MNW Package Compatibility with MT3DMS (and other questions...)

[mmamobile]

I've generated a flow model using the MNW package to represent several pumping wells - the flow model seems to be producing reasonable results, but I'm not able to run MT3DMS. The error message generated in the MT3DMS window is "ERROR: MAXIMUM NUMBER OF SINKS/SOURCES ALLOWED [MXSS] = 1674 INCREASE VALUE OF [MXSS] IN [sSM] PACKAGE INPUT FILE". When I convert to the WEL package, I have no problems. Am I missing something? I know MT3DMS version 5 was updated to provide compatibility with the MNW package, and from the look of it, GMS is using version 5.2. I've also tried to manually alter the SSM input file, but MT3DMS fails if I do this.

If I can't use the MNW package directly with MT3DMS, is there a simple operation to convert the WEL package generated by the MNW package to something that can be recognized by GMS? More specifically, the WEL package is in standard MODFLOW format, which differs from the WEL package format used by GMS-based MODFLOW simulations.

Also, I'm attempting to use the transient observation (TOB) package in MT3DMS to compare model results to tracer breakthrough at several observation wells. I've gotten to the point where the .OCN file is providing the simulated concentration at each time step (at each observation location), but the file is not showing the observed concentration. Is this due to the fact that my observation times do not exactly match the time steps produced by the solver?

Any help on any of these issues would be greatly appreciated!

Thanks!

[mmamobile]

Following up on this issue: I've been able to get MT3DMS to run with the MNW package, but there seems to be no way to represent an MNW well in the SSM package.

[Alan Lemon]

GMS 7.1 uses MT3DMS 5.2. It looks like MNW support was added to MT3DMS 5.3. We have added this item to our back log to implement in the next version of GMS.

[mmamobile]

Thanks Alan - would replacing the .exe or redirecting to the 5.3 version resolve this issue? I imagine I'd have some manual manipulation of the SSM package to do...

Also, any thoughts on the lack of observed concentration data in the .OCN file?

Edited August 21, 2010 by mmamobile

[Alan Lemon]

Redirecting to 5.3 should work to run MT3DMS. This will probably cause some issues with reading the solution back in. We modify MT3D to output GMS data sets but we can read the native UCN format.

You will have to do some manipulation of the SSM package.

I am not sure what is going on with your observations. Are you still having this problem?

[mmamobile]

Alan,

Yes, I'm still having the issue with the TOB package - I'm thinking the problem boils down to an imperfect match between the model-calculated time step (model time) and the observation intervals. The TOB package (OCN output file) provides model-calculated concentrations at each location at the end of each time step, but it does not interpolate the observed concentrations or take the observation in closest temporal proximity, which results in the OCN file having no "observed" data.

Does that make sense? I don't mind working outside of GMS to compare model predicted and observed concentrations, but it would be nice to use the TOB package to do the work.

Thanks again.

[Alan Lemon]

If you haven't done so yet, can you send your files to support and we will take a look at the TOB problem? If your project has sensitive data could you make a simple example that illustrates the problem. Thanks.