Peculiarities of Long-term Phases of the Increased and Decreased Don and Lena Runoff in the 19th–21st Centuries

Abstract

The results of studying long-term (lasting 10–15 years or more) phases of decreased and increased conditionally natural annual and seasonal runoff of the Don River near the village of Razdorskaya and the Lena River near the village of Kyusyur are considered. The retrieval of long-term water flow time series (excluding the changes that are caused by anthropogenic impacts from the observed water flow) is based on the transformation of the annual hydrograph of average daily water flow using the Kalinin–Milyukov method. The long-term phases of annual and seasonal runoff have been identified on the basis of cumulative deviation curves and criteria for statistical homogeneity of time series by their averages. For the entire period of observations on the Don (1891–2019) and the Lena (1936–2019), two cardinally different types of long-term dynamics for contrasting phases of annual and seasonal runoff that are characteristic of these rivers and common in most of Russia have been revealed. On the Lena, the phases of decreased and increased values of annual and seasonal runoff have changed quasisynchronously, whereas on the Don, the phases of annual runoff and snow melt flood runoff on the one hand and summer-autumn and winter runoff on the other hand have changed asynchronously. The main characteristics of the contrast phases have been determined.