Runoff components of small catchments in Sikhote-Alin: summarizing the results of field measurements and tracer modeling

The article summarizes results of the systematic study of the streamflow formation of two small catchments in the upper part of the Ussuri River. The study was carried out by the hydrograph separation technique (using detailed data of the hydrochemical and hydrological monitoring) and the use of a tracer mixing model in conjunction with EMMA. Performed in the period from 2011 to 2016 the studies allowed to calculate the river runoff components of the summer-autumn period at 3 gauge-stations and evaluate their mutual dynamics at different time scales. It is shown that in the case of landscape uniformity of the catchment (the Medvezhiy Creek), the river flow can be represented as a result of 3 sources’ mixing. This, the most common, scheme for the hydrograph separation includes following sources: a direct rainfall flow, an organic soil water component, and an underground baseflow. If the catchment’s landscape structure is clearly heterogeneous (the Elovy Creek), the river flow can be represented as a result of 4 sources’ mixing. In this case, the fourth source appears as a result of the separation of soil water component into individual components – organic and mineral. This separation is due to the spread in the basin of the cold upper belt of fir-spruce forests, whose soils are characterized by a lower rate of organic matter destruction and a deeper illuviation process of DOC. Statistically significant dependencies of the some runoff components’ proportions against river discharges were identified, systematization of which makes them promising for practice in hydrological monitoring and forecasting.