1 Lawrence Berkeley National Laboratory, University of California, Earth Sciences Division 2 University of Oslo, Department of Geophysics, Simulating Unsaturated Flow Fields Based on Ground Penetrating Radar and Saturation Measurements Stefan Finsterle 1 andNils-Otto Kitterød 2
Purpose: Estimate unsaturated flow velocities by 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 railway runways utm-E utm-N Moreppen research site 10m N Moreppen research site 615,750615,800 6,677,740 6,677,760 6,677,780 6,677,800 6,677,820 6,677,840 p42 p44 p46 p48 p33 p41 p43 p45 p47 p35
p47 Delta topset Delta foreset What did we see?Cross section of a delta Delta bottomset Iso-crones Delta foreset Delta topset Sea level (~ BP)
p47 p45 p43 p41 GPR profiles p41 p43 p45 p47 Moreppen N 10 m
Why GPR? geological architecture depth [m] West- East position [m] Significance of heterogeneities to flow? soil moisture content, because = f( ) inverse modeling
Why soil moisture? easy high resolution in space continuous in time (compared to other variables) satellite radar GPR profiles p41 p43 p45 p47 Moreppen N 10 m N12 N10 N18 N20 N34 N32 N30 N40 N38 N36 N46 N44 N42 N12 N10 N18 N20 N34 N32 N30 N40 N38 N36 N46 N44 N42 GPR(44)GPR(46) GPR(47) GPR(45) 5 m
soil moisture content 0.2 m below the surface Moreppen, delta topset May vol% H 2 O interpolation in 3D
soil moisture content 0.3 m below the surface Moreppen, delta topset May vol% H 2 O
soil moisture content 0.5 m below the surface Moreppen, delta topset May vol% H 2 O
soil moisture content 1.0 m below the surface Moreppen, delta topset May vol% H 2 O
soil moisture content 1.5 m below the surface Moreppen, delta topset May vol% H 2 O
soil moisture content 2.0 m below the surface Moreppen, delta topset May vol% H 2 O
soil moisture content 2.5 m below the surface Moreppen, delta foreset May vol% H 2 O
soil moisture content 3.0 m below the surface Moreppen, delta foreset May vol% H 2 O
soil moisture content 3.5 m below the surface Moreppen, delta foreset May vol% H 2 O
soil moisture content 3.7 m below the surface Moreppen, below groundwater table May vol% H 2 O
soil moisture content Moreppen, fence diagram May vol% H 2 O
Why inverse modeling? honor observations include a priori information consistent homogenization question of scale!!
find model parameters that minimize | cal. – obs. | Inverse modeling: k abs,S r, 1/ , n | calc – obs |
depth (m) depth (m) top1 top2 dip1 dip2 dry saturated ~ 0.5 sat. depth (m) c11c16
top1 top2 dip1 dip2 observed most likely with uncertanty 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 reproduced are we able to reproduce (or make forecasts) of non-observed variables?, but
GPR profiles p41 p43 p45 p47 Moreppen N 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)
depth (m) day 1 day 2 day 3
F(x) for [Br] and [HTO] time Søvik and Alfnes et al. (2001) Moreppen tracer test m (Br) m (Br) m (Br) m (Br) m (Br) m (HTO) m (HTO) m (HTO) m (HTO) m (HTO) 1.8 m iso 2.8 m iso 3.3 m iso 1.8 m ani 2.8 m ani 3.3 m ani
Future work 1) Preferential flow How much ? How fast? F(x) for [Br] and [HTO] time m (Br) m (Br) 2)Effective parameters
homogeneous anisotropic heterogeneous isotropic
c a b
breakthrough curves (42 mm/d infiltration) time (days) number of particles heterogeneous isotropic (case a) pressure (all) pressure and saturation saturation (no dip2) pressure (no dip2) homogeneous anisotropic saturation (all)