Effects of Reservoir Storage Reallocation Considering Prior Release Operation Based on Long-Range Ensemble Rainfall Forecast

More integrated operation of multi-purpose reservoirs, which have storage capacities for multiple operation purposes such as flood control, water supply or power generation, is important for more effective management of water-related disasters as well as increase in renewal energy production for climate change mitigation. In this study, efficacy of storage reallocation of a multi-purpose reservoir was investigated when introducing prior release operation considering operational long-range ensemble hydrological forecast. One-week Ensemble Forecast of precipitation, which is provided by Japan Meteorological Agency (JMA) with their global ensemble prediction system (GEPS), was employed to make a decision for prior release operation. Advantages and risks of prior release operation with a multi-purpose reservoir in flood management, water supply and power generation were investigated considering potential scenarios of reservoir storage reallocation through the simulation of long-term reservoir operation. As a result of case studies applied to the simplified Hiyoshi Reservoir system in the Yodo River basin, Japan, it was shown that the reservoir can gain increased capability to control large-scale floods with limited impacts on hydropower production by introducing prior release operation based on long-range ensemble hydrological forecast with reservoir storage reallocation when hydropower production was susceptible to the reservoir storage level.