The Neversink Reservoir watershed, an important contributor to New York City’s drinking water supply, was sampled over the summer of 2022 to investigate the spatiotemporal variability of dissolved organic matter (DOM) and disinfection byproducts (DBP) potential (e.g., dichloroacetic acids (DCAAs), trichloroacetic acids (TCAAs), trihalomethane (THM)) and their relationship to geomorphic features (e.g., topographic indices (TI), drainage area, and runoff patterns) under baseflow conditions. Eleven sub-basins were monitored for fluorescent DOM, dissolved organic carbon (DOC), fluorescence index, specific ultraviolet absorbance at 254 nm (SUVA), turbidity, and DBP formation potential. Results showed that DOM was primarily aromatic, chromophoric, and mostly derived from terrestrial sources with DOC means ranging spatially from 0.83 to 1.38 mg/L. DBP potential concentrations varied more spatially (43 to 157 μg/L for TCAA) than over time (23.9 to 48 μg/L for TCAA at the Main Branch). Drainage area and topographic index explained differences in DOC means (R2 = 0.41, R2 = 0.87) and SUVA means (R2 = 0.48, R2 = 0.59) across sub-basins and had moderate explanatory power for specific DBP precursor concentrations (R2 = 0.05 to R2 = 0.49). TI showed the strongest relationship with DOC (R = −0.93) and SUVA (R = −0.77) with an inverse relationship that has not been commonly observed but is present in similar hardwood forested watersheds.
Shakhawat et al. (Wed,) studied this question.