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 typically available precipitation and runoff. 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, but none have been applied widely across the Canadian Prairie. The objective of this study was (1) to determine if the rate at which contributing area changes with loss of wetland storage capacity is related to wetland distribution, and if so, (2) to map sensitivity across the region. To do so, a GIS analysis was employed in which iterative measurements were made of contributing area expansion with simulated wetland storage capacity loss. Results show that those catchments with more small wetlands have more sensitive contributing areas to storage capacity loss. 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 loss of wetland storage capacity. This may inform implementation of beneficial management practices, transportation network design, and management of streamflow and nutrient transport to downstream lakes across the region.