1. Types of Boundary Conditions
Specified head (including constant head)
h = f (x,y,z,t)
Specified flux (including no flow)
h/l = -ql/Kl
Head-dependent conditions
q = -Kb (hb – h)/b
Implementation
in MODFLOW

2. Versions of MODFLOW
MODFLOW 88/96
MODFLOW2000
MODFLOW2005

3. MODFLOW88/96 required Packages required 1 is required head dependent
BCs
1 is required
& PCG2

4. RIVER Package
Field setting
Representation
in the model

6. Head Dependent Boundaries MODFLOW’s River Package
hb= hR = head in the river
q = -Kb (hb – h)/b
Head Dependent Boundaries
MODFLOW’s River Package

8. w m
Q = conductance x change in head

9. Q = C (hR – hijk)
hijk w m
RBOT
Gaining River Cell

10. Q = C (hR – hijk)
RBOT
Losing River Cell

11. Q = C (hR – hijk)
RBOT
Losing River Cell

12. Percolating River Cell
Q = C (hR – RBOT)
RBOT
Percolating River Cell

13. Definitions Riverbed Conductance = (Kv/m) wL Leakance = Kv/m
Resistance = m/Kv
Kv = vertical hydraulic conductivity of riverbed sediments
m = thickness of riverbed sediments
w = width of the river
L = length of the river within the cell

14. Resistance River with sandy bottom = 1 day
Small stream with silty bottom = days
Stream/lake in till = 100 days

15. Head Dependent Boundaries
in MODFLOW88/96
Q = C h
River Package
Drain Package
General Head Boundary (GHB) Package
ET Package

16. River Package
Q = C (hR – hijk)
where
C =KvLw/m

18. Drain Package

19. Drain Package Q = C (hijk-d) Q = 0 if hijk<d
where d = head in the drain.
Q = 0 if hijk<d

20. General Head Boundary Package
Boundary cell hB L h
Q= C (hB-h)
C = K A /L

21. Evapotranspiration (EVT) Package
…to be discussed later,
when we do the Final Project

22. Lake Model hB L GHB Q = C (hB - h) C = Conductance = K A/L
K is the hydraulic conductivity of the aquifer between the model and the lake;
A is the area of the boundary cell, perpendicular to flow.

23. Streamflow Package (Prudic 1989)- see p. 127 A&WQ
Allows for dynamic interchange of
groundwater and streamflow; solves
for stream stage.
Manning’s Equation:
d = (Q n / C w S1/2)3/5
n is Manning’s Roughness coefficient
New MODFLOW Package available in MODFLOW2000.
• Streamflow Routing Package (Prudic 2004)

24. Estimating Manning’s n

27. • Lake Package – Available in MODFLOW2000
(Cheng and Anderson, GW,1993)
(Council, 1998)
(Merritt and Konikow, 2000)
Solves for lake levels
• MODBRANCH
(Swain, 1993)
• Wetland Module
(Restrepo et al., GW,1998)
Other packages:

28. Lake (LAK) Package
Change in Storage = Outflow - Inflow
Change in lake level = Change in Storage/Area

29. Head Dependent Boundaries
in original MODFLOW88/96
Q = C h
River Package
Drain Package
General Head Boundary (GHB) Package
ET Package
Prudic’s 1989 Streamflow Package and a few other
packages have since been added to MODFLOW88/96
and are available when running MODFLOW88/96
in Groundwater Vistas.