Modeling Soil Freezing and Thawing on a Rangeland Watershed

Abstract

ABSTRACT Soil frost can significantly reduce the infiltration capacity of soil, which may result in severe flooding and erosion. Snow cover, precipitation, and frozen soil vary with elevation particularly in mountainous rangelands, and consequently only portions of a watershed typically contribute to runoff. The objective of this research was to extend the applicability of the Simultaneous Heat and Water (SHAW) model to frozen soil prediction on rangeland. The SHAW model simulates heat, water, and solute transfer through a one-dimensional snow-residue-soil system using hourly weather observations. Simulations were conducted for a low, middle, and high elevation site on the Reynolds Creek Experimental Watershed in southwestern Idaho. Simulated frost depths, snow depths, and soil temperatures compared well with measured values at the three sites. For the first year, soil frost was deepest (72 cm measured; 75 cm simulated) at the lower elevation site where snow cover was minimal. The model correctly predicted little or no frost penetration at the upper elevation sites for the same year. Maximum simulated frost depths for the second year were 58 cm, 43 cm, and 31 cm at the low, middle, and high elevation site compared to measured values of 58 cm, 50 cm, and 34 cm, respectively. These results support the use of the SHAW model for simulating soil frost on rangelands.