ESTIMATING THE SATURATED HYDRAULIC CONDUCTIVITY OF A SOIL

CONTAINING STONES

Novák V., Kňava, K. Institute of Hydrology, Slovak Academy of Sciences,

Bratislava, Slovakia

Slovakia, A = 49 019 km sq, Af = 0.41

High Tatras stony soils

-Many mountaineous soils contain rock fragments (gravelly, stony soils), more than 2 mm in diameter

-Most of forest soils over Slovakia are stony soils

-Majority of published soil characteristics (physical, hydrophysical) are estimated for fine earth fraction (less than 2 mm in diameter)

FIRE 2005

2007

2008

2009

EX NEXIF

.lokality vybrané

v

súčinnosti s

TANAP-om

_IF(INTACT FOREST)

–

Vyšné

Hágy

_EX(EXTRACTED FOREST)

–

Danielov dom

_NEX(NON-EXTRACTED-FOREST)

–

Tatranská

Lomnica /Jamy/

_FIRE(ZHORENISKO)

–

Nový Smokovec –

Tatranské

Zruby

2005

2009

Measuring stoniness

Measuring stoniness

-70.00

-60.00

-50.00

-40.00

-30.00

-20.00

-10.00

0.00 0.00 0.10 0.20 0.30 0.40 0.50

Pc

z c

m

Site FIRE, High Tatras

-100

-80

-60

-40

-20

0 0 0.5 1

nr

z c

m Pores Stones Soil particles

Site FIRE, High Tatras

Darcy´s law

v

–

“macroscopic”

flow rate , m s1

K –

saturated hydraulic

conductivity of the soil, m s1

L

–

length of the soil sample, m Δh –

the difference between the water levels at the both ends of the soil column, m

L hKv Δ=

vK h

L h

LvK =→= Δ

→ Δ

= 1

1290.31

670.30

277.10

321.28

181.06

1002.78

238.76

991.69

0 200 400 600 800 1000 1200 1400

1

K cm.d-1

44

160

54

20

19

50

46/45

MK/30

0 - 5

c m

10 -

15 c

m 40

- 45

c m

Vertical distribution of saturated hydraulic conductivity of soil matrix K, measured on soil samples. Site Fire, H. Tatras.

Numerical experiment-

alternative method of K stony soils estimation

•

Representative elementary volume (REV) of stony soils is too big to be sampled and processed

•

Numerical experiment (simulation of Darcy´s test) is good alternative to estimate K

•

Two dimensional simulation model HYDRUS -2D was used

Darcy´s test •

Volume of the REV is 1 cubic meter

•

Cross section of the 2D simulation stony soil is 1 square meter

•

Soil contains stones of 10 cm in diameter of given relative volume (area)

•

Soil matrix is saturated with water, stones are non-conductive for water

•

Unite hydraulic gradient is applied; the top and bottom of the REV is ponded with 10 mm of water

Water content for relative stone content 0.1

red-

saturated soil

Velocity for relative stone content 0.1 Red-high velocity Blue-low velocity

Water potential

for relative stone content 0.1 Red-positive pressure Blue-negative

Rv_01_1_waterCONTENT.jpg

Water content for relative stone content 0.1

Velocity Rv

=0.1

Water potential Rv

=0.1

Water content for relative stone content 0.2

Velocity

Rv

=0.2

Water potential

Rv

=0.2

Water content for relative stone content 0.2

Velocity

Rv

=0.2

Water potential

Rv

=0.2

Water content for relative stone content 0.3

Velocity

Rv

=0.3

Water potential

Rv

=0.3

Water content for relative stone content 0.3

Velocity

Rv

=0.3

Water potential

Rv

=0.3

Saturated hydraulic conductivities of soils K with different volumetric stone content Rv

0.001

0.01

0.1

1

0 0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4 Rv

K c

m .m

in- 1

1

2

3

4

Cumulative water infiltration into stony soil with different stones content: Rv = 0, (1); Rv = 0.1, (2); Rv = 0.2, (3);

Rv = 0.3, (4);

Rv = 0.4,(5).

Loamy sand, FIRE site, High Tatras, Slovakia.

Cumulative Infiltration

0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 6.0 6.5 7.0

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 t (min)

I (c

m )

1

2

3

4

5

0 - 100 cm

21.5

22.5

23.5

24.5

25.5

26.5

27.5

28.5

29.5

30.5

31.5

32.5 1 7 13 19 25 31 37 43 49 55 61 67 73 79 85 91 97 10 3

10 9

11 5

12 1

12 7

13 3

13 9

14 5

15 1

15 7

16 3

16 9

17 5

18 1

18 7

19 3

19 9

20 5

21 1

time, d

W at

er c

on te

nt , c

m

LAI 6 LAI 3 LAI 1.5

Závery Hydraulické

vodivosti vodou nasýteného pórovitého prostredia (pôdy)

K sa znižujú

so zvyšujúcim pomerným objemom kameňov Rv nelineárne a

ich hodnoty sú

nižšie, ako vypočítané

lineárnou

závislosťou K = 1 -

Rv . Závislosť

medzi relatívnou nasýtenou hydraulickou vodivosťou

a

relatívnym obsahom skeletu Kr = f(Rv ) je vhodné

vyjadriť lineárnou rovnicou typu Kr = 1- a Rv (rov.7),

súčiniteľ

a sa

pohyboval v

rozmedzí

1.1 < a < 1.32 pre kamene guľového tvaru s

priemerom 10 cm.

Relatívne hydraulické

vodivosti Kr pri danom pomernom obsahu kameňov Rv sa znižujú

so znižujúcou sa nasýtenou hydraulickou

vodivosťou pôdnej matrice a

so zvyšovaním sa veľkosti dispergovaných kameňov.

Preliminary conclusion 1

Hydraulic

conductivity of porous media containing stones and saturated with water (soil)

K decrease

with

increasing relative stone content (stoniness)

Rv ; values of K are below linear relationship K = 1 -

Rv .

Preliminary conclusions 2

•

Relationship between relative saturated hydraulic conductivity Kr and stoniness Rv -

Kr = f(Rv ) can be expressed by linear –

type

equation

Kr = 1- a Rv ), coefficient

a was found in the range 1.1 < a < 1.32 for spherical stones of 10 cm

in diameter

Preliminary conclusions 3

Relative hydraulic conductivities

Kr for constant Rv are decresing with decresing saturated hydraulic conductivity of matrix Km , with diameter of stones and with unregularity in shape, size and distribution of stones.

ESTIMATING THE SATURATED HYDRAULIC CONDUCTIVITY OF A SOIL CONTAINING STONES Foliennummer 2 Foliennummer 3 High Tatras stony soils Foliennummer 5 Foliennummer 6 Foliennummer 7 Foliennummer 8 Foliennummer 9 Foliennummer 10 Foliennummer 11 Foliennummer 12 Foliennummer 13 Foliennummer 14 Darcy´s law Foliennummer 16 Numerical experiment- alternative method of K stony soils estimation Darcy´s test Water content for relative stone content 0.1�red- saturated soil Velocity � Foliennummer 22 Foliennummer 23 Foliennummer 24 Foliennummer 25 Foliennummer 26 Foliennummer 27 Foliennummer 28 Foliennummer 29 Foliennummer 30 Foliennummer 31 Foliennummer 32 Foliennummer 33 Foliennummer 34 Foliennummer 35 Foliennummer 36 Saturated hydraulic conductivities of soils K with different volumetric stone content Rv Cumulative water infiltration into stony soil with different stones content: Rv = 0, (1); Rv = 0.1, (2); Rv = 0.2, (3); Rv = 0.3, (4); Rv = 0.4,(5). Loamy sand, FIRE site, High Tatras, Slovakia.� Foliennummer 39 Závery Preliminary conclusion 1 Preliminary conclusions 2 Preliminary conclusions 3