APPLICABILITY OF JMA MSM AND GSM FOR PRE-RELEASE AT MULTI-PURPOSE DAMS IN JAPAN

Abstract

 We assessed how accurate the current rainfall forecast was in decision making for pre-release at multipurpose dams in Japan, as the use of numerical rainfall forecast for pre-release is becoming more active at dams nationwide. For this analysis, inflow was calculated by using a tank model whose parameters were proposed based on geological features, and the regular controls and quantities of each dam were also incorporated based on our survey. After that, we evaluated the capacity to be secured and time required for prerelease which were predicted at different forecast initial times in the most recent disasters. As a result, there were uncertainties such as false alarms of the capacity to be secured and large range among forecast updates. On the other hand, under the flood control capacities and downstream flow capacities of target dams, there were few cases where it is difficult to recover the water use capacity, and the forecasts were effective information for reducing the degree of emergency spillway gate operation.