The possibility of use of the previously developed calculation technique of the North Rivers flow hydraulic records for the Ob River, the largest river in Russia by basin area, flowing under severe conditions in West Siberia was examined. The calculation technique is based on the model of heat and moisture exchange of the geological substrate with the Earth’s atmosphere, the Soil-Water–Atmosphere–Plants (SWAP) model, in conjunction with information support based on global databases of geological-substrate parameters and information obtained from observational data collected by weather stations within the Ob River basin. Uncertainty of the Ob River flow was assessed. Additionally, the ability of the SWAP model to reproduce multiyear dynamics from average values of snow reserves in the Ob-Irtysh basin was examined.