THE ANALYSIS OF PRECIPITATIONS USING THE METHOD OF THE PERCENTUAL DEVIATION OF RAINFALL QUANTITY OF CIBIN HYDROGRAPHIC BASIN PUBLISHED

Simona Spânu
Cibin Basin has, in the 2237 km2 on which it stretches, a level difference of over 1700 m between its spring (the glacial circle in the Cindrel Mountains where Iezerul Mare and Iezerul Mic are situated) and its mouth (Sadu-Hârtibaciu-Cibin-Olt confluence area).The altitude plays a determinant role in the precipitations regime. Besides, the configuration of the relief also leaves its mark upon the moving air masses, determining the formation of types of precipitations. The analysis of the long data ranges offers an ensemble image regarding the succession of periods with pluviometric surplus and deficit for Cibin hydrographic basin. This approach allows the identification of a possible cyclicity of the episodes with flooings and droughts. The analysis of the annual regime of precipitations in Cibin hydrographic basin for the interval 1961-2005 and that of the frequency with which precipitations have been registered on different risk classes denote that in Sibiu only a low risk of surplus and deficit is manifested, in Agnita the extreme values with medium and major risk are of deficitary nature, and in Păltiniş the extremes of medium and major risk are characteristic to the surplus quantities.  The quantity of precipitations fallen in the area of Cibin hydrographic basin has been grouped according to deviation classes (one normal class and five classes for each of the quantities that are higher and lower than the normal) and to pluviometric domains (where there have been gathered the values of all the classes with positive and negative deviations, comparing them to the normal domain). The characterization of the effects produced by long-term rains, as well as rain showers, was done from the point of view of the risk they induce in the natural and antropic environment. Of interest for this analysis are the precipitations that fall during the vegetation period and which affect the crops.  The analysis of the annual regime of precipitations in Cibin hydrographic basin for the interval 1961-2005 and that of the frequency with which precipitations have been registered on different risk classes denote that in Sibiu only a low risk of surplus and deficit is manifested, in Agnita the extreme values with medium and major risk are of deficitary nature, and in Păltiniş the extremes of medium and major risk are characteristic to the surplus quantities. The quantity of precipitations fallen in the area of Cibin hydrographic basin has been grouped according to deviation classes (one normal class and five classes for each of the quantities that are higher and lower than the normal) and to pluviometric domains (where there have been gathered the values of all the classes with positive and negative deviations, comparing them to the normal domain). Then there have been established groups of pluviometric risk through surplus and deficit, to these being added the group with no pluviometric risk. The frequency of the years with pluviometric risk through surplus is low in the depression and plateau area, but it is worth mentioning that in the mountains the risk through surplus reaches 20%, and the one through deficit 15,6%. The risk through surplus signalled in the mountain region also spreads in the rest of the area, especially in Sibiu Depression, generating hydrologic risk.
precipitations; percentual deviation of rainfall quantity; pluviometrical risk
Presentation: oral

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