TURBIDITY AND RAINFALL IN A SMALL WATERSHED IN NORTHEAST TENNESSE

Excess turbidity is a cause of surface water impairment for fish and aquatic life, and has been shown to be positively correlated to pathogen impairment. Turbidity in Tennessee streams is of special concern as sedimentation is the second ranking cause of surface water impairment after Escherichia Coli, with 9934.15 km (6,172.8 miles) of sediment impaired streams reported in the state for 2012 (representing 21.7% of assessed waters). While the correlation between turbidity and rainfall is well established, previous research has focused on longer timescales and therefore the relationship between turbidity and rainfall at the hourly timescale is poorly understood. During a 14-day period in Fall 2015, a data-logging rain gauge was deployed, and n=337 hourly water samples were collected from Sinking Creek (HUC14-06010103000325) at Jacob’s Nature Park in Johnson City, Tennessee. The collection site was 365 meters (1,200 feet) downstream from a sediment impaired tributary (Catbird Creek). Two small rainfall events occurred during the study period, and turbidity was compared to precipitation accumulation and intensity using cross-correlation. A small statistically significant Spearman correlation between precipitation accumulation and turbidity exists at lags of 2 through 8 hours following a rainfall event (r=0.127 to 0.203, p<0.05). Similarly, a small statistically significant Spearman correlation exists between precipitation rate and turbidity at lags of 2 through 8 hours following a rainfall event (r=0.123 to 0.2, p<0.05). Linear regression models on turbidity at various lags explained only 4% of the variability in turbidity.