Problem with Well BC (rate budget)

Hi,

I build a 3D aquifer with 4 layers in transient conditions. In this model, there are 5 well BC.

For all well BC, I define 0 m3/d on the first slice, and the pumping rate on the second slice.

The problem is my rate budget is not constant for wells, even after a long time of computation. Sometimes, wells seems to stop pumping. And a moment after, the well seems to pump again. This probelm lead to an oscillation of the balance.

I think this problem can be caused by a bad definition of the boundary condition but I can't find where I made a mistake.

Is there anyone to know how to face this problem and how to fix the constant rate of the pumping rate?

I thank you in advance.

Best regards,

Guillaume

What is your free surface settings? If "fully confined", the well should be able to pump at a constant rate, however if using "unconfined" settings, the well BC can go "dry" and stop pumping. It would be expected to oscillate as the BC turns on/off due to over pumping and recovery.

Thank you for your answer,

I am using unconfined settings. It's exactly what happens : sometimes the well BC become dry and stop pumping.

I will try to modify aquifer settings to allow a higher rate before the well become dry.