Long-term dynamics of maximum flood water levels in the middle course of the Ob River

Abstract

Results of statistical analysis of the long-time series of flood maximum water levels in the Ob River middle course (West Siberia, Russia) are presented. Most time series are statistically non-homogeneous at the 5 % level of significance. In most cases, there is a violation of homogeneity in 1959 due to the Novosibirsk HPP flow regulation, but there might be also some natural change. The extremely low maximum levels of 2012 are the “outliers” from probability distribution functions at 5% significance level. In the modern period (after 1959), some downward tendencies in maximum water level change over the middle course of the Ob River cause decrease in the area, depth and duration of floodplain inundation.