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

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

3. Drain Package

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

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

6. 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.

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

8. New MODFLOW Packages to simulate dynamic interchange between groundwater and surface water
• Stream Package
(Prudic, 1989)
• MODBRANCH
(Swain, 1993)
• Lake Package
(Cheng and Anderson, GW,1993)
(Council, 1998)
(Merritt and Konikow, 2000)
• Wetland Module
(Restrepo et al., GW,1998)

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

10. Transient Simulations require:
Initial Conditions
Storage Coefficient
Time step

11. Types of Initial Conditions
Static steady state
Dynamic steady state
Dynamic cyclic conditions
(Time distant conditions)