An integrated framework of lake‐stream connectivity for a semi‐arid, subarctic environment

Abstract Lake‐stream networks dominate the semi‐arid, subarctic Precambrian shield. Such a network consists of a number of lake basin elements linked to each other by surface channels. To investigate the processes causing seasonal severance of flow connection in the lake‐stream system, a chain of lakes in northern Canada was studied in 2004. Water balance shows that rapid and substantial runoff from the local basin slopes during the snowmelt period led to a rise of lake levels above their outlet elevations to generate outflow. Continued summer evaporation caused draw down of lake storage below the outflow thresholds, represented by the lake outlet elevations. Outflow ceased and the lakes became disconnected. Summer rainfall in a semi‐arid environment was insufficient to overcome storage deficit to re‐establish flow connectivity among all lakes. For the drainage system as a whole, streamflow interruption or continuity depends on the linkage of its lake‐stream sub‐units. The principle of fill and spill governs runoff generation and flow connection between the lake elements. This principle is applied to a conceptual model of flow along a chain of lakes, taking account of (1) antecedent storage in individual lakes, (2) their storage change calculated through water balance and (3) the thresholds to be exceeded for outflows to occur. Copyright © 2007 John Wiley & Sons, Ltd.