Unsaturated simulation

Hello
I have to run a 3D regional, unsaturated flow model,
The model seems to run in the begining but after one day , it take very small time steps and require an enorm disk space!!!
I note that I have assigned powerfunctions of rivers in my model from 1 day to  397 days.
When I have run, feflow calculates 50 days in 15 hours (enorm time of simulation) knowing that the final time is 397 days!!!!
Can you please tell me how to do to run it correctly,
I have take default settings as said in the help to guarantee a stable simulation run.
Thank you very much for any help.

Have you assigned any head constraints at your boundary nodes ?

In my experience, when a head boundary condition is lower than the min head constraint or higher than a max head constraint, the boundary become instable.
maybe this helps.

best regards henilein

Hello henilein,
I don't assigned any head constraint in my model,
thx