turning off mf6 stress package with auxiliary variable not working

[dbrakenhoff]

Not sure if this is an issue or if I might be missing something, but I'm having trouble turning off a stress package (GHB in this case).

The mf6 input/output manual states:

To turnoff all of the stresses for a stress period, a PERIOD block must be specified with no entries.

I tried doing that with flopy, but the following code creates a GHB package with a None entry in the period block for Period 6. This causes an error when MF6 encounters that None entry. My model is actually a variable density model with salinity, hence the concentration variable.

import flopy

sim = flopy.mf6.MFSimulation(exe_name="mf6")

nper = 10
pd = [(1, 1, 1)] * nper

tdis = flopy.mf6.ModflowTdis(sim, nper=nper, perioddata=pd)
ims = flopy.mf6.ModflowIms(sim)
gwf = flopy.mf6.ModflowGwf(sim)
dis = flopy.mf6.ModflowGwfdis(gwf)
npf = flopy.mf6.ModflowGwfnpf(gwf)
ic = flopy.mf6.ModflowGwfic(gwf)

spd = {
    0: [[(0, 1, 1), 1.0, 100.0, 0.0],
        [(0, 0, 0), 1.0, 100.0, 0.0]],
    5: [()]
}

ghb = flopy.mf6.ModflowGwfghb(gwf, stress_period_data=spd,
                              auxiliary=["CONCENTRATION"])

sim.write_simulation()
sim.run_simulation()

I've been able to establish that this does not happen when the auxiliary variable is not added. In that case the period block for stress period 6 is empty.

I also tried entering an empty rec-array, but that still yields a period block with a "None" entry:

empty = flopy.mf6.ModflowGwfghb.stress_period_data.empty(
    gwf, aux_vars=["CONCENTRATION"])[0]
spd2 = {
    0: [[(0, 1, 1), 1.0, 100.0, 0.0],
        [(0, 0, 0), 1.0, 100.0, 0.0]],
    5: empty
}

Thanks in advance for taking a look!

[spaulins-usgs]

@dbrakenhoff Confirm that this is a problem. I have a fix though I am going to run a few more tests to verify that it fixes all cases before I submit a PR tomorrow morning. If you want the fix now it is in the mfdatalist.py file on my fork here:

https://github.com/scottrp/flopy