Simulation of freezing and thawing soils in Inner Mongolia Hetao Irrigation District, China

Inner Mongolia Hetao Irrigation District, in north of China, is typical of seasonal frozen soil areas in the region. Irrigation in autumn is required to leach soil salt and to provide a reserve of soil water for the next yearʹs crop. However, improper autumn irrigation results in the secondary salinization of soil. The objective of this study is to simulate soil water and heat dynamics during winter period with the one-dimensional Simultaneous Heat and Water (SHAW) model to assess its capability for simulating overwinter water storage. SHAW model soil parameters were calibrated by data of 1995–1996 and 2002–2004 and validated by data of 1996–2001 and 2005–2006 using field measured soil water contents and temperatures during freezing and thawing periods. Using calibrated and validated soil parameters, the paper simulates the process of soil freezing–thawing, and the dynamic variation of moisture–heat transfer, including soil water content, temperature, frost depth, soil evaporation, and water flux in the seasonal freezing–thawing period. These are useful to determine proper autumn irrigation management, and can be used in future research to address overwinter solute migration to reduce soil secondary salinization.