CLIMATE CHANGE EFFECT ON MAXIMUM FLOOD STAGES IN ABAKAN RIVER

The study topicality relates to the effect of climate changes and increased recurrence of dangerous hydrological events on rivers of southern Siberia. The observed and predicted changes in flood regimes are caused by a variety of factors and require different approaches in order to characterize the types of these changes. The aim of the study is stochastic modeling of solid precipitation total in the Abakan river basin, establishing relationship between precipitation and maximum water levels in the Abakan river during the flood period under spatial and temporal variability of hydrometeorological factors. Methods: comprehensive geographical and hydrometeorological analysis, dependence establishment based on long-term hydrometeorological observations using mathematical statistics methods, methods (developed by V.P. Galakhov) for estimating precipitation total in the basin with regard for orographic correction to the velocity of vertical movements in the frontal zone. Results. The crucial factor in the formation of maximum flood levels is winter precipitation amount. Heavy rainfalls during flood recession may significantly influence the maximum water levels. However, climate changes of recent decades in river mountain basins of southwestern and eastern Siberia are evidence of dependences between autumn soil freezing and formation of snowmelt-induced maximum stages. In some years during the flood period, decreased maximum water levels are probable in basins with prevailing foothill plains, unlike those with overwhelmingly mountainous landscapes. We have developed a method for calculating winter annual precipitation total in the Abakan basin taking into account physical features of precipitation formation in the mountains, in particular the orographic correction to the velocity of vertical movements. The independent data suggest that algorithms for calculating snowmelt-induced maximum stages based on regression dependencies do not always give adequate results, therefore updating with regard for freezing processes in the foothill plain is required. Besides, extra observation data are called for obtaining the general statistical dependence.