Friday, January 06, 2012

Happy New Year

We hope your holidays were great!

We have been busy, as usual, trying to keep Groundwater Vistas up to date.  There have been three major things added since my last posts before the holidays.  These include (1) tied parameters in Pest, (2) modifications to how Storage pilot points are handled, and (3) a new update for MODFLOW-NWT.

Tied parameters in PEST are those that are modified based on how another parameter changes during calibration.  A common example is vertical hydraulic conductivity, which may be set as a multiple of horizontal hydraulic conductivity.  PEST would estimate horizontal K and then vertical K is automatically adjusted based on the new horizontal K value.  We have had some of this sort of thing in the past with pilot points (see previous posts) but this new feature works with any zone-based or reach-based parameter.  Step 1 is to define every parameter you need (including the ones that are tied) under Model|Pest|Parameters.  In Step 2, select Model|Pest|Tied Parameters.  The parameters on the left side of this spreadsheet are ones from step 1.  For those parameters that are tied, enter the parameter they are tied to on the right.  Just leave all untied parameters unchanged.

In previous versions of Groundwater Vistas, the storage pilot point represented the primary storage coefficient of a cell.  For a type 1 layer using the BCF Package, this would be specific yield.  For type 3 layers in BCF or unconfined layers in LPF, where the water table was lower than the layer top, this would also be specific yield.  For all other conditions, the pilot point would be the storage coefficient in BCF or specific storage in LPF.  We now have two types of storage pilot points in GV6, Storage (or specific Storage) and Specific Yield.  When starting a new model in Vistas or opening an older model that did NOT have storage pilot points, the new approach is used.  If you open an older model in Vistas that had storage pilot points, GV will default to the older legacy approach so as not to change your model.  You can opt for the new approach by selecting Model|Pest|Options - Targets tab.

And finally, a new version of MODFLOW-NWT was released by the USGS on December 29.  Some solver issues were fixed and changes were made to the UZF and SFR Packages.  Note that there is some additional data input for UZF that we do not yet support.  However, your model will still run without these options.  If you review these changes on the USGS web site and need these new options for your model, please let me know so I can make it a higher priority.

All of these changes are in Version 6.14 Build 4 which is on our web site now.

Happy New Year!



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