Heat and moisture transfer processes in the aeration zone play an important role in the runoff generation mechanism in regions where seasonal soil freezing/thawing occurs. Seasonally frozen soil can significantly influence the amount of runoff generated during winter and spring. This study presents an analysis of a physically-based parameterization of the frozen ground effects derived from Kozeny’s theory that accounts for changes in both volumetric liquid water and solid particles-water contact surface. An analytical solution is formulated for the Sacramento soil moisture accounting model linked with a basic heat transfer model. Tests at selected sites and river basins show that simulated soil moisture, temperature, and runoff agree well with measured data. Simulation results at river basin outlets suggest that a non-frozen version consistently underestimates spring floods and overestimates the following summer floods if the frozen ground effect is significant. It is impossible to remove these biases without introducing frozen ground physics. Solid particles-water contact surface change is the dominant factor in the runoff mechanism affected by frozen ground; however, its effect decreases significantly for the coarser soils.
Floods, Frozen ground, Precition, Soil temperature and moisture, USA
