ESI Quarterly Webinars Start in June

I presented a free webinar at the end of March on our new software versions.  That was very well received so I want to continue offering these free one-hour webinars periodically.  The next one has been scheduled for June 16 at 11 am and 8 pm Eastern time in the US.  I will talk about the status of our new software versions and highlights from the MODFLOW Conference.  You can sign up at groundwatermodels.com - there are links right on the main page.

MODFLOW-USGs

For those of you attending the MODFLOW Conference at Colorado School of Mines in a couple of weeks, I will be demonstrating the use of nested grids in a new version of MODFLOW called MODFLOW-USGs, developed by Sorab Panday. We use the term nested grid to refer to a refinement to the finite-difference grid where the grid lines do not extend beyond the refined area, as shown above. This greatly reduces the number of grid cells. It is similar in concept to MODFLOW2005-LGR (Local Grid Refinement), except that MODFLOW-USGs is one simulation rather than two. Chris Langevin and Sorab Panday will both be presenting papers on this new style of MODFLOW modeling and on MODFLOW-USGs specifically.

Our demonstration will take place on Monday evening, June 6th, from 5:30 to 7:30 in the Green Center, Friedhoff Hall. Please stop by and I can show you more. I will also be posting a lot more about this new MODFLOW version in coming blog posts.

Hope to see you there.

GV with MODFLOW-NWT on the Web

Just a quick note that Groundwater Vistas 6.04 Build 1 with MODFLOW-NWT is on our web site! Update installers and the full installers both have this version in 32-bit and 64-bit flavors.

MODFLOW-NWT Source Code Released

And there was much rejoicing... The MODFLOW-NWT source code is out now (see link below). We will have it hooked up in Groundwater Vistas Version 6.04 Build 1, probably by tomorrow. If you see 6.04 build 1 on our web site (www.groundwatermodels.com - click Clients/Downloads), then you know we have added MODFLOW-NWT.

So now you'll probably want to know how to use it. It's actually pretty easy to get it working because it's essentially MODFLOW2005 with a new solver. So here is what you need to do:

1. Select Model|MODFLOW|Packages and change the version to MODFlOW2005
2. You must use the LPF Package (BCF not supported). The easy way to make that happen is to turn on "Automatically Reset Package Units" in step 1.
3. Select Model|MODFLOW2005|Packages and turn on the checkbox that says "Use Upstream Weighting (UPW) and Newton Solver (NWT) instead of LPF Package"
4. Select Model|MODFLOW2005|Options and click on the "NWT General" tab. The NWT Solver has lots of options under this tab and the one labeled "NWT Methods". See notes below on the solver settings.

That is all you need to do. The next time you run the model, you will be running MODFLOW-NWT. We do have a windows DLL version, as well as the USGS command line versions in both 32-bit and 64-bit flavors.

Just a note on the solver settings. There are a lot of settings but one thing I really like about the implementation of this NWT solver is the use of an OPTIONS variable that can be SIMPLE, MODERATE, COMPLEX, or SPECIFIED. If you choose one of the first 3 settings you eliminate most of the settings and NWT will configure itself. We are defaulting to MODERATE in Vistas but we'll see how that goes. As we gain more experience we may change that. Anyway, if you choose one of those first three settings then you only need to set the following variables in the solver:

HEADTOL, FLUXTOL, MAXITEROUT, THICKFACT, LINMETH, IPRNWT, and IBOTAV

These variable names are listed on the GV dialog and they are all on that first tab mentioned above.

One other note on MODFLOW-NWT is the specification of dry cell head. We have set up GV so that cells will not show up as dry. This is essentially the same thing that MODFLOW-Surfact does. If you would rather see dry cells, there is a checkbox on Model|MODFLOW2005|Options - LPF Options tab called "IPHDRY". Turn that option on if you want to see dry cells. There is one other option there that is for MODFLOW-NWT which will reduce pumping rates in cells that become desaturated. See the MODFLOW-NWT manual for more information.

We have noticed some lingering "stack overflow" problems with both MODFLOW2005 and MODFLOW-NWT so if your model crashes please send us the GWV file so we can figure out the cause. We have tried to test this on large problems but there is no guarantee that we caught all of the problems. This is a long story - corner me at the MODFLOW conference in a couple of weeks and I'll bore you with it.

Here is the link. It is not live yet on the USGS Groundwater Software page but should be soon.

water.usgs.gov/nrp/gwsoftware/modflow_nwt/ModflowNwt.html

MODFLOW-NWT Documentation Released

The documentation for the new MODFLOW-NWT code is now on the USGS web site (see link below). This new version of MODFLOW offers a Newton formulation for nonlinear problems, especially those involving drying and rewetting of cells. It is a special version of MODFLOW2005 that has a new solver (NWT) and a new version of the Layer Property Flow (LPF) Package called the Upstream Weighting Package (UPW). The format of the UPW Package is virtually identical to LPF so the transition to MODFLOW-NWT is relatively simple. It's really just a matter of substituting a new solver file.

MODFLOW-NWT handles dry cells in a manner similar to MODFLOW-Surfact's pseudo soil relations. So if you do not want to spend the money for MODFLOW-Surfact, then MODFLOW-NWT is a viable alternative. The downside is that MODFLOW-NWT can be slower than MODFLOW-Surfact. I have confirmed this with some test problems and real models. But it works!

The source code should be available in a few days. As soon as the source code appears on the USGS web site we will activate this feature in Groundwater Vistas Version 6. I will make another post when that happens.

Link to MODFLOW-NWT manual: http://pubs.usgs.gov/tm/tm6a37/

SEAWAT2000 Update Released

The USGS released an update to SEAWAT2000. The new version is called 4.00.04. The update fixed a problem with the drain observation package and the transport observation package. Apparently there were also reports that the program did not run on Windows 7, although I never had any problems with that. Both 32-bit and 64-bit executable files are provided.

The new version of SEAWAT2000 will show up in Groundwater Vistas Version 6.02 Build 12 later today or tomorrow. If you would like to download SEAWAT2000 from the USGS, use the following link:

seawat2000 download link