The main purpose of this project is to study the adequacy of the use of surface water quality model in environmental impact assessment (EIA), especially rivers or streams. The results are expected to improve the document quality of current EIA reports. The study process includes: (1) collection of various water quality assessment models and methods; (2) analysis of the differences and local feasibility of the models and methods; (3) design objective selection principles. Two-steps selection flow was established and expert consultation in persons and in documents was involved. In the first step of model selection, the candidate models are identified depend on its reliability, availability, and convenience, which are simple method, AGNPS, BASINS, ESTUARY, HSPF, PLOAD, QUAL2E/QUAL2K, SWMM, and WASP. But the practical applications of PLOAD in Taiwan is too less to be selected. Thus, eight models are resulted in the first selection. The second selection is to select the possible model for specific development cases. The pollution quantity and quality, the case location, category of final receiving waterbody, nonpoint source pollution and the tidal effects of cases are the five selection principles in the second step. In addition, a selection flow chart is designed to assist the selection process. If multiple models are finally resulted, people can make decision of model use according to the priority of selection principles. Otherwise, various models for different simulations are also recommended.

environmental impact assessment, river/stream water quality assessment models, model selection, experts consultation, technology guideline