Slide #1.

Types of Boundary Conditions 1. Specified head (including constant head) h = f (x,y,z,t) 2. Specified flux (including no flow) h/l = -ql/Kl 3. Head-dependent conditions q = -Kb (hb – h)/b Implementation in MODFLOW
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Slide #2.

Versions of MODFLOW MODFLOW 88/96 MODFLOW2000 MODFLOW2005
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Slide #3.

required MODFLOW88/96 Packages required head dependent BCs 1 is required & PCG2
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Slide #4.

RIVER Package Field setting Representation in the model
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Slide #6.

hb= hR = head in the river q = -Kb (hb – h)/b Head Dependent Boundaries MODFLOW’s River Package
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Slide #8.

m w Q = conductance x change in head
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Slide #9.

Q = C (hR – hijk) hijk m RBOT w Gaining River Cell
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Slide #10.

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

Q = C (hR – hijk) RBOT Losing River Cell
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Slide #12.

Q = C (hR – RBOT) RBOT Percolating River Cell
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Slide #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
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Slide #14.

Resistance River with sandy bottom = 1 day Small stream with silty bottom = 1- 10 days Stream/lake in till = 100 days
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Slide #15.

Head Dependent Boundaries in MODFLOW88/96 Q = C h • River Package • Drain Package • General Head Boundary (GHB) Package • ET Package
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Slide #16.

River Package Q = C (hR – hijk) where C =KvLw/m
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Slide #18.

Drain Package
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Slide #19.

Drain Package Q = C (hijk-d) where d = head in the drain. Q = 0 if hijk
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Slide #20.

General Head Boundary Package Boundary cell L h Q= C (hB-h) C = K A /L hB
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Slide #21.

Evapotranspiration (EVT) Package …to be discussed later, when we do the Final Project
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Slide #22.

GHB L 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. hB
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Slide #23.

• Streamflow Package (Prudic 1989)- see p. 127 A&W 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) Q
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Slide #24.

Estimating Manning’s n http://www.engineering.usu.edu/classes/cee/5470/wsp2339.pdf
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Slide #27.

• Lake Package – Available in MODFLOW2000 (Cheng and Anderson, GW,1993) (Council, 1998) (Merritt and Konikow, 2000) Solves for lake levels Other packages: • Wetland Module (Restrepo et al., GW,1998) • MODBRANCH (Swain, 1993)
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Slide #28.

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