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Drain Elevation Problem


Hydrology
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I have a drain in my model with a specified elevation. When I have used drains previously, the groundwater is drawn down to the specified elevation for those cells that the drain is in. In the model that I am now working on, the groundwater is not being drawn down to the drain elevation, it is 8 to 10 feet higher, and varies across the drain. How can I force the groundwater to be drawn down to the elevation specified by the drain, and is the response that I am seeing correct?

I am using GMS 8.2 64bit in Windows 7.

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How big is the conductance compared with the cell size? If the cells are really large then you may need a really large drain conductance if you are simulating a free draining face. The numbers that you have mentioned are quite large but you are getting some response when you increase the value.

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The cell size for layer 1, where the drains are, is about 4'x4' and 95' deep. The drain is set to 40' deep. I am using the drain as an easier way to simulate a well. The problem may be the cell depth. In other models I usually have not had a single layer that is this deep.

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What is the specified drain elevation compared to the head in the model cell?

The flow out will be calculated as follows:

Q = COND * (DELEV - Hijk) where COND is the drain conductance, Hijk is the head in the cell, and DELEV is the drain elevation.

If you select the cell and go the the MODFLOW | Flow Budget command you should see the calculated flow to the drain.

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