Transformation between Phreatic Water and Soil Water during Freeze–Thaw Periods

Abstract

During freeze-thaw periods, the exchange between shallow groundwater and soil water is unusually strong and bidirectional, which causes soil salinization and affects the accuracy of water resources assessment. The objectives of this study were to explore the laws of transformation between phreatic water and soil water through nine different groundwater table depths (GTDs) and three kinds of lithologies during three successive freeze-thaw periods using field lysimeters. The results showed that phreatic evaporation increased with smaller average soil particle sizes. The differences between phreatic evaporation and recharge to groundwater (DPR) and GTDs were well fitted by the semi-logarithmic model, and the regression coefficients A and B of the model were well fitted by the linear relationship with the average soil particle size. With the increase of soil particle size, the change of DPR decreased with the change rate of soil particle size. The extent of transformation between phreatic water and soil water decreased with the increase of soil particle size. During the whole freeze-thaw period, the negative value of DPR increased with an decrease in GTD. The groundwater depths of zero DPR (D-zero) of sandy loam, fine sand and sandy soil during the freeze-thaw periods were 2.79 m, 2.21 m and 2.12 m, respectively. This research is significant for the prevention of soil salinization disasters and the accurate assessment of water resources.

Simulation of Soil Freezing and Thawing for Different Groundwater Table Depths

“…Therefore, the soil temperature dropped more quickly and the freezing rate was faster under the same temperature gradient. Thus, the frost depth was greater when the GTD was 1.0 m. When the GTD was >1.5 m, the transformation from phreatic to soil water was less than with a GTD at 1.0 m (Chen et al, 2018), the soil profile water content was lower, and the thermal conductivity of the soil decreased compared with that at 1.0 m, so the maximum frost depth decreased compared with that at the 1.0‐m depth.…”

“…In shallow groundwater areas, the transformation between phreatic water and soil water is extremely strong during the seasonal freeze–thaw period. Soil freezing will cause shallow groundwater to migrate into the soil profile, resulting in redistribution of soil moisture (Chen et al, 2018; Miao et al, 2017). Thus, the soil hydrothermal properties are changed and then affect the soil freezing and thawing.…”

Effect of Straw Mulch on Soil Evaporation during Freeze–Thaw Periods

“…The average annual potential evaporation of the water surface is 1642.4 mm; the average annual wind speed is 0.9 m•s −1 , and the average annual relative humidity is 74%. The annual average frost-free period is about 200 days, and the maximum observed soil frost depth was 92 cm in 1960 [39,40]. The surface soils are mainly sandy loam, and the soil physical properties are presented in Table 1.…”

The Effect of a Sand Interlayer on Soil Evaporation during the Seasonal Freeze–Thaw Period in the Middle Reaches of the Yellow River

“…They found that soil evaporation in these columns was greatly influenced by the distance between the sand layer and water table. Due to the series of changes in soil physical properties from soil freezing and thawing that make the measurement of evaporation and mechanisms difficult [23,24], there has been less attention placed on sand-layer soil evaporation during the seasonal freeze-thaw period, especially in field experiments.…”