1 Lawrence Berkeley National Laboratory, University of California, Earth Sciences Division2 University of Oslo, Department of Geophysics, nilsotto@geofysikk.uio.no

Simulating Unsaturated Flow Fields

Based on

Ground Penetrating Radar and Saturation Measurements

Stefan Finsterle1 and Nils-Otto Kitterød2

Purpose: Estimate unsaturated flow velocitiesby inverse modelling of flow parameters

conditioned on soil moisture content

and Ground Penetrating Radar

Why soil moisture?

Why unsaturated flow?

Why inverse modelling?

Why Ground Penetrating Radar?

Why do a tracer test?

Why unsaturated flow?

Protection of groundwater resources

The Gardermoen airport

The Moreppen research station

Oslo Airport Gardermoen

4 km

2 km

Residence time?

On the runways (acetate, formeate)

On the airplanes (glycol)

Consumption of ~ 400 mill. liter/year

Deicing chemical

Jet fuel

Main problem:

Good remediation potential in the unsaturated zone(oxygen is the best electron acceptor)

However:

Why Ground Penetrating Radar?

Electromagnetic Wave Propagation

2 = j ( + j )

Soil moisture content, : = f()

Sedimentological heterogeneities

Most important in unsaturated zone

Oslo Airport Gardermoen

railwayrunways

utm-E

utm-N

616 000 618 000

6672500

6674500

6676500

Moreppenresearch site

10m

N

Moreppen research site

615,750 615,8006,677,740

6,677,760

6,677,780

6,677,800

6,677,820

6,677,840

p42 p44 p46p48

p33

p41

p43

p45

p47

p35

p47Delta topset

Delta foreset

What did we see? Cross section of a delta

Delta bottomset

Iso-crones

Delta foreset

Delta topsetSea level (~10.000 BP)

p47

p45

p43

p41

GPR profiles

p41p43p45p47

MoreppenN

10 m

Why GPR?

geological architecturede

pth

[m]

0

2

4

0 20 40

West- East position [m]

Significance of heterogeneities to flow?

soil moisture content, because = f()

inverse modeling

Why soil moisture?

easyhigh resolution in spacecontinuous in time

(compared to other variables)

satellite radar

GPR profiles

p41p43p45p47

Moreppen

N

10 m

N12

N10N18

N20

N34

N32

N30

N40

N38

N36

N46

N44

N42

N12

N10N18

N20

N34

N32

N30

N40

N38

N36

N46

N44

N42

GPR(44) GPR(46)

GPR(47)

GPR(45)

5 m

soil moisture content0.2 m below the surface Moreppen,

delta topset

May 11. 1995

vol% H2O

3.0 29.8

interpolationin 3D

soil moisture content0.3 m below the surface

Moreppen,

delta topset

May 11. 1995

vol% H2O

3.0 29.8

soil moisture content0.5 m below the surface Moreppen,

delta topset

May 11. 1995

vol% H2O

3.0 29.8

soil moisture content1.0 m below the surface Moreppen,

delta topset

May 11. 1995

vol% H2O

3.0 29.8

soil moisture content1.5 m below the surface Moreppen,

delta topset

May 11. 1995

vol% H2O

3.0 29.8

soil moisture content2.0 m below the surface Moreppen,

delta topset

May 11. 1995

vol% H2O

3.0 29.8

soil moisture content2.5 m below the surface

Moreppen,

delta foreset

May 11. 1995

vol% H2O

3.0 29.8

soil moisture content3.0 m below the surface

Moreppen,

delta foreset

May 11. 1995

vol% H2O

3.0 29.8

soil moisture content3.5 m below the surface

Moreppen,

delta foreset

May 11. 1995

vol% H2O

3.0 29.8

soil moisture content3.7 m below the surface Moreppen,

below groundwater table

May 11. 1995

vol% H2O

3.0 29.8

soil moisture content

Moreppen,

fence diagram

May 11. 1995

vol% H2O

3.0 29.8

Why inverse modeling?

honor observationsinclude a priori informationconsistent homogenization

question of scale!!

find model parametersthat minimize | cal. – obs. |

Inverse modeling:

kabs,Sr, 1/, n

| calc – obs |

dept

h (m

)

0

-1

-2

-3

2 4 6 8 10 12

dept

h (m

)

0

-1

-2

-3

2 4 6 8 10 12

top1top2

dip1dip2

drysaturated~ 0.5 sat.

dept

h (m

)

0

-1

-2

-3

2 4 6 8 10 12

c11 c16

top1

top2

dip1

dip2

observed

most likely

withuncertanty

c11 and c16 are the conditioning wells

obs – calc for the whole flow domain

Why do a tracer test?

validate model parameters by independent observations

Primary observations is reproducedare we able to reproduce (or make forecasts)

of non-observed variables?

, but

GPR profiles

p41p43p45p47

MoreppenN

10 m

GPR profiles

p41 p43 p45 p47

Moreppen

N

10 m

Lysimeter trench

GPR profiles

p41 p43 p45 p47

Moreppen

N

10 m

Prenart probe

3.5 m

6 m

2.3 m

Background, 48 mm/day, through the dripper lines

Bromide (Br)Tritiated water (HTO)

dept

h (m

)

0

-1

-2

-3

0

-1

-2

-3

2 4 6 8 10 12

0

-1

-2

-3

day 1

day 2

day 3

0.00

0.20

0.40

0.60

0.80

1.00

F(x

) fo

r [B

r] a

nd

[H

TO

]

0.00 5.00 10.00 15.00 20.00 25.00 30.00

time <days>

Søvik and Alfnes et al. (2001)

Moreppen tracer test

-1.82 m (Br)-1.83 m (Br)

-2.95 m (Br)-3.09 m (Br)-3.30 m (Br)-1.78 m (HTO)-2.49 m (HTO)-2.95 m (HTO)-3.09 m (HTO)-3.30 m (HTO)1.8 m iso2.8 m iso3.3 m iso

1.8 m ani2.8 m ani3.3 m ani

Future work

1) Preferential flow

How much ?How fast?

0.0

0.2

0.4

0.6

0.8

1.0

F(x

) fo

r [B

r] a

nd

[H

TO

]

0 5 10 15 20 25 30

time <days>

-2.48 m (Br)-2.84 m (Br)

2) Effective parameters

0

-1

-2

-3

2 4 6 8 10 12

homogeneousanisotropic

heterogeneousisotropic

cab

breakthrough curves (42 mm/d infiltration)

time (days) 7 8 9 10 11 12

num

ber

of p

arti

cles

10

15

5

heterogeneous isotropic (case a)

pressure (all)pressure and saturation

saturation (no dip2)

pressure (no dip2)

homogeneous anisotropic saturation (all)