Growing switch-grass in a riparian buffer zone can be one of future best management practices in water resource protection.Switch-grass requires no fertilizers and less land and water.It was recently found to be a good source of biomass.In this study, Soil and Water Assessment Tool (SWAT) model was applied to a watershed to examine the effectiveness of buffer zones of switch-grass in reducing pollutants (nitrate) from crop fields to rivers or lakes.Numerical experiments were conducted to identify potential sub-basins in the watershed that have high impact and to assess the effects of buffer size on pollution reduction.Simulation results showed that a buffer zone having 10%-50% of the sub-basin area could lead to 55%-90% reduction in nitrate loading to rivers.The combination of buffer zone and switch-grass for bio-energy can become an emerging environmentally beneficial practice and economically feasible solution to energy problem.The results of this study can assist in cost-benefit analysis and evaluation of growing switch-grass for bio-fuel in riparian buffer zones and decision-making in best management practices for water quality assessment and envirorumental protection.