Posted Fri, 27 Mar 2015 07:04:16 GMT by Thomas Chung Senior Hydrogeologist
I am working a confined aquifer model with artesian wells.  I wonder what is the best type of boundary conditions to represent an artesian wells in Feflow. I have tried to use the type 1 - hydraulic head BC to have minimum flow constraints to bound the maximum flow from the artesian wells (plus maximum flow constraints = 0 not to inject water) and I have the BC = topographic elevations. However, it seems the BC level controls most of the model output and sometimes I got outflow higher than what I constraint the artesian wells.

I have also tried to use the well BC, however, if I put the minimum head constraints above my aquifer layer (say top of layer 2, I got the minimum
head constraint/ intake level as layer 1 top), then I have some wells injecting in the model.

It would be great if anyone can share their modeling experience with artesian wells here. 

Posted Mon, 30 Mar 2015 13:22:10 GMT by Carlos Andres Rivera Villarreyes Global Product Specialist - FEFLOW
Hi Thomas,

It is not correct that you set a head BC equal to the topographic level, this would reflect the behavior of a seepage boundary. For an artesian well, the head BC should get a value, which depends on the high pressure located down in the aquifer. I would recommend you the following options:
Head BC -> Pressurized value
Minimum flow-rate constraint = Maximum flow expected through the artesian well in m3/d
Maximum flow-rate constraint = 0 m3/d (avoid possible water inflow).

Depending on the local settings, you may use a discrete feature element (DFE), which can enhance the vertical flow. Thus, the outflow would be mainly dominated by the deeper aquifer and not the shallow locations. Phreatic and piezometric surfaces may be complicated, so the most-correct evaluation can be only reached by using the Richards' approach in FEFLOW.


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