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GMS assigning multiple specified head sources to same cell


Zak_B
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Has anyone else noticed this happening? When a source/sink coverage is mapped to modflow, occasionally some of the specified head bc's seem to get split and assigned in tandem to a single cell. Like for example, say the bc was 1500 ft, GMS will sometimes assign 2 sources to the cell with a seemingly arbitrary division that sum to the original, like 1300 ft and 200 ft. Modflow seems to sum these and solutions seem right - it just seems to be an annoying problem. Is there a fix for this?

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The BC gets split in an attempt to correctly compute the flow of water in/out of the aquifer associated with a specified head arc in the map module. The division is not as arbitrary as it seems; GMS looks at the length of each arc in the cell to determine what the different head values should be. So if the head in the cell should be 1500 and one arc has a length of 866 in the cell and another arc has a length of 133 in the cell then the head associated with the first arc will be 1300 and the head associated with the second arc will be 200.

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The BC gets split in an attempt to correctly compute the flow of water in/out of the aquifer associated with a specified head arc in the map module. The division is not as arbitrary as it seems; GMS looks at the length of each arc in the cell to determine what the different head values should be. So if the head in the cell should be 1500 and one arc has a length of 866 in the cell and another arc has a length of 133 in the cell then the head associated with the first arc will be 1300 and the head associated with the second arc will be 200.

I'm not sure I understand what you're saying - there's only one arc passing through the cells where this is happening. Also, it's only a few cells out of hundreds of variable head cells in the model where this happens.

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Zak - Is it possible that, while you were drawing the arc, you stopped it and started it again, but the arcs didn't actually connect? From a distance, it would look like one arc, but if you zoomed in, they wouldn't be connected. That's the only thing I can come up with as to why you would have 2 specified heads in one cell.

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QUOTE (Zak_B @ Sep 17 2008, 02:59 PM) <{POST_SNAPBACK}>
I'm not sure I understand what you're saying - there's only one arc passing through the cells where this is happening. Also, it's only a few cells out of hundreds of variable head cells in the model where this happens.

If there is only one arc passing through the cell then this sounds like a bug. If this is the case then you should send your files to support with the appropriate instructions.

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