Specifications and Accuracy of Rainfall Forecast Required for Pre-Release at Multi-Purpose Reservoirs in Japan

Pre-release is the discharge from a reservoir before flood to enhance control capability. Its success depends on performance of rainfall forecasting. However, there little information regarding causal relationship between its and pre-release. Therefore, forecast required for pre-release at 326 multi-purpose reservoirs in Japan shown quantitatively this paper. In our analysis, was simulated based tentative forecasts made using observed data period 17 years (2006 2022) with some processing. Then, outputs were evaluated terms two risks: not avoiding emergency spillway gate operation no recovery water use capacity. The results five elements reached: (1) characteristics situations requiring pre-release, (2) length (3) spatial resolution, accuracy (4) amount, (5) position zone. For (1), nationwide typhoons or stationary fronts frequency four instances per year. (3), assuming perfect accuracy, current specifications Japan: 84 h more combined 5 km 20 resolution are generally effective themselves. (5), possible uncertainties amount zone needs be decreased by one digit operations, while excessive tends result