A three-component hydrograph separation based on relationship between organic and inorganic component concentrations: a case study in Eastern Siberia, Russia

Chemical monitoring data on two rivers draining small-scale and medium-scale watersheds were collected and analyzed. It was shown that the variability in stream water chemistry is explained mostly by two natural processes. The first process is the change in dominant water flow path in soil during the year and the second process is the change in water table depth. These changes are reflected in dissolved organic carbon (DOC) to base cations (BC) ratio (DOC/BC). The increase of DOC/BC ratio (or decrease of BC/DOC ratio) from winter to summer is due to proportional dilution of groundwater by near-surface flow. The decrease of DOC/BC ratio from summer to winter is due to dilution by interflow. The ratio values typical for hydrological periods, when one of the sources absolutely predominated over the others were used as end-member signatures. The solute concentrations calculated using discharge fractions derived from mixing equations were highly correlated to those measured in riverine water.