Identified model parameterization, calibration, and validation of the physically distributed hydrological model WASH123D in Taiwan

Typhoon-induced flood and inundation are among the major natural disasters in Taiwan. To understand and mitigate these hydrological hazards, adequate modeling tools on watershed scales are necessary. This paper describes the calibration and validation of a river basin using a physics-based watershed model, WASH123D. The key objective is to demonstrate the enable technology of using physics-based watershed models rather than lump parameter or statistical models. An ad hoc calibration procedure based on our understanding of the target river basin was employed. Systematic parameter optimizations would be addressed in subsequent studies. The Lanyang Creek basin situated in northeastern Taiwan is chosen as the study area. Two years of data (2004 and 2005) were used to examine event-based responses and long-term predictions. Both parametric work and hydrology issues are discussed. The simulated magnitude and time lag of the flow peak are compared with the observation. The results indicate that the proposed model could indeed provide Taiwan Typhoon and Flood Research Institute with a useful protocol for research, prediction, and forecast related to watershed hydrology.