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In cold regions, frozen soil has a significant influence on runoff and water erosion. Frozen soil can reduce infiltration capacity, and the freeze-thaw processes degrade soil cohesive strength and increase soil erodibility. In the Inland Pacific Northwest of the USA, major erosion events typically occur during winter from low-intensity rain, snowmelt, or both as frozen soil thaws and exhibits low cohesion. The Water Erosion Prediction Project (WEPP) model is a physically-based simulation tool for water erosion, and has been widely used for conservation planning on agricultural, range, and forest lands. WEPP estimates runoff and sediment yield by simulating major hydrological and erosion processes. Previous applications of WEPP to continuous bare fallow (CBF) runoff plots at the Palouse Conservation Field Station (PCFS) in southeastern Washington State showed that WEPP reproduced the occurrence of the major observed erosion events but the amount of sediment yield was either under- or over-estimated. The inability of WEPP to fully reproduce field-observed erosion events at the PCFS suggests a need for an examination of the dynamic changes in soil properties and for improving the representation of such dynamics. The objective of this study was to evaluate the seasonal changes of rill erosion parameters on a CBF runoff plot at the PCFS.