Towards a dynamic effective drainage area map for the Canadian Prairie : sensitivity of contributing area to wetland storage capacity

Abstract

Wetlands that occupy topographic depressions are a defining feature of the Canadian Prairie. These features control hydrological connectivity as they contain high storage capacity relative to precipitation and runoff than is typically available. Altering wetland distribution changes the frequency with which areas can become hydrologically connected to the catchment outlet. There are several methods that have proven successful in estimating contributing area response to changes in wetland storage satisfaction or removal, but none have been applied widely across the Canadian Prairie. The objective of this study was to determine if the rate at which contributing area changes with wetland storage capacity satisfaction or removal could be related to wetland distribution, and if so, map sensitivity across the region. To do so, a GIS desktop analysis was employed in which iterative measurements were made of contributing area expansion with simulated wetland storage capacity satisfaction or removal. Results show that those catchments with more small wetlands have more sensitive contributing areas to storage capacity satisfaction or removal. Extrapolation of this relationship across the Canadian Prairie shows that areas in western Manitoba and southeastern Saskatchewan are among the most sensitive. These results provide a better understanding of how contributing area may change with satisfaction of wetland storage deficits or removal of wetland storage capacity and this may benefit agriculture, industry, and efforts to manage floods and nutrient transport to downstream lakes across the region.