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Based on observational data from 70 hydrological stations in the North Caucasus an evaluation of present values of mean annual runoff, minimum monthly winter and summer runoff was carried out. Series of maps was drawn. Significant changes in mean annual. minimum monthly and maximum runoff during last decades have been revealed in the North Caucasus. A rise in both amount of water availability and potential natural hazard is characteristic of the most of the North Caucasus that is considered to be caused by recent climate change. Mean annual runoff during 1978-2010 increased compared to 1945-1977 by 5-30 % in the foothills and by 30-70% in the plain area. An increase in winter minimum monthly runoff is as well most intensive in the plain part of study area (>100%). Within the foothills it amounts to 50-100%. In mountainous area long-term oscillation of winter minimum monthly discharge strongly depends on local factors, such as geological structure. The rate of the increase in summer minimum monthly discharge regularly grows from central foothill part of Northern Caucasus (30-50%) to the Western plain territory (70-100%). In Kuban river basin 30% of analyzed gauging stations show positive trend in maximum instantaneous discharge, while 9% negative. On the contrary, in the Eastern part – Terek river basin – negative trend in maximum instantaneous discharge is prevalent: 38% of gauging stations. Positive trend in Terek river basin is characteristic of 9.5% of analyzed gauging stations.

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Abstract. Extreme hydrological events on the rivers of European part of Russia are closely related to the hydrological regime transformation answering recent climate changes. Rivers in this region used to be traditionally attributed to the Eastern-European type with well-pronounced seasonal flood wave and quite low flow period during summer and winter. During the last twenty years the role of the occasional floods became more and more important. Number of winter floods, connected with thaws rose dramatically, in the same manner as summer flash floods. In this study, the frequency and duration of extreme low flow and high flow events is analyzed. The deficits during hydrological year were calculated. Due to results increase in natural runoff regulation, does not reduce frequency of extreme events, in some regions it raises.

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