%0 Journal Article %T Use of integrated functions to establish the phases and cycles of fluctuations in the flow of rivers Vit, Osam and Yantra %J Bulgaria, the Bulgarians and Europe - Myth, History, Modernity %D 2017 %X The periods, phases, cycles and chronologies occurring in the annual outflow of the rivers Vit, Osam and Yantra are established through modern methods. The temperature, rainfall and drainage complex of the watersheds are carefully analysed. The study uses a different number of stations with data from different periods. The analysis was conducted with integrated functions. The main phases which the manifesting cycles stand out. The study proves the close relation between rainfall and river runoff and the weaker relation between temperature and river flow. The correlation coefficient is used to prove that the various watersheds integrate rainfall according to their physical and geographical capacity. Each considered process composed of a number of elements of chance must be cyclical and have internal correlation %K integral curves^ phases^ cycles^ Vit^ Osam^ Yantra. %U http://journals.uni-vt.bg/bb/eng/vol11/iss1/34