Sediment Export Modeling in Cold-Climate Prairie Watersheds

Abstract

Nonpoint source pollution is a critical problem in Canadian prairie watersheds. However, sediment mobilization and export are poorly represented in existing models for these watersheds. The poor representation is partly because the hydrology of the region is highly influenced by the existence of numerous dynamically-connected landscape depressions that vary in storage capacity and because of the complex freeze-thaw cycles in the region. The objective of this research was to improve sediment export simulation modeling in these cold-climate prairie watersheds by incorporating a probability distribution function of depression storage capacity and a seasonally varying soil erodibility factor into the soil and water assessment tool (SWAT) model. The probability distribution function is used to represent the variation in storage capacity of the numerous depressions, whereas the seasonally varied soil erodibility factor is used to account for changes in erodibility as the soil freezes and thaws. Results from two case study watersheds confirm an improvement in sediment export predictions when varying storage capacity is represented and the sediment loss routine includes seasonally varying soil erodibility.