Hydrological thresholds in depression storage and contributing area for low-relief landscapes

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This research is an extension of my earlier work in digital terrain analysis and aims to improve our understanding and ability to model the impact of surface depressions on streamflow. One of the distinctive features of the low-relief landscapes of Canada west of the Rocky Mountains is the wide-spread occurence of shallow, surface depressions produced by glacial and periglacial processes. In the Canadian Prairies, these depressions are often called Prairie potholes or sloughs. They provide environmentally-important wetland sites and exert a significant control on streamflow and groundwater regimes. The size and frequency of surface depressions can vary greatly across the landscape. They are often linked by drainage courses along which water flows only when the storage capacity of the depressions is filled. Water spilling from filled depressions represents a hydrological threshold shift with catchment areas and streamflow volumes often changing dramatically. The potential significance of surface depression storage to regional hydrologic and climatic processes is illustrated by the South Saskatchewan River Basin where scientists estimate that over 50% of the landscape rarely contributes runoff to the major river system because of the interuption of drainage courses by sloughs and potholes. The objectives of this research are to (1) characterize the major features of the complex, inter-depressional flow patterns found in much of the Canadian Praires, (2) modify the standard algorithms used in digital terrain analysis to appropriately represent this pattern in local-scale hydrological models and (3) develop up-scaling techniques to allow our improved understanding of this system to be used effectively in regional scale hydrological models. While this research will focus particularly on the hydrological impact of surface depressions in Prairie landscapes, its outcomes will also have application in areas like the Canadian Shield and northern tundra where surface depressions are also an important element of the landscape.