Principal Denudation Processes and Their Contribution to Fluvial Suspended Sediment Yields in the Upper Yangtze River Basin and Volga River Basin

This paper synthesized the principal land denudation processes and their role in determining riverine suspended sediment yields(SSY) in two typical geographical environments of the Upper Yangtze River Basin in China and the Volga River Basin in Eastern Europe. In the Upper Yangtze River Basin, natural factors including topography, climate,lithology and tectonic activity are responsible for the spatial variation in the magnitude of denudation rates.Human disturbances have contributed to the temporal changes of soil erosion and fluvial SSY during the past decades. On one hand, land use change caused by deforestation and land reclamation has played an important role in the acceleration of sediment production from the central hilly area and lower Jinsha catchment; On the other hand, diverse soil conservation practices(e.g., reforestation,terracing) have contributed to a reduction of soil erosion and sediment production since the late 1980 s.It was difficult to explicitly decouple the effect of mitigation measures in the Lower Jinsha River Basindue to the complexity associated with sediment redistribution within river channels(active channel migration and significant sedimentation). The whole basin can be subdivided into seven sub-regions according to the different proportional inputs of principal denudation processes to riverine SSY. In the Volga River Basin, anthropogenic sheet, rill and gully erosion are the predominant denudation processes in the southern region, while channel bank and bed erosion constitutes the main source of riverine suspended sediment flux in the northern part of the basin. Distribution of cultivated lands significantly determined the intensity of denudation processes.Local relief characteristics also considerably influence soil erosion rates and SSY in the southern Volga River Basin. Lithology, soil cover and climate conditions determined the spatial distribution of sheet, rill and gully erosion intensity, but they play a secondary role in SSY spatial variation.

Soil erosion: An important indicator for the assessment of land degradation neutrality in Russia

This review of soil erosion(SE)studies in Russia focuses on two main tasks:(i)ensuring the completeness and reliability of SE data in Russia,a large country(17.1 million km2)with a variety of natural and socio-economic causes of land degradation,(ii)assessing the possibility of including a SE indicator among the indicators of land degradation neutrality(LDN).A wide range of statistical,remote sensing,mathematical modeling data.the results of scientific and field studies obtained at different levels were analyzed.It is asserted that in Russia the total area of eroded lands and those under erosion risk occupy more than 50%of all agricultural lands,whereas soil fertility of croplands decreased in Soviet time(from 1950s to 1980s)by 30-60%only due to water erosion.However,recent scientific studies indicate a decrease in erosion rate and in the area of eroded land during the last 30-40 years as a result of abandonment of arable land and subsequent overgrown with natural vegetation.The climate change resulting in decrease of the depth of soil freezing,flow of spring runoff also adds to the decrease of soil erosion.The SE indicator was suggested as an important complement to three global LDN indicators.At national and subnational level,it can be interpreted through such indices as"Rate of soil loss"(ton ha-1 yr-1)and"Total soil loss"(1000 tons,in certain area during selected time period).At local level the set of indices can be wider and site-specific,including those obtained through remote sensing data by using the classifier of thematic applications of remote sensing technologies;the example was tested at the local site.

The history and assessment of effectiveness of soil erosion control measures deployed in Russia

Research activities aimed at design and application of soil conservation measures for reduction of soil losses from cultivated fields started in Russia in the last quarter of the 19th century.A network of"zonal agrofor-estry melioration experimental stations"was organized in the different landscape zones of Russia in the first half of the 20th century.The main task of the experiments was to develop effective soil conservation measures for Russian climatic,soil and land use conditions.The most widespread and large-scale introduction of coun-termeasures to cope with soil erosion by water and wind into agricultural practice supported by serious governmental investments took place during the Soviet Union period after the Second World War.After the Soviet Union collapse in 1991,general deterioration of the agricultural economy sector and the absence of investments resulted in cessation of organized soil conservation measures application at the nation-wide level.However,some of the long-term erosion control measures such as forest shelter belts,artificial slope terracing,water diversion dams above formerly active gully heads survived until the present.In the case study of sediment redistribution within the small cultivated catchment presented in this paper an attempt was made to evaluate average annual erosion rates on arable slopes with and without soil conservation measures for two time intervals.It has been found that application of conservation measures on cultivated slopes within the experimental part of the case study catchment has led to a decrease of average soil loss rates by at least 2.52.8 times.The figures obtained are in good agreement with previously published results of direct monitoring of snowmelt erosion rates,reporting approximately a 3-fold decrease of average snowmelt erosion rates in the experimental sub-catchment compared to a traditionally cultivated control sub-catchment.A substantial decrease of soil erosion rates on arable slopes has been equally reflected in a corresponding decrease of aggradation rates in the main valley bottom and tributaries.