Developing Drought Early Warning Index for Water Supply of Tsengwen Reservoir in Southern Taiwan

F.N.-F. Chou and B.P.T. Chen (Taiwan)


Drought early warning index, reservoir, regression.


The upcoming drought usually reveals vague sign under hydrologic uncertainty. The appropriate moment of enforcing water supply restriction always blunders away after bearing the impact of drought. If the early warning of drought can be anticipated, well preparation of fallow to the agricultural lands can be arranged. This paper proposed an approach to develop drought early warning index (DEWI) for southern Taiwan to detect the drought in advance for setting up proper plans to mitigate the water shortage impact. The DEWI was developed in this paper, using expected deficit of reservoir-based water supply system. In Taiwan, the hydrologic year starts from June which is the wet season and it ends on May which is dry the season. So, the simulation in this paper for the water shortages was started from available initial storages of a reservoir of current period (June) to till the end of the dry season (May). To cope with the actual water supply process, this simulation encountered the initial storage and reservoir inflow series only. A variety of deficits could be realized in different hydrologic years. A linear regression model was then established to estimate the DEWI with selected factors which deduced from available rainfall, reservoir inflow and storage data. With validation tests at Tsengwen-Wushantou reservoir system, this DEWI provided excellent performance in adopting proper mitigation policy at the end of the wet season.

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