Changes in River Ice Formation Dates and Tests for Their Statistical Significance Assessment

Resumo

A methodological approach is developed to the analysis of long-term series of observations of hydrological characteristics including the testing of the hypothesis of randomness both for the full series and for their parts; the diagnosis of intraseries dependence of time series; the testing of the hypothesis of homogeneity of the parts of observations series under comparison; the identification of change points. Statistically significant changes in the dates of river ice formation in the Votkinsk Reservoir catchment were revealed for the periods of 1975–2012 and 1983–2012, whereas the entire observation period (1936–2012) did not reveal such changes. A possibility of localization of change points for the observation series was assessed using the inversion test.