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