HR: 0800h
AN: H51H-0875    [Abstracts]
TI: Ecohydrological Controls on Intra-Basin Alpine Subarctic Water Balances
AU: * Carey, S K
EM: sean_carey@carleton.ca
AF: Department of Geography and Environmental Studies, Carleton University, 1125 Colonel By Dr., Ottawa, ON K1S 5B6, Canada
AU: Ziegler, C M
EM: cziegler@connect.carleton.ca
AF: Department of Geography and Environmental Studies, Carleton University, 1125 Colonel By Dr., Ottawa, ON K1S 5B6, Canada
AB: In the mountainous Canadian subarctic, elevation gradients control the disposition of vegetation, permafrost, and characteristics of the soil profile. How intra-basin ecosystems combine to control catchment-scale water and biogeochimcal cycling is uncertain. To this end, a multi-year ecohydrological investigation was undertaken in Granger Basin (GB), a 7.6 km² sub-basin of the Wolf Creek Research Basin, Yukon Territory, Canada. GB was divided into four sub-basins based on the dominant vegetation and permafrost status, and the timing and magnitude of hydrological processes were compared using hydrometric and hydrochemical methods. Vegetation plays an important role in end-of-winter snow accumulation as snow redistribution by wind is controlled by roughness length. In sub-basins of GB with tall shrubs, snow accumulation is enhanced compared with areas of short shrubs and tundra vegetation. The timing of melt was staggered with elevation, although melt-rates were similar among the sub-basins. Runoff was enhanced at the expense of infiltration in tall shrub areas due to high snow water equivalent and antecedent soil moisture. In the high-elevation tundra sub-basin, thin soils with cold ground temperatures resulted in increased surface runoff. For the freshet period, the lower and upper sub-basins accounted for 81 % of runoff while accounting for 58 % of the total basin area. Two-component isotopic hydrograph separation revealed that during melt, pre-event water dominated in all sub-basins, yet those with greater permafrost disposition and taller shrubs had increased event-water. Dissolved organic carbon (DOC) spiked prior to peak freshet in each sub-basin except for the highest with thin soils, and was associated with flushing of surficial organic soils. For the post-melt period, all sub-basins have similar runoff contributions. Solute and stable isotope data indicate that in sub-basins dominated by permafrost, supra-permafrost runoff pathways predominate as flow pathways are confined above the permafrost aquitard. In contrast, lower elevation zones supply runoff via deeper subsurface flow pathways with increased levels of dissolved solutes. With regards to DOC, sub-basins dominated by permafrost supply the bulk of DOC to the stream because of near-surface pathways. Results highlight the importance of vegetation, the soil profile and frozen ground status in controlling hydrological and hydrochemical fluxes. Future changes in vegetation, which are occurring rapidly in the subarctic, are expected to have a large impact on the hydrology and biogeochemistry of these systems.
DE: 0702 Permafrost (0475)
DE: 1813 Eco-hydrology
DE: 1823 Frozen ground
DE: 1863 Snow and ice (0736, 0738, 0776, 1827)
DE: 1876 Water budgets
SC: Hydrology [H]
MN: 2007 Fall Meeting