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©1995, 1996, Richard B. Winston,
Last modified on Wednesday, January 31, 1996 - 5:02:12 PM
Skip forward to Input instructions for the Block-Centered Flow, Version 1.
If your version of MODFLOW has version 2 (BCF2) or version 3 (BCF3) you may wish to switch to the instructions for those packages. Input files prepared for Block-Centered Flow, Version 1 will work with versions 2 and 3 but the added capabilities of those latter versions will not be implemented.
The original instructions for the Block-Centered Flow Package, Version 1, (BCF1) are on pages 5-37 to 5-40 of McDonald and Harbaugh (1988).
Introduction: The Block-Centered Flow Package, Version 1, (BCF1) is used to describe the width of the rows and columns, the layer types (confined, unconfined, or variable) and the hydrologic properties of the aquifer(s). These include, hydraulic conductivity or transmissivity, storage characteristics, elevations of the tops and bottoms of all layers, anisotropy between the x and y directions and vertical leakance terms.
Although this may seem obvious, if you specify both the tops and bottoms of layers, the bottom of every cell in a layer must be above or at the top of the cell in the underlying layer. The layers are numbered from top to bottom. All numbers should be right justified
Lines 1-5 are the same for all models and are entered only once. The subsequent lines are repeated for each layer but only some of the lines are used for each layer depending primarily on whether a model is steady state or transient, and the layer type. The bottom layer is treated a little differently than the others. No vertical conductance is specified for it. There are specialized instructions for each case.
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All input parameters should be right justified.
- Line 1
- Lines 2+
- LAYCON array, Format = 40I2, up to two lines, = 0 if confined, =1 if unconfined (only valid for layer 1), =2 if variable but with constant transmissivity, =3 if variable and with variable transmissivity
- Lines 3+
- TRPY(NLAY) anisotropy array entered using U1DREL, Ratio of transmissivity or conductivity along columns to that along rows. One value for each layer.
- Lines 4+
- DELR(NCOL) array entered using U1DREL, Cell width along rows, one value for each column.
- Lines 5+
- DELC(NROW) array entered using U1DREL, Cell width along columns, one value for each row.
- Lines 6+, Use only for transient simulations
- sf1(NCOL,NROW) array entered using U2DREL, primary storage coefficient (specific yield for water table aquifers, specific storage times layer thickness for confined or variable aquifers).
- Lines 7+, Use only for confined aquifers or variable aquifers with constant transmissivity (LAYCON = 0 or 2)
- Lines 8+, Use only for unconfined aquifers or variable aquifers with variable transmissivity (LAYCON = 1 or 3)
- Lines 9+, Use only for unconfined aquifers or variable aquifers with variable transmissivity (LAYCON = 1 or 3)
- Lines 10+, Use for all layers EXCEPT
the bottom layer
- Vcont(NCOL,NROW) array entered using U2DREL, Vertical hydraulic conductance term (1/(Sum(z/K)) where K = hydraulic conductivity, z terms are measured from the center of the block in the layer for which data is being entered to the center of the layer beneath. (Equation 49, p. 5-12, McDonald and Harbaugh, 1988)
- Lines 11+, Use if the simulation is transient AND the aquifer has variable confinement (LAYCON = 2 OR 3)
- Lines 12+, Use if the aquifer has variable confinement (LAYCON = 2 OR 3)
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Enter a right-justified 0 for transient simulations. Enter a nonzero integer for steady state simulations.
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Use this variable to tell where cell-by-cell flow terms for the Block Centered Flow package should be saved or if flow at constant head cells should be printed. It should be right justified. You must also set ICBCFL in the Output Control option to print or save cell-by-cell flow terms.
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For each layer, starting at the top, enter a right justified integer to tell what type of aquifer that layer represents. Two spaces are reserved for each layer. Use only one line if there are 40 or fewer layers. Use two lines for 41-80 layers.
- LAYCON(i)=0 for confined aquifers.
- LAYCON(i)=1 for unconfined aquifers. (Valid only for layer 1, the top layer)
- LAYCON(i)=2 for aquifers which switch between confined and unconfined conditions but with constant transmissivity. (This implies that aquifer thickness is large compared to the maximum thickness of the unsaturated zone in the aquifer during unconfined conditions.)
- LAYCON(i)=3 for aquifers which switch between confined and unconfined conditions and with variable transmissivity. (Transmissivity will be calculated based on hydraulic conductivity and saturated thickness.)
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- Enter the anisotropy for each layer as the ratio of transmissivity or conductivity along columns to that along rows. Enter one value for each layer.
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Enter the width of each column going from left to right.
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Enter the width of each row going from top to bottom. (Please note that it is easy to get this reversed because in plots of y vs. x, y decrease from top to bottom whereas here, row numbers increase from top to bottom. The calculations should not be affected if you get this backwards but you may increase the difficulty of transferring the data to some other program such as a plotting program or spreadsheet.)
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Enter the primary storage coefficients for each cell (specific yield for water table aquifers, specific storage times layer thickness for confined or variable aquifers). Specific storage times layer thickness is referred to as "confined storage coefficient" in the original documentation of the Block Centered Flow Package.
Lines 6+ to 12+ are entered once for each layer. Enter all the lines for one layer before going on to the next layer.
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Use only for confined aquifers or variable aquifers with constant transmissivity (LAYCON = 0 or 2)
Enter the transmissivity along rows. Transmissivity along columns will be calculated by multiplying by TRPY.
Lines 6+ to 12+ are entered once for each layer. Enter all the lines for one layer before going on to the next layer.
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Use only for unconfined aquifers or variable aquifers with variable transmissivity (LAYCON = 1 or 3)
Enter the hydraulic conductivity along rows. Hydraulic conductivity along columns will be calculated by multiplying by TRPY.
Lines 6+ to 12+ are entered once for each layer. Enter all the lines for one layer before going on to the next layer.
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Use only for unconfined aquifers or variable aquifers with variable transmissivity (LAYCON = 1 or 3)
Enter the elevation of the bottom of the aquifer for each cell.
Lines 6+ to 12+ are entered once for each layer. Enter all the lines for one layer before going on to the next layer.
Go back to Input instructions for the Block-Centered Flow (Version 1) Package.
Use for all layers EXCEPT the bottom layer
Enter the vertical hydraulic conductance term for each cell. The vertical conductance term is calculated as (1/(Sum(z/K)) where K = hydraulic conductivity, and z terms are measured from the center of the cell in the layer for which data is being entered to the center of the cell immediately beneath it. (Equation 49, p. 5-12, McDonald and Harbaugh, 1988).
For example, suppose that the cell for which data is being entered is 5 m thick with a hydraulic conductivity of 10^-3 m/s and the cell in the layer immediately beneath it is 8 m thick with a hydraulic conductivity of 5*10^-4 m/s. The z term for the top layer is 5/2 = 2.5 m and the z term for the bottom layer is 8/2 = 4 m. The vertical conductance term is thus
V = 1/[(2.5/{10^-3})+(4/{5*10^-4})]
V = 1/[2.5*10^3+8*10^3]
V = 1/[1.05*10^4]
V = 9.52*10^-5 s^-1
In a quasi-three dimensional model, there might be a confining bed between two adjacent layers. The confining bed would not be modeled directly but its affects on the hydrology of the adjoining aquifers would be incorporated into the vertical conductance term. For example, suppose that the two layers in the example above were separated by a 3 m thick confining bed with a hydraulic conductivity of 10^-8 m/s. The z value for the confining bed would be it's thickness (3 m) and the vertical conductance term would be calculated as
V = 1/[(2.5/{10^-3})+(3/{10^-8})+(4/{5*10^-4})]
V = 1/[2.5*10^3+3*10^8+8*10^3]
V = 1/[3.000105*10^8]
V = 3.3*10^-9 s^-1
Lines 6+ to 12+ are entered once for each layer. Enter all the lines for one layer before going on to the next layer.
Go back to Input instructions for the Block-Centered Flow (Version 1) Package.
Use if the simulation is transient AND the aquifer has variable confinement (LAYCON = 2 OR 3)
Enter the specific yield for all cells. In the original documentation this is referred to as the secondary storage coefficient. The primary storage coefficient for unconfined aquifers is also the specific yield but in that case there is no secondary storage coefficient.
Lines 6+ to 12+ are entered once for each layer. Enter all the lines for one layer before going on to the next layer.
Go back to Input instructions for the Block-Centered Flow (Version 1) Package.
Use if the aquifer has variable confinement (LAYCON = 2 OR 3)
Enter the elevation of the top of the aquifer for each cell.
Lines 6+ to 12+ are entered once for each layer. Enter all the lines for one layer before going on to the next layer.
Go back to Lines 6+
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LAYCON=0 (confined), Steady State, Transient
LAYCON=1 (unconfined), Steady State, Transient
LAYCON=2 (variable, constant transmissivity), Steady State, Transient
LAYCON=3 (variable, variable transmissivity), Steady State, Transient
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LAYCON=0 (confined), Steady State
- Line 1
- Lines 2+
- LAYCON array, Format = 40I2, up to two lines, = 0 if confined, =1 if unconfined, =2 if variable but with constant transmissivity, =3 if variable and with variable transmissivity
- Lines 3+
- TRPY(NLAY) anisotropy array entered using U1DREL, Ratio of transmissivity or conductivity along columns to that along rows. One value for each layer.
- Lines 4+
- DELR(NCOL) array entered using U1DREL, Cell width along rows, one value for each column.
- Lines 5+
- DELC(NROW) array entered using U1DREL, Cell width along columns, one value for each row.
- Lines 7+,
- Lines 10+, Use for all layers EXCEPT
the bottom layer
- Vcont(NCOL,NROW) array entered using U2DREL, Vertical hydraulic conductance term (1/(Sum(z/K)) where K = hydraulic conductivity, z terms are measured from the center of the block in the layer for which data is being entered to the center of the layer beneath. (Equation 49, p. 5-12, McDonald and Harbaugh, 1988)
Go back to Lines 7+ or the top of this section.
Go back to Specialized Instructions
Go back to Input instructions for the Block-Centered Flow (Version 1) Package.
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LAYCON=0 (confined), Transient
- Line 1
- Lines 2+
- LAYCON array, Format = 40I2, up to two lines, = 0 if confined, =1 if unconfined, =2 if variable but with constant transmissivity, =3 if variable and with variable transmissivity
- Lines 3+
- TRPY(NLAY) anisotropy array entered using U1DREL, Ratio of transmissivity or conductivity along columns to that along rows. One value for each layer.
- Lines 4+
- DELR(NCOL) array entered using U1DREL, Cell width along rows, one value for each column.
- Lines 5+
- DELC(NROW) array entered using U1DREL, Cell width along columns, one value for each row.
- Lines 6+, Use only for transient simulations
- sf1(NCOL,NROW) array entered using U2DREL, primary storage coefficient (specific yield for water table aquifers, specific storage times layer thickness for confined or variable aquifers).
- Lines 7+, Use only for confined aquifers or variable aquifers with constant transmissivity (LAYCON = 0 or 2)
- Lines 10+, Use for all layers EXCEPT
the bottom layer
- Vcont(NCOL,NROW) array entered using U2DREL, Vertical hydraulic conductance term (1/(Sum(z/K)) where K = hydraulic conductivity, z terms are measured from the center of the block in the layer for which data is being entered to the center of the layer beneath. (Equation 49, p. 5-12, McDonald and Harbaugh, 1988)
Go back to Lines 6+ or the top of this section.
Go back to Specialized Instructions
Go back to Input instructions for the Block-Centered Flow (Version 1) Package.
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LAYCON=1 (unconfined), Steady State
- Line 1
- Lines 2+
- LAYCON array, Format = 40I2, up to two lines, = 0 if confined, =1 if unconfined (valid only for layer 1), =2 if variable but with constant transmissivity, =3 if variable and with variable transmissivity
- Lines 3+
- TRPY(NLAY) anisotropy array entered using U1DREL, Ratio of transmissivity or conductivity along columns to that along rows. One value for each layer.
- Lines 4+
- DELR(NCOL) array entered using U1DREL, Cell width along rows, one value for each column.
- Lines 5+
- DELC(NROW) array entered using U1DREL, Cell width along columns, one value for each row.
- Lines 8+, Use only for unconfined aquifers or variable aquifers with variable transmissivity (LAYCON = 1 or 3)
- Lines 9+, Use only for unconfined aquifers or variable aquifers with variable transmissivity (LAYCON = 1 or 3)
- Lines 10+, Use for all layers EXCEPT
the bottom layer
- Vcont(NCOL,NROW) array entered using U2DREL, Vertical hydraulic conductance term (1/(Sum(z/K)) where K = hydraulic conductivity, z terms are measured from the center of the block in the layer for which data is being entered to the center of the layer beneath. (Equation 49, p. 5-12, McDonald and Harbaugh, 1988)
LAYCON=1 (unconfined) is only valid for layer 1, Lower layers that can be unconfined must be entered using LAYCON=2 or 3.
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LAYCON=1 (unconfined), Transient
- Line 1
- Lines 2+
- LAYCON array, Format = 40I2, up to two lines, = 0 if confined, =1 if unconfined (only valid for layer 1), =2 if variable but with constant transmissivity, =3 if variable and with variable transmissivity
- Lines 3+
- TRPY(NLAY) anisotropy array entered using U1DREL, Ratio of transmissivity or conductivity along columns to that along rows. One value for each layer.
- Lines 4+
- DELR(NCOL) array entered using U1DREL, Cell width along rows, one value for each column.
- Lines 5+
- DELC(NROW) array entered using U1DREL, Cell width along columns, one value for each row.
- Lines 6+, Use only for transient simulations
- sf1(NCOL,NROW) array entered using U2DREL, primary storage coefficient (specific yield for water table aquifers, specific storage times layer thickness for confined or variable aquifers).
- Lines 8+, Use only for unconfined aquifers or variable aquifers with variable transmissivity (LAYCON = 1 or 3)
- Lines 9+, Use only for unconfined aquifers or variable aquifers with variable transmissivity (LAYCON = 1 or 3)
- Lines 10+, Use for all layers EXCEPT
the bottom layer
- Vcont(NCOL,NROW) array entered using U2DREL, Vertical hydraulic conductance term (1/(Sum(z/K)) where K = hydraulic conductivity, z terms are measured from the center of the block in the layer for which data is being entered to the center of the layer beneath. (Equation 49, p. 5-12, McDonald and Harbaugh, 1988)
LAYCON=1 (unconfined) is only valid for layer 1, Lower layers that can be unconfined must be entered using LAYCON=2 or 3.
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LAYCON=2 (variable, constant transmissivity), Steady State
- Line 1
- Lines 2+
- LAYCON array, Format = 40I2, up to two lines, = 0 if confined, =1 if unconfined, =2 if variable but with constant transmissivity, =2 if variable and with variable transmissivity
- Lines 3+
- TRPY(NLAY) anisotropy array entered using U1DREL, Ratio of transmissivity or conductivity along columns to that along rows. One value for each layer.
- Lines 4+
- DELR(NCOL) array entered using U1DREL, Cell width along rows, one value for each column.
- Lines 5+
- DELC(NROW) array entered using U1DREL, Cell width along columns, one value for each row.
- Lines 7+, Use only for confined aquifers or variable aquifers with constant transmissivity (LAYCON = 0 or 2)
- Lines 10+, Use for all layers EXCEPT
the bottom layer
- Vcont(NCOL,NROW) array entered using U2DREL, Vertical hydraulic conductance term (1/(Sum(z/K)) where K = hydraulic conductivity, z terms are measured from the center of the block in the layer for which data is being entered to the center of the layer beneath. (Equation 49, p. 5-12, McDonald and Harbaugh, 1988)
- Lines 12+, Use if the aquifer has variable confinement (LAYCON = 2 OR 3)
Go back to Lines 7+ or the top of this section.
Go back to Specialized Instructions
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LAYCON=2 (variable, constant transmissivity)Transient
- Line 1
- Lines 2+
- LAYCON array, Format = 40I2, up to two lines, = 0 if confined, =1 if unconfined, =2 if variable but with constant transmissivity, =3 if variable and with variable transmissivity
- Lines 3+
- TRPY(NLAY) anisotropy array entered using U1DREL, Ratio of transmissivity or conductivity along columns to that along rows. One value for each layer.
- Lines 4+
- DELR(NCOL) array entered using U1DREL, Cell width along rows, one value for each column.
- Lines 5+
- DELC(NROW) array entered using U1DREL, Cell width along columns, one value for each row.
- Lines 6+, Use only for transient simulations
- sf1(NCOL,NROW) array entered using U2DREL, primary storage coefficient (specific yield for water table aquifers, specific storage times layer thickness for confined or variable aquifers).
- Lines 7+, Use only for confined aquifers or variable aquifers with constant transmissivity (LAYCON = 0 or 2)
- Lines 10+, Use for all layers EXCEPT
the bottom layer
- Vcont(NCOL,NROW) array entered using U2DREL, Vertical hydraulic conductance term (1/(Sum(z/K)) where K = hydraulic conductivity, z terms are measured from the center of the block in the layer for which data is being entered to the center of the layer beneath. (Equation 49, p. 5-12, McDonald and Harbaugh, 1988)
- Lines 11+, Use if the simulation is transient AND the aquifer has variable confinement (LAYCON = 2 OR 3)
- Lines 12+, Use if the aquifer has variable confinement (LAYCON = 2 OR 3)
Go back to Lines 6+ or the top of this section.
Go back to Specialized Instructions
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LAYCON=3 (variable, variable transmissivity), Steady State
- Line 1
- Lines 2+
- LAYCON array, Format = 40I2, up to two lines, = 0 if confined, =1 if unconfined, =2 if variable but with constant transmissivity, =3 if variable and with variable transmissivity
- Lines 3+
- TRPY(NLAY) anisotropy array entered using U1DREL, Ratio of transmissivity or conductivity along columns to that along rows. One value for each layer.
- Lines 4+
- DELR(NCOL) array entered using U1DREL, Cell width along rows, one value for each column.
- Lines 5+
- DELC(NROW) array entered using U1DREL, Cell width along columns, one value for each row.
- Lines 8+, Use only for unconfined aquifers or variable aquifers with variable transmissivity (LAYCON = 1 or 3)
- Lines 9+, Use only for unconfined aquifers or variable aquifers with variable transmissivity (LAYCON = 1 or 3)
- Lines 10+, Use for all layers EXCEPT
the bottom layer
- Vcont(NCOL,NROW) array entered using U2DREL, Vertical hydraulic conductance term (1/(Sum(z/K)) where K = hydraulic conductivity, z terms are measured from the center of the block in the layer for which data is being entered to the center of the layer beneath. (Equation 49, p. 5-12, McDonald and Harbaugh, 1988)
- Lines 12+, Use if the aquifer has variable confinement (LAYCON = 2 OR 3)
Go back to Lines 8+ or the top of this section.
Go back to Specialized Instructions
Go back to Input instructions for the Block-Centered Flow (Version 1) Package.
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LAYCON=3 (variable, variable transmissivity), Transient
- Line 1
- Lines 2+
- LAYCON array, Format = 40I2, up to two lines, = 0 if confined, =1 if unconfined, =2 if variable but with constant transmissivity, =3 if variable and with variable transmissivity
- Lines 3+
- TRPY(NLAY) anisotropy array entered using U1DREL, Ratio of transmissivity or conductivity along columns to that along rows. One value for each layer.
- Lines 4+
- DELR(NCOL) array entered using U1DREL, Cell width along rows, one value for each column.
- Lines 5+
- DELC(NROW) array entered using U1DREL, Cell width along columns, one value for each row.
- Lines 6+, Use only for transient simulations
- sf1(NCOL,NROW) array entered using U2DREL, primary storage coefficient (specific yield for water table aquifers, specific storage times layer thickness for confined or variable aquifers).
- Lines 8+, Use only for unconfined aquifers or variable aquifers with variable transmissivity (LAYCON = 1 or 3)
- Lines 9+, Use only for unconfined aquifers or variable aquifers with variable transmissivity (LAYCON = 1 or 3)
- Lines 10+, Use for all layers EXCEPT
the bottom layer
- Vcont(NCOL,NROW) array entered using U2DREL, Vertical hydraulic conductance term (1/(Sum(z/K)) where K = hydraulic conductivity, z terms are measured from the center of the block in the layer for which data is being entered to the center of the layer beneath. (Equation 49, p. 5-12, McDonald and Harbaugh, 1988)
- Lines 11+, Use if the simulation is transient AND the aquifer has variable confinement (LAYCON = 2 OR 3)
- Lines 12+, Use if the aquifer has variable confinement (LAYCON = 2 OR 3)
Go back to Lines 6+ or the top of this section.
Go back to Specialized Instructions
Go back to Input instructions for the Block-Centered Flow (Version 1) Package.
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©1995, 1996, Richard B. Winston,
rwinsto@lsuvm.sncc.lsu.edu
Dept. of Geology and Geophysics
Louisiana State University
Baton Rouge, La 70803
U.S.A.
504-388-2337
Fax 504-388-2302
http://scribe.geol.lsu.edu/rbwinston.html
ftp://aapg.geol.lsu.edu/pub/winston