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Advances in Meteorology
Volume 2014 (2014), Article ID 581756, 11 pages
Research Article

Uncertainty Assessment: Reservoir Inflow Forecasting with Ensemble Precipitation Forecasts and HEC-HMS

Taiwan Typhoon and Flood Research Institute, National Applied Research Laboratories, 11 F, No. 97, Section 1, Roosevelt Road, Zhongzheng District, Taipei 10093, Taiwan

Received 3 June 2014; Revised 1 August 2014; Accepted 4 August 2014; Published 27 August 2014

Academic Editor: Hann-Ming H. Juang

Copyright © 2014 Sheng-Chi Yang and Tsun-Hua Yang. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


During an extreme event, having accurate inflow forecasting with enough lead time helps reservoir operators decrease the impact of floods downstream. Furthermore, being able to efficiently operate reservoirs could help maximize flood protection while saving water for drier times of the year. This study combines ensemble quantitative precipitation forecasts and a hydrological model to provide a 3-day reservoir inflow in the Shihmen Reservoir, Taiwan. A total of six historical typhoons were used for model calibration, validation, and application. An understanding of cascaded uncertainties from the numerical weather model through the hydrological model is necessary for a better use for forecasting. This study thus conducted an assessment of forecast uncertainty on magnitude and timing of peak and cumulative inflows. It found that using the ensemble-mean had less uncertainty than randomly selecting individual member. The inflow forecasts with shorter length of cumulative time had a higher uncertainty. The results showed that using the ensemble precipitation forecasts with the hydrological model would have the advantage of extra lead time and serve as a valuable reference for operating reservoirs.