The purpose of this study is to assist Taiwan Environmantal Protection Administration (EPA) in reviewing the environmental impact assessment (EIA) reports regarding the water quality modeling. Four main tasks are conducted to provide technological support in examining the results of water quality modeling which was used in the assessment of surface water quality. The tasks include: (a) summarizing the results of modeling application of the four models (HSPF/BASINS, SWMM, WASP, and QUAL2K) which were applied in the EIA cases, and a model user manual is prepared based on EIA cases, (b) reviewing at least 20 EIA reports, (c) developing a heavy metal TMDL, and (d) hosting workshops to discuss the water quality models. Twenty EIA cases were evaluated during this study. One of the EIA cases were assessed by the QUAL2K, seven by the simple dilution model, but twelve were not assessed by any models. Two EIA cases were followed up, and comments on the EIA cases were provided during the scoping meeting. The WASP was applied to develop a heavy metal TMDL. The results showed that the Copper (Cu) has to be reduced to meet the critical water quality under Q75 and Q50 low flow condition. The scenarios of Cu loading reductions were presented for the Cu TMDL developments in Nankan River. Besides, the parameters of the water quality models are summarized for future application. During this study, the parameters of the four models were collected based on the EIA cases. For the HSPF/BASINS, the parameters of Toucian Creek were collected. For the QUAL2K, Dahan Creek and Da-an river was collected. For the WASP, Wu Creek and Juoshuei River was collected. For the SWMM, Da Pu Mei drainage was collected. Finally, several suggestions for further investigation are provided. This study recommends that government agencies should work with institute to revise the modeling guidelines or model implementation for applications in EIA cases. Moreover, the co-working institute can play a critical role in archiving models and data, maintaining and upgrading them for future applications. The modeling workshops should take place frequently to emphasize on modeler education.

Water Quality Model, Environmental Impact Assessment, Technical Guideline