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atoMulti-purpose reservoirs, which are operated for both of flood control and water use purposes, play an important role in water resources management. Consideration of operational hydrological predictions can potentially provide an improvement in operations of a multi-purpose reservoir by allowing adaptive operation according to the predicted future condition of the reservoir and the target river basin. In this paper, a decision support tool for flood control operation of a multi-purpose reservoir considering middle-range operational ensemble prediction is proposed. One-week Ensemble Forecast of precipitation, which is provided by Japan Meteorological Agency with 51 ensemble members for the coming eight days, is considered to support decision making for conducting preliminary water release from the reservoir to secure empty storage capacity for flood control. Firstly, ensemble streamflow prediction for the coming one week is estimated from One-week Ensemble Forecast of precipitation using Hydro-BEAM, a distributed rainfall-runoff model. Reservoir states such as inflow or storage volume are then estimated for each ensemble member of streamflow prediction to decide the amount and the timing of the preliminary release for flood protection. Chance and the expected amount of recovery in water storage at the end of the flood event is also calculated for each scenario of reservoir operation to estimate the impact of the flood control operation on water supply for the long term. Trajectories of the predicted streamflows and expected reservoir states are shown to reservoir managers with the possible flood damages and the potential water deficits for the decision support of operation. The amount and the timing of the preliminary release are finally decided with consideration of expected situations and their variance taking uncertainty into account. The proposed method and the tool were applied to multi-purpose reservoirs in Japanese river basins, demonstrating their effectiveness and applicability in the real-time operation of multi-purpose reservoirs.


Session S8-01, Flood Control through Use of Water Reservoirs I



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