Spatial-temporal Transformation of the Volga Reservoirs’ Soil Complex Communication 6. The Kuybyshev Reservoir Bottom Sediments and their Mapping with the Use of Geo/information Techniques

The article presents the geo/informational analysis of the spatial/temporal transformation of the Kuybyshev Reservoir soil complex structure and qualitative composition according to the materials of hydrological surveys of 1961, 1983, 2001–2002 and 2015–2017. As a result of the raster images vectorization we obtained three topical geo/information layers, every one of them contained the data sufficient for mapping the appropriate period of the researches. Analysis of the fourth layer in the area of the model Volga-Kama Expansion (F = 1011 km2 ) characterized by a complicated crest-shallow bottom relief, diverse hydrodynamic processes caused by water input via the Volga and the Kama and a wide spectrum of the windwave activities has shown insignificant changes in the bed structure after 2002. In 2015–2017 analysis of the bottom sediments types' distribution at 45 control stations has reaffirmed the stability in all 10 orographic stretches (reaches). Increase of the stations' number will make more complicated the bottom sediments distribution mosaic and will not significantly change their spatial/temporal transformation found during the first years of the reservoir functioning. We have found that at the current stage the reservoir soil complex is represented by coarsegrained deposits (44%), fine-grained sediments (42%), diffused rocks (13%) and waterlogged soils 91%) located near the floodplain islands of the Kazan and Chistopol regions of variable backwater. The organic matter and biogenic elements content is at the level typical for the plain reservoirs' bottom sediments. The Kuybyshev Reservoir level of heavy metals pollution in the Volga cascade system has been estimated as low.