Indicators of high and low inflow to Lake Baikal and the runoff of its main rivers

Abstract

The differentiation of the surface water inflow values to Lake Baikal and the runoff characteristics of the main Baikal rivers into seven gradations according to the water availability conditions was studied on the basis of regular observations. This classification enables to operate with numerical values of the water availability criteria of the considered indicators. It has been demonstrated that the range of fluctuations in the river inflow and runoff within individual classes (gradations) is determined by sample distribution parameters, with the range narrowing from high to low water availability. The classes of catastrophically high or low water content in the annual and monthly inflow values and the runoff characteristics of the Selenga, Upper Angara and Barguzin rivers for 1961–2020 were observed mostly once each. For earlier years, which are outside the calculation period, the values of inflow and water runoff of the rivers with a lower recurrence rate were observed. The low inflow observed in 1903 and the spring flood period of the Barguzin River in 1936 corresponded to a recurrence interval of once every 1,000 years or less frequently.