bug: Reading flows from binary budget file for steady stress period of zero length

[mbakker7]

I have a MF6 model consisting of two stress periods. First stress period is steady with length 0. Second stress period is transient. I can read the heads from the binary heads file with Flopy. But when I read the flow from the binary budget file, I can not read the budget for the steady stress period. The times function also doesn't return the first time. But I can read the budget data by specifying the step and period, so it is all stored. It all works fine when the steady stress period has length rather than 0. But it is nice to specify a transient stress period that starts at 0 (i.e., the first stress period has zero length).

import numpy as np
import flopy as fp 

modelname = 'bugtest'
modelws = './bugtest'
sim = fp.mf6.MFSimulation(sim_name='bugtest', 
                          version='mf6', 
                          exe_name='../bin/mf6', 
                          sim_ws=modelws, 
                         )

tdis = fp.mf6.ModflowTdis(simulation=sim, 
                          nper=2, 
                          perioddata=[(0, 1, 1), (10, 10, 1)], 
                         )

ims = fp.mf6.ModflowIms(simulation=sim, 
                        complexity='SIMPLE',
                       )

gwf = fp.mf6.ModflowGwf(simulation=sim, 
                        modelname=modelname, 
                        save_flows=True,
                       )

dis = fp.mf6.ModflowGwfdis(model=gwf, 
                           nlay=1, nrow=1, ncol=10, delr=1, delc=10, top=10, botm=0
                          ) 

npf = fp.mf6.ModflowGwfnpf(model=gwf, 
                           icelltype=[0], 
                           k=10,
                          )

ic = fp.mf6.ModflowGwfic(model=gwf, 
                         strt=0,
                        )

wel = fp.mf6.ModflowGwfwel(model=gwf, 
                           stress_period_data={0: 0, 1: [[(0, 0, 0), -1]]},
                          )

sto = fp.mf6.ModflowGwfsto(model=gwf, 
                           ss=1e-4,
                           steady_state={0: True},
                           transient={1: True},
                          )

chd = fp.mf6.ModflowGwfchd(model=gwf, 
                           stress_period_data={0: [[(0, 0, 9), 0]]},
                          )

oc = fp.mf6.ModflowGwfoc(model=gwf, 
                         budget_filerecord=f"{modelname}.cbc", 
                         head_filerecord=f"{modelname}.hds", 
                         saverecord=[("HEAD", "ALL"), ("BUDGET", "ALL")],
                        )
sim.write_simulation(silent=True)
success, _ = sim.run_simulation(silent=True) 
print('success: ', success)

hds = gwf.output.head()
cbb = gwf.output.budget()

Then the output is:

print(hds.get_times()) # gives correct times
print(hds.get_kstpkper()) # gives correct steps and periods
print(cbb.get_times()) # skips the first time
print(cbb.get_kstpkper()) # gives correct steps and periods
print(cbb.get_data(totim=0)) # gives empty list, which is wrong
print(cbb.get_data(kstpkper=(0, 0))) # returns correct values for step=0, period=0