I think this is the problem that I too had a while back - I think it is because
your layer boundaries are not horizontal (no problem with that) and the river in
some places is in contact with one layer and other places it is in contact with
the next layer.

I think if you double click on the river arc and instead of <use layer range>
choose <auto assign layers using lower cells> this will assign the river arc to
the appropriate cells in the topmost layer that it crosses at all the points
along the arc.

---- Original message ----
>Date: Mon, 07 Apr 2008 15:04:31 -0000
>From: "geo_mithun" <geo_mithun@...>
>Subject: [gms-users] Need help
>To: gms-users@...
>
> Dear People
> I'm really confused. I really need your help.
> Constantly getting this
> error message when I do the modflow simulation check
> using GMS 6.0
> "The Changing Head Boundary Condition is below the
> bottom elevation of
> cell"
>
> Now what I'm trying to do:
> > build a solid model using lithologs
> > made a 3D grids and new modflow model
> > then interpolated the solid solids to modflow
> model (grid overlay)
> > specified the head boundary conditions (river) and
> recharge rates
> using coverage to modflow comand
> > interpolate the top surface elevation.
>
> After that when I check simulation: it gives me
> above error. not sure
> what is happening.
>
> Any help would be appreciated.
>
> Thanks, Zahid
>
>