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MODFLOW 6: Time Array Series Packages

Introduction to Time Array Series

Time array series can be set for any package through the package.tas object, and each package.tas object has several attributes that can be set:

Attribute	Type	Description
package.tas.filename	str	Name of time series file to create. The default is packagename + “.tas”.
package.tas.tas_array	{double:[double]}	Array containing the time array series information for specific times.
package.tas.time_series_namerecord	str	Name by which a package references a particular time-array series. The name must be unique among all time-array series used in a package.
package.tas.interpolation_methodrecord	list (of strings)	List of interpolation methods to use for time array series. Method must be either “stepwise” or “linear”.
package.tas.sfacrecord_single	float	Scale factor to multiply the time array series data column. Can only be used if there is one time series data column.

The following code sets up a simulation used in the time array series examples.

# package import
from tempfile import TemporaryDirectory

import numpy as np

import flopy

# set up where simulation workspace will be stored
temp_dir = TemporaryDirectory()
workspace = temp_dir.name
name = "tutorial04_mf6_data"

# create the Flopy simulation and tdis objects
sim = flopy.mf6.MFSimulation(
    sim_name=name, exe_name="mf6", version="mf6", sim_ws=workspace
)
tdis_rc = [(1.0, 1, 1.0), (10.0, 5, 1.0), (10.0, 5, 1.0), (10.0, 1, 1.0)]
tdis_package = flopy.mf6.modflow.mftdis.ModflowTdis(
    sim, time_units="DAYS", nper=4, perioddata=tdis_rc
)
# create the Flopy groundwater flow (gwf) model object
model_nam_file = f"{name}.nam"
gwf = flopy.mf6.ModflowGwf(sim, modelname=name, model_nam_file=model_nam_file)
# create the flopy iterative model solver (ims) package object
ims = flopy.mf6.modflow.mfims.ModflowIms(sim, pname="ims", complexity="SIMPLE")
# create the discretization package
bot = np.linspace(-3.0, -50.0 / 3.0, 3)
delrow = delcol = 4.0
dis = flopy.mf6.modflow.mfgwfdis.ModflowGwfdis(
    gwf,
    pname="dis",
    nogrb=True,
    nlay=3,
    nrow=101,
    ncol=101,
    delr=delrow,
    delc=delcol,
    top=0.0,
    botm=bot,
)
# create the initial condition (ic) and node property flow (npf) packages
ic_package = flopy.mf6.modflow.mfgwfic.ModflowGwfic(gwf, strt=50.0)
npf_package = flopy.mf6.modflow.mfgwfnpf.ModflowGwfnpf(
    gwf,
    save_flows=True,
    icelltype=[1, 0, 0],
    k=[5.0, 0.1, 4.0],
    k33=[0.5, 0.005, 0.1],
)

Time Array Series Example 1

Time array series data can be passed into the timearrayseries parameter on construction of any package that supports time array series. This example uses the timearrayseries parameter to create a time array series and then uses the package’s tas property to finish the time array series setup.

This example uses time array series data in a RCHA package. The time array series is built as a dictionary with the times as the keys and the recharge values as the values.

tas = {0.0: 0.000002, 200.0: 0.0000001}

The time array series data is then passed into the timearrayseries parameter when the RCHA package is constructed.

rcha = flopy.mf6.modflow.mfgwfrcha.ModflowGwfrcha(
    gwf, timearrayseries=tas, recharge="TIMEARRAYSERIES rcharray_1"
)

WARNING: Time array series name rcharray_1 not found in any time series file

Time array series attributes can be set by access the time array series package object through the rcha.tas attribute.

# finish defining the time array series properties
rcha.tas.time_series_namerecord = "rcharray_1"
rcha.tas.interpolation_methodrecord = "LINEAR"

The simulation is then written to files and run.

sim.write_simulation()
sim.run_simulation()

writing simulation...
  writing simulation name file...
  writing simulation tdis package...
  writing solution package ims...
  writing model tutorial04_mf6_data...
    writing model name file...
    writing package dis...
    writing package ic...
    writing package npf...
    writing package rcha_0...
    writing package tas_0...
FloPy is using the following executable to run the model: ../../home/runner/.local/bin/modflow/mf6
                                   MODFLOW 6
                U.S. GEOLOGICAL SURVEY MODULAR HYDROLOGIC MODEL
                  VERSION 6.7.0.dev0 (preliminary) 01/09/2025
                               ***DEVELOP MODE***

   MODFLOW 6 compiled Jan 09 2025 13:31:07 with Intel(R) Fortran Intel(R) 64
   Compiler Classic for applications running on Intel(R) 64, Version 2021.7.0
                             Build 20220726_000000

This software is preliminary or provisional and is subject to
revision. It is being provided to meet the need for timely best
science. The software has not received final approval by the U.S.
Geological Survey (USGS). No warranty, expressed or implied, is made
by the USGS or the U.S. Government as to the functionality of the
software and related material nor shall the fact of release
constitute any such warranty. The software is provided on the
condition that neither the USGS nor the U.S. Government shall be held
liable for any damages resulting from the authorized or unauthorized
use of the software.


 MODFLOW runs in SEQUENTIAL mode

 Run start date and time (yyyy/mm/dd hh:mm:ss): 2025/01/10 23:25:23

 Writing simulation list file: mfsim.lst
 Using Simulation name file: mfsim.nam


ERROR REPORT:

  1. Input name "TUTORIAL04_MF6_DATA" exceeds maximum allowed length (16) for
     MODELNAME.

UNIT ERROR REPORT:

  1. ERROR OCCURRED WHILE READING FILE 'mfsim.nam'

(False, [])

# clean up for next example
gwf.remove_package("rcha")

Time Array Series Example 2

A time array series can be added after a package is created by calling the package’s tas attribute’s initialize method. Initialize allows you to define all time array series attributes including file name, the time array series data, name record, and method record.

First a recharge package is built.

# create recharge package with recharge pointing to a time array series
# not yet defined. FloPy will generate a warning that there is not yet a
# time series name record for recharray_1
rcha = flopy.mf6.modflow.mfgwfrcha.ModflowGwfrcha(
    gwf, recharge="TIMEARRAYSERIES rcharray_1"
)

WARNING: Time array series name rcharray_1 not found in any time series file

Then a time array series dictionary is created as done in example 1.

tas = {0.0: 0.000002, 200.0: 0.0000001}

The time array series data are added by calling the initialize method from the ‘RCHA’ package’s tas attribute. The time array series file name, name record, and method record, along with the time series data are set in the initialize method.

# initialize the time array series
rcha.tas.initialize(
    filename="method2.tas",
    tas_array=tas,
    time_series_namerecord="rcharray_1",
    interpolation_methodrecord="LINEAR",
)

try:
    temp_dir.cleanup()
except PermissionError:
    # can occur on windows: https://docs.python.org/3/library/tempfile.html#tempfile.TemporaryDirectory
    pass