flopy.modflow.mflak module

mflak module. Contains the ModflowLak class. Note that the user can access the ModflowLak class as flopy.modflow.ModflowLak.

Additional information for this MODFLOW package can be found at the Online MODFLOW Guide.

class ModflowLak(model, nlakes=1, ipakcb=None, theta=-1.0, nssitr=0, sscncr=0.0, surfdep=0.0, stages=1.0, stage_range=None, tab_files=None, tab_units=None, lakarr=None, bdlknc=None, sill_data=None, flux_data=None, extension='lak', unitnumber=None, filenames=None, options=None, lwrt=0, **kwargs)[source]

Bases: flopy.pakbase.Package

MODFLOW Lake Package Class.

Parameters:
  • model (model object) – The model object (of type flopy.modflow.mf.Modflow) to which this package will be added.
  • nlakes (int) – NLAKES Number of separate lakes. Sublakes of multiple-lake systems are considered separate lakes for input purposes. The variable NLAKES is used, with certain internal assumptions and approximations, to dimension arrays for the simulation.
  • ipakcb (int) – (ILKCB in MODFLOW documentation) Whether or not to write cell-by-cell flows (yes if ILKCB> 0, no otherwise). If ILKCB< 0 and “Save Budget” is specified in the Output Control or ICBCFL is not equal to 0, the cell-by-cell flows will be printed in the standard output file. ICBCFL is specified in the input to the Output Control Option of MODFLOW.
  • lwrt (int or list of ints (one per SP)) – lwrt > 0, suppresses printout from the lake package. Default is 0 (to print budget information)
  • theta (float) –

    Explicit (THETA = 0.0), semi-implicit (0.0 < THETA < 1.0), or implicit (THETA = 1.0) solution for lake stages. SURFDEPTH is read only if THETA is assigned a negative value (the negative value of THETA is then changed to a positive value internally by the code). * A new method of solving for lake stage uses only the time-weighting

    factor THETA (Merritt and Konikow, 2000, p. 52) for transient simulations. THETA is automatically set to a value of 1.0 for all steady-state stress periods. For transient stress periods, Explicit (THETA = 0.0), semi-implicit (0.0 < THETA < 1.0), or implicit (THETA = 1.0) solutions can be used to calculate lake stages. The option to specify negative values for THETA is supported to allow specification of additional variables (NSSITER, SSCNCR, SURFDEP) for simulations that only include transient stress periods. If THETA is specified as a negative value, then it is converted to a positive value for calculations of lake stage.
    • In MODFLOW-2000 and later, ISS is not part of the input. Instead NSSITR or SSCNCR should be included if one or more stress periods is a steady state stress period as defined in Ss/tr in the Discretization file.
    • SSCNCR and NSSITR can be read for a transient only simulation by placing a negative sign immediately in front of THETA. A negative THETA sets a flag which assumes input values for NSSITR and SSCNCR will follow THETA in the format as described by Merritt and Konikow (p. 52). A negative THETA is automatically reset to a positive value after values of NSSITR and SSCNCR are read.
  • nssitr (int) –

    Maximum number of iterations for Newton’s method of solution for equilibrium lake stages in each MODFLOW iteration for steady-state aquifer head solution. Only read if ISS (option flag input to DIS Package of MODFLOW indicating steady-state solution) is not zero or if THETA is specified as a negative value. * NSSITR and SSCNCR may be omitted for transient solutions (ISS = 0). * In MODFLOW-2000 and later, ISS is not part of the input.

    Instead NSSITR or SSCNCR should be included if one or more stress periods is a steady state stress period as defined in Ss/tr in the Discretization file.
    • SSCNCR and NSSITR can be read for a transient only simulation by placing a negative sign immediately in front of THETA. A negative THETA sets a flag which assumes input values for NSSITR and SSCNCR will follow THETA in the format as described by Merritt and Konikow (p. 52). A negative THETA is automatically reset to a positive value after values of NSSITR and SSCNCR are read.
    • If NSSITR = 0, a value of 100 will be used instead.
  • sscncr (float) – Convergence criterion for equilibrium lake stage solution by Newton’s method. Only read if ISS is not zero or if THETA is specified as a negative value. See notes above for nssitr.
  • surfdepth (float) – The height of small topological variations (undulations) in lake-bottom elevations that can affect groundwater discharge to lakes. SURFDEPTH decreases the lakebed conductance for vertical flow across a horizontal lakebed caused both by a groundwater head that is between the lakebed and the lakebed plus SURFDEPTH and a lake stage that is also between the lakebed and the lakebed plus SURFDEPTH. This method provides a smooth transition from a condition of no groundwater discharge to a lake, when groundwater head is below the lakebed, to a condition of increasing groundwater discharge to a lake as groundwater head becomes greater than the elevation of the dry lakebed. The method also allows for the transition of seepage from a lake to groundwater when the lake stage decreases to the lakebed elevation. Values of SURFDEPTH ranging from 0.01 to 0.5 have been used successfully in test simulations. SURFDEP is read only if THETA is specified as a negative value.
  • stages (float or list of floats) – The initial stage of each lake at the beginning of the run.
  • stage_range (list of tuples (ssmn, ssmx) of length nlakes) –

    Where ssmn and ssmx are the minimum and maximum stages allowed for each lake in steady-state solution. * SSMN and SSMX are not needed for a transient run and must be

    omitted when the solution is transient.
    • When the first stress period is a steady-state stress period, SSMN is defined in record 3.

    For subsequent steady-state stress periods, SSMN is defined in record 9a.

  • lakarr (array of integers (nlay, nrow, ncol)) –

    LKARR A value is read in for every grid cell. If LKARR(I,J,K) = 0, the grid cell is not a lake volume cell. If LKARR(I,J,K) > 0, its value is the identification number of the lake occupying the grid cell. LKARR(I,J,K) must not exceed the value NLAKES. If it does, or if LKARR(I,J,K) < 0, LKARR(I,J,K) is set to zero. Lake cells cannot be overlain by non-lake cells in a higher layer. Lake cells must be inactive cells (IBOUND = 0) and should not be convertible to active cells (WETDRY = 0).

    The Lake package can be used when all or some of the model layers containing the lake are confined. The authors recommend using the Layer-Property Flow Package (LPF) for this case, although the BCF and HUF Packages will work too. However, when using the BCF6 package to define aquifer properties, lake/aquifer conductances in the lateral direction are based solely on the lakebed leakance (and not on the lateral transmissivity of the aquifer layer). As before, when the BCF6 package is used, vertical lake/aquifer conductances are based on lakebed conductance and on the vertical hydraulic conductivity of the aquifer layer underlying the lake when the wet/dry option is implemented, and only on the lakebed leakance when the wet/dry option is not implemented.

  • bdlknc (array of floats (nlay, nrow, ncol)) –

    BDLKNC A value is read in for every grid cell. The value is the lakebed leakance that will be assigned to lake/aquifer interfaces that occur in the corresponding grid cell. If the wet-dry option flag (IWDFLG) is not active (cells cannot rewet if they become dry), then the BDLKNC values are assumed to represent the combined leakances of the lakebed material and the aquifer material between the lake and the centers of the underlying grid cells, i. e., the vertical conductance values (CV) will not be used in the computation of conductances across lake/aquifer boundary faces in the vertical direction.

    IBOUND and WETDRY should be set to zero for every cell for which LKARR is not equal to zero. IBOUND is defined in the input to the Basic Package of MODFLOW. WETDRY is defined in the input to the BCF or other flow package of MODFLOW if the IWDFLG option is active. When used with the HUF package, the Lake Package has been modified to compute effective lake-aquifer conductance solely on the basis of the user-specified value of lakebed leakance; aquifer hydraulic conductivities are not used in this calculation. An appropriate informational message is now printed after the lakebed conductances are written to the main output file.

  • sill_data (dict) –

    (dataset 8 in documentation) Dict of lists keyed by stress period. Each list has a tuple of dataset 8a, 8b for every multi-lake system, where dataset 8a is another tuple of

    IC : int
    The number of sublakes
    ISUB : list of ints
    The identification numbers of the sublakes in the sublake system being described in this record. The center lake number is listed first.
    And dataset 8b contains
    SILLVT : sequence of floats
    A sequence of sill elevations for each sublakes that determines whether the center lake is connected with a given sublake. Values are entered for each sublake in the order the sublakes are listed in the previous record.
  • flux_data (dict) –

    (dataset 9 in documentation) Dict of lists keyed by stress period. The list for each stress period is a list of lists, with each list containing the variables PRCPLK EVAPLK RNF WTHDRW [SSMN] [SSMX] from the documentation.

    PRCPLK : float
    The rate of precipitation per unit area at the surface of a lake (L/T).
    EVAPLK : float
    The rate of evaporation per unit area from the surface of a lake (L/T).
    RNF : float
    Overland runoff from an adjacent watershed entering the lake. If RNF > 0, it is specified directly as a volumetric rate, or flux (L3 /T). If RNF < 0, its absolute value is used as a dimensionless multiplier applied to the product of the lake precipitation rate per unit area (PRCPLK) and the surface area of the lake at its full stage (occupying all layer 1 lake cells). When RNF is entered as a dimensionless multiplier (RNF < 0), it is considered to be the product of two proportionality factors. The first is the ratio of the area of the basin contributing runoff to the surface area of the lake when it is at full stage. The second is the fraction of the current rainfall rate that becomes runoff to the lake. This procedure provides a means for the automated computation of runoff rate from a watershed to a lake as a function of varying rainfall rate. For example, if the basin area is 10 times greater than the surface area of the lake, and 20 percent of the precipitation on the basin becomes overland runoff directly into the lake, then set RNF = -2.0.
    WTHDRW : float
    The volumetric rate, or flux (L3 /T), of water removal from a lake by means other than rainfall, evaporation, surface outflow, or groundwater seepage. A negative value indicates augmentation. Normally, this would be used to specify the rate of artificial withdrawal from a lake for human water use, or if negative, artificial augmentation of a lake volume for aesthetic or recreational purposes.
    SSMN : float
    Minimum stage allowed for each lake in steady-state solution. See notes on ssmn and ssmx above.
    SSMX : float
    SSMX Maximum stage allowed for each lake in steady-state solution.
  • options (list of strings) – Package options. (default is None).
  • extension (string) – Filename extension (default is ‘lak’)
  • unitnumber (int) – File unit number (default is None).
  • filenames (str or list of str) – Filenames to use for the package and the output files. If filenames=None the package name will be created using the model name and package extension and the cbc output name will be created using the model name and .cbc extension (for example, modflowtest.cbc), if ipakcbc is a number greater than zero. If a single string is passed the package will be set to the string and cbc output names will be created using the model name and .cbc extension, if ipakcbc is a number greater than zero. To define the names for all package files (input and output) the length of the list of strings should be 2. Default is None.

Notes

Parameters are not supported in FloPy.

Examples

>>> import flopy
>>> m = flopy.modflow.Modflow()
>>> lak = {}
>>> lak[0] = [[2, 3, 4, 15.6, 1050., -4]]  #this lake boundary will be
>>>                                        #applied to all stress periods
>>> lak = flopy.modflow.ModflowLak(m, nstress_period_data=strd)
classmethod load(f, model, nper=None, ext_unit_dict=None)[source]

Load an existing package.

Parameters:
  • f (filename or file handle) – File to load.
  • model (model object) – The model object (of type flopy.modflow.mf.Modflow) to which this package will be added.
  • nper (int) – The number of stress periods. If nper is None, then nper will be obtained from the model object. (default is None).
  • ext_unit_dict (dictionary, optional) – If the arrays in the file are specified using EXTERNAL, or older style array control records, then f should be a file handle. In this case ext_unit_dict is required, which can be constructed using the function flopy.utils.mfreadnam.parsenamefile.
Returns:

str – ModflowLak object.
Return type:

ModflowLak object

Examples

>>> import flopy
>>> m = flopy.modflow.Modflow()
>>> lak = flopy.modflow.ModflowStr.load('test.lak', m)
write_file()[source]

Write the package file.

Returns:
Return type:None