Coupled modelling of soil thaw/freeze dynamics and runoff generation in permafrost landscapes, Upper Kolyma, Russia Lebedeva L.1,4, Semenova O.2,3 1Nansen Environmental and Remote Sensing Centre 2Gidrotehproekt Ltd 3St. Petersburg State University 4State Hydrological Institute St. Petersburg, Russia The study is partially supported by Russian-German Otto Schmidt Laboratory for Polar and Marine research

Variety of landscapes and complex process interactions Bare rocks Bush tundra Deep active layer Subsurface runoff Shallow active layer, surface runoff Larch forest Riparian vegetation www.hydrograph-model.ru

Motivation Objectives variety of landscapes and dominated flow formation mechanisms sparse hydrometeorological network in North-Eastern Russia and nearly absence of research stations observed environmental changes impact differently in diverse landscapes - analysis of active layer formation and flow generation mechanisms in mountainous permafrost landscapes of the Kolyma Water Balance Station (North-Eastern Russia) - simulate thaw/freeze depths and runoff in homogenious landscape typical for North-Eastern Russia using the Hydrograph model - develop and verify unified approach for hydrological modelling in changing permafrost environments of North-East of Russia Objectives

Study area: Kolyma water-balance station Creek Area, km2 Average (and maximum) elevation, m Average (and maximum) slope, º Area occupied by a certain landscape, % Rocky talus Mountain tundra Sparse trees Forest and bogs Morozova 0.63 1370 (1700) 33 (50) 98 2 Severny 0.33 1020 (1300) 21 (40) 24 63 13 Yuzhny 0.27 985 (1100) 17 (30) 5 17 56 22 Kontaktovy 21.2 1070 (1700) 25 (50) 34 27 12 Mean air temperature is -11,40С Mean annual precipitation 320 mm Elevation ranges 800-1700 m Variety of landscapes Continuous permafrost with the thickness up to 400 m Representative for the vast territories of Upper Kolyma River Basin

List of measurements conducted at KWBS

Scheme of the typical landscapes Bare rocks Bush tundra Sparse forest Larch forest

initially developed by Prof. Yury Vinogradov The Hydrograph model Process-based (explicitly includes all processes) Observable parameters, no calibration (can be obtained apriori) Common input daily data (air temperature and moisture, precipitation) Free of scale problem (from soil column to large basin) initially developed by Prof. Yury Vinogradov www.hydrograph-model.ru

Physical ground properties that drive the processes of active layer formation Moss and lichen Peat Clay with inclusion of rocks Bedrock Density, kg/m3 500 1720 2610 Porosity, % 90 80 55 35 Water holding capacity, % 60 20-40 13 7 Infiltration coefficient, mm/min 10 0.0005-0.5 0.0005 0.05-1 Heat capacity, J/(kg oC) 1930 840 750 Heat conductivity, W/(m oC) 0.8 1.2 1.5 Wilting point, % 8 6-8 4 2-3 www.hydrograph-model.ru

Soil thaw/freeze processes and runoff formation Type 1 – peaty soils and surface flow Peaty soil is fully saturated with ice during snow melt. It thaws slowly and surface flow occurs. observed runoff simulated runoff snow water equivalent infiltration into soil surface flow observed soil thaw depth simulated soil thaw depth

Soil thaw/freeze processes and runoff formation Type 2 – rocky stratum and subsurface flow Snowmelt water is re-frozen in soil. Only subsurface flow is formed. liquid water content in soil ice content in soil simulated soil thaw depth observed runoff simulated runoff snow water equivalent

flow dependence on air temperature Stages of the soil thawing and spring flow formation (Bantsekina, 2003) flow dependence on air temperature Data of ice content in the rocky stratum don’t exist. According to literature each year in freshet period 40-60 mm ground ice are formed. Modelling results for 1969-1990 show 21-48 mm.

Observed and simulated thawing depths in bare rocks, bush tundra and larch forest, 1962

Runoff modelling at slope scale Yuzny Creek, area 0.27 km2 , sparse forest 1980: NS = 0.74 Severny Creek, area 0.33 km2, bush tundra 1978: NS = 0.86 1 – observed runoff, 2 – simulated runoff, 3 - precipitation www.hydrograph-model.ru

Runoff modelling at slope and small scale Morozova Creek area 0.63 km2, bare rocks 1979: NS = 0.79 Kontaktovy Creek, 21.2 km2, 1978, m3/s 1978: NS = 0.85 Landscape distribution: Bare rock – 32 % Bush tundra – 29 % Sparse forest – 21 % Larch forest – 18 % 1 – observed runoff, 2 – simulated runoff, 3 - precipitation

Conclusions www.hydrograph-model.ru Hydrograph model proved its capability to successfully describe soil thawing and freezing, water and ice dynamics in rocky stratum in diverse landscapes based on relatively simple algorithms and observable parameters. Good agreement between observed and simulated active layer depth and runoff is achieved for small watersheds of the KWBS Developed set of model parameters which are systematized according to main landscapes of the Upper Kolyma River basin might be transferred to other basins without specific observations www.hydrograph-model.ru Semenova O., Lebedeva L., Vinogradov Yu., 2013 Simulation of subsurface heat and water dynamics, and runoff generation in mountainous permafrost conditions, in the Upper Kolyma River basin, Russia. Hydrogeology Journal vol. 21, iss. 1, 107 – 119. DOI:10.1007/s10040-012-0936-1 www.hydrograph-model.ru

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