Contribution of icing ablation to streamflow in a discontinuous permafrost area

Icings, present in many small streams in the discontinuous permafrost environment, alter the seasonal water balance by redistributing a component of flow from the winter to the spring. Icing ablation continues to contribute to streamflow after the disappearance of the snowpack and constitutes an additional source of runoff. The temporal variability and significance of icing ablation to streamflow were examined with a combined water balance and isotope study in a tributary of Manners Creek, Northwest Territories. Icing accounted for 20% of the surface water available for melt. Over the spring study period, icing ablation accounted for 6% of total streamflow, while the total surface-water flux provided 8%. Shallow subsurface flow, which consisted of infiltrated snow meltwater and premelt groundwater, contributed the most to streamflow. At the end of the melt period, icing ablation was the only source of surface runoff to the stream and was similar in magnitude to the estimated evapotranspiration loss. Comparison with other studies revealed that on a regional scale, the hydrologic role of icing ablation is controlled by the interaction between the timing of melt, the magnitude of groundwater recharge, the spatial extent of permafrost, and the depth of seasonal frost.