River runoff in European Russia under global warming

<p>Regional spatially distributed runoff formation models for the Volga, Don, Northern Dvina, Pechora and Kuban river basins were developed using ECOMAG software, global databases (DEM, soils, landscapes) and weather station dataset. According to hydrological models, good or satisfactory results were obtained for calculating the daily runoff using the KGE criterion for each of 35 gauges, PBIAS for 34 gauges, NSE for 33 gauges. </p><p>For example, the Volga basin model based on the Earth system models output data reproduces the annual runoff over the historical period with an error of 1.5–6% relative to the calculation based on the weather station data. The largest relative calculation errors are typical for the winter runoff (up to 17%), and the smallest for the runoff during the spring flood (up to 6%).</p><p>Under global warming and critical threshold of 1.5°С and 2°С (in the context of UPH #1), the assessment of the runoff anomalies of the Volga and its main tributaries showed the following general features: an increase in winter runoff, a decrease in runoff during the spring flood and summer-autumn, and, as a result, a decrease in annual runoff. The decrease in annual runoff was 10–11% under the realization of both warming scenarios relative to the period 1970–1999. The largest relative decrease in runoff by 17–20% was noted for the Oka and Upper Volga, while for the Kama only by 1–5%. The increase in the winter runoff of the Volga amounted to 17% and 28% under global warming of 1.5°C and 2°C, respectively. The negative runoff anomalies for the period of spring flood and summer-autumn were in the range of 21–23%. The most intense increase in winter runoff by 30–40% was characteristic of the Upper Volga, and the least intense was for the Oka by 12–20%, depending on the rate of global warming. The largest relative decrease in runoff during the spring flood and summer-autumn was noted in the Upper Volga (about 40%), and the smallest was noted in the Kama by 8–10%.</p><p>This study was supported by the Russian Science Foundation (project No. 20-77-00077).</p>