抄録
Climate change alters the hydrological cycle in river basins and threaten the future surface water resources under the stress of the rapid urbanization and population growth in many cities. Haji Dam, located upstream of the Gono River in Chugoku region in Japan, is a very important green energy resource for urban water supply, hydropower generation, irrigation and flood controls. Therefore, the assessment of the projected inflow and capacity under present operating rule is very important for the multi-purpose reservoir. As a result, the estimated maximum 100-year probable rainfall will surplus at least 5 % in the whole river basin as well as the approximately 35 -60 mm surcharge in July and +5 to +20 mm extra in September will fall east, west and middle of the basin in near future. Finally, the increasing trend is significant with 50 m3/sec/year in the annual basic and around 100 to 150 m3/sec/month during the wet season. It requires to change the release ratio before and during the flood if the current flood control allocation wants to keep constant and reservoir water level continuously retains under the flood alarm level for reservoir safety. Moreover, the present operating rule assures the enough capacity after flood season or from September for multi-purposes.
