Posted Sat, 23 Jul 2022 20:55:43 GMT by Joshua Shultz Graduate Student
I am building a steady state  regional groundwater table in FEFLOWs variably saturated mode. The model is generally flat elevation to groundwater is less than 10m. However i noticed that even with a clayey soil and higher than normal recharge ( i am using the in/outflow on top/bottom) the model will become bone dry above the water table. I have used the standard and modified van Genuchten parameters for unsaturated flow. My main question is why do I not see a gradient change in moisture content but rather a fast change from dry to saturated? Is this expected of FEFLOW as it is applying my "recharge" directly to the water surface? I specify the top layer (land surface elevation) of my model? Any insight would be appreciated - Thanks
Posted Tue, 09 Aug 2022 07:20:12 GMT by Carlos Andres Rivera Villarreyes Global Product Specialist - FEFLOW
There are several reasons of your observation, being the most simple one the discretization. If you would like to improve the vertical moisture profile in the unsaturated zone, you basically need to work with more slices.
Also, FEFLOW does not apply directly the recharge to the water table. The fact that you are solving the Richards eq., FEFLOW is capable to simulate the propagation of the wetting front (let's say from top surface) down to the water table. If you are getting less recharge, then it may be you need to improve parameter settings (conductivity, unsaturated param. etc).

Posted Tue, 09 Aug 2022 18:17:06 GMT by Joshua Shultz Graduate Student
Thanks for your reply, I had some further questions and I believe I sent you an email with more details

Joshua Shultz

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