Comparison of methods for separating flood frequency of reservoir by sub-seasons

Abstract. The development of separate flood frequency distributions for different sub-seasons within a year can be useful for protection, storage and utilization of flood flows for the reservoir operation management. This paper applies conventional statistical method, fractal method and the mixed Von Mises distribution to the separation of flood sub-seasons for inflows to Hongfeng Reservoir in China. Design floods are found for different sub-seasons, along with flood control levels for flood regulation. The flood season is divided into four sub-seasons using the fractal method: the pre-rainy season (May), main-flood season (June and July), late-flood season I (August) and late-flood season II (September). The mixed Von Mises distribution method accounts for the general flood pattern and combines August and September as one late-flood season, for three sub-seasons with different frequency distributions. The flood regulation calculation results show little difference between the control water levels in August and September, so the two can be combined into one period.