Active layer depth as a key factor of runoff formation in permafrost: process analysis and modelling using the data of long-tem observations

Lyudmila Lebedeva1,2, Olga Semenova2,3

1St.Petersburg State University2Hydrograph Model Research Group

3State Hydrological Institute, St. Petersburg, Russia

Objectives

1. Establishment of observations database for the period

1948 – 1990

2. To analyze the patterns of distribution of active layer

depth in different landscapes

3. To assess the main factors determining active layer depth

4. To estimate physical properties of the soil strata and

simulate the process of soil freezing and thawing in

different landscapes

5. To simulate runoff using the same set of parameters as in

active layer depth modelling

Fig.1. Sketch of the KWBS

Study area

Kolyma water-balance station (KWBS)Kolyma water-balance station (KWBS) – small research watershed (22 km2) in the

upper Kolyma river; observations since 1948

Watershed boundaries

Meteorological Station

Rain gauge

Recording rain gauge

Pit gauge

Snow survey line

Cryopedometer

Evaporation plot

Pan evaporation plot

Snow evaporation plot

Water balance plot

• Mean annual temperature

– -11,60C

• Precipitation – 314

mm/year

• Open wood, bare rocks

• Continuous permafrost

• High-mountain relief

• Representative for the

North-East of Russia

KWBS instrumentation

Measured parametersObservation

periodTemporalresolution

Number ofstations

Stream flow 1948–cont.MinuteDaily

7

Meteorological observations

1948–cont. 3h 1

Precipitation 1948–cont.

MinutePentad, decade in winter, daily in summer

DecadeMonth

105

1010

Snow surveys 1948–cont. Monthly (October – March), decadely (April…) 5

Evapotranspiration 1958–cont. Pentade 4

Snow evaporation 1958–cont. September – October, March – April (12-hourly) 1

Pan evaporation 1970–cont. Decade 1

Energy balance 1958–cont. Decade 1

Soil freezing/thawing 1958–cont. Once in 5 days 5

Soil temperature at depths 0.1 – 3.2 m

1974–1981 Daily 1

Flow water chemistry 1958–cont. Event based 2

Hydrograph Model

RR• Deterministic distributed model of runoff formation processes

• Single model structure for watersheds of any scale

• Adequacy to natural processes while looking for the simplest solutions

• Minimum of manual calibration

• Forcing data: precipitation, temperature, relative humidity• Output results: runoff, soil and snow state variablessoil and snow state variables, full

water balance

Landscapes

Legendoutlet

stream

rock debris

swamp forest

open wood

The landscapes vary with altitude

from stone debris to swamp forest

Fig.2. The main landscapes of KWBS

Active layer depth in different landscapes

Upper Upper part of part of the slope:the slope:

LowerLowerpart of part of the slope:the slope:

clay slate

•rock debrisrock debris•absence of vegetationabsence of vegetation

•peaty groundpeaty ground•swamp larch forestswamp larch forest

Soil propertiesThe main parameters for simulation soil thawing and freezing processes in the Hydrograph model are physical soil properties

Porosity, %

Field capacity,%

Heat capacity,

J/m3*K

Heat conductivity,

W/m*K

Peat 80 50 1920 0.8

Clay slate 50 40 750 2.3

Crushed

stone55 30 810 1.7

Crumbling

rock55 13 790 2

Slope aspect

Slope aspect in mountain relief of KWBS controls both landscape and active layer depth because of different solar radiation income

Fig.4. Direct solar radiation income during the year for

north-and south-facing slopes

Legendoutlet

stream

rock debris

swamp forest

open wood

Fig.2. The main landscapes of KWBS

Fig.3. Domination of north- and south-facing slopes within KWBS

Northern aspect

Southern aspect

Active layer depth modelling

Site 1 (subcatchment Site 1 (subcatchment Severny):Severny):

•South-facing slope•Absence of vegetation•Rock debris•Active layer depth up to

1.7 m

Calculated Observed

03.8412.8309.8306.8303.8312.8209.8206.8203.82

m

1.8

1.6

1.4

1.2

1

0.8

0.6

0.4

0.2

0

Calculated Observed

03.7912.7809.7806.7803.7812.7709.7706.7703.77

m

1.8

1.6

1.4

1.2

1

0.8

0.6

0.4

0.2

0

m

Site 2 (subcatchment Site 2 (subcatchment Yuzhny):Yuzhny):

•North-facing slope•Sphagnum, shrubs•Soil profile – peat, clay

loam, clay slate•Active layer depth up to

0.7 m

Fig.5. Observed and calculated active layer depth in two landscapes, KWBS

Runoff modelling – slope scale

Subcatchment Severny:Subcatchment Severny:•0.41 km2

•South-facing slope•Sparse vegetation•Thin soils and rock debris

Subcatchment Yuzhny:Subcatchment Yuzhny:•0.27 km2

•North-facing slope•Moss, shrubs, open wood•Soil profile – peat, clay loam, clay slate

Fig.7. Observed and simulated runoff, Severny, 1981–1982

observed simulated

11.198109.198107.198105.1981

m3/s

0.10

0.08

0.06

0.04

0.02

0.00

observed simulated

10.198208.198206.1982

m3/s

0.10

0.08

0.06

0.04

0.02

0.00

simulated observed

10.198108.198106.1981

m3/s

0.10

0.08

0.06

0.04

0.02

0.00

simulated observed

10.198208.198206.1982

m3/s

0.10

0.08

0.06

0.04

0.02

0.00

Fig.8. Observed and simulated runoff, Yuzhny, 1981–1982

observed simulated

09.197608.197607.197606.1976

m3/s

6

4

2

0

Runoff modelling at the Kontaktovy watershed (21,7 km2)

Legendoutlet

stream

rock debris

swamp forest

open wood

Different slope aspects, soil and vegetation were combined into 3 runoff formation complexes (RFC)For each RFC the set of parameters verified against active layer depth and runoff in subcatchments was used

observed simulated

09.197508.197507.197506.1975

m3/s

6

4

2

0

observed simulated

10.197709.197708.197707.197706.1977

m3/s

6

4

2

0

observed simulated

09.197808.197807.197806.1978

m3/s

6

4

2

0

Conclusions

1. Active layer depth has high variability and is determined mainly by landscape

2. The landscapes vary consecutively from stone debris with no vegetation in the top of the slope to swamp forest next to the stream body

3. The main parameters for computing water and heat dynamic in soils are its physical properties

4. Long-term observations accompanied with description of soil and vegetation properties may serve as a base for reliable estimation of the model parameters which can be transferred to the basins with limited data

Acknowledgements

This study was conducted within the research grant provided by Russian-German Otto-Schmidt Laboratory for Polar and Marine research in 2010

The attendance to EGU 2011 was made possible with additional support of Russian-German Otto-Schmidt Laboratory for Polar and Marine research

Hydrograph Model Research Group

www.hydrograph-model.ru

More results in the Canadian discontinuous permafrost environment on…

Thu, 07 Apr, 11:30–11:45, Room 38EGU2011-4813

“Parameterisation by combination of different levels of process-based model physical complexity”

by Pomeroy, Semenova, Lebedeva and Fang

Thank you for attention!