minus head-bottom diference of whole section

Hi,

I am using FEFLOW 4.8 to model an one layer free surface fluvial delta ground water system in a closed basin.  I met a confusing situation that the modeled head-bottom difference was minus for every point along some sections while the water in/out balance was maintained. Would you please tell me what’s the possible reason. Thanks.

Shaofeng

Heads can be below the model bottom if in Specific Options settings 'Falling dry at bottom' is set to 'unconstrained'. FEFLOW uses a minimum transmissivity to calculate flow in these areas then.