Watershed-scale water quality impacts of riparian forest management

The SPANS (SPatial ANalysis System) Geographic Information System (GIS) and the Georgia Landcover Database were used to identify land use within the 333 km2 Little River Research Watershed of Georgia and to perform a variety of spatial analyses with the purpose of determining the water quality impact of riparian forest management within the watershed. The watershed contains a dense dendritic stream network, with approximately 54% of a 30 m riparian buffer on either side of all streams of second order or larger currently in forest cover. Approximately 60% of the upland is in some type of agricultural production. GIS analyses were used to extrapolate field-scale measurements on riparian forest nonpoint-source-pollution nutrient buffering capacity to the watershed-scale, and to evaluate the water quality impact of three increasing deforestation and three increasing reforestation riparian forest management scenarios. Nitrogen (N) and phosphorus (P) loadings at the watershed outlet could potentially increase by 16.7 and 9.5%, respectively, under a 50% riparian buffer deforestation scenario. Decreases in potential N and P loadings of 13.2 and 7.4%, respectively, could potentially occur under a 50% reforestation scenario. Fragmentation analysis of the riparian buffer indicated that only six blocks of riparian forest at least 2 km long remained in the entire watershed, confirming the fragmented state of the riparian forest.