GLY 521- Hydrogeology 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

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 boundary model 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