EFFECTS OF ROAD SALT APPLICATION ON WATER QUALITY IN A MOUNTAINOUS HEADWATER STREAM

The population of Boone, North Carolina, USA has increased 27.1% since 2000 and almost doubles during the school year when a local university, Appalachian State University, begins classes. As the population increases, Boone continues to urbanize to accommodate the population growth, including increasing impervious surfaces. Due to its location in northwestern North Carolina in the Blue Ridge Mountains, winter conditions are common for the region and the combination of an increasing population in a snowy region requires the use of road salt. Road salt application creates abnormal salinity levels for Boone Creek, a headwater stream that runs along urbanized sections of Boone. In this urbanized area, a large area of impervious surfaces creates more locations that require road salt application, which mostly drain into the stream.

The 1.5 km study reach is divided into upstream and downstream regions where the amount of impervious surfaces increases from 13.7% to 24.3%. A total of three loggers are monitoring salinity: one upstream of campus (JS) has been recording since mid-October 2014. Another, approximately mid-campus (VG) has been recording since July 25, 2014. The last logger, located at the end of campus (PB), has been recording since mid-October 2014. During winter precipitation events, salinity readings from Boone Creek decrease as the water is diluted from initial precipitation; however, meltwater eventually transports the road salt to local streams, increasing the salinity on average by approximately 3.200 PSU for an average of 18.72 hours before it returns to normal conditions. The mean salinity for the JS, VG and PB sites are 0.191 PSU, 0.237 PSU, and 0.226 PSU, respectively. Salinity levels measured in 2006 and 2007 are half of the current measurements, suggesting increasing salinity levels in baseflow. We attribute the increasing salinity of groundwater in the ASU and Town of Boone area to rising rates of application of road salt. This salt is supplied rapidly during winter meltwater runoff, but over longer time scales is being supplied on a steady basis through baseflow. These results are important for assessing effects of increasing salinity on water quality and aquatic life in Boone Creek.