Modflow transient simulation - no convergence

[GMS User]

I buiil a steady state model. I run it and I get it to converge.

I switch to transient, change the CHD boundary conditions and import heads from the steady state simulation.

I run the model and everything is fine.

When I try to change the boundary conditions (CHD) I get the model not to converge. In the iteration/error I get two very high values and then the simulation stops.

I revert to previous values but the simulations fails again.

The only way to get it fixed is to un-check all packages in modflow and re-map the coverages to modflow.

After that the simulations converges.

By the way I'm using GMS 8.0.

Any other suggestions?

Thanks

[Alan Lemon]

It sounds like when you "remap to MODFLOW" that the CHD bcs are changed back to the original state and so now it converges?

Which solver are you using?

Do a bunch of cells go dry in the transient simulation? Maybe modflow gets some divide by 0 or something.