Published March 14, 2019 Original Research Core Ideas Simulation of Soil Freezing and Thawing • The SHAW model was used to simu- for Different Groundwater Table Depths late the freeze–thaw process during freeze–thaw periods. Junfeng Chen,* Xuguang Gao, Xiuqing Zheng, • It revealed the effects of soil texture Chunyan Miao, Yongbo Zhang, Qi Du, and Yongxin Xu and groundwater table depth on soil freezing and thawing. During freeze–thaw periods, the transformation between phreatic water and • The frost depth and accumulated soil water will change the soil hydrothermal properties and affect the soil freez- negative soil surface temperature ing and thawing in shallow groundwater areas. The purpose of this study was to relationship was determined. determine the effect of four different groundwater table depths (GTDs) and two soil textures on the process of soil freezing and thawing during two successive freeze–thaw periods using the Simultaneous Heat and Water (SHAW) model. The results show that the frost depth was the maximum when the GTD was 1.0 m, and the maximum frost depths of sandy loam and fine sand were 97.6 and 98.9 cm, respectively. When the GTD was larger than 1.5 m, the maximum frost depth decreased with an increase in GTD, and the maximum frost depth of the soil pro- file was more sensitive to changes in the air temperature. The frost depth of the soil profile was linear with the square root of the accumulated negative soil sur- face temperature (ANST) under different GTDs. The ANST was influenced by the phreatic evaporation, and the soil freezing rate increased with an increase in GTD under the same ANST. This research is significant for the rational development of soil water and heat resources and the study of soil water–heat transfer in shallow groundwater areas. Abbreviations: ANST, accumulated negative soil surface temperature; GTD, groundwater table depth; SHAW, Simultaneous Heat and Water. Soil freezing and thawing is a common natural phenomenon in seasonally frozen and permafrost areas. China has the third largest area of frozen soil in the world, and the soils are affected by seasonal freezing and thawing in northern China. In shallow ground- J. Chen, X. Gao, X. Zheng, C. Miao, and Y. water areas, the transformation between phreatic water and soil water is extremely strong Zhang, College of Water Resources and Engi- during the seasonal freeze–thaw period. Soil freezing will cause shallow groundwater to neering, Taiyuan Univ. of Technology, Taiyuan 030024, China; C. Miao, First Hydrogeology migrate into the soil profile, resulting in redistribution of soil moisture (Chen et al., 2018; and Engineering Geology Team of Shanxi Miao et al., 2017). Thus, the soil hydrothermal properties are changed and then affect Province, Taiyuan 030024, China; Q. Du, Taigu Water Balance Experimental Field, Bureau of the soil freezing and thawing. Not only does freeze–thaw action change the physical and Hydrology and Water Resources Survey of chemical properties of soil (Dagesse, 2010; Özgan et al., 2015; Sheng et al., 2015), but it Shanxi Province, Taigu 030800, China; Y. Xu, also affects the soil erosion resistance and has a significant impact on the water and heat Dep. of Earth Sciences, Univ. of the Western Cape, Private Bag X17, Bellville, Cape Town balance in the soil (Guo et al., 2011a; Zhao et al., 2013). Therefore, study of the freezing 7535, South Africa. *Corresponding author and thawing process in soil is important for the rational development of soil water and ([email protected]). heat resources, agricultural production, and project construction. The freeze–thaw cycle of soil is the result of complex effects of meteorological and Received 20 Aug. 2018. environmental conditions on the heat flux of surface water. For many years, investigators Accepted 7 Jan. 2019. have conducted a great deal of research on the effects of snow cover (Iwata et al., 2010; Ling and Zhang, 2003; Osokin et al., 2000; Qiang et al., 2018; Zhang, 2005; Zhou et al., 2013), Citation: Chen, J., X. Gao, X. Zheng, C. Miao, Y. Zhang, Q. Du, and Y. Xu. 2019. Simulation meteorological factors (Frauenfeld and Zhang, 2011; Guo and Wang, 2014; Hirota et al., of soil freezing and thawing for different 2006; Jafarov et al., 2013; Wang et al., 2015, 2016), topography (Ling et al., 2012; Gao et groundwater table depths. Vadose Zone J. 18:180157. doi:10.2136/vzj2018.08.0157 al., 2016; Lin et al., 2010; Yi et al., 2014), and pore size (De Kock et al., 2015; Starkloff et al., 2017; Watanabe and Kugisaki, 2017) on the soil freezing and thawing process during the seasonal freeze–thaw period. The soil freezing and thawing process has been studied by monitoring methods (Kimball et al., 2004; Kong et al., 2014; Naeimi et al., 2012; Sun © 2019 The Author(s). This is an open access article distributed under the CC BY-NC-ND license et al., 2012; Wu et al., 2016b) and numerical models (Gens et al., 2009; Kojima et al., (http://creativecommons.org/licenses/by-nc- nd/4.0/). 2013; Mironov and Karavaysky, 2015; Semenova et al., 2014). Rasmussen et al. (2018) Vadose Zone Journal | Advancing Critical Zone Science calibrated CoupModel to simulate permafrost temperature at two necessary to strengthen the research on the influence of ground- sites with different snow depths on the delta in the Zackenberg water on the process of soil freezing and thawing. Valley, northeastern Greenland. Younes et al. (2015) simulated The freeze–thaw cycle in the soil is a complex process accom- wintertime soil temperature, soil frost depth, and snow depth for panied by heat conduction, phase change of water, solute migration, a 14-yr period in a highland area of Iran using CoupModel. To pre- and other physical, chemical, and mechanical effects. Thus, various dict water migration in freezing soil, Ming et al. (2016) presented models have been used to simulate and monitor the soil freezing a water migration model that introduced the concept of a migra- and thawing process in many studies. Flerchinger and Saxton tion potential. Kelleners (2013) developed a new numerical model (1989) and Flerchinger (1991) established a coupled model of to calculate coupled water flow and heat transport in seasonally water and heat transfer in frozen soil based on the principle of frozen soil and snow. The freezing and thawing status of the soil conservation of mass and energy, the SHAW (Simultaneous Heat as well as the freezing and thawing process mainly depends on and Water) model, which is a systematically effective model for the soil temperature and the soil water content. Ding et al. (2000) simulating soil freezing and thawing. The SHAW model has been established the relationship between freeze–thaw depth and soil verified to accurately simulate the soil freezing depth, the effect of temperature in soil freeze–thaw cycles based on experimental water and solution on winter freezing, and the effect of solutes on data from the Tibetan Plateau region and found that the maxi- soil freezing (Chen et al., 2015; Corrao et al., 2017; Fu et al., 2016; mum freeze–thaw depth and freeze–thaw time for different frost Gosselin et al., 2016; Li et al., 2012, 2013; Liu and Shao, 2015). depths is determined by the surface soil temperature. Frauenfeld Guo et al. (2011a, 2011b) simulated the surface flux of the Naqu et al. (2004) used observational data of soil temperatures at 211 BJ station using the SHAW model and found that the daily freez- sites to assess the characteristics of soil depth changes in Russia ing–thawing process in shallow soils affected the surface energy from 1956 to 1990. flux, and this effect was greater during the freezing process than The freezing and thawing of soil is essentially the freez- the thawing process. Kojima et al. (2013) proposed a sensible heat ing and thawing of water in the soil medium, that is, the phase balance method to determine the soil freeze–thaw rate by using the change process of the pore water. The difference in soil water SHAW model to simulate the soil freezing and thawing process. content will directly affect the degree and intensity of soil freez- Throughout the current research, significant progress has been ing. Kozlowski and Nartowska (2013) simulated the variation in made in the monitoring methods and numerical simulations of the the unfrozen water content in representative bentonites during soil freezing–thawing process during the freeze–thaw period, and freeze–thaw cycles. By studying the freezing and thawing charac- the SHAW model has been mainly used to simulate heat, water, teristics of three kinds of soils. Tian et al. (2014) found that the and solute transfer within a one-dimensional profile that includes change in unfrozen water content in soil lags behind the change the effects of plant cover and snow. An inadequate understanding in soil temperature. of the effects of GTD on the soil freezing and thawing process As a source of soil water, the groundwater has an important during seasonal freeze–thaw period promoted this study. influence on soil water variations and soil evaporation, especially The objectives of this study were to: (i) use the SHAW model in shallow groundwater areas. Frequent fluctuations of ground- to simulate the freezing and thawing process of soils during two water would aggravate soil salinization in arid and semiarid areas successive freeze–thaw periods; (ii) investigate the characteristics where soil evaporation is strong (Ibrahimi et al., 2014). Wu et al. of soil freezing and thawing under four different GTDs (0.5, 1.0, (2016a) studied the evaporation of frozen and thawed soil under 1.5, and 2.0 m) and two different soil textures (sandy loam and fine different GTDs by field soil column experiments and revealed sand) during two successive freeze–thaw periods; and (iii) reveal the influence of GTD on water and salt transport in frozen and the effects of soil texture and GTD on the soil freezing and thaw- thawed soil.