Long-term changes in water flow of the Volga basin rivers

Irina Milyukova,Oleg Borodin,Aleksandr Georgiadi,O Makarieva,D Post

doi:10.1051/e3sconf/202016305008

Abstract

The long periods/phases (with a duration of more than 10-15 years) of increased and decreased water flow of rivers in the Volga river basin were identified. The annual and seasonal water flow (over snow-melt flood period, as well as summer–autumn and winter low-water seasons) of six representative rivers over observation periods more than a century in duration, starting from the 1870s–1890s up to 2016, was used. In addition to this, periods with the average runoff close to its normal value were also observed. The boundaries of contrast phases were determined using normalized cumulative deviation curves in combination with Student’s test of the statistical homogeneity of the data series. The duration of the phases varies from 10 to 96 years. The phases of lower runoff were generally longer than those of higher runoff (this is especially typical of the winter and summer–autumn low-water season). The identified contrast phases show a statistically significant difference between the annual and seasonal runoff. The analysis of the data series of alteration of phases with increased and decreased water flow in hydrological seasons of the year allowed the authors to identify three major types of their long-term dynamics within the Volga river basin.

Highlights

Long-term variations of the annual and seasonal river runoff show periods of its decreased and increased values with different duration
The article presents the results of comparison of contrast phase characteristics of six representative rivers in the Volga basin over more than century-long observation periods, which feature considerable differences in natural conditions and the character of anthropogenic load
The approach to the analysis of the long-term phases of changes in the annual and seasonal runoff caused by climate changes is based on the analysis of data series of conditionally natural runoff with the use of cumulative deviation curves, statistical homogeneity criteria of average runoff values, and the comparison of the characteristics of the identified phases of contrast water flow

Summary

Introduction

Long-term variations of the annual and seasonal river runoff show periods (phases) of its decreased and increased values with different duration. Long contrast phases with a duration of 10–15 and more years can be identified in them. They are observed against the background of appropriate climate changes. Anthropogenic factors cause considerable changes in these phases [1,2,3,4,5]. The article presents the results of comparison of contrast phase characteristics of six representative rivers in the Volga basin over more than century-long observation periods (starting from the 1870–1890s), which feature considerable differences in natural conditions and the character of anthropogenic load.

The methods used to analyze the annual and seasonal runoff

The main types of temporal dynamics of long phases

The duration of the long phases

Differences between the average runoff of contrast phases

Conclusions