The Feitsui reservoir is a major water supply source for more than five million people in Northern Taiwan. The reservoir water quality has been good, but is threatened by eutrophication due to excessive nutrient input and siltation due to sediment loads. Recently, the water authorities in Taiwan have made considerable efforts to devise strategies using watershed conservation practices for the protection of Feitsui reservoir water quality. The control of non-point source pollution (NPS) represents one of the major strategies and the use of best management practices (BMPs) is under careful consideration. The objective of this study was to assess the effectiveness and cost of a full Feitsui watershed implementation of riparian buffer strips and other appropriate conservation practices. Based on the use of watershed simulation models and a statistical relationship between pollution reduction rate and the width and slope of a buffer strip, a methodology for the planning and design of riparian buffer strips was addressed. Data from field experiments were used to calibrate the coefficients of the regression equations. Several planning scenarios were evaluated by means of cost-benefit analysis coupled with net present value method. Data on local construction and maintenance costs for the selected design and location of buffer strips were used in the analysis. Based on several cost-benefit analyses, the scenario for installing buffer strips with 30 m width and 5% slope along both sides