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Types of Boundary Conditions

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Title: Types of Boundary Conditions


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 Packages
required
required
head dependent BCs
1 is required
PCG2
4
RIVER Package
Field setting
Representation in the model
5
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6
hb hR head in the river
q -Kb (hb h)/b
Head Dependent Boundaries MODFLOWs River Package
7
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8
Q conductance x change in head
9
Q C (hR hijk)
hijk
RBOT
Gaining River Cell
10
Q C (hR hijk)
RBOT
Losing River Cell
11
Q C (hR hijk)
RBOT
Losing River Cell
12
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 1- 10 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
17
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18
Drain Package
19
Drain Package
Q C (hijk-d) where d head in the drain. Q 0
if hijkltd
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
GHB
L
Lake
Model
hB
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 AW

Q
Allows for dynamic interchange of groundwater and
streamflow solves for stream stage.
Mannings Equation d (Q n / C w S1/2)3/5 n
is Mannings Roughness coefficient
New MODFLOW Package available in MODFLOW2000.
Streamflow Routing Package (Prudic 2004)
24
Estimating Mannings n
http//www.engineering.usu.edu/classes/cee/5470/ws
p2339.pdf
25
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26
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27
Lake Package Available in MODFLOW2000
(Cheng and Anderson, GW,1993) (Council, 1998)
(Merritt and Konikow, 2000)
Solves for lake levels
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

Prudics 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.
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