IMPACT OF RIPARIAN FOREST BUFFERS ON AGRICULTURAL NONPOINT-SOURCE POLLUTION

A field monitoring study of a riparian forest buffer zone was conducte d to determine the impact of the riparian ecosystem on reducing the co ncentration of agricultural nonpoint source pollutants. Groundwater sa mples were collected from 20 sampling locations between May 1993 and D ecember 1994, and analyzed for NO3-N, PO4, and NH4-N. Statistical anal yses such as Friedman's test, cluster analysis, cross correlation anal ysis and Duncan's test were performed for the nutrient data. The study showed that the riparian buffer zone was effective in reducing nitrat e concentrations originating from upland agricultural fields. Instream nitrate concentrations were 48 percent less than those measured in th e agricultural field. Reductions in concentrations in sampling locatio ns at the wetland edge ranged from 16 to 70 percent. The mean nitrate concentrations in forested hill slope were 45 percent less than concen trations in a well located in an upland agricultural field. Meanwhile, the concentrations of phosphate and ammonia did not follow any specif ic spatial trend and were generally higher during the summer season fo r most sampling locations.