Zero-Flow Dynamics for Headwater Streams in a Humid Forested Landscape

Much of our understanding on temporary headwater streams is from arid and sub-humid environments. We know less about zero-flow periods in humid headwater catchments that experience seasonal snow cover. Our study characterised the temporal and spatial patterns of zero-flow periods for forested headwater streams in a snow-dominated landscape. We used 36 years of streamflow data from 13 headwater catchments within the Turkey Lakes Watershed located on the Canadian Shield in Ontario, Canada, near the eastern shores of Lake Superior. These headwater catchments differ substantially in their number of May-November zero-flow days (0-166 days per year) despite being clustered in a small geographical area with similar geology, physiography and vegetation cover. The catchments also experience similar continental climatic conditions with relatively even precipitation inputs throughout the year (mean annual precipitation of 1210 mm/year). Inter-annual variability in the number of zero-flow days was primarily associated with May-November precipitation and evapotranspiration. Despite the large seasonal snowpacks that form in this region, the amount of snow did not appear to influence the extent of zero-flow periods. We found that between-catchment variability in zero-flow occurrences was related to differences in catchment area and catchment properties typically associated with greater groundwater influence. Our study suggests that occurrences of zero-flows in headwater streams can be highly variable even over small geographical regions and that flow permanence may be more sensitive to spring to fall weather conditions than the influence of snow due partly to the shallow soils typically found on the Canadian Shield.