Vulnerability Assessment of Dam Water Supply Capacity Based on Bivariate Frequency Analysis Using Copula

초록

The vulnerability of the water supply capacity of a dam is defined as the expected deficit volume from a typical water deficit event. In this study, a water deficit event was assumed to be a rectangle composed of the deficit duration and deficit intensity whose occurrence probability was then estimated by the bivariate frequency analysis based on the copula method. This approach is different from the conventional one based on the assumption of the same occurrence probability for all events. This proposed method was applied to the Namgang dam in Korea as an example and the resulting estimate of the vulnerability was compared with the conventional method. First, the OR' concept was found to be better than the AND' concept in the calculation of the occurrence probability. Additionally, based on the consideration of multicollinearity, it could be concluded that the occurrence probability should be estimated by considering the water deficit intensity and duration. For the Namgang dam, the vulnerability was determined to be 9.11 x 10(6) m(3), which is about 3% of the total storage capacity. This estimated vulnerability is also about 70% of the amount estimated by applying the conventional method with the same occurrence probability for all water deficit events.

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