SPATIAL AND TEMPORAL CONTROLS ON STREAMFLOW GENERATION IN A HIGH ARCTIC CATCHMENT: HOW DOES WATER ACCUMULATE ALONG THE VALLEY FLOOR?

Spatial and temporal patterns of runoff generation are poorly understood in watersheds throughout the world, though this is particularly true in Arctic watersheds underlain by permafrost. In these regions of the world, the presence of permafrost, along with rapidly changing climatic conditions, has posed a challenge to understanding stream-aquifer dynamics. Previous work on runoff generation in high Arctic catchments has been conducted at small spatial scales (single hillslope studies) and relatively large spatial scales (hydrograph analysis at the catchment outlet). The disparity in spatial scales makes it difficult to determine how sources of streamflow are distributed across the broader watershed.

The purpose of this study is to understand runoff generation dynamics in catchments underlain by continuous permafrost by working between the greater catchment scale and smaller hillslope scale. We conducted four different sampling events, where discharge was quickly sampled along the valley bottom, providing a temporal “snapshot” of the spatial distribution of discharge. The four sampling events consider both shallow and deep frost table conditions, as well as low (15 L/s) and high (286 L/s) discharge conditions. Results show that the spatial pattern of discharge accumulation along the valley floor changes as a function of watershed wetness and frost table thaw extent. Specifically, the spatial accumulation of discharge more closely follows the spatial accumulation of upslope-accumulated area under wetter watershed conditions and drier conditions during times of shallower thaw depth. However, this relationship breaks down during drier conditions at times of deeper thaw depth, suggesting that surface topography is not always a good predictor of streamflow generation in this catchment. Also, similar to temperate snowmelt-dominated catchments, the slope of the discharge-contributing area relationship became greater with increasing watershed wetness. This work elucidates fundamental runoff generation processes and provides insight into hydrologic dynamics in arctic systems that are currently experiencing rapid environmental change.