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

Table 1

Collected six typhoons’ historical data. The first three typhoons’ observed data, namely, Typhoon Fungwong, Typhoon Sinlaku, and Typhoon Jangmi, were used for model calibration and validation. The second three typhoons’ TAPEX ensemble quantitative precipitation forecasts, namely, Typhoon Morakot, Typhoon Saola, and Typhoon Soulik, were used for model application to provide the reservoir inflow forecast for the Shihmen Reservoir.

Typhoon	Year	TAPEX period; (land warning period*)	Track	Max. cumulative rainfall** (mm)
				24 h	48 h	72 h
Fungwong	2008	—; (7/27 2:30~7/29 11:30)	3	235.8	280.4	282.1
Sinlaku	2008	—; (9/12 5:30~9/15 20:30)	2	412.0	711.1	899.0
Jangmi	2008	—; (9/27 8:30~9/29 17:30)	2	317.2	369.2	404.4
Morakot	2009	8/6 8:00–8/8 2:00; (8/6 8:30~8/10 5:30)	3	265.0	413.3	466.7
Saola	2012	7/31 8:00–8/1 20:00; (7/31 20:30~8/3 14:30)	2	397.7	398.6	422.6
Soulik	2013	7/11 8:00–7/12 20:00; (7/11 20:30~7/13 23:30)	2	494.3	672.7	798.9

*The land waning period of typhoons was based on the Typhoon Database of Central Weather Bureau, Taiwan (http://rdc28.cwb.gov.tw/). Periods are MM/DD notation.
**Data from the Shihmen Reservoir Management Center (http://www.wranb.gov.tw/). Thiessen’s polygon method was used to calculate the average rainfall and maximum cumulative rainfall. Selected precipitation gauges and the corresponding weights of Thiessen’s polygon were listed in Table 3.