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Kirk

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I would like to set up ET for a surface defined by a tin (based on DEM), but when I create a coverage, it seems to just ask for "ET Elevation". Can I select a surface to set ET elevations for individual model cells within a larger polygon?

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Kirk,

We had the same issue recently (18 September 2015), with the option for "2D Dataset -> Array" being greyed out, and were given this work-around from Jack at Aquaveo support. It seems to have worked.

"Currently the option to use the "2D Dataset -> Array" command for U-Grids is not available, however I believe that the developers are working to implement it in future versions of GMS.

I've got a possible work-around for you. This assumes that your topographic surface can be represented as a 2D scatter set or TIN. In this case right-click on your U-Grid and select 3D->2D, and then select layer 1 so as to make a 2D U-Grid of the top layer of your 3D U-Grid. This ensures that the cell IDs of layer 1 in your 3D U-Grid line up with the cell IDs of the 2D U-Grid. Now select the 2D U-Grid to ensure that it is the active U-Grid, and select the topographic surface data that you have and convert it to a 2D scatter set. Then interpolate that 2D scatter set to the 2D U-Grid. Now you will right-click on the interpolated dataset on the 2D U-Grid, and select "View Values". Copy the column of f values here, click ok to exit that dialog and bring up the dialog for the EVT package on the 3D U-Grid. Now paste in those values to the array for the EVT package. You can check to make sure that the cell IDs are the same and line up all right. If you have trouble doing this, please let us know."

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Alan L., see also Rob Virtue's note below. Thanks Rob for sending this workaround, in case Alan's method seems problematic.

Alan,

indeed the 2D dataset to Array function is greyed out in my GMS application, as noted by Rob. I will try your approach, with the hope that if I have a 2D dataset created and turned on, then the function may be available (i.e. not greyed out). I'll give it a try. I have sent the files to Aquaveo technical support, maybe they will show me the same thing.

Kirk

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Hi. I am attempting to apply the concepts Alan L. and Rob have brought up. One problem is that I do not know what a U-GRID is. Also, Alan your method sounds very straight forward. But can you possibly explain the steps a little more? How do I interpolate the ET surface to a matching 2D grid? I tried just selecting "grid" in the Project Explorer, and "Convert to" 2D grid, but no top elevation seemed to come into the 2D grid. I need more detailed instructions, but can always revert to entering them all manually.

Meanwhile, Kyle with Aquaveo support sent me some instructions too. I'll call Kyle and see if perhaps he can walk me through the steps.

Kirk W.

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If you don't know what a UGrid is then ignore the instructions from Rob for your case.

To get a matching 2D grid....

1. Right click on the 3D Grid in the project explorer and select the Convert to | 2D Grid command.

2. Select Ok at the prompt to set the default elevation of the 2D Grid (this value won't matter for what we want to do)

Now you will need to interpolate to the 2D Grid so you will have to convert your TIN to a 2D Scatter Set.

1. Right click on the TIN in the project explorer and select Convert to | 2D Scatter Points command.

2. Right click on the 2D Scatter point in the project explorer and select the Interpolate to | 2D Grid command.

Now you have a data set on the 2D Grid that represents the ET Surface. We want to take that data set and apply it as the ET surface array.

1. Go to the ET package in MODFLOW. MODFLOW | Option Packages | EVT ...

2. Make sure the ET Surface array is being shown in the dialog and now select the 2D Dataset -> Array button.

3. Select the data set that you interpolated to your 2D grid.

Now you ET Surface is set.

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Thanks for your detailed reply, Alan, I appreciate this. I will see if I can get that method to work. I am in a testing phase at the moment, working out my methodology for applying the ET in the model.

Meanwhile, I just emailed Kyle at Aquaveo a solution that also seemed to work. Here is what I wrote Kyle:

Well, I think I have succeeded in getting my elevations placed in the ET package. I simply went to MODFLOW – Global – Top in the Project explorer, and selected “properties.” I clicked on the upper left cell to “select all” of the array. I then opened MODFLOW – ET – ET Surface and again selected all, and used “paste.” It seems to have populated my ET array with surface elevations. That is what I had in mind, so I believe I am good-to-go. However, if you do find a better way to do it, why please let me know. Or, if what I did is not OK for some reason, please let me know that too.

Alan, if you think my method might cause me problems, please let me know.

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A final note: Thanks for the assistance. I followed the steps provided by Alan, and found that the virtually the exact same elevations were reproduced in my MODFLOW ET package as using my copy and paste method. Nice demonstration of how well the software works with elevation datasets. I actually had saved the USGS NED dataset as 2D Scatter points, so just interpolated that product onto the 2D Grid. This worked great.

Kirk

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