Rainfall patterns associated with runoff and erosion levels in West-Siberian Chernozems

Аннотация

The aim of the study was to identify 1) the main regularities of surface runoff formation due to downpours and 2) the extent of erosion process on arable chernozems in areas with dissected relief and sharply continental climate. The influence of rainfall patterns and soil physical factors on soil erosion was studied in three large geomorphological regions in the South-East of West Siberia. Field observations were carried out during 1968–1979 in the Kuznetsk Depression and in 1984–1986 in the Near-Ob areas, and from 1995 until present in the Near-Salair area. The data of meteorological stations were analyzed for rainfall patterns in the same years, including inter-year variability and downpour recordings. Summer precipitation and its intensity were measured by using hydrograph unit. Water infiltration in the field was studied by the method of small flooded areas (Nesterov’s method), when square or round frames with an area of 2500 (external) and 625 cm² (internal) were installed on the soil surface. To simplify and automate water supply, the PVN-00 device was used, consisting of two hermetically sealed tanks, two cylindrical frames of different diameters and a tripod. The influence of rainfall patterns and soil physical factors on the processes of soil erosion was studied. As regards climatic factors the data of meteorological stations were analyzed for historical rainfall patterns, including interannual variability and downpour recordings. Experimental data of water infiltration, runoff and soil loss were discussed for the main soils units: Greyzemic Phaeozems (Siltic), Luvic Chernozems (Siltic) and Haplic Chernozems (Siltic) with variable content of soil organic matter and erosion levels. The studied regions were characterized by the prevalence of precipitation during the warm growing season and by sporadic or cyclical precipitation patterns. Heavy rains were found to cause significant damage to agricultural land only locally, during early spring, when the soil is not protected by vegetation. The greatest erosion hazard is represented by meltwater, not only by its total amount, but also by the snow thawing rate. The significant decrease in the infiltration rates with extensive farming is the main factor of degradation of the most fertile soils in West Siberia. Soil vulnerability to erosion in the studied area was shown to decrease in the range: Kuznetsk Depression > Near-Salair > Near-Ob (no storm damage).