Количественная оценка эрозионных потерь почвы на различных участках распахиваемого склона (бассейн Верхней Oки)

Abstract

The paper presents the results of detailed erosional study of soil loss observed during the post-Chernobyl period. Radiocaesium method was applied in the experimental area located in Oryol district of the Oryol region (Upper Oka basin). The humidification conditions analysis was conducted for recent decades (2021–2022), an increase in the groundwater supply of rivers and lakes was observed. It was found that intense April precipitation has a strong erosional impact onto the soil cover, despite the decrease in the volume of meltwater in recent years. The analysis of temperature conditions confirmed the warming of the winter season in the last decade and in 2022, erosional potential of meltwater has almost halved. Intense precipitation in September and October of 2021, a warm winter and intense rains in April 2022 caused intensive soil washing in spring. The inter-aggregate adhesion is disrupted in the soil after freezing and consequent thawing, so the intense spring precipitation forms a soil washout. Soil runoff in the studied area is carried out by a complex system of furrows and erosional ravines. The article describes the main approaches applied to develop a semi-empirical methodology for erosional soil loss estimation, and the equations obtained on its basis for six zones of studied area differing in the structure of the surface. The methodology is based upon the in-situ data collected by authors in 2014–2017. The dependences of caesium-137 specific activity on morphometric variables (namely catchment area and profile curvature) are estimated. The reference value of caesium-137 specific activity was establish reducing the results of layer-by-layer in-depth measurements within three block elevations on the watershed. The equations used for the calculation of soil runoff amount were applied to produce a grid map of the soil runoff intensity for the sloping surface of the southern exposure. Estimation of the soil runoff (provided under the conditions of 25 cm arable layer depth and 1110 g/m³ soil material density) shows that in the studied area of gray forest heavy loam soils, the soil runoff value varies from 5 t/ha/year to more than 20 t/ha/year. The proposed methodology can be refined by enlarging the (spatial) scale of research.