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Found 11 results

  1. Hi, I'm modeling a contaminant transport with MT3D while activating MNW2 package for multi-layered model. It seems MNW2 package gives appropriate value for head and drawdown. But when I check the concentration after running MT3D, it gives erratic value on multi-nodes well location. I put negative pumping rate on mnw to simulate pumping well and the concentration is exceeding the upper limit of modeling domain. I wonder anybody experienced same (or similar) problems? If so, any suggestion would be appreciated. Thanks, Ki
  2. 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
  3. 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!
  4. Hello !!!!! I am making a simulation of a tracer test with three injection wells (north) and one pumping well (south). On the injection wells we have injected the salt and water for 16 hours and then successively water for two months. After 16 hours of injection (the initial concentration was 330g/l), we started to pump almost the same amount of water injected on the north on the same time span. we have found the Kx values that match the arrival times of the breakthrough curve at the observation points, according to the pathlines. The problem is that I am getting Nacl concentrations that are too high compared with the values I have measured (calculated from the electric conductivity at the observation point converted in Nacl concentration). The aquifer thickness is about 30 meters. My question is, according to the above mentioned; is there any way to reduce the concentration at the observation well (40 meters downgradient of the injection well). There should be no adsorption or other phenomena within the aquifer, or at least we expect that. The concentrations should be around 10mg/l, however, the concentrations I am getting are around 1800mg/L * could it be possible to use double density approach to solve that problem? * RT3D gave me better results than MT3D, setting in both cases NO reaction (tracer transport), but setting in the CHEMICAL REACTION PACKAGE A value for the Linear isotherm a first sorption value of 1e-3, could that value influence a lot? Thanks a lot for your reply and possible suggestions Alexxander
  5. Hello everybody I would like to know if there is a way to tell MT3D to pick up the same time steps i have in a transient flow model, i Have triend several options: * i have an injection occurring only during 2 days, and i want to see the behavior of that injection (Nacl) during 120 days within a field of injection and pumping wells * the transient model of flow has been calibrated for most of the time steps enclosed you can see the characteristics of the time steps at the end I get only 26 stress period in some case with many time steps (26 days) for the transport i dont understand why? though I need 120 day THANKS A LOT FOR YOUR HELP ALEXANDER
  6. Has anyone on this forum seen this error from MT3D? "error: a or b too big, or MAXIT too small in betacf" It happened to me 6 hours into an 8 hour model run. I have tracked this down to a function call to the pearsn subroutine which it turn calls betacf in the Transport Observation Package. The purpose of the function is to calculates statistics on the goodness of fit between model and observed concentrations. It appears to have nothing to with actual solute transport calculations. What triggered the error was a slight change to my specified concentration cells. Maybe MAXIT in the source code needs to be increased? Default value is 100 but I'm not sure if this would do the trick. Rich
  7. A question on GMS coverages for MT3D: Can a coverage be created for parameters in the MT3D Chemical Reaction Package? For example, I would like to set up zones within a model with different sorption coefficients and first-order reaction constants. It does not seem like these options are available when setting up a coverage - am I missing something? Or, is this only something that can be done in Grid Mode. Thanks, Rich
  8. Just came up with a question regarding where to apply different solution schemes for the advection package activated in the MT3D or RT3D model, and the cases are based on the tutorials 1. Can someone please explain further why we choose the Standard finite difference method for both the Sequential anaerobic degradation and BTEX degradation with multiple electron acceptors, MMOC for the Rate-limited sorption reaction, MOC for both Instantaneous aerobic degradation and Double-Monod model, 3rd order TVD (ULTIMATE) for all MT3D tutorial cases, etc. If there were relevant recommended reading resources, that would be greater. 2. In the Rate-limited sorption reaction tute, what is the meaning of changing Max. number of cells any particle will be allowed to move per transport step to 2 in the Particle dialog of the Advection package? 3. How to save multiple solutions as a .rts file like what it supposed to import in the Rate-limited sorption reaction tute. Because each time I ran the model it would overwrite the existing solution with a new solution of both Aqueous and Soil given a certain mass transfer coefficient. How to come up with a solution with different runs (i.e. different mass transfer coef in one solution file? Thanks, Dylan
  9. Hi. I am trying to create a simple saltwater intrusion model (The Henry Problem) where I include direct age modelling. For this I need two species: "Salt" and "Age". At the western side of the model I have a constant head boundary with constant salt concentration. In the eastern side I have a constant flow boundary with constant concentrations for both Salt and Age. The problem is that I haven't found a way to implement the constant salt concentrations at the western side without having to specify a constant age as well. Has anyone found a way to specify the concentration of only one out of several species? Your help is appreciated Lau Petersen
  10. Hi, I am simulating a confined aquifer problem. My cell size in the grid is 1m by 0.5m. When I run MT3D simulation, it get crashed before completion. Please let me know what can be the reasons to it and what changes should I consider making in my model. I have attached the picture of simulation progress window. Thank You
  11. I'm using the Transport Observation Package (TOBS) with MT3DMS in a simple GMS model (v10.0.10) for testing purposes. I noticed that when the Transport Observation Package is active, calculated concentrations at observation locations are not being interpolated from its neighboring nodal points. This is in contrast to how GMS reports concentrations when the TOBS package is not activated. I checked the TOBS input file (*.tob) and noticed that the iConcINTP flag which controls how TOBS handles interpolation is set by GMS to zero (no interpolation). The benefit of the TOBS package is that it calculates mass fluxes at groups of source/sink boundary conditions. I do not believe that GMS can do this in post-processing without the TOBS package active. Based on the above, I have two questions: 1) Is there any way to tell GMS to turn on the interpolation in TOBS on so that interpolation is performed? I was able to turn it on manually by saving in GMS, opening the TOBS file and changing the iConcINTP from 0 to 1. 2) I'm wondering if interpolation "on" (iConcINTP = 1) should be the default option in GMS since the output would be more consistent with how GMS does post-processing on concentrations at observation points. Any insight on this would be appreciated. - Rich Carbonaro
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