Drawdown

In my current project I want to calculate the groundwater inflow into several wells inside a building excavation in accordance with a predefined hydraulic head at the wells using FEFLOW 7.1.
For example, the natural phreatic level is located at -10 m and for a construction site I have to lower the phreatic level to exact -20 m. What is the best way to do that?
Using 'multilayer wells' just makes the definition of a well capacity possible and I would have to find my solution iteratively.
Attached you will find my current model.
Thank you!

As you correctly pointed out, you have the possibility to represent the wells by means of fixed heads (Dirichlet). Use a maximum flow rate constraint with 0 m³/d to avoid any artificial infiltration. You may additionally impose a minimum flow rate constraint with an exfiltration rate corresponding to the pumping rate. The latter case enables you to avoid that more water is leaving the system as the pumping well is technically able to handle (pump capacity).