Основни черти на цикличните колебания на пролетния отток на реките в Северна България

Стойчев, К., Стоянова, Р., Генев, М. Основни черти на цикличните колебания на пролетния отток на реките в Северна България

Stoichev, K., Stoianova, D. Genev, M. Basic features in the cyclic variations of rivers spring flow in North Bulgaria

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BASIC FEATURES IN THE CYCLIC VARIATIONS OF RIVERS’ SPRING FLOW IN NORTH BULGARIA

K. Stoichev, R. Stoinova, M. Genov

Summary

In this paper the cyclic changes of the total spring flow, including the period from March to May have been examined as well as the changes in the monthly water quantities for the same period.

Changes have been analysed by dynamic average quantities (Fig. 1—3) and by correlation functions.

Two obviously expressed positive cycles correspondingly in 1936—1947 and 1948—1959 as well as three slighter in amplitude and duration have been established in the spring flow variation.

Maxima and minima of these cycles are shown in Table 4. Almost the same cycles have been observed in the flow variations in the different months (Fig. 2). However, these cycles are characterised by some synphase with respect to their beginning and finishing.

Correlation functions’ analysis (Table 3) shows that the 11-th year cycles (86%) and 21-year cycles (71%) are characterised by the biggest frequency. The rest of the cycles are of lower frequency (64%).

Cyclic recurrence of spring flow defines to a considerable extent the annual flow variations. Correlation indexes between them are 0.60—0.90 (Table 1).

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