River flow to the Arctic Ocean plays a significant role in the oceanic freshwater budget accounting for about 2/3 of the total freshwater flux to the Arctic Ocean. Ocean salinity and sea ice formation are critically affected by river input and changes in the freshwater and heat fluxes to the ocean can exert significant control over global ocean circulation via the North Atlantic deep water formation. There are mounting evidences that hydrological regime across the pan-Arctic is experiencing an unprecedented degree of change. However, the exact causes of such change are not immediately apparent, as they constitute a complex interplay between climate- and human-induced drivers. We used a new version of University of New Hampshire Water Balance Model (WBM) to quantify major sources of changes in river flux to the Arctic Ocean from Eurasian drainage basin. WBM is a grid based model which simulates the vertical water exchange between the land surface and the atmosphere and the horizontal water transport along a prescribed river networks for both natural and anthropogenic systems. The model accounts for sub-pixel land cover types, glacier and snow-pack accumulation/melt across sub-pixel elevation bands, permafrost dynamics, anthropogenic water use (e.g. domestic and industrial consumption, and irrigation for most of existing crop types), hydro-infrastructure for inter-basin water transfer and reservoir/dam regulations. To identify and quantify contributions of individual drivers/factors to river flow we used a new water source tracking capability recently developed in WBM. It allows “fingerprinting” of water at all steps in the water cycle such as in soils, groundwater pools, lakes, reservoirs, and fluxes such as originated from snowmelt, rain, glacier runoff, and baseflow. By comparing the difference in water component fractions in water storages and fluxes resulting from multiple historical runs we were able to quantify responses of each water source to the changes in climatic drivers and to characterize causes of observed changes in river flow to the Arctic Ocean. This work was mainly supported by Russian Foundation for Basic Research, grants: 18-05-60192 and 18-05-60240.