Hydrology of subarctic Canadian Shield: heterogeneous headwater basins

A field study near Yellowknife, Northwest Territories, was conducted to understand and conceptualize better the runoff generation processes of Canadian Shield headwater basins. Results indicate that these basins can be viewed as a number of hydrological elements, defined as physiographic units, with behaviours, defined by the pattern of their functions over time, which are similar within their boundaries and dissimilar with areas adjacent. A key finding of this study is that available storage at any location is dictated by hydrological processes within the individual elements as well as inputs from adjacent elements. Runoff from an element is generated only when its saturation threshold is exceeded. The importance of inputs from adjacent elements in addressing storage demands causes their geometry and topology on the landscape to control where, when and how runoff is generated. The physical manifestation of these processes is a cascading runoff pattern through the headwater basins as their downstream locations saturate and generate runoff. The element threshold concept is proposed as the hydrological framework encompassing these processes and patterns that prevail in the shield environment.