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

0.000.00 0.10 0.20 0.30 0.40 0.50

Pc

z c

m

Site FIRE, High Tatras

-100

-80

-60

-40

-20

00 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, mΔh –

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

LhKv Δ

=

vKh

Lh

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

cm

10 -

15 c

m40

- 45

cm

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

Velocityfor relative stone content 0.1Red-high velocityBlue-low velocity

Water potential

for relative stone content 0.1Red-positive pressureBlue-negative

Rv_01_1_waterCONTENT.jpg

Water content for relative stone content 0.1

VelocityRv

=0.1

Water potentialRv

=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 0.4Rv

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

0.00.51.01.52.02.53.03.54.04.55.05.56.06.57.0

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

32.51 7 13 19 25 31 37 43 49 55 61 67 73 79 85 91 97 103

109

115

121

127

133

139

145

151

157

163

169

175

181

187

193

199

205

211

time, d

Wat

er c

onte

nt, c

m

LAI 6 LAI 3 LAI 1.5

ZáveryHydraulické

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.