Observation heads are not changing

[DT21CIV011 RAKESH K. VERMA]

I am running a 3-layered ModFlow6 model in Model Muse, I have recharge and GHB conditions, and using PEST for model calibration. I assigned three hydrological conductivity zones, but after making many attempts by changing k, storage constant, seepage data, I see negligible changes, even though I have raised the hydrological conductivity several times. The output groundwater head (about 89m) always remained below the bottom of the last aquifer (z=150m). Anybody suggest what could be the reason?

[Robert Lanning]

You may be losing too much water out of the model from your lowest layer.  Experiment by (1) significantly decreasing the K in your bottom layer and/or (2) adjust your GHB on one or more of the sides of your model.

Take care,

Geobob