SPATIAL TRENDS IN STREAM CONDUCTIVITY AND POTENTIAL SOURCES IN A SMALL RURAL WATERSHED

Road salt has negative effects on the surrounding environment, and is linked to groundwater contamination and declines in macroinvertebrate populations. The mechanisms for movement and persistence of chloride from paved roads into nearby surface waters are not fully characterized. This project investigates first-order streams in a small, rural watershed in Buckfield, ME to better understand potential pathways for road salt contribution to nearby stream conductivity. The watershed is mostly forested with some periphery agricultural land, and is mostly underlain by till. State highway 217, where road salt is deposited during the winter, crosses five first order streams. Using a handheld meter, conductivity and water temperature data were collected along a transect from just upstream of the road through stream confluences downstream in July and August. Readings were taken in the stream channel, and seeps and tributaries near each channel. Elevated conductivity values were typically found immediately downstream of road crossings. Stream A appears to have elevated conductivity readings along the entire measured profile, with higher readings persisting downstream due to the increased interaction and proximal location to the road. Isolated elevated conductivity readings are also found away from the road in other streams such as C, D and E, which run perpendicular to the road. At these areas of lower slope and hundreds of feet away from the road, conductivity values in the stream channel proper increased, and elevated readings were found in small tributaries, seeps and springs discharging into the stream. Overall elevated readings are generally highest in the area proximal to and downslope of the road surface. Therefore there would appear to be a slow but steady, rise in concentration of road salt downslope and proximal to the road. This results in an asymmetric cross-sectional spatial distribution of conductivity across and downstream of the road crossing for each stream.