readbtn: Read MT3D .btn File
In dpphat/MFtools: This is a package for reading MODFLOW and MT3DMS files

This function reads in a btn file and creates a list composed of the following vectors:

NLAY: Atomic Vector of the Number of Layers in the Model Grid
NCOL: Atomic Vector of the Number of Columns in the Model Grid
NROW: Atomic Vector of the Number of Rows in the Model Grid
NPER: Atomic Vector of the Number of Stress Periods in the Model
NCOMP: Atomic Vector of the Number of Compounds in the Model
MCOMP: Atomic Vector of the Number of Mobile Compounds in the Model
TUNIT: Atomic Vector of the Number of Time Unit
LUNIT: Atomic Vector of the Number of Length Unit
MUNIT: Atomic Vector of the Number of Mass Unit
TRNOP: Logical Vector of Packages To Use
LAYCON: Vector of Layer Types: LAYCON = 0 = Confined, LAYCON != 0 = Unconfined or Convertible
dX: Cell Width Along Columns
X: Cell Center Coordinate in the Model Coordinate System
dY: Cell Width Along Rows
Y: Cell Center Coordinate in the Model Coordinate System
TOP: Top Elevation of Layer 1
TRANS

Data frame composed of LAY, ROW, COL, dZ, PRSITY, ICBUND, SONC, where these values are defined as follows:

dZ: Layer Thicknesses
PRSITY: Porosity
ICBUND: ICBUND array. See MT3DMS manual for a description of ICBUND
SCONC: Starting Concentrations at the beginning of the simulation
CINACT: Value that indicates an inactive value
THKMIN: Minimum saturated thickness in a cell
IFMTCN: Flag indicating whether the calculated concentration should be printed to the standard output text file and also serves as a printing-format code if it is printed
IFMTNP: Flag indicating if the number of particles in each cell should be printed and also serves as a printing format code if it is printed
IFMTRF: Flag indicating if the model-calculated retardation factor should be printed and also serves as a printing format code if it is printed
IFMTDP: Flag indicating if the model-calculated distance-weighted dispersion coefficient should be printed and also serves as a printing format code if it is printed
SAVUCN: Logical flag indicating if the concentration solution should be saved to a .ucn file
NPRS: Flag indicating the frequncy of output and also indicating whether the frequency output is specified in terms of total elapsed simulation time or the transport step number. See MT3D Manual for further details of NPRS
TIMPRS: Total elapsed time at which the simulation results are printed
NOBS: Number of Observations wells recording concentration data
NPROBS: Integer indicating how frequently the concentration is recorded at each Observation Well
OBSLOC: Cell indices (L, R, C) of Observation Well locations
CHKMAS: Logical Flag indicating whether a one-line summary of mass balance information should be printed
NPRMAS: Integer indicating how frequently the mass budget information should be recorded
PERLEN: Lengths of Stress Perids
NSTP: Number of time-steps for the transient flow folution in each stress-period
TSMULT: Time-step multiplier. Only used if NSTP > 1. See MT3DMS Manual for further details
TSLNGHdf: If TSMULT < 0, TSLNGHdf frovides the length of time-steps for the flow solution in each stress period
DT0: The user-specified transport step size within each time-step of the flow solution
MXSTRN: The maximum number of transport time steps allowed within one time step of the flow solution
TTSMULT: A multiplier for successive transport steps within a flow step
TTSMAX: Maximum transport step size allowed when transport step size multiplier TTSMULT > 1.0

1	readbtn(rootname)

rootname

This is the root name of the btn file

readbtn("T04")

# Find the average initial concentration assigned to the MT3DMS Model
btn <- readbtn("T04")
btn$TRANS %>% 
select(SCONC) %>%
summarise(AVG = mean(SCONC))

> A tibble: 1 x 1
>        AVG
>      <dbl>
> 1 17.77554

# Find the average initial concentration (> 5 Âµg/L) 
# assigned to Layer 1 of the MT3DMS Model
btn$TRANS %>% 
filter(LAY == 1) %>%
select(SCONC) %>%
filter(SCONC >= 5) %>%
summarise(AVG = mean(SCONC))

> A tibble: 1 x 1
>        AVG
>      <dbl>
> 1 1096.754

# Find the range of porosity values assigned to the model 
btn$TRANS %>%                  # Select the RCL Value table that contains the porosity values
select(PRSITY) %>%             # Select the table column that contains porosity values
t() %>%                        # Convert to a vector of values
as.factor() %>%
levels()

> [1] "0.15" "0.21" "0.25" "0.4"