The Variation of the Liquid Monthly Average Flow in the Hydrographic Basin of the Uz River
Keywords:temporal variation, occurrence frequency, variation coefficient, rainfall
The study of the characteristics pertaining to the variation of the average monthly flow is based on the calculation of the multi-annual average extracted from the average monthly flows, on the relative and absolute occurrence frequency of the maximum annual average flows, the analysis of the maximum and minimum seasonal average flows, the occurrence probability of the highest flows, the variation amplitude highlighted with modular coefficients (Kmax si Kmin), the ratio between these two modular coefficients (Kmax/Kmin), but also the Cv variation coefficient calculated based on the entire data series relative to the average flows. Also, there were estimated the maximum flows with different insurances: Pearson III distribution, which adjusts the most effectively the empirical insurances. The variation of the average monthly liquid flows is studied in respect with the variation of the average annual rainfall registered between 1980 and 2009. In this respect, there were established correlations between the flow variations and rainfall, as well as the tendencies at the two hydrometric stations (Cremenea and Dărmănești). By analyzing the variation of the average monthly flows it was possible to establish the genesis of the fluctuation of the flows registered during different periods of the year, as well as the complex way of combining the water sources for the Uz river. The liquid average flows from the Uz hydrographic basin present a temporal variation related to the evolution of climatic factors. The maximum values of the liquid average monthly flows occurred in the month of April in 1970 at the Uz valley hydrometric station and at the Cremenea station, while in 1984 they occurred at the Dărmănești hydrometric station. The registration of the maximum values for the average monthly spring flows can be explained by the intensification of the cyclonic activities responsible for the generation of abundant rainfall overlapped over the rising air temperature fostering snow meltdown at ground level.