Thursday, November 08, 2007

Better HUF Support

GV 5.09 Build 6

HUF (Hydrogeologic Unit Flow) was a new package added to MODFLOW2000 and MODFLOW2005. It allows you to define hydrostratigraphic layers that are independent of actual model layers. MODFLOW then computes a composite transmissivity based on the HUF layers that intersect each model layer. Not a bad idea.

GV5 supports HUF but the trick is how to get the HUF data into the GUI since GV really only tracks actual model layers. Here are the basic steps you need to follow to use HUF in Groundwater Vistas:

(1) Use Model/MODFLOW2000/Packages and enter a non-zero number next to HUF and check the 2nd column to create it. Put a zero next to LPF to turn that one off and uncheck 2nd column.
(2) select Model/MODFLOW2000/Options - HUF tab. Enter the number of HUF layers you want to use.
(3) add property matrices. This is done using Props/Surface Data. Each "surface" is a 2D matrix in row-column order just like MODFLOW reads it. You will need a matrix of top elevation, thickness, Kx and Kz at a minimum for each HUF layer. You add them by first creating a new one and then using either import or one of the edit commands to fill it.
(4) after adding all of the matrices you need, go to Model/MODFLOW2000/Huf data and select the surfaces for each huf property you need for each huf layer.

So that gets a bit tedious defining those surfaces or arrays. In order to make it easier to use HUF, we added a new export/import. The idea is that you create two GV models. One has the definition of all HUF layers (you don't need boundary conditions or other stuff) and the other has the number of model layers you actually want to use when running MODFLOW. Each must have the same number of rows and columns. You define the HUF model first and then use Props/Export/HUF Data Arrays. Then go into the final model and use Model/MODFLOW2000/HUF Data Import.


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