ABSTRACT: The storage dynamics of a subarctic Canadian Shield catchment.

CGRG Bibliography of Canadian Geomorphology
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Abstract

Several previous studies have identified the importance of exceeding storage thresholds for generating runoff from components of the Canadian Shield landscape. A water budget study was initiated in the 150 square kilometer Baker Creek research catchment in the subarctic Canadian Shield to evaluate the significance of storage, its dynamic and potential influence on runoff generation at a catchment scale. Water budget measurements taken from April – September 2007 included precipitation, snowmelt, terrestrial evapotranspiration, lake evaporation, streamflow, lake detention storage and soil water storage. Most of the snowmelt is directed to storage early in the study period, with much of the remainder directed to streamflow. Contrary to expectations, the largest storage receptacle was not the lakes, but the soils. Losses to the atmosphere from storage dominated the fluxes from the catchment by the end of June. A geophysically based investigative framework shows that streamflow at the catchment outlet displays a hysteretic relationship with storage. The efficiency with which storage is converted to streamflow during individual runoff events increased non-linearly with the ratio of precipitation inputs to a weighted basin scale storage deficit. The non linear pattern can be explained by differences in the locations and nature of the areas hydrologically connected to the outlet among events. When the catchment is dry, only a series of large lakes contribute to runoff to the basin outlet. When the catchment is wet, much more of the watershed can direct water to the outlet, and the basin becomes more efficient in generating runoff. Furthermore, low water levels associated with dry conditions reduce the efficiency with which water can be transferred downstream by the lakes. The results imply that the probability distribution of distance to the outlet from locations where storage thresholds have been exceeded may be useful in discerning the runoff ratio in heterogeneous catchments.

Bibliography of Canadian Geomorphology