Inter/annual changes in the Volga River water content under global climate change

Relevance. Timely assessment of inter/annual and seasonal changes of the Volga River water flow in the conditions of global climate change is necessary for studying of their impact on formation of the Volga-Kama cascade reservoirs’ hydro/chemical and ecological status. Methods. To analyze inter/annual changes of the Volga River water content over the 1958–2023 period we have established a data base for water discharge in the Zhiguli reservoir range. The samples arranged by years have been statistically processed with Statistica sof-ware. Results. During the 1976-2023 period, average annual fl ow of the Volga in the Zhiguli reservoir range has been increased by 10 % in comparison with the low-water period of 1958–1975 observed prior to the beginning of the current climate change. Th e water fl ow increase rate was not uniform: during the 1976–1996 period, the water fl ow considerably increase by 14 % with average rate of 42 m3/s per year; during the 1997–2023 period we observed the water flow decrease by 7 % with average rate of 17 m3/s per year. Th ere was no many-year regulation of water fl ow in the Volga, so, its many-year changes were caused by the climate change. We have stated that substantial variability of average monthly water discharge and discrepancies between average annual and average monthly discharge changes are caused by seasonal water flow regulation in the Zhiguli reservoir range under the conditions of the water flow increase caused by the climate change. The most average monthly water discharge changes were registered in April: over the 1958–1975 “low-water” period they decreased by 30 %, while over the 1976–1996 “high-water” period they increased by 153 %, and over the 1997–2023 “average-water” period they decreased by 49 %.