Assessment of soil loss by water erosion in small river basins in Russia

Abstract

© 2020 Elsevier B.V. Prolonged and intensive agricultural exploitation in the European territory of Russia has resulted in extensive soil erosion, which has led to anthropogenically induced degradation of arable land. The extensive agricultural development of the region stems from the presence of plains suitable for plowing, which feature fertile chernozem (Luvic Chernozems) and grey forest (Luvisols) soils. The majority of the land in the small river basins (70–80%) are plowed. In addition, this macroregion of Russia is the main agricultural territory that provides food for the entire country. The total arable area comprises approximately 600,000 km2. Approximately 95 million people, the majority of the population of Russia, live in this region. This research aims to provide a quantitative assessment of the soil lost by erosion in the arable lands of the macroregion using an USLE empirical mathematical model modified to suit the harsh climatic conditions of Russia. The calculation was performed using a raster model of the data that includes a model of the slope angle, slope length, soil erodibility, rainfall erosivity factor, water content of the snow, annual distribution of precipitation, and types of land use. The location of arable lands of the territory were determined by remote sensing measurements and the TerraNorteRLCv.3 (2014) map compiled by the Space Research Institute of the Russian Academy of Science. For the first time, the intensity of soil erosion over periods of snowmelt and storm runoff, as well as the total annual soil loss, were determined for this territory at a regional scale (1:500,000). The results of these calculations were generalized for small river basins. For this generalization, we used a grid we had previously designed that features over 50,000 river basins. The average soil erosion in the territory studied amounts to 4.04 t ha−1 year−1, considering the soil-protective coefficients of agricultural vegetation. In the annual soil loss by erosion, storm runoff erosion prevails at 3.78 t ha−1 year−1 and the erosion by snowmelt is considerably lower at only 0.26 t ha−1 year−1. As expected, due to the higher values of the relief (length-slope) factor, soil erosion increases from the lowland plains (3.65 t ha−1 year−1) to the high plains (5.38 t ha−1 year−1), peaking in the mountains (12.88 t ha−1 year−1). The rate of soil erosion of arable lands consistently decreases from the taiga and forest landscape subzone to the steppes. An east–west trending zone featuring the highest soil erosion was distinguished. This zone of high soil erosion coincides with the mixed and broad-leaved forests subzone, which is highly used for plowing. Moreover, a western longitudinal sector of high soil erosion that includes the forest and forest-steppe landscape zones was also determined.