MODPATH with MODFLOW-NWT

[Saman-M-B]

Hello,

I'm having this issue that for my transient modflow-nwt model, I wish to run backward particle tracking using modpath7. However, despite flopy examples in this matter, when I run modpath, it doesn't go into the transient phase, and in the first stress period, which is steady-state, particles terminate. I tried different options, methods, and configurations, even with MODPATH6, but no progress.

The thing is that I have two different well galleries in my aquifer which one of which only gets activated at a certain stress period onwards, so I need the modpath to simulate the transient phase to see the effect of the second well gallery on the flow dynamics.

modelname = mod_Transient'
mf = flopy.modflow.Modflow.load(
f=modelname,
model_ws=ws,
verbose=False,
version="mfnwt",
check=False,
)

cellids_wel = mf.wel.stress_period_data[0]
nodew = get_nodes_wel(cellids_wel, nrow, ncol)
cellids_mnw2 = mf.mnw2.node_data
nodemnw = get_nodes_mnw2(cellids_mnw2, nrow, ncol)
all_nodes = nodew + nodemnw

particles = 1

sd = flopy.modpath.CellDataType(
drape=0,
columncelldivisions=particles,
rowcelldivisions=particles,
layercelldivisions=particles,
)

pd_well = flopy.modpath.NodeParticleData(
subdivisiondata=[sd],
nodes=nodew,
)
pd_mnw = flopy.modpath.NodeParticleData(
subdivisiondata=[sd],
nodes=nodemnw,
)

pg_wel = flopy.modpath.ParticleGroupNodeTemplate(
particlegroupname="PG_WEL", particledata=pd_well, filename=f"{modelname}.pg2.sloc"
)
pg_mnw = flopy.modpath.ParticleGroupNodeTemplate(
particlegroupname="PG_MNW", particledata=pd_mnw, filename=f"{modelname}.pg3.sloc"
)

pgs = [pg_wel, pg_mnw]

mpnamb = f"{modelname}_mp7_backward"

mp = flopy.modpath.Modpath7(
modelname=mpnamb,
flowmodel=mf,
exe_name="mp7",
model_ws=ws,
)
mpbas = flopy.modpath.Modpath7Bas(mp)
mpsim = flopy.modpath.Modpath7Sim(
mp,
simulationtype="pathline",
trackingdirection="backward",
weaksinkoption="pass_through",
weaksourceoption="pass_through",
budgetoutputoption="summary",
#referencetime=[107, 0, 1.0], #3256.0
#timepointdata=[100, 30.0],
#zonedataoption="on",
particlegroups=pgs,
stoptimeoption="extend", # extend, total, or specified
#stoptime=0.0,
#retardationfactoroption="off",
#retardation=0.5,
)

mp.write_input()
success, buff = mp.run_model(silent=False, report=True)

Run particle tracking simulation ...
Processing Time Step 1 Period 1. Time = 1.00000E+04 Steady-state flow

Particle Summary:
0 particles are pending release.
0 particles remain active.
0 particles terminated at boundary faces.
0 particles terminated at weak sink cells.
0 particles terminated at weak source cells.
484 particles terminated at strong source/sink cells.
0 particles terminated in cells with a specified zone number.
0 particles were stranded in inactive or dry cells.
0 particles were unreleased.
0 particles have an unknown status.

Normal termination.

I even tried to see what if i put the erefence time of simulation in backward option to the last stress period which is steady-state too but as you can see below, no use.

Run particle tracking simulation ...
Processing Time Step 1 Period 108. Time = 2.32250E+04 Steady-state flow
Processing Time Step 30 Period 107. Time = 1.32250E+04 Steady-state flow
Processing Time Step 29 Period 107. Time = 1.32240E+04 Steady-state flow

Particle Summary:
0 particles are pending release.
0 particles remain active.
0 particles terminated at boundary faces.
0 particles terminated at weak sink cells.
0 particles terminated at weak source cells.
484 particles terminated at strong source/sink cells.
0 particles terminated in cells with a specified zone number.
0 particles were stranded in inactive or dry cells.
0 particles were unreleased.
0 particles have an unknown status.

Normal termination.

[wpbonelli]

Nothing leaps out to me from your modpath setup code. Could you share your NWT model as well so we can have a closer look?

[Saman-M-B]

Yes, sure.

mod_Transient