THE REASONS OF THE INSTATIONARY OF THE SEASONAL RUNOFF OF RIVERS AND STREAMS IN THE RIKA RIVER BASIN

Liudmyla Gorbachova, Tеtiana  Bauzha, Ukrainian Hydrometeorological Institute, Ukraina

Abstract

Many researches indicate that the climate change is influencing on the seasonal runoff of the rivers and causes the break of the stationary processes of its formation. Therefore, the goal of this paper is the research the changes with time of the average values of the seasonal runoff of the Mountain Rivers and streams in the Rika River Basin, air temperature and precipitation. It will allow defining possible changes in the intrayearly distribution of the runoff and analyzing the reasons for such changes.
The 16 points of observation were chosen for research which is located on the 4 small and 2 medium rivers and 5 streams. The period of observation on these water bodies is from 46 to 49 years (since the beginning of the observations to 2006 inclusive).
Dynamics of the seasonal runoff of the rivers and streams on 7 of observation gauges (from 16 gauges) has the statistically significant trends on 5 -% the significance level. It is indicates to the statistical inhomogeneity of the seasonal runoff in of the time. The dynamics of the seasonal air temperature has the statistically significant trends by summer and the dynamics of the seasonal precipitation – by autumn and spring. The analysis of the difference integral curves showed that the statistically significant of the trends are in the observations series which does not have of the full hydrological cycle. As a consequence, that the presence of the statistically significant or statistically insignificant trends in the observations series have the periodic natures, which don't only depend from duration of the observations, but also depends from length of the separate full hydrological cycles and of their dry - and wet phases.
So, the detected changes with time of the average values of the seasonal runoff of the watercourses of the Rika River also is the cycling fluctuations, which have the well denominated synchronous view with change of the average values of the atmospheric precipitation and air temperature. Hence, the observations series of the seasonal runoff of the rivers and streams of the Rika River, and the air temperature and precipitation in their basins are the stationary.