Development of effective pre-release method for dams during super typhoons using long-term ensemble rainfall forecasts

Abstract

Against the background of increasing frequency of heavy rainfall due to climate change, an analytical approach to maximize the effective use of the reservoir from both flood control and water utilization was conducted. Simulations by applying statistical down-scaling method to the long-term ensemble rainfall forecast by ECMWF on a dam basin where a large inflow occurred during the Typhoon Hagibis in 2019 were shown. The results show that it is possible to use long-term ensemble rainfall forecasts to gain a temporal, stochastic understanding of total rainfall, required flood storage volumes, and recoverable reserves. Based on this understanding, a calculation method for setting release rates that correspond to effective pre-release start times and changes in rainfall forecasts in order to minimize both flood control and water service risks was proposed.