Integration of Extended-range and Long-term Rainfall Forecasts towards Reservoir Inflow Forecasting

This work integrated the calibrated ECMWF’s extended-range (1 ~ 30 days ahead) and the CWB1T1’s seasonal (1 ~ 6 months ahead) rainfall forecasts as the input of the HBV-based hydrological model for performing the inflow forecasting at the key reservoirs in Taiwan. The reservoir inflow forecasting can facilitate to predict the future reservoir storage and support decision-making during the drought period. In the face of short-term rapidly changing weather conditions (such as the mei-yu front and typhoon), the extended rainfall forecasts generally perform more precisely than the seasonal rainfall forecasts during the same forecasting period. This work used the calibrated (downscaled and bias-corrected) ECMWF’s extended-range rainfall re-forecasts (2000 ~ 2019) as the input of the HBV-based hydrological model for forecasting the reservoir inflows. The results reveal that the reservoir inflow re-forecasts by calibrated ECMWF’s extended-range rainfall re-forecasts have a better performance than those by the CWB1T1’s seasonal rainfall re-forecasts for the 1 ~ 30 days lead time. Therefore, the integration of extended-range (1 ~ 30 days ahead) and seasonal (2 ~ 6 months ahead) rainfall forecasts for reservoir inflow forecasting can simultaneously reflect the short-term weather conditions as well as the long-term trend of the weather outlook. © 2023, Taiwan Agricultural Engineers Society. All rights reserved.