Modeling the width and placement of riparian vegetated buffer strips: a case study on the Chi-Jia-Wang stream, Taiwan.

Improper agricultural activities seriously affect water quality. It is very important to control agricultural nonpoint source pollution along the Chi-Jia-Wang Stream to protect the habitat of land-locked salmon (Oncorhynchus masou formosanus), one of the endangered species in Taiwan. Riparian vegetative buffer strips are used to intercept wastewater, surface runoff and groundwater flow to reduce pesticide, nutrient and other organic pollutants before they enter the stream. This study estimates the suitable width for vegetated buffer strips in the riparian zone along the stream using a geographic information system and an index model. The groundwater in the study area is easily contaminated by pollutants due to the high hydraulic conductivity in the riparian zone of the Chi-Jia-Wang Stream. After comparing simulations on selected 46 kinds of selected pesticides, the maximum safety depth of Fenarimol was estimated. A wider Fenarimol vegetated strip is needed as a buffer zone to ensure pollution control effectiveness. Simulation results can provide a preliminary evaluation for the soil or groundwater pollution caused by pesticides, but the actual influences require onsite data verification.