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Abstract

An approach to reducing uncertainties in modeling of river runoff sources by expanding the information support of the hydrological model with hydrochemical data is presented. The object of the study is the upper reaches of the Moskva River with an area of 1360 km². The physically based ECOMAG model was used to simulate hydrological processes in the catchment area. Numerical experiments demonstrated a strong equifinality effect, in which several different sets of the model calibrated parameters produce equally good results of simulation of runoff hydrograph, but contribution of the water sources (quick flow, interflow and baseflow) to the total runoff significantly differ. In order to reduce the equifinality effect, the proposed method allows simultaneous use of conjugate calibration by the total hydrographs of the daily runoff and additional calibration by the contribution of the base flow determined by hydrochemical data. Specific marker compounds of environmental tracers of the water sources were used to support the delineation of source contributions to the mixed-signal observed in the river: specifically chemical oxygen demand (permanganate, dichromate), specific electrical conductivity, the concentrations of Na+ and K+ ions and total phosphorus. Using the statistical approach and the mass balance method, the contributions of various sources to the river runoff were determined. The proposed approach usually ensures the modeling accuracy of the runoff sources in different phases of the water regime in the order of 10-20%. This study was carried out under Governmental Order FMWZ-2022-0003.