Rechecking the characteristic flood levels of a built reservoir after extending the hydrologic time series

Abstract

Reservoirs are one of the most efficient infrastructures for integrated water resources development and management in a river basin. Rechecking characteristic flood levels plays a more and more important role in flood risk management, especially with extending hydrologic time series for a built reservoir. Hydrologic uncertainty is a key factor which impacts probability distribution of characteristic flood levels. Methodology of stochastic differential equation for flood routing is proposed in order to derive probability distribution of characteristic flood level for a built reservoir. The Three Gorges reservoir in the Changjiang River basin of China is selected for a case study. The uncertainty of flood is transformed into uncertainty of characteristic flood level so as to analyze probability distribution of characteristic flood level. One hundred and twenty-eight years of daily runoff data from 1882 to 2009 have been used to test the method. The results indicate that the proposed method can make an effective derivation of probability distribution of characteristic flood level by considering hydrologic uncertainty. Reliability of hydrologic time series and original checking of flood levels (180.4 m) increases with the increasing value of n. Reliabilities of the hydrologic time series and checking of flood levels are 93.19% and 99.17% under the sample size 120, respectively. The research results will provide