Analysis and evaluation of long-term changes in the main hydrometeorological characteristics on the Valdai

Abstract

The relevance of the topic is due to the continuing interest in the regional consequences of climate warming and the updating of estimates of long-term changes in the extended series of hydrometeorological observations. The aim of the study was to analyze the long-term changes in air temperature, precipitation, the maximum depth of soil freezing, the height of snow cover, the regime of underground water and river flow for the total observation period of 1939–2018 based on the materials of the Valdai Research Hydrological Laboratory. The average annual air temperature has increased by 1.4°C since 1988, with the most significant increase in air temperature in January-February and in March. Annual precipitation totals increased by an average of 114 mm compared to 1939–1979, the increase in precipitation occurred mainly in the colder months of the year. The maximum depth of soil freezing decreased by an average of 2 times. At the same time, on the studied small watercourses (the Taiga log and the river Polomet'). The average annual flow of rivers has not changed significantly. Multidirectional trends are observed in the long-term fluctuations of the maximum spring flow of rivers. Ground water levels did not increase in 1991– 2016, and in some upper aquifers they decreased. The largest replenishment of groundwater reserves in the spring began to occur on average 2 weeks earlier. Over the past 30 years, the minimum 30-day winter water consumption has not increased, and the variation of fluctuations in the minimum 30-day summer-autumn water consumption of rivers has increased