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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
boundarymodel cell
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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