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ex-gwt-henry.py.
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Henry Problem
Classic saltwater intrusion
Initial setup
Import dependencies, define the example name and workspace, and read settings from environment variables.
[1]:
import os
import pathlib as pl
import flopy
import git
import matplotlib.pyplot as plt
from flopy.plot.styles import styles
from modflow_devtools.misc import get_env, timed
# Example name and workspace paths. If this example is running
# in the git repository, use the folder structure described in
# the README. Otherwise just use the current working directory.
try:
root = pl.Path(git.Repo(".", search_parent_directories=True).working_dir)
except:
root = None
workspace = root / "examples" if root else pl.Path.cwd()
figs_path = root / "figures" if root else pl.Path.cwd()
# Settings from environment variables
write = get_env("WRITE", True)
run = get_env("RUN", True)
plot = get_env("PLOT", True)
plot_show = get_env("PLOT_SHOW", True)
plot_save = get_env("PLOT_SAVE", True)
Define parameters
Define model units, parameters and other settings.
[2]:
# Scenario-specific parameters - make sure there is at least one blank line before next item
parameters = {
"ex-gwt-henry-a": {
"inflow": 5.7024,
},
"ex-gwt-henry-b": {
"inflow": 2.851,
},
}
# Scenario parameter units - make sure there is at least one blank line before next item
# add parameter_units to add units to the scenario parameter table
parameter_units = {
"inflow": "$m^3/d$",
}
# Model units
length_units = "centimeters"
time_units = "seconds"
# Model parameters
nper = 1 # Number of periods
nstp = 500 # Number of time steps
perlen = 0.5 # Simulation time length ($d$)
nlay = 40 # Number of layers
nrow = 1 # Number of rows
ncol = 80 # Number of columns
system_length = 2.0 # Length of system ($m$)
delr = 0.025 # Column width ($m$)
delc = 1.0 # Row width ($m$)
delv = 0.025 # Layer thickness
top = 1.0 # Top of the model ($m$)
hydraulic_conductivity = 864.0 # Hydraulic conductivity ($m d^{-1}$)
initial_concentration = 35.0 # Initial concentration (unitless)
porosity = 0.35 # porosity (unitless)
diffusion_coefficient = 0.57024 # diffusion coefficient ($m^2/d$)
botm = [top - k * delv for k in range(1, nlay + 1)]
nouter, ninner = 100, 300
hclose, rclose, relax = 1e-10, 1e-6, 0.97
Model setup
Define functions to build models, write input files, and run the simulation.
[3]:
def build_models(sim_folder, inflow):
print(f"Building model...{sim_folder}")
name = "flow"
sim_ws = os.path.join(workspace, sim_folder)
sim = flopy.mf6.MFSimulation(sim_name=name, sim_ws=sim_ws, exe_name="mf6")
tdis_ds = ((perlen, nstp, 1.0),)
flopy.mf6.ModflowTdis(sim, nper=nper, perioddata=tdis_ds, time_units=time_units)
gwf = flopy.mf6.ModflowGwf(sim, modelname=name, save_flows=True)
ims = flopy.mf6.ModflowIms(
sim,
print_option="ALL",
outer_dvclose=hclose,
outer_maximum=nouter,
under_relaxation="NONE",
inner_maximum=ninner,
inner_dvclose=hclose,
rcloserecord=rclose,
linear_acceleration="BICGSTAB",
scaling_method="NONE",
reordering_method="NONE",
relaxation_factor=relax,
filename=f"{gwf.name}.ims",
)
sim.register_ims_package(ims, [gwf.name])
flopy.mf6.ModflowGwfdis(
gwf,
length_units=length_units,
nlay=nlay,
nrow=nrow,
ncol=ncol,
delr=delr,
delc=delc,
top=top,
botm=botm,
)
flopy.mf6.ModflowGwfnpf(
gwf,
save_specific_discharge=True,
icelltype=0,
k=hydraulic_conductivity,
)
flopy.mf6.ModflowGwfic(gwf, strt=initial_concentration)
pd = [(0, 0.7, 0.0, "trans", "concentration")]
flopy.mf6.ModflowGwfbuy(gwf, packagedata=pd)
ghbcond = hydraulic_conductivity * delv * delc / (0.5 * delr)
ghbspd = [[(k, 0, ncol - 1), top, ghbcond, 35.0] for k in range(nlay)]
flopy.mf6.ModflowGwfghb(
gwf,
stress_period_data=ghbspd,
pname="GHB-1",
auxiliary="CONCENTRATION",
)
welspd = [[(k, 0, 0), inflow / nlay, 0.0] for k in range(nlay)]
flopy.mf6.ModflowGwfwel(
gwf,
stress_period_data=welspd,
pname="WEL-1",
auxiliary="CONCENTRATION",
)
head_filerecord = f"{name}.hds"
budget_filerecord = f"{name}.bud"
flopy.mf6.ModflowGwfoc(
gwf,
head_filerecord=head_filerecord,
budget_filerecord=budget_filerecord,
saverecord=[("HEAD", "ALL"), ("BUDGET", "ALL")],
)
gwt = flopy.mf6.ModflowGwt(sim, modelname="trans")
imsgwt = flopy.mf6.ModflowIms(
sim,
print_option="ALL",
outer_dvclose=hclose,
outer_maximum=nouter,
under_relaxation="NONE",
inner_maximum=ninner,
inner_dvclose=hclose,
rcloserecord=rclose,
linear_acceleration="BICGSTAB",
scaling_method="NONE",
reordering_method="NONE",
relaxation_factor=relax,
filename=f"{gwt.name}.ims",
)
sim.register_ims_package(imsgwt, [gwt.name])
flopy.mf6.ModflowGwtdis(
gwt,
length_units=length_units,
nlay=nlay,
nrow=nrow,
ncol=ncol,
delr=delr,
delc=delc,
top=top,
botm=botm,
)
flopy.mf6.ModflowGwtmst(gwt, porosity=porosity)
flopy.mf6.ModflowGwtic(gwt, strt=initial_concentration)
flopy.mf6.ModflowGwtadv(gwt, scheme="UPSTREAM")
flopy.mf6.ModflowGwtdsp(gwt, xt3d_off=True, diffc=diffusion_coefficient)
sourcerecarray = [
("GHB-1", "AUX", "CONCENTRATION"),
("WEL-1", "AUX", "CONCENTRATION"),
]
flopy.mf6.ModflowGwtssm(gwt, sources=sourcerecarray)
flopy.mf6.ModflowGwtoc(
gwt,
budget_filerecord=f"{gwt.name}.cbc",
concentration_filerecord=f"{gwt.name}.ucn",
concentrationprintrecord=[("COLUMNS", 10, "WIDTH", 15, "DIGITS", 6, "GENERAL")],
saverecord=[("CONCENTRATION", "ALL")],
printrecord=[("CONCENTRATION", "LAST"), ("BUDGET", "LAST")],
)
flopy.mf6.ModflowGwfgwt(
sim, exgtype="GWF6-GWT6", exgmnamea=gwf.name, exgmnameb=gwt.name
)
return sim
def write_models(sim, silent=True):
sim.write_simulation(silent=silent)
@timed
def run_models(sim, silent=True):
success, buff = sim.run_simulation(silent=silent)
assert success, buff
Plotting results
Define functions to plot model results.
[4]:
# Figure properties
figure_size = (6, 4)
def plot_conc(sim, idx):
with styles.USGSMap():
sim_name = list(parameters.keys())[idx]
gwf = sim.get_model("flow")
gwt = sim.get_model("trans")
fig = plt.figure(figsize=figure_size)
fig.tight_layout()
# get MODFLOW 6 concentration
conc = gwt.output.concentration().get_data()
ax = fig.add_subplot(1, 1, 1, aspect="equal")
pxs = flopy.plot.PlotCrossSection(model=gwf, ax=ax, line={"row": 0})
pxs.plot_array(conc, cmap="jet")
levels = [35 * f for f in [0.01, 0.1, 0.5, 0.9, 0.99]]
cs = pxs.contour_array(
conc, levels=levels, colors="w", linewidths=1.0, linestyles="-"
)
ax.set_xlabel("x position (m)")
ax.set_ylabel("z position (m)")
plt.clabel(cs, fmt="%4.2f", fontsize=5)
if plot_show:
plt.show()
if plot_save:
fpth = figs_path / f"{sim_name}-conc.png"
fig.savefig(fpth)
def plot_results(sim, idx):
plot_conc(sim, idx)
Running the example
Define and invoke a function to run the example scenario, then plot results.
[5]:
def scenario(idx, silent=True):
key = list(parameters.keys())[idx]
parameter_dict = parameters[key]
sim = build_models(key, **parameter_dict)
if write:
write_models(sim, silent=silent)
if run:
run_models(sim, silent=silent)
if plot:
plot_results(sim, idx)
# Scenario 1 - Classic henry problem
scenario(0)
# Scenario 2 - Modified Henry problem with half the inflow rate
scenario(1)
Building model...ex-gwt-henry-a
run_models took 6652.95 ms
Building model...ex-gwt-henry-b
run_models took 6825.12 ms
