Releasing water rationing based on the cross-scale weather forecast: A case study of Taoyuan area in 2011

Usually, water rationing against drought period is terminated after a significant amount of rainfall in the watershed of reservoirs. However, based on the historical weather records, it seems that the rationing can be terminated earlier. In this study, we employed the CWB monthly weather outlook, CWB seasonal weather outlook, and climatological weather forecast to determine the time of terminating water rationing for different hit-rates of weather forecasts. We used Shimen reservoir and the drought event in 2011, phase 1 water rationing had executed from March 1 to June 30, as our case study. Based on the reservoir inflow records in 2011, the rationing can be terminated as early as the middle May (14th ten-day). According to the weather outlooks (seasonal rainfall outlook) with the accuracy of 100%, we make decision in the early March, that the normally supply can start from middle May. With the accuracy of seasonal rainfall outlook of 60%, in the middle and late April, the termination of rationing in middle May can be estimated. Based the weather forecasts with current forecast system in Taiwan, the water can be supplied normally 1 month ahead.