Active layer depth as a key factor of runoff formation in permafrost: process analysis and modelling...
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Transcript of Active layer depth as a key factor of runoff formation in permafrost: process analysis and modelling...
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!