How isotopic fractionation of snowmelt affects hydrograph separation

• Published in: Hydrological Processes
• Main Authors: Taylor, Susan, Feng, Xiahong, Williams, Mark, McNamara, James
• Format: Article in Journal/Newspaper
• Language: English
• Published: Wiley 2002
• Subjects: Arctic; Ice; permafrost; Alaska
• Online Access: http://dx.doi.org/10.1002/hyp.1232; https://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1002%2Fhyp.1232; https://onlinelibrary.wiley.com/doi/pdf/10.1002/hyp.1232

Abstract We present the isotopic composition of meltwater samples from four seasonal snowpacks: a warm, maritime snowpack in California; a temperate continental snowpack in Vermont; a cold continental snowpack in Colorado; and an Arctic snowpack in Alaska. Despite the very different climate conditions the δ 18 O of meltwater from all four snowpacks increased as melting progressed. This trend is consistent with theoretical results that model isotopic exchange between water and ice as meltwater percolates through a snowpack. We have estimated the systematic error in the hydrograph separation if the isotopic composition of a snow core were used in place of that of meltwater. Assuming no error in the old water or stream water values, the error in the new water fraction depends on: (1) the isotopic difference between the snow core and the old water; (2) the isotopic difference between the snow core and the meltwater; and (3) the new water fraction contributing to the stream flow during a spring melt event. The error is large when snowmelt contributes a dominant fraction of the stream flow, which may be expected where infiltration of snowmelt is limited (e.g. permafrost, urban areas). A particular challenge will be how to incorporate the changes in isotopic composition of meltwater measured at a point into hydrograph separation models conducted at the watershed scale. Published in 2002 by John Wiley & Sons, Ltd.