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[References: 40 tit.]

Relationships between the amount and chemistry of atmospheric water, river water, and groundwater are analyzed in the catchments of six small tributaries of the Tom River near Tomsk City (Russian Federation, West Siberia, Ob R. basin) using data of long-term hydrogeological and hydrological observations (from the 1970s to 2019). A decrease in the rate of water exchange was shown to cause an increase in the interaction time in the water–rock system and, accordingly, in the total concentration of dissolved salts in groundwater. For the first time for the lower reaches of the Tom R., it was shown that the intensity of interaction between river water, subsoil water, and artesian water can be evaluated with the use of the coefficient of variation Cv(Ym) of the monthly runoff depth values of small rivers—the greater the value of Cv(Ym), the greater the closeness of deep aquifers and groundwater TDS. The processes of rock leaching and dissolution were found to dominate in areas with considerable replenishment of water reserves in the warm season of the year (on the right side of the Tom R. catchment), while the input of substances from outside, e.g., with precipitation, dominates in the area were groundwater resources are mostly replenished during snow melting.