БАГАТОРІЧНА МІНЛИВІСТЬ СТАТИСТИЧНИХ ПАРАМЕТРІВ РОЗПОДІЛУ СЕРЕДНЬОГО РІЧНОГО СТОКУ ВОДИ РІЧОК УКРАЇНИ З НАЙДОВШИМИ РЯДАМИ СПОСТЕРЕЖЕНЬ

Abstract

The purpose of the study is to study and analyze the long-term variability of the statistical parameters of the distribution of the average annual water flow (norms, variation coefficients, and asymmetry) of the rivers of Ukraine, which have long series of observations. For this, we used the sequence of observations of the average annual water discharge at hydrological posts: river Dniester – the city of Zalishchyky, an observation period of the year 1882-2015; river Prut – the city of Chernivtsi, 1895-2015; river Desna – the city of Chernihiv 1895-2015; river Pripyat -the city of Mozyr, 1882-2014; river Southern Bug – the city of Alexandrovka, 1914-2015; river Danube – the city of Reni, 1861-2015; river Dnipro – the village of Lotsmanskaya Kamenka, 1818-2015. The duration of actual continuous observations varies from 102 to 155 years. The longest series of average annual water discharges was 198 years (the Dnieper River – the village of Lotsmanskaya Kamenka), but it consists of observations (1818-1961 – 144 years) and restored (1962-2015 – 54 years). To identify the long-term variability of the main parameters of the distribution of the average annual water flow, a comparison method is used. In our case, we compared the main statistical parameters of the rivers understudy for individual 30-year periods – sequential and with an overlap of 15 years – with the main parameters that were determined for the entire observation period. The determination of the average absolute deviations of the main statistical parameters for 30-year periods from the parameters for a long-term period, defined in %, made it possible to analyze the degree of their long-term variability. Slight variation in time has runoff norms and variation coefficients, which can be considered the most stable distribution parameters. In a long-term section, the variability of these parameters for runoff norms is in the range from 2 % to 14 %, for variation coefficients – from 7 % to 23 %. It should be noted that the highest percent deviations (14 % and 23 %, respectively) are for the observed average annual flow of water on the river Prut – the city of Chernivtsi, which turned out to be heterogeneous according to the Fisher criterion. The greatest amplitude of time variability falls on asymmetry coefficients, for which the average absolute deviation of parameters over 30-year periods from parameters over a long-term period for the studied rivers is in the range from 29 % to 98 %.