Organic matter transport in New York City drinking-water-supply watersheds

350 210 Stroud Water Research Center

Kaplan, L.A., J.D. Newbold, D.J. Van Horn, C.L. Dow, A.K. Aufdenkampe, and J.K. Jackson. 2006. Journal of the North American Benthological Society 25:912–927.



Organic matter (OM) in streams that provide drinking water is a potential energy source for bacterial regrowth in distribution systems and a precursor for disinfection byproducts. Baseflow concentrations of OM were measured over a 3-y period in 60 streams divided evenly between water-supply regions east and west of the Hudson River (EOH or WOH) in New York State. A baseline of OM concentrations in the 2 regions was generated, and land use/cover variables were related to those baseline concentrations. Dissolved organic C (DOC), biodegradable DOC (BDOC), and particulate OM (POM) reflected regional differences in land use and point-source discharges. Three-year mean concentrations for these variables and for total organic C (TOC) were significantly lower in the WOH than in the EOH by factors of 1.5 to 2.3. Size fractionation of POM showed similarities between regions with >70% of particles in the 0.5- to 10-μm size class. DOC made up most of the TOC in both regions, and DOC:POC ratios ranged from 1.7 to 54.4. Stepwise multiple linear regressions revealed that agriculture and forest land uses explained most of the variation in OM concentrations in the WOH, whereas wetlands and point-source discharges, primarily associated with wastewater treatment plants, explained most of the variation in OM concentrations in the EOH. Despite the potential problems from OM for drinking water quality, OM is a natural and important component of stream ecosystems, so its total elimination from watersheds is neither advisable nor possible. Our data from watersheds in the WOH region with high percentages (>97%) of forested land use and from small to mid-sized watersheds in the EOH with no point-source discharges provide lower limits for OM concentrations and targets for best management practices.