Using DOC to better understand local hydrology in a subarctic watershed

The goal of this study was to gain a better understanding of the hydrology of a permafrost affected watershed using analyses of DOC. DOC from water samples collected in the Caribou–Poker Creeks Research Watershed (CPCRW) was analyzed by several techniques, including pyrolysis-gas chromatography/mass spectrometry (py-GC/MS). Results showed that the ratio of aromatics to nitriles served as a useful indicator of groundwater and runoff contribution to streams. In general, as the conductivity of water samples decreased, the DOC concentration and the ratio of aromatics to nitriles increased. Other analyses showed that as the conductivity increased, labile DOC (LDOC) decreased. The LDOC results were consistent with pyrolysis-GC/MS results. The results showed that organic matter in baseflow can have different aromatic to nitrile ratios, depending on the source and pathway to the stream. In a permafrost watershed were flowpaths are complicated by frozen ground, DOC characteristics proved to be a useful indicator of groundwater entering the watershed from outside the topographic boundary.