MODELING STREAM SALT CONCENTRATION IN A SOUTHERN APPALACHIAN URBAN HEADWATER

Road salt is used in winter to clear roadways of snow and ice in high latitude and altitude regions. This practice introduces salt into the environment that sustains elevated electrical conductivity levels that damage ecosystems and lead to a decline in aquatic species. Dating back as far as 2006 electrical conductivity measurements, as well as discharge measurements, have been recorded in Boone Creek, a 1.8 km second-order headwater located in the southern Appalachian Mountains of Boone, North Carolina. This research applies a linear reservoir model based on mass balance of water and salt to investigate long term (60 year) salt retention and transport in this mountainous headwater watershed. Yearly road salt input is based on application rates collected from North Carolina Department of Transportation, Town of Boone Public Works Center, and Appalachian State University Physical Plant; the number or snow events; and road mileage estimated in ArcGIS. Yearly recharge is based on annual precipitation data collected by the National Climatic Data Center with which a runoff ratio was applied. Storage volume and the response factor are assumed to be constant over time. This linear reservoir model is calibrated against the discharge and electrical conductivity data collected from the field. The preliminary results indicated that the model simulated the annual discharges reasonably well, while underestimated the stream salt concentrations slightly. The further step is to apply this calibrated model to estimate residence time of road salt in the watershed and predict how stream salt concentration responds to changes in road salt application and climate in the future.