Influence of vegetation on water isotope partitioning across different northern headwater catchments

Wednesday, 17 December 2014
Rachel S Gabor1, Doerthe Tetzlaff1, James M Buttle2, Sean Kevin Carey3, Hjalmar Laudon4, Carl P J Mitchell5, James P McNamara6 and Chris Soulsby1, (1)University of Aberdeen, Aberdeen, United Kingdom, (2)Trent University, Peterborough, ON, Canada, (3)McMaster University, Hamilton, ON, Canada, (4)SLU Swedish University of Agricultural Sciences Umeå, Umeå, Sweden, (5)University of Toronto, Toronto, ON, Canada, (6)Boise State Univ, Boise, ID, United States
The hydrology of high latitude catchments is sensitive to small changes in temperature, and likely to be impacted by changes in climate. Vegetation water usage can play a large role in catchment hydrologic pathways, affecting how water is stored, released, and partitioned within a landscape. Thus a better understanding of how vegetation impacts water partitioning in northern catchments can help us understand how climate change will impact high-latitude hydrology.

As part of the VeWa project, five catchments were chosen between 44oN and 64oN in Europe and North America, to compare the role of vegetation in the movement of water across northern landscapes. These catchments vary in aspect as well as extent of snowpack and their vegetative landscapes include heather moorland, coniferous and deciduous forests, mixed grass, and tundra landscapes. Importantly, all the catchments have records of stable isotopes in different waters of the system. An initial comparison of the water isotopes in these catchments demonstrates variation between the catchments, with the lower latitude sites showing more fractionation suggestive of evapotranspiration. While all catchments show a depletion of heavy isotopes in the spring, the depletion is most evident in catchments with a heavier snowpack. The vegetative growing season during the summer months shows the greatest impact of evapotranspiration on isotopes, indicating that an increased summer in a warmer climate would likely alter water partitioning and storage dynamics in these regions.