| Summary: | Application of novel hydrological methods for assessing runoff generation in remote northern landscapes is necessary to identify the consequences of climate variability and change. In Old Crow Flats, a lake‐rich thermokarst landscape in northern Yukon Territory (Canada), local land users have concerns over the effects of recent lake drainage and fluctuating river discharge on their traditional way of life. In the absence of hydrometric stations, we evaluate the utility of isotopic monitoring of the lower Old Crow River, which is fed by several tributaries and drains the flats, for tracking runoff generation. Isotopic ‘snapshots’ obtained from 2007, 2008 and 2009 during the recession limb of the spring freshet hydrograph provided characteristic patterns of deuterium excess (d‐excess) along the Old Crow River. River sampling in June 2007 captured a pulse of evaporatively enriched lake water originating from a rainfall‐triggered catastrophic lake drainage event, identified by decreased d‐excess values. June 2008 was marked by negligible variability in d‐excess values along the same reach of the river, consistent with minimal export of lake waters after a winter of below‐normal snow accumulation. In contrast, rising d‐excess values along the study reach in June 2009 indicate enhanced rainfall‐generated runoff. River isotope sampling could be used to monitor spatial and temporal variability in runoff generation processes in the Old Crow Flats and other northern lake‐rich landscapes drained by rivers. Copyright © 2014 John Wiley & Sons, Ltd.
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