Groundwater modelling, exercise 2. - mr2ue.dk · Groundwater modelling, exercise 2. ... Surfer 8, Golden Software inc., Colorado USA. ... The main model is as described in this tutorial

Groundwater modelling, exercise 2.

Building a 2D groundwater model using FemLab

Hydrological model of the Gjern River catchment

April 2006 Thue Weel Jensen

Aarhus April 2006 Title: Groundwater modelling, exercise 2. Building a 2D groundwater model using FemLab Hydrological model of the Gjern River catchment Author: Thue Weel Jensen Stud nr. 20021223 As part of: The groundwater modelling course Department of Earth Sciences, University of Aarhus Cover photo: Colour plot of hydraulic heads for the 2D Groundwater model, created in FemLab Web version: http://mr2ue.dk/www/study/papers/papers.html Department of Earth Sciences, University of Aarhus Ny Munkegade, bld. 1520 ‐ 528 DK‐8000 Aarhus C Homepage: www.mr2ue.dk

2

Contents

1 Introduction Side 3 2 Location Side 3 3 Simpel model Side 3

3.1 Method Side 3 3.2 Result Side 4 3.3 Discussion Side 4

4 Complex model Side 4

3.1 Method Side 4 3.2 Result Side 5 3.3 Discussion Side 6

5 Conclusions Side 6 References Side 7 Appendix 1 Side 8 Appendix 2 Side 9 Appendix 3.1 Side 10 Appendix 3.2 Side 11 Appendix 3.3 Side 12 Appendix 4.1 Side 13 Appendix 4.2 Side 14 Appendix 4.3 Side 15 Appendix 4.4 Side 16 Appendix 4.5 Side 17 Appendix 4.6 Side 18

3

Groundwater modelling, exercise 2. Building a 2D groundwater model using FemLab

1 Introduction

The following report is created in context with the report ʺGroundwater modelling, exercise 1. Building a geological model, by the method of Kriging, using Surfer 8ʺ This report deals with the building of a 2D groundwater model using FemLab. The modelling procedure is furthermore described in appendix 1

2 Location

The 2D profile is located in the north‐eastern part of the catchment area, going from A) UTM 32 V 558800 6232250 to B) UTM 32 V 550750 6235200. It thereby covers a cross‐section that goes from the hydrological divide to the shore of Søbygaard Lake (Appendix 2).

3 Simple model

3.1 Method

By projecting the groundwater levels from a number of wells on to the profile, a simple geological model is established. In this model it is assumed that the entire domain consists of sand with constant hydraulic conductivity K, that the bottom of the domain is constant equal to the average depth to the clay and that the recharge R is constant along the top. At the divide as well as at the bottom of the model the flux is 0 across the boundary. At the lake the boundary condition is given by a constant hydraulic head (Dirichlet)

By adjusting the values of K and R the model is calibrated to fit the true hydraulic heads along the model top. A first estimate for the values of R, can be found by looking at the annual precipitation. In the area of Gjern, the precipitation is about 930mm p.a. (corrected value). About 435mm will evaporate back to the atmosphere, and about 50% disappear as surface run‐off (DMU, 2003). This leaves us with an infiltration at about 6.88e‐9.

4

3.2 Result

Figure 3.2 shows the physical boundaries of the groundwater model. It can be seen that the groundwater level, represented as the top of the model, is dipping towards the lake.

The results of the model calibration are presented in appendix 3.1, 3.2 and 3.3.

After calibration the values of R and K is R=6.88e‐9 m/s and K=1.95e‐4 m/s

3.3 Discussion

As can be seen in appendix 3.1, 3.2, 3.3, the model is not good and it is probably fare from the true geology. But the model can be used to get an idea of what the values of K and R is.

4 Complex model

4.1 Method

A more complex model is establishes by using all the known perimeters of the geology and groundwater levels. By using the calculated grid‐data from exercise 1, the elevation of the different boundaries have been extracted at points along the profile. A 500m distance between the data points has been chosen as being sufficient.

In order to get a realistic picture of the groundwater level, a grid file has been made by using information from the GEUS well database (PC‐Jupiter).

A two layer hydrological model is established, so that the upper boundary is equal to the groundwater level and the lower boundary is equal to the clay/sand boundary. The boundary between the two hydrological layers is defined as the sand/till boundary. In the range where the groundwater level is situated at a lower elevation then the till/sand boundary, the model only consist of one layer. Figure 4.1 shows the layer boundaries of the geological model.

Variation of model boundaries

010

203040

506070

8090

0 1000 2000 3000 4000 5000 6000 7000 8000 9000 10000

Distance in meter

Elev

atio

n in

met

er

Top

Bottom

Figure 3.2: Physical boundaries of the groundwater model. Hydrological divide at x=0, Søbygaard Lake at x=8500

5

In the model, two different values of hydraulic conductivity (K1 and K2) is used for the two layers, and where the simple model was operating with a constant infiltration, this model is operating with one value R1 over the till area (x=0m to x=5500m) and one value R2 from x=5500m to x=8500m (the lake).

4.2 Result

Figure 4.2 shows the more complex model. It can be seen that the till layer only covers a part of the aquifer. Figure 4.2 can be seen together with appendix 4.1 with show a number of wells projected on to the profile.

The results of the hydrological model can be seen in appendix 4.2, 4.3, 4.4 and 4.5. The chosen values of the variables Is

R1 3.35e‐9 m/s R2 6.88e‐9 m/s Km 1.95e‐8 m/s Ks 1.53e‐4 m/s

Variation of geological boundaries

-100

102030405060708090

0 1000 2000 3000 4000 5000 6000 7000 8000 9000

Distance in meter

Elev

atio

n in

met

er

Terrain

Top sand

Top clay

GWL

Figure 4.1: Physical boundaries between the geological layers. Complex model. Hydrological divide at x=0, Søbygaard Lake at x=8500

Variation of modell boundaries

-100

102030405060708090

0 1000 2000 3000 4000 5000 6000 7000 8000 9000

Distance in meter

Elev

atio

n in

met

er

Top

Boundary

Bottom

Figure 4.2: Physical boundaries of the groundwater mode. Complex model. Hydrological divide at x=0, Søbygaard Lake at x=8500

6

4.3 Discussion

This model represents a god estimate of the true geology, but there are still many uncertainties that influences on the model result, e.g. the presence of clay lenses within the aquifer. Given appendix 4.1, it is possible that a clay lens is situated at about x=3500m, but the well are situated quit fare from the profile and therefore not included in the model. The well‐logs can be seen in appendix 4.6.

Also the fact the little is known about the constants, makes it difficult to cerate a good model. It must be expected that ad least some of the constants is known.

5 Conclusions

It must be concluded that the models is quit uncertain, they are simply too simple. There is no evidence that the groundwater is flowing in a straight line from the saw mill to the lake, and the fact that some of the groundwater probably exfiltrate to the small stream at x=3500m makes the reliability of the model quit doubtful.

7

6 References DMU, 2003, Overvågning af effekten af retablerede vådområder, Teknisk anvisning fra DMU, nr. 19, 3. udgave, Danmarks Miljøundersøgelser, Miljøministeriet. Page 20. Jupiter net‐database, www.geo.dk, april 2006 FemLab 3, Comsol AB, Stockholm Sweden MapInfo 7.8, MapInfo Corporation, NY USA PC‐Jupiter, GEUS, Copenhagen Denmark Surfer 8, Golden Software inc., Colorado USA

Appendix 1 FemLab Tutorial

Step 1 Open FemLab

Open program, choose 2D mode and classical PDE / PDE coefficient form. Set application mode name to “H”, and pres OK.

Step 2 Draw model

To draw the physical boundaries of the model it is possible either to plot the coordinates directly, or create a grid and then use the curser to draw lines between the grid points.

To plot the coordinates choose <Draw/Specify objects/Line> (se above) In the line window write the coordinates for each line segment, choose style=closed polyline (solid). An example could be: X= “0 100 200 300 400 500 500 400 300 200 100 0 0” Y=”0 0 0 0 0 0 10 20 30 40 50 60 0”

0,0 100,0

500,10

500,0 400,0 300,0 200,0

0,60100,50

200,40300,30 400,20

To draw manually, set up a grid by choosing <Option/Axis Grid setting>

Enter the preferred spacing, and/or extra grid points, if needed. Choose the draw mode in the top toolbar, and choose the drawing tool in the draw‐toolbar.

Step 3 Setup constants

<Options/Constants>

Enter the needed constants

Step 4 Setup boundary conditions Enter the boundary mode in the top toolbar and click on the model

domain (sub domain), or choose <Physics/Boundary setting>

Choose the boundaries for which you want to set up.

For the upper boundaries with infiltration R, choose Neumann condition, q=0 g=R*ny (where R is the infiltration [m/s] and ny defines the normal vector on y) For the left boundary (hydrological divide) and the bottom boundaries (impermeable clay), choose g=0 (for 0 flux) and q=0 For right boundary (constant head) choose Dirichlet condition, with g=0 q=0 h=1 r=Hin (Hin being the head value at the boundary)

Step 5 Setup domain/sub-domain condition Enter the sub‐domain mode, and click the model domain, or choose <Physics/Subdomain settings>

Set c=K (for K being the hydraulic conductivity of the sub‐domain) and all other constants to 0

Step 6 Refine mesh Enter the mesh mode, and refine the mesh by clicking the refine mesh tab in the main toolbar (this gives a more accurate result, but the model run time will be longer)

Step 7 Post processing To visualize the results of the model, run the model after setting all the

perimeters (step 1 through step 6)

Enter the Post processing mode. Here there are 9 options to visualize the model results. 2D Surface plot 3D Surface plot Contour plot Arrow plot Streamline plot Boundary plot Animate Line and point cross section To setup the different plots, choose <Post processing/Plot perimeter> Here there are several options to optimize the plots. There is no need to describe the all, the best way to learn is to try and alter the perimeters and then see what happens to the plot.

It is though worth to mention the in order to get the right direction on the arrows in the arrow plot, a minus must be enter in front of ux and uy in the arrow data menu.

In order to get the stream lines to run through the whole of the model frame, set the maximum number of integration steps to a large amount (400000 or more) Choose <plot parameters/Streamline/Advanced>

Exercise

As an example on what to do wit this program, the following model shows what happens if e.g a pumping well is established in a groundwater aquifer. The main model is as described in this tutorial. By adding a sub‐domain to the main model, try to modify the model so it satisfies the following perimeters. The infiltration is 300 mm/year The hydraulic conductivity is 3.5e‐4 m/s The filter is 1*1 m, situated with center at (x,y)=(200;2) and the pumping rate is 0.0045 m3/hr

Appendix 2

Area map, of the Gjern river catchment. Blue dots indicating each end of the profile

Black dots indicating the location of the wells

1.5001.5001.5001.5001.5001.5001.5001.5001.500 3.0003.0003.0003.0003.0003.0003.0003.0003.000

metresmetresmetresmetresmetresmetresmetresmetresmetres

000000000

Appendix 3.1

FemLabThue Weel JensenScales in meter

Surfaceplot og hydraulic headsSimple model

Appendix 3.2


Flowlines of hydraulic movementSimple model

H(model) versus H(real) Simple model

0

10

20

30

40

50

60

70

80

90

0 1000 2000 3000 4000 5000 6000 7000 8000 9000 10000

meter

met

er

H(model)

H(real)

Terrain

Ap

pen

dix 3.3

Thu

e Weel Jen

sen

Appendix 4.1 Profile line showing the projected wells.

SØ DIV78.424

78.426

78.461

78.479

78.277

78.478

78.406 78.235

78.367

78.287 78.558

Clay-Till

Unspecified clay or tertiay-clay

Sand

Silt

2.000 m 6.000 m4.000 m 8.000 m0 m

0 m

20 m

40 m

60 m

80 m

100 m

Appendix 4.2


Surfaceplot og hydraulic headsComplex model

Appendix 4.3


Flowlines of hydraulic movementComplex model

Appendix 4.4


Comtours of hydraulic headComplex model

H(model) versus H(real) Complex model

0

10

20

30

40

50

60

70

80

90

0 1000 2000 3000 4000 5000 6000 7000 8000 9000 10000

meter

met

er

H(model)

H(real)

Terrain

Ap

pen

dix 4.5

Thu

e Weel Jen

sen

Appendix 4.6 Drill reports from the GEUS well‐database

Udskrevet 10/4 2006 Side 1

DGU arkivnr: 78. 406BORERAPPORT

Danmarks og Grønlands Geologiske Undersøgelse

Borested : HAMMEL DESTRUKTIONSANSTALT8450 Hammel

Kommune : HammelAmt : Århus

Boringsdato : 1/1 1961 Boringsdybde : 35 meter Terrænkote : 75 meter o. DNN

Brøndborer : MOB-nr : BB-journr : BB-bornr :

Prøver- modtaget : - beskrevet : - antal gemt :

af : B

Formål : Anvendelse : Boremetode :

Kortblad : 1215 IISØUTM-zone : 32UTM-koord. : 553560, 6233670

Datum : ED50Koordinatkilde : Koordinatmetode : Dig. på koor.bord

(seneste) 16,3 meter u.t. 1/1 1961Indtag 1Ro-vandstand Pejledato Ydelse Sænkning Pumpetid

l

s

s

0 (ler).

6 (sand).

17,3 (sand).

meter u.t.ø ukendt

0

5

10

15

20

25

f ortsættes..




s

meter u.t.

29Filter (i1)

35

25

30

35




Borested : HAMMEL,KURT CHRISTENSEN8450 Hammel


Boringsdato : 4/5 1973 Boringsdybde : 43,5 meter Terrænkote : 77 meter o. DNN



af : G




2,4 m³/t 5 meter(seneste) 9,3 meter u.t. 4/5 1973Indtag 1Ro-vandstand Pejledato Ydelse Sænkning Pumpetid

glg

lim

Dannelsesmiljøgl

Klimastratigraf iKronostratigraf i

l

g

gl

gs

0 (ler).

4,5 (grus, sand og grus).

12,5 (oligocæn-miocæn-pliocæn glimmerler, ler i vej.f j. f .).

20 (oligocæn-miocæn-pliocæn glimmersand, sand i vej.f j. f .).

meter u.t.ø254ø ukendt

24Filter (i1)

0

5

10

15

20

25

f ortsættes..




lim

mar

gs

gl27 (oligocæn-miocæn-pliocæn glimmerler, ler i vej.f j. f .).

meter u.t.

27

43,5

25

30

35

40

Aflejringsmiljø - Alder (klim a-, krono-, litho-, biostratigrafi)

m eter u.t.

0 - 4,5 glacigen - ant. glacial4,5 - 12,5 ant. glacial

12,5 - 36 limnisk - 36 - 42 limnisk - 42 - 43,5 marin -




Borested : VOLDBY,BYRIELSHOLM,ANDERS BYRIEL8450 Hammel





af : G




3 m³/t 30 meter(seneste) 6 meter u.t. 13/12 1965Indtag 1Ro-vandstand Pejledato Ydelse Sænkning Pumpetid

glgDannelsesmiljø

gl

Klimastratigraf i

ml0 (glacial moræneler (leret till)).


0

5

10

15

20

25

f ortsættes..




glg

f lv

glml

ds40 (glacial smeltevandssand).

meter u.t.

48Filter (i1)

51

25

30

35

40

45

50


m eter u.t.

0 - 40 glacigen - glacial40 - 51 fluvial - fluviatil - glacial




Borested : HAMMEL,ANDELSSVINESLAGTERIET8450 Hammel





af : G




70 m³/t 2,4 meter(seneste) 21,2 meter u.t. 1/1 1966Indtag 1Ro-vandstand Pejledato Ydelse Sænkning Pumpetid

glg

f lv

Dannelsesmiljøgl

Klimastratigraf i

ml

gl

ds

0 (glacial moræneler (leret till)).

7 (oligocæn-miocæn-pliocæn glimmerler, ler i vej.f j. f .).

9,5 (glacial smeltevandssand).


0

5

10

15

20

25

f ortsættes..




f lv glds

meter u.t.

41Filter (i1)

46

25

30

35

40

45


m eter u.t.

0 - 9,5 glacigen - glacial9,5 - 43 fluvial - fluviatil - glacial




Borested : VOLBY VANDVÆRK8450 Hammel



Brøndborer : Erik Mortensen, LundMOB-nr : BB-journr : BB-bornr :


Formål : Anvendelse : Ingen anvendelseBoremetode :



18 m³/t 1,5 meter(seneste) 7,8 meter u.t. 1/1 1962Indtag 1Ro-vandstand Pejledato Ydelse Sænkning Pumpetid

l

s

i

s

l

s

0 (ler).

1,6 (sand).

5,5 (silt klæg, meller).

7,8 (sand).

8,8 (ler).

13,4 (sand).


18,5Filter (i1)

23,5

0

5

10

15

20




Borested : Gården Fuglsang, Fuglsangvej 100, Fajstrup Krat8450 HammelRold Skov Savværk



Brøndborer : Holger Pedersen,SkjødMOB-nr : 16054BB-journr : BB-bornr :

Prøver- modtaget : 5/7 1984- beskrevet : 26/6 1985- antal gemt :

antal : 3af : PG

Formål : VandforsyningsboringAnvendelse : VandforsyningsboringBoremetode :

Kortblad : 1315IIISVUTM-zone : 32UTM-koord. : 557772, 6233114

Datum : ED50Koordinatkilde : AmtKoordinatmetode : GPSTørboring/slagboring

7,2 m³/t 3,5 meter 96 time(r)(seneste) -0,7 meter u.t. 1/3 1984Indtag 1Ro-vandstand Pejledato Ydelse Sænkning Pumpetid

Notater : Gruskastning nr. 4

glgDannelsesmiljø

gl


ml

l

0 LER, siltet, svagt gruset, gråbrun, kalkholdig, "moræneler".

2 LER, sandet, svagt gruset, gråbrun, kalkholdig, "moræneler".

4 LER, bbb opblanding af sand, bbb opblanding af sten. (ler).

6 SILT, svagt leret, sortbrun, glimmer-holdigt, kalkfri, "glimmersilt".

meter u.t.ø254ø160

4Gruskastning

1,2-1,8mmFilter (i1)

0,5mm6

6,5

0

5


m eter u.t.

0 - 4 glacigen - glacial4 - 66 - 6,5 limnisk -




Borested : Industrivej8450 HammelBor.3



Brøndborer : Holger Pedersen,SkjødMOB-nr : BB-journr : BB-bornr : 3

Prøver- modtaget : - beskrevet : 25/9 1977- antal gemt :

af : B

Formål : VandforsyningsboringAnvendelse : Boremetode :


Datum : ED50Koordinatkilde : Koordinatmetode : Dig. på koor.bordTørboring/slagboring

65 m³/t 3,8 meter 17 time(r)(seneste) 24,65 meter u.t. 25/9 1977Indtag 1Ro-vandstand Pejledato Ydelse Sænkning Pumpetid

Indtag 1 Tid: 30min Vsp: 24,65m

Tilbagepejling

l

s

0 LER, bb gul. (ler).

5 LER, bb blå. (ler).

9,5 SAND, bb rød. (sand).


Gruskastning 1,2-1,8mmFilter (i1)

0,8mm

0

5

10

15

20

f ortsættes..




s

24,65 SAND, bb rød. (sand).

31 SAND, bb grå. (sand).

meter u.t.

25

30

35

40

45

50

55

f ortsættes..




s

73 Boringen afsluttet i følgende bjergart : SAND, (sand).

meter u.t.

73

60

65

70




Borested : Tulip, Hammel8450 HammelBoring 2



Brøndborer : Holger Pedersen,SkjødMOB-nr : BB-journr : ZBB-bornr :


Formål : VandforsyningsboringAnvendelse : Ingen anvendelseBoremetode :



80 m³/t 2 meter 66 time(r)(seneste) 22 meter u.t. 1/8 1974Indtag 1Ro-vandstand Pejledato Ydelse Sænkning Pumpetid

l

l

l

s

s

0 (ler).

3,5 (ler).

7 (ler).

9,5 (sand).

22 (sand).

meter u.t.ø200

0

5

10

15

20

f ortsættes..




s

meter u.t.

51,5Gruskastning

1,2-1,8mmFilter (i1)

0,8mm

25

30

35

40

45

50

55

60

f ortsættes..




s

70 (sand).

meter u.t.

69,5

70,5

60

65

70




Borested : Vadestedvej 146, Hammel8450 Hammel


Boringsdato : 1/5 1976 Boringsdybde : 23,5 meter Terrænkote : 47,5 meter o. DNN

Brøndborer : Bent Kruse, VinderslevMOB-nr : BB-journr : BB-bornr :


Formål : VandforsyningsboringAnvendelse : Sløjfet/opgivet borBoremetode :


Datum : ED50Koordinatkilde : Koordinatmetode : Dig. på koor.bordTørboring/slagboring

39 m³/t 14 meter 28 time(r)(seneste) 4,5 meter u.t. 28/11 2005(første) 5 meter u.t. 1/5 1976

Indtag 1Ro-vandstand Pejledato Ydelse Sænkning Pumpetid

glg

f lv

mar

Dannelsesmiljøgl


ml

ml

ds

ol

0 LER, siltet, brun, kalkfri. (glacial moræneler (leret till)).

4 LER, siltet, brun, kalkholdig. (glacial moræneler (leret till)).

8 SAND, mest mellem, stærkt gruset, brun, kalkholdig. (glacial smeltevandssand).

22,5 LER, fedt, leret, brun, glaukonit-holdigt, svagt kalkholdig. (oligocæn ler).


18Filter (i1)

0,8mm

22,5

23,5

0

5

10

15

20

fortsættes..





m eter u.t.

0 - 8 glacigen - glacial8 - 22,5 fluvial - fluviatil - glacial

22,5 - 23,5 marin -




Borested : Frisenborg Vandværk8450 Hammel



Brøndborer : Holger Pedersen,SkjødMOB-nr : BB-journr : BB-bornr :


Formål : VandforsyningsboringAnvendelse : VandforsyningsboringBoremetode :



7 m³/t 9,8 meter 21 time(r)(seneste) 24,6 meter u.t. 1/10 1973Indtag 1Ro-vandstand Pejledato Ydelse Sænkning Pumpetid

glg

lim

Dannelsesmiljøgl


ml

ks

gi

0 LER, fedt, svagt leret, grå, kalkfri. (glacial moræneler (leret till)).

9 SAND, grå, kvarts-holdigt. (miocæn kvartssand).

23,5 SILT, f laserlejring, grå, glimmer-holdigt, kalkfri. (oligocæn-miocæn-pliocæn glimmersilt, silt i vej.f j. f .).

meter u.t.ø2000

Filter (i1) 0,3mm

0

5

10

15

20

25

f ortsættes..




limgi

gs

gl

36 SILT, sandet, grå, glimmer-holdigt, kalkfri. (oligocæn-miocæn-pliocæn glimmersand, sand i vej.f j. f .).

44 LER, fedt, siltet, glimmer-holdigt, kalkfri. (oligocæn-miocæn-pliocæn glimmerler, ler i vej.f j. f .).

meter u.t.

45

25

30

35

40

45


m eter u.t.

0 - 9 glacigen - glacial9 - 45 limnisk -




Borested : SALL,SKOVFOGEDHUSET,NIELSEN8450 Hammel





af : B




(seneste) 5,6 meter u.t. 12/2 1974Indtag 1Ro-vandstand Pejledato Ydelse Sænkning Pumpetid

l

s

0 (ler).

4,5 (sand).

meter u.t.ø ukendt

0

5

10

15

20

25

f ortsættes..




s

meter u.t.

32,4Filter (i1)

39

25

30

35

Documents

Groundwater modelling, exercise 2. - mr2ue.dk · Groundwater modelling, exercise 2. ... Surfer 8, Golden Software inc., Colorado USA. ... The main model is as described in this tutorial