Comparative modelling of two catchments in Taiwan and England

A comparative modelling of two catchments of similar sizes in Taiwan and England is described. In the study, despite its success in many Taiwanese catchments, including the Yan-Shui Creek catchment in this study, the distributed model GBDM was initially found unsuitable when applied to the Brue catchment in South West England. However, the simulations are much better after revising the infiltration capacity. Further exploration reveals several interesting findings. (1) The infiltration computation based on soil characteristics and classifications is unreliable in the model. Other factors, such as climate, farming practice and vegetation cover, could have a much more significant impact. (2) The application of the GBDM far away from its 'home country' unveils a possible weakness of such a model for being 'underfitting'. The fact that an 'adjustment factor' added in the model could improve both its calibration and validation may indicate that there is a room to improve the GBDM structure for catchments outside Taiwan. (3) The study illustrates the difficulty in creating a universal distributed model that could suit all possible hydrological environments, under the constraint of model parameter parsimony to minimize the 'equifinality' problem.