Poster runoff processes

Integrated Water Resources Management in Central Asia:
Model Region Mongolia (MoMo)
www.iwrm-momo.de
Runoff generating processes in the forest-steppe ecotone
of the Khentii Mountains in northern Mongolia
KOPP J. BENJAMIN1, BENTS MATTHIAS2, LANGE JENS2, MENZEL LUCAS1
1Institute
of Geography / Department of Physiogeography, University of Heidelberg
2Institute of Hydrology, University of Freiburg
In this study about regional hydrology, which is part of the IWRM Project „Integrated Water Resources Management in Central Asia: Model Region Mongolia
(MoMo)“, we investigate hydrological processes in a headwater area of the Kharaa River. The aims of this study are the identification and quantification of
relevant runoff generating processes in the forest-steppe ecotone which remained mostly uninfluenced by direct human activities. In this region,
characterized by permafrost free, steppe vegetated south-exposed slopes and permafrost underlain, taiga vegetated north-exposed slopes, the hydrological
behaviour differs fundamentally. Forest fires, both natural and human induced, occasionally occur during dry periods and have the capability to change the
hydrological system immediately and on the long-term.
North-exposed pristine taiga
Figure 1: Pristine taiga forest during the summer
months.
North-exposed burned taiga
Figure 2: Hillslope runoff in the pristine
taiga during the summer months.
Figure 5: Burned taiga forest during the summer
months.
Figure 6: Hillslope runoff in the burned
taiga during the summer months.
• Vital trees, vital organic surface cover (0.15 ± 0.04 m)
• Dead trees, mostly dead organic surface cover (0.03 ± 0.02 m)
• Insulation of the soils (albedo↑, shadowing↑, thermal conductivity↓)
• Soil warming (albedo↓, shadowing↓, thermal conductivity ↑)
• Permafrost in shallow depths
• Permafrost degrades to deeper depths
• Cold, moist soils, evapotranspiration by trees and organic surface cover (1)
• Warm, very moist soils, small evapotranspiration following forest fire (1)
• Good storage function → slope runoff was observed only after
a relativly high increase of the soil mositure
• Loss of the storage function → slope runoff was observed almost
immediately after precipitation input
Figure 3: Water temperature (°C), water level (level) und relative increase of the soil moisture (d SM)
following selected precipitation events in the pristine taiga.
Figure 7: Water temperature (°C), water level (level) und relative increase of the soil moisture (d SM)
following selected precipitation events in the burned taiga.
• Flowpaths are controlled by the position of the permafrost
• Relocation of the flowpaths after the degradation of the permafrost (2)
→ mainly as matrixflow in the organic
surface cover and as pipeflow in the
interface between surface cover and
the mineral horizon (2)
→ partly as matrixflow in the mineral
horizon (2)
h
Figure 4: Schematic flowpaths in the pristine
taiga, visualized with brilliant blue.
high fraction of event-water with
high water temperature
Literature
South-exposed steppe
• dry, warm and silty soils
• High rates of evapotranspiration (3)
• Very low surface infiltration rates (1)
• Surface runoff during precipitation
events with high intensities; surface
runoff fraction of stormflow is up to
70% at the beginning of the event
31% of the total event
Figure 8: Schematic flowpaths in the burned
taiga, visualized with brilliant blue.
→ partly as pipeflow between the dead
organic cover and the mineral
horizon
→ mainly along an effective network
of deep flowpaths above the
permafrost
cold pre-event water is replaced by
event water characterized by higher
temperatures
Figure 9: Two component hydrograph
separation using δ2H.
• (1) Kopp JB., Menzel L., Minderlein S. (in preparation). Effect of exposition,
vegetation and wildfire on soil moisture distribution in a mountainous headwater
area in the discontinous permafrost zone of northern Mongolia.
• (2) Kopp JB., Lange J., Bents M., Menzel L. (in preparation). Effects of wildfire on
summer runoff processes in a mountainous headwater area in the discontinous
permafrost zone of northern Mongolia.
• (3) Minderlein S., Menzel L. (in preparation). Evaporation and energy balance
dynamics of a grassland and shrubland in a semi-arid forest-steppe ecotone,
northern Mongolia.
Contact:
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