Abstract:Storage heterogeneity effects on runoff generation have been well documented at the hillslope or plot scale. However, diversity across catchments can increase the range of storage conditions. Upscaling the influence of small-scale storage on streamflow across the usually more heterogeneous environment of the catchment has been difficult. The objective of this study was to observe the distribution of storage in a heterogeneous catchment and evaluate its significance and potential influence on streamflow. The study was conducted in the subarctic Canadian Shield: a region with extensive bedrock outcrops, shallow predominantly organic soils, discontinuous permafrost and numerous water bodies. Even when summer runoff was generated from bedrock hillslopes with small storage capacities, intermediary locations with large storage capacities, particularly headwater lakes, prevented water from transmitting to higher order streams. The topographic bounds of the basin thus constituted the maximum potential contributing area to streamflow and rarely the actual area. Topographic basin storage had little relation to basin streamflow, but hydrologically connected storage exhibited a strong hysteretic relationship with streamflow. This relationship defines the form of catchment function such that the basin can be defined by a series of storing and contributing curves comparable with the wetting and drying curves used in relating tension and hydraulic conductivity to water content in unsaturated soils. These curves may prove useful for catchment classification and elucidating predominant hydrological processes.

Tundra ponds are a common type of wetland in the High Arctic. Their preservation is predicated upon ample water supply and storage to overcome evaporation losses. Two years of hydrological study of a cluster of ponds in a polar oasis of the Canadian Arctic showed the dominance of overland flow in the spring as an agent that recharged the pond storage. The freshet produced by snowmelt gave rise to extensive surface flow connections between the ponds and with their surrounding areas, but such flow connectivity lasted only about 2 weeks. After that, the ponds appeared to be separated from lateral drainage. Detailed mapping of the water and frost table positions together with water balance investigation, however, indicated the presence of subsurface flows between some ponds and with their adjacent slope. The flow magnitude was small relative to the vertical processes of evaporation and rainfall. Evaporation loss was mainly responsible for storage depletion, leading to a decline in pond level and shrinkage of open water area, unless major rain events restored the storage (as in 2006). It is postulated that climate warming could increase evaporation and active layer thickness to promote greater loss in surface water storage, or geomorphic processes could breach the pond rims, leading to the demise of ponds.

Wetlands are important to boreal catchment hydrology and water chemistry regimes because they are often situated at the outlet of headwater basins. There is understanding of runoff and geochemical processes that predominate in these wetlands. However, an investigation to improve understanding of the dynamic of hydrological function is absent. This paper addresses the nature of the collection, storage, transmitting and contributing functions of one typical wetland in Canada's Precambrian Shield. The majority of water enters from the larger upstream watershed. Excess water from this source is stored near the bisecting stream, where it interacts little with water collected from other sources. Outflow from the wetland is dominated by surface runoff. There were two hydrological functional phases during the study. During the first phase, the wetland merely transmitted streamflow from higher parts of the watershed. There was a diversity of hydrological function during the second portion of the study. Outflow chemistry during this second phase indicates that even when the wetland was contributing, outflow was composed of water that had very little residence time in the wetland. These results have implications for how hydrological models represent heterogeneous catchment conditions or how they may be coupled to biogeochemical models.

Abstract. Soil moisture and ground thaw state are both indicative of a hillslope's ability to transfer water. In cold regions, in particular, it is widely known that the depth of the active layer and wetness of surface soils are important for runoff generation, but the diversity of interactions between ground thaw and surface soil moisture themselves has not be studied. To fill this knowledge gap, detailed shallow soil moisture and thaw depth surveys were conducted along systematic grids from April to July of 2008 at the Baker Creek Basin, Northwest Territories. Multiple hillslopes were studied to determine how the interactions differed along a spectrum of topological, typological and topographic situations across the landscape. Overall results did not show a simple link between soil moisture and ground thaw as was expected. Instead, correlation was a function of wetness. The drier the site was, the more random the interaction between soil moisture and ground thaw. This indicates that interactive soil moisture and thaw depth behaviour on hillslopes in cold regions changes with location and cannot necessarily be lumped together in hydrological models. To explore further why these differences arise, a companion paper (Part 2: Influences of water and energy fluxes) will examine how the hydrological and energy fluxes influenced the found spatiotemporal patterns.

Abstract. The companion paper demonstrated variable interactions and correlations between shallow soil moisture and ground thaw in soil filled areas along a wetness spectrum in a subarctic Canadian Precambrian Shield landscape. From wetter to drier, these included a wetland, peatland and soil filled valley. Herein, water and energy fluxes were examined for these same subarctic study sites to discern the key controlling processes on the found patterns. Results showed the presence of surface water was the key control in variable soil moisture and frost table interactions among sites. At the peatland and wetland sites, accumulated water in depressions and flow paths maintained soil moisture for a longer duration than at the hummock tops. These wet areas were often locations of deepest thaw depth due to the transfer of latent heat accompanying lateral surface runoff. Although the peatland and wetland sites had large inundation extent, modified Péclet numbers indicated the relative influence of external and internal hydrological and energy processes at each site were different. Continuous inflow from an upstream lake into the wetland site caused advective and conductive thermal energies to be of equal importance to ground thaw. The absence of continuous surface flow at the peatland and valley sites led to dominance of conductive thermal energy over advective energy for ground thaw. The results suggest that the modified Péclet number could be a very useful parameter to differentiate landscape components in modeling frost table heterogeneity. The calculated water and energy fluxes, and the modified Péclet number provide quantitative explanations for the shallow soil moisture-ground thaw patterns by linking them with hydrological processes and hillslope storage capacity.