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Creating elevation on Modflow


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Hi all, I am currently looking at the impact of elevation on the hydraulic heads in a three layer model in Modflow 6 for elevations of 1, 5 and 10 degrees. To create elevation I am manually entering values within the top and bottom elevation packages. However when running the model the cells seem to flood substantially. I have investigated the effect of recharge and hydraulic conductivity however, despite using a wide range of values for these parameters the cells in the top layer still flood substantially. I wanted to check if the problem was related to how I constructed the model and input the elevation. Are there other methods of defining elevation within Modflow6? 

I have attached below images of the conceptual for flat and sloping scenario for reference. Any assistance would be greatly appreciated. 

Many thanks,


Conceptual models.pptx

Edited by MGage
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Well, based on what I'm seeing, you have one side of your model that has a constant head boundary condition and the other 3 are No flow boundaries.  If this is the case, the only way for the water (which you are adding through recharge) to leave the model is through the constant head boundary.  Therefore, the groundwater elevation has to get high enough for the gradient to want to flow towards the constant head.  At a minimum, it will need to be at the elevation of the constant head boundary.  If the conductivity of the peat layer is too low, this will create quite a mound. I'm thinking that you may not want a No Flow boundary in all locations, but I don't know everything about your model.

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