such problem. I am not able to work out solution to this problem. Any help would be appreciated. Thank You
  15. Hi all, A bit of a simple question but I can't find the answer anywhere in the help files. I've been provided with some ARCGIS TIN's (.adf files within the TIN folder) and I'm struggling to import them into GMS. Is there a conversion that must be completed before this will work or am I missing something really simple as GMS just spits out errors at present. Thanks in advance M
  16. I want to simulate the seepage of water through the base of a reservoir, but I do not know how to do it. I tried to use SEEP2D but I just know how to simulate the seepage of water through levees, earth dam, and sheet pile. Please show me which modules of GMS and which model (are currently supported in GMS) I should apply for this case. Kind regards, Quoc Tran
  17. hello, i have a transient groundwater - surface water GMS model and I need to export river leakage values for single cell for all the time periods. is there a simple way to do that? i can access the leakage value via the sources/sinks menu but only for the selected timestep. thanks.
  18. Tom said to mention this here on behalf of technical support. When exporting native text MODFLOW files, the files are not updated with new information. For example put new information into the MODFLOW | Global Options | Optional Packages | RCH package and click OK. Unless the project is manually saved after making the edit and before exporting the native text file those changes aren't saved, but users may not realize clicking OK doesn't update the files. It may be helpful for the user to receive a reminder that 'You have not yet saved your changes to the model. Would you like to save these changes before exporting the native files?' or something along those lines.
  19. Hi everyone, I am currently doing a project regarding in-situ chemical oxidation of BTEX using persulfate solution, and trying to use RT3D to represent the process. As reading the literature the reaction should be a pseudo 1st-order kinetic reaction model, but the only relevant option I found in the reaction package is the inst. aerobic degradation of BTEX which only offers oxygen as the electron acceptor. In this case, could someone familiar with the persulfate or other similar oxidation mechanisms tell how to construct the RT3D model? convert the persulfate concentration to an equivalent oxygen concentration? or should I try more options other than MODFLOW? Regards Dylan
  20. Hi all, I have come up with some errors when running the tute model of TUTE: MODFLOW – Generating Data from Solids that indicate “changing heads are below the bottom of cell xxx". It is so weird that a tute brings up a problem like this. Having read a thread in the forum suggesting to remove the BC of constant heads from the sources sinks coverage, I found many cells dry out with red triangular flags after a modflow run. I knew it was different from what is instructed in the tute sheet, but it seems plausible for me that without those BC these cells could dry out. A further question is, i was constructing a more complex multi-layer solids model and tried to convert to modflow. My BCs are constant heads set on the arc of the coverage boundary, kind of surrounding my small catchment of interest, and they are definitely all below the bottom of my first, second and part of the third layer, so how to define the default layer range? (i.e. from 1 to 1, 3 to 12 as I have 12 layers in total, or 1 to 12?). PS: in this coverage I define wells, specific head, layer range for source sink and layer range for areal properties, and tick used for BC option. The first trial I have set was 1 to 12 (dont know if appropriate), converted map to modflow, and could see the blue dots assigned from layer1 to 12 of my conceptual model. All of them indicate the some heads I define in the coverage. (Really? Does it have to be a 58 m head in the even very bottom of my rock layer of 30 m elevation?). As expected, the model warned that lots of heads were below cells' bottom. When removing all of them in sources sinks and running the model in steady state, I found it never converge. A feeling was that I did it wrong when defining BCs. This is where I got confused. Could anyone kindly help? I am using GMS Version 10.0 Thanks for any help Rgds Dylan
  21. Hi, I've been trying to calibrate my transient model using PEST, however I'm experiencing some difficulties. It executes the estimation process and finishes the parameter estimation but it fail's to give me any new values for the chosen parameters. This only happens when I try to calibrate it as a transient model. When I run it in steady state there are no problems and it estimates new values for my parameters. When I run it as a transient model there is a message in the PSLAVES windows that pops which states that the "Total sum of squared, weighted residuals: NaN", and I think the problems lies here. However I'm not sure how to fix it. If anyone has any idea what's causing this and could help me with a solution I would be very grateful. Jonas
  22. I am using GMS 10.1.3 and trying to import a MODFLOW NWT model obtained from the USGS. The model appears to import okay, but when I run MODFLOW, it quits after several seconds with the note "MODFLOW terminated with error!" The OUT file states "model stopping due to reach altitude error." Upon further examination of the OUT file, there are warnings for each stream segment that "upstream elevation is equal to or lower than downstream elevation" and the streambed properties listed in the file indeed streambed elevations all set to zero. Looking at the SFR2 package through GMS shows all stream segments ELEVUP and ELEVDN set at zero for stress period one. For all other stress periods, there is data provided for ELEVUP, but ELEVDN remains universally set at zero. I can copy the ELEVUP data from a later stress period and apply this to stress period one, but without ELEVDN data, the altitude errors still occur, terminating MODFLOW. It appears that when importing the file, GMS does not pick up the streambed elevation data. Any help will be much appreciated.
  23. I'm a newer user building a MODFLOW model that I will then need to teach others how the model was constructed, I am establishing a coverage for the WEL package that will use a point shapefile from another model to inform the location and pumping/abstraction rates. One of the attributes in the shapefile is "Layer", identifying the layer of the well in the 10 layers of the model. I was shown how to create the coverage but I wanted to understand the rationale for selecting the Layer Range item in the Source/Sink/BCs list. I'm guessing this allows the use of the Layer attribute to map the points to specific layers in the Solid and Grid models, assuming they appear within layers 1 to 10, as specified. Also, I had a question about the "Use to define model boundary (active area)" check box. I have conflicting information as to when that should be checked in a coverage. My intuition tells me that is would only apply to feature objects that define the model boundary and not necessarily other boundary conditions that are applied to the model boundary conditions. For example, given one coverage (a polygon) that defines the extent of the active region of the model across all layers is create with the "Use to define..." item checked. If separate coverage was created that defines a constant head on layers along one edge of the active model domain, already identified as active in the other coverage, does the box need to be checked? When should it be check and not? Is there a danger in checking the box when it shouldn't. Any insights are appreciated Ted
  24. Hi, I need to know if it's possible (and how) to export with GMS grid parameter data of a model into shapefile such as : - Ibound - Hydraulic conductivity, Anisotropy - Porosity, Ss I've already exported CCF file with the Export function (see my previous topic) but it didn't include all the modflow code/parameters. Can you help ? Thanks
  25. Hi everyody, I work with GMS 10.1. I need to export the information of flows of a steady state model realised on Modflow 2005 with GMS. Is there a way to recuperate a file in ASCII form (or equivalent) with flow values of every faces of the mesh's of the grid ? Thanks for your help
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