GLY 521- Hydrogeology

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GLY 521- Hydrogeology

• Modflow Packages

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Modflow Packages
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Block Center Flow (BCF) Package

• The BCF package is the central package for all
  solutions
• Specify the way each cell will be treated here

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Conductance
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Recharge Package

• One value assigned to each vertical column
• Can assign to uppermost cell or specified layer

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Evapotranspiration Package

• Allows ET only when water table depth is shallow
• Can allow ET only from uppermost cells

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River Package
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River Package
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River Package
Stage above water table
Stage below water table
Water table below bed
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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.
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Stream Package (Prudic 1989)

• Not part of original Modflow
• Routes water through stream segments
• Calculates stage in reaches using channel
  hydraulics (Mannings Equation)

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General Head Boundary
boundary
model cell
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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
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General Head Boundary

• Caution! Make sure GHB is does not affect model
  area
• Can use zone budget to assure water balance

GHB
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Zone Budget

• Not a package, but a separate program
• Specify groups of cells as zones and zonebudget
  calculates water balance on each zone