ABSTRACT: Hydrologic profiling for greenhouse gases on prairie potholes: Part 1, hydrologic dynamics.

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Abstract

The prairie pothole region is a unique physiographic region that covers 500,000 square kilometres of central North America containing many shallow depressions or "potholes" ranging in size from m2 to km2 that were created by retreating glaciers. Prairie potholes are composed of an ephemeral or permanent pond surrounded by concentric bands of soils with water contents that vary both in space and time. This systematic pattern in soil water content from the edge to the centre of the pothole may be defined as the hydrologic profile of the pothole. Hydrologic profiles of prairie potholes may be important drivers of biogeochemical activity, including transporting precursors of greenhouse gases (GHGs) from contributing source areas towards the ponds and formation of sinks or sources of GHGs. In this project, we are (a) developing a technique for defining hydrologic profiles of potholes; and (b) developing a model that relates hydrologic profiles to GHG exchanges within potholes. For this paper, we present our research findings on predicting hydrologic profiles of potholes. We studied potholes along a P-PET gradient at 5 nodes extending from the semi-arid southern extent (30 yr average annual P-PET=-485 mm) to the semi-humid northern extent (-65 mm) of the prairie pothole region in central Saskatchewan. For each node, fine-scale (0.5 m x 0.5 m) topographic data were obtained using Light Detection and Ranging (LiDAR) technology and landform elements (crest, shoulder, backslope, footslope, toeslope, wetland) were delineated using digital terrain analyses. At each node, about 20 potholes representative of the size distribution of potholes were selected and 4 to 8 orthogonal transects were established from the crest to the centre of each pothole. Soil moisture was measured at 10 m intervals along each transect on a 24 day cycle from May to October 2005. We present our research findings on the interactive impacts of landform elements with changing climatic conditions on the hydrologic profiles of potholes. Future research will use hydro-GHG profiling to scale estimate of GHG sink/source status from individual potholes to the entire region.

Bibliography of Canadian Geomorphology