GLY 521- Hydrogeology

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GLY 521- Hydrogeology
Modflow Packages
Modflow Packages
Block Center Flow (BCF) Package
• The BCF package is
the central package for
all solutions
• Specify the way each
cell will be treated here
Conductance
Recharge
Package
• One value assigned
to each vertical
column
• Can assign to
uppermost cell or
specified layer
Evapotranspiration Package
• Allows ET only
when water table
depth is shallow
• Can allow ET
only from
uppermost cells
River Package
River Package
River Package
Stage above
water table
Stage below
water table
Water table
below bed
River Package
Note: you want to make sure that the total flux to the stream is
preserved at a given head difference. Conductance should be
preserved, even if stream geometry is not.
Stream Package (Prudic 1989)
• Not part of original
Modflow
• Routes water through
stream segments
• Calculates stage in
reaches using channel
hydraulics
(Manning’s Equation)
General Head Boundary
model cell
boundary
General Head Boundary
• GHB package often
used to simulate
lakes and reservoirs
• Can also be used to
“telescope” a model
down to a smaller
area
GHB
General Head Boundary
• Caution! Make sure
GHB is does not
affect model area
• Can use zone budget
to assure water
balance
GHB
Zone Budget
• Not a package, but a
separate program
• Specify groups of
cells as “zones” and
zonebudget calculates
water balance on
each zone

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