ОЦЕНКА БАЛАНСА НАНОСОВ РЕК ОБЬ И ЕНИСЕЙ

Abstract

This paper presents results of comparative analysis of the sediment budgets of the Ob’ and the Yenisei, base on universal erosion equations, RUSLE using 250 m resolution DEM GMTED 2010. Cumulative volumes of sediments accumulated in the stream catchments were estimated calculating the difference between erosion and sediments runoff of the studied basins. Thus, the difference between total erosion (watershed erosion + bank erosion) is (1250 MT/year + 35 MT/year) for the Ob and (315 MT/year + 21.9 MT/year) for the Yenisei. Sediment runoff in the mouths of both rivers estimated based on MSU data is 63.5 MT/year for the Ob and 32.5 MT/year for the Yenisei; Sediment runoff in the mouths estimated based on Roshydromet data is 16 MT/year for the Ob and 2.4 MT/year for the Yenisei. Sediment runoff was used to calculate the total deposition of matter in the catchment area during the transport of sediments from sources to sinks, for the Ob total deposition is 1270 MT/year, for the Yenisei is 335 MT/year. For the unregulated part of the Ob’ catchment, the accumulation was 56.5 MT/year, and for the unregulated part of the Yenisei catchment was 43 MT/year. The coefficient of reduction of sediment runoff (1/SDR) downstream, based on new samplings of sediment runoff in 2018–2019 in the mouths of both, Ob and Yenisei, was 2.3, and for the entire catchment area 20 and 30 respectively. Volume of sediments moved by denudation processes in the basin ends up being redeposited within the same fluvial systems. Thus, under the current hydro-meteorological regime, the large drainage basins in Russia and elsewhere are major depositional systems.