The Mechanism and Regularities of Ion Runoff Formation in the Ob River (Western Siberia) under the Influence of Its Tributaries and Underground Feeding

Abstract

An analysis of observation data was conducted on the chemical composition of river and groundwater in the Ob River basin, covering more than 23 thousand samples taken from the network of governmental monitoring of surface and groundwater, the materials of scientific research, and engineering surveys. A model was developed for computing the total content of major ions along a stem of the Ob River. As a result, quantitative estimates of the total ion runoff and its underground component were obtained. Conclusions were drawn relating to: (1) uneven distribution of the ion flow over the Ob basin; (2) the predominant removal of dissolved solids from mountain regions and adjacent forest steppe and southern taiga areas and their accumulation in the middle taiga subzone with the maximum thickness of sedimentary cover of Mesozoic–Cenozoic deposits; (3) the influence of the main tributaries on the total dissolved solids (TDS) in the Ob River, limited to only a few kilometers downstream of their mouths (the rivers of Irtysh, Chumysh, and Severnaya Sosva as exceptions); (4) the maximum impact of groundwater on river water TDS in the forest steppe and southern taiga areas of the upper and middle Ob basin and minimum impact in the flat part of the lower reaches of the Ob in forest–tundra and tundra.