Author(s)

E. Uspuras & J. Simaityte

Abstract

The dam of the Kaunas hydropower station in Lithuania is an important system from the safety point of view because only several kilometres downstream the dam Kaunas city is situated with population over 450 thousands. The paper presents the Kaunas dam risk analysis aspects, where the main part takes overtopping probability estimation. The purpose of this study was the critical water level modelling by the dam and to estimate overtopping probabilities by several scenarios - including spillway failure probabilities. The statistical data -maximum annual flow data of 76 years-water input to the Kaunas reservoir from The Nemunas River were collected and analysed. Also there were analysed water level and reservoir capacity data near the dam. The mathematical model of Kaunas dam which let perform prognoses of the critical reservoir capacity and at the same time the critical water level, as it is known as dangerous for dam and may cause the dam failure. The mayimurn flow data were assumed to be independent and identically distributed. the extreme value distribution helped to estimate critical water levels probabilities. The every day flow and water release data thorough the dam spillways let to calculate everyday reservoir water volume and to know water level during the flood period. As a result, there were estimated three critical level probabilities under three gate operation scenarios. Estimated outlet failure probabilities and water level probabilities in each scenario yields the overflow probability (when water level reaches the top of the dam). As the Kaunas dam height is 48 meters, such water level leads to overtopping and according international literature almost 50% leads to dam

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